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GEO 2010
- Conference date: 07 Mar 2010 - 10 Mar 2010
- Location: Manama, Bahrain
- Published: 07 March 2010
21 - 40 of 457 results
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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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