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First EAGE Workshop on Iraq - Hydrocarbon Exploration and Field Development
- Conference date: 29 Apr 2012 - 02 May 2012
- Location: Istanbul, Turkey
- ISBN: 978-94-6282-050-0
- Published: 02 May 2012
34 results
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Structural Interpretation of The Zagros Fold-Thrust Belt (Northern Iraq)
Authors R. Di Cuia, F. Arboit and A. RivaRecently Northern Iraq has been the focus of extensive hydrocarbons exploration with high success rate as confirmed by the discovery of large oilfields mainly in fractured carbonate reservoirs. The fault and fracture network was produced by tectonic evolution of the area located in a complex structural domain in between the Arabian and Eurasian plates. Evidences for the Arabia–Eurasia Plates convergence can be observed across the entire mountain range of the Northern Iraq and related to a combination of shortening on E-W/NW-SE-trending folds and thrusting, both related to several shortening stages occurred between Cretaceous and Miocene. It is proven that most of the oil accumulation of Northern Iraq originated by a migration from earlier deeper accumulations which were initially hosted in stratigraphic or old structural traps, and which are now largely depleted. The structural evolution of the area has enhanced lateral migration from different source rocks of Upper Jurassic to Lower Cretaceous ages into the present-day traps which includes Late Tertiary inversion anticlines. During Late Tertiary, large scale folding and faulting/fracturing produced the deformation and leakage of older structures holding hydrocarbon that allowed the late migration to shallower limestone reservoirs (Cretaceous – Tertiary), or escape to surface. Hence in this portion of the Iraqi Zagros range most of the oil and gas discoveries lies into carbonate rocks reservoirs, such as the Cretaceous Qamchuqa Shiranish, Hartha and Kometan formations (all important carbonate fractured reservoirs), and the Teriary Fatha (Lower Fars) Formation (limestone dominated unit) In general, fracturing percentage is variable and becomes more localized close to faults. Fault zones could be relatively narrow and characterized by an intense fracturing. The prediction and exact characterization of the faults and fractures network is a crucial factor for the positive results of hydrocarbon exploration. The study area, part of Iraq, lies north of Latitude 35° North. The main purpose of this study was to examine the nature of the High Folded Zone and the structural styles across this region. The interpretation is based on the integration of the available geological and geophysical subsurface data, stratigraphy and tectonic published information, present day stress field measurements and a new structural interpretation based on remote sensing techniques for all the anticlines in the high folded zone. These data were integrated to build a regional structural model and to provide a detailed structural description of the folds located in the High Folded Zone.
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Majnoon Field, SE Iraq: A giant unique among other giants?
Authors M. Mehenni and F. GuitMajnoon, one of the South Iraq Giant oil fields, is a 52 km by 15 km greenfield which was discovered in 1979, approximately 60 km north of Basrah, close to the Iraq/Iran border. The northern part of the field area lies in the Hawizeh marshes, a designated RAMSAR site (Wetlands of International Importance). Majnoon has a current target production of 60,000 BOPD (barrels of oil per day) from 17 wells and a STOIIP of 38 Billion barrels, according to Ministry of Oil data, contained in 12 reservoirs. The drilling of 15 new wells and a work-over campaign during 2011-12 will allow production to reach the first contractual target of 175,000 BOPD (SIPD, 2010). The FDP to be submitted by March 2013 will define the development plan to take production levels towards the target production level of 1.8 MM BOPD.
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New Insights to the Implications of Salt Tectonics in the Northern Part of Kuwait Arch: An Integrated Modeling Study
By P. SinghAn integrated model based approach involving depth converted 2D seismic sections, gravity, magnetic and well data is adopted to map occurrence and spatial limits of Eocambrian Hormuz Salt in the subsurface and to evaluate its influence on the development of structures in North Kuwait. The northeastern Arabian basin shows a poly-phase tectonic evolution that occurred under different stress regimes. Role of Eocambrian Hormuz Salt in evolution of structures on the Arabian Plate as well as Zagros Fold belt is well established. In Kuwait, salt triggered structures are not investigated in view of the fact of its non-piercement to the surface, attenuation of seismic signal at greater depths where the salt bodies are envisaged to be present and presence of multiple events. Additionally, carbonate stringers reported from Eocambrian salts in the adjoining regions generate seismic reflections and add to the problems of salt mapping. The depth converted seismic sections are used as a bit map for 2¾D modeling to guide the geometry of the density polygons. The integrated models have brought out the presence of salt in the northern Kuwait. One of the deepest well in the northwestern Raudhatain encountered Hormuz Salt at a depth of 20200 feet and corroborated the model. The major faults are also mapped from integrated models. A diapiric salt structure (Jabal Sanam) having surface manifestation is reported north of the Kuwait border and lends further credence to the model. Structural analysis of subsurface data from the integrated modeling in the northwestern Raudhatain suggests the presence of the Hormuz Salt Pillow in the core of the anticline. This study is also extended to the Mutriba Structure to cover the northern part of the Kuwait. The role of tectonic events, particularly extensional faulting, and differential loading of sedimentary cover above the mobile salt layer is the main factor in triggering of salt diapirism. It is envisaged that Permo-Triassic Tethyan rifting, Cretaceous-Paleogene obduction and compressive events associated with basement reactivation of north-south Arabian trends could have initiated episodic salt diapir activity in the northern part of Kuwait. The faults probably played a role in weakening and breaking the overburden, and hence producing pathways for the salt movement. The salt pillow might have slowly grown in a compressive regime arising from Zagros Orogeny. The structure needs to be evaluated in view of its unique structural history and hydrocarbon entrapment avenues.
