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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
51 - 71 of 71 results
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Neural Network Permeability Prediction of Heterogeneous Gas Sands Using NMR Data
By H. GharibAnalysis of heterogeneous gas sand reservoirs is one of the most difficult problems. These formations are extremely complex, producing from multiple layers with different permeability that is often enhanced by natural fracturing. Therefore, looking for using new well logging techniques like NMR in individual bases or in combination with conventional open hole logs and building new interpretation methodology is essential to well define and obtain the representative reservoir characterizations. Nuclear magnetic resonance (NMR) logs differ from conventional logs because the NMR measurements provide mainly lithology independent detailed porosity and a good evaluation hydrocarbon potential. NMR logs can be used to determine formation permeability and capillary pressure. This paper concentrates on permeability estimation from NMR logging parameters. There are three models to derive permeability from NMR; Kenyon model, Coates-Timer model and Bulk Gas Magnetic Resonance model. These models have their advantages and limitations related mainly to the nature of reservoir properties. This paper determine permeability from BG model and introduces the artificial network model to derive formation permeability using data from NMR and other open hole logs data. The permeability results of artificial neural model and BG model will be validated by core permeability for studied well.
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Spatial Variations in Hydrocarbon Generation and Expulsion, Southern Tunisia
Authors K.C. Abdulah, T.M. Chambers and J. RobsonSince 2003 Pioneer Natural Resources Tunisia Ltd. has participated in the drilling of 42 wells in southern Tunisia, made a number of discoveries and recorded the presence of hydrocarbons in reservoirs of Ordovician, Silurian, Devonian, and Triassic age. This presentation builds on prior work, but specifically focuses on basin models aimed at exploration acreage operated by Pioneer. Subsequent to the deposition of Paleozoic source rocks, the Ghadames Basin experienced uplift and erosion related to at least 4 major orogenies. The amount of erosion varies across the acreage studied and the results from 3 of the study wells are presented to illustrate the varying impact of basin tectonics on source rock generation and expulsion. Basin models, constrained by bottom-hole temperatures and vitrinitre reflectance equivalent data, support 2 phases of hydrocarbon generation and expulsion from the Silurian Tannezuft hot shales, ie., during the Carboniferous and late Cretaceous/early Tertiary. In contrast, the Devonian Frasnian source rocks have been adversely affected by the Hercynian uplift and have only expelled hydrocarbons within the western portion of the study area. Hydrocarbon expulsion from the Frasnian source rocks occurred during late Cretaceous/early Tertiary.
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North-east Western Desert Petroleum System
Authors I. Moretti, Y. Kerdraon, M. Sami, M. Said and H. AliThe petroleum system of the South Alamein area (Western Desert - Egypt) has been evaluated in the frame of an exploration effort in the area. We will present here our main conclusions in term of source rock, maturation, kitchens and drainage
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Organic Matter Preservation and in Situ Humification in Phosphatic Pellets from Tunisian Phosphatised Sediments
Authors A. Ben Hassen, J. Trichet, J.R. Disnar and H. BelayouniThe phosphatic "pellets", from Ypresian ore of Ras-Draâ, Tunisia, are rounded grains, with some hundreds of micrometers in mean diameter. These pellets are embedded in a sedimentary, more or less carbonated or shaly, matrix. The pellets studied in this ore contain between 28 and 38 % of P2O5 and between 0.30 and 1.62 % of TOC. Surprisingly – with regards to the age of the pellets – this organic matter (OM) is very rich in humics (>75.60 % of humic C). Curiously also, the OM present in the matrix of the pellets is by far not as rich in humic compounds (>21.42 % of humic C, % of TOC). The composition of the OM of the matrix is quite usual for a 50 My old, epicontinental, never buried (over a maximum of 200 m depth), sedimentary layer. It is a low-rank kerogen. Pellets appear therefore as chemically individual bodies whose diagenetic story has been quite different, and independent, of that of their embedding sediment. These bodies have been demonstrated to have derived from fish feces (Ben Hassen, 2007).
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In Salah CO2 Geological Storage – A Sustainable Development Project
Authors N. Bounoua, R. Siaci, M. Iding, P. Ringrose, A. Mathieson and I. WrightAt the Krechba field CO2 from the In Salah gas field development is reinjected into the Carboniferous storage formation. A unique combination of monitoring techniques is used to verify safe storage at this site and to develope CO2 managment tools for other potential storage projects. We will give an overview of the latest results and future plans at Krechba.
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Reliable Decon Operators for Noisy Land Data
Authors N. Gulunay, N. Benjamin and A. KhalilInterbed multiples for noisy land data that survives the stacking process can be successfully deconvolved when operators are designed on NMO'ed and cleaned versions of the traces but are applied to NMO'ed original traces. Clean traces can be obtained by radial mixing NMO'ed (or differential NMO applied) traces in any domain where there is spatially dense distribution of traces.
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Use of Wide-azimuth Land Seismic Data for Lithology Prediction in Algeria
Authors L. Wang, F. Sutherland, N. Philip and B. TaylorIn this paper we try to discriminate lithologies by conventional AVO analysis and AIGI crossplot in a Cambro-Ordovician reservoir in Algeria. We use different AVO products including angle stacks and intercept / gradient data, and carry out analysis in both reflectivity and impedance domains. Results from angle stacks and intercept / gradient could be compared directly in the extended elastic impedance domain. Well log processing and analysis results are used to calibrate the seismic prediction. We find the result from intercept and gradient is better than that from angle stacks due to scaling issue in the far angle stacking. The apparent separation between the sand and the shale is an encouraging result that suggests AIGI crossplot can be used as a robust tool for lithology prediction and an aid to AVO analysis and calibration.
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How Should Event Amplitudes Vary Across a Seismic Gather?
Authors B. Taylor, N. Philip, L. Wang and F. SutherlandIn this paper we use forward modelling methods to estimate how amplitudes across a gather should vary in an attempt to assess the fidelity of our real seismic gathers. This may allow us to make corrections to AVO analyses that are based on possibly mis-scaled gathers.
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3D Seismic Imaging of the Acacus Play in OMV’s Jenein Sud Concession in the Ghadames Basin of Southern Tunisia
Authors N. Saidi Ayari E, P GmbH, H. Granser E, P GmbH, J. Friha E and P GmbHTraditionally, seismic imaging of the Acacus sandstone reservoirs in the Ghadames basin southern Tunisia was viewed problematic. Nevertheless, the good quality of the 3D seismic data in OMV’s Jenein Sud permit made some direct interpretation of the Silurian targets possible thanks to the use of Prestack Migration, Acoustic Impedance Inversion, 3D Visualization etc.
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Sedimentology and Sequential Interpretation of the Fluvio-marine Facies of the “Bejaoua Facies”, Northern Tunisia
Authors B. Kamel, S. Mohamed, B.I.L. Kmar and R. SamiThe Oligo-Miocene “Bejaoua Facies” Formation of Northern Tunisia can be arranged in three distinct parts which include from base to top: (1) A fully marine system characterizing the lower part (Oligocene) which is well documented at Jebel Hajra Touila , Sidi M’Himech and Touiref settings. (2) An alluvial fan, shallow marine and fluvial deposits characterize the middle part (Aquitanian)respectively in Sidi M’Himech, Hajra Touila and Touiref sections. (3) The Upper Part (Aquitanian) shows a fully fluvial system consisting of braided stream channel sandstones common to all sections. This subdivision was based (1) on sequential interpretation including a key stratal surfaces ( unconformities,Sequences boundaries SB and Maximum Flooding Surface MFS) of facies stacking patterns occur in Bejaoua Facies Formation (2)on eventuel chronostratigphic correlation with Fortuna Formation which is bounded above and below by biostratigraphically dated key strata.
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Tertiary Stratigraphy of the Offshore Sirt Basin, Libya
More LessThe onshore Sirt Basin, Libya, is a prolific hydrocarbon basin, with reserves of approximately 50 billion barrels OE, however comparatively little exploration activity has occurred in the offshore extension of this rift basin. In advance of drilling deepwater exploration wells in the basin, this study has been undertaken to understand the Tertiary post-rift section. Regional seismic data was used to define 8 Tertiary sedimentary packages through the observation of stratal terminations and geometries that indicate a re-organisation of sedimentation. Biostratigraphy has been used to pick formation tops and tie these 8 seismically defined packages to eight offshore wells. This has allowed the development of a chronostratigraphy. During the Eocene there is a well developed carbonate margin however, at top Eocene there is a major change in sedimentation from carbonates to clastics, which subsequently infill the basin. This is coincident with a pulse of ‘Syrian Arc’ inversion. This inversion appears to have continued through to the Early Oligocene and is postulated to have caused an initial phase of slumping. There is a dramatic second phase of slumping that is focussed on the NE basin margin and is likely to have a local tectonic cause. The Messinian event is represented as an erosional surface on the basin margins and lacustrine and evaporitic deposits in the basin centre. This is overlain by a very thin Plio-Pleistocene section.
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Late Barremian/Aptian Orbata Carbonate Platform, Central Tunisia – Sedimentary Record and High-frequency Cycles
Authors A. Nasri, A. Bel Kahla and M. SoussiNew stratigraphic concepts such as sequence stratigraphy (Vail at al., 1977); cyclostratigraphy (Fisher, 1986; Strasser, 1994) have determinate a way of thinking which appreciates this perception. These concepts treated in detail the dynamic behavior of sedimentary systems and prove the necessity for models using cause and effect relationships and look for interdependencies mechanisms between many variables.
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Experimental Investigation of Wettability Effect on Co-Solvent Flooding of Heavy Oil Reservoirs
Authors R. Kharrat, A. Dehghan and M. GhazanfariDespite numerous experimental studies there is a lack of fundamental understanding on how the chemical composition of a co-solvent at different wettability conditions might affect heavy oil recovery efficiency in 5-spot models. In this work a series of solvent injection experiments performed on a one-quarter five spot glass micromodel. Four groups of commercial chemicals as well as their mixtures as co-solvents were added to one light hydrocarbon solvent. New chemical procedures were applied to alter the wettability of micromodel towards strongly water-wet and oil-wet conditions. Precise analyses of the pictures provided continuously during injection processes were used to explore the solvents' displacement efficiency. It has been observed that different groups of chemicals have various effects on oil recovery based on their nature. An optimum mixture of co-solvents with greatest sweep efficiency was determined. The observations confirmed that the presence of connate water in strongly water-wet medium could improve the final recovery, while the effect of wettability in absence of connate water is at minimum. It was found that the displacement efficiency of the solvents depends on the surface wettability condition and is generally higher in strongly water-wet medium.
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HC Prospecting by Gravity Data at Shallow Sea and Plane Land
By A.A. ChernovTaman peninsula research using gravitational field anomalies. Taman feature is the presence numerous high amplitude diapiric folds to which the traps of various types are connected. The overwhelming majority of investigations folds contain traps of petroleum or gas. The experience of its prospecting and development has shown necessity of application of non-standard ways of their detection and development. This necessity is dictated by dating of productive objects to low-power of collectors partings with prevalence of jointing types of capacity, and also low resolution of seismic researches. The application specially picked up transformations at the appropriate parameters of the account has allowed to reveal of system of disjunctives breaks mainly sublatitude strike, for which the majority of deposits is dated. A gravity transformation number which has revealed latent connection of existing productive sites with gravitational anomalies is received. The forecast of perspective objects is executed on the basis of gravity researches results.
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Hyperspectral Remote Sensing in North Africa
By C.L. GoudyHyperspectral remote sensing is a technique that uses reflected solar radiation to determine the spectral response within a determined area (pixel) on the surface of the earth. Airborne hyperspectral techniques can aid in the location of macroseeps by direct detection and may be used indirectly to locate microseeps. The purpose of this presentation is to raise awareness of hyperspectral remote sensing as a direct hydrocarbon exploration tool. I will demonstrate how the technique works and show spectral hydrocarbon signatures, which aid in hydrocarbon detection. Examples of surface seeps North Africa will show how the technique is successful in locating hydrocarbons at the surface.
