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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
41 - 60 of 71 results
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Airborne Gas Flux Mapping for Frontier Exploration
By W.J.S HirstThe deployment of LightTouch in Tunisia in 2008 will be described and sample data and results presented. The principles of operation will be described as well as the ways in which the findings can support exploration in a frontier setting.
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An Analysis of the Near Surface Using Remote Sensing for the Prediction of Logistics and Data Quality Risk
More LessRemote sensing offers the unique ability to view the earth’s surface without actually being in contact with it. Using multi-spectral satellite data and Digital Elevation Models (DEM) a workflow is presented to build a topography and a lithology based classification of the near surface. This enables the creation of logistics and data quality (surface scatter and surface velocity) risk maps. The paper draws on data from the Western Desert of Egypt including surface geological sampling and correlation with seismic data. The results demonstrate that the interpretation of remote sensing data allow the prediction of risks associated with land seismic acquisition.
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Seismic Acquisition without Cables – Choices, Benefits and Field Experience
By R.G. HeathLand seismic instrumentation is changing very rapidly and new technology can solve many of the problems associated with traditional equipment. This paper reviews the latest technology and explains how its use, alone or side-by-side existing hardware, can benefit many aspects of exploration in North Africa.
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Interferometric Rayparameter Estimation and Applications
Authors L. Velasco, R. Ferber and L. WestModern seismic surveys accumulate large amounts of data due to the increased channel and shot counts (see Rached et al., 2006). Therefore we need to move away from the manual estimation of the first breaks, needed for the production of refraction based static corrections, and instead use more automatic methods. The novel technique described here is based on the theory of seismic interferometry to the estimation of rayparameter values as function of source and receiver offset. Seismic interferometry is the process of creating secondary seismic traces (interferograms) from pairs of genuine seismograms by cross-correlation (or spectral division). One major benefit of dealing with interferograms is that of estimating delay times by picking maxima of interferograms as opposed to picking first-break travel times from the actual seismograms. One application of the estimated rayparameter is to enhance automatic first break picking. The rayparameter is estimated in the region of the first breaks and is subsequently used in the stacking of adjacent traces. The stacked traces, with an improved signal-to-noise ratio, are analyzed in place of the original traces to provide better estimates of the first break times.
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The Use of Organic Matter Study for the Reconstitution of Basin Paleogeography and the Record of Global Climate Change
Authors N. Ouertani, R. Hamouda and H. BelayouniFourteen cores have been executed across the southern part of the lake of Tunis, to trace the physico-chemical evolution of the sedimentary environment. The vertical distribution of TOC along cores, attests the existence from bottom to top, of a positive organic sequence illustrating a progressive enrichment of the sedimentary column in organic matter. From the marine stage up to the present lagoon stage, the lake of Tunis, acted as an organic matter trap. The maximum organic matter accumulation is recorded in the upper black sediments due to the development of highly anoxic conditions amplified by a marked anthropic influence. The paleo-morphology of the lagoon deduced from the organic evolution profiles interpretation of the sediment cores, indicates the existence, of two relatively deep anoxic marine areas (one at the West and one at the East) separated by a shallow marine less anoxic central area which remained constantly under the influence of strong hydrodynamic activity. The distribution of S2 (pyrolysable organic matter) is quasi-similar to that of the TOC contents. Such result clearly indicates that the organic matter associated with these sediments is homogeneous and exhibit the same origin (Tissot et Welte, 1984; Bélayouni, 1990; Disnar, 2003).
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Abundance and Diversity Patterns of Nummulite Species of Libya as Indictors of Climatic and Tectonic Changes
Authors K.J. Whidden, R.W. Jones and T. AfiffiThe purpose of this study is to look at well data from Libya and adjacent areas of North Africa to study changes in the abundance and diversity of nummulites from the Late Paleocene to Early Oligocene, in order to further evaluate tectonic vs. climatic controls on the timing of nummulite speciation.
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Quantifying Undiscovered Resource Potential
By M. ZaterThe main critical issue in the exploration is the risk associated to the play elements . Mapping the risk of the different play element and using the best basin analogues can provide a good approach to estimate the remaining hydrocarbon potential. Lack of data is a barrier. indeed the regional geology understanding and the basin exploration history of a basin is a key factor to help compensate the lacking data.Two methods of Geox estmation are used to quantify the remaining potential: the area yield method in the emerging basins and field size distribution in area with more data on a play level.
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Asset Lifecycle OPEX Modelling with Montecarlo Simulation to Reduce Uncertainties and to Improve Field Exploitation
Authors F. Verre, A. Giubileo and C. CadegianiBe cost effective at early stages of field development and during mature production it is one of the most critical steps for improving risk and uncertainties management and optimization of field exploitation during the asset lifecycle. This study shows the methodology adopted by EniTunisia to evaluate the operating expenditures (OPEX) for development projects and producing assets. This methodology adopts the concept of activity based cost (ABC) and Monte Carlo simulations to improve OPEX estimates, to influence the design optimising costs, and to reduce uncertainties throughout the exploration and production (E&P) phases from evaluation phase through mature operations up to decommissioning. This methodology has been successfully applied for both development projects and mature production. In particular when used during design phases it provides an improved OPEX cost estimates compared to percentage of CAPEX methods, which enables project and operations teams to better evaluate the feasibility and operability of a project. In addition a risk analysis will be carried out for the cost model in order to mitigate the risks and uncertainties associated with the different assumptions.
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Validation of a Semi-automatic Interpretation of Image Logs Using Two Wells from a North Africa Sandstone Reservoir
Authors R. Di Cuia, D. Ferraretti, G. Gamberoni, E. Portier and L. EscaréA new system was developed to extrapolate the maximum amount of information from the image logs by considering not only the surfaces that cut the borehole but also the textural features of the images. The main objective of developing this system was to reduce the subjectivity and the time of interpretation tasks by largely automating the log interpretation, although some level of human interaction and correction is still necessary. This approach exploits image processing algorithms to analyze borehole images and artificial intelligence techniques to classify them. The resulting implemented system produces a semi-automatic interpretation of the image logs. This software was used over the FMI logs of four wells from the north African region in order to test the validity of the results.
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Rock Type-based Characterization and Petrophysical Analysis of the Silurian Acacus Sandstones, Ghadames Basin, Tunisia
Authors T.C. Axtmann, D. Baldwin, R. Peveraro and R. VessellCareful petrographic examination of sidewall cores from Acacus sands, combined with routine core analysis, XRD and SEM data allowed for identification of 5 discrete rock families. Integration of the petrographic and wireline data, particularly NMR (CMR) data, enabled the identification of the 3 principle reservoir rocks 80+% of the time. Starting at the pore scale and discriminating discrete petrophysical Rock Types with unique petrophysical properties yields a much more robust characterization of the reservoir than can be obtained by conventional evaluation techniques. The integrated approach should reduce logging costs by enhancing the ability to identify rock types capable of storing and producing fluids and through the generation of more accurate fluid saturation profiles. Distinction of Rock Types permits more coherent interpretation of porosity-permeability, capillary pressure and electrical properties data measured in the lab. Applying these data in log analysis allows for better saturation and net pay calculations. Finally, the integration of rock types with depositional environments ultimately leads to better and more meaningful reservoir mapping which can be used to better locate future wells.
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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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