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Second EAGE Workshop on Iraq
- Conference date: 15 Sep 2013 - 18 Sep 2013
- Location: Deep Sea, Jordan
- ISBN: 978-90-73834-63-7
- Published: 15 September 2013
1 - 20 of 38 results
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Sedimentology and Sequence Stratigraphy of the Mishrif Formation and it's Impact on Reservoir Heterogeniety, Rumaila Field, Southern Iraq
Authors C. Lehmann, K. Ryder, S. DiSimone and S. PerrottaThe Upper Cretaceous Mishrif Formation of Southern Iraq deposited as part of a large carbonate platform system spanning across the Arabian Plate from Iraq to Oman. The carbonates are the host of some of the most prolific hydrocarbon accumulations and form one of the major reservoir units of the Rumaila Field. The Mishrif Formation is part of the second-order systems tract spanning from the upper-most Albian to the Turonian. The Ahmadi Formation is part of the Transgressive Systems Tract (TST), and the Rumaila and the Mishrif Formations are part of the Highstand Systems Tract (HST). The Mishrif is bound at the top by an Arabian plate-wide unconformity. The Mishrif Formation was further divided into five 3rd-order sequences. The lower three of these sequences comprise the Mishrif B (mB) while the upper two sequences make up the Mishrif A (mA). Extensive core studies helped to understand the depositional environment and the impact of the sequences on reservoir quality of the Mishrif reservoir.
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Mishrif Reservoir Characterisation at Majnoon: Implications for Future Waterflood
Authors N. Jaffey, A. Dasgupta, S. Basu, A. Turki and A. AwadeesianNew core description (MJ-29), pressure data and log correlation has been interpreted to further characterise the Mishrif Fm. at Majnoon field and it’s impact on future waterflooding: 1. Cemented layers at parasequence tops and/or flooding surface mudstones form pressure baffles/barriers between Mishrif and Ahmadi parasequences. Implications for waterflood: Parasequences act as separate drainage units. Non uniform pressure depletion at end of depletion phase. During waterflood, most water may be diverted to higher perm depleted layers, resulting in poor vertical sweep efficiency. 2. High perm layers in mA and mB2.1 are laterally extensive throughout the field. Implications for waterflood: Selective perforation strategy in water injectors may be required to avoid high perm zones and improve vertical sweep efficiency. 3. Khasib B in pressure communication with Mishrif and Ahmadi. Implications for waterflood: Opportunity to develop Khasib B together with Mishrif/Ahmadi reservoirs 4. Deterioration of net thickness from west to east. Implications for waterflood: Expected recovery per well is likely to be poorer on eastern flank. Waterflood in the flanks may warrant different strategies. 5. Significant lateral porosity variation along field crest Implications for waterflood: Different areas of Mishrif may warrant different pattern configuration.
