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GEO 2010
- Conference date: 07 Mar 2010 - 10 Mar 2010
- Location: Manama, Bahrain
- Published: 07 March 2010
401 - 457 of 457 results
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A Consistent Geostatistical Approach for Constraining Multiple Surfaces to Horizontal Wells
Authors Petter Abrahamsen, Pål Dahle, Frode Georgsen and Arne SkorstadThe robust use of horizontal well data in 3D stratigraphic horizon modeling is an important challenge.
In many reservoir models there are inconsistencies between the zone log information observed in
horizontal wells, and the horizons and zones of the 3D model.
The two main reasons for these inconsistencies are that:
1) Zone log information is not used directly in the modeling of the surfaces;
2) Well picks in deviated wells do not impact the modeling of adjacent surfaces.
Inconsistencies between the 3D model and the horizontal well data are typically resolved by time
consuming, iterative manual editing of the stratigraphic horizons.
A robust, geostatistical approach for ensuring the correct modelling of multiple stacked stratigraphic
surfaces constrained by long horizontal wells is presented. The approach has been developed to
maintain 3D consistency between the stratigraphic surfaces and horizontal well data. The stratigraphic
surfaces are treated simultaneously in 3D and universal or Bayesian cokriging is used for prediction of
surface location based on a variety of constraints including: well picks; zone logs; isochores and
seismic interval velocities.
In contrast to standard approaches, all well markers (picks) are treated simultaneously and will have
impact on surfaces above and below. This ensures consistent use of all available well marker data forall surfaces.
Zone log constraints in long horizontal wells are handled by identifying the sections of the well paths
that impose soft (inequality) constraints on the surfaces. The key sections of the horizontal wells are re
-sampled at approximate grid resolution and used as help points in the kriging equations. Identifying
the soft constrains and assigning correct value to the help points is the cornerstone of the method.
Velocity and isochore trends are used to ensure that overall shape of the structure and thickness
variations are preserved. Uncertainty trends for velocities and isochores are used to allow flexibility in
the relative weights assigned to the various input constraints.
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Hydrothermal Dolomites along Faults/Fractures in the Aptian-Albian Platform Carbonates (Karrantza Valley, N.W Spain): Petrographic and Geochemical Results
Authors Mumtaz M. Shah, Fadi H. Nader, Julie Dewit, Rudy Swennen and Daniel GarciaAptian-Albian carbonates were deposited in the Basque-Cantabrian Basin (NW Spain) as a result of an
intense rift-related subsidence. This rock succession is affected by N-S, E-W, NW-SE and NE-SW
oriented normal and strike-slip faults, which acted as fluid flow conduits to selectively dolomitize the
Aptian-Albian carbonates in the study area (Karrantza valley, NW Spain).
Field studies exhibit excellent beige coloured dolomite exposures along the faults surrounded by light
grey coloured host limestone. Linear fault restricted dolomite and irregular dolomite bodies, indicate
that lithology mechanically controls the geometry of the dolomites.
Different dolomite facies exhibit systematic variation away from the fault/fracture. Paragenesis of these
dolomites indicate their development over different dolomitising events. Several phases of calcite
cement pre- and post-date the dolomitisation events. Pyrite (2-phases), galena and sphalerite are also
locally observed. Zebra dolomite shows the most depleted values with δ18O varying between -18.6 to
-15.2 ‰V-PDB and δ13C between -0.7 to +1.6‰ V-PDB compared to non-planar and planar dolomite
which show overlapping stable isotopic ratios ranging from -18.7 to -11.5‰ δ18O V-PDB and -2.6 to
+1.9‰ δ13C V-PDB. The broad range and highly depleted values of δ18O are interpreted to reflect
multiphase dolomitization and dolomite recrystallization. Limestones close to the dolomites show
depleted δ18O values (similar to those of the dolomites), implying isotopic resetting during
dolomitization and large scale fluid migration. Microprobe analysis indicate Fe-rich central part of
dolomite (1.6 to 1.9 wt.%) as compared to their external zones and the dolomite cement (Fe: 0.0 to
0.6 wt.%). The Mg content in the void-filling, non-luminescent calcite is high (0.9 to 1.3 wt.%) as
compared to luminescent, replacive calcite (0.1 to 0.8 wt.%). Fluid inclusion analyses show Th values
range from 120 to 200°C and estimated salinities between 10 and 24 eq. wt. % NaCl for zebra and
nonplanar dolomites, which confirms very hot dolomitizing fluids (hydrothermal origin)of the investigated dolomites.
Above stated studies helped in defining the geometry of dolomite bodies (reservoir heterogenity
characterization), constraining the genesis of the dolomites and superposition of diagenetic events,
documenting the characteristics of hot, saline dolomitizing fluids and related fluid flow history.
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Influence of Noise from Passive Seismic Reservoir Detection
Authors Weiwei Yang, Nima Riahi and Mike KellyWe present a numerical modeling study of the impact of surface noise on the ability to correctly detect
low-frequency micro-tremors originating from the subsurface. The analysis is motivated by the need to
assess the extent by which the empirically observed hydrocarbon (HC) micro-tremor can be masked by surface noise.
Subsurface micro-tremors and surface noise sources (hereon referred to as signal and noise) are
placed within a p-wave velocity model of a producing field. Placement of the virtual signal and noise
sources is based on known reservoir and noise locations. Signals are modeled by vertically polarized
Ricker wavelets with 3Hz center frequency randomly distributed in time. Noises are modeled by either
vertically or horizontally polarized white noise filtered between 1-18Hz. The sources are propagated
using a staggered grid finite difference solver, and the particle velocities are recorded at ground level
by virtual receivers. A series of forward simulations is run with different noise strengths to achieve
various signal-to-noise ratios (SNRs). Placement and signature of the signal and noise sources are kept constant.
A spectral ratio attribute known to be indicative of hydrocarbons is computed for the synthetic results.
From this attribute, the virtual receivers are classified into two groups, above HC and away from HC,
using two classification methods: Jenks' natural breaks and neural networks (NNs). The classification
results from the two methods are consistent. The best performing NNs, trained on synthetic data for
each noise level, are then used to generate hydrocarbon probability maps based on real passive
seismic data acquired on the same producing field. These maps are compared with the actual oil-water
contact (OWC). Results show that the predictions were most reliable for NNs trained on a SNR of 0.5
(or -3 dB). Predictions from NNs trained on higher or lower SNRs give inferior predictions for this
dataset. A summary of the influence of noise on the ability to predict reservoir presence is provided.
This study shows that even though noise impairs the ability to correctly identify hydrocarbon related
tremors, more reliable results can be achieved by applying processing methods that accommodate for variations from noise.
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Wave-Equation Propagation as a Body-Wave Filter
Authors Benjamin Witten and Brad ArtmanPassive seismic data collected with broadband seismometers is usually under-sampled. The sampling
problem makes it impossible to utilize multi-dimensional filtering techniques to isolate various
propagation modes. We propose a chain of wave-equation imaging and simple signal processing in the
image domain as an effective method to mitigate deleterious noise effects and improve the ability to
extract body waves containing subsurface information.
We begin with the principles of time-reverse modeling: data are reversed in time and inserted into the
model domain as source functions. In this domain, data are better sampled, and after sufficient
propagation steps wave-front healing will allow events within the data to coalesce into approximately
correct coherent wave fronts. At each time-step in the elastic propagation, the wave field can be
filtered to remove unwanted energy. Also, the propagation itself will confine high ray parameter,
undesirable, energy to the shallow section of the model domain due to evanescence in a v(z) medium.
We also capitalize on being able to exactly separate the P- and S-wave components using simple
vector operators. To accumulate a measure of body-wave energy content as a function of surface
coordinate, we sum the depth axis of the image after windowing away the contaminated shallow section.
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An Integrated Approach to Salt Basin Evaluation
Authors Peter A. Kukla and Janos L. UraiSalt basins play a major role in the hydrocarbon industry but also are increasingly important as oil and
gas storage sites. They display a complex geodynamic evolution characterized by several phases of
halokinesis and associated sedimentation. Our approach to salt basins combines seismic, structural and
sedimentary studies with analysis of rheological properties, and geomechanic modelling. High
resolution reservoir quality studies in prospective salt basin sequences and new advances in microscale
porosity and permeability analytical techniques can now be taken to a predictive level for
exploration and serve to optimize production in existing fields. We illustrate these concepts with case
studies from Europe and the Middle East.
One classic area of salt tectonics is the Central European Basin System (CEBS). Here, the mobile
Permian Zechstein salt formed a large number of salt structures such as anticlines, diapirs, pillows,
sheets, stocks, and walls during an extended period of salt tectonic activity in Mesozoic and Cenozoic
times. Salt-influenced sedimentary responses to renewed phases of tectonism can be clearly discerned
from detailed sequence analysis based on seismic and log data combined with retrodeformation
modelling studies. High quality 3-D seismic data integrated with structural modelling improves the
definition of salt structure and associated sediment architecture in salt-controlled sequences.
The improved understanding of the tectonic and sedimentary evolution of salt structures and detailed
knowledge of the dynamics of subsurface salt has significant effects on seismic modelling, depth
conversion and interpretation of complex structures. Integrated analysis advances the prediction of
potential hydrocarbon reservoirs. Salt wedges which have formed by lateral extrusions during periods
of diapir emergence and reduced sediment accumulation as well as isolated carbonate “rafts” and
“stringers” can form potential hydrocarbon traps and thus represent an alternative exploration target in
most salt-rich hydrocarbon provinces. Knowledge of the geometry and properties of salt as well as the
surrounding host rocks significantly improves the prediction of seals and their capacity and helps in
planning drilling operations.
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Sedimentology and Exploration Potential of the Haima Supergroup from the Eastern Flank of the Ghaba Salt Basin in Central Oman
Authors John D. Smewing, Jan Vargo, Hugh Miller, Ed Price, Cliff K. Hunter and Mohamed AminIn Central Oman the Early Palaeozoic Haima Supergroup contains important clastic reservoirs charged
by hydrocarbons from the underlying Huqf Supergroup. CCED (Oman) and partner, Tethys Oil, are
exploring on the eastern flank of the Ghaba Salt Basin. The Amin, Miqrat, Al Bashair and Barik
Formations in the lower part of the Haima Supergroup form part of their exploration portfolio.
