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4th EAGE North African/Mediterranean Petroleum and Geosciences Conference and Exhibition Tunis 2009
- Conference date: 02 Mar 2009 - 04 Mar 2009
- Location: Tunis, Tunisia
- ISBN: 978-90-73781-99-3
- Published: 02 March 2009
21 - 40 of 71 results
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Petroleum Geological Atlas of the Southern Permian Basin Area - overview SPB-Atlas Project – Organisation and Results
Authors J.C. Doornenbal, O.A. Abbink, H.J.M. Pagnier and J.D. van WeesThe Southern Permian Basin (also referred to as Central European Basin) is Europe’s largest sedimentary basin. It is a typical intracontinental basin that evolved from latest Carboniferous to recent times and extends from eastern England to the Belarussian-Polish border and from Denmark to South Germany. The Southern Permian Basin Atlas (SPBA) project is a joint project between the Geological Surveys of Belgium, Denmark, Germany, The Netherlands, Poland, and the UK and is being supported by a wide range of E&P companies, government licensing authorities, universities and research institutes. The aim of the Atlas is to present an overview of the results of over 150 years of petroleum exploration and research in this basin area. As this gas and oil province continues to mature and with field sizes inevitably decreasing, more and more careful data integration and geoscientific effort is required to discover new reserves. The subsurface characterization provided in the Atlas will also be of great value to governments, researchers and other individuals interested in the deep subsurface.
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Controlled-source Seismic Interferometry by Multi-dimensional Deconvolution Applied to a Laterally Varying Elastic Model
Authors J.R. van der Neut, K. Wapenaar and M.K. SenIn controlled-source seismic interferometry (SI), one typical aim is to redatum an array of sources to a receiver location. In cross-correlation (CC) based SI this goal is achieved by cross-correlating registrations at two receiver locations and summation over sources. Although a closed boundary of multi-component sources surrounding the receiver array is required, applications generally involve one-sided illumination and single source types only, which can result in spurious artifacts, erroneous kinematics and incorrect amplitudes. Therefore it can be helpful in some cases to replace cross-correlation by multi-dimensional deconvolution (MDD). In MDD based SI the reflection response is retrieved by inverting a general integral equation, which we implement in a least-squares sense. Additional advantages include improved radiation characteristics of the retrieved (virtual) sources and a relaxation of some assumptions, including the absence of loss terms and knowledge of the source wavelet. Disadvantages include the need for accurate wavefield decomposition and instabilities that might occur in the matrix inversion that forms the core of MDD. We apply SI by both MDD and CC to an elastic model with lateral variations and report slight improvements of MDD compared to CC.
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Sub-salt Imaging through Pre-stack Depth Migration – A Case Study from Offshore Egypt
Authors H. El Meligy, M. Sheath, J. Høyen, D. Renshaw, Ø. Skinnemoen, A. Issa, W. Badr, M. Abdelaty, E. Shady, M. Hårde and C. JebsenThe Middle East hosts a wide range of different geological setting, a large number of which exhibit structural complexity and hence can benefit from depth imaging. These structurally complex areas range from over thrust zones on the U.A.E - Oman border to salt structures in the Gulf of Suez and fault shadow problems in the Western Desert of Egypt in addition to offshore Egypt
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Seismic Interferometry by Multi-dimensional Deconvolution for Passive Transient Sources
Authors J.R. van der Neut, K. Wapenaar and E.N. RuigrokIt has been shown that cross-correlation of passive seismic recordings at the earth surface can yield a Green's function as if both sources and receivers were at the surface. One of the important underlaying assumptions is that the passive sources are uniformly distributed throughout the subsurface. This assumption is generally not fulfilled. We present an alternative approach that can be applied to transient passive seismic recordings registered by an array of receivers, where Cross-Correlation (CC) is replaced by Multi-Dimensional Deconvolution (MDD). We show that MDD can correct implicitly for a non-uniform source distribution and demonstrate this with a synthetic example. The main drawback of our methodology is that individual transient events need to be identified and isolated in the shot records.