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Impact of Reservoir Heterogeneity on Field Development and Reservoir Management of the Mishrif Reservoir, West Qurna I, Southern Iraq
Authors L.A. Yose, H. Alqassab, S. Fullmer, S. Van Simaeys, A. Wawrzynski, D. Viator and M. StoneThe Mishrif reservoir comprises the main discovered developed reservoir at West Qurna I field in southern Iraq and has been on production intermittently since 1999. Core, log and dynamic reservoir data are being integrated to characterize and model the impact of reservoir heterogeneity on reservoir performance and development plans, including waterflood response. Reservoir heterogeneity is driven mainly by stratigraphy and depositional facies, and an integrated sequence-stratigraphic model has been developed to guide reservoir characterization and modeling. Shallow-water skeletal grainstone facies comprise a relatively small volume of the reservoir, but form the dominant flow units in the reservoir. Permeabilities range from 10’s to 1000’s of millidarcies based on integration of core and well test measurements. Due to the long-term shallowing-upward trend within the Mishirf, grainstone is mainly developed in the regressive, upper Mishrif zones, when accommodation space was more limited. Permeabilities in grainstones are enhanced by dissolution associated with subaerial exposure at sequence boundaries. Outer-shelf packstone and wackestone facies comprise the bulk of the reservoir rock volume and are dominated by microporosity. These facies exhibit high porosity (> 20 %), but low permeability (< 10 millidarcies) due to small pore throat sizes. Microporosity is developed throughout the Mishrif, but is dominant in the wackestone/packstone facies of the transgressive lower Mishrif (includes Rumaila Formation). The permeability contrast between high-permeability grainstone and low-permeability packstone/wackestone facies presents significant challenges to reservoir development and management. One challenge is optimizing waterflood effectiveness. The permeability contrast between high- and low-permeability rock types will result in differential waterflood advance and reservoir sweep, with water moving more rapidly through the higher-permeability flow units and potentially by-passing a large rock volume with lower permeability. Production and injection logging indicate that grainstone intervals account for the majority of reservoir production and injection in the upper Mishrif. The geometry and connectivity of the grainstone bodies vary significantly by sequence-stratigraphic interval, ranging from field-wide thief zones, to more discontinuous grainstones of limited lateral extent (1-2 km). Waterflood design and completion strategies need to be developed and managed on a zonal basis to account for these geologic variations. Another challenge is optimizing recovery from low-permeability microporous rock. A large volume of reserves is in microporous rock, especially within the lower Mishrif. Appraisal of the lower Mishrif with high-angle wells is planned.
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Geological Controls on the Distribution of Reservoir Quality in a Carbonate Formation
Authors A. Ortenzi, O. Borromeo, A. Bersani, N. Bona and C. MaragliuloA continuous core taken in the Middle-Late Cenomanian reservoir provided significant information about the main geological controls on reservoir quality. This paper discusses the impact of facies types and diagenetic modifications on the pore system and thus on the overall efficiency of the reservoir, giving conceptual models for the reservoir model building. The cored section investigated about 150m of the reservoir. from top to almost the bottom.
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Field Development Plan Optimization of Mishrif Reservoir in Majnoon Oilfield
Authors M. Gupta, A. Dasgupta and K.V.K. PrasadThe paper discusses the optimized field development plan for Majnoon with special emphasis on the major Mishrif reservoir. Mishrif is the largest reservoir in Majnoon with expected OIIP of more than 20 billion bbls and a large areal coverage. One of the key uncertainties in Mishrif is the reservoir performance under sustained water injection. The base case development plan for Mishrif is initial depletion followed by inverted 5 spot 100 acres pattern injection. Since reservoir is quite heterogeneous single development scheme throughout the field is not suitable. Several iterations for development plan optimizations including voidage replacement optimization resulting in a ‘hybrid phased’ development is planned with ‘5 spot 100 acres pattern injection’ in the crest and ‘200 acres depletion’ for the flank. The development plan optimization was done by integrating the results from the reservoir simulator into an in-house developed Excel based tool. The Excel based tool was used to analyze the large simulation dataset. This effort led to a robust development plan for Mishrif in terms of well count, well and pads phasing, water injection distribution and voidage replacement management. This work led to 30% reduction in well count without impact on recovery factors.