Recent heavy oil discoveries have been made in the Amin and Miqrat clastics as well as newly
discovered light oil in the underlying Huqf carbonates.
We report on new data on the Amin to Barik Formations which have emerged as a result of the recent
drilling and on a linked outcrop-based program in the nearby Huqf inlier.
The Huqf inlier is a 10,000 km2 area of outcropping Cretaceous to Neoproterozoic sediments. Here, the
Amin Formation at the base of the Haima comprises coarse lithic sandstones and chert conglomerates
that were deposited as in channel bars on a west facing continental braid plain. A marine flooding
surface in the upper part of the Amin Formation terminates continental sedimentation. Thereafter all
Haima sediments were deposited in marginal marine to fully marine settings.
Contrary to previous suggestions no evidence for primary aeolian sand deposition has been found.
Instead marine incursion during upper Amin times resulted in flooding of the continental braid plain
and a shore-fringing mixed clastic-carbonate tidal flat developed upon which the fine clastics of the
Miqrat Formation were deposited. The tidal flat interpretation is based on the occurrence of
channelling, convolute bedding and starved wave ripples, on the overall fine grained nature of the
sediment and on the ubiquitous presence of dewatering structures and carbonate mud.
Highly porous large scale cross bedded sandstones occur within the Miqrat Formation in the outcrop
belt. Based on the evidence for marine deposition these sandstones are believed to represent subtidal
straight crested dunes.
Marine influence increases upwards into the Al Bashair Formation with oolitic limestones interbedded
with the fine clastics. The Barik Formation represents progradation of deltaic sands out over this marine basin.
These revisions to the stratigraphy and palaeoenvironmental interpretations of the Haima Supergroup
have provided a better framework for east flank exploration in Central Oman and for prediction of the
geometry of potential clastic reservoirs in the target formations.
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Complex Fracture Carbonate Reservoir Modeling for Reserves for Reserves Assurance in West Java, Indonesia
Authors Adi FM Ringoringo, Joko Padmono and Enrico NgantungThe Oldest Carbonate reservoir in west java Indonesia is pre-Tertiary - Oligocene Carbonate. This
potential reservoir is under Talang Akar Reservoir. The other carbonate reservoir in Java are mostly
formed during Miocene. Some formed as reefs carbonate and some other as various clastic carbonate
sediment. Sometimes in the Miocene age, tectonic activity was intensively growth. As a result, the
carbonate reservoir were influenced both by structural and stratigraphic.
Part of west java - Indonesia oil fields consist of some variety of carbonate reservoir. The most
productive reservoir is a build up reef reservoir combined with fracture porosity. Other productive
reservoir followed by clastic carbonate with fracture porosity. The least productive is lagoonal
carbonate reservoir with fracture porosity.
In such condition building a geologic modeling of such carbonate reservoir become complex and
difficult. As a matter of fact, building geologic modeling is depend upon many parameter, such as
geometry of the deposits facies distribution, strucrute configuration and finally reservoir properties correlation.
This paper will describe the work flow to achieve a comprehensive such geology modeling in variety
complex carbonate reservoir, including fracture distribution analysis and to have more precise reserve calculation.
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Systematic Description of Larger Foraminifera from Oligocene -Miocene in Different Oil Field, Kirkuk Area, North Iraq
More LessLarger Foraminifera are typically associated with shallow water carbonate sediments. The investigation
is based on a well exposed and surface sequence of bioclastic limestone in Bai-Hassan Well-25
section. Different types of larger Foraminifera were described , (Miogysina spp. , Miogypsinoides spp.,
Amphistegina spp., Pararotalia spp., Numulittes spp., Heterostegina spp. , Operculina spp.,
Lepiddocyclina spp., etc. indicated of shallow water carbonate sediments.
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Mineralogy and Illite/Smectite Mixed-Layer Expandability of Rudies Formation and Its Relation to Maturation of Organic Matter, in the Southern Sector of the Gulf of Suez, Egypt
Authors Abubakr F. Maky and Ahmed S. MousaThe X-ray diffraction analysis of 29 bulk samples and 21 clay fractions samples derived from Rudies
Formation, that present in Gabal El-Zeit and Morgan basins in the southern part of the Gulf of Suez,
are used to define the mineralogic composition of this formation. This rock unit is composed mainly of
quartz, dolomite and calcite associated with minor amounts of phyllosilicates, such as kaolinite and
illite/smectite mixed-layer, as well as traces of K and Na feldspars, and hematite. The analysis of clay
fraction of the studied samples indicated that, illite/smectite mixed-layer is the main mineral
component in Gabal El-Zeit Basin, followed by kaolinite, in which kaolinite is the main clay mineral,
followed by illite/smectite mixed-layer in El-Morgan basin. Illitization of illite/smectite mixed-layer is
the main process in this study, which indicated that the random interstratification (R=0) of
illite/smectite mixed-layer is present in two stages of organic matter maturation at Gabal El-Zeit Basin
smectite percentage (S%) ranges between 85 and 80%, present in temperature range from 28 to 46 °
C indicating immature stage. whereas random interstratification in Morgan basin are situated in with
smectite percentage ranged between 60 and 50 and temperature range 90 to 91°C, reflects mature source rock.
The ordered interstratification (R=l) has S% ranged between 40 and 25 % present at depth range from
2413 to 3055m and temperature range 94 to 103°C is also detected. While (R=3) illitization stage is
identified with S% ranged between 15 and 10 %, is present at depths 3250 and 3480m and have
temperature range of 115-137 °C which reflecting end of oil generation stage, whereas R≥3 illitization
stage with S% of 10% or less is present at depth ranged from 3445 to 3550m and temperature from
139 to 143°C which indicating wet gas stage. Generally, these illitization stages and temperature
ranges show that, the organic matter content of Rudeis Formation at Gabal El-Zeit Basin is present in
immature stage, whereas the organic matter in Rudeis Formation at Morgan basin is attending in a
range of oil window and wet gas stage.
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Qualitative Core Data Management for Efficient Exploitation and Future Explorations of Hydrocarbon Reservoirs through Corrections in Laboratory Generated Petrophysical Data
More LessThe Petrophysical studies carried out in the Laboratories; generate sets of data on Porosity,
Permeability, Relative and Effective permeability for effective exploitation of the reservoir. These data
are generated by doing experiments on core plugs which were plugged out from different well cores
owing to different reservoir sands. As we know that the cores are cut by the rotating and chipping
actions of the bit, each peripheral particle lying on the peripheral portion of the core experiences a
tremendous frictional force due to the rotational effect of the bit resulting in a tremendous heat
generation along the peripheral part. These phenomena may occur for small time duration but this will
have a definite impact and can change the original orientation of the particles lying in the periphery.
The over all data on porosity, permeability, relative and effective permeability thus generated can have
an erroneous factor through its generation. The error occurs again as a second obliteration when core
plugging job is carried out. The job which is similar to drilling and coring job in a smaller magnitude.
This again resulted in changing the original orientation of the particles lying in the peripheral part of
the core plug. Under tremendous amount of frictional force and temperature of high magnitude these
peripheral particles lose some of their original petrophysical properties as well as orientations. Where
as during the petrophysical studies at the laboratories we never consider these changes made through
the making of plugs and the petrophysical data generated there after is bound to be erroneous with
varying magnitude. So by using a suitable constant during these processes which can be calculated to
the nearest approximation by taking the amount of frictional forces, amount of heat generated and the
mineralogical composition and rock type of the core/ plug involved during the processes. These
corrections will help for better representation of the petrophysical characters leading to efficient
Reservoir exploitation and future exploration activities through better data management.
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Evaluation of the Effect of Wettability Alteration from Oil Recovery in Carbonate Reservoirs
Authors James Sheng, Danielle Morel and Pascal GauerMore than 60% of the world’s oil reserves are held in carbonate reservoirs. Many unfavorable factors
contribute to low oil recovery in these reservoirs. Fractured and oil-wet are two leading factors.
Therefore, many research focuses have been put on these factors. Apparently, there is an increasing
interest in using chemicals to alter wettability. Injection of chemicals can result in various effects, for
example, wettability alteration and reduction in interfacial tension (IFT). The question is how much
contribution from each mechanism to the increase in oil recovery. There is lack of such information in
the literature. The information is very important because it will guide us to select what chemicals to be used.
This paper is to evaluate the effect of wettability alteration on oil recovery in carbonate reservoirs. The
main objective is to quantify different mechanisms of wettability alteration in oil recovery related to
chemical EOR. Particularly, we compare the effects of wettability alteration and interfacial tension. Both
fractured and non-fractured reservoirs are addressed. Analytical models and numerical simulation
models are used. Our results show that wettability alteration only plays important roles when IFT is
high, and it is effective in the early time. IFT plays very important roles with or without wettability
alteration and is effective during the entire process. The implication is that anionics used to reduce IFT
is preferred to cationics used to alter wettability. Other observations are that in surfactant-induced
wettability alteration with low IFT, gravity drive is a very important mechanism. Molecular diffusion of
chemicals affects oil recovery rate in the early time, but not ultimate oil recovery.
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Reservoir Optimization and Monitoring Challenges in the Nhr Umr Reservoirs of the Bahrain Field
Authors Jameela Al Bahraini, Ammar A. Shaban and Ali E.AL-MuftahNhr Umr reservoirs in Bahrain Field consist of three reservoirs that vary from calcareous silt stones to
sand stones. They are the second major producing zones in Bahrain Field and are overlain by Mauddud
limestone reservoir separated by 8 - 10' shale. All these reservoirs are on production since early
thirties and Mauddud reservoir has been under gas injection since 1938. These reservoirs with diverse
fluid contents and hydro-dynamically different systems communicate with each other through the
extensive faulting.
For such mature reservoirs with a long production history, identifying by-passed oil, underperforming
areas, areas under communication, locating infill wells and upgrading the reserves are challenging tasks.