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The Attenuation of a Complex Multiple Wavefield Using 3D General Surface Multiple Prediction (GSMP) – A Case Study
Authors H.E. El-Meligy, M. Sheath, J. Høyen, D. Renshaw, Ø. Skinnemoen, M. Hårde, M. Abdelaty, E. Shady, A. Cooke, T. El Melegy and B. BroussardIn this case study, we show how a new implementation of 3D surface-related multiple elimination (3D SRME) can be used to successfully predict and attenuate complex multiples, including diffracted multiples, on a dataset from Egypt’s Mediterranean Sea.
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Flow Unit Definition and 3D Petrophysical Modeling in a Complex Carbonate Reservoir, SW Iran
Authors M. Homaie and B. AlizadehAt first, Flow unit study helped to interpret Petrophysical potential of complex reservoir behavior. Core analysis such as Porosity, phi, Permeability, k, and permeability/porosity ratio (computed r35 port size in microns) and Winland r35 plot were used for the this progress. Lorenz and stratigraphic modified Lorenz plot indicated that five rock/pore units were indictable, each with an individual flow behavior called Flow Unit. They are defined as, disperse vugs (b), touching vugs (c), meso (m) and micro port size (e) and fracture (a) units. The flow units (c) and (m) constitute 55% and 20% reservoir flow respectively. In other side they are contained only 25% reservoir storage capacity. But flow unit (b) imparts 22% reservoir flow and 76% storage capacity. Different digenetic processes such as solution, cementation, dolomitization and anhydrite nodules precipitation affecting from Pyrnean disconformity have caused that flow units were irregularly distributed within whole reservoir. At second step porosity and water saturation were 3D modeled. Its results support complexity of reservoir situation depending to various Petrophysical factors. Lower reservoir, Jahrum fm, although contains better Petrophysical properties but production is mostly focused in upper reservoir or Asmari fm, where flow units (c) and (a) are generated.
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Detecting Remaining Gas Reserves Based on Coupled Modelling of Subsidence and Reservoir Depletion Processes
Authors O.A. Abbink, P.A. Fokker, A.G. Muntendam-Bos, B. Orlic and K. van Thienen-VisserDepletion of large volumes of natural gas, oil and water from hydrocarbon reservoirs may lead to movements of the Earths surface (tilt or subsidence). Observations of these movements (Interferometric Synthetic Aperture Radar (InSAR), leveling measurements) can provide a better insight on subsurface processes like reservoir compaction or the aquifer strength. A simple inversion approach does not usually provide a sensible solution due to the non-uniqueness of the inverse problem and the sensitivity of the inverse problem to small fluctuations in the data. This necessitates the use of all available prior information (geologic model, reservoir model) in the inversion procedure to better constrain the subsurface parameters. A time-dependent inversion scheme is adopted for resolving the spatial and temporal reservoir pressure drop from the surface subsidence observations. The innovative inversion method is effectively applied to one synthetic and two field cases (one from The Netherlands, one from North Africa). The results suggest that incremental gas reserves due to reservoir compartmentalization can be detected successfully.
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Hydrocarbon Production and Reservoir Management – Recent Advances in Closed-loop Optimization Technology
Authors O.A. Abbink, R.G. Hanea, E.D. Nennie and R.C.A.M. PetersPetroleum production is a relatively inefficient process. For oil production, it is, generally, less than 60 % effective on a macro scale and less than 60 % effective on a micro scale. This results, commonly, in an actual oil recovery of less than 35 %. Optimization of the production process will, therefore, have a significant impact on the supply of energy. At various locations in the world consortia have been set up to develop new technology that would help optimize the production process. In 2005 Shell, Delft University of Technology, and Netherlands Organization for Applied Research TNO have started the ISAPP knowledge centre. ISAPP aims to develop innovative solutions for petroleum production based on a closed loop integrated systems approach. The projects in ISAPP address both reservoir characterization issues and control issues. Apart from a short overview, this paper presents two cases from the ISAPP project portfolio: an optimal control example that shows how well head choke control can be used to prevent wax deposition during production; a reservoir characterization example that deals with production history matching and prediction of production from new wells.