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Water Flood Management of the Mishrif Reservoir, Rumaila Field, Southern Iraq
Authors B. Salim, K. Almond, R. Van Den Ham and L. ZongfaThe Rumaila field in southern Iraq is a super-giant oil field and contains multiple, stacked, world-class reservoirs. The Mishrif carbonate formation is one of the largest and least-developed Rumaila reservoirs and is a key focus of the Rumaila Operating Organization (ROO) work activities and budget. . At the start of production in 1973, Mishrif well rates were high with average rates exceeding 10,000 bbl/day. Today, after production of only 3% of the STOIIP, reservoir pressure has fallen significantly to the point that many wells have ceased to flow and active wells are flowing only 1,000-3,000 bbl/day. This pressure declined and the absence of any significant water production, suggests the absence of an active aquifer. Material balance work supports this position. The challenge to improving recovery from this reservoir lies in increasing reservoir pressure and mobilising additional oil. A major waterflood expansion project has been planned in order to increase and maintain pressure above the Mishrif bubble point pressure. The full-field water injection project began April 7, 2013 in the first phase of this massive development project. Water injection commenced in 2010 into the Mishrif in three trial areas in the north part of the field. The past three years of trial area operation have yielded encouraging results to water injection in the Mishrif. The first stage of the water injection expansion project involves treatment of water at the Qarmat Ali plant in Basra and then delivery through large pipelines to the existing Cluster Pump Stations (CPS) in north Rumaila. Conversions of producers to injectors are planned in order to convert the field from an existing line drive injection pattern to an inverted 9-spot with a 5-spot pattern ultimately planned. In addition, the wellwork plan includes the installation of larger tubing, packers and high-pressure wellheads. The injection process is under continuous surveillance to monitor the reservoir response to water injection. Reservoir pressure is being monitored in numerous wells both before and during water injection. Water quality is monitored at the CPS facilities and at each injection well to ensure appropriate quality injected water is injected into the reservoir. Individual injection well rates are measured weekly and integrated asset models are updated to improve the allocation of injection water. Produced water samples are taken in wet wells to ascertain water injection breakthrough. It will take some time before the water injection is expected to impact the pressure in the entire Mishrif formation. Significant steps are being taken by ROO to progress and improve production from the Mishrif reservoir in the near future.
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Fluid Contact Determination Tools for Carbonate Reservoir and its Impact on Field Development
More LessThis paper describes various methodologies used in arriving to the determination of fluid contact in Mishrif reservoir of Halfaya. It is hoped that this paper will generate an interactive and lively discussion which will enhance our understanding of carbonate reservoirs in Iraq as well as globally.
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Successful First Commercial Production of Halfaya Field – Feedback on Mishrif
Authors F. Bruyere, T. Ping and O. JinThe Halfaya field, discovered in 1976, is located in the south area of Iraq towards the border with Iran in the Amara region. The field structure is an anticline of about 10 km width by 30 km length with several oil bearing reservoirs of Cretaceous to Miocene age. These reservoirs in either carbonates or clastics formations contain large volumes of hydrocarbons (>16 Gbbl OOIP), the Mishrif reservoir containing around three fifths of the OOIP. First Commercial Production commenced on June 16th 2012 with contribution from 27 wells including 6 originally existing producers. With the rapid development of the Mishrif reservoir, a large data acquisition program was carried out. The 30 new wells penetrating the Mishrif were fully logged with a standard suite of tools and some wells were logged with Nuclear Magnetic Resonance or imagery tools.
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The Use of Production Logs in Order to Understand Reservoir Heterogeneity of the Mishrif Reservoir, Rumaila Field, South Iraq
Authors A. Holden, C. Lehmann, K. Ryder, K. Choi and K. AlmondThe Rumaila field is located in South East Iraq and contains multiple reservoir intervals, including the Upper Cretaceous Mishrif carbonate. This reservoir has been on production for many years but still contains significant oil reserves. Reservoir pressure has dropped due to historical production and, therefore, large scale water injection is planned to support future production.
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A Classification Scheme for Mishrif Carbonate Microfacies in North-Rumaila, West-Qurna and Majnoon Fields
Authors A. M. R. Awadeesian, N. Jaffey and S. BasuIt is a vital subject to establish a stratigraphic tool: specifically concerns on high-resolution (HR)-facies-analysis and classification terminology for the Mishrif multi-carbonates In southern Iraq oil fields. A HR-microfacies investigation approach: is aptly submitted for petrographic – diagenetic / pore-system evaluation; to be stand-by utility for sequence stratigraphic inquiry and reservoir geology construction of the important Cenomanian – Early-Turronian carbonate succession in the southern fields. This lexicon could be considered as a supportive-data-tool to dealing with the Mishrif-carbonates-factory in the super-giant North-Rumaila, West-Qurna and Majnoon fields. The former fields are pertinently considered prototype-model; for appraising the other regions in southern Iraq.