This poster describes the application of a practical process (1) Development of a systematic workflow
for production optimization and reservoir analysis; (2) Identifying and highlighting reservoir trends,
patterns and anomalies; (3) Locating the under performing wells/areas, and recommend solutions (4)
Identifying essential patterns for consideration in overall development plan. The challenge was to
evaluate large data sets in a short time and cost-effective manner.
The technique uses a streamlined workflow of reservoir assessment processes, which require data
gathering, formatting and validation through combining the data with several processes associated
with both the static and the dynamic model of the reservoir. Quick interpretations of these models
generate opportunity regions, re-completion candidates, and new infill potential in the reservoir. Based
on the processes run in the Nhr Umr zones it was possible to understand the reservoir performance
and main issues associated with field development. Utilizing these techniques, the recently completed
development drilling program was suitably adopted to realize an efficient reservoir management
process for developing the field with the objectives of decreasing decline rate and increasing the recovery.
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Gas Detection by Spectral Decomposition Using Matching Pursuit
Authors Ahmed M. Almarzoug and Ferhan AhmedTraditional methods for detecting fluid response are based on the pure elastic Gassman theory which
assumes the resultant seismic effects are frequency-independent. Recently, there have been
investigations into the use of spectral decomposition for extracting information on fluid properties.
Researchers have discussed how to calculate the frequency-dependent seismic reflection response, and
the resultant frequency-related properties, such as attenuation and dispersion characteristics. To
derive frequency-related attributes from seismic data, it is more convenient to use spectral
decomposition techniques. A seismogram can be decomposed into constituent wavelets, and a time
versus frequency analysis can readily be constructed by weighted superposition of wavelet spectra as a
function of record time. The spectral decomposition using Morlet wavelets by matching pursuit requires
no windowing and no use of the Fourier transform. This method has excellent time resolution and
eliminates "Gibbs phenomena" as well as other undesirable effects windowing.
We have developed an accurate Morlet wavelet spectral decomposition using matching pursuit. This
allows us to calculate a range of frequency-dependent attributes, such as, absorption coefficients and
amplitude gradients in the frequency domain. We have observed that the frequency response of a
seismic reflection and its resultant attenuation and dispersion may have a link to fluid saturation. We
have applied the method on real data from Saudi Arabia to demonstrate this correlation. The results
suggest that careful data processing and modeling are necessary to understand the complex effect of
different fluids on the spectral response for reliable interpretation.
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Stratigraphy of the Albian to Santonian Sediments of Bangestan Palaeo-High, Southwest of Iran
Authors Ali Ghabeishavi, Hossein Vaziri-Moghaddam, Azizollzh Taheri and Farid TaatiThe Bangestan Palaeo-high is one of the well exposed Cretaceous palaeo-high which is cropped out in
Bangestan Anticline (southwest of Iran/ about 150 km west of Ahwaz). Eight outcrop sections and one
subsurface section (Pr#35) from Parsi oil field (10 km southwest of Bangestan Anticline) were studied.
More than 2000 thin sections were analyzed. Biostratigraphy, microfacies, sedimentary environment
and sequence stratigraphic techniques were used for better understanding of palaeogeography of
Bangestan Palaeo-high. The foraminifers biostratigraphic study led to recognition of 10 biozones.
The sedimentary environment of the lower Sarvak is interpreted as a carbonate shelf without an
effective barrier separating the platform from the open marine. The inner shelf environment was
dominant by benthic foraminifers such as miliolids, Nezzazata spp. and alveolinids. The rudist
community was well developed in middle shelf environment. The outer shelf was dominant by
oligosteginids and fine-grained platform derived material. The intrashelf basin is identified by
planktonic foraminifers, radiolarians and oligosteginids.
The grainstone dominated upper Sarvak sediments are subdivided into six microfacies belongs to highenergy
fringing carbonate platform around the emerged area. The proximal to distal positions are
identified by varying from intraclast dominated facies to benthic foraminifers dominated, rudist
dominated and finally oligosteginids in more distal one.
The Coniacian-Santonian sediments (Surgah and Ilam Formationes), which were deposited on the
flanks of Bangestan Palaeo-high, are subdivided into nine microfacies types. Various sedimentary
environments, ranging from continental lacustrine to very shallow and relatively deep-water
(hemiplegic to pelagic) marine environments are recognized.
The sequence stratigraphic analyses led to identification of 5 (A-E) sedimentary sequences.
The sequence stratigraphic correlation show that in the Cenomanian time, Bangestan Anticline was
located at margin of intrashelf basin, while in this time Parsi oil field was in the intrashelf basin. At the
Late Cenomanian, the lower Sarvak were differentially uplifted along pre-existing basement faults.
Deposition of the Cenomanian-Turonian limestones (upper Sarvak) and Coniacian-Santonian (Surgah
and Ilam) sediments took place on the flanks of Bangestan Palaeo-high and beyond. The center of this
palaeo-high emerged and was exposed to erosion until Late Campanian.
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Estimation of Barrel of Oil Equivalent of Gas Using PVT Multi-Stage Separation Data
Authors Mohammad AlBahar, Anup Bora and B.B. SinghOver last 60 years, Kuwait’s gas production has been mainly coming from associated gas sources from
its large and thick reservoirs undergoing natural depletion. Recent discoveries of the deep Jurassic gas
discoveries, the relative make-up of overall gas stream has undergone considerable changes. The
current gas stream includes gas production from existing oil reservoirs, deep gas reservoirs,
condensate, and volatile oil reservoirs. As a result of this, gas stream is becoming richer.
However, in the past there has been no systematic attempt to understand and estimate the Barrel of
Oil Equivalent of overall gas based on relative contribution from the reservoirs in Kuwait. This study is
a first attempt to develop a new methodology and process to estimate the BOE factor for Kuwait taking
into account all the major oil/gas producing reservoirs in Kuwait.
The study considered all gas composition information including PVT test data on all PVT samples for
more than 200 wells and gas outlet points. The study focused on the gas composition behavior and the
amount of energy associated with different sources of gas.
The study shows that any oil company must develop and adopt its own BOE factor for reporting the gas
volumes in terms of oil equivalent.
Key technical contributions of this work include: data evaluation techniques, estimation of calorific
values and conversion of the calorific value to BOE factor per (well, reservoir, field and company), and
general correlations of gas and fluid properties for quick projection of BOE value.
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The Use of 3D-3C Seismic Refraction Method to Detect Hidden Shear Zonez
More LessIn the last twenty-five years, there have been significant advances in the spatial resolution of most
geophysical sets of data. Whereas geophysical data were once commonly acquired along widely spaced
profiles, it is now more usual to obtain geophysical data along numerous closely spaced traverses. As a
result, the spatial sampling is now comparable in both horizontal directions and the greater resolution
has greatly improved the interpretation of geological features. A major benefit of high resolution
geophysical data sets, is the ability to generate pseudo-geological maps. The geological map
traditionally has been a one of the most important domains for visually summarizing geological information.
Many geological features in the subsurface are three-dimension (3D) in nature, and two-dimension
(2D) seismic section is a cross section of the 3-D seismic wave field. Having a detailed image of the
subsurface usually makes the interpretation more reliable. The aim of using 3D-3C seismic data is to
find more information about rock properties with both P- and S-waves.
The broad objective of this study was to use seismic refraction methods to map in detail a faults zone
and shear zone, which there was no evidence of subsurface faults in study area. Seismic refraction
methods were selected because of their potential ability to provide greater lateral resolution of the
narrow vertical shear zone, than is currently the norm with electrical or electromagnetic methods. This
situation was confirmed with a number of resistivity depth images as part of this study.
The results of the seismic refraction surveys show that the hidden faults occur as a narrow region with
low seismic velocities and increased depth of weathering. The major geological achievement was the
demonstration that there were cross cutting features associated with the major shear zone.
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Petroleum System Modeling as a Useful Tool for Exploration Stage: A Case Study from Muglad Basin - Sudan
Authors Mohamed A. Yassin and Ahmed GibreelThe Geological & Geophysical (G&G) study’s work scope which is running after structural mapping and
prospects assessment is not enough to be a guide for exploration stage. It can easily be shown that
this kind of scope is often dangerously incomplete without Petroleum system modeling.
Petroleum system modeling technology is used to investigate charge risks by special simulators which
can calculate the processes of hydrocarbons generation, expulsion, migration, accumulation and loss through geologic time.
Structural analysis and sequence stratigraphy are essential part in the basin modeling. Integration of
these two disciplines with others such as geochemistry, petrophysics and geophysics will be very
helpful to reduce the basin modeling’s uncertainties.
This work answering questions such as: Have hydrocarbons been generated in a basin? Where were
the hydrocarbons generated? When were the hydrocarbons generated? Could the generated
hydrocarbons have migrated to my prospect? What are the possible properties of the hydrocarbons
which could have migrated to my prospect?
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Al Rayyan Field: Case Study of a Subtle Structural Trap and Implications for Exploration in the Arabian Gulf
Authors Graeme Warren, Larry Smith and Lex Van WijheThe Al Rayyan Field is an example of a very low relief structure located on the western flank of the
Qatar Arch. The structural analysis of the field is an ideal template for the exploration of subtle traps in
the region. Different seismic data sets and processing techniques (in both time and depth) have
produced ambiguous structures over the field. Isochron mapping of geologically significant intervals
successfully resolves the field’s structural evolution through time. This same mapping strategy can be
employed as an exploration tool to screen and validate subtle prospects observed in both the time
and/or depth domains within the Gulf region.
The Top Early Cretaceous to Top Jurassic isochron is the critical geological interval for understanding
the trap geometry of the field. The field is located on a paleo structural nose that previously plunged
counter to the present-day regional dip direction. The thinning and faulting evident on the Middle to
Upper Cretaceous isochron are in sharp contrast to the structurally featureless Early Cretaceous
isochron. The Jurassic isochron thins eastward towards the Qatar Arch and gives no indication of the
present day field. The isochron characteristics observed locally are consistent with a regional geological
history that begins with stability throughout the Jurassic and Early Cretaceous; is followed by collisional
tectonics during the Middle to Late Cretaceous; and culminates with down-warping and northward
tilting in the Cenozoic. The latter event transformed the Jurassic reservoir at Al Rayyan from a
structural nose into its current low relief, four-way closure geometry.
The foregoing suggests that a valid exploration strategy for the region should consider a search for
subtle structural features that formed during the Middle to Late Cretaceous. Paleo-structural noses
identified within the Cretaceous section, especially those that are associated with isochron thinning and
faulting of the Middle to Late Cretaceous section, represent prime exploration targets. This strategy
should help the explorationist distinguish between structurally valid versus velocity-induced leads
within these target sections.
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Near Surface Effect Corrections with Grm Ssm Method
More LessVariations in the topography and thickness of the near-surface soil layers can have a major affect on
traveltimes, because the very low seismic velocities, often as low as 250 m/s, can result in large
increases in traveltimes. These layers can lead to significant problems with the detailed inversion of
refraction data, commonly as artefacts in the refractor velocities if no attempt is made to recognize
and remove their effects. As such, it is usually necessary to correct for variations in the near surface, if
a detailed model of the refractor is required as a starting models for tomographic inversion.
Very small variations in the parameters used to drive the seismic velocities in the refractor can result
in significant variations in the computed velocities. In many cases, where small receivers spacings are
employed to define very shallow targets, such as is commonly the case with geotechnical
investigations, the variation in the computed time parameters are often as large as the errors in the
traveltime data (Palmer et al, 2005).
Most methods for correcting for near-surface effects attempt to model the near surface irregularities
and to calculate the traveltimes through these irregularities. The corrections are usually computed with
the first arrival refraction data, if there is adequate coverage of these irregularities. The standard
methods of correcting for any near surface variations, using traveltimes obtained with intermediate
shot-to-receiver spacings is described in Dobrin (1983) and Palmer (1980,1986). If these corrections
are not made, the determination of refractor velocities can be subject to considerable ambiguity,
especially where the detailed resolution of narrow features is concerned. However, where the
irregularities do not extend over more than a few receiver intervals, these deterministic methods
cannot be employed, because there is usually insufficient reversed traveltime data to define them
accurately. In such situations, an alternative approach is required (Nikrouz2005).
The near-surface corrections are adjustments to the original field seismic refraction data, in order to
remove the effects of varying topography or surface velocities. With the traveltime data recorded, it
was found that the consistency between adjacent lines, which were only 10 m apart, was not always
immediately obvious, even though the traveltime data generated excellent refraction tomograms.
However, when the near surface effects were satisfactorily accommodated, the consistency between
adjacent lines was improved considerably.
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Advances in Time-Lapse Reservoir Monitoring Using the New Generation of Radar Satellites
Authors Andrea Tamburini, Fabrizio Novali, Stefano Cespa and Giacomo FalorniSurface deformation monitoring provides unique data for observing and measuring the performance of
producing hydrocarbon reservoirs, for Enhanced Oil Recovery (EOR) and for Carbon Dioxide Capture
and Storage (CCS). To this aim, radar interferometry (InSAR) and, in particular, multi-interferogram
Permanent Scatterer (PS) techniques are innovative, valuable and cost-effective tools.
Depending on reservoir characteristics and depth, oil or gas production can induce surface subsidence
or, in the cases of EOR and CCS, ground heave, potentially triggering fault reactivation and in some
cases threatening well integrity.
Mapping the surface effects of fault reactivation, due to either fluid extraction or injection, usually
requires the availability of hundreds of measurement points per square km with millimeter-level
precision, which is time consuming and expensive to obtain using traditional monitoring techniques,
but can be readily obtained with InSAR data. Moreover, more advanced InSAR techniques developed in
the last decade are capable of providing millimeter precision, comparable to optical leveling, and a high
spatial density of displacement measurements, over long periods of time without need of installing
equipment or otherwise accessing the study area.
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Integrated Reservoir Analysis and Geochemistry Leads to Increasing Production from Underdeveloped Reservoir in the Bahrain Field
Authors Nayera K. Abdulla, Najla Nedham, Challa R. Murty and Yahya Al AnsariSince the Bahrain field was discovered in 1932, the main focus of development was on major
formations of the field, leaving shallow formations not fully exploited. Today with the increase in oil
price and the depletion of major formations, there is a greater need to consider increasing production
from these under developed zones.
This case study describes the measures applied with the purpose of increasing production from the
Magwa zone, which is the most economically attractive of the shallow zones. The zone is the basal
member of the Rumaila formation of the middle Cretaceous Wasia group. It is predominantly limestone
with interbeded shale. An integrated methodology was adopted to enable a better understanding of the
reservoir production behavior and to explain the lateral heterogeneity of the formation. This
investigation was triggered by the variation in the formation water salinity from North to South. Water
saturation maps, rock type, production history, geochemistry and structural set-up were used as the
main inputs in this analysis. The interpretation of trends between these factors were used to explain
the behavior of the reservoir. The outcome of such investigations is of critical value in determining the
location of new development wells, selecting candidate wells for recompletion and planning for EOR processes.
This paper will explain how a better understanding of the reservoir through data integration has
resulted in a significant increase in oil production.
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Fluid Status and Saturation Assessment in Low Resistivity Pay Carbonate Reservoir, Using Core Scale Petrophysical and Resistivity Modelling
Authors Francois Umbhauer, Jean Pierre Leduc, Eric Guyotte and Abubaker ElSadawiFluid status definition for completion strategy, or reliable saturation evaluation for hydrocarbon in place
and reserves estimation in heterogeneous carbonates reservoirs, based on wireline resistivity logs, is
often uncertain as these reservoirs often deviate from Archie’s law.
This can be explained by small scale heterogeneities (patchy macroporous oil zones embedded in a
microporous matrix) which can generate an excess of conductivity (electrical bypass through water
saturated microporous connected path). Applying Archie’s law with the standard m and n =2 values in
such cases may lead to erroneous water saturation computation, with serious consequences on fluid
status, completion strategy and project economics.
A methodology has been developed to tackle this problem by: 1) modelling reservoir heterogeneity at
core scale using commercial geomodelling software, providing a reference oil volume calibrated by core
petrophysical data (CT scan 3D imaging, minipermeameter, porosity, permeability, capillary
pressure) ; 2) checking the accuracy of the model through forward modelling, using a research 2D
resistivity modelling software simulating the invasion process, by comparison with the acquired
wireline resistivity logs response.
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Basin Analysis and Organic Source Facies Studies of the Jurassic/Cretaceous Sediments in Northern Sinai, Egypt
Authors Esam Abdelgawad, Abdulrahman Alsharhan, Mostafa M. Lotfy and Ayman El SaiThe Sinai Peninsula is bounded by the Suez Canal and Gulf of Suez rift to the west, the transform Dead
Sea-Aqaba rift to the east and the Mediterranean passive margin to the north. The stratigraphic section
in North Sinai ranges in age from Pre-Cambrian to Recent and varies in thickness between 2000m of
mostly continental facies in the south to almost 8000m of marine facies in the north.
The northern Sinai represents an important hydrocarbon province in Egypt, but the origin of the
hydrocarbons and their migration is not fully understood. Structural, stratigraphic and combination
traps are encountered in the study area. The North Sinai district has a good oil exploration potential,
and only a few plays have been tested.
In this study, we evaluated the organic source facies and assess the results of basin modeling in order
to improve our understanding of the regional petroleum system in that region.
Organic/inorganic geochemical and petrographic analyses of 80 rock samples ranging in age from Early
Jurassic to Cretaceous were accomplished. Most of the studied samples had moderate to high TOC
contents and mixture type II/III kerogen with a wide range of petroleum generation potentials from
very poor to very good. Thermal and burial history models indicated that the source rocks entered the
early-mature/mature stage in very recent times. The top of the oil window ranges in depth from 3000
m to 4,300 m, whereas the bottom of the oil window was not reached by most of the studied wells. In
combination with numerical modeling results, structure contour maps for key horizons revealed
possible migration trends and prospective areas. We tentatively identified prospective targets for
hydrocarbon exploration in the Cretaceous succession, especially where carbonate build-ups are present.
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Study of Microfacies and Sequence Stratigraphy of the Fahliyan Formation in the Marun Oil Field, Northern Dezful Embayment, Southwestern Iran
Authors Amir Feghhi, Bahram Habibnia, Hassan Amiri Bakhtiar and Shahram AvarjaniConsidering all different formations in Zagros basin, the Cretaceous column has a remarkable position.
“Fahliyan” carbonate formation with the age of Neocomian (early Cretaceous) is a main reservoir of
Khami group and is extended in whole Zagros depositional basin. The equivalent formation of
“Fahliyan” formation in Saudi Arabia, Bahrain and Qatar is “Yamama” formation and in Kuwait from
older to earlier; “Makhul”, “Minaghish” and “Ratawi” formations (Setudenia, 1978). According to
characteristics of Fahliyan’s equivalent formation in Saudi Arabia and Qatar (“Yamama” formation), it
looks that their depositional conditions had been very alike to each other. In the past, several
geological studies had been done on this formation (mostly using lithostratigraphy and biostratigraphy
points of view), however concerned with its performance of being a high-quality reservoir and since
Marun oil field is one of the top biggest oil fields in Dezful embayment and Iran, there was a critical
need for more detailed studies to help hydrocarbon exploitation from Khami group in this field. This
research was mainly an effort to this aim.
This research has been done based on petrographic methods and using methodology and principles of
sequence stratigraphy. Moreover, well logs have been used as a subsidiary tool to assess the sequence
stratigraphical studies. To describe microfacies and to determine their depositional environment,
“Wilson” (1975) and “Flügel” (2004) methods have been applied and for nomenclature of carbonate
rocks, “Dunham” (1962) method has been used. After recognition of microfacies and evaluation of
lateral and vertical variations (using Walter’s law) depositional model of Fahliyan formation was
proposed. Then, sequences of Fahliyan formation and their systems tracts were identified. At the final
stage, compartments with more reservoir potential were recognized.
