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70th EAGE Conference and Exhibition incorporating SPE EUROPEC 2008
- Conference date: 09 Jun 2008 - 12 Jun 2008
- Location: Rome, Italy
- ISBN: 978-90-73781-53-5
- Published: 09 June 2008
21 - 40 of 556 results
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Exploring in the Utah Hinge Line Using a Multi-disciplinary Approach
Authors J. Barraud, D. Bate, M. Davies, P. Houghton and P. VersnelMountainous Thrust Belt areas are typically challenging settings for oil and gas exploration. The topography and geologic complexity combine such that land based geophysical data acquisition is expensive and may leave many questions unanswered. However, the pay back from successful exploration can be large. One such successful example is the discovery of Covenant Field by Wolverine Gas and Oil, in the Utah Thrust Belt, USA in 2003. ARKeX in association with JEBCO Seismic have acquired 150 sq mi of BlueQube data, centered on the Covenant Field discovery. The objective of this work was to identify the BlueQube response of a known anticlinal structure in the thrust belt trend. With an understanding of the response from this known field, the BlueQube data is being used to develop an exploration strategy along the Thrust Belt.
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De Ruyter Field, Netherlands - Discovery and Near-field Exploration
Authors F. Blom, L. van Borren and M. BaconDe Ruyter field is located in the southern North Sea on the Dutch Continental Shelf. The discovery well was drilled in 1996 on a seismic anomaly and the well found gas with an oil rim in sandstones of Triassic age. An appraisal well drilled in 1997 on an adjacent compartment found oil without a gas cap in Permian sandstones. Subsequent exploration drilling in the area proved unsuccessful. Recently however, seismic amplitude interpretation has identified a number of prospects with a high chance of containing hydrocarbons. Two of these prospects were drilled during 2007 and both wells discovered gas. The current approach to exploration in the area is focused on validation of seismic anomalies and is aimed at de-risking drillable prospects. This paper demonstrates how validation is based on a rock physics model and observations on seismic amplitudes and flat events.
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Reservoir Characterization and Palaeo-environmental Reconstructions of Upper Carboniferous Strata in the Cleaver Bank High Area
Authors O. A. Abbink and T. B. Van HoofRecently, renewed interest in the hydrocarbon potential of Upper Carboniferous strata of the North Sea basin (and especially the Cleaver bank High area) led to an increased exploration activity in this area of the Dutch and UK offshore. The Upper Carboniferous deposits in the Cleaver Bank High area are characterized by a high lateral variability in sedimentological facies which makes prospecting for hydrocarbons difficult. Therefore, a high resolution stratigraphical framework in combination with a better insight in the distribution of sedimentological facies is needed to increase the exploration efficiency in this area. This is achieved by high resolution quantitative palynology on ten wells from the Cleaver Bank High area (Dutch offshore).
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An Evaluation of the Petroleum System - Offshore Morondava Basin, Madagascar, Based on 2D Seismic Data Interpretation
Authors M. S. Tamannai, D. Winstone, I. Deighton and P. ConnThis study addresses the regional interpretation of 2D seismic data acquired in 2003 and 2005-2006 by TGS-NOPEC integrated with satellite gravity data and source rocks modelling to analyze the petroleum system of the offshore part of the Morondava Basin (Madagascar). Seismic and satellite gravity data interpretation suggests that the western coastal basins of Madagascar can be split into two tectonic provinces i.e a western passive margin and an eastern failed rift. The structure, depositional environments and burial histories of these two provinces are quite distinct. Hence, the potential petroleum systems that occur in each province are also different. The offshore part of the basin is under-explored but found to be highly prospective. Evidences of direct hydrocarbon indicators have also been found. The burial and hydrocarbon expulsion histories for source rocks of Permo-Triassic and Mid Jurassic ages were modelled and encouraging results have been seen. The structuration happened before the oil expulsion from these source rocks which maximize the chances of finding hydrocarbons in place. Potential good quality reservoirs including predominantly sandstones and limestones have been interpreted which are covered by interbedded seals. Hence, all elements of an effective petroleum system were identified during this study.