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Reservoir Surveillance by Production and Pulsed Neutron Logging in the West Qurna I Field, Southern Iraq
Authors F. Alali, R.A. Abdullah, A. Abdussalam and D. ViatorThe West Qurna-1 field is comprised of a series of stacked carbonate and clastic reservoirs with highly variable reservoir properties. The main producing reservoir is the Cretaceous Mishrif carbonate, characterized by reservoir heterogeneity ranging from high permeability grainstones to low permeability microporosity-dominated facies. This reservoir quality heterogeneity produces high contrast flow units which pose a challenge to reservoir management and require extensive reservoir surveillance. Reservoir surveillance has many different aspects, including monitoring zonal flow contributions, zonal injection performance (waterflood), pressure monitoring, saturation changes, and oil-water contact (OWC) movement. Production logs (PLTs) are primarily run in wells completed in the carbonate Mishrif and the clastic Zubair reservoirs. Key objectives are (1) to measure well production rates in light of scarce fieldwide surface rate metering, (2) to determine zonal flow contributions and waterflood injection performance from acidized commingled perforated intervals, (3) to determine static/flowing cross flow patterns, (4) to measure flowing and static pressures for Psat maintenance, and (5) to obtain indications of cross-flow from behind pipe. An additional objective is the recent use of PLT toolstrings in the Mishrif for single rate production build up (PBU) analysis for permeability-thickness (kh), skin, and drainage area reservoir heterogeneity for wells with single and multiple perforated intervals. Where surface rates are available via test separators or Multi Phase Flow Meters, PLT results from the same time frame are integrated with the surface well performance data (ie. flowing upstream pressures and choke settings) to set optimal surface flow conditions within established reservoir surveillance guidelines (ie. guide flowing upstream pressures to ensure down-hole flowing pressure is above oil Psat). PLT results are used to guide current perforation and zonal shut-off strategies and will guide future water injection strategy. For saturation and OWC monitoring, Pulsed Neutron Capture (PNC) saturation logs are predominantly run in sigma capture mode. Mishrif saturation logs have been run since 2010 to obtain base logs for future time-lapse monitoring for (1) flank OWC movement, (2) saturation changes offsetting injection wells, and (3) monitoring water encroachment along recognized high kh zones. PNCs are also run on an as-needed basis for drillwells without complete open-hole logs and as diagnostic logs on high-water cut wells that have stopped flowing. Challenges for the PNC program include recognizing true saturation changes in heavily acidized completed intervals, and establishing an efficient repeat logging pace for time-lapse.
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Rock Physics Based Seismic Charaterization of a Carbonate Reservoir
Authors A. Amato del Monte, F. Luoni, O. Borromeo and E. PaparozziAn innovative approach for carbonate seismic reservoir characterization was researched, tested and applied. This approach is based on the integration of core analysis (i.e. laboratory acoustic measurements and pore type petrographic description) into a rock physics model which takes into account the pore type to explain the typical variability of velocities that carbonate reservoirs exhibit for a given porosity. The rock physics model used is based on the Extended Biot Theory (EBT) and allows the calculation of a property (frame flexibility factor or Gamma-K) which in principle can be linked to the rock pore structure
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Improved Oil Recovery Technique for Mishrif Carbonate Reservoirs in NR and WQ Fields in Iraq
Authors A.M.R. Awadeesian, K. Al Obaidi and S. ChatterjeeThe Mishrif carbonate reservoirs in the North-Rumaila and West-Qurna oil fields are impressively characterized by successive-TMF-buildups. These buildups are ranked into 3-specific-reservoir-facies-performance groups, reflecting multiple-vertical-stacking pattern (RFP3-to-RFP1). A Pre-mature water-breakthrough; is seriously expected to be created mostly by RFP1 type, with vast increase in the water-oil-ratio versus continuous decrease in the oil recovery, when these carbonates treated with usual water-oil-displacement technique. To improve oil recovery for Mishrif carbonate reservoirs by overcoming the above expected problems: a modified water-flooding technique is lab-organized and settled by (micro-booster-displacement) methodology; on tens of standard-size-plugs, characterized by multi-TMFs / differential poro-perm buildups, taken from the investigated good-recovery cored intervals in the representative oil-wells from both fields. Suitable economic/soluble polymer with surface active agents were used, and polymerized-alkaline-surfactant-water,PAS-water flooding technique; is performed. A decrease of (10 to 15%) in water-oil-ratio; is successfully achieved after water-breakthrough by successive injections of the prepared controlling agent of (crudeoil-in-wateremulsion) type. An analogy scheme by facies/pore-analogy-system has achieved for the Majnoon domain, and RFP3-to-RFP2 / limited-RFP1 buildup is more matched, with regular / non-constrained petro-link, and limited oil-bypassing zones. The 1st and 2nd stages of the presented water-oil displacement-technique; is of special request for Majnoon carbonates reservoirs development.