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Exploring for Hydrocarbons with Airborne Geophysics
By M.J. PorterDuring the period September to November 2008, Shell Tunisia Metouia conducted an airborne geophysics survey over the Metouia block acquiring gravity, magnetic, hyperspectral and trace gas detection (*LightTouch) data. We review some of the operation aspects of this work and discuss how the data will be used to help evaluate the prospectivity of the area. * "LightTouch" is a patented methodology
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The Buried Reefs Mapping by Seismic and Gravity Data
By A.A. ChernovThe prospects of detection of HC deposits in the Timan-Pechora province contact by reef structures in Ust-Pechora carbonate sediments of Upper Devonian. The interpretation of gravitational anomalies was directed on revealing and mapping of reefs and connected with by them decompactions – potential traps HC. The prospects of the decision were estimated proceeding from results of researches of gravitational fields anomalies above buried reefs structures in various oil content areas. Revealed thus by the numerous researchers of law of display of reefs in gravitational fields testify as to potential opportunities of gravity by searches of buried reefs, and allow to make a choice of techniques of interpretation of a gravitational field.
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A Detailed Seismic Characterization of a Complex, Multi-reservoir Gas Field in the Nile Delta Deep-water
Authors G. Cavanna, M. Fervari and M. GalbiatiWe present a seismically consistent methodology to address the key issues of reservoir extent, reservoir quality and internal connectivity in order to drive the building of an integrated reservoir model, in the pre-development phase of a Nile Delta deep water clastic gas field consisting of several unconnected pools of different size, most of them below seismic resolution.
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Seismic Guided Reservoir Description, Lehib, Libya – A Case Study
Authors D.C. Barkwith, A. Rafai, M. Leathard and M. FrancisThe lifting of the embargo on Libya has enabled the latest geophysical technology to enter the country and help solve exploration and production issues. One such issue is the seismic description of carbonates reservoirs such as the Lehib field in the Sirte basin. This carbonate reservoir thins and historically has proved difficult to image and interpret; to resolve this, a broad seismic bandwidth with good signal-to-noise ratio content is required. The aim is to produce a detailed 3D static reservoir model to enhance the production of the current reservoir and to explore the possibilities of satellites to this main field.
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Carbonate Facies Discrimination, a Different Look to AVO Attributes
More LessA new method of carbonate facies prediction is developed based on principal theory of seismic amplitude variation with offset, AVO. It is revealed in theory that all rock samples with similar Poisson’s ratio must align themselves along a straight line in I and G attribute space regardless of sample porosity. Thus, a group of facies with different amounts of Poisson’s ratio must generate a set of parallel lines in AVO attribute space which might be used to separate them. This was then inspected on ultrasound velocity measurements of core samples from a carbonate reservoir South -West Iran with promising results.Grainstones and packstones that are classified as structurally grain supported material are distributed along parallel lines in I and G plane and away from mud supported wackstone / mudstones. This distinct behavior might be used to separate carbonate facies based on rock’s clay content. As I and G are interface attributes, facies predicted in this way belong to the interval immediately below top reservoir interface. This is helpful especially where reservoir thickness is below seismic resolution and interval dependent attributes such as acoustic impedances fail to resolve different lithologies.
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Anisotropic PetroElastic Modeling of a fractured Tight Gas Reservoir – Case Study
Authors N. Hadj-Kacem and J. Marrauldmodeling is performed to determine the isotropic elastic properties of the rock. Afterwards, two theories are tested in order to incorporate anisotropy: Hudson’s and Eshelby-Cheng models. Finally, the main impacts of this study are the calibration of the azimuthal seismic survey acquired on the zone as well as the definition of the best positions and orientations of the future drillings.
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