Generally speaking, the main tasks having done during this study are as below:
Study of microfossils (benthic foraminifera and algae)- Relative age determination of “Fahliyan”
formation (based on age of microfossils)- Study of different kinds of microfacies- Study of depositional
environment and sedimentary cycles- Sequence stratigraphy of “Fahliyan” formation in well section-
Evaluation of “Fahliyan” reservoir characteristics in Marun oil field- Assessment of relation between
microfacies with reservoir potential and sedimentary cycles of “Fahliyan” formation using thin sections and well logs
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Integration of Seismic and Well Data to Characterize Tar Mat in Carbonate Reservoirs
Authors Tarek M. Matarid, Christoph T. Lehmann, Khalil I. Hosani, David Cobb and Adrian SmithThis paper presents an integrated approach using the 3D seismic and well data to enhance our
understanding of the lateral and/or vertical distribution of the Tar Mat.
The study carried out utilizing a recent stat-of-the-art 3D ocean-bottom seismic technology (OBC) with
high resolution and high quality offshore Abu Dhabi and several wells with excellent suit of logs,
thousand feet’s of core data and geochemical studies.
A Model Based Acoustic Impedance Inversion was conducted following the 3D seismic reservoir
mapping. A comprehensive porosity prediction analysis and validation were conducted for each well.
The observation of the abrupt destruction of porosity in the well data associated with Tar Mat presence
in the core did trigger the idea of computing the porosity derivative cube from the seismically predicted
porosity cube. This significant and dramatic change in porosity associated with the Tar presence
suggested that this porosity destruction might be visible in the seismically predicted porosity cube.
The derivative of the porosity volume after post-stack Impedance inversion was generated to visualize
the rate of changes in porosities. The high negative porosity derivative in a highly porous section may
represent the top of a tar mat. The high positive porosity derivative values also can be used to indicate
Tar free developed porosity. Good match was found between the generated porosity derivative volume
and the top tar from wells.
The cross-plots between the seismic acoustic impedance and porosity for all wells (including Tar wells)
suggesting difficulty to distinguish between Tar and lithology change for porosities less than 10%.
The lateral Tar distribution was found to be predictable utilizing post stack 3D seismic acoustic
impedance inversion followed by porosity prediction and its derivative volume.
The seismic Tar mat prediction on the porosity volume has provided new and important interpretation
of the top of the Tar in the inter-well region and for the static model. Different Tar prediction schemes
from seismic have been evaluated for further refinment. Differentiating in tight rocks and to recognize
the remaining porosity plugged with tar remains ambiguous in the lower reservoir tight rocks.
Therefore, a detailed sampling and geochemical analysis of the tar is being performed on the core to
determine the base of the tar.
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Reservoir Permeability Estimation Using Neural Network and Geostatistical Approaches
Authors Keyvan Najafzadeh, Mohammad A. Riahi and SeyedMohsen SeyedAliEstimating permeability from well log data in uncored borehole intervals is an important difficult task.
On the other hand, direct prediction of reservoir permeability from seismic data is often supposed
impossible due to resolution limitations of seismic data and hydraulic nature of permeability. In many
cases reservoir permeability estimation is restricted to core scale and wellbore proximity. Commonly,
permeability is estimated from various well log curves using empirical relationships or multiple linear
regression (MLR), but it seems that artificial neural network (ANN) produces a more reliable response
related to reservoir permeability estimation. The aim of this article is to build a reliable structural
model of study area from seismic data, then a back propagation ANN is used for reservoir permeability
estimation in uncored intervals. Also geostatistical approaches are used for permeability estimation. At
last validity of methods has been checked by cross validation and a comparison between methods has been made.
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Results of Feasibility Study of Surface-to-Borehole Time-Domain CSEM for Water-Oil Fluid Substitution in Ghawar Field, Saudi Arabia
Authors Daniele Colombo, Shiv Dasgupta, Kurt M. Strack and Gang YuMonitoring the advancement of flood from water injection in carbonate reservoirs is a major challenge
for geophysical methods. 4D seismic has limited applicability to Middle East reservoirs with low gas-oilratio
in carbonate rocks. On the other hand, electromagnetic (EM) methods hold the largest potential in
such reservoirs due to the large resistivity contrast (over one order of magnitude) between oilsaturated
and water-saturated reservoir rocks. Electromagnetic measurements, however, are noise
sensitive thus special configurations need to be implemented to enable the detection of the extremely
small variations of the electromagnetic field that are induced by oil being replaced by injection water.
Controlled source EM transmitters on ground surface and borehole receivers represent the most
effective layout configuration to improve the signal-to-noise ratio and to augment the aperture of
investigation while addressing the signal-to-noise challenge through long recording times. Transient
time-domain controlled-source EM techniques also provide broadband EM measurements and adapt to
most geologic scenarios and to the conditions characterizing the Ghawar field.
An advanced 3D modeling study was carried out by considering real reservoir geometry from 3D
seismic interpretation, anisotropic resistivity distribution from tri-axial resistivity logs (acquired from
surface to reservoir depth in the monitoring well) and time snapshots of fluid saturations modeled in
reservoir simulators. The study allows the determination of EM field sensitivity to fluid saturation
changes in in-situ reservoir conditions. Results indicate the vertical component of the electric field (Ez)
is the most sensitive parameter to fluid replacement for a survey layout consisting of surface galvanic
transmitters radially distributed around the well and a single, multi-level, borehole receiver. Repeated
EM modeling over different time snapshots evidence the possibility to effectively monitor in three
dimensions the resistivity changes occurring in the reservoir as the water flood front advances.
Estimates of the EM field strength allow quantitative evaluations of the noise floor required to detect
the variations of the electromagnetic field. These estimates will be used in a successive phase of the
study where actual noise measurements and noise cancellation techniques will be tested in the field.
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Application of Phase Inversion Deconvolution (PID) in Multiple Attenuation
Authors Abdolah Kiani, Abdolrahim Javaherian and Nasser KazemiThis paper describes the analysis of the continuous alteration of the acoustic waveform propagating
through the linear system (earth). Based on results of this analysis, the surface related measurements
are described as a convolution of the impulse response of the system with the nonstationary forward
wavelet. In Phase Inversion Deconvolution method, we consider a forward wavelet includes all multiple
terms generated within the system as well as the energy source signature, absorption, geometrical
spreading and the receiver characteristics. The multiples are discriminated from primaries based on the
difference between the phase spectrum of the seismic signal and the inverse of the forward wavelet.
The conditions of separability of primaries and multiples, and impulse response of system are analyzed
and illustrated using wavelets extracted from the real seismic signal in cepstrum domain. We applied
this method for real data, which acquired in SW of Iran, and expect that can attenuate the multiples,
return the decayed energy to the same level, and remove the source and the receiver properties from
the recorded signal. So PID can be one of the primary and essential steps of AVO interpretation and
direct gas detection.
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Using Seismic Attributes to Delineate Fractures
Authors Satinder Chopra and Kurt J. MarfurtFractures can enhance permeability in reservoirs and hence impact the productivity and recovery
efficiency in those areas. Fold and fault geometries, stratal architecture and large-scale depositional
elements (e.g. channels, incised valley-fill and turbidite fan complexes) are often difficult to see clearly
on vertical and horizontal slices through the seismic reflection data. Seismic attributes help us in
characterizing stratigraphic features that may comprise reservoirs, and form an integral part of most
interpretation projects completed today. Coherence, curvature and relative acoustic impedance are
some important seismic attributes that are used for such analysis. However, for extracting accurate
information from seismic attributes, the input seismic data needs to be conditioned optimally. This
includes noise removal, using robust dip-steering options and superior algorithms for computation of seismic attributes.
Curvature attributes in particular exhibit detailed patterns for fracture networks that can be correlated
with image log and production data to ascertain their authenticity. One way to do this correlation is to
manually pick the lineaments seen on the curvature displays for a localized area around the borehole,
and then transform these lineaments into rose diagrams to compare with similar rose diagrams
obtained from image logs. Favorable comparison of these rose diagrams lends confidence in the
interpretation of fractures. Another way is to generate automated 3D rose diagrams from seismic
attributes and correlate them with other lineaments seen on the coherence attribute.
3D volume rendering is one form of visualization that involves opacity control to view the features of
interest ‘inside’ the 3D volume. A judicious choice of opacity applied to edge-sensitive attribute subvolumes
such as curvature or coherence co-rendered with the seismic amplitude volume can both
accelerate and lend confidence to the interpretation of complex structure and stratigraphy. Volume
visualization of stratigraphic features is a great aid in 3D seismic interpretation and can be greatly
aided by adopting cross-plotting of seismic discontinuity attributes in the interpretation workflow as we
will demonstrate in this presentation.
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Detecting Stratigraphic Features via Cross-Plotting of Seismic Discontinuity Attributes and Their Volume Visualization
Authors Satinder Chopra and Kurt J. MarfurtFold and fault geometries, stratal architecture and large-scale depositional elements (e.g. channels,
incised valley-fill and turbidite fan complexes) are often difficult to see clearly on vertical and
horizontal slices through the seismic reflection data. Consequently, visualization techniques are used
for viewing the data, whether it’s the input seismic data or derived data in terms of seismic attributes.
Such visualization helps extract meaningful information, allows for greater interpretation accuracy and
improves efficiency. 3D volume rendering is one form of visualization that involves opacity control to
view the features of interest ‘inside’ the 3D volume. A judicious choice of opacity applied to edgesensitive
attribute sub-volumes such as curvature or coherence co-rendered with the seismic amplitude
volume can both accelerate and lend confidence to the interpretation of complex structure and stratigraphy.