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Fracture study of potential reservoirs in Northern Iraq
Authors L. Csontos, A. Magyari, T. Pocsai and C. MajercsikA fracture study was performed in Kurdistan Region of Northern Iraq. Based on exploration efforts, the Sargelu and Kurrachine carbonates are fractured reservoir rocks in the region. The study was based on traditional fieldwork. Data were collected in 6 anticlines and 9 formations. Orientation data of all fractures, faults within several blocks of 1 square metre were recorded, together with their length, aperture, frequency, filling, surface characteristics. Data were plotted on stereonets in present state, and in back-tilted (unfolded) state. Analysis was performed in latter position. Data were separated into layer-perpendicular and layer-oblique sets. Part of the fracture sets shows clear relation to local folding. Perpendicular (tensional) and shear joints form symmetrical sets. In these cases there are two oblique/shear sets: one where the acute angle bissectix points to the shortening direction and another, which has the obtuse angle bissectix in the same direction. In some other fracture sets there is strong departure from the local fold orientation. In these cases the different fracture sets can be interpreted as born of the superposition of two symmetric sets related to different fold orientations. This is supported by the measurement of NW-SE to E-W fold axes in the mentioned folds and areas, irrespective of the map attitude of the major folds. Layer-oblique sets were separated into three classes. Steeply dipping joints that were striking parallel to layer-perpendicular family of the same exposure were affiliated to fold-related joints. Flat-dipping fractures were possibly formed by compression. These fractures suggest compression directions. Finally, fractures having dips around 50° were interpreted as normal fault-like shear surfaces. These fractures suggest extension directions. Assessing the estimated structural directions we propose three probable extension events in N-S (NNW-SSE); NE-SW and NW-SE direction. The same exercise suggests (much weaker defined) NW-SE; NE-SW and N-S compression directions. Fault slip measurements in the closer and wider vicinity gave the same or very similar faulting events. In some exposures non-gravitational open fractures and others filled by bitumen were observed. These were mostly longitudinal joints, oriented perpendicular to recent local N-S or NE-SW compression, or shear joints symmetrical to these directions. Longitudinal joints may have remained open due to continuous fold growth. Shear joints may have remained open due to fold-parallel extension, or continuous shear movement. Since recent compressive stress directions play an important role in opening fractures (that are then filled by bitumen), oil migration should be a young process.
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Geochemical and Palynological Analysis in Assessing Hydrocarbon Potential and Palaeoenvironmental Deposition, North Ir
By Ahmed Najafil exploratory wells , Makhul-2 (Mk-2),Qarachuq-1 (Qc-1) and Qarachuq-2(Qc-2), TaqTaq-1(Taq-1), Butmah-15 (Bm-15), Ajeel-8 (Aj-8)and Jabal kand( Jk -1) ,encountered from Butmah Formation ( Lower-Middle Liassic) , Sargelu Formation (Middle Jurassic ) and Naokelekan Formation (upper Jurassic ) .The value of palynological analyses in the undertaken study is to resolve stratigraphic and palaeoenvironmental consequences of Jurassic Period in Iraq , thus the profuse of plant cuticle of translucent phytoclast in the basin of deposition refers to proximal depositional environment due to their specific gravity of this type of plant cuticle , whereas the opaque organic matter produced either from highly oxidized environment or from forest fire residues could refer due to its light specific gravity to distal depositional environment that this type could transported far from the continents toward the aquatic environment . Recurring Type A Amorphous kerogen indicates Oil –Prone beside various amorphous types (B, C, D) within Zagros Fold Belt. The specified palynomorphs recovered from palynological analysis declared so many indications to determine the potentiality of source rocks .Almost all slides shows spores and pollen, phytoclasts and amorphous organic matter. Extracted resins and pigments are indicating toxic environment of type II-III kerogen that generates oil with subordinate gas.Geochemical analysis can aid also the undertaken study by determination the Terrestrial origin and kerogen type II-III .Previously proved that all crude oils within this sub- basin is belong to family A (sourced from Middle Jurassic Sargelu Formation) nearby local basins of family B (sourced from U. Triassic Kurra chine, and Rhaetic Baluti Shale Formation). Jurassic Period is considered as a generative hydrocarbon rock unit by means of both optical and chemical approaches definitely in the Great Kirkuk region and surrounding areas in North Iraq. Meanwhile the current studies focused on the western desert as promising reservoirs related with hydrocarbon pathways from Mesopotamian Basin.
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New paleoshorelines of the prolific Oligocene /Aquitanian sequence from zagros fold thrut belt.Kurdistan Region/N.Iraq.
Authors Fadhil. Ameen and P. OthmanNew paleo-shorelines of the prolific Oligocene and Aquitanian)sequences across Zagros Fold Thrust Belt.Kurdistan Region (N/Iraq) Fadhil Ahmed Ameen and Parween Othman Qadir University of Sulaimani, Dept. of Geology. [email protected], [email protected] ABSTRACT The Oligocene and Early Miocene sequences are mainly comprised of a thick carbonate successions within the Zagros Mountains (Kurdistan Region .NE-Iraq) . Conjugates lines of evidences based on microfacies, paleontology , depositional environments, are used to re-establish the depositional system , paleogeoreaphy and paleo shore lines. Generally, in the High Zagros Fold, the Late Eocene (Pribonian) facies representing by lagoon carbonates of the Pila Spi Formation overlain by the evaporates or siliciclastic facies of the Fatha Formation (Burdigalian-Langhian) manifested by sequence boundary of type one, as major unconformity and sedimentary hiatus for about 13.4 Ma. Kirkuk Group (Oligocene) representing three fourth order Oligocene sequences, within one third order cycle, mostly retrograded over the Late Eocene sequences showing lateral variation in their facies from inner ramp ,middle ramp to outer ramp carbonates and to deep basinal facies. They are deposited during the Tectonic Megasequence Ap.11 and extends from Early Oligocene to Early Miocene (Aquitanian) in the remnant foreland basin depocenter, while in the basin periphery Kirkuk Group are less developed and appear as patchy reef bodies and their sequences may separated by hiatuses of different durations. On other hand, the Early Miocene (Aquitanian) sequence stratigraphic architecture representing by Euphrates and Jeribe Formations with sub-conglomerates between them show a sequence boundary of type one with the overlying Fatha Formation. The Aquitanian -Burdigalian boundary placed almost at the Jeribe –Fatha Formations boundary in the basin periphery, expressing patch appearance within the High zagros belt . The remarkable northern and northeastern wards extensions of the Oligocene (Kirkuk Group) and Miocene carbonates ( Euphrates and /or Jeribe Formations) mostly controlled by basin geometry, basin configuration, and sea level changes before closing of Kurdistan foreland basin and switching from under fill to over fill conditions. As a result new Plaeoshore line for the Oligocene and Early Miocene basins was detected from Kurdistan region NE- Iraq pointing to a new prospective area and shallow carbonates oil and gas fields. Key words: Kirkuk Group, Early Miocene (Aquitanian ) , Sequence boundary, Kurdistan Foreland to Sag basin, plaeoshore line, Zagros Low and High Fold Thrust Belts. New perspective area.