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Yamama Reservoir Compartmentalization in Majnoon: A Preliminary Perspective
Authors S. Chatterjee, S. Basu and A.A. TurkiThe Yamama carbonate is the deepest drilled reservoir in Majnoon field with the second largest oil volume. The Yamama reservoir is about 300 m thick and subdivided by thin discontinuous mudstone units into Yamama A, B1 and B2 major reservoir units. Laterally, the Yamama A, B1 and B2 reservoirs are compartmentalised into at least two separate fault compartments based on the following evidence: 1. Seismic interpreted fault: A west dipping normal fault was interpreted on three 2D seismic lines on the crest of the field. The fault offset is subtle (less than one seismic loop) and 2D seismic quality is low therefore the lateral extent of this fault beyond the three interpreted seismic lines is highly uncertain. This suggests that the Yamama is compartmentalised with a western and eastern fault block. 2. Pressure data: MJ-12 (western flank well) shows pressures elevated by about 70 psi compared to MJ-08 and MJ-09 (crestal wells) at the datum depth of 3900 mTVDSS. 3. Fluid contacts: OWC in the western flank wells (MJ-03, MJ-12 and MJ-15) is about 120 m deeper than in the rest of the field.
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Zubair: An Integrated Understanding from New Well in Majnoon Field
Authors A. Srivastava, S. Jain, M. Vaidya, K. Bandyopadhyay and F. AbbasMajnoon is a giant oilfield located 60km north of Basra, Iraq close to the Iraq-Iran border. It was discovered in 1976. Due to various wars the production has been interrupted through time. It is a banana shaped structure with a NNW-SSE orientation in the southern part; nearly N-S in the centre and NNE-SSW in the northern half. The field has multiple proven oil reservoirs, mostly carbonate in origin except for the clastic pulses of Nahr Umr and Zubair Formations. The Zubair Formation occurs in northern Saudi Arabia, Kuwait and most of southern Iraq and Iran. It is stratigraphically placed below the Shua’iba formation and separated from the over pressured Yamama formation by the Ratawi shale. In the First Commercial Phase (FCP) of drilling, Zubair Formation is a major target for sweet oil production. Out of the 18 planned wells, eleven wells target this formation. In Majnoon, there remains a wide range of uncertainty in Zubair reservoir properties and distribution due to sparse data. The major part of our understanding comes from the 10 legacy well penetrations and poor quality 2D seismic data. To supplement this, analogue data and published literature have been used. In this paper, the Zubair formation has been reviewed based on the new information from 10 wells which have already penetrated the Zubair during the FCP phase of drilling.
