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68th EAGE Conference and Exhibition incorporating SPE EUROPEC 2006
- Conference date: 12 Jun 2006 - 15 Jun 2006
- Location: Vienna, Austria
- ISBN: 978-90-73781-00-9
- Published: 12 June 2006
41 - 60 of 462 results
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Modelling Study of Airwave Contribution to the CSEM Signal
By K.N. MadsenThe Controlled Source Electromagnetic (CSEM) signal received in a three layer model (air, sea and seabed) has been split into contributions from the direct wave, the signal travelling through the seabed and the direct and indirect airwave by means of three modified models run in addition to the full three layer model. The components have been split for various cases of sea depth, seabed resistivity and frequency. The results show that the contribution from the indirect airwave is of the same order of magnitude as the contribution from the direct airwave and may be even larger. It is also shown that the relationship between the airwave and the signal that has travelled through the seabed is very different depending on whether the seabed resistivity is low or high. This may influence the choice of frequency for a CSEM survey.
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Accuracy of Sharp Inversion of CSEM Data Constrained by Seismic
More LessIt is well known that sharp inversion of CSEM data constrained by seismic can produce very accurate resistivity estimation. However frequently asked questions are: is the inversion result still valid if the depth and the thickness of the layers estimated from seismic interpretation are affected by some inaccuracy? How this inaccurate depth/thickness estimation propagates through the inversion of the CSEM data? In this paper we try to answer these key questions through synthetic tests and with application to real data where a well control exists.
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AEM Combined with TDEM - A Good Tool for Mapping the Quaternary in Rugged Areas
More LessOverdeepend alpine valleys are main players in alpine geology, and therefore the main operational theatre for applied geophysicst in Austria. One of the main geological questions to be tackled is the presence and/or size of hydrogeological regimes, mostly harboured in quaternary units. The combination of Air-borne electromagnetics (AEM) and transient-electromagnetics (TDEM) proofed successful as assistance for geological mapping activities in rugged, alpine areas. Hereby the TDEM method is applied to collect deeper information than provides by air-borne systems. The starting models for TDEM inversions are constraint by multi-electrode geoelectric profiles. However, strong anthropogenic noise in alpine valleys reduces the success rate of TDEM surveys to 70%. One case study is presented, showing the thinning out of a clay rich bottom set underneath a glacial terrace.
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Improving Signal-to-Noise Ratio Using Pseudo Random Binary Sequences in Multi Transient Electromagnetic (MTEM) Data
Authors D. Wright, A. Ziolkowski and G. HallWe present multi-transient electro-magnetic (MTEM) data using a step-function and a pseudo-random binary sequence (PRBS) as the source time function. We may recover the earth impulse response from either data set and integrate the result to obtain the corresponding step response. Results show that the PRBS waveform recovers the same result as the step in current but in a much shorter time.
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Modeling Responses of a Wide-Band Drill-Hole FEM Receiver
More LessResults from numerical modeling of a eletromagnetic drill-hole probe SAMPO are presented. The modeled quantities are in-phase, quadrature, amplitude and phase of the axial components of the magnetic field. All quantities are normalized by the value of the reference field. The model used in this study is a thin plate model. The results of modeling are also compared with field data. The interpretation rules derived from numerical modeling were found to be in good agreement with the field data.
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Magnetotelluric Study along a Profile Traversing the Korean Peninsula
More LessMagnetotelluric measurements were carried out along a profile traversing the Korean peninsula, which is an important tectonic link between the continental block of China and the island arcs of Japan, to figure out the mid-crustal structure of electrical conductivity. The 2-D inversion result shows a few highly conductive anomalies and highly resistive anomalies. The highly conductive anomalies are related with the basement rocks of the Cretaceous Kyongsang basin and the sedimentary and metamorphic rocks of the Okchon belt that is a representative orogenic belt in the Korean peninsula, while the highly resistive anomalies are connected with the Cretaceous granite intrusions in the middle part of the Okchon belt and the eastern part of the Kyongsang basin. Another interesting feature is the large phase anomaly exceeding 90° in the Okchon belt. Although a reliable explanation seems to be made by an electrically anisotropic structure, it will be necessary to treat a full 3-D modeling or an anisotropic modeling to understand the complex structure of this region.