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Exploration of regions with stratigraphic trap potential using seismic inversion and spectral decomposition techniques
Authors S.M. SeyedAli, I. Maghfouri Moghadam and M. JalaliExploration of new hydrocarbon prospects is a significant challenge in petroleum industry. Conventional methods of seismic data interpretation provide the necessary tools for identification of main structures such as anticlines and faults which are capable of hydrocarbon reservation. Locating these prospects makes it necessary to come with knowledge of lithology and existing fluid phase in the reservoir. The problem is more robust when stratigraphic traps come in the area of interest. In such cases utilization of quantitative seismic methods is inevitable. This paper focuses on exploration of stratigraphic hydrocarbon traps among the proved structural reservoirs. The applied methodology in this study consists of combination of inversion and spectral decomposition of seismic data. For this purpose forty two seismic lines which belong to different oilfields at mountainous areas of Zagros Folded Belt has been structurally interpreted in the study area (within the area of 4275 km2). The interpretation of all the lines will lead in to a three dimensional structural model of study area in the time domain. Having the structural model, it is possible to build an initial model of elastic properties by means of petrophysical well logs data. This model will be used in inversion algorithm to obtain acoustic impedances model. The obtained results from the inversion process illuminate the gradual lithology changes between the structures. Due to the overlapping among the acoustic impedance values in geological formations lithology, spectral decomposition of seismic data has revealed the existing ambiguity in lithology determination of interest zones. This is done by preparation of different iso-frequency sections from seismic data to determine the high absorption energy formations such as anhydrites which lack the chance of hydrocarbon reservation. Finally distribution of sand relative to anhydrite, obtained from inversion and spectral decomposition methods, which was in good agreement with sedimentological and stratigraphic results suggests probable stratigraphic traps between proved structural fields.
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ThrustBelt Imaging Challenges – Learning from 3D Fullwave Modeling
Authors C. Gerea, J.M. Mougenot and F. ClementSeismic image quality in foothills and thrust-belts with rugged topography is often very poor with conventional low-fold sparse 3D orthogonal surveys. The most often cited reason is the high-level of shotgenerated noise backscattered from near-surface heterogeneities and irregular topography. Consequently, many depth imaging projects in thrusted terrains have been disappointing.
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Advanced Wide-Azimuth Processing of Dukhan Field Ultra High-Density Seismic Survey for Optimal Reservoir Characterization
Authors A. Leveque, S. Seeni, A. Guerroudj, P. Plasterie, S. Sampanthan, H. Zaki, K. Setiyono and D. Van HulleAcquisition of ultra high-density wide azimuth seismic data was successfully completed over QP’s Dukhan Oil Field early in 2011. The objective for this state-of-the-art, 850 sq km 3D survey was for improved data quality and resolution to allow the imaging of small faults and fracture zones as well as improved structural imaging of deeper reservoirs. Optimal preservation of amplitudes was important for the reliable prediction of reservoir properties away from well control.
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Advanced 3D Land Internal Multiple Modeling and Subtraction, a wide azimuth Oman case study
Authors P. Plasterie, A. Pica, N. Benjamin, M. Bendjaballah, S. Leroy, L. Delmas, P. Zjwartes, R. Smith and T. Van DijkInternal multiple attenuation presents a major problem to both the geologist and the geophysicist. For the first the amount of noise can often be such that accurate interpretation of the primary seismic wavefield is impossible making seismic data unusable. For the second, internal multiples are hard to distinguish in the total wavefiled, and the problem is more difficult to deal with than with surface related multiple. Internal multiples have a dispersed character that creates a curtain of noise often stronger than primaries where move out discrimination or deconvolution techniques fail.
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Petroleum Geochemistry Of Oil Samples From Shallow Boreholes At Sakran Site, Western Iraq
Authors F. R. Al-Rawi, T.K. Al-Ameri and Salih M. AwadhAdmixture of oil with water was shown in two shallow boreholes drilled for ground water purposes to a depth of 117 and230 meters at Sakran village, western Iraq. The sites of these boreholes are located within an area represents the eastern extension of east-west trending Anah graben. Petroleum geochemistry analyses are carried out for samples of the admixture collected from these boreholes. Terpane and sterane biomarker distributions, as well as stable isotope values, are determined for the oil to determine valid oil – to – source correlations. The results show that the oil from this area is of Upper Jurassic age with C28/C29 is 0.75 and with high sulfur content (2.75%). Tricyclic terpanes values as well as hopanes have indicated source rock affinity of carbonates while pristine to phytane ratio have indicated marine algal source of kerogen type II. Oilfield water also are analyzed for cations (Ca, Mg, Na, K) and anions (SO4, Cl, NO3, HCO3) as well as the physical properties (TDS, EC, pH and T), The hydrochemical characterization demonstrated that the origin of these oilfield waters is marine origin. All these information could confirm source rock affinity to the Upper Jurassic Sargelu and Najma Formations in which their ages equivalent to the source in east Baghdad Oil Field and Tikrit Oil Field and with different oil family from the nearby Akkas field, located to the west of this area.