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Stratigraphy, Sedimentology and Depositional Environments of the Late Ordovician Succession in Al Kufrah Basin, SE Libya
Authors C.R. Wilson, D.P. Le Heron, H.A. Armstrong and L. GindreOutcrops on the northern and south-eastern flanks of Al Kufrah Basin, Libya (Jabal Azbah and Jabal az Zalmah) help to improve understanding of the End-Ordovician (Hirnantian) glacial event in Gondwana. Several glacial erosion surfaces are identified, attributed to waxing and waning of ice sheets extending into the marine environment, and the sedimentary succession reveals an extensive glacial outwash fan apron deposited on a broad, shallow continental shelf. During deglaciation, fluvial and tidal cross-bedded sandstones were deposited in the southeast of Al Kufrah Basin and the entire region was overlain by Tanezzuft shales, siltstones and fine sandstones. Evidence from Al Kufrah Basin strongly suggests an extremely broad continental shelf setting during the Lower Palaeozoic, with implications for the morphology and dynamics of the ice sheet margin, and the availability of accommodation space during deglaciation. These implications must be considered when developing and refining depositional models for Lower Palaeozoic petroleum plays in the basin and elsewhere in Libya.
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Reservoir Characterisation of Deepwater Massive Sandstones – Case Studies from the Numidian Flysch and Mediterranean
Authors D.A.V. Stow, S. Riahi, M. Soussi, C. Fildes, U. Patel, S. Marsh Company LLC and M. Johansson OilfieldThe deep-water turbidite play is currently one of the most prolific and important in hydrocarbon exploration and production. Within this play, the best reservoirs are those that occur in thick sequences of deep-water massive sandstones (DWMS). These are very thick (1- >50m) sand beds or units that are devoid of primary sedimentary structures, deposited by high-density turbidity currents and/or sandy debris flows. They are commonly associated with thin-bedded turbidites, hemipelagites and other deep-water sediments, and display excellent and uniform reservoir properties and geometries. Typically, they also give rise to sand injection structures within the superjacent and laterally adjacent sediments, and display a variety of feather-edge relationships with the associated facies. The Oligo-Miocene Numidian Flysch system from both northern Tunisia and Sicily includes excellent examples of DWMS, which are the subject of ongoing investigations. This contribution aims to present an overview of what we know about DWMS, with particular focus on their reservoir characteristics, to introduce some new data on examples from the Mediterranean region, and to place the Numidian system within the context of DWMS globally.
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Giant Sandwaves from the Late Ordovician of the Tassili N'Ager, Algeria
Authors R.J. Dixon, T.L. Patton and J.P.P. HirstGiant sandwaves are described from the Ordovician outcrops of the Tassili N’Ager (SE Algeria). The sandwaves have been examined in the field and mapped using remote sensing techniques. They occur at the top of a Late Ordovician glacial sequence and unconformably overlie a sequence of pro – glacial sediments. They are in turn overlain by shelfal sediments of Lower Silurian age, mostly organic – rich, graptolitic shales that are a major petroleum source rock. The sandwaves are developed in medium to coarse grained sand and are characterised by large scale, cross sets up to 4m in height with dips of 10 – 15 degrees, dips are unidirectional with palaeo flow toward the east. The coarse grained nature and large size of the bedforms suggests the existence of strong unidirectional currents in the eastern Tassili N’Ager at the end of the Ordovician. The interaction of tidal currents and post – glacial topography in the early stages of the Silurian transgression seems the most likely explanation of these spectacular features.
