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GEO 2010
- Conference date: 07 Mar 2010 - 10 Mar 2010
- Location: Manama, Bahrain
- Published: 07 March 2010
1 - 50 of 457 results
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Feasibility of Detecting Near-Surface Cavities Using Integrated Seismic and GPR Techniques
More LessThe feasibility of directly detecting near-surfaces cavities is challenging due to the complexity of nearsurface
materials and the limited resolution of seismic techniques.
Therefore, Shallow seismic survey has been applied for an area of limestone rocks includes subsurface
cavity at depth about 3 meters under the ground surface. seismic waves have been generated and
acquired with high resolution and good quality characteristics along profiles passing through the cavity
with 1 meter geophone spacing and multi-channels seismograph. During a comprehensive sequence of
data processing and using more sophisticated software for refraction tomography and multi-channel
analysis of surface waves (MASW ) , the cavity has detected at about 3 meters depth and about 30
meters of lateral extension has been clearly identified. Furthermore, the location of the cavity has been
confirmed successfully through the application of GPR surveying profiles along the inspected cave
position. The acquired GPR profiles are processed and filtered to minimize the noise effects. High
amplitude reflections are observed within the profile. These high amplitude reflections are good
indicator to the presence of cavity at a depth of 3 meters from the earth's surface with thickness of
about 8 meters and extend laterally for about 30 meters in the profile direction. It noticed that both of
lateral extension and depth to the top of the cavity have been identified through seismic and GPR data
interpretation. It is concluded that, the integration between two different near surface geophysical
techniques is powerful and helpful way in detecting not only the depth for the subsurface features but
also in determining their lateral dimensions.
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Interpreted Strike-Slip Fault Elements in the 1st Eocene Reservoir of Wafra Field, PNZ Kuwait
Authors Nader M. Eloutefi, John Smith and Fahd Al-khaldiThe Wafra field lies in the northwest part of Kuwait/ Saudi Arabia partitioned Neutral Zone (PNZ) and
the 1st Eocene is the shallowest reservoir in the field. The structure of Wafra consists of two parallel
anticlines, trending northwest - southeast. It is proposed that these anticlines are cut by northeast -
southwest elements (strike slip faults). Accordingly, structural compartmentalization has been created
due to horizontal and vertical displacements, with some rotation in the horizontal plane especially in
the southern area of the field. These elements are believed to play an important roll in the
development of structures in PNZ.
This structural domain represents the direct response to two major elements: the extension of Red Sea
to the west, and the compression of Zagros crush zone to the east.
Regionally, many observations have been detected suggesting the occurrence of these elements. These
observations are: Landsat images of Kuwait and Saudi Arabia, sinuosity of the Kuwait coast line, and
structural offset of oil fields in PNZ area i.e. Wafra, South Fawaris & Humma.
So far, micro-scanner image data has proved to be one of the best methods to provide evidence for
the presence of these elements. Abrupt changes in bedding dip attitude, deviation azimuth, and facies
plus the occurrence of intensive fractures are the main evidence for these elements (strike-slip faults).
Structure and pressure maps have been integrated with image data to verify the regional distribution
of these strike slip faults in Wafra area. Current seismic data has insufficient quality to provide support
for these interpretations.
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A Simple Technique for Estimation of Reservoir Permeability from Seismic Reflection Data Based from Biot’s Theorem
Relationships among elastic parameters and rock properties, and ultimate reservoir parameters have
been established in continuum mechanics and rock physics. Therefore, it should be possible to estimate
reservoir permeability from the seismic data. We used Biot's solution of wave equation in an elastic
porous medium and the approximations of Turgut-Yamamoto to allow an establishment of a linear
relationship between attenuation coefficient or amplitude ratio as a function of the inverse of the
square of frequency. The slope of this function includes the permeability. It can be shown that this
technique agrees to the measurement of the permeability of a porous medium from seismic
waveforms. We examined this technique to estimate the reservoir permeability by using synthetic
seismogram data. The result show that has an error less than 5 %, it means that the study of
permeability estimation from surface seismic data is possible by using an accurate calibration step. The
procedure is tested on 3D seismic data over part of Duri field in central Sumatra, Indonesia. The
simplicity of the theoretical approach requires the introduction of an empirical calibration factor that is
provided by well SM#A in the area. This factor is then implemented to estimate the permeability with
seismic data on the field; it gives a permeability map of the study area. A key result of the study is
that permeability estimation with surface seismic data are possible but requires calibration. A
confirmation and validation of this procedure will be subject to future work.
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Neural Permeability Prediction of Heterogeneous Gas Sand Reservoirs
Authors Gharib M. Hamada and Moustafa ElshafeiAnalysis of heterogeneous gas sand reservoirs is one of the most difficult problems. These reservoirs
usually produced from multiple layers with different permeability and complex formation, which is often
enhanced by natural fracturing. Therefore, using new well logging techniques like NMR or a
combination of NMR and conventional open hole logs, as well as developing new interpretation
methodologies are essential for improved reservoir characterization. Nuclear magnetic resonance
(NMR) logs differ from conventional neutron, density, sonic and resistivity logs because the NMR
measurements provide mainly lithology independent detailed porosity and offer a good evaluation of
the hydrocarbon potential. NMR logs can also be used to determine formation permeability and
capillary pressure.
This paper concentrates on permeability estimation from NMR logging parameters. Three models used
to derive permeability from NMR are Kenyon model, Coates-Timer model and Bulk Gas Magnetic
Resonance model. These models have their advantages and limitations depending on the nature of
reservoir properties. This paper discusses permeability derived from Bulk Gas Magnetic Resonance
Model and introduces neural network model to derive formation permeability using data from NMR and
other open hole log data. The permeability results of neural network model and other models were
validated by core permeability for the studied wells.
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Quantitative Characterisation of Intertidal to Supratidal Sediments of the Abu Dhabi Coastline
Authors Stephen Lokier, Alice Knaf and Thomas SteuberThe Abu Dhabi coastline provides an ideal setting for the study of sedimentary systems inferred to be
directly analogous to those which deposited many of the regions Mesozoic petroleum reservoirs.
Improved understanding of these complex depositional environments, supported by quantitative
sedimentological data, is essential to the development of accurate depositional models and reliable
simulations for carbonate reservoirs.
The arid southern shore of the Arabian Gulf has an extremely low-angle ramp geometry. The coast is
locally protected from open marine conditions by a number of peninsulas and offshore shoals and
islands. Sedimentary processes in the supratidal zone are dominated by the precipitation of evaporite
minerals in the shallow sub-surface. A broad carbonate-evaporite intertidal setting, characterised by
complex depositional facies geometries, passes off-shore, into a subtidal carbonate depositional environment.
The coastline of the United Arab Emirates is currently undergoing massive infrastructure development
at an unprecedented scale, with huge dredging and island-building projects changing the sedimentary
dynamics of the coast beyond recognition. The impending loss of many of the natural coastal systems
gives further impetus to the need for accurately recording these sedimentary environments before they
are eradicated by the anthropogenic overprint.
This study employs a range of analytical techniques to investigate and characterise the surface.
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Characterization of Ahmadi Reservoir of Bahrain Field with DFN Model Using Transient Well Testing
Authors Ammar A. Shaban, Thierry Le Maux and Laurent GhilardiniThe Ab formation of the Ahmadi group in is one of the most difficult reservoirs to produce in Bahrain
Field. It has tight matrix with low permeability and complex fracture system makes it difficult to
produce. Hence, the understanding of such fractured systems is essential for modeling and improving
the production and ultimate recovery from this reservoir. To help with that, Discrete Fractured Network
(DFN) modeling has been used to characterize this fractured reservoir. If integrated with other data
from the field, DFN can provide more representative fractured models. Transient Pressure Welltesting,
a widely known applied reservoir characterization technique, can be used to validate the suggested DFN models.
This paper presents the work that incorporates a sensitivity analysis study used to test and investigate
the parameters that have a direct effect on the curve signature of the transient pressure welltest
analysis and their interpretations.
Different customized DFN models were built and simulated to obtain the pressure measurements under
different scenarios. Various pressure derivative curves were generated and compared to investigate
the sensitivity of fracture parameters on the signature responses.
The study concludes with actual field cases from the Ab fractured reservoir.
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Depositional Environment and Sequence Stratigraphy of the Neocomian Fahliyan Formation in the North Dezful Embayment, SW Iran
Authors Mostafa Sabouhi, Davood Jahani, Farid Taati Qurayem and Ali AminzadehFahliyan Formation (Neocomian) is one of the important hydrocarbon reservoirs of khami group in
south west of Iran. This Formation has 332m thickness in type section and mainly consist of carbonate
rocks. In this study,the Fahliyan Formation was investigated in subsurface section of AZN#B Well in
the north Dezful Embayment(with281m thickness). Lower boundary of Fahliyan Formation with Garau
Formation is continuous and the upper contact with Gadvan formation is conformable According to this
study 13 carbonate microfacies and one shaily facies were recognized which are grouped into four
facies associations micro facies group). These facies associations present platform to basin depositional
setting and are nominated as : A (Tidal-flat), B (Lagoon), C (Bar) and D (Open marine).
Based on available data set including cutting samples,thin sections and well log analysis, it seems the
Fahliyan Formation was deposited in a Carbonate shelf setting and the studied profile indicates the
shallowest part of the platform.Vertical succession of microfacies and relative depth changes of the
Fahliyan Formation led to identification of two third-order depositional sequence. The first sequence
includes HST only and the TST is in the Garau Formation. The upper boundary of this sequence is a
type 2 (SB2). The second sequence includes TST and HST,and upper boundary with The Gadvan
Formation is type 1 sequence boundary (SB1).
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Magnifying the Numerical Aspects of Convection-Dispersion Equation by Selecting Different Methods and Grid Sizes
More LessVirtually all reservoir simulators obtain solutions to fluid flow equations, usually nonlinear partialdifferential
equations, by, making discrete approximations to derivatives.1 Whether finite-difference or
finite-element methods are used, these approximations always introduce truncation errors that often
can distort the accuracy and stability of the solution. The truncation error is often referred to as
numerical dispersion because, to lowest order, it can be represented as a second spatial derivative
term,2 added to any true dispersion term in the problem.
Distortion of numerical solution is most significant in the simulation of EOR processes3 where sharp
displacement, concentration, and/or temperature fronts are an important part of the efficiency of the
processes, and artificial smearing as a result of numerical dispersion can render the simulation meaningless.
At this paper to investigate the effect of solution method on Numerical Dispersion two computer
programs that the first one is based on method of Finite Difference and the second is based on method
of Line-Explicit are written in MATLAB Software. Also at this paper stability of 9 cases that are included
various time and distance weighting for each method are discussed. In continue the effect of grid sizes
(Δx) on smearing and oscillation is investigated by selecting various values for Δx. The results indicate
that by using the method of Line-Explicit as solution method for general difference equation (equation
(32)), numerical dispersion will be minimized. Also, it is showed that cases of 7, 8, and 9 have
minimum numerical dispersion. At the last part of the paper, as it can be seen from Figures.37-54
decreasing the grid sizes, reduces the numerical dispersion.
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Deposition of Retrogradational Carbonate Grainstone Shoals and Subsequent Basal Barrier (Sole Seal) Development by Deposition and Diagenesis - Lower Cretaceous Ratawi Oolite Reservoir (Minagish Formation) Wafra Field, PNZ-Kuwait
Authors Osama M. El-Gendi, John Weston and Bader Al-OtaibiThe Wafra field is located in the Partitioned Neutral Zone (PNZ) between Kuwait and Saudi Arabia and
has been producing medium oil from the Ratawi Oolite Limestone reservoir since 1956.
The Wafra Ratawi is an example of a detached rimmed shelf carbonate shoal depositional system
deposited on a paleo-high in the Late Cretaceous. The depositional architecture was analyzed for major
depositional controls and to explain the existence of a sole seal (Basal Barrier) that restricted early
water encroachment and contributed greatly to the productivity of the reservoir.
The carbonate platform is made up of allochem Oolitic limestone shoals (grainstones) during relative
sea level stagnation in an overall transgressive retrogradation shoal system with shallowing upward
sequences. The reservoir is structurally trapped on three sides and stratigraphically trapped on one
side where tighter, off-shoal deeper marine carbonate wackestones and mudstones provide the
necessary reservoir seal.
As the leeward and windward carbonate grainstone shoals developed, a tighter carbonate mudstone
was deposited by reduced circulation of nutrients and aeration, and increased excessive heat, resulting
in a low stand system tract (LST) lagoonal facies. The retrogradation of these grainstone shoals with
intervening lagoonal facies resulted in a continuous development of a tighter facies across the field,
enhancing a substantially facies-driven sole-seal to the reservoir called the Basal Barrier. Diagenetic
cementation of the Basal Barrier (possibly due to Neomorphism or re-crystallization of pre-existing
carbonate fines) further reduced the sole seal permeability restricting bottom aquifer support, resulting
in lower water production for much of the production life.
As transgression continued, the grainstone forming carbonate factory was over-whelmed and drowned
by a rapid rise in sea level during the transegressive system tract (TST), and tighter, deeper marine
carbonates capped the main reservoir grainstone shoals. Complete entrapment came with continued
transgression during the highstand system tract (HST) and deposition of tight deeper marine
argillaceous carbonates grading to calcareous shales at the top forming the cap rock to the reservoir.
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Characterisation and Genesis of Oils from Unconventional Reservoirs of Ahmedabad Block, Cambay Basin, India
Authors Neelam Niranjan, Leena John, Anita Sharma and Anil GuptaCambay Basin is endowed with hydrocarbon accumulations in multiple reservoirs of different ages. In
Ahmedabad block reservoirs within Kalol Formation can be identified on conventional logs whereas
reservoir rocks in Cambay Shale are predominantly shaly and unconventional in nature with no
identifiable reservoir manifestations on well logs in fields like Sanand, Jhalora, Wadu and Indrora. The
problem of identification and quantitative evaluation of such unconventional reservoirs is being
addressed by high resolution Resistivity Imaging Tool. Identification of hydrocarbon zones is an
arduous task in such reservoirs but at the same time source of hydrocarbons is also a relevant issue.
The present work is to see if these reservoirs are self sourced or have migrated hydrocarbons.
Oils from unconventional shale reservoirs, developed in Chhatral Member of Younger Cambay shale in
Sanand field in Ahmedabad block have been characterized and correlated with oils from other
reservoirs. Source rock identification and characterization has been carried out from these and nearby
wells using pyrolysis, isotopic and biomarker studies.
It has been found that oils in these unconventional reservoirs are genetically similar to the oils in
conventional reservoirs from the same and nearby wells. The source rock is either absent in these
shales or not mature enough to generate hydrocarbons indicating that hydrocarbons from more mature
Cambay Shale or Olpad have migrated to these locales and is not in-situ generated.