In addition to co-rendering, we evaluate an interpretation workflow that cross-plots pairs of edgesensitive
attributes. By crossploting coherence and an appropriate curvature attribute, we can define a
polygon that highlights “clusters” that exhibit low coherence (indicating a discontinuity) and high
curvature (indicating folding, flexing, fault drag, or differential compaction). Modern volume
interpretation software allows us to link and display these interpreter-defined clusters in the seismic
volume for further examination. Once identified interactively, such visual ‘clustering’ can be used to
supervise geobody delineation using neural networks and other classification algorithms. This saves the
seismic interpreters considerable time and effort. We illustrate this new workflow through application
to several 3D seismic surveys recently acquired in western Canada and demonstrate that multiattribute
volume co-rendering and clustering provides a powerful tool that leads to a better understanding of the
spatial relationships between seismic attributes and the geologic objectives being pursued.
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Integrated Reservoir Management Leads to Improved Productivity from Khuff Gas Reservoir of Bahrain Field
Authors Challa RK Murty, Salah S. Abdulla and Ebrahim AlowainatiBahrain Field is a mature asset containing several oil and gas reservoirs. The bulk of Gas reserves are
located in Khuff and Pre-Khuff (Unayzah) reservoirs. The Khuff is a carbonate reservoir that is
subdivided into four units - KO , K1, K2and K3. These gas reserves are vital for the country because
they represent the main domestic energy supply. All the subunits are highly productive except K3
where the production is marginal as it is derived mainly from the fractures.
An integrated Reservoir monitoring is in place to improve the asset management of this critical
resource. This includes (a) updating reservoir description using the data from Core Analysis (b)
ensuring proper depletion by monitoring the reservoir pressure, (c) reviewing the production
performance from various units, (d) recording the deliverability of wells periodically (e) revising the
perforation intervals based on the rock typing and (e) monitoring the movement of Gas water contact.
A yearly surveillance program is implemented regularly to acquire data from the reservoir. The
deliverability of the wells is monitored using the SCADA system. A study on the system pressure
reduction was undertaken which indicated that the productivity can be enhanced by reducing the well
head tubing pressure. Accordingly the gas dehydration units are being modified to handle production
with low well head pressures. The reservoir perforation policy is also revised using the study which
helped in improving the productivity. This paper discusses how the integrated study helped in providing
a good frame work needed to assess the best ways to improve the exploitation of the gas reserves.
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Controls from Formation of Early Replacement Dolomites and Diagenetic Anhydrite: Reactive Transport Modeling of Dynamic Interactions between Geothermal and Reflux Circulation
Authors Anwar B. Al-Helal, Fiona Whitaker and Yitian XiaoGeothermal heating and brine reflux have been invoked to explain early dolomitization of platform
carbonates. Reactive transport modeling (RTM) suggests that geothermal convection can form a wedge
-shaped dolomite body thickest at the platform margin, while reflux can form a tabular body which
thins away from the brine source. In natural systems flow will respond to both drives and vary through
time with changes in platform top conditions, for example as brine pools develop and disappear, and
this likely to significantly impact both dolomitization and associated anhydrite precipitation.
TOUGHREACT is used to investigate the dynamic interactions geothermal convection and brine reflux.
Reflux of brines (85‰) rapidly restricts geothermal convection to the platform margin where only
minor dolomitization occurs. Brines infiltrate to considerable depth, but fluid flux is most rapid at
shallow depth due to reducing permeability with depth, permeability anisotropy, and diagenetic
modification of permeability. Simulations suggest, complete dolomitization to 150-200 m depth within
1 M.y. beneath the brine source.
Reflux dolomitization may enhance reservoir quality at shallow depth associated anhydrite precipitation
occludes porosity beneath the main dolomite body. The predicted anhydrite volume is almost twice
that suggested by earlier simulations that do not incorporate heat transport. Increasing geothermal
heat flux has little effect on geothermal circulation, but does accelerate reflux diagenesis. Cooling the
platform top from 40 to 25°C slows reactions and displaces the anhydrite zone downwards so it may
become completely decoupled from the brine source.
When brine-generating conditions cease, subsurface brines will continue to flow and have been
suggested as a drive for continued dolomitization (a variant termed “latent reflux”). Our simulations
demonstrate that latent reflux does not form a significant amount of dolomite due to prior Mg2+
consumption at shallow depth, although as geothermal circulation becomes re-established, platform
margin dolomitization rates increase.
RTM offers considerable potential for improving our understanding of diagenetic reactions and their
impact on reservoir quality in such hybrid flow systems. However, the veracity and utility of predictions
depend on the specification of meaningful boundary and initial conditions, and the temperature regime
appears to plays a critical role in the dolomitization and anhydritization story.
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Using Hilbert Transform as a Tool for Random Noise Attenuation and It’s Application from One of the Iranian South East Oilfields
Authors Hamid R. Soleymani and Mohammad A. RiahiUsing Hilbert transform as a tool for random noise attenuation and it’s application at one of the Iranian south east oilfields.
Seismic data always consist of a signal and a noise component. What has to be considered as noise
depends on the application? However, as a general defnition we can say that any recorded energy
which interferes with the desired signal can be considered as noise. The noise can be classifed as
background noise (for instance wind, swell, noise from nearby production, or interference from nearby
seismic acquisition), source-generated noise (for instance direct and scattered waves or multiples), and
instrument noise and can show up as coherent or incoherent energy in seismic gathers. This diversity
of noise types with different characteristics makes separation of signal and noise a challenging process.
In recent years, several authors have developed effective methods of eliminating random noise
(incoherent energy). For example, Gülünay (2000) used the noncausal prediction filter for randomnoise
attenuation; Ristau and Moon (2001) compared several adaptive filters, which they applied in an
attempt to reduce random noise in geophysical data; and Karsli et al. (2006) applied complex-trace
analysis to eismic data for random noise suppression, recommending it for low-fold seismic data. Also
Some transform methods were used to eliminate seismic random noise, e.g., seislet transform (Fomel,
2006; Fomel and Liu, 2008), and curvelet transform (Neelamani et al., 2008).
We use a procedure, complex-trace transformation (CTT) that uses complex-trace envelope and
normalized phase traces to improve the temporal resolution and to increase S/N of stacked seismic
data. We follow the technique offered by Shtivelman et al. (1986) and Karsli et al. (2006) who showed
that analysis of seismic data in complex geologic environments should be based on both group and phase correlation.
In this study, we suggest further applications of the method for resolution improvement and randomnoise
suppression, which have not been considered by Shtivelman et al. (1986) and Karsli et al.
(2006). The applicability of the method for temporal resolution improvement in presence of
interference effects and random noise is also discussed with examples of synthetic and field seismic
data from one of the Iranian south east oil fiels where the Hilbert transform denoising method has
successfully attenuated the noise and allowed for improved imaging.
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Role of Sedimentology and Petrography in the Development of Khuff Reservoirs,<br>Bahrain Field - a Case Study
Authors Masoud Faqihi, Suresh Kumar, R.N. Govinda Rao and Ibrahim JaberThis paper highlights the petrography and sedimentology study carried out for Khuff gas reservoir of
Bahrain field. The topics include a review of the core analysis Electrical, Sonic, Full bore Formation
Micro Imager (FMI) logs, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) studies. The
study helped in explaining the mineralogy, dolomitization, diagenesis and evolution of the pore system of the reservoir.
The study indicated four different facies (a) Peloidal-lime-grainstone to Packstone, Skeletal lime
grainstone facies which is interpreted as being very coarse grained, deposited relatively with a high
energy, shoal environment, (b) Bioturbated-Lime- Mudstone & Lime-wackestones facies, which are
interpreted to be that of lagnoonal environment. (c) Dolomudstone facies, with dolomitized mud
supported sediments are interpreted as shallow, restricted lagoon in a supratidal setting. (d)
Dolopackstone facies, interpreted as being deposited within a shoal environment.
According to the study, depositional environment is identified as lagoonal during transgressive phase
and shoal during regressive phase. The diagenesis is dominated by compaction indicated by tight
textures in mud rich samples and deformation of framework grains. Porosity enhancement is seen due
to the grain dissolution and rare fracturing while porosity destruction is carried by compaction of
sparse calcite cement and dolomite. Calcite is the dominant mineral in some samples. The clay content
is found to be very minor.
SEM analysis showed the presence of good porosity including inter-particle and inter-crystalline
porosity. The average porosity is about 17% and the permeability is about 60 md and very few
fractures are observed in this formation.
This integrated study helped in understanding the reservoir heterogeneity and its potential based on
which current wells were completed appropriately and this would also aid in completing the future wells productively.
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Reservoir Characterization of Fadhili Reservoir, Bahrain Field -A Case Study
Authors Masoud Faqihi, R.N. Govinda Rao, Suresh Kumar, Ebrahim Jaber, Habeeb Baqer, Ali E. AL-Muftah and K. KumarThis paper describes a practical approach that led to improve the production from one of the unexploited
reservoirs in the Bahrain Field and increased its potential recovery. The Fadhili reservoir, a
middle Jurassic carbonate, is about 185' thick and overlain by tight Dhruma limestone, with an oil
column of 50-70' in thickness. The reservoir quality is good in the top 3 stratigraphic layers but
progressively deteorites towards the base of the reservoir. The low formation resistivities in the oil
bearing zones are attributed to the high formation water salinity, which makes the formation
evaluation difficult.
Vertical wells begin production with low water cut, which gradually rises to more than 95% during the
course of production. Six vertical wells drilled in this reservoir have produced 156 MMSTB of oil as of date.
Initially, based on the poor performance of the vertical wells, the Fadhili was thought to be a poor
prospect. However, a simulation model built to study the production behavior of the reservoir indicated
that the production potential can be increased if an appropriate well type is chosen for this reservoir.
Based on this study, to ensure maximum reservoir contact, a horizontal well was drilled, targeting the
top 10-20' of the oil column, to evaluate oil production potential of the reservoir. During the last six
months, this horizontal well alone has produced more than the total production of all the 6 vertical
wells put together drilled in the past.
The encouraging production results (high on oil/low on water) prompted a review of the geological
model and petrophysical properties of the reservoir for a) better reservoir characterization, b)
identifying reservoir flow units and c) estimation of reserves. This paper highlights the results of the study.