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Applications of New Wireline Technology in a Mature Middle-East Oil Field
Authors L. Finlayson, A. Aziz, D. Viator, D. Mardon, R. Abdullah and F. AlaliExxonMobil is a partner with Shell and the Iraqi South Oil Company in developing the West Qurna 1 supergiant oil field in southern Iraq. In-place oil volumes in the main limestone reservoir are approximately 30 to 40 billion barrels. Other undeveloped clastic and limestone reservoirs include another 10 to 15 billion barrels. Although over 375 wells have been drilled in the field since the late 1970s, very few have advanced logs that are commonplace in most major field developments in which ExxonMobil participate. This presentation will highlight applications of new logging technology including wireline formation pressure, nuclear magnetic resonance, cross-dipole sonic and micro-resistivity imaging. These new technologies are providing key insights into many aspects of reservoir properties including water saturation, pore size distribution, reservoir pressure and connectivity. Latest generation formation pressure tools, provide accurate measurements of formation pressure in each reservoir subdivision. These pressures are related to original reservoir conditions, in currently unproduced reservoirs, whereas in produced reservoirs, they provide the amount of depletion from original conditions, which is related to reservoir connectivity. Nuclear magnetic resonance tools provide a measurement of porosity that is sub-divided into a pore-size distribution. This knowledge of pore-size can be related to several reservoir characteristics including water saturation, micro-porosity distribution and permeability. Cross-dipole sonic tools provide a fast and slow dipole-shear measurement which can be used to calculated formation anisotropy which is related to the presence of natural fractures and formation stress orientation. Micro-resistivity imaging tools provide a very high-resolution image of the borehole wall. These images can be related to formation properties including fractures, rock type and formation dip and direction. Insights from these latest generation wireline tools are helping to build better static and dynamic subsurface geological models. Examples will show initial field logs, processed logs and interpreted results. Where available, interpretations are compared to and calibrated with routine and special core analysis. In a difficult operating environment, the support and collaboration of South Oil Company staff has been crucial to the successful implementation of the West Qurna 1 Formation Evaluation strategy.
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Stratigraphy and Depositional Environment of the Upper Zubair Sandstone (“Main Pay”), West Qurna 1 Field, Iraq
Authors G.D. Harris, R.W. Wellner, V. Catterall, S. Kairo, C. Liu and Y. ChenExxonMobil and South Oil Company entered into an agreement to develop oil reserves in the “Main Pay” reservoir at West Qurna 1 field in 2010. Two cored wells, WQ1_0002 and RN_0083, were released to ExxonMobil in 2011 by SOC for core description and sampling. Various authors have interpreted the Zubair sandstones in the region to have been deposited in deltaic, estuarine and fluvial environments, but prior to reviewing these core data the dominant environments of deposition at West Qurna field were not well defined. A biostratigraphic study of the “Main Pay” reservoir indicates that most samples contain a mix of marine and terrestrial fauna. Examples of marine fauna include: benthic forams, dinocysts, echinoid plates/spines, bivalves, gastropods, calcispheres and trace fossils. Terrestrial material includes organic matter, spores, pollen, phytocuticles, amber and thin coal intervals. Abundant marine faunas occur in lower energy, deeper marine conditions whereas reduced marine fauna that is admixed with terrestrial material, occurs in higher energy, shallower water conditions. Rock types observed in core in the lower portion of the “Main Pay” include coarsening upward black claystones at the base overlain by bioturbated very fine grained sandstones which in turn are overlain by fine-grained, trough cross-bedded sandstones. Cross-bedded sandstones are sometimes capped by thin coals or lignites. Above the coarsening upward succession is a shale interval that is 10m thick with abundant marine fauna. Overlying the shale member is the middle sandstone unit. This unit is composed of interbedded thin claystone- siltstone intervals and thin to thick bedded very fine to fine grained sandstones. Bioturbation by marine organisms is common throughout this unit. Biostratigraphic and rock description show the reservoir sandstones of the Zubair “Main Pay” at the West Qurna 1 area were deposited predominantly in shallow water marine setting. Presence of thin coals, phytocuticles, roots and other terrestrial material indicate the area was periodically occupied by land plants. Well log correlations and MDT pressure data demonstrate that the “Main Pay” sandstones have good lateral connectivity. This high degree of lateral continuity together with paleoecologic and lithologic indicators of alternating marine and terrestrial deposition suggest the Zubair “Main Pay” reservoir at West Qurna 1 was deposited close to the paleo-shoreline, and most likely in a deltaic environment.