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New Siliceous Microfossils in Permo-Carboniferous Rocks: Extraction, Origin, Application
Authors Holger Cremer, Oscar A. Abbink, Linda Garming, Elisa Guasti and Roel VerreusselLate Carboniferous to Middle Permian rocks resting on the Base Permian Unconformity in the
Netherlands are of great economic significance. The Rotliegend rock sequences contain the most
important gas reservoirs of the Netherlands, the Slochteren sanstones. However, the Rotliegend
reservoir rocks are typically barren of any fossils, including palynomophs, which hampers stratigraphic
control and correlation of these rocks. In a recent attempt of re-evaluation the barrenness of the
Rotliegend, siliceous microfossils, referred to as biogenic silica particles (BSPs), in considerable
morphological diversity could be extracted from these rocks. We applied a three-step approach to
prepare BSP-containing microscopic slides from Rotliegend samples: (1) pre-flotation treatments
aiming at the removal of large particles, organic matter, carbonate and clay, (2) repeated flotation
steps in order to extract and concentrate BSPs, and (3) slide preparation using Naphrax™ as mounting
medium. Many of the newly discovered siliceous microfossils resemble plant stones, so-called
phytoliths, tiny silica bodies of various shape and size that are incorporated as structural elements in
the roots, stems, and leafs of modern plants. Major plant groups like the gymnosperms, lycopods and
ferns existed already by the end of the Devonian which might imply that these early land plants have
also formed phytoliths in their tissues. The here reported BSPs constitute only the second evidence of
phytolith-like siliceous microfossils from the Paleozoic. The newly extracted microfossils may provide a
tool for subdividing and correlating Rotliegend rock successions. In order to test this hypothesis, Permo
-Carboniferous rocks from various wells in the Netherlands were studied. Biogenic silica particles
(BSPs) could be extracted from all studied wells and lithostratigraphic units.
However, the total BSP abundance in the single samples considerably varies. A total of 22 BSPs with
significant morphological differences could be hitherto identified. BSP assemblages in the Rotliegend
are currently examined to determine how they can provide information on stratigraphy. The examined
BSP-based biostratigraphic approaches include first and last occurrence dates and variability in the
down-core abundance patterns. If the stratigraphic importance of BSPs could be confirmed in the
ongoing studies, BSPs will provide a new tool for subdividing and correlating the mostly barren
Rotliegend sequences.
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Application of Soft Computing in Lithology Prediction: A Case Study from Marun Field
Authors Sayyid Reza Asadullahpour and Bahram HabibniaThis paper focuses on prediction of lithology, especially shale intervals. Shale is very significant in
zonation, layering, formation damage and well logs. Neural clustering network (NCN), neural patternrecognition
network (NPRN), feed-forward back-propagation network (FBN), fuzzy clustering means
(FCM) and adaptive neuro-fuzzy inference system (ANFIS) are used. They are tried on three wells in
carbonate reservoirs of Marun field, however results are discussed for Well # 222 with 811 utilized
data of raw log reading.
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Correlation and Integration of Seismic Velocities, Rock Properties, and Pore Structure in from Outcrop of Wasia Group Rocks in the U.a.E
An earlier geological and petrophysical investigation of the Lower Cretaceous, Wasia Group in the UAE
found potential correlations between seismic velocities (Vp and Vs) and fracture density, except for a
group of rock samples that deviates from the general trends. The aim of this study is to better
understand the previous results to improve characterization and correlation of the geology and rock
properties of the exposed rock.
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Integrated Geophysical Investigation of Al Hiyar Area, Eastern Abu Dhabi: Implications for Structure of the Frontal Fold Belts of Oman Mountains
Authors Saif A. Al Mesaabi, Ammar H. El Husseiny, Ahmed A. Hassan and Mohamed AliGravity, magnetic and seismic surveys were conducted in Al Hiyar area, eastern Abu Dhabi, located on
the border between the United Arab Emirates (UAE) and Oman on the western edge of the northern
Oman mountains as part of a study to determine the subsurface structures and sedimentary sequences
of the area. The interpretation of these new data was integrated with a new interpretation of
reprocessed commercial seismic reflection profiles recorded close to the area.
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Structural and Tectonic History of the Sedimentary Basin in Northern Iraq and the Kurdistan Region
More LessThe aim of this study is to address the main aspects of the structural and tectonic evolution of the
sedimentary basin in northern Iraq and identifies all the sedimentary cycles in details from the Late
Triassic period to Pliocene.
The second part tackles the Geohistory modelling of all the encountered source rocks in the basin and
evaluates their maturation history and expulsion of hydrocarbons.
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Challenges Associated with Exploring the Cretaceous Rudist Basin-Margin Buildups of the Arabian Basin
More LessRudist buildups were described from many horizons within the Cretaceous strata of the Arabian Basin.
The most prominent among these were described from the Shuiaba Formation (Aptian) in the major
oilfields of the Arabian Gulf region. They were documented also from the Mauddud Formation (Aptian)
in the eastern offshore areas of Saudi Arabia and southeast Iraq and from the Mishrif Formation
(Albian-Cenomanian) in the southern Arabian Gulf and southern Iraq (e.g. Majnoon field). More varied
buildups were found in the Upper Cretaceous carbonates of the Simsima Formation (Maastrichtian) in
Oman and the UAE, the Hartha Formation (Campanian) in central and west Iraq and from Wadi Sir
Formation (Turonian) in Jordan.
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North Oman Fault Geometries in Outcrops, Analogues and Sub-Surface
Authors Pascal D. Richard and Mohammed Al-KindyNorth Oman offers a rare opportunity for making outcrop observations of faults developed in
formations that are also the producing reservoirs in the sub-surface. It is possible to look in great
detail at fault geometries and associated fault damage zones, both in map view and cross sections.
From these observations it is possible to establish the geometrical rules that will help to build static
models and interpret faults on seismic. It is also possible to illustrate the impact of the simplifications
which are inherent to the static modelling process and assess whether they are acceptable or not to
define the most suitable modelling strategy.
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Spatially Enabled Decision-Making with GEMS Using the First Integrated Data Model
More LessGEMS/Fastrack is an application used by prospect evaluators and portfolio analysts to assess the
volumetric potential of subsurface resources and to manage their portfolios.
The HC volumes calculated in Fastrack are used to report udSFR and dSFR volumes (undiscovered- and
discovered Scope-For-Recovery, respectively) and Business Case volumes, the latter being an
important prospect-ranking criterion to determine which prospects will be matured.
All computation results are stored in an Oracle database that makes use of an integrated data model
meaning that the same database holds the coordinates of the target and prospect outlines as well as
the non-spatial data, i.e. all other data. The integrated data model imposes a common key between
the spatial and non-spatial data. This enables easy checking of consistency between the spatial and
non-spatial data and allows for spatial querying of the database through a Geographical Information
System (GIS). Apart from volumes, reservoir input parameters such as GOC, OWC, GWC and length of
oil and/or gas column are also available. These parameters are not only used to rank the prospects but
also to quality control the data.
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3D Microanalysis of Geological Samples with Nanofocus Computed Tomography
Authors Gerhard Zacher, Jens Lübbehüsen, Oliver Brunke and Thomas MayerDuring the last decade, Computed Tomography (CT) has progressed to higher resolution and faster
reconstruction of the 3D-volume. Most recently it even allows a three-dimensional look inside of
geological samples with submicron resolution. This allows sophisticated analysis of hydraulic
parameters like porosity and permeability or volumetric information about distribution and quantitative
content of specific minerals providing important information for petrophysicists.
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Remote Sensing-in-Aid to Geo-Scientists
Authors Siddiq H. Al Balushi, Issa S. Quseimi and Ahmed S. TabookOver the years the use of Remote Sensing (RS) in Petroleum Development Oman (PDO) has evolved
from being seen as providing general surface information images for seismic and engineering planning
activities to an essential and cost effective tool to support many other added value E&P activities. With
the increase in the number of Satellites and their spatial resolution and different type of sensors;
accurate and detailed images can be acquired at a lower cost; this opened up new applications for Oil
industries including high accuracy surface deformation monitoring. Satellite images /data and Aerial
photos are used to provide overview of the regional geological setting, pre-and post plan 2D and 3D
seismic surveys, engineering construction activities, selection of exploration well sites, monitoring
environmental impact and pipeline transfer of hydrocarbons.
This paper demonstrate the varied application used in oil and gas activities including Surface
Deformation Monitoring and Enhanced Oil Recovery (EOR) projects in support of reservoir surveillance
and geological modelling.
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Fast Appraisal and Maturation of Heterogeneous Carbonate Fields in a Shuaiba Stratigraphic Play, North Oman
We present two case studies discussing the synergy between appraisal and maturation activities of a
heterogeneous carbonate play in North Oman. Key aspects are the effects of the complex geology on
how quickly new fields can be brought on stream after discovery.
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Variations in Formation Water Salinity and Its Bearing from Oil API in a Shallow Heavy Oil Bearing Sandstone Reservoir in Ratqa Field, North Kuwait
Authors Kawthar I. Sultan, Arshad Aziz, Sawsan Al-Zanki and Abdul Ridha Al-AshwakThe extensively drilled, Lower Fars Formation of Miocene age, hosting heavy oil in the Ratqa Field of
North Kuwait, comprises alternations of fluvial to estuarine channel sands and associated overbank
shales, ranging in depth from 260 feet in the South to 550 feet in the North, capped by a shale,
considered the regional top seal. The formation thickness ranges from 750 feet in the South to 900
feet in the North. The sands are disposed along a relatively gently sloping SW-NE structural monocline,
without any observable structural or stratigraphic entrapment. Large variations in formation water
salinities have been observed from well testing and from log derived estimations. Presence of very low
salinity water at shallow depths of 200-300 feet and enormous increase in the salinity with depth, at
places, indicates possible contamination of formation water having over 100,000 ppm as NaCl
concentration, with a relatively fresh water.
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Detailed Compositional Modeling of Gas Injection Pilot in Giant Carbonate Reservoir in the Middle-East
Authors Tawfiq A. Obeida, Adrian Gibson, Bikram Baruah and Hussain Al HashemiThe objective of this paper is to address the main challenges that have been encountered in the
simulation study when using local grid refine (LGR) within upscaled models. The challenges are mainly
due to the unreliability of populating the fine grids with reservoir properties and attributes.
Dynamic modeling of a pilot is an important task to predict fluid flow and reservoir behavior which is a
major step of pilot design. Dynamic models usually have many limitations when it comes to geological
description due to upscaling of fine-grid static model.
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Sea-Level and Paleoproductivity Changes Recorded in Early Paleogene Deposits in Jordan: Events for Regional Correlation
Authors Elisa Guasti and Oscar A. AbbinkThe importance of hydrocarbon in the Middle East is well known. However there are still areas where
the exploration potential is not fully developed yet, such as in Jordan.
The Paleocene-Eocene depositional record in the Middle East and North Africa is dominated by
hemipelagic marls that form important seals for petroleum accumulations in certain areas, and by
shallow water limestones which represent good reservoirs, such as the Wafra field between Kuwait and
Saudi Arabia.
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Characterization of the Hercynian Unconformity, for Prospect Evaluation, Saudi Arabia
Authors Sulaiman L. Al-Sulami and Mohammed AmeenThe Hercynian unconformity in the Arabian plate (Late Devonian to Early Carboniferous) impacts the
hydrocarbon resources and therefore is an essential aspect of prospect evaluation and field
development. We conducted a regional characterization of the unconformity using an integrated,
multidisciplinary method, including borehole images, dipmeters, open-hole logs, cores, seismic data,
VSP, inorganic geochemistry and palynology. The study included 13 key wells with over 14,000 ft of
borehole images (across the unconformity) and several hundred Km of seismic sections across key
prospects and traps.
The study shows the unconformity is manifested in distinct modes in terms of:
1. Unconformity facies: including conglomerate/breccia, paleosols, and disturbed zones due to soft
sediments deformation.
2. Angular discordance: including change in dip azimuth, or dip angle, or both.
3. Occurrence of tectonic faults.
The above aspects of unconformity modes offer different hydrocarbon configurations. These include
positive configurations that facilitate a sealing effect, potential reservoirs, or potential paths for
hydrocarbon migration. In addition they include negative configurations that result in losses of
potential resources, through weathering and erosion, of potential source rocks and reservoir rocks.
Case studies of these configurations from mainland Saudi Arabia are presented and discussed in this paper.
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Jurassic and Cretaceous Carbonate Geology and Stratigraphic Plays in the Rub’Al Khali Basin, Kingdom of Saudi Arabia
Authors Craig Harvey, Abdul-Hameed Azzouni and Henk DrosteThe South Rub ‘al Khali Company Ltd is an Incorporated Joint Venture between Shell Saudi Ventures
Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for nonassociated
gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of Saudi Arabia.
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Sweet Success in Sour Arab Reservoirs - How Successful Coring Improved Data Integration
Authors Andreas Briner, Abdul-Hameed Azzouni, Conxita Taberner and Brent WignallThe South Rub' al Khali Company Ltd. (SRAK) is an Incorporated Joint Venture between Shell and
Saudi Aramco and is engaged in exploring for non-associated gas and liquids in parts of the South Rub'
al Khali Basin. The licence area contains significant quantities of ultra-sour gas in the Jurassic Arab Formation reservoir.
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The Role of Non-Seismic Methods in ear-Surface Solutions: Applications of Seismic-Gravity Joint Inversion and Redatuming in South Rub Al-Khali, Saudi Arabia
Onshore seismic data from the Middle East are adversely affected by near surface and intermediate
depth velocity anomalies. The correct estimate of the near-surface velocity field is fundamental to
obtain reliable seismic images. Conventional velocity model building workflows based on refracted
arrivals (i.e. First Breaks - FB) fail to appropriately reconstruct the shallow velocity complexities in the
presence of large velocity inversions, sharp lateral velocity changes and noisy FB. In such cases, the
integration of seismic with additional geophysical measurements (i.e. gravity-EM) can solve the shallow
velocity modeling problem. Simultaneous Joint Inversion (JI) is an elegant and analytic method to
address geophysical data integration. It is implemented in this paper for velocity model building in
South Rub Al-Khali by taking advantage of the availability of high-resolution gravity data coincident
with the seismic acquisition. The analyzed 2D seismic lines are sampling different near-surface geologic
conditions such as dunes, sub-cropping carbonates and karsts. This corresponds to various degrees of
complexity in the near surface velocity field and related distortions introduced in the seismic image
when a conventional “statics” approach is used. An alternative approach to statics solutions is then
explored by simultaneous JI of FB and gravity data residuals for the shallow velocity and density fields.
Pre-stack wave-equation redatuming (WED) is then used to model and remove the effects of complex
velocity patterns from the seismic data. Various degrees of improvement are obtained with the
discussed workflow depending on the severity of the near-surface velocity complexities and shallow
geologic conditions. The analysis of the results allows to identify specific roles for non-seismic methods
for the solution of near surface problems in land seismic data processing.
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Paleozoic Clastic Systems, Reservoir Quality, and Play Mapping in the Rub’ Al Khali Basin, Kingdom of Saudi Arabia
Authors Michael Hulver, Abdul-Hameed Azzouni and Craig HarveyThe South Rub ‘al Khali Company Ltd (SRAK) is an Incorporated Joint Venture between Shell Saudi
Ventures Limited (50%) and Saudi Arabian Oil Company (50%), and was set up in order to explore for
non-associated gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom
of Saudi Arabia.
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Joining the Dots: Cretaceous Prospectivity in the South Rub ‘Al Khali Basin, Saudi Arabia
Authors Michael Moir, Henk Droste, Craig Harvey and Andrew WeedonThe South Rub ‘al Khali Company Ltd is an Incorporated Joint Venture between Shell Saudi Ventures
Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for nonassociated
gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of Saudi Arabia.
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Listening to the Right Thing: The Integration of Low Frequency Seismic Data with Other Geophysical Methods as a Frontier Exploration Tool in the South Rub ‘Al Khali Basin
Authors Colin Nunweek, Michael Hulver and Pieter van MastrigtThe South Rub ‘al Khali Company Ltd is an Incorporated Joint Venture between Shell Saudi Ventures
Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for nonassociated
gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of
Saudi Arabia.
Following an initial three well exploration drilling campaign in SRAK’s Contract Area 2 (CA2), SRAK
embarked on a second major phase of 2D seismic acquisition. Low frequency seismic data has been
acquired on all new 2D seismic lines via an embedded recording set-up. This has resulted in the largest
combined PSTM / LF exploration data sets acquired to date.
One of the key challenges facing low frequency seismic as an effective exploration tool is the lack of
signal depth discrimination. This presentation will focus on the combination of low frequency seismic
with conventional seismic products in order to constrain the depth of the low frequency signal and how
combining these workflows with geologic models has led to the identification of a potentially new
hydrocarbon play in the southern Rub ‘al Khali Basin.
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Where Is My Sand Wedge? Part 1: Exploring for Stratigraphic Trapping Potential in the Unayzah Group, South Rub' Al Khali Basin
Authors Geoff Pike, Craig Harvey, Michael Hulver, Ashraf Khalil and Pieter van MastrigtThe South Rub ‘al Khali Company Ltd is an Incorporated Joint Venture between Shell Saudi Ventures
Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for nonassociated
gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of
Saudi Arabia.
To date exploration for a working Palaeozoic petroleum system has proven reservoir in 4-way
structural dip closure and the presence of mature source rock. The search for gas is focused on the
subtle, off-structure stratigraphic potential of the Unayzah Group, and in particular the Nuayyim
Formation and/or Jawb Member sandstones.
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Where Is My Sand Wedge? Part 2: Lessons from Srak’S First Stratigraphic Trap Test in the South Rub' Al Khali Basin
Authors Geoff Pike, Craig Harvey, Michael Hulver, Ashraf Khalil and Pieter van MastrigtThe South Rub ‘al Khali Company Ltd is an Incorporated Joint Venture between Shell Saudi Ventures
Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for nonassociated
gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of Saudi Arabia.
SRAK’s Unayzah Stratigraphic Play exploration has resulted in the identification, de-risking and drilling
of a number of stratigraphic traps in the South Rub Al-Khali Basin. Such traps rely on Nuayyim
Formation (Unayzah A Reservoir Unit) and Jawb Member (Unayzah B Reservoir Unit) targets that
developed preferentially off-structure. Exploration for these stratigraphic traps is generally difficult as
even good quality 3D seismic data cannot resolve subtle facies changes and faults that may be
fundamental trapping components. On 2D seismic, such problems are enhanced and exploration
therefore relies much more heavily on good geological models coupled with geophysical or geochemical
direct hydrocarbon indicators (DHI’s). SRAK tested the largest known stratigraphic trap in its acreage
with its sixth well. Critical to the evaluation and de-risking were a sound geological model from
analogues in the Saudi Aramco Reserved Area, an up-dip calibration well and a world class, 600 km
low frequency seismic (LF) dataset to de-risk the trap.
The presentation will discuss the lessons from the current drilling campaign including an update to the
geological model for the Unayzah Group for the southern Rub ‘al Khali Basin. The application of low
frequency seismic techniques to de-risking has been tested by the drill-bit for both conventional and
unconventional traps and this new technology will be discussed.
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“Brighter than the Moon” - Illuminating the Hydrocarbon Prospectivity in the South Rub' Al Khali Basin
More LessThe South Rub Al-Khali Company Ltd is an Incorporated Joint Venture between Shell Saudi Ventures
Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for nonassociated
gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of Saudi Arabia.
In order to achieve its objectives within the timeframe of the First Exploration Period, a play-based
rather than prospect-based exploration strategy had been devised during the start-up of the Venture to
maximise the chances of identifying working hydrocarbon systems and to optimally position the
Company for a Second Exploration Period.
This encompassed a two pronged approach pursuing pre-Khuff Formation sweet gas prospectivity in
SRAK’s Contract Area 2 in Southwest Saudi Arabia and Khuff and Arab Formation sour gas
prospectivity in SRAK’s Contract Area 1 in Southeast Saudi Arabia. A concerted Technology effort was
made to help polarize drilling opportunities.
As SRAK’s First Exploration Period is drawing to a close in mid-2010, this paper will summarise the
exploration results, review how the exploration strategy evolved through time in response to early
exploration results and distill learnings applicable to similar frontier exploration ventures elsewhere.
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West Esh El Mallaha Concession Fields, Pre- and Syn-Rift Multi-Oil-Bearing Reservoirs as a Structural and Stratigraphic Model in the Eastern Desert Onshore Southern Gulf of Suez Rift Province, Egypt
More LessThe Gulf of Suez is a failed extensional rift basin. Rifting initiated during Early Miocene time and
reached its peak at the end of Burdigalian. Three major fault trends are observed in the Gulf of Suez;
rift parallel or clysmic. North oblique and rift orthogonal cross elements. The Gulf of Suez rift is divided
into three dip provinces separated by two transfer zones. Each dip province has its own geologic
characteristics which makes the hydrocarbon trapping mechanisms are different from one province to
another. The southern province is dominated by SW dipping pre-rift sequences and characterized from
the central and northern parts by more severe extension, faults are more frequent, smaller structural
block size, thicker sand reservoir accumulations during in the Miocene syn-rift sequences, thinner prerift
sequences and well developed Miocene salt diapers. As a result, the southern GOS province is more
favorable for Miocene and Pre-Miocene (including the Basement rocks) hydrocarbon traps. West Esh El
Mallaha concession has oil production from three separate structural closures (Tanan-Tawoos, Rabeh
and East Rabeh). Its total area is 52 km square with 45 wells have been drilled in the concession.
The structural style of West Esh El Mallaha fields are dominated by tilted fault blocks bounded by NWSE
oriented normal, down to the northeast faults and dissected by oblique and orthogonal faults.
Reservoirs range in age from Cretaceous to Miocene.
The first commercial hydrocarbon in West Esh El Mallaha concession was discovered by Coplex in 1997
from Rabeh field. The discovered oil was placed on production on February 1998. Currently, the West
Esh El Mallaha concession fields are operating by LUKOIL/ESHPETCO joint venture company. The
concession cumulative oil production as of June, 2009 is 27.5 MMB, of which 90% is produced from Pre
-Miocene Nubia and Matulla Fms and the remaining 10% from the Miocene reservoirs Nukhul and Rudeis.
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Sequence Stratigraphic Analysis of the Ratawi Shale Formation: Implications for Reservoir Distribution and Exploration Potential in Kuwait
Authors Saifullah K.Tanoli and Mohammad Dawwas Al-AjmiThe Ratawi Shale Formation is first Cretaceous dominantly clastic unit which overlies a thick carbonate
succession in Kuwait. The formation is divisible into three informal zones; the lower one consisting of
mainly shale with limestone interbeds. This part was deposited under transgressive conditions in
shallow marine to offshore environments. An MFS is recognized near the top of this zone which follows
a variable thickness, usually thin, highstand interval due to incision during the overlying lowstand. The
middle zone of the formation consists of better sandstone facies. It was deposited in fluvial to estuarine
environments representing sedimentation in incised valleys in western part and in nearshore to shallow
marine environments eastward. This zone makes the lowstand deposition and completes one 3rd order
cycle of deposition. The overlying upper zone consists of shale with local thin sandstone, siltstone and
limestone interbeds and is interpreted as deposited under transgressive conditions with or without a
recognizable highstand before its termination by the overlying Pre-Zubair late Valanginian unconformity.
High frequency sequences and important related surfaces such as regressive surface of marine erosion
(RSME), subaerial unconformity (SU) or subaerial exposure surface (SES), subaerial erosion surface
(SERS), shoreline ravinement (SR) or transgressive surface (TS), flooding surface (FS) and possible
existence of basal surface of forced regression (BSFR) were identified and described from the cores.