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An Integrated Description of the Stratigraphy and Depositional Environment of the "Main Pay" Member of the Zubair Formation, Rumaila, Iraq
Authors M. Wells, D. Kitching, D. Finucane and B. KosticRumaila is one of the world’s supergiant oil fields. At the end of 2009, BP entered into a Technical Service Contract as the lead contractor with the South Oil Company of Iraq (SOC) and PetroChina to develop the remaining resource. The Early Cretaceous Main Pay is one of the largest reservoirs in the field. A rich dataset has recently become available including access to nearly 1 km of core, wireline image logs, open hole logs, formation pressure tests and cased hole saturation logs. Biostratigraphic analysis of the core indicates that most samples contain both marine and terrestrial mircoflora, confirming a marginal marine gross depositional environment. Palynology has proved to be of particular value, with diverse and abundant recovery of algal and dinoflagellate cysts from fine grained deposits allowing for a high resolution bio-chronostratigraphic model to be built. A set of marginal marine genetic elements was interpreted through the integration of core sedimentology and palynofacies. Two fourth-order regressive-transgressive cycles are identified in the Main Pay and overlying Upper Shale Member with additional higher-order cycles recognised, especially in the north of the field. The cycles highlight the phased advance and retreat of a river-dominated and tidally influenced delta system. The observation of cyclic bundles of thin foreset shale laminae confirms the influence of tides. Cores from the south of the field are dominated by fine to medium grained cross-bedded sandstones that were mainly deposited in lower delta plain distributary channels. Towards the north of the field, grain sizes tend to reduce and more heterolithic mixed sand and shale deposits are preserved. In addition to distributary channels; mouth bar, shoreline and tidal flat deposits are present in the north, suggesting a more basinward setting. Non-reservoir elements in the Main Pay are dominated by prodelta “fluid” mudstones picked primarily based on their palynological assemblages. These elements typically overlie a transgressive deposit and flooding surface and mark the early phase of deltaic advance. These deposits tend to be laterally extensive and form the foundation for the stratigraphic description. The stratigraphic and depositional descriptions have been extended away from cored wells using well logs, formation pressure tests and fluid saturation data. The current description suggests the potential for targeted development of bypassed oil beneath flooding shales and in the mouth bar, shoreline and tidal flat genetic elements.
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In Search of the Remaining Oil in the "Main Pay" Member of the Zubair Formation through Surveillance Oil Mapping, Rumaila Field, Southern Iraq
Authors D. Kitching, R. Farmer and M. AbuzaidRumaila is one of the world’s supergiant oil fields. At the end of 2009, BP entered into a Technical Service Contract as the lead contractor with the South Oil Company of Iraq (SOC) and PetroChina to develop the remaining resource. The Main Pay is one of the largest reservoirs in the field. It has played a large part in delivering production for more than 50 years and is expected to play a significant role in securing and sustaining field plateau production with billions of barrels yet to be recovered. The Main Pay is under active waterflood (aquifer support supplemented by water injection). In 2010, a massive program of cased hold saturation log surveillance was initiated, with logs acquired on 106 wells across the field with the objective of improving understanding of the current distribution of fluids in the reservoir. The acquisition of this data coincided with the beginning of an intense period of study on nearly 1 km of historical core released to BP by SOC that concluded in 2012. The Main Pay is interpreted to have been deposited in a largely progradational to aggradational, fluvially dominated and sand-rich deltaic environment. Occasional well-developed marine flooding surfaces are observed, usually succeeded by prodelta shales. These shales can be correlated widely and act to break up vertical connectivity and reduce vertical sweep efficiency. Whilst the majority of effective reservoir rock is found in high quality laterally and vertically amalgamated distributary channels, some lower quality reservoir is found in more distal or marginal argillaceous mouthbar, shoreline and tidal sand flat deposits. This heterogeneity is expected to reduce areal sweep efficiency.