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Structure of Flysch Cover as a Result of Detailed and Semi-Detailed MT Survey
Authors M. Wojdyla, M. Stefaniuk, T. Czerwinski and A. Maksymlish Carpathians where the efficiency of reflection seismic survey is poor as a result of complex structure of the flysch cover of the Carpathian overthrust. The main aims of the surveys were recognition of Carpathians structure, but results of them were applied to studying structure and lithological differenciation of flysch cover. The meseurements were applied in two variants. First, MT sites were located separately along profile line with a step 1–3 km. In each sounding site short, 400 m continuous profiling was carried out to eliminate effects of small near-surface resistivity inhomogenities. Second, long (up to 15 km) magnetotelluric continuous profiling was carried out as an EMAP method. The quantitative interpretation was based on 1D Occam inversion and 2D NLCG algorithm. The 1D interpretation based on the least-square inversion was made too. An initial model for LSQ inversion was created based on available geological data and results of other geophysical methods. There were two ways of recognizing resistivity of flysch cover during interpretation. The first one is using the EMAP algorithm, the second one - using 2D inversion. A combination of those two methods gives good geoelectrical model.
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NL Oil and Gas Portal - Your Gateway to Dutch E&P Data
Authors A.T. Ganzeveld, M.R.H.E. Peersmann, G. Remmelts and R.R.L. AllardSince the 1990's TNO has developed POSC-related E&P data repositories. As of 1997, the Dutch government commissioned TNO to develop a national data repository for all geological data of the Netherlands: DINO. In 2001, the first online interface on that database was launched, called DINOShop. The reliability as well as the vast amount of data contained in the DINO system resulted in a steady growing number of customers and system use, improving the overall quality of data and interface.
In order to endure oil and gas production in the Netherlands, the Dutch government tries to endorse independent operators to work in the Dutch area, offshore and onshore. To emphasize the meaning of this policy, the government wants to give new players a head start: effective regulatory framework and efficient licensing procedures, good infrastructure and easy access to E&P data. In Q4 of 2005, a start was made to create a DINO-driven portal dedicated to the oil and gas industry, the NL Oil and Gas Portal. Not only is the portal a gateway to all E&P related data, it contains petroleum province reference information (in a geological atlas) and gives access to interactive stratigraphic maps, profiles and 3D models.
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Integrating Scalable Vector Graphics (SVG) in a Web-Based Seismic Data Portal
More LessAn integrated web-based seismic data portal can effectively support collaborative research in the field of geophysics. In this context, user-perceived performance and usability of the system is of paramount importance. New technologies such as Scalable Vector Graphics (SVG) can improve user interaction, but need to be exploited in a judicious manner. Scope, difficulties and necessary paradigm shifts are considered from the experience of integrating SVG in an open-source web-based seismic data portal.
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Vertical Seismic Pitfalls - Problems in Archiving VSP Data
By E.L. JackVSP (Vertical Seismic Profile) data are the poor relation of the oil exploration industry. They are neither fish nor fowl, neither simply well log data nor simply seismic and because they do not easily fit into a database set up for either of their more famous cousins, they can prove troublesome to archive, or at least troublesome to archive in their entirety. This paper describes some of the problems attached to the archiving of VSP data, by examining the variety of data (calibrated logs, velocity tables and reports, in addition to the seismic data) involved in a VSP archive. The particular problems inherent in the various data types are addressed, with special attention given to the seismic data. A recent feasibility study on loading VSP Data to the Common Data Access (CDA) DataStore is described, with an analysis of some of the problems encountered. Finally recommendations are made for archive procedures and for the media most suited to allow access to all aspects of the VSP.
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Parallel Computers from the Seismic Processing Viewpoint
By E. KurinThe analysis of present-day parallel computer architectures is done in terms of their fit to processing/imaging seismic data. The classification of processing algorithms is suggested based on their demand for computing power, required physical memory, and a number of traces contributing to each output trace. We discuss the dependence of the optimal computer configuration on the algorithms applied, as well as on the given processing sequences.
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UN Framework Classification - Towards Global Harmonization of Fossil Energy and Mineral Resources Classification
Authors P. Blystad, S. Heiberg and J.E. RitterThe UN Economic and Social Council recommended in July 2004 the UN Framework Classification for Fossil Energy and Mineral Resources (UNFC) for worldwide use by UN Member States, international organizations and regional commissions. UNFC is a tool for harmonizing existing classifications and will be helpful in improving Energy studies, Resource management, Business process management and Financial reporting. The basic criteria are Economic viability, Field project maturity and Geological knowledge which are divided into categories and subcategories. A simple codification makes UNFC applicable universally and to meet the demand for a global code for fossil energy and mineral resources. Non-conventional energy resources are emerging as supply sources, some of these blurring the boundary between mineral and energy. Collaboration with the financial community supports the development of an International Financial Reporting Standard for extractive activities. Specifications, guidelines and case studies for the classification are being developed by the Combined Reserves International Reporting Standards Committee (CRIRSCO) and UN experts for minerals and by the Society of Petroleum Engineers (SPE) for petroleum. Aggregated classes of remaining recoverable quantities, like proved, probable and possible reserves are distinguishable in UNFC.
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Re-Developing Europe's Largest Onshore Oilfield - How to Justify New 3D Seismic for Schoonebeek
Authors M.A.M. van Dongen, H. Priebe, K. Pipping, G. Warren and R. TileyThe Schoonebeek Oil Field, is currently being considered for re-development. A critical element for this re-development is an optimal positioning of the horizontal injector and producer wells in the shallow Bentheim reservoir. The original 3D seismic comprises a large structural uncertainty at reservoir level, which is expected to be significantly reduced with new hires 3D seismic. The impact of the (reduced) structural uncertainties on the well performances has been simulated in Petrel and the outcome supported the acquisition of new seismic.
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Play Concepts Based on New Stratigraphic Methods - Two Examples from the Dutch
Authors O.A. Abbink, H.F. Mijnlieff, D.K. Munsterman and R.M.C.H. VerreusselIn the Northern Offshore of the Netherlands 'Upper Jurassic' strata are mostly limited to the Central Graben and Terschelling Basin. Outside the Central Graben and the Terschelling Basin only thin veneers of these strata occur on the fringing highs as the Schill Grund High and the Step Graben. The 'Upper Jurassic' strata are an important target for the oil and gas exploration. The geology of the non-marine to shallow marine strata is complex. The combination of lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate changes, salt tectonics and structural differences hamper straightforward seismic interpretation and log correlation. A tectono-stratigraphic approach has led to the identification of three tectono-stratigraphic sequences. Sequence 1 (Callovian - lowermost Kimmeridgian) comprises the initiation of the Central Graben. Sequence 2 (lower Kimmeridgian - lower Portlandian) comprises the initiation of the Terschelling Basin. During sequence 3 (upper Portlandian - Ryazanian) the Dutch offshore is draped by a regional transgression. In this presentation the enhanced exploration potential resulting from the tectono-stratigraphic approach, is exemplified by two potential play concepts.
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Value of Seismic Information with Multiple Drilling Targets
Authors J.E. Bickel, R.L. Gibson, D.A. McVay, S. Pickering and J. WaggonerPrevious work has focused on valuing seismic information in the context of a go/no-go decision surrounding a single hydrocarbon target. While useful, this scenario fails to address the more common decision situation facing most oil and gas companies: the development of a multi-target drilling program in the face of constrained resources (e.g., capital, rigs, time). In this paper, we quantify the value of seismic information when facing some form of drilling or budget constraint. In so doing, we demonstrate that seismic information is potentially more valuable than has been shown before. We also highlight the importance of quantifying seismic accuracy in different geologic settings.
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Meso-Scale Heterogeneities in Reservoir-Scale Sand Injectite Complexes
Authors M. Vigorito, A. Scott, A. Hurst and J. CartwrightThe mesoscale structures (centimetres up to several metres sized structures) associated with the injection complexes have important effects on reservoir quality and performace. Some the mesoscale structures may act as permeability barriers while others can be preferential pathways for fluid migration with obvious effects on the vertical and horizontal permeability.
Field investigation on reservoir scale analogues demonstrates that these structures may occur in well-defined associations and that their style, geometry and distribution are related to the type and morphology of the architectural elements with which they are associated and, on a larger scale, to the internal and external geometry of the injection complex.
Mesoscale structures are recognisable both at outcrop and in core and provide insights on the main genetic processes. The structures can form or be modified during the injection process and/or during the following compaction and diagenesis of the intruded sands.
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Buried Quaternary Valleys Stand Out - Infill and Implications for Oil and Gas Fields of the North Sea
Authors T.B. Kristensen, M. Huuse, J.A. Piotrowski, O.R. Clausen and L. HambergBuried Quaternary valleys spread out beneath the formerly glaciated North Sea stand out from the surrounding sediments and provide significant challenges for seismic imaging, borehole stability and seabed installations. Through the use of a 1244 km2 3D seismic dataset and a few shallow borehole logs important details about the valley infill are revealed with implications for offshore operations. Two types of seismic infill facies are found in a number of different combinations within 12 buried valleys of very different sizes, and a conceptual model explaining the circumstances under which the valleys are likely to have been filled up are presented.
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Exploring for Stratigraphically Trapped Gas in Deep-Water Channel Deposits of the Austrian Molasse Basin
Authors R. Hinsch and S.M. HubbardGas is produced from deep-water sandstone and conglomerate of the Puchkirchen and basal Hall Formations (Oligocene-Lower Miocene) in the Molasse foreland basin of Upper Austria. The basin is mature, with >2000 wells drilled to date, and an extensive seismic reflection dataset that covers much of the paleo-basin foredeep has recently been acquired in the study area. Seismic stratigraphic analysis has revealed that deep-water sedimentation in the basin was dominated by a channel belt up to 5 km wide that transported sediment derived from the Central and Eastern Alps eastward along the basin axis (Linzer, 2001; de Ruig, 2003; de Ruig and Hubbard, 2006). New exploration models for stratigraphic traps associated with the recently developed channel model are necessary for future success in the basin. Channel abandonment and migration were important processes that resulted in a stratigraphic configuration consisting of coarse-grained sandstone and conglomerate overlain by channel and overbank mudstone. This represents an ideal reservoir architecture, including porous reservoir facies sealed by impermeable deposits, and may be an important play concept for future exploration in Upper Austria.
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Sequence Stratigraphy and Reservoir Architecture of Late Ordovician Glacially-Related Deposits, Murzuq Basin, Libya
Authors S.M. Ghnia and A. AzizThe Upper Ordovician deposits comprise two main stratigraphic units: Melaz Shuqran, and Mamuniyat, of which Mamuniyat Sandstones represent the primary reservoir targets in Murzuq Basin.
Sequence stratigraphic analysis of these deposits using well and seismic data led to the subdivision of the Melaz Shuqran into two third order sequences: Pre-Melaz Shuqran Sandstone - and Melaz Shuqran Seq.#2, and the Mamuniyat into three sequences. The Pre-Melaz Shuqran Sandstone represents the initial massive deposits in the deepest parts of the troughs (Palaeovalleys). The MZseq.2 shale comprises stacked, fining-upward parasequences. The Pusgillian Melaz Shuqran is separated by a stratigraphic break from the Upper Ashgillian Mamuniyat.
The Mamuniyat sequences correspond to a periglacial sediments and exhibit a cut and fill geometry related to successive glacial events during Hirnantian times. The Mamuniyat Sequence#1, interpreted from seismic, incised Melaz Shuqran. Seismic character suggests that it comprises massive deposits, probably coarse grained. The Mamuniyat Sequence#2 started with retrogradational parasequences culminating in Maximum Marine Flooding Surface. This was followed by progradational parasequences of the Highstand System Tracts (HST). The Mamuniyat Sequence#3 initiated with Transgressive System Tracts either very thin or absent. The HST locally displays poor reservoir quality which reflects variations in the energy of the depositional systems.
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Deep Play Exploration in the Mature Niger Delta Basin - An Appraisal of Risks and Challenges
Authors B. Olaleye, R.N. Basorun and R.N. BasorunSome attempts have been made in the past by some of the major operators to explore the deep plays with no exciting results owing to some overwhelming challenges.
A major risk factor in the branding of any deep prospect is the accuracy of the trap imaging. A spectrum of seismic methodologies has evolved over time in response to the issue of enhancing the image resolution of the deep plays.
The quality of reservoir at critical target depths is a fundamental issue in the evaluation of deep prospect for hydrocarbon volumes. The application of high resolution sequence and seismic stratigraphy has allowed the prediction of sand fairways and their environments of deposition. The evolution of petro-acoustic analysis and multi-attributes inversion in seismic stratigraphy has produced tools for the prediction with good probability, reservoir qualities and petrophysical parameters and their distribution within an area/volume of interest.
The primary challenges the explorationists face include the prediction of hydrocarbon presence in terms of type and volumes, pore pressure prediction and issues of completion and production engineering in an intimidating HPHT environment.
These challenges make deep play exploration a high risk venture as at now in the mature Niger delta basin.
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