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Geochemical Characterisation and Correlation of Cenomanian Turonian Sediments in Central-eastern Tunisia
Authors A. Mabrouk, H. Khaldi and I. JarvisGeochemical analysis of 254 core and cuttings samples from three petroleum exploration and development wells (Well 1, 2, and 3) in the Sfax area of eastern Tunisia, has successfully characterised the Cenomanian Fahdene Formation, and the Turonian Annaba, Bireno and Douleb members of the Aleg Formation. The cored mid-Turonian Bireno Member in the Well 3 is subdivided into two lithostratigraphic units: (i) Unit 1, attributed to a shallow subtidal environment; (ii) Unit 2, believed to represent an intertidal to supratidal sabkha environment. Vertical geochemical profiles were established for each well for 11 major elements and 7 trace elements. Chemostratigraphic correlation based on marker geochemical shifts that reflect member boundaries and the two Bireno Member sub-units has been successfully established between the three wells. Porosity seems to be strongly correlated with Ca and Mg, reflecting the importance of peri-reefal limestones and sabkha dolostones as important reservoir horizons, while clay minerals provide the main source of gamma ray response, and clay-rich beds typically represent relatively tight intervals. Chemostratigraphic studies of shallow-marine sediments such as the Bireno Member, offer considerable potential for the characterisation, subdivision and correlation of strata in petroleum basins.
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The Control of Geomechanics and Lithofacies on Fracture and Fault Permeability in Carbonates – Examples from Maiella
Authors P.A. Gillespie and B.G. WallPermeability in faulted carbonates is a key problem in exploration and production, and yet there is no existing rule base for its prediction. Fault zone properties are affected both by mechanical processes such as cataclasis and also by diagenetic processes, including precipitation and pressure solution. We have studied faults and associated fractures in a variety of limestone lithologies in the Maiella Mountain, Abruzzo, Italy and have used rock mechanical testing in order to better define the conditions of development of the faults. Combining this information with subsurface data from fractured carbonates, we propose a conceptual model for the development of carbonate fault rock permeability, based on the pore type and the loading history.
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Ability of FMS in Detecting Fractures and Other Geological Features of Asmari Fractured Carbonate Reservoir
Authors F. Khoshbakht, H. Memarian, M. Azizzadeh, G. Nourozi and A. MoallemiAsmari is a heterogeneous carbonate reservoir, which fractures play main role in hydrocarbon production. The main goal of present study is evaluation of FMS’s ability in detecting fractures and other geological features of Asmari formation. More than 380 m whole core that cut from Asmari described in order to extract structural features. FMS of this interval has also been processed and interpreted. Then, in order to evaluate and compare structural features on both core materials and image logs, the frequency logs (as frequency per 0.5 m) (for fractures, compactional features, beddings and anhydrite),orientation plots (for fractures and beddings) and aperture log (For open fractures) have been generated. Results checked by fractures data of seven wells (five image logs and two cores) of studied field and one well of neighbor field that obtained from core and image logs. Comparison of core and FMS revealed that they have excellent correlation for open fracture. FMS rarely detects filled fractures and faults of Asmari in studied well. It also is average in detecting bedding plains. Most of the 940 compaction features observed in core could not be recognized in FMS. Anhydrites in Asmari determined by FMS had good correlation with core.
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Predicting Carbonate Reservoirs, Offshore Sirt Basin, Libya
Authors K.J. Whidden, T.D. Mason, J. Iliffe and T. BevanThis paper presents a model for predicting shallow water carbonate facies in the offshore Sirt Basin. The transition between the onshore and offshore has an overall ramp geometry, cut by Cretaceous rifting, so that the offshore is deeper than the onshore. Shallow water carbonate facies are predicted to occur offshore when the onshore is non-marine to very shallow marine.
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Fractured Basement Exploration on the Algerian Sahara Platform Applied New Play Concept on the Ramade Horst
By M. BellikOn the Ramade Horst, the fractured granitic basement at a depth of 1900m has been an active tectonic zone during the Austrian phase. The Silurian is unconformably overlain by the Albian resulting in 2000m of uplift which resulted in the Silurian hot shales being downthrown along the Ramade fault and juxtaposed with the Cambrian and the Basement. The weathered material, the low permeability of the Cambrian/R3 and the Ante-Cambrian shales would be a potential top seal separating the Basement from the Cambrian. Exploration of this unconventional target in the existing fields is recommended as a mean to increase the production and extend the lifetime of the facilities. Also in the Ramade this play can be bundled with the Cambrian.
