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GEO 2010
- Conference date: 07 Mar 2010 - 10 Mar 2010
- Location: Manama, Bahrain
- Published: 07 March 2010
1 - 20 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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