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Preliminary Sequence Stratigraphic Framework and Reservoir Characteristics of the Mauddud Reservoir, West Qurna I Field, Iraq
Authors S. Van Simaeys, S. Fullmer and L.A. YoseA new sequence-stratigraphic framework is proposed for the Mauddud formation at West Qurna I Field, based on the integration of core, well-log, biostratigraphic data, and limited 2D seismic data. The Mauddud Formation is ~150m thick in the West Qurna 1 field area and was deposited on a broad carbonate shelf developed during the Albian (Early Cretaceous). The Mauddud Formation unconformably overlies the Nahr Umr Formation in most parts of the basin and can be described as a second-order composite sequence that is composed of three high-frequency, shallowing-upward depositional sequences. The overall shallowing-upward trend in the Mauddud Formation culminates in a stack of peri-tidal facies with multiple exposure surfaces in the shallowest sequence and a big regional unconformity at the top of the Mauddud. The overall stacking pattern would place the Mauduud in the prograding portion of a composite sequence. The identified high-frequency sequences can be correlated across the study area, consistent with deposition on a broad carbonate shelf and are subdivided into parasequence sets that provide a higher resolution reservoir zonation. Carbonate lithofacies were deposited in inner to lower ramp, normal to slightly restricted environments. The lower part of the Mauddud Formation represents a transgressive system (lower 2 sequences) and displays a fairly uniform lithology across the field. The vertical and horizontal extension of this facies all over the Arabian basin indicates long-term stability of the basin. In areas of relatively higher energy, localized rudist banks were established on the basin margin. Local lagoons were also formed wherever the topographic or hydrodynamic settings allowed. These are characterized by algal-pelletal facies. The Mauddud highstand sequence set displays a lateral change in lithology ranging from good quality grainstones in the northern and central part of the field to lower quality peri-tidal packstone/wackestone facies in the southern part of the field. In general, most Mauddud lithofacies have moderate porosity and low permeability, with microporosity as the dominant pore type. Intervals with enhanced reservoir quality can be related to fracturing and faulting or the presence of rudist floatstone-rudstone facies. The proposed sequence-stratigraphic framework and the sequence-stratigraphy-keyed facies scheme result in a predictable distribution of reservoir and seal facies and allow for a better prediction of the vertical and lateral distribution of reservoir quality and reservoir continuity at both field scale and regional scale. Results are being incorporated into reservoir models and integrated with well test and additional core data to further evaluate well productivity and controls on flow within the reservoir.
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Regional Petroleum Geology of Central and South West Iraq
By A.D. HorburySubsurface geology of Iraq is generally poorly understood away from the main petroleum producing areas of the SE and the foldebelt of the NE. Relatively little interpretation has been made and published using regional 2-D seismic coverage, whilst data from wells is scattered and of variable quality; and outcrop studies are still in their infancy. Largely this is due to a perception that the broad down-to-the east regional dip across this whole region, precludes the development of significant traps and therefore the petroleum industry has focused its resources elsewhere. As a first pass strategy this is undoubtedly sensible but as acreage and fields in parts of the country with existing production are allocated to operators, attention will inevitably focus updip in a westerly direction.
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Integrated Approach of Exploration Tools Using Seismic Data, Facies Analysis, Source Rock Maturation Modelling and Hydrocarbon Formation and Expulsion Defining the Petroleum Systems in Iraq
Authors N.Z. Marouf and M.B. AL-GailaniAnalysis of ten east-west and two north-south regional seismic transects across the whole of Iraq using Kingdom programme involving more than 150 seismic lines showed at least two phases of folding separated by angular unconformities influencing the Palaeozoic sequence. Extensional phases followed; one during the Triassic, the other one during the late Cretaceous influencing the Mesozoic sequence along the eastern parts and the Zagros folded belts. These two extensional phases are very well imaged by the seismic data. Further, compression phases followed; the first one during the early Tertiary and the other during the late Miocene-Pliocene. These resulted in a positive basin and structure inversion. The positively inverted structures were interpreted using the Kingdom programme. Data from deep wells were incorporated in the interpretation using time, interval time, velocity, thickness and depth maps were generated from different parts of Iraq. The results showed very detailed picture of the geometry of the major and minor structures. Pre folding restoration and flattening of some horizons allowed the construction of the spatial configuration of the sedimentary basin through time. Isopach and facies maps were produced for each Mesozoic-Cenozoic sedimentary cycle.
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