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2nd EAGE St Petersburg International Conference and Exhibition on Geosciences
- Conference date: 16 Oct 2006 - 19 Oct 2006
- Location: Saint Petersburg, Russia
- ISBN: 978-90-73781-64-1
- Published: 16 October 2006
1 - 100 of 209 results
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The Role of Russian Federation and Other CIS Countries for the Natural Gas Supply to Europe
By H. RempelNatural gas accounts for about 24 % of world-wide primary energy consumption, after crude oil and hard coal. Its share has increased in the last several years. This trend is expected to continue in the future (IEA 2005). Therefore the question arises, how the increasing gas demand in Europe can be assured? This question and the role of Russia and otger CIS countries will be analysed focussing on geology of hydrocarbon basins and giant gas fields, resource base, technical viability and contract security.
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The 21st Century's Strategic Reserve of Gas Industry Development are Russian Far-Eastern and Siberian Arctic Region
Authors V.V. Rybalcenko, V.S. Parasyna, V.S. Kovalenko and V.A. SkorobogatovThere is given analysis of modern condition of geological and resource exploration of sedimentary oil-gas-bearing basins of Russia as a whole and its eastern regions and also problems in sphere of further exploring of Russian Far-Eastern and northern Siberian regions. There is conducted qualitative assessment of gas-& oil-bearing capacity’s prospectives of Yamal, Gydan, Cara sea, the Yenisei-Khatanga deflection and Russian Arctic eastern seas.There are given the authors’ assessments of potential resources of Arctic regions. There is made conclusion on decreasing of gas-bearing prospectives in eastern direction. There are given results of risk-analysis of conducting of quest-prospecting works at West-Siberian megabasin’s north. There are made conclusions that exploring and exploitation of Russian Far-Eastern and Siberian northern and Arctic regions will be gas industry development’s strategy basis in the 21st century.
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The Genetic Evolution of the Petroleum Systems of Onshore Russia
Authors S. Creaney, M.P. Dolan, R.J. Ferderer, E. Fjellanger, N.W. McAllister, B.C. South, M.A. Sullivan and J.T. Van GorselThe genetic evolution of sedimentary basins involves basin formation, fill, and maturation of rocks and fluids within that basin.
The petroleum systems of Russia cover an extreme chronology from Pre-Cambrian to Recent for both source rock deposition as well as timing of petroleum emplacement. The oldest systems are driven by Riphean source rocks which matured under Vendian load and are reservoired in the ‘snowball-earth’ Vendian glacial deposits of East Siberia.
The evolution of these systems requires an understanding of Arctic, Tethyan, Atlantic and Pacific tectonics and their interplay.
As an example, the protracted Baltica – East Siberian craton suturing in the Uralian ruptures Paleozoic plays in West Siberia but sets up source deposition and loading in the Timan Pechora basin. The collapsed accretionary crust formed in West Siberia provides the substrate for Mesozoic deposition including the prolific Bazhenov source of the Late Jurassic. Trap formation occurs in West Siberia as a result of the far field effect of the India collision re-activating this older accretionary grain during peak petroleum generation.
This talk describes the petroleum systems of the major onshore provinces in Russia, linked to their controlling tectonic and depositional events.
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Deep Model Barents-Kara Region Based on Complex Interpretation along Geotraverses 1-3 AR
Authors N.M. Ivanova, I.V. Belyev, Y.G. Leonov, Y.I. Matveev and Y.V. RoslovThe Barents-Kara Region (BKR) has a compound structure, with a thick sedimentary cover, a heterogeneous basement and is complicated by rift structures. The specific tectonic structure of the BKR is mainly associated with repeated rifting. Therefore, the major objective was to study the topography and physical parameters of the granite-gneissic metamorphic complex and to determinate the age and composition of synrift complexes. The purpose of this article is to illustrate the special features of the deep structure of the Barents-Kara Region from recent deep seismic investigations and gravity/magnetic data along geotraverses 1-AR, 2-AR and 3-AR.
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The Potential of Oil-and-Gas Content in the Transitional Areas of the Separate Regions of Russia.
By V. SavchenkoThe regional geophysical works, which were recently carried out by the use of the high technologies and equipment, extended the potential of oil-and-gas content of the different structures, explored during the preceding years.
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Sequence Stratigraphy of West Eurasia and the Greater Caspian Region - Comparisons with Arabia
Authors P.R. Sharland, D.M. Casey, R.B. Davies, C.M. Hulka, D.B. Kemp, B.R. Kilner, D. Lodola, M. Ruddy and M.D. SimmonsFive years ago we demonstrated the occurrence across the Arabian Plate of 63 synchronous Maximum Flooding Surfaces (MFS) during the Late Precambrian – Phanerozoic.
It can be demonstrated that our sequence stratigraphic model can be successfully applied to the stratigraphy of West Eurasia (e.g. West Siberia, Timan-Pechora, Volga-Urals, Barents Sea) and the Greater Caspian (including the Black Sea) regions. Both MFS and sequence boundaries can be demonstrated to be correlative within the constraints of biostratigraphy.
There are profound hydrocarbon exploration and production implications for the application of the sequence stratigraphic model that we have developed. The model provides a precise and reliable framework for correlation and mapping and the subsequent identification of petroleum system elements such as lowstand reservoirs and transgressive source rocks.