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HC Bearing Area in the Eastern Part of the Ukrainian Black Sea
Authors S. N. Stovba, O. I. Khriachtchevskaia and I. V. PopadyukA regional investigation of the eastern part of the Ukrainian Black Sea has been carried using a vast set of regional seismic reflection profiles, including the new set of regional seismic profiles by Naftogaz of Ukraine. The drilling of Subbotina well 403 in 2006 has confirmed the huge oil and gas potential of the Kerch shelf. The recoverable reserves of the field are expected of more than 100 ml. tons of oil and 100 bln. m3 of gas. 20 large structures with closures of 50-200 km2 within the Kerch shelf have been mapped within Oligocene-Miocene-Pliocene sediments. The structure and growth history of the prospects and Subbotina structure are the same. Some of the prospects have much more size than Subbotina structure. A number of high-amplitude anticlines has been mapped and a huge Mesozoic structure of 400 sq. km in deep water depth up to 2200 m. There are strong direct hydrocarbon indicators on seismic data. According to expert appraisal, every major lead formed within the Upper Mesozoic-Cenozoic section in water depths of 100 m to 2000 m has an area of several hundred sq. km, with vertical closure of hundreds of meters, and has the potential to contain hundred million barrels of recoverable hydrocarbons.
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Digital Point Receiver Seismic Acquisition and Pre-stack Reservoir Characterization at Sulige Gas Field, China
Authors M. C. Li, S. Q. Shi, Y. B. Du, Z. H. Yao, D. X. Wang, M. B. Zhang and S. J. ChengSulige gas field (Ordos basin, Inner Mongolia) is the largest onshore gas field in China with proven gas reserves of 1.1 trillion cubic meters. This thin multi-layered deltaic reservoir of lower Permian age is very heterogeneous which prevents development drilling from high success rate (less than 60%). With respect to these characteristics and to the depth of the reservoir (3000 m), an improvement in surface seismic was mandatory more efficiently detect the sweet spots. This has been accomplished using point source - point receiver dense 2D acquisition based on explosive and digital 1C MEMS accelerometers. Data processing as well was revisited to better preserve amplitude of the CDP gathers used as input of pre-stack inversion and AVO analysis. Digital sensors proved to be more effective in preserving far offset amplitude than the conventional arrays of geophones. The resulting lithological and gas content predictions, confirmed by 30 new wells, demonstrate their effectiveness in delineating sweet spots. Success have improved by 50% and Sulige gas field has now tripled its natural gas output capacity, helping PetroChina to meet surging domestic energy demand: the field’s annual capacity reached 4 billion cubic meters by end 2007 from 1.3 billion the previous year.
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Effect of Zechstein Supergroup (Z1 Cycle) Werrahalit Pods on Prospectivity in the Southern North Sea
Authors J. R. Underhill and K. L. HunterResults of a seismic interpretation and the analysis of exploration wells in license blocks in the southern part of Southern North Sea (SNS) Quadrant 49 highlight the presence of poorly documented, lensoid Werrahalit pods within the lowermost of the Upper Permian, Zechstein Supergroup (Z1) carbonate-evaporite cycles. Their occurrence has a demonstrable effect on the accurate definition of structural traps and reserve estimates in the highly prospective Leman Sandstone Formation reservoir underneath. There remains a clear need for the zone in which the pods occur to be delimited and the effect of the Werrahalit to be accounted for when evaluating remaining prospectivity in the SNS in order to assess the exploration and production risks and rewards that their presence brings.
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Complex Fractured Carbonate Reservoir Potentials - The Impact of Dettailed Structural Analysis - The Example of the Maiella
Authors R. Di Cuia, D. Casabianca, A. Shakerley and M. MasiniThe carbonates of the Maiella Mountain (Italian Apennines) was studied to verify the consistency between forward model predictions and field measurements in a carbonate fracture sequence. The variability of depositional environments and facies, with the depositional trends orthogonal to the main present day structural axis, makes the Maiella Mountain an ideal outcrop for studying how carbonate units located in contrasting depositional environments (different textures and organization but similar structural locations) react to stress and develop fracture networks. This study was undertaken with a multidisciplinary approach and focused on the detailed acquisition and analysis of outcrop data (fracture, and facies) from sequences located in different depositional environments and structural settings. The results of the fieldwork were then compared with the fracture systems predicted by a forward modeling technique applied by restoring seismic-scale cross sections. The comparison highlights that : a) the structural model predicts correctly fracture density distribution at the field scale (km’s); b) the structural model does not fit fracture density data at the inter well-scale (100’m); c) the number of fracture sets predicted by the model is not consistent with observed data; d) fracture connectivity is higher in the field than that proposed by the model.