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Sequence Stratigraphy and Reservoir Characterization of the Uppermost Devonian-carboniferous in Southwest Algeria
Authors H. Abdallah, J.M. Jauregui, S. Adrianto, J. Gerard, F. Djettou, R. Afrazmanech, E. Figari, K. Nouar and N. IbrihenThe Upper Devonian-Carboniferous reservoirs correspond to new hydrocarbon plays in south western Algeria, highlighted during the recent Repsol’s exploration drilling campaign (2003-2007). Strunian and Tournaisian sandstone units produced potential gas flows from several wells essentially located in the western trend of Reggane basin. They correspond to prograding fluvial-deltaic cycles from South to North, alternating with transgressive events, prior to the global marine environment during the Upper Carboniferous. Tidal currents and storm action were the main processes which controlled sediment deposition. Reservoir characterization is the main objective of this integrated study using chronostratigraphy and 3D modelling. Biostratigraphy and field work will complete the data base in this wide area. In terms of reservoir properties, main regional quality variations seem to be related to facies changes and diagenesis effects.
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Sequence Stratigraphy and Reservoir Characterization of the Lower Devonian in the Southwest of Algeria
Authors E. Figari, J.M. Jáuregui, J. Gerard, S. Adrianto, H. Abdallah, F. Djettou, R. Afrazmanech, T. Castro and C. SakherLower Devonian reservoirs in Southwest Algeria are included in a stratigraphic interval between the so called “Caledonian Unconformity”, at the Silurian/Devonian (Lochkovian) limit, and a major regional flooding surface at the Emsian top. Three lithostratigraphic units are identified and correlated over hundreds of kilometers in outcrops and through Reggane basin. The Lochkovian/Gedinnian A & B reservoir units have been respectively deposited in tidal and foreshore environment. The Pragian/Siegenian C & D and Emsian reservoir units correspond to shoreface sandstones separated by offshore shales. In terms of sequence stratigraphy framework, they are equivalent to five 3rd Order Sequences (Vail et al., 1978), called De 1, 2, 3 4 and 5. A progressive decrease of the sand-shale ratio is expected from the SE to the NW of Reggane basin in every reservoir unit according to the overall progradation of the system and increasing marine influences. In spite of the extremely good correlation of these units around the whole area, internal heterogeneities exist due to facies associations and additional diagenetic processes.
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The Silurian Acacus Outcrop in Southern Libya – An Analogue to Jenein Sud?
Authors M. Scherer, D. Radies and R. KoehazyOutcropping cliffs of the Silurian Acacus Formation in Southern Libya were laser-scanned, and based on field sections mapped for reservoir bodies to resolve reservoir architecture. Pseudo-wells were constructed along these sections based on Jenein Sud well logs. Utilising seismic wavelet extractions accounting for frequencies and hence resolution, synthetic seismic sections were constructed to test the limits of seismic resolution for mapping Acacus reservoirs.
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Reservoir Characterization and Modeling of the Upper Ordovician Sandstones Unit in Southwestern Sahara, Algeria
More LessIn the southwestern part of the Algerian Sahara platform, the production of dry gas from Ordovician reservoir is related not only to lateral facies changes but also to the spatial distribution of natural fractures throughout the reservoir. In order to check out these assumptions, an integrated approach using a large data set, and combining several methods is used to simulate separately porosity, subseismic fault and fractures models. The main data integrated, derived from core, outcrop, wire-line logs, seismic interpretation, seismic attributes and PVT. The different concepts and approaches are related to sedimentological and structural aspects, geostatistics, sequence stratigraphy, seismic stratigraphy, and attributes generation. This leads to generate acoustic impedance which is integrated in the porosity simulation workflow as a secondary propriety, by using deterministic methods. The subseismic fault model is carried out by the means of a specific workflow, smoothing, variance and antracking attributes generations. The analysis of distribution of these subseismic faults throughout the main study field shows a closer relationship between fractures density, the curvature axes of the folds and the productivity. All these results have an impact on the planning of the future delineation wells and in the exploration-production strategy.
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