The RSME is usually sharp and wavy separating the underlying offshore muddier facies from the
overlying shoreface sandier facies. The sequence boundary is marked by exposed surface locally
represented by rooted interfluves and in other areas by the weathered horizons and still in others by
incised fluvial surface. The transgressive surface or shoreline ravinement in one case lies at the base of
tidally influenced channel but usually makes a thin burrowed horizon with the fining and deepening
upward trend. The reservoir facies are variably associated with the falling stage systems tract (e.g.
shoreface sandstone above the RSME), with the lowstand systems tract (e.g. fluvial to estuarine
sandstones) and locally with the transgressive systems tract (e.g. tidal channel above SR). An insight
of the sequence stratigraphic set up along with paleoenvironmental regime is crucial for identification
and distribution of reservoir facies in this formation.
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Early and Charge Related Diagenetic Controls from Rock Types (Arab C and D Reservoirs, South Rub' Al Khali Basin, Saudi Arabia)
The South Rub ‘al Khali Company Ltd (SRAK) is an Incorporated Joint Venture between Shell Saudi
Ventures Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for
non-associated gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of Saudi Arabia.
The Arab C and D reservoirs in the Kidan Field of the South Rub ’al Khali Basin have recently been the
targets of a well drilled by the SRAK Venture. A total of 350 ft continuous core was obtained to
characterize reservoir properties and interpret key processes controlling their distribution across the
field. Depositional environments and early diagenetic patterns provided the template for burial and
charge-related modification of rock properties. Distinct reservoir rock types have been differentiated
based on petrographic observations, core porosity, core permeability and MICP (mercury injection
capillary pressure) data.
This presentation focuses on the results of the detailed diagenetic and geochemical study that allows
the interpretation of the key processes controlling the differentiated rock types in Arab C dolostone
units and Arab D ooid grainstone units. Dolostone reservoir properties in the Arab C are mainly
controlled by the presence/absence of late calcite and / or late anhydrite plugging of intercrystalline
porosity. The key diagenetic processes recorded in rock types from Arab D grainstones are: early
cementation, compaction, burial cementation (including calcite, fluorite and anhydrite), late leaching
and late charge-related cementation (calcite and saddle dolomite).
The rock types are mostly stratigraphically defined units, in spite of the recorded complexity of
diagenetic processes, associated diagenetic products and pore size distributions. The stratigraphic
arrangement of the rock types in the studied core responds to depositional and early diagenetic
controls. The late diagenetic products follow the early diagenetic template, nevertheless understanding
the impact of late diagenesis has proven key to predict the rock properties across the field and
construct new reservoir models.
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Wavelet Consistency Assessment for Quantitative Interpretation - A Case Study from Northeastern Saudi Arabia
Authors Ming-Ren Hong, Mohammed Alfaraj, Jinsong Wang and James RiceAn onshore exploration 3D survey located in Northeastern Saudi Arabia and covering an area of
approximately 6300 square kilometers was acquired in 2003. There are two existing oil fields with
Upper Jurassic, carbonate reservoirs controlled by four-way closures, located within the survey.
Current exploration activity, away from these fields, is concentrating on stratigraphic plays involving up
-dip truncation of regional trends with the hydrocarbon seals being created by dolomitization and
cementation within the reservoir.
A multi-well feasibility study confirmed that porosity changes within the reservoir at these seal
boundaries could be seen using acoustic impedance inversion. One important question on the use of
seismic inversion over this large of an area was the wavelet stability. The inversion software used in
the project employed a multi-well, multi-trace approach that allowed for very detailed, thorough and
semi-automated procedures for conducting a wavelet study.
This paper will present the results from wavelet stability tests including analysis of seismic data only by
means of a Markov chain Monte Carlo (MCMC) simulation technique. This is followed by scenarios with
different combinations of single and multiple wells and seismic data, with varying number of traces
around each well used in the calibration and wavelet extraction. The final wavelet determined in the
inversion analysis was then cross-checked among the various techniques. This thorough procedure
confirmed that the wavelet was zero phase and SEG negative polarity, and that it was reasonably
stable throughout the survey.
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Shaybah 3D Amplitude Inversion with Interbed Multiple Modeling
Authors Ming-Ren Hong, Harun Mohd Noor and Mahmoud HedefaAmplitude inversion has been used routinely throughout the industry to help assess the reservoir
quality and derive reservoir properties such as porosity. In cases where interbed multiple
contaminations interfere with the primary reflectivity, the inversion results are questionable unless
interbed multiples can be simulated in the inversion procedure.
In this paper, we demonstrate the use of zero-offset modeling, to simulate interbed multiples,
observed in a 3D seismic dataset, acquired over the Shaybah oil field. We identified the interval from
which interbed multiples were generated and produced a reasonable 3D impedance model for use in
the field’s development drilling program.
A “layer-stripping” type modeling approach was used to identify the interval from which the interbed
multiples were generated. Three key geologic intervals between the surface and the base of the
reservoir were identified as candidates for the starting layer from which the interbed multiples were
modeled. To begin, the shallowest formation of the three was designated as the starting layer.
Synthetic traces with primary and interbed multiple reflections were generated and compared with the
measured seismic data. This procedure was repeated for the deeper two consecutive formations. At the
conclusion of this modeling exercise, it was determined that using the shallowest formation as the
starting layer produced the best match between the synthetic and measured seismic data.
The inversion algorithm used a model-based method where the starting model was generated by
interpolating known log impedances between existing well control based on the interpreted seismic
time horizons. The initial model was then optimized by iteratively updating the impedance to minimize
the error between the synthetic, generated from the model, and the seismic. The final inversion results
were evaluated by matching the measured 3D seismic data to the impedance logs at the wells.
Comparison of seismic and inverted impedance volumes showed that the top of the reservoir was more
clearly defined by the impedance volume; whereas the 3D seismic signature for the top of the reservoir
is poorly defined due to the presence of the multiple interference.
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Exploration Campaign Drilling for Low-Relief Channel-Sand Prospects, South Central Oman
Authors Recep A. Kazdal, Cees van Eden and Lanette MarchaDuring 2009/10, PDO Exploration is executing a ‘peephole’ exploration/appraisal campaign for 2
prospects in the vicinity of a field which was developed using several grid drilling campaigns since
1990. The Field, discovered in 1986, is a low relief anticline (approximately 45m relief and 100 km2
closure) located in central Oman. The oil is produced from the Permian Upper Gharif channel sands,
deposited within a predominantly muddy floodplain and hence with a relatively low net/gross of some
30%. The oil is 24o API with a viscosity of 45cP. Experience, gained during the appraisal and early
development stages of the field, is being brought to bear on the exploration and appraisal of its
satellites. The initial field development was based on the drilling of high-angle, deviated wells aimed at
maximising the chance of finding the fluvial channels. This achieved a low rate of success at a high
drilling cost. A new strategy of drilling multiple, low-cost, vertical wells (peepholes) was implemented.
The economics of this campaign drilling could tolerate the expected low success rate, eventually
improving understanding of the reservoir distribution patterns and reducing uncertainty in targeting
productive sands. The first peephole campaign in the field started in 2001. Twenty wells were drilled
with a success rate of 60%. The ensuing second campaign drilled another 12 wells with a success rate
of 66 %. Both campaigns resulted in a substantial production increase and met both the economic and
geological success criteria. Using this field development as an analogue, 12 wells have been
incorporated on the Exploration drilling sequence to appraise the first satellite prospect. A further 10
wells are planned on a second prospect in 2010. This paper will share the results and learnings of the
first drilling campaign. The first campaign well proved an oil bearing zone with a much higher net/gross
than the historical exploration well.
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Utilising New GIS Tools in Petroleum Exploration and Production
Authors Joerg Mattner and Rajasekar GanesanChallenges for the petroleum industry increase continuously; the “easy” reservoirs have been
discovered and are produced today. New technologies and increasing sophistication, both in the data
display, evaluation and interpretation are utilised to home in on new prospects and increased production.