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Structural and Sedimentological Evolution of the Ultra-deep Gas Play Fairway - Gulf of Mexico Shelf, Texas and Louisiana (Best of AAPG)
Authors C. L. Farmer, D. H. Phillips, R. H. Benthien, D. V. Dailey, B. W. Horn and D. G. DerbeckerUltra-deep drilling activity on the Gulf of Mexico shelf is targeting a new deep gas play fairway below established older production. The fairway extends from the Mississippi delta across the Texas shelf in the section below 25,000 feet. Large relatively simple anticlines with inverted Paleogene and Cretaceous sediment packages have been identified. These packages have been mapped regionally and locally to identify isopach thicks that should be favorable for accumulation of reservoir sandstone. The main exploration risks identified for the ultra-deep fairway are reservoir presence and quality. The targeted deep structures contain sediments that exhibit internal ponded geometries with thickening axes coincident with present day anticlinal axes. Closure on many of the deep inversion anticlines formed very early as a result of initial autochthonous salt withdrawal. The deep structures are de-coupled from the shallower growth faulted section. Restoration of the structures through geological time indicates a complex interaction between salt thickness, depositional thickening and structural geometry.
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The Influence of Tectonics on Temporal and Spatial Variations in Sandbody Architecture – Cretaceous Gosau Basin, Western Calcareous Alp, Austria (Best of AAPG)
Authors D. Paton, M. Carr, H. Ortner, R. Amerman, J. Borer, P. Plink-Bjorklund, D. R. Pyles, B. Trudgill and R. J. WildThe Cretaceous Gosau deep water basin, western Austria, provides an exceptional example of syn-depositional structural influence on sandbody architecture. Significant variations in sandbody architecture are observed in both proximal to distal and axis to margin settings; these can be attributed to the basin's structural configuration. The west of the basin (proximal) is structurally confined and characterized by amalgamated coarse-grained channels. In contrast, structural deformation increases towards the east (distal) generating significantly greater accommodation space that results in both a deepening of the basin and an increase in basin width (from ~ 0.5 to 3 km). There is a corresponding change in strata to repetitive couplets of high-aspect ratio lobeform conglomeratic Mass Transport Complexes (MTCs) overlain by thinly bedded turbidites. The axis to margin variation is most pronounced in the medial portion of the basin where superb exposure of progressive rotation of strata is associated with structural growth of the basin margin fold. Immediately adjacent to the growth fold the basin fill is dominated by re-mobilized coarse grained facies and MTCs (~ 90 % of gross stratigraphy). Coeval strata in the axis are more finely bedded turbidites (coarser grained facies ~ 30 % of gross stratigraphy).
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Outcrop Characterisation of Turbidite Reservoir Analogues Deformed by Fluidisation - Implications for Reservoir Models
Authors A. Scott, O. Stanzione, A. Hurst, M. Vigorito, J. Moreau, W. Vettel and J. CartwrighThe study of post-depositional sand remobilisation and injection processes has become increasingly important in the oil and gas industry because of the considerable impact on reservoirs quality. Nevertheless, the effect of remobilisation of large volume of sand through fluidisation processes on turbidite reservoirs is still poorly understood. This creates significant issues for reservoir modelling, reserve estimation, well planning and drilling. Outcrop analogues provide essential inputs for the reservoirs modelling by constraining the geometry and petrophysical properties of modified sandbodies. The Panoche Giant Injection Complex (PGIC, Panoche-Tumey Hills, California, USA) is the largest injection complex yet documented from outcrop. This injection complex covers an extended outcrop area and crosscut about 1200 m of slope mud-rich succession with a complex system of dykes and sills. The injections are sourced from isolated slope channels, channel complexes and lobes which provide exceptionally well exposed analogues for turbidite reservoirs modified by fluidisation and injection. We describe such modifications in terms of external geometries, internal architecture and facies distribution and provide examples of how these modifications affect the reservoir properties and the distribution of porosity and permeability.