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Sequence Stratigraphy of the Mishrif Formation, West Qurna 1 Field, Iraq
Authors L.A. Yose, J.C. Mitchell, R.W. Broomhall, F. Hasiuk and C. LiuThe Mishrif formation in southern Iraq is a world class reservoir with over 100 GBO in place. The West Qurna 1 field (WQ1) is part of large N-trending anticlinal structure located near the eastern margin of the Arabian Plate, in the foreland of the Zagros fold and thrust front. An integrated reservoir study of the Mishrif is underway in the West Qurna contract area as part of a Technical Services Agreement with the South Oil Company of Iraq. The Mishrif has been under primary depletion since 1999, with intermittent disruptions due to wars. A key component of the field re-development plan is to implement a waterflood to increase reservoir pressure and improve recovery. Planning the waterfood requires an understanding of the permeability structure within the reservoir, including flow unit geometry and connectivity. A sequence-stratigraphic study of the Mishrif is underway to provide a foundation for reservoir characterization and modeling. The data currently available include data from 375+ wells (200 acre well spacing), 17 cored wells, and limited 2D seismic. PLTs and recent MDTs provide data on zonal pressures and contributions to flow, and information on scaling differences between core plug, whole core and well-test derived permeabilities. The Mishrif is ~250m thick in the WQ1 area and was deposited on a low-angle carbonate ramp. The Mishrif is interpreted to be comprised of four (4) third-order depositional sequences (1-4, oldest to youngest), that span from the Lower Cenomanian to the Early to Middle Turonian (est. 5-7 Ma duration). The sequences are stacked into a second-order sequence that records an overall shoaling-upward pattern. Sequences 3 and 4 are each capped by major exposure surfaces that form tight “caprock” intervals. The sequence boundary at the top of the Mishrif (Sequence 4) corresponds to a plate wide unconformity (the 92 Ma SB of Sharland et al., 2002). Reservoir quality variations within the Mishrif are closely tied to original depositional textures that vary predictably within the sequence framework. Grainstones, often with coarse Rudist debris, form high porosity, high permeability flow zones that will dominate flow within the reservoir. Grainstone distribution is predicable within the sequence-stratigraphic framework. Much of the reservoir is microporous with high porosity, but low permeability. The high permeability contrast within the Mishrif presents a significant challenge to waterflood management. Reservoir modeling is underway to determine the optimum development plan for the Mishrif, including waterflood. The development plan will need to be tailored to account for the observed geologic variability, using the sequence-stratigraphic framework as a guide.
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Calculation of hydraulic diffusivity and permeability at Mosul dam's lake
More LessThe space-time pattern of seismicity in Mosul reservoir is studied. The epicentral area of seismicity was considered for each three months of the monitoring period (starting from April 1986 to December 1987). Events scattered far away from the concentration area were excluded. The most prominent direction of epicentral areas are along a zone of nearly E-W direction, coinciding with the general trends of the faults in the area. However, the most characteristic feature of epicentral area is its relation with the reservoir level and number of observed events (Fig.1). The epicentral area related to October-December 1986 (area 3) is the smallest epicentral area. This is due to the recording ¬was off from the 5th November 1986 to the end of March 1987. ¬Therefore ¬the ¬hydraulic diffusivity between areas 3 and areas¬2 and¬4 ¬ was ¬not -considered¬. During 1986 it can be seen that there was an increase of epicentral area during July-Sept. although there was drop in water level in the lake. This suggests that there was a time lag between water level and pore pressure diffusion. The calculated average hydraulic diffusivity of Mosul reservoir is 9.3x104 cm2/sec. This is within the range of hydraulic diffusivity obtained in other reservoirs in the world. Talwani and Acree (1985) calculated the hydraulic
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Role of Geomechanics in improving Field Development Strategy: A Case Study from North Kuwait
By S. PerumallaThe Lower Cretaceous Zubair formation in North Kuwait comprises oil-bearing sands intercalated with shale sequences. Historically, drilling into this formation presented major wellbore instability issues that include hole pack-off, stuck pipe and logging tools, high over-pull, tight zones while tripping, and severe hole washouts. These well problems have a significant impact on well costs and timeline. Due to significant wellbore instability in these wells, the operator was drilling mostly vertical wells. However, surface constraints and production goals demanded placement of high angle/horizontal wells to maximize reservoir contact and higher production. The wells drilled in every orientation have experienced instability problems in this formation. Vertical wells have encountered major washouts and difficulties with wireline logging operations. Deviated wells have been even more unstable and often required sidetracks - greatly increasing well costs. This presentation analyzes these wellbore instability problems, including the failure mechanisms, and presents the actions taken to resolve them. A solution to these instability issues is presented, which was derived by building geomechanical models using well data, drilling problem analysis, core inspection, and core -based rock mechanical test results. We used chemoporoelastic and anisotropic geomechanical models to simulate the behavior of the Zubair formation while drilling in vertical and deviated holes to understand the wellbore instability experiences. Based on the analysis, changes in mud weight, reformulation of the mud system, and modified drilling practices were incorporated in the well plan of new high-angle wells. Success was achieved in drilling the wells and running the casing in this formation with deviations as high as 80°. The study helped to achieve a large reduction in indirect NPT due to wellbore instability. This experience is also a key learning and input for designing future complex trajectories. It was observed that a major measurable impact in the form of smoother operations and optimized well cost occurred during the drilling campaign based on recommendations from this analysis. This presentation also discusses the way forward in optimizing well completion strategy, trajectory optimization for field development and positioning of wells for optimal reservoir. The ultimate goal of implementing Geomechanics in field development is to help decision support to enhance the production at well scale and field scale with optimal balance between injection and production strategies.
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Rock fabric and pore geometry characteristics of the Mishrif Carbonates in South Iraq fields and application to the Majnoon field
More LessThe Cenomanian Mishrif–Ahmadi carbonates rock fabric versus pore-geometry and its influence of production performance in the North-Rumaila & West-Qurna oil fields have specifically been studied to be used as analogues in the Majnoon oil Field, in the absence of similar data in the latter.
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3D- Static Modeling for Carbonate Mushrif Formation in Buzurgan Field
Authors W. K. Hamdan and S. N. AL-JawadThe aim of this study is to build a Model for carbonate Mishrif Formation in Buzurgan Field. The Mishrif formation is considered to be an overall progradational marine shelf sequence; rudist shells occupied different locations on the Mishrif carbonate platform.