We show petroleum geoscience studies in which GIS was fundamental in bringing together varied data
sets on multiple scales to accomplish an integrated and result oriented analysis. New tools allow
geoscientists who are not GIS experts to efficiently analyse and interpret a wide range of data e.g. well
data, present-day and paleo-fault leakage and cross-flow probability, reservoir compartmentalisation,
fracture sweet spots, facies distribution and depositional direction. Regional paleo-stress and structural
maps are used to guide and constrain these interpretations.
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Hydrocarbon Charge and Reservoir Pressure History of the Carbonate Stringer Play in South Oman - Implications for Pre-Drill Pore Pressure Risking
Authors Paul N. Taylor, Afifa Al Harrasi, Cees van Eden and Mohammed Al GhammariThe Ara Stringer Play in the South Oman Salt Basin contains sour oil and gas fields reservoired in
carbonate slabs encased within salt. Hydrocarbons occur in a depth range of 2.5 km to 5.5 km with
reservoir pressures ranging from hydrostatic (10-11 kPa/m) to near-lithostatic (22 kPa/m) gradients.
Similarly, in-situ hydrocarbon fluid densities vary widely, from 3 kPa/m to 8 kPa/m. Such variability in
reservoir pressure and fluid density present a challenge for the design of safe and cost-effective drilling
and completion strategies. Of particular concern is the combination of dry gas and hard overpressure,
which could lead to well head pressures of up to 100 MPa (14,500 psi) at 5km. To address this
uncertainty we have completed an integration of reservoir pressure data, seismic data, fluid PVT data
and geochemical data to allow the construction of a model for the risking of likely pressure regime and
hydrocarbon fluid types pre-drill.
Previous work has shown that stringers which have pore pressures close to a hydrostatic gradient
today, should have been highly overpressured prior to a “deflation” event in the geologic past. Our
observations on the hydrocarbon fluid characteristics support a scenario in which gas-condensate
accumulations have originated from a palaeo oil phase within overpressured reservoirs. These oil
accumulations were subsequently depressurised to allow separation and segregation of a gas phase.
In the event that a “deflated” stringer is re-pressurised due to further burial, the saturation pressure of
the mixture will be exceeded once again and the two-phase accumulation will revert back to a single
phase oil column. Therefore highly overpressured gas reservoirs are only expected when the oil and
gas phases are physically isolated prior to re-burial. Structural separation of the oil and gas legs of a
palaeo-accumulation in the Ara Stringer Play has been observed.
The consequence of a phase separation / segregation model of gas occurrence is that the density of
the segregated gas-condensate fluid is dependent upon the reservoir pressure (depth) at the time of
deflation to hydrostatic conditions. There is, therefore, a strong depth dependency to the predicted
fluid character, with in-situ density increasing with depth. This knowledge can be used to optimise
engineering decisions, rather than relying on the “worst-case scenario” of lowest density fluid
properties and highest reservoir pressures observed within the play.
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Offshore Cyprus - A Future Hydrocarbon Player
By Per H. SembOffshore Cyprus, located in the eastern Mediterranean close to the already proven hydrocarbon
provinces offshore Egypt and Israel covers a huge unexplored area. This area has recently drawn a lot
of attention from the oil and gas industry after arranging its first license round in 2007 and from the
news of the very encouraging lower Miocene gas discoveries in offshore Israel.
The Cyprus Ministry recently announced they are ready to launch its 2nd license round around Q4 ’09 -
Q1 ’10 after completion of the first round which resulted in award of one block to the American
company Noble Energy Inc. In the 2nd round all open blocks will be offered, in total 12 blocks, each
with size of 4-6000 sq km which sums up to more than 70,000 sq km of unexplored acreage.
The offshore blocks are covered by more than 19,000 line km of newly acquired 2D seismic and 750 sq
km 3D seismic data. About 12,500 line km of the 2D data was acquired in 2008/2009 with a dual
sensor streamer technology which especially enhances the lower frequencies (also enhancing the
higher frequencies) which is crucial for penetration and imaging of the pre Messinian structures. The
recent acquired 2D seismic reveals a full set of new potential plays offshore Cyprus. In the thick pre
Messinian sediment package in the Levant basin a lot more details are seen and more of the deeper
low frequent structures are reveled giving a better understanding of the potential plays. The enormous
Eratosthenes structure located south of Cyprus which origin has been subject to a lot of discussion is
now revealing a lot more of its structural elements, supporting the idea of the structure as a potential
hydrocarbon source/reservoir. The western offshore and the Herodotus Basin is in general complex
with a lot of thrusting and faulting were several big 4-way closure structures have been identified
together with a set of interesting pre Missinian fault blocks. Several hydrocarbon indicators as flat
spots, amplitude anomalies and gas chimneys identified both in the pre and post Messinian sediments
further enhance the hydrocarbon potential in offshore Cyprus.
Based on the promising structures and elements identified in the seismic data and the recent Dalit and
Tamar discoveries (0.5 and 5Tcf of gas) in offshore Israel, offshore Cyprus is expected to receive a lot
of attention from the oil and gas industry with regards to the second license round and will be an
important player in the future search for hydrocarbons.
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Tectonic Escape (Indentation) in Central Saudi Arabia, Possibility and Exploration Potential
Authors Mesbah H. Khalil, Muzaiyen E. Muzaiyen, Khalid M. Hmoud and Luay B. IsmailTectonic analysis indicates a high possibility of tectonic escape structures in central Saudi Arabia which
could bear significant hydrocarbon exploration potential. This study aims to introduce a new tectonic
model that explains several surface and subsurface newly mapped structures in central Saudi Arabia.
Potential fields, seismic and surface geology data are integrated to accomplish this study.
Basement terrane analysis of the Arabian shield and its eastern continuation beneath the sedimentary
basin indicates the general north-south orientation with differences in width and composition. It shows
that the maximum crust thickness is in the middle of the outcroping shield with a promontory
extending 200km toward east in subsurface (Central Arabian Arch) where Triassic (Khuff) marine
carbonates overlay the basement directly. The crust shows gradual thinning eastward from this
promontory till the offshore Arabian Gulf. Some terranes show wedging-out and others show narrowing
against the eastern side of the basement outcrops. This pattern suggests the tectonic escape of the
wedging out and narrowing terranes against the competent Afif terrane since the InfraCambrian
accretion of Arabia. The terrane accretion occurred by westerly driven terranes collided against the
thick promontory of the Afif terrane causing dispersion toward south and north through east-west
accommodation zones. Long segments of unusual east-west surface structures (faults and strike of
strata) over the boundaries of the subsurface basement promontory from north and south are thought
to be a dragging of the dispersed terrane fragments at the promontory boundaries. West of these eastwest
zones, deformation is concentrated at the north-south terranes with curved hard link transfer
zones. This InfraCambrian tectonic setting is believed to have been reactivated during Phanerozoic
tectonic phases to express its escape tectonics pattern further-up till outcrops. Re-distribution of the
Phanerozoic stresses at that inherited basement fabric controlled the geometry of the sub-basins and
their filling during extension phases. It controlled also the preferable locations of structural positive
inversion during compression phases to form the fault related fold traps. This approach explains the
diversity of structural styles in the sedimentary cover (compression, transpression, and transtension)
which formed simultaneously during Late Cretaceous compression but with different directions.
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Dual Sensor Seismic Examples from Around the Middle East
Authors Mark Spencer-Jones and Per H. SembNew dual-sensor streamer 2D data have been compared to legacy conventional streamer data
throughout the Middle East (Cyprus, Egypt, Lebanon, Libya, and Saudi Arabia) to analyze the
differences and quantify the improvements in seismic resolution. A comparison of PSTM stacks after
processing through the same flow of the vintage hydrophone data and the up-going pressure field (Pup)
showed in general a higher signal-to-noise ratio and better resolution of the P-up image. Spectral
analyses quantified the amplitude versus frequency level and showed a significant increase of low and
high frequencies. The low frequency enhancement was particularly significant deeper in the sections
with spectacular penetration below the highly reflective Messinian Salt/Mansiyah Formation layers.