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Application of Structural Analogs to Enhance Understanding of Tectonically Inverted Settings (Best of AAPG)
Authors D. J. Reynolds and J. R. UnderhillIntegration of field and subsurface data from the Wessex Basin (UK) and Doseo Basin (Chad) has provided important new insights into petroleum prospectivity in structurally inverted settings. Using these data it has proved possible to refine models of inversion anticline development and recognition criteria for a variety of polyphase deformation scenarios. In the Wessex Basin, structures are exposed that are typically difficult to image seismically, such as the steeply dipping, highly deformed forelimb of inversion anticlines. These regions are particularly important to resolve when mapping trap geometry, field extent, and fault displacement for fault seal analyses. In all cases the inversion anticlines are related one-for-one with early rift faults, regardless of their trend and that relaying normal faults produce en-echelon inversion anticlines. Thus, en-echelon folds do not indicate strike-slip faulting a priori. In addition, maximum inversion is coincident with the center of the fault segment where maximum subsidence occurs during extension. As a result, much can be interpreted about the pre-inversion structure by mapping the inversion anticlines themselves.
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How Do Relay Ramps Influence Sedimentation in Rift Settings? A Study Combining Sandbox and Numerical Experiments
Authors W. Athmer, R. M. Groenenberg, S. M. Luthi, M. E. Donselaar, D. Sokoutis and E. WillingshoferIn this experimental study the influence of relay ramps on submarine fan deposition is investigated by combining physical laboratory experiments with fluid flow computations. The laboratory experiments comprised a two-layer sandbox model with sand and silicone put under extensional stresses to produce a rift basin with relay ramps. Its laser-scanned topography served as digital elevation model for the FanBuilder program, in which turbidity currents were modelled under different inflow directions to the rift axis. The relay ramps were found to behave as pathway for the flow if the angle of incident was small compared to the ramp incline. Wide and antithetic relay ramps with small dips can thus function as depocentres. Narrow ramps are by-passed, and the turbidity currents flow down the main gradient of the rift edge to form basin floor deposits. In order to simulate syn-tectonic sedimentation the deposits obtained from the numerical calculation were physically added to the sandbox model before and during resumed extension. Serial cuts in the analogue model after the experiments exhibited the internal structure of the modelled rift basin.
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3D Geological and Seismic Forward Modeling of a Sinuous Slope Channel Complex, Brushy Canyon Formation, West Texas (Best of AAPG)
Authors M. Tomasso, D. R. Pyles, F. L. Bonnaffé and D. C. JennetteSeismic interpretation reflects some aspects of the sub-surface geology, but the scaling of seismic images rarely shows the full geological picture. Many stratigraphic architectural elements are typically at higher resolution than the acquired seismic image, and their interpretability on seismic profiles is often limited. The ability to directly compare outcrops with seismic objects has the potential to bridge this scale-gap. Seismic forward modeling of outcrops enables the examination of known stratigraphy and depositional elements at various scales. We discuss the construction of a fully three-dimensional geologic model, based upon the Beacon Channel outcrop of the Brushy Canyon Formation of west Texas, which is interpreted as a sinuous slope channel complex. A high-resolution 3D digital outcrop dataset was acquired using a ground-based lidar scanner. The main stratigraphic surfaces and architectural elements identified using traditional field methods were interpreted directly onto the digital data, similar to seismic interpretation, providing a detailed 3D outcrop interpretation. These outcrop-constrained stratigraphic data were used to construct a 3D zone-based reservoir model. Petrophysical properties from producing analog reservoirs of similar depositional settings were assigned to lithofacies zones. Use of property transforms allowed an accurate representation of intra-zone facies asymmetry.
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Multisource Data Integration and 3D Digital Outcrop Visualization Environment - From Virtual Geology to Subsurface Models
Authors N. Lisi, S. Nardon, G. Brandazzi and E. OrsiniClassical Digital Outcrop modelling (DOM) needs to integrate all the available outcrop-based geologic features that are spatially positioned and recorded, at all scales, in 3D georeferenced environment. To do this, many different tools, with contrasting workflows, are commonly used by various modelers. To methodically integrate and quantitatively use all the various types of geological information retrievable from outcrops Eni decided to create an integrated workflow to be used in a single work-environment and able to run on any Eni infrastructure.This will allow for the user to: - Import, integrate and visualize of all kinds of georefenced data (LIDAR, GPR, Shallow Seismic, GPS measurements, wellbore logs and bottom-hole core picture, etc) in both 1D, 2D and 3D domain - interpret data in terms of surfaces and boundaries via semi-automatic polyline interpretation and picking - use sedimentary facies recognition to extract geometrical information - measure and analyse structural data (bedding and fracture plunge) both from LIDAR Clouds of Point and photodraped images A robust Virtual Outcrop has so been produced and will be expanded in the future providing the outcrops are suitable to be used as subsurface analogs.