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Reservoir Environment Effect on Oil-Water Flow Process In Kirkuk Tertiary Reservoir
More LessIt is important for the rock samples used in laboratories to have a surface state as close as possible to that found in the reservoir. The natural state of the samples can be either preserved or restored The present study is experimental results of the oil recovery by imbibition process which made on four core samples of dimension (3.79 cm) in diameter and (6.04-7.54) cm of length, which were cored from large core samples taken from selected intervals of Avanah and Baba domes of the kirkuk tertiary reservoir.
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Flow Units Identification of the Mishrif Formation in North Rumaila Field
Authors Sameer N. Al-Jawad, Y.T. Al-Rawi and A.A.A. Al-DabajNorth Rumaila field is located about 54 km to the west of Basrah in south Iraq. The Mishrif Formation in North Rumaila is one of the most important reservoirs in southern Iraq. The present work is a reservoir unit identification of the Mishrif Formation in North Rumaila Field. The study is based on subsurface sections from 14 wells; nine of which are from North Rumaila Field and five from West Qurnaand South Rumaila.
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Impact of Carbonate Reservoir Heterogeneity on Water Injection Pilots of the Rumaila Field, southern Iraq
Authors C. Lehmann, K. Ryder, K. Almond, A. Holden, B.A.K. Al-Salim, H. Saeed and P. HenningA water injection trial in one of the giant fields of Southern Iraq has been designed in order to test water injection and sweep efficiency in middle Cretaceous carbonates. Three water injection trial areas have been identified. The areas exhibit different reservoir architectures which will help to understand the nature and mechanisms of water movement. Water injection is underway and the trial is ongoing with preliminary results available.
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Innovative Carbonate Reservoir Modeling: Example from Mishrif Reservoir, Iraq
By H. Al-QassabIntegrated reservoir characterization has a large impact on reservoir management and therefore on reservoir forecasting. The use of dyanamic data in reservoir characterization has become increasingly important, particularly when it comes to permeability modeling.
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Cementing – New procedure to ensure well integrity in South Rumaila Field utilizing Geomechanics Evaluation
Authors H. Soroush, R. Kuchinski, B. Khdier, S. Zaki, B.S. Shaheed and P. KalathingalCementing is a major factor affecting the integrity of a well for its entire life. Proper cement bonding to the casing and formation is a key measure of well integrity. Unlike most drilling related activities, the cement placed into wells must remain competent for the entire life of the well and beyond to ensure no fluid leakage even after the well has been abandoned.
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Tectono-stratigraphy and structure of the northwestern Zagros collision zone across the Iraq-Iran border
Authors M. Mohajjel and S.A. AliTectono-stratigraphic units within the Zagros orogen in northeast Iraq (foreland) and northwest Iran (hinterland) are correlated to provide an integrated map along the collision zone. Structural cross-sections across the Zagros suture zone reveal the relationships between the tectonic terranes of various ages and different origins. Terranes of oceanic affinity have accreted onto the Arabian plate during collision-accretion events that started in the Late Cretaceous. The collision resulted in closure of the Neo-Tethys Ocean and the construction of a structurally complex suture zone. Jurassic-Cretaceous deep ocean radiolarites of the Qulqula-Kermanshah terrane and ophiolitic mélange serpentinites were structurally accreted against the Arabian passive margin in the Late Cretaceous during an ophiolite arc-continent collision event. The overthrust radiolarites and ophiolitic mélange terranes initiated the development of the foreland basin overlap flysch (turbidites) and molasse assemblage on the now active Arabian margin. Paleocene-Eocene volcanosedimentary rocks of the Walash-Naopurdan-Kamyaran terrane developed as an intra-oceanic island-arc within the intervening Neotethys Ocean. They now structurally overlie the older ophiolite mélange and radiolarite terranes as a result of continued convergence onto the margin of the Arabian Plate. These younger thrust sheets and nappes have been transported over the Miocene molasse unit of the Tertiary Red Beds in flexural foreland and covered the late Cretaceous accretionary complex terrane–foreland basin assemblages. The Qulqula-Kermanshah terrane is exposed in a tectonic window at the northeastern part of the mapped area indicating that the late Cretaceous accreted terranes occur below the Walash- Naopurdan-Kamyaran thrust sheet. Late Cretaceous ophiolite massifs-bearing terranes named the“Upper Allochthon” (i.e. Gemo-Qandil nappe, 97-118 Ma) are emplaced by younger thrust sheets over the Paleocene-Eocene Walash-Naopurdan-Kamyaran terrane by out-of-sequence thrusting. Mesozoic metamorphic rocks of the hinterland including volcanic and intrusive rocks of the active Iranian continental margin (Sanandaj-Sirjan zone), collided in the Miocene due to continent-continent collision and occur in the youngest nappes and klippes along the Zagros suture zone. This is the first effort to correlate the tectonic units in this area. Detailed geological information has been compiled for the first time across the Iraq-Iran border by using the published larger scale geological maps from both regions to give correlation between tectonic units. The tectono-stratigraphic units recognized across the border. Tectonic terranes of the Zagros suture zone are identified and named. Structural cross-sections are presented to demonstrate the thrust sheets relationships and ages of convergent tectonic events due to collision along the northeast Iraq and northwest Iran border.
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Seismic- Sequence Stratigraphy of Oligo-Miocene deposits in Northwestern part of Dezful embayment (NW of IRAN)
By M. JalaliMore than a century, exploration and production of hydrocarbon in Asmari formation are continued, but nowadays most of targets are in this formation has drilled. Therefore investigation of facies variation and the role of that in quality of reservoir and searching of non-Anticline targets in Asmari formation are very important. This study was done in Northwestern part of Dezful embayment in the area between Naftshahr to Dehlouran near the border of Iraq(NW of Iran).Oligo-Miocene deposits in this area include deep marine marls, carbonates, and sandstones and evaporate. In concern with variation in facies and lithology in these deposits, this area has the potential of Non – Anticline traps and this variation has the very important effects on quality of reservoirs. In this study, detail investigations concerning sedimentology and sequence-seismic stratigraphy of these sediments were established based on new available seismic, outcrop and well data. According to this study, six 3rd order sequences and four seismic facies were determined and paleogeographic maps were drowned. Sedimentolgical and Seismic Sequences are correlated in normal and longitude transects. In these transects the potential of reservoir in was evaluated. The facies change in the basin has been illustrated in paleogeographical maps. Combination of Seismic interpretation and paleogeographical maps shows the areas that have possibility of Non-Anticline traps. This study shows that further potentials such as stratigraphic traps, Fault related traps, sub-trusts and satellite structures still exist in Asmari Fm. In this area, which should be focused on future exploration activities.
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Prediction of hydrocarbon saturation by results of Simultaneous seismic inversion in a carbonate reservoir
By Naimeh RiaziSophisticated techniques such as Amplitude Versus Angle (AVA) Simultaneous Inversion are required to provide Acoustic Impedance (AI), Shear Impedance (SI), density and compressional to shear velocity ratio (Vp/Vs) profiles in which outputs would lead to reliable reservoir discrimination. AVA simultaneous inversion has been utilized for inversion of a 2D seismic profile using one deep exploration well aimed at revealing lateral variations of the Lower Cretaceous Fahliyan carbonate reservoir (SW Iran). The purpose is also to investigate possible relationships between Lamé parameters and hydrocarbon saturation in the carbonate reservoir. Transforming of offset dependent CDP gathers to angle dependent gathers, extracting angle dependent wavelets, producing three angle gathers, construction of initial model and finally simultaneous seismic inversion are stages which have been done in this study. A direct relationship is seen between water saturation (SW) and Lamé parameters in carbonate reservoir. In contrast, indirect relationship with MuRho (MR) and SW is seen in clastic rocks. This study confirms the applicability of AVA simultaneous inversion and Lamé parameter computation in uncovering lateral variations of hydrocarbon saturation within a carbonate reservoir.
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Hydrocarbon Seepage, Spring Waters and Geobotany Surveys as Tool for Detecting Fault Extension: Abu-Jir Fault Zone Case
More LessAbu-Jir Fault Zone is a known fault and as one structural features in Iraq which extend NW- SE for long distance on the western side of the Mesopotamian basin. The feature of this fault on surface is mysterious and not clear. Surface extension evaluation of fault requires the selection of valid parameters among numerous geological factors. The present study focuses on the evidence of the existence of the fault traces on the surface such as springs, hydrocarbon seepages and geobotany in order to employ them as tools in geochemical exploration for determining fault extension. For this purposes, direct and indirect geochemical methods (spring water survey, hydrocarbon accumulation survey as well as geobotany) were carried out along Abu-Jir Fault Zone. The hydrocarbon accumulation features are existed in many types. The first is intruded massive hydrocarbon under high pressure penetrating the gypsum of Fatha Formation and exposed on surface. The second one is that the hydrocarbon intruded gypsum bed along cleavage plane but hasn't exposed on surface. The third type is light hydrocarbon ascending from depth associating the spring water and floating on the water surface. This study invested the anomaly of hydrocarbon, total dissolved solid (TDS), H2S gas emission, abnormality in growth of palm trees such as curvature and overturn the stem of palm trees and formation an isolated local aqueous environments around the springs along Abu-Jir Fault Zone for detecting the fault extension.
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Microfacies and Petrographic study for Yamama formation in Ratawi field
Authors A.H. Saleh and S. N.Al-JawadThe available thin section examination for Yamama formation in Ratawi field, Six cyclic type microfacies have been recognized for Yamama Formation ( L. Beriassian - E. Valangenian ) at Ratawi-3 (Rt -3) and Ratawi-4 (Rt-4) Wells , Those are as Follows : Peloidal packstone, Algal wackestone - packstone , Oolitic- Peloidal grainstone, Bioclastic wackestone - packstone, foraminifera wackestone and mudstone microfacies , the latter has been divided into two submicrofacies: argillaceous lime mudstone and sparse fossiliferous lime mudstone. The horizontal extension of these microfacies can be identified by studying log Characters variation and thin sections.
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Experimental Determination of Hydrate Phase Equilibrium
Authors Ehsan Kamari and M. OyarhosseinIran's proved natural gas reserves are the world's second largest reserves. Mainly, because of different climate changes and different reservoirs’ characterizations, studying the behavior of producing outcome fluids and their transportation is greatly essential. One of the main problems occurs in the gas reservoirs is related to the hydrate formation while producing from a well, either in production strings or production lines (before and after choke). Effective parameters which lead to form hydrates are: high pressure, low temperature and water presence; and therefore, the high possibility of having this phenomenon in Iranian reservoirs is quite obvious especially in the cold climates and for the gas wells. Hydrate formation in production lines and equipments will also result in many different obstacles such as: complete or partial closure in production lines and heat exchangers, erosion of the equipment, pressure reduction, etc. In this paper, by the experimental data from one the Iranian sour gas field, the conditions of hydrate formation, which will be helpful to determine the safe/unsafe zones by P-T curves, will be discussed. In addition, the final data will be compared to other correlations, as well.
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Construction of the Iraq National Gravity and Magnetic Database for the promotion of Hydrocarbon Exploration
Iraq has a long history of hydrocarbon exploration which included the regional gravity surveying of Iraq using land gravity and aeromagnetic methods. These exploration data sets have now been fully compiled into digital products which provide a wealth of new structural and sub surface information for the shallow parts of the basins (main seen by the gravity data) and deep basement structures (mainly seen by the aeromagnetic data). These responses result from a strongly magnetised basement and weakly magnetised sediments that vary from 4-5 km to in excess of 13 km in thickness in eastern Iraq. Since sediments increase in density with depth due to compaction, the gravity anomalies will be associated with tectonic movements (faulting and folding) that have laterally offset the sediment layers and densities.
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Foreland Basin System of the Northeastern Arabian Margin, Kurdistan Region, Iraq; Impact on Oil Accumulations
By B. Al-QayimPart of the convergence history of the Arabian margin during Upper Cretaceous –Pliocene time is documented in megasequence of two successor foreland basins. A close up look of this sequence’s outcrops and subsurface sections through facies and lithostratigraphic correlation as well as sequence stratigraphic analysis invoke reinterpretation and evaluation of their tectonostratigraphic origin and basin differentiation. The early one is represented by the proto Zagros foreland basin. It is developed upon obduction of radiolarite-melange suites over the Arabian margin during Late Turonian age. The Dokan oligostiginal limestone, Gulneri marine shale, and the Kometan oligostiginal-globigerinal limestone formations represent the starving, pre-flysch stage of the basin. The extensive intra-Turonian unconformity which bottoms these units marks the onset of this foreland basin formation. The major filling stage is represented by the Upper Campanian-Paleocene pelagic Shiranish marlstone and the thick, (up to 3Km.) flysch sequence of the Tanjero and Kolosh Formations. Basin inversion and shoaling is demonstrated by the punctuation of the upper part of the flysch sequence with reefal to shoal limestone of the Aqra-Bekhme (Ma’astrichtian) and the (Upper Paleocene-lower Eocene) Sinjar nummulitic limestone and the Khurmalah dolostone Formations. The red silciclastic sediments of the Gercus Formastion constitute the continental molasse filling stage. Deformation is limited and confined to the proximal areas.
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Enhanced Formation Evaluation Using High Quality LWD logs in North and South Iraq
By O. El FaroukMud invasion effects most data acquired by logging tools which in turn affects formation evaluation. In most cases WL logs ran several days after drilling the reservoir section. Weatherford performed back to back job between high quality sonic resistivity LWD versus complete wireline logging suits to study the differences in quality and allowed quantification of mud invasion effects on WL data. The study proved the excellent quality of LWD data and its ability to replace the WL which save rig time and avoid running WL radioactive source bearing density neutron tools. Also LWD provide real time petrophysical evaluation which plays important role in the decision making process before invasion takes place and mask the correct water saturation calculation.
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Open Hole Log Data Acquisition in the Challenging Well Bore Conditions of Northern Iraq
By R. KuchinskiThe tectonic stresses inherent in the earth’s crust in Northern Iraq create challenges in the drilling and completion of oil and gas wells drilled in this area. Geomechanical studies show that wellbore stability issues can arise when formations are penetrated by well bores. These well bore stability H55 issues can lead to difficulties when attempting to acquire open hole wireline log data leading to increased formation evaluation risks. These risks can be classified as follows: 1. Lost rig time due to the inability of logging tools getting to bottom. (bridging) 2. Lost rig time due to delays associated with making last minute arrangements for alternative logging methods when bridging problems become too severe. 3. Lost in hole charges associated with permanently sticking logging tools due to bad hole conditions. 4. Unsound decision making throughout the life of the well, because bad hole conditions, made the acquisition of formation evaluation data impossible. Recent advances in Formation Evaluation technology and conveyance techniques; allow for the acquisition of high quality petrophysical measurements regardless of borehole conditions or geometry. Logging systems conveyed in the drill string, or through the drill string, have a 100% chance of getting to bottom on the first attempt. With the logging tools securely attached to the drill pipe, the risk of the logging tools getting stuck is also reduced. The non-traditional conveyance techniques presented on this poster will illustrate several case studies from Northern Iraq which have led to operational optimization to formation evaluation in this area.
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Optimization Water Flood, Water Management and Plan for EOR Stage using Rantau Structure in North Sumatera Indonesia as an Example
Authors A. Badril and I. Putu SuarsanaRantau structure is located in north Sumatra basin of Indonesia, with the main hydrocarbon producing layer from Keutapang, has 33 productive layer and divided into 11 compartment (A1, A2, B, C1, C2, D1, D2, D3, D4, E1 dan E2) and has 580.25 MMbbl remaining oil in place. Rantau structure start produced in 1929, total number of wells already drilled 558. Peak primary oil production occurred in 1969 with 31,711 bopd. The oil was produced from primary stage to secondary stage on several layers and blocks. The secondary stage has been started with injecting water since 1984 with peripheral pattern and successful increasing oil production from secondary recovery until 5,500 bopd in 1988 from the previous condition 2,550 bopd in 1984 with source of water injection from sea water that has water salinity 26000-33000 ppm, this poor water injection quality directly impact problems for injection wells (plugging) and declining oil production until 2300 bopd in 1997. To increase or optimization oil production from potential layers or blocks, that some of them was not impact by secondary recovery in 1984. Water production is the main issue that can impact directly to oil production, manage water production and get more additional production from potential layer that some of them was not impact by secondary recovery from 1984. EOR division Pertamina EP planned for pilot water flood on 3 potential layers (600, 400, 770 & 800), upgrading injection & production facility (water for injection comes from water produce and treated before inject into the reservoir) and EOR stage on layers and blocks that in 1984 already impact by water injection. Kick off pilot water flood had been done in January 2010 with irregular 5-spot pattern in layer 600 and successful increase reservoir pressure and oil production until 400-500 bopd (after 3-4 months injected) from 2 producer wells form the previous condition 20 bopd. From the prediction with reservoir simulation additional reserve form full-scale water flood in 3 potential layers (600, 400, 770 & 800) can get maximum 11.65 MMbbl and additional reserve from chemical flood 6.83 MMbbl (layer 600), but for the long term EOR division Pertamina EP will be screening and restudy all production layer, because remaining oil in place still potential to optimize with secondary and EOR stage.
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