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Integrated Basin and HC Systems Model, Silurian-Carboniferous, Southern Algeria
Paleozoic basins of southern Algeria comprise several HC systems: i) infra-Cambrian (?) source rock,
Upper Ordovician reservoirs; ii) Silurian source rock, Lower and Middle Devonian reservoirs ; iii) Upper
Devonian source rocks, Lower Carboniferous reservoirs. Since 2006 commercially productive gas
reservoirs have been proven by several wells in the Reggane and Ahnet Basins. Previous basin
evaluation has proposed HC generation predominantly during Mesozoic reburial, with pre-Hercynian
generation having been largely ineffective (Purdy & MacGregor 2003, Geol. Soc. Spec. Publ. London, v.
207). Thermochronlogical data (Logan & Duddy 1998, Geol. Soc. Spec. Publ. London, v. 132) have
indicated two-phased HC generation: i) simple burial heating to oil window before peak Hercynian
orogeny (pre-Early Carboniferous); ii) Late Triassic heating to wet and dry gas window in the Latest
Triassic, related to the development of the Central Atlantic Magmatic Province (CAMP) and doleritic
dykes/sills (Reggane Basin); iii) subordinate heating of less mature basin margins until recently.
In order to better assess the basin and HC development including the recently proven gas plays, an
integrated study has been performed including: i) seismic and sequence stratigraphy at basin and
reservoir resolution; ii) numerical basin modeling (subsidence/uplift, sediment flux); iii)
palynostratigraphic (miospores, acritarchs) and organofacies analysis; iv) paleotemperature analysis
including organic maturation, apatite and zircon fission track and (U-Th)/He dating. Focus is on the
Reggane Basin, where ample 2D seismic coverage and calibration wells (logs, samples) have been
available. Results include: i) trans- and regressive trends within the basin fill; ii) intra- and inter-basin
correlation iii) lateral continuation and vertical connectivity of reservoir sandstones; iii) accommodation
and sediment flux history; iv) paleotemperature development related to pre- and post-Hercynian burial
and exhumation. The new data show, that the existing models of HC development for the Upper
Silurian-Lower/Middle Devonian and Upper Devonian-Lower Carboniferous systems have to revised.
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Velocity Estimation by Focal Transform
Authors Siyavash Torabi and Abdolrahim JavaherianObtaining a reliable velocity function is still an important problem in seismic processing. The most
important reason to construct a reliable velocity function is to obtain the best quality stack of a given
signal. In this paper, focal transform is introduced as a tool in velocity analysis. By using focal
transform, it is possible to have a velocity function with higher resolution compared to that of the
traditional method. From a physical point of view, the principal action of forward focal operator is
removing the spatial phase of the signal content from the input data and the inverse focal operator
restores what the forward operator has removed. This method is based on the fact that shape of
hyperbolic event in focal domain depends on the difference between operator shape and the event.
Measuring the difference between operator and event can be somehow used as an indicator and
through applying this indicator, velocity of each event can be determined. This method works properly
for synthetic data with different level of noise and also it can distinguish similar events with small
differences in velocity and time. Quality of the velocity function that is obtained through this method is
not affected by multiples and those are easily distinguished from primaries.
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Mobility Control Requirement in Enhanced Oil Recovery Processes
By James ShengMobility control is essential in any EOR process. We know that the displacing phase mobility should be
less than or equal to the displaced phase mobility. If we take polymer flooding as an example EOR
process, the displacing phase is polymer solution, and the displaced phases are oil and water phases.
Based on the conventional concept, the polymer mobility should be less than or equal to the sum of oil
and water mobilities.
The problem is that the conventional concept is based on the conditions that the displacing phase and
displaced phase move at the same velocity and one fluid is displaced by another fluid. However, in the
polymer flooding case, two phases, oil and water, are displaced by polymer. And the oil and water
phases move at different velocities. Therefore, the conventional concept cannot be applied to the
polymer flooding process or a general EOR process.
In this paper, we first demonstrate using simulation approach that the above conventional concept is
invalid in polymer flooding case. Based on the theoretical stability analysis of displacement front, we
propose that the displacing polymer mobility should be less than or equal to the oil phase mobility.
The above mobility requirement is validated by extensive simulation results at different conditions. It is
also justified by field practices. The new concept helps us to select the correct polymer concentration
for a practical EOR process.
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2D Crustal Seismic Velocity Structure beneath Quchan Seismic Network Using Inversion of Local Earthquake Travel times
More LessQuchan has been destroyed frequently from 1870 until now. This city which is located in central Kope
Dagh region has experienced four destructive earthquakes in 1851 (M 6.9) , 1871-1872 (M 7.2), 1893
(M 7.1) and 1895 (M 6.8). These earthquakes caused widespread devastation and heavy human loss in
Quchan and many surrounding villages. These events are the largest earthquakes occurred in the Kope
Dagh in the past 160 years. What is responsible for these earthquakes is not known clearly yet. The
Kope Dagh is a linear mountain range separating the shortening in Iran from the stable flat
Turkmenistan platform. In its central part an array of active right-lateral strike-slip faults exists that
obliquely cut the range and produce offsets of several kilometres in the geomorphology and geological
structure. Quchan Fault and Baghan Fault are two prominent faults of this array which is located N and
N-W of the Quchan and it is not known that whether these faults continue to the town and south of its
or not. In this study we tried to answer this question with 2D Crustal Seismic velocity structure
beneath Quchan seismic network and used inversion of local earthquake travel times. Finally We
indicate some evidences and discussed about them (like focal mechanism, topographic map, satellite map and etc.).
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The Use of Passive Adsorbents for the Assessment of Hydrocarbon Charge in the Shallow Waters around Bahrain
Authors Ray Fenstermacher, Naji Ahmed Qassim and Larry SmithThis document will summarize the efforts to assess hydrocarbon charge in the shallow waters around Bahrain.
Shallow water presents a challenge for the exploration and prospect development of hydrocarbon
reserves. The surf zone is a high-energy environment that is frequently avoided due to the expense of
seismic acquisition in these water depths.
To help overcome the exploration uncertainty presented by these shallow transition areas, divers
deployed over eight hundred passive devices in the sediment for the collection and assessment of
geochemical data as part of this reconnaissance survey. The passive adsorbents were embedded in the
sediment to a depth of 10 - 20 cm, and left in place for an average of 17 days.
Samples were deployed in four separate areas with an average distance between points of
approximately 1 km. The water depths ranged from less than 1 meter to approximately 20 meters in
the deepest block. Many of the samples were embedded near living coral reef with no disturbance to
this sensitive habitat; supporting the premise that this technique is environmentally neutral and does
not significantly affect even the most highly sensitive habitats. Samples were also placed around select
analog wells in order to provide a means of comparing a known geochemical signature to the unknown areas.
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Chemical Stratigraphy: Feasibility of High Resolution Correlation - Outcrop Case<br>Study of a Submarine Slope Channel Complex (Tabernas Basin, Spain)
Chemical stratigraphy is the application of whole-rock inorganic geochemical analyses to characterize
and correlate strata, based on the recognition and interpretation of subtle variations in the bulk
chemical composition of sedimentary rocks. In recent years it has become an important tool in
enhancing correlation in subsurface reservoir successions in exploration industry. However this
technique widely lacks integration with sedimentological-based stratigraphic correlation methods, e.g.
lithostratigraphy, sequence stratigraphy. This study set out to examine the validity, accuracy and
limitations of the chemostratigraphic technique as correlation tool with the aid of outcrop studies
testing chemical stratigraphic correlations against sequence stratigraphic correlations.
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Mississippi Valley Type (MVT) Mineralization in the Khuff C Reservoirs, Saudi Arabia
More LessMississippi Valley Type (MVT) mineralization emplaced pyrite, sphalerite, galena, and gangue minerals,
such as saddle (baroque) dolomite into the C carbonate of the Khuff Formation, of Upper Permian age.
In most cases small percentages of MVT mineralization had been identified in several Khuff reservoirs,
both onshore and offshore. In one particular case MVT mineralization was represented by complete
replacement of carbonate beds and consisted of multiple, thick layers of mineral deposits that
contained moldic porosity. X-ray diffractometry confirmed the presence of pyrite, sphalerite, and
galena.
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Impact of High Resolution Seismic from Reservoir Modeling Minagish Oolite<br>Reservoir, Minagish Field, Kuwait
Authors Abdel M. Ebaid, Taher El Gezeery and Rakesh BahugunaThe Minagish field has several reservoirs with oil accumulated primarily in lower Cretaceous Minagish
Oolite -middle member (MMO) rocks. This giant carbonate hydrocarbon accumulation was discovered in
1959 and accounts for over 90% of oil production in the Field. As the reservoir pressure started to
decline, there was a need for water injection on the flanks of the structure to support the reservoir
pressure and to increase the oil production. The sequence stratigraphic analysis based on well logs,
cores and the old 3-D seismic sub-divided the reservoir into 13 geological layers with multiple phases
of ooid shoal development.
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Active Fluid Regime of the Basement Fractured Zones in Volga-Ural Region
More LessThe parametric well Novo-Yelkhovo-20009 penetrated loosely aggregated zones of the crystalline
basement including those occurring at a depth of more than 3.0 km below its top. Geophysical data
indicate aggregated zones. Most of them occur at a depth of more than 5000 m. From 1991 through
1996, mud sampling was repeatedly conducted in the well at specified depths, and the gas saturation
was studied. These studies showed that the amount of dissolved hydrocarbon gases and their
composition changed with time. Regrettably, no production tests have yet been conducted on the
loosely aggregated zones. These are supposed to contain brines and dissolved gases including
hydrocarbon ones. The quantitative and compositional variations of the dissolved gas recorded in the
course of the monitoring indicate its movement in the loosely aggregated zones due to possible
geodynamic and pressure changes in these zones. This means that the loosely aggregated zones of the
basement are geodynamically active.
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Investigations of the Basement Fractured Zones in the Volga-Ural Region
Geological structure of the Russian plate, including the territory of the Tatarstan Republic, and oil and
gas presence in the sedimentary cover of this region permit a conclusion that the Precambrian
crystalline basement (CB) can be considered as a potential target for hydrocarbon exploration. CB in
Tatarstan has been studied by deep drilling to a depth of several hundred metres to 4 km and by up-to
-date geophysical and geochemical techniques.
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Possible Oil Source Rock of Southern Caspian Sea with Consider Bivalves and<br>Gastropods
More LessMaikop series , in age upper-Oligocene to middle Miocene in Republic of Azerbaidjan (western Caspian
sea) and Caspian part its is petroleum source rock.So,considering interpret of results gained from
correlation between the Maikop series and the Miocene sediments in southern Caspian sea(Iranian
side),determined these sediments as probable petroleum source rock.Recent geochemical studies by
Research Center Oil Industry of Iran,reveald that Miocene sediments in southern Caspian sea(Iranian
side) can generate 5-10 milliard oil barrel.Therefore,in this research,Alamdeh-Galanderud and Nudeh-
Takam sections were selected and biostratigraphy studies with consider bivalves and gastropods were
done.In conclusion four conditions to form oil and gas are mentioned.
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Integrating Remote Sensing and GIS Technologies for Surface Geotechnical and<br>Geological Analysis
By Rob RossWhilst there is no substitute for the field work of experienced geoscientists in undertaking geological
and geotechnical surface mapping, increasingly surface mapping can be undertaken using remote
sensing technologies, together with GIS techniques, with greater confidence than in the past. Several
major issues caused problems with early remote sensing techniques, especially using early Landsat
satellites. Firstly, the poor resolution (80 metre pixel size) of the imagery and, secondly, the lack of
multi-spectral bands specifically dedicated to the detection of radiation useful to discriminate surface
geology.
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Comprehensive History Matching a Complex Carbonate Reservoir (Maydan Mahzam<br>Field, Offshore Qatar)
The Maydan Mahzam field in offshore Qatar is a complex carbonate oil reservoir of the Late Jurassic
Arab formation. It was brought on production in 1965, with a short period of natural depletion before
starting water injection through dump-flooders located on the flanks of the reservoir. An integrated
study has been launched by Qatar Petroleum in order to optimize the future development of the field
and maximize the future recovery of the remaining oil in place. In this context the understanding of the
main producing mechanisms of the past forty years is of major value. This requires reservoir modeling
with extensive and detailed history matching.
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Use of Pre-Stack Seismic Data to Guide the 3D Rock-Type Distribution of Arab-D in<br>Maydan Mahzam High-Resolution Geological Model
Maydan Mahzam is a carbonate field located offshore Qatar with principal oil production from the Arab-
D reservoir. In order to optimize the management of this mature field, Qatar Petroleum undertook a
comprehensive reservoir modeling exercise using an up-to-date integrated multi-disciplinary approach,
combining reservoir, geological, geophysical and production data. This paper illustrates how seismic
data has been used to quantitatively constrain the reservoir model between wells.
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Data Mining in Identifying Carbonate Litho-Facies from Well Logs Based from<br>Extreme Learning and Support Vector Machines
This research investigate the capabilities of data mining in identifying carbonate litho-facies from well
logs based on extreme learning and support vector machines. Formation facies usually influence the
hydrocarbon movement and distribution. Identifying geological formation facies is critical for economic
successes of reservoir management and development. The identification of various facies, however, is
a very complex problem due to the fact that most reservoirs show different degree of heterogeneity.
Last decade, there has been an intense interest in the use of both computational intelligence and
softcomputing learning schemes in the field of oil and gas: exploration and production to identify and
predict permeability and porosity, identify flow regimes, and predict reservoir characteristics. However,
most of these learning schemes suffer from numerous of important shortcoming. This paper explores
the use both extreme learning and support vector machines systems to identify geological formation
facies from well logs. Comparative studies are carried out to compare the performance of both extreme
learning and support vector machines with the most common empirical and statistical predictive
modeling schemes using both real-world industry databases and simulation study. We discuss how the
new approach is reliable, efficient, outperforms, and more economic than the conventional method.
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On Utilizing Functional Networks Computational Intelligence in Forecasting Rock<br>Mechanical Parameters for Hydrocarbon Reservoirs: Methodology and Comparative Studies
Rock mechanical parameters of reservoir rocks play an extremely important role in solving problems
related to almost all operations in oil or gas production. A continuous profile of these parameters along
with the depth is essential to analyze these problems which include wellbore stability, sand production,
fracturing, reservoir compaction, and surface subsidence. The mechanical parameters can be divided
into three main groups: viz., elastic parameters, strength parameters, and in-situ stresses. Even the
profile of in-situ stresses with depth is estimated using logs with elastic parameters as an essential
input. The focus of this article is on the prediction of elastic parameters along with the depth of a given
reservoir based on functional networks as a novel computational intelligence and data mining modeling
scheme.
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Hydrocarbon Potential of Devonian Sequence Jauf Formation - a Case Study from<br>Awali Field
Authors C.B. Reddy and Yahya Al-AnsariJauf Formation is of Lower to Middle Devonian age. It underlies Jubah and overlies Tawil formation with
conformable contacts. After deposition of Tawil, the shallow marine sands of the Jauf formation were
deposited over a broad shelf. It consists of thick Sandstone with thin Shale intercalations. Jauf
reservoir is relatively cleanest and most porous of all pre-Unayzah reservoirs. It is a continuous zone
with sand thickness varying from 250 to 400 ft. Jauf top is encountered at a depth of 11000 ft in the
structural crest and reach depths of over 15000 ft in flanks of Awali field area and penetrated in few
Awali wells. Individual porous layers are 5-15 ft thick and alternate with tight well-cemented
sandstones or shales. The zone proved to be gas bearing in a test conducted in two of the crestal wells
of Awali field. Gas shows were also reported in few drilled wells, but production testing was not carried
out in these wells.
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Evaluating Fundamental Controls from Depositional Facies Heterogeneity in a<br>Carbonate Ramp Using Forward Stratigraphic Modeling
Authors Miriam S. Andres, Paul M. Harris and Gareth D. JonesMuch of our understanding of the depositional facies heterogeneity, to date, derives from geological
concepts, outcrop studies and subsurface information. Deposited strata represent the unique solution
to a combination of fundamental controls at the time, not including subsequent diagenetic, tectonic
and/or burial overprint. Forward stratigraphic modeling (FSM), in contrast, provides an opportunity of
simulating multiple solutions by isolating one of the fundamental controls. In this capacity we use the
FSM tool ‘Dionisos’ to investigate the role of various input parameters and their control on a graindominated
carbonate ramp setting typical of the Middle East. Specifically, we focused on extent and
distribution of reservoir and non-reservoir facies as they are key to understanding and predicting
reservoir connectivity and potentially performance in carbonate ramps.
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Reactive Transport Models of Structurally Controlled Hydrothermal Dolomite:<br>Implications for Middle East Carbonate Reservoirs
Authors Gareth D. Jones, Ipsita Gupta and Eric SonnenthalHydrothermal dolomitization is present in several Middle East carbonate reservoirs including Ghawar,
the North Field and South Pars. Structurally controlled hydrothermal dolomitization describes the
replacement of limestone with dolomite and/or the precipitation of dolomite cement and associated
MVT minerals (anhydrite, sulfides, quartz and fluorite) as a consequence of subsurface brines that
ascend upwards through fault and fracture systems. This fluid rock interaction in the burial
environment has the potential to both improve and/or degrade reservoir quality depending on the
properties of the host rock, fluid composition, timing of fluid flow and spatial position relative to
structure.
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Strategies for Modeling Depositional Heterogeneity of Carbonate Ramps Using<br>Outcrop Analogs and Multiple Point Statistics
Authors Ted Playton, Jeroen Kenter, Marjorie Levy, Aurelien Pierre, Gareth D. Jones and Paul M. HarrisOutcrop exposures offer continuity, correlation, and resolution of geological data well beyond that of
the subsurface, and serve as ‘idealized’ analogs for reservoirs. In this study, measured sections,
photomosaic mapping, DGPS, and LIDAR data were collected along a 38 km dip exposure of Lower
Jurassic carbonate ramp strata in the High Atlas of Morocco, and converted into a static model using
multiple point statistics (MPS). The goal was to generate new modeling strategies through simulation
of ramp depositional heterogeneity during both transgressive (TST) and highstand (HST) conditions,
and for each of the facies belts observed (inner, middle, outer, and basinal ramp settings).
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The Ratawi Reservoir of the Partitioned Neutral Zone (PNZ), Saudi Arabia and<br>Kuwait
Authors Bonny Archuleta, Arthur Saller and Stevel BachtelThe Lower Cretaceous Ratawi Formation is a target for increased production and ongoing exploration
within the Partitioned Neutral Zone (PNZ). The Ratawi Formation consists of 3 members including: the
Ratawi Oolite (base), the Ratawi Limestone and the Ratawi Shale (top). Deposition of the Ratawi Oolite
and Ratawi Limestone occurred on a low-angle carbonate ramp roughly dipping to the east to
northeast. Oil from the Ratawi reservoir is currently being produced from the South Umm Gudair,
Wafra, and South Fuwaris fields. The purpose of this study is to better understand the reservoir
heterogeneity of the Ratawi at both the regional and field scale to provide inputs for future
development and exploration activities.
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Stratigraphy and Depositional History of the First Eocene Reservoir from Wafra<br>Field, Partitioned Neutral Zone (PNZ), Saudi Arabia and Kuwait
Authors Nial Toomey, Paul Montgomery and William S. MeddaughThe Paleocene/Eocene aged First Eocene reservoir at Wafra Field in the PNZ (Saudi Arabia and Kuwait)
is a dolomitized, heavy oil (18-22°API) carbonate reservoir. The 40 acre Large Scale Pilot (LSP) is
located in the southern portion of the field and contains 56 producers, injectors, and temperature
observation wells. Additionally, four cores were taken from the LSP area. The high well density and
variety of data types (Core, FMI, wireline logs) provides a unique opportunity to examine the
stratigraphy and depositional history of this complex carbonate system. This study focuses on the
EOC500 to EOC700 interval, which is the zone targeted for initial enhanced oil recovery.
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