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High Resolution 3D Mechanical Earth Model Using Seismic Neural Netmodeling - Integrating Geological, Petrophysical and Ge
Authors A. S. Wendt, F. R. Mohamed, A. Rasmussen and A. MurinedduA 3D Mechanical Earth Model (3D MEM) was built integrating geological, petrophysical and geophysical data. The 3D MEM represented the close-to-initial rock property conditions, and is an ideal basis for e.g. wellbore stability and formation integrity forecasting during initial and depleted field conditions. Using neural networking, dynamic rock properties at the wellbore level and derived from seismic inversion were integrated to obtain a "true" 3D property model. The lateral resolution of the model was driven by seismic trace density; the vertical resolution was driven by upscaled well log information. The workflow was developed for constraining regional property trends, that honor structural elements in the field, and allow to derive realistic rock property values and distributions even in areas where only limited well log information exists. The 3D MEM demonstrated that (1) Neural networking driven by seismic inversion produces rock property values that are nearly identical with the upscaled logs, which is a remarkable improvement; (2) The distribution of the rock properties is controlled by main structural elements such as faults, erosional surfaces, layering and topography; and (3) The distribution of the rock properties has a high lateral and vertical resolution even in areas where wellbore information was sparse.
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A Software Agent Based Tool for Generating and Validating Structural Interpretations
Authors B. Zhu, M. Perrin, Z. Guessoum and J. F. RainaudThe paper examines the problem of validating the geological interpretation related to a 3D structural model in view of new information coming from a drilling in progress. Considering a given geological interpretation expressed as a Geological Evolution Schema [Brandel & al. 2005], there exists definite rules that allow to determine whether the markers corresponding to two geological surfaces can be neighbours or not along a drilling trajectory. The validation problem then consists in checking the compatibilities of the various couples of markers successively met by the drilling trajectory. This is by nature a distributed problem. We propose to model it by means of a Multi-Agent System [Bradshaw 1997, Briot and Demazeau 2001] and to solve it thanks to an Eco-Problem Solving methodology [Ferber 1999]. Preliminary results are given, which demonstrate that the proposed method is sound and promising.
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A Genetic Algorithm for Optimal Blocking of Well Logs
More LessBlocking well logs is an initial and mandatory step for many processes. It is an upscaling procedure and has no unique solution. In order to find a set of "optimal blocking" for geophysical applications we propose to use a criterion based on seismic difference between synthetic seismogram computed on the fine scale logs and synthetic seismogram computed on the blocked logs. The optimisation process is performed with a genetic algorithm because genetic algorithms have the ability to solve non linear problem and to provide a set of solutions which gives an idea of the uncertainty in the model space. Thanks to the limited number of parameters, blocked well logs can be used lately in many applications such as Massive Modelling.
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M-GS - New Spatial Estimation and Simulation Models for More Precision and More Realism
Authors C. Magneron and F. PetitThe majority of the geostatistical models used in the petroleum industry are variogram-based models. The variogram enables to build effective estimation (kriging) and simulation operators by catching the mean spatial correlation inherent to a data set. Despite their popularity, variogram-based models are the subject of several criticisms. The main one is that they should not be able to handle and reproduce precisely the structural complexity of the reality. M-GS models are improved variogram-based models. They are based on an optimized determination of structural and computational parameters. They lead to more precise and/or more realistic estimation and simulation results than conventional variogram-based models. It is shown by four examples regarding gridding (2), noise removal and simulation issues.
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Earth Recursion, an Important Component in Shared Earth Model Builders
Authors S. A. Petersen and Ø. HjelleThe concept of Earth Recursion is introduced to solve critical problems of Shared Earth Model builders, especially related to their capability to express the geological evolution. The recursive approach turns out to be very efficient when addressing apparently diverse questions like natural "aging", property depth trends, incorporation of externally defined property distributions, faults within volumes and structural restoration. The concept is implemented in the Compound Earth Model builder by StatoilHydro. It is shown how the original expression for spatial distribution of properties can be written as a recursive sequence. This revision forms the basis for the implementation of Earth Recursion in the builder and demonstrated by construction of a complex property distribution reflecting the interference of on-lapping features, normal faulting and compression.
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