The dual-sensor streamer measures the pressure wave field using hydrophones and simultaneously the
vertical component of the particle velocity using motion sensors, overcoming the limitations of
hydrophone-only acquisition systems. Its unique ability to de-ghost signals and to optimize data
quality, not just for one target depth, but for all depths shallow to deep, promises to significantly
improve our customer’s exploration success ratio, well targeting and recovery efficiency. Besides data
quality improvements, the streamer is operationally efficient because it records in one pass, with one
streamer depth, in seas no other system can handle. The technical benefits of this step change are
seen in three key areas: - Enhanced resolution of the final seismic image - Better penetration revealing
deeper targets - Improved operational efficiency. The first two points result from the increased
bandwidth at both low and high frequencies due to removal of the receiver ghost. The third point
results from the ability to tow deeper, which is operationally attractive as weather and operational
noise are minimal and the streamers are better behaved.
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Considerations for Cableless System Development and Deployment on High Production Vibroseis Operations
Authors Robert G. Heath, John Giles and Vlad MayerNext generation cableless land acquisition systems are now in use on seismic crews in various
countries. Such recorders overcome many of the perceived shortcomings of earlier devices which may
have limited uptake for certain applications.
These new systems are characterised by improved levels of source control integration, a wider variety
of remote unit timing capabilities, abilities to perform remote control of ground stations as well as data
QC/status return, and much improved data harvesting techniques.
This paper reviews these newest source control and recorder technologies, and describes how both
passive and active acquisition in Middle East environments can benefit.
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New Insights from Hydrocarbon Prospectivity - Moroccan and Nova Scotian Conjugate Margins
Authors Hamish Wilson and Matt LuheshiEmerging plays in Brazil, Ghana and Morocco have triggered interest in searching for analogue plays in
conjugate margins. Using paired margins is a powerful way to evaluate basins in search of overlooked
plays. Insights gained from the Rockall, Porcupine and Orphan have been used to evaluate systems
and plan exploration programmes.
Interest in Morocco and NS has been triggered by licence activity. Using data/maps across the margin
is vital in understanding the critical synrift and early postrift play systems. The paper is based on work
undertaken for OETR in Halifax and studies completed on the Moroccan margin. Both margins show
that when integrated into play analyses there is potential for significant volumes of hydrocarbons. The
use of conjugate margin analysis is critical in developing models for de-risking hydrocarbon prospectivity.
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Remaining Exploration Potential of the Paleozoic Section in Abu Dhabi
More LessThe pre-Khuff principal reservoir, Unayzah formation consists mainly of distal braid plain sandstones
with minor aeolian deposits. Facies controls on reservoir quality are weak. Quartz cement, Illite and
compaction are the main causes of reductions in reservoir quality in the Unayzah. Quartz cementation
tends to be most severe in the cleanest, coarsest sandstones and near certain fractures.
Paleozoic seals are provided by the Basal Khuff Clastics, tight basal Khuff carbonate and Middle Khuff
Anhydrite. The base Khuff carbonate seal does not appear to be regional extensive, but localised and
potentially prospect specific. However, there are insufficient data to accurately define the seal for the
Unayzah hydrocarbon accumulations.
The main challenge that faced the Paleozoic source evaluation and basin building was the presence of
few deep well penetrations. Therefore, much of the unknown source and tectonic information were
derived from the surrounding countries. This comes from understanding the regional tectonics and
depositional trends of the southeastern Arabian plate, which helped extrapolate the source trends into
the Abu Dhabi area.
The Silurian source rocks basin modeling was constructed to define the timing of hydrocarbon charge
from this source rocks. Also, the objective of this modeling was to gain an understanding of how the
Paleozoic hydrocarbon system works and, specifically, comparing the timing of hydrocarbon charge
with the timing of fields structural growth history. The basin modeling work of the Silurian Hot Shale
source rocks started by building an extensive database, which includes the information related to
source rock distribution, heat flow of the basin and the construction of the stratigraphic and the
lithological models. Additional inputs such as tectonic events and estimating the magnitude of the
removed section, during the erosional events, were added.
The current maturation modeling indicated that oil from Silurian source rocks was generated early in
the basin history and was widespread by the Late Triassic (220 Ma). Significant gas was present by
Lower Cretaceous (140 Ma) and dominated the hydrocarbon system by Middle Cretaceous (110 Ma).
Significant high mature gas was generated in the early Tertiary (50 Ma). At present-day, charge is still
active in the north of Abu Dhabi.
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Petrophysical Properties Evaluation of Tight Gas Sand Reservoirs Using Integrated Data of NMR, Density Logs and Scal
More LessMany tight formations are extremely complex, producing from multiple layers with different
permeability that is often enhanced by natural fracturing. The complicity of these reservoirs is
attributed to a) Low porosity and low permeability reservoir and b) The presence of certain clay
minerals like illite, kaolin and micas in poress. Evaluation of tight gas sand reservoirs represents
difficult problems. Determination of petrophysical properties using only conventional logs very
complicated. Nuclear magnetic resonance (NMR) logs differ from conventional neutron and density
porosity logs, NMR signal amplitude provides detailed porosity free from lithology effects and
radioactive sources and relaxation times give other petrophysical parameters such as permeability,
capillary pressure, the distribution of pore sizes and hydrocarbon identification. Using of NMR in
individual bases or in combination with density log and SCAL data provide better determination of
petrophysical properties of s tight gas sand reservoirs.
This paper concentrates on determination of three petrophysical parameters of tight gas sand
reservoirs: First, Determination of detailed NMR porosity in combination with density porosity,DMR. It
is found that DMR porosity method is a gas corrected porosity, and independent facies porosity model,
Second NMR permeability, KBGMR; it is based on the dynamic concept of gas movement and bulk gas
volume in the invaded zone. It is concluded that KBGMR is facies independent technique and this is the
most important value of this technique and Third Capillary pressure derived from relaxation time T2
distribution and then it could be used for formation saturation measurements especially in the
transition zone. It is found that the assumptions of capillary pressure approximation from T2
distribution can be applied in gas wells as well with some consideration due to gas and mud filtrate effects.
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Co-Krigged Porosity Modeling Exhibits Better Results than Conventional Regression Analysis and Multiattribute Transform Porosity Models
Authors Amjad Hussain and Aamir RasheedReservoir heterogeneity characterization is always a real challenge for the sub-surface professionals.
Although there is no direct way to assess the true heterogeneity, still certain models can imitate the
important features of variability. The spatial distribution of reservoir properties can be determined by
stepping through a workflow which starts where standard workstation seismic and geologic
interpretation ends. In order to obtain the most accurate and detailed results, one must design a
multidisciplinary workflow that quantitatively integrates all the relevant sub surface data. This paper
demonstrates the enhanced results of regression analysis and the multi-attribute transforms which are
used for porosity prediction in one of the areas in Middle Indus Basin. The co-kriging method used in
geostatistics has been applied to derive a combined effect of both the techniques. The dataset used for
this study consists of the available well data including VSP & the petrophysical logs, a 3D seismic
volume consisting both reflectivity & Inversion data for attribute extraction. A conventional regression
analysis using the single polynomial function incorporating the AI & the well porosities were used to
extrapolate the average porosities away from the known control points. We then applied the multiattribute
transform using various seismic attributes and the well data. A cross-validation of porosity
with the significant seismic attributes was done through neural networking. The results were then
applied to derive initial porosity map. Both the results were integrated using co-kriging approach which
involved creation & comparison of different variograms to get the enhanced version of porosity model.
The co-kriged porosity maps showed a better delineation of good porosity zones as compared to initial
porosity maps.
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