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The Aquitaine Basin, Stratigraphic and Structural History, Petroleum Geology
Authors J.J. Biteau, A. le Marrec, M. le Vot and J.M. MassetThe Aquitaine Basin is located in the south-western part of France, extending from the Gironde Arch to the north, to the Pyrenean Mountain Chain to the south. It corresponds to a triangular shape domain of 35000 km2 acreage. This presentation aims to describe the history and the dominant Petroleum System of the Aquitaine Basin including both its northern and southern domains. This is an original approach compared to most of the presentations already published.
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Interpretation and Visualization of Thrust Sheets in a Triangle Zone in Eastern Potwar, Pakistan
More LessTriangle zone plays are common in the Potwar area of Pakistan. The Potwar Basin (Figure 1) is one of the oldest oil provinces. It is located in the western foothills of the Himalayas in northern Pakistan. It includes the Potwar Plateau, the Salt Range, and the Jhelum Plain. The Khairi Murat thrust-Dhurnal backthrust triangle zone in the northern Potwar deformed zone (NPDZ) and the Joya Mair triangle zone in the southern Potwar platform zone (SPPZ) are also well documented today. These tectonic settings hold several billion barrels of reserves, and significant amounts of hydrocarbons are being produced. We interpreted the Domeli-Dil Jabba triangle zone geometry which is the result of Tertiary Himalayan collision between Indian and Eurasian plates. The thrust and backthrust phases in the eastern Potwar are the result of a northwest-southeast Himalayan compression. This is the regional triangle zone in the eastern edge of Potwar which is the result of large, regionally extensive convergent thrust sheets.
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Modern Approaches in Seismic Modeling of the LUKOIL Oil Fields in Nenetskiy Region
Authors N. Tsyganova, A. Glebov, I. Khromova, S. Goretskiy and S. YakubovskiyOil fields of the Timano-Pechorskaya oil-and-gas province (located in Nenetskiy autonomous national area of Russia) characterized by the complicated geology with sharp facies variations by lateral, steep slopes of the structures, pinch-out zones presence, large number of tectonic faults and non-anticline traps. These result in large number of ambiguousness of the geological and geophysical interpretation and, thereby, bring to difficulties in geological modeling.
Acoustic inversion results which are used in seismic interpretation process have some advantages since, firstly, both seismic and well data are used in computations. Also prior geological information can be included that leads to more stable result.
In the paper results of the acoustic inversion of the southern part of Inzyreiskoe oilfield are discussed. Single impedance cube was calculated for two target intervals – Middle Devonian terrigenous and Upper Devonian carbonate complexes. For Upper Devonian complex we managed to perform the facial classification and particularly define the high cavernosity and karsting zones. The main results for Middle Devonian complex are improvement in seismic correlation in zones with complicated interference patterns, correction of pinching out lines of sand reservoirs and definition of consolidation zones and shaling outs of reservoirs.
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New Seismic and Geological Investigation of Upper Devonian Deposits in the Izma Depression of Timan-Pechora Oil-and-Gas
Authors I.V. Petrova, R.V. Khipeli, I.N. Kerusov, A.E. Evstigneeva and A.A. MesherskyThe results of a new seismic investigation of producting Sirachoy-Domanic (Upper Devonian) deposits in the Izma depression of Timan-Pechora oil-and-gas province are presented in the report. A detailed facial analysis with extracting prospective reef objects and sheet drapes has been made on the basis of 2D and 3D seismic investigations and wells data. The basis for the facial zoning and reservoir characteristics is: examination of the thickness distribution of Domanic and Sirachoy sediment, analysis of complex seismic attributes, results of the seismic inversion in the form of acoustic impedance sections. Many Domanic reef systems and connected with them hydrocarbon traps have been found on a comparatively small area. The problems of locating exploratory drilling on the oilfields and perspective structures have been solved, the course of high-priority seismic work has been chosen, main problems of seismic investigation of the organogenous objects have been defined.
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Oil-and-gas generator - accumulative systems of the Vankorski field in the Krasnoyarsk region
Authors NATALIA Kosenkova, V.A. Krinin, N.V. Lopatin and N.A. MalishevПиролиз керогена 151 образца керна и шлама скв. № 11 Ванкорской, впервые в этом районе вскрывшей разрез средней и верхней юры, а также генетические корреляции типа «нефть-нефть» и «нефть-битумоид предполагаемой нефтематеринской свиты» привели к идентификации нефтяной яновстанской свиты и газоконденсатной среднеюрской (малышевская и вымская свиты) в качестве основных источников коммерческой нефтегазоносности.
Установлено, что нефти продуктивных пластов неокома принадлежат к одному генетическому семейству, связанному в основном с яновстанским источником нефти.
Юго-восточный Пендомаяхский очаг генерации углеводородов интенсивно функционировал в эоцен-плиоценовое время. Критический момент для яновстанско-неокомской системы наступил в раннемиоценовое время, а среднеюрско-неокомской – в позднеэоценовое. С этим периодом времени был связан активный этап формирования залежей нефти и газоконденсата в Ванкорском месторождении, который продолжается и в настоящее время. Вертикальное перераспределение в пределах Ванкорской структуры было особенно интенсивным на новейшем этапе тектонической истории района.
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Risk Quantification of Geological Object Spatial Localization
Authors N.L. Ivanova and A.I. ArapovaThe geological risk quantification technique on perspective geological objects localizating, well position foundation and hydrocarbon resources estimation is considered. It bases on spatial reliability function and risk function stochastic estimation. We use structural mapping error and capacity characteristic crosswell-space error field simulation.
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3D Data Advanced Imaging for Reservoir Properties Analysis of the Dataset from the Illizi Basin, Algeria
Authors A. Iakovlev, N. Kushnerov, D. Golovanov, V. Solomatin and A. InozemtsevA set of advanced imaging solutions such as a refraction static, LIFT technology for Pre-migration imaging, Pre-STM, Pre-SDM were applied to process the seismic data set from the area OHANET GARA TISSELIT Block 245 South (Ililizi basin) Algeria.
A key challenge of this work was to produce high-quality seismic data to improve the description of reservoir heterogeneity by using 3D seismic to guide the interpolation of sparse network consisting just 2 wells to detect subtle stratigraphic and structural features over a range of frequencies with high-resolution and precise imaging in time and depth domain.
The special efforts were done to ground-roll and mid-range velocity noise attenuation, de-multiple work, seismic amplitude preserving for subsequent AVO analysis.
A detailed delineation of potential reservoirs has been obtained by integration of seismic and log data. Key to successful integration were (1) careful inversion via Neural Network Inversion of the 3D seismic data (2) accurate seismic-to-depth conversion of the inverted impedance cube, (3) reservoir characterization using AVO and (4) coherence cube calculation. The integrated model was used to formulate a set of recommendations for subsequent drilling plan implementation. In particular some subtle anticline structures with relatively high porosity-impedance and high-amplitude fluid-saturation was identified as potential development drilling targets.
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Seismic Inversion with Quantification of Uncertainty - Case Studies from Clastic Basins
By N.C. DuttaReservoir description using seismic data has two major components: inversion of seismic data to extract attributes such as P- and S-wave velocities and bulk densities, and relate those parameters to reservoir properties, such as rock and fluid types, fluid saturation, porosity and pore pressure through fundamentals of rock physics. In seismic acquisition, we have seen considerable advancement that contributed to the quality of the seismic data, especially in the prestack domain. These are: single sensor recording (a large number of channels/offset), accurate and calibrated source and receivers and their positions, digital group forming, and towing cables at shallow water depths to minimize swell noise. All of these enable us to access surface seismic data with high S/N and fidelity that often rivals the fidelity of the Vertical Seismic Profiles (VSP).
In this paper, we use high quality seismic data to carry out Full Waveform Prestack Inversion to extract reservoir parameters, such as porosity and saturation. We use rock physics principles to constrain our inversion algorithm and then quantify our uncertainty using Bayesian approach that accounts for errors in upscaling and noise in the data and the model. We illustrate the entire procedure with examples from several basins.
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Multiattribute Analyses in Gas Field Development (Molve Field Study)
Authors Z.S. Sladovic and I.F. FutivicSubject of this paper is seismic attribute analysis as the significant tool in Molve field development. The most important application of 3D seismic data, especially in development phase is characterization of inside reservoir quality based on attribute analyses. As Molve field is complex from stratigraphical, geological and other reservoir characteristic points of view the simple seismic attribute- reservoir parameter relationship couldn’t be establish.
There are four main lithologies in Molve field, and none of them is unified. Based on sedimentological and petrophysical analyses each lithology was separated on two main parts. At this point attribute - reservoir parameter relationship was established for “litofacies I” – limestone, but that approach was still insufficient for other lithologies. Multiattribute was created (the intention is to unify process for all lithologies; so time - frequency domain attribute was created). Now the field characteristics become highly correlated with seismic multiattribute. Probability of false correlation between reservoir characteristics and particular seismic attribute was determined based on (Kaklomey, 1997). This probability for multiattribute is around 15%.
Visualization of that attribute provides easily recognition of the area with better reservoir properties
As further drilling confirm, multiattribute specially delineates residual gas accumulations.
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Seismic Inversion Results for Prediction of Properties of Complex Reservoirs
Authors D.G. Kirnos, D.E. Kashcheev and A.M. GritzenkoA combined teqnique to predict reervoir properties from seismic inversion results is considered. Classification methods, multiple regression models and neural networks are employed to obtain predicted values of reservoir properties. A case history of porosity prediction, confirmed by subsequent drilling and geophysical survey, is provided.
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Study of Reservoir Properties and Hydrocarbon Saturation from 3D Seismic
Authors V.I. Ryjkov, M.B. Rapoport, I.K. Kondratyev and A.B. KrivitskyStudy of reservoir properties and hydrocarbon saturation from 3D seismic is suggested to carry out using the combination of three independent seismic technologies:
- Optimal seismic inversion
- Seismofacial analysis basing on geosonic modeling
- HC saturation prognosis basing on frequency-dependent seismic attenuation.
The result of investigation is the geological facial model of oilfield including distribution of porosity, reservoir thickness and HC saturation.
The examples obtained on oilfield in Western Siberia are provided.
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RT-Matrix Method for Direct Problems of the AVO
More LessTo advance the mathematical and computational treatments of direct problems of the AVO involving multilayered media, a new derivation of the RT matrix method (reflection-transmission matrix method) is presented. This method allows calculate the complete dynamic response including both the displacement and stress fields in a layered half-space. The stability and accuracy of the direct problem’s solution are studied by numerical experiments on the model data. The synthetic seismogram building is realized. Based on actual data performance capabilities of the AVO inverse problems’ solution are investigated using iterative selections of models of the medium. It is shown that selection of models of the medium using a realized algorithm allows tracing the alterations of the medium parameters (bed thicknesses) between key wells.
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Recovery of Thin Formation Properties through Seismic Amplitude Inversion
Authors G.A. Maksimov, G.N. Gogonenkov, S.A. Kirillov and V.A. LarichevThe paper proposes an effective method to recover a thin-formation structure (thinner than seismic wavelength) through amplitude inversion of surface-recorded low-frequency seismic events with due regard for downhole acoustic log data. As a result, spatial structure and properties of individual thin beds in a geologic unit are recovered between the wells at a scale less than seismic wavelength.
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Rock Properties of Complex Lithologies - Similarities Between Offshore Brazil and West Siberia
Authors O. Klarner, S. Klarner and B. UjetzRift related basins represent an important part of hydrocarbon bearing areas worldwide. In basins containing large flood basalts, volcanic rocks occur as major sediment source for potential reservoir sandstones. Examples from Cretaceous sediments in the Santos Basin, offshore Brazil, and Jurassic sediments in the West Siberian Basin are presented here. In contrast to pure quartz arenites, these sandstones contain a significant amount of feldspars, lithics and their diagenetic products which have a significant impact on reservoir properties. Although diagenetic products may preserve porosity at relatively deep burial, they normally reduce permeability and therefore production rates. The acoustic and elastic properties of the reservoirs are also affected. These types of complex reservoirs are rarely documented. Therefore, learning from case studies helps to understand similar reservoirs and to predict their properties in order to optimise exploration and production potential.
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The technology of integrated speed-spectral interpretation of filter-capacitor characteristics and petroefficiency of reservoirs in three-dimensional cross-borehole space petroefficiency of reservoirs in three-dimensional cross-borehole space
Authors M. Afanasyev, E. Kopilevich, E. Davydova, A. Petrov, A. Goncharov and J. AfanasyevaПрогнозирование ФЕС коллекторов в межскважинном пространстве производится по данным сейсморазведки и ГИС на основе их спектрально-временного и псевдоакустического преобразований с определением количественных спектральных по оси частот и времён атрибутов, а также псевдоакустической скорости. Эти сейсмические атрибуты сертифицируются по принципу наилучшей корреляции с ФЕС и интерпретируются комплексно с использованием искусственных нейронных сетей, на выходе которых распределение в пространстве удельной ёмкости и гидропроводности коллекторов.
Технология обладает патентной чистотой и успешно внедрена в сейсмогеологических условиях Западной Сибири и Тимано-Печорской НГП
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Modeling and Inversion of Sonic P and S Wave Velocities at the Mallik 5L-38 Gas Hydrate Research Well
Authors J.G. Rubino, C.L. Ravazzoli and J.E. SantosUsing an interval of real log data from the Mallik 5L-38 Gas Hydrate Research Well, we estimate empirical relations for some mechanical properties of the gas hydrate frame. This is an important problem for geophysical exploration in gas hydrate bearing sediments, a subject which has not received as much attention as it deserves from the researchers in this field.
The theoretical velocities used to model the sonic logs are computed using a Biot-type formulation combined with known petrophysical models for shaley sandstones.
The empirical results are also applied to obtain estimates of gas hydrate saturations at a different depth interval from sonic and density log data, showing the applicability of this approach.
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Authenticity of Hydrocarbons Deposit Prediction Rise on a Base the Integrated Model of Field
Authors A.P. Sorokin, S.O. Slobodyanyuk and V.V. SirchenkoAuthenticity of prediction of hydrocarbons deposit, at the searches and exploring of hydrocarbons reservoirs by geophysical methods, relies oninforming of every method in concrete geological condition and is characterized by the factor of definiteness 0
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Prestack Interpretation in Interpreter's Environment
Authors M.M. Popov, D. Mair and N. Xuan NamIn the conventional approach of interpreting stacked seismic, the goal of a prospect mapping is to define the geologic framework and stratigraphy. Correlating well data with poststack seismic attribute volumes provides some hints to possible hydrocarbon presence and reservoir quality away from wells. However these characterized volumes have already blended the seismic response of different offsets, and can be further distorted by the stacking process. To understand the composition of the framework that is lithology and pore fluid away from well control requires prestack interpretation.
For decades, interpreters have used poststack seismic volumes as their primary data type due. In contrast, prestack seismic data has been very difficult to access from a standard seismic interpretation environment, partly due to hardware limitations. Its use has been limited to specialists such as AVO experts and seismic processors. Nowadays, with access to affordable hardware providing sufficient disk space and memory to handle huge prestack datasets, the potential to work with prestack data exists. Most importantly, new geophysical tools permit everyday interpreters to view and analyze this prestack seismic data in an integrated interpretation environment.
This paper describes a case study whereby analyzing prestack data in the interpreter's environment helps to see clearly differences in the prestack response to hydrocarbon or water at the reservoir.
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Structure of the Jan Mayen Fracture Zone, Norwegian-Greenland Sea - Insights from the New Aeromagnetic Survey JAS-05
Authors L. Gernigon, O. Olesen, J. Ebbing, J.O. Mogaard, C. Pascal, S. Wienecke, J. Mondt, O. Norvik, M. Sand and O. SteenIn order to better constrain the Cenozoic evolution of the Norwegian-Greenland Sea and contiguous margins, a new aeromagnetic data (JAS-05 survey) was acquired in the Eastern part of the Jan Mayen Fracture Zone during autumn 2005. We present preliminary results and interpretation of this survey. The main faults, structure and magnetic anomalies have been re-interpreted using a systematic comparison between bathymetry, gravity, magnetic patterns and available seismic data. Magnetic chrons have been identified and has been used to provide accurate Cenozoic ages for the oceanic basement and overlying sedimentary sequences, identified on seismic. The new magnetic survey and integrated study allow us to discuss the tectonic and magmatic evolution of the Jan Mayen Fracture Zone and its geodynamic implications
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Forecast of the Mineral-Raw Prospective Areas, That Is According to Results of Integrated Processing and Interpretation
Authors S.A. Kaplan, E.N. Cheremisina, A.S. Kireev, V.I. Galuev and S.S. MalininaThis paper presents the methodology of integrated processing and interpretation of research data on control geophysical profiles. The general scheme of integrated analysis of geological information is adduced. Methods of constructing environment models based on data from separated geophysical methods are represented, methodology of getting block-layered locally-homogeneous model of Earth’s crust is proposed. Results of forecast of favorable zones for formation of mineral deposits and conditions on Eastern Siberia and Far East profiles are represented
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The Geodynamic Model Central - Aldan of Region (CAR) and Prediction
More LessThe offered operation has allowed on the basis of a dynamic model Central - Aldan of region, using the program COSKAD 3D, to carry out prediction of plants under search operations on ore gold
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Deep Structure and Geodynamics of the Pre-Mesozoic Sedimentary Successions within the Northern West Siberia
Authors S.L. Kostyuchenko, V.A. Erkhov and V.Y. BulavinovThe data derived from deep CDP, DSS and conventional seismic study of the territory of Northern West Siberia give evidences to suggest different stages of evolution of the region. The plate tectonics took place up to the Middle Palaeozoic. The interaction of a mantle plume and earth crust causes the large-scale sedimentary basin formation during the Middle-Upper Palaeozoic. The rift occurred in the end of the Palaeozoic up to Early Triassic time, and after these, general subsidence of the lithosphere was resulted by formation of the West-Siberian sedimentary province. We conclude that, in the area of study, 4-6 km thick carbonate-terrigenous sedimentary complex exists beneath the Mesozoic to Cenozoic oil and gas bearing cover.
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Deep Structure of the Pre-Mesozoic Consolidated Basement of the West-Siberian Geosyneclise and “Deep” Geological-Geophysical and Geodynamic Factors of Hydrocarbon Deposits Localization.
Authors A.S. Egorov, V.N. Muchin, A.I. Atakov and E.Y. ErmolinResults of geological-geophysical modeling of the consolidated basement of the West-Siberian geosyneclise with the use of modern-day regional CDP seismic profiling data are presented. The estimation of potentialities of the multifactor prognostic technology with the aim of “deep” factors of hydrocarbon deposits localization is considered.
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Technology of MT Data Interpretation and Results Obtained at Geotraverses
Authors V.P. Bubnov, E.D. Aleksanova and A.G. YakovlevTechnology of magnetotelluric (MT) data interpretation and results of MT investigations along geotraverses in Eastern Siberia are considered. New information about resistivity structure of the sediments and consolidated crust was obtained. Thick conductive Riphean layers, supposed to be good collectors, were revealed in Irkenyevsky aulacogen and Tungusskaya syneclise. It is shown that in geoelectric conditions of Yeniseisky range MT method allows to study only the upper 10 – 15 kilometers. Two types of the Earth’s crust are determined within the Siberian craton. Crust of the first one contains crustal conductive layer and corresponds to hydrocarbon perspective areas. In the crust of the second type this layer is not developed.
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Seismography as Effective Problem Solving Method in Ore and Oil Geology and in the Siberian Earth's Crust Study
Authors A. Salnikov, V.L. Kuznetsov and V.M. MarkovДля повышения геологической эффективности сейсмических исследований, в том числе проведенных в прошедшие годы, предлагается использовать способ сейсмической томографии на временных задержках волн в первых вступлениях, зарегистрированных при работах методами отраженных и преломленных волн.
Для решения обратной задачи применяются специальные двухмерные временные поля, что позволяет объединить в единую систему времена прихода волн при наблюдениях разной детальности, в том числе при отсутствии корреляционной увязки отдельных годографов. В качестве интерпретационной модели принята непрерывная двухмерно-неоднородная модель.
Разработанная технология сейсмической томографии широко применяется при решении различных задач нефтяной и рудной геологии и при изучении глубоких зон земной коры Сибири: изучение самой верхней гетерогенной части земной коры в рудных районах, что позволяет прогнозировать новые рудные узлы и изучать их структуру; изучение структуры и строения, а в комплексе с данными бурения, и состава палеозойских нефтегазоносных образований в Западной Сибири; позволяет освещать внутреннюю структуру глубоких зон земной коры, обеспечивая выявление волноводов, зон дезинтеграции, глубинных разломов.
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Depth-Velocity Model Based on Regional Seismic Data
Authors V.V. Kasianov and I.U. KulakovaThe calculation of reflected compressional wave velocities based on regional seismic survey data for further depth conversion and the compressional wave field study aimed to identify blocks and areas in Yamal-Nenets autonomous district for detailed prospecting at insufficient deep drilling information.
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Which Parameters Control Seismic Attenuation in a Fractured Porous Rock?
Authors B. Gurevich, M. Brajanovski, R.J. Galvin and G. LambertTo analyse which parameters (fracture length, thickness or spacing) control the frequency dependence of attenuation and dispersion, we consider two theoretical models. The first model considers fractures as planes of weakness (or highly compliant and very thin layers) of infinite extent. In the second model fractures are modelled as thin penny-shaped voids of finite radius.
In both models attenuation exhibits a typical relaxation peak around a normalised frequency of about 1. This corresponds to a frequency where the fluid diffusion length is of the order of crack spacing for the first model, and the crack diameter for the second. This is consistent with an intuitive understanding of the nature of attenuation: when fractures are closely space, the waves reflected/scattered by cracks interfere with each other, with the interference pattern controlled by the fracture spacing. Conversely, if fracture length is smaller than spacing, then fractures act as independent scatterers and the attenuation resembles the pattern of scattering by an individual crack.
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The interpretation of petroefficiency of fractured reservoirs
Authors D. Reznikov, E. Kopilevich, E. Davydova, M. Afanasyev and A. PetrovПрогнозирование коэффициента нефтепродуктивности трещинных коллекторов производится по данным сейсморазведки МОГТ, ГИС, испытаний скважин на основе количественных спектрально-временных и псевдоакустических преобразований сейсмических преобразований сейсмической записи и кривых ГИС с последующим интегрированием спектрально-скоростных атрибутов с использованием искусственных нейронных сетей для определения коэффициентов емкостной дифференциации (КЕД) глинистых трещинных коллекторов, интегральной удельной емкости (q) карбонатных трещинных коллекторов КЕД и q коэффициента нефтепродуктивности Кнпр = Q/Δp, где Q – дебит нефти, Δp – перепад давления в скажине. Технология обладает патентной чистотой и успешно внедрена в сейсмогеологических условиях Западной и Восточной Сибири.
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PS-Wave Azimuthal Anisotropy in a North American Carbonate Basin
Authors S. Roche, B. Mattocks, J. Li and S. RonenIn an onshore example from a US carbonate basin, an embedded multicomponent test exhibits good PS-wave signal quality at the depth of interest, and all the expected characteristics of converted waves in azimuthally anisotropic media. In particular, there are clear azimuthal polarity reversals on the transverse receiver component, separated by null amplitudes defining the symmetry planes of the natural coordinate system; azimuthal velocity variations on the radial component then distinguish the specific symmetry plane aligned with maximum horizontal stress. The cumulative anisotropy is in good agreement with regional horizontal stress from borehole breakouts.
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Applying the Side-View Seismic Location Method (SVSL) in Complicated Geological Conditions
Analyzed are results of applying the Side-View Seismic Location method (SVSL) in combination with other seismic methods to solution of main problems of HC exploration in complicated geological settings of Orenburg region and Kuyumba oil field in East Siberia. Combination of SVSL and other seismic methods (CMP) allows solve such problems as building a structural model, mapping of fractured zones and fluid migration pathways. By way of examples considered is solution of these problems for the south of Cis-Ural through, particularly, for the Akobinsk area featuring a material effect of salt-dome tectonics. The second part of the paper presents results of applying SVSL to mapping the open fracturing of rocks, refining the geological model of Riphean complex of East Siberia (Kuyumba oil field) in combination with the structural seismic (2D CDP), and identification of fractured zones which are promising drilling targets. Proposed is a technique for identifying reefogenic structures in the depth interval of Riphean complex. This allows substantially improve the reliability of geological predictions when selecting optimal drilling sites to achieve maximum oil flow rate in exploratory wells.
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Noise Amplitude Analysis of Collocated VectorSeis and Geophones Groups
More LessОдним из требований, предъявляемых заказчиком работ к качеству полевого материала, является контроль максимально допустимого уровня случайных шумов (до первых вступлений) на профиле. В большинстве случаев максимально допустимое значение шума для данной площади обычно известно либо по результатам предыдущих работ, либо по результатам предварительно проведенных опытных работ, и задается в микровольтах.
В последнее время все большее распространение начинает получать сейсморазведка с использованием точечных многокомпонентных цифровых акселерометров. Главным отличием данного метода является регистрация полного волнового поля и отказ от группирования сейсмоприемников.
Многокомпонентный цифровой сейсмоприемник представляет собой акселерометр, регистрирующий ускорение, в отличие от стандартного геофона, измеряющего скорость смещения частиц грунта. Вследствие этого при работе с акселерометрами нельзя использовать максимально допустимый уровень шумов, рассчитанный для групп геофонов. Часто, при применении акселерометров на конкретной площади мы не имеем достаточного количества статистических данных для определения уровня шумов в микрогалах. В данной работе исследуется возможность использовать для определения этого уровня максимальный шум групп геофонов.
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Time Processing of Multicomponent 3D Survey Acquired in West Siberia, Russia
Authors Z. Tlemissova and D. YanchakMulticomponent data acquired by TNK-BP in 2005 was the first 3D/3C survey shot in West Siberia, Russia. This study covers the main issues and challenges of the 3C processing and the behavior of PS waves in the subsurface geology of West Siberia as compared to P waves.
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Use of a Vertical Component of Seismic Shear Waves
Authors YU.P. Bevzenko and V.A. ZozulyaWide-scale implementation of multi-component seismic exploration is constrained by subsoil users’ doubt in its efficiency due to lack of information acquired in field conditions and confirmed by drilling and field operation results. In such situation shear & converted wave data obtained in the process of conventional seismic exploration with monotype P-waves is useful to justify multi-component seismic prospecting. The most favorable conditions for studying a vertical component of shear and converted waves are found in prePolar areas with a high-velocity 500 m thick permafrost layer on a surface of the interval under study. Use of additional information allows to define requirements to projects of multi-component seismic exploration performed using borehole explosions and nonexclusive sources of a vertical action, as well as, in some cases, solve geological tasks at relatively shallow depths. A result of the research works performed since 1997 is a recommendation to realize a rational land multi-component 2D seismic exploration based on a highly-mechanized 3-component telemetric system “MarshLine” being manufactured by a Russian company “Sea Technology” for working in transit zones.
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Multicomponent OBC (4C) Time Imaging over Pamberi, Offshore Trinidad
Authors T.D. Johns, C. Vito, R. Clark and R. SarmientoResults from the P-P and P-Sv prestack time migration of a four-component (4C) OBC seismic swath test acquired in 2004 over the Pamberi area in Block LRL offshore Trinidad, are presented. A description of the processing applied to the multicomponent seismic data, through curved-ray anisotropic Kirchhoff prestack time migration for both the compressional P-wave and mode-converted PSv-wave, is provided. Mode-converted shear-wave data acquired from 4C surveys allow for imaging where conventional seismic data are perturbed due to the presence of shallow gas or fluid in the pore spaces of the rock. Furthermore, mode-converted shear waves propagate with a different raypath than that of the compressional wave, thereby providing an alternative illumination of the subsurface target. As both the P-wave and S-wave record independent measurements of the same subsurface, more reliable rock properties can be uniquely determined, allowing for improved reservoir characterization and lithology prediction. A conventional towed-streamer 3D was acquired over the Pamberi area in 2003, but failed to resolve adequately the target reflectors comprising the reservoir under the main growth fault. Therefore, the purpose of the 4C survey was to evaluate the potential of long-offset multicomponent technology for resolving stratigraphic interpretation in areas of complex challenging geology.
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Shear-Wave Seismic and VSP with Virtual Sources
Authors A.V. Bakulin and R.W. CalvertShear-wave seismology holds great promise but always remains small niche activity due to a variety of operational and subsurface limitations. In this study we demonstrate that the Virtual Source method can overcome many of these limitations and revive shear-wave seismology. With an array of sources at the surface this method allows us to obtain a Virtual Shear Source at the location of each downhole geophone in a well. Firstly, in certain cases it allows us to generate pure shear-wave energy without P-wave contamination using conventional P-wave sources even in a marine environment. Secondly, we can construct SS images of the subsurface even through a complex near-surface for which the velocity model is unknown. Thirdly, we can control the polarization. All this is at a price of placing geophones in the subsurface and making downhole recordings. This price tag is expected to decrease with greater use of permanent downhole monitoring, cheap wells and instrumented oilfields.
We will show examples of SS images obtained through a complex near-surface and show shear-wave checkshots generated with the help of P-wave sources even in a marine environment. This
development may lead to a renaissance of shear-wave seismology especially for permanent seismic monitoring.
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Full-Wave Imaging Projects Using Multicomponent Digital Sensors in Russia
Authors T.E. Galikeev, A.P. Zhukov, I.P. Korotkov and A. BurlakovTwo 3-D multicomponent datasets were acquired in Western Siberia and analyzed. The same type of digital 3-C accelerometers used for data recording were used with different types of sources (dynamite and VibroSeis). Data analysis suggests that the source and near surface conditions can impact the quality of recorded converted wave data, while the vertical P-wave component is of a high quality and equally interpretable when compared to geophone data acquired in the same area. Absorbing properties of the overburden in Western Siberia limit frequencies of converted waves up to 20-30 Hz depending on intensity of near-surface frost penetration. Therefore, an adequate effort should be spent on generating low frequencies in the source’ spectrum. Production sweeps rarely start below 10 Hz due to equipment restrictions and applied sweep tapers further reduce full energy effort spent on low frequencies. Absence of low frequencies in the source manifests itself by a very narrow frequency spectrum of converted waves in the data acquired with VibroSeis. Although, during processing and utilizing data rotation (data were recorded with 3-C digital sensors) the quality of C-wave stacks were improved.
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Advances in Multicomponent Exploration
Authors S. Grion, S. Roche, J. Gibson, B. Mattocks, S. Ronen, H. Watt and K. PoplavskiiMulticomponent (MC) seismic data are gaining importance as an exploration tool for difficult targets. Vector acquisition of seismic data in three orthogonal directions (3C) allows for the recording of both compressional (P) and shear (S) waves. These respond differently to fluid and solid combinations in the subsurface and the joint use of both wave modes provides many potential benefits. Applications relate to structural imaging (seeing through gas clouds, better fault definition, improved near-surface resolution), fracture characterization (density and orientation), fluid discrimination and estimation of lithology (sand/shale, dolomite/anhydrite). Furthermore, vector recordings allow for improved noise attenuation with respect to conventional P-wave records.
This paper provides an overview of multicomponent technology and focuses on the techniques and advances that are improving viability and includes theory and practical examples of how multicomponent technology is improving the ability of the industry to find and produce more oil and gas.
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Minimization of the 4C Alford Data Matrix for Non-Orthogonal PS-Wave Reflection Modes
By J.E. GaiserJoint inversion of P-waves (compressional waves) and PS-waves (converted P to S-waves) is becoming more important for pore pressure prediction, time-lapse effects and characterizing the stress and fracture state of reservoirs. However accurate results will depend on how well the principal S-wave (shear-wave) directions can be determined in anisotropic media. PS-wave reflection coefficients in azimuthally anisotropic media produce a set of non-orthogonal amplitude modes that can complicate the estimation of principal S-wave directions.
The purpose of this study is to show that a conventional Alford rotation provides the correct principal direction for non-orthogonal PS-wave modes in azimuthally anisotropic media when reflection coefficients vary azimuthally. Fast and slow S-wave components of 4C (four component) Alford data are examined in terms of azimuthally anisotropic PS-waves reflection coefficients. Results for orthorhombic media illustrate that the Alford data matrix is diagonally dominant when properly aligned with the principal directions. A synthetic data set consisting of a 5-layer model representing vertical fractures of different orientations demonstrates that conventional Alford rotation and layer stripping will give the correct principal directions when the off-diagonal traces are minimized.
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Numerical Modelling of Seismic Character of Depositional Sequences
Authors B. Gurevich, A. Gerhardt, G. Lambert, C.M. Griffiths and C. DytAnalytical and numerical models of sediment transport and deposition are being increasingly used to investigate controls on sediment variability in depositional sequences. In this paper we consider the stratigraphic response to eustatic sea-level (amplitude and period) and local controls, such as sediment supply and subsidence, and their impact on the resulting reflectivity along a notional well situated in an outer neritic location. The development of key stratal surfaces shows a systematic relationship with respect to the various stages of an aggradation curve.
The results of seismic modelling indicate that seismic events related to sediments deposited under the influence of systematic changes in sea level show a distinctive pattern that approximates the derivative of the original seismic wavelet, while their amplitudes indicate the degree of evolution along the stages of the aggradation curve. If appropriate conditions are met, this distinctive character can be used to distinguish such seismic events from the ones associated with unconformities or layers not directly associated with these controls.
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3D Finite-Difference Modeling of Borehole Wave Propagation
Authors V.A. Tcheverda, V.I. Kostin, D.V. Pissarenko and G.V. ReshetovaFinite-difference (FD) method for 3D simulation of sonic waves propagating in a borehole and surrounding 3D heterogeneous elastic medium is presented. It is based on explicit second-order staggered grid FD scheme that solves the first-order elastic wave equations in cylindrical coordinates. Special modification of Perfectly Matched Layer (PML) for cylindrical coordinate system is developed and implemented. Essential 3D nature of the waves processes for realistic models claims necessity to use parallel computations. Parallelization is performed on the base of domain decomposition approach and implemented under Message Passing Interface (MPI). Result of numerical experiments is presented.
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Wave Propagation in Rocks and Granular Materials Modelled as 1D Heteromodular Elastic Medium
More LessWe consider 1D non-stationary essentially nonlinear dynamic problem for heteromodular elastic medium. Heteromodular medium reacts differently to the tension and compression and therefore presents strongly nonlinear behaviour at infinitisemal deformations. It is subjected to the harmonic force which was "switched on" at zero moment of time. We consider the case when the difference in elastic moduli for tension and compression is small, and construct asymptotical solutions for large times. The analytical results are verified numerically. We construct both near and far-field asymptotics, analyse spectral properties of the problem.
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Tube-Wave Interaction with a Fluid-Filled Circular Fracture of a Finite Radius
Authors S.R. Ziatdinov, A.V. Bakulin and B.M. KashtanTube waves in boreholes are used for characterizing formation properties and hydraulic properties of fluid-filled fractures and permeable zones intersecting wellbores. At low frequencies there is a wellknown approximate formalism describing reflection/transmision of tube waves on layer boundaries and infinite fluid-filled fractures. However for fractures or washouts of finite size one can only use numerical methods such as finite difference that are time-consuming and do not provide physical insights.
Here, we extend existing formalism to analyze reflection/transmission of tube waves on a circular fluid-filled fracture/washout of an arbitrary finite size. We break the problem into three tasks. First, conversion of tube waves into guided waves is modeled using method of Kostek et al. (1998). Second, we derive new analytical solution for reflection of diverging guided slow wave from a fracture tip using 2D approximation. Finally, we derive conversion coefficient describing transformation of imploding guided into tube waves in a borehole. Combining three solutions, we obtain simple analytical representation of a total wavefield in the borehole as a superposition of upgoing and downgoing tube waves generated at the fracture intersection and borne by incoming guided waves and their multiples. New solution is in good agreement with finite difference computations.
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The Analysis of Microseisms Spectrum at Prospecting of Oil Reservoir on Republic Tatarstan
Authors E.V. Birialtsev, I.N. Plotnikova, I.R. Khabibulin and N.Y. ShabalinAre represented the results of the analysis of a microseisms spectrum, which is received at prospecting of small oil reservoirs on territory of Republic Tatarstan. For this analysis it is used the method based on revealing of peak abnormal high amplitude in a range of 1-10 Hz. Are discussed two alternatives hypothesis about nature of this peak over oil reservoirs. Based on experimental data it is shown, that the hypothesis of resonant amplification of microseisms in the resonator between daylight surface and oil reservoir is more adequate. It is shown, that it is can observe oil reservoirs, the border a sedimentary cover - the crystal and of other geological structures, such as active fault, as a peak on microseism spectrum.
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Microseismic Monitoring of Hydraulic Fracturing - Physical Fundamentals of Interpretation
Authors S.A. Shapiro, C. Dinske and E. RothertSeveral basic dynamic processes related to propagation of hydraulic fracturing modify the effective stress in rocks and, therefore, they are relevant for triggering of microseismicity. For instance, these are the creation of the new fracture volume, fracturing fluid loss and its infiltration into reservoir rocks as well as diffusion of the injection pressure into the pore space of surrounding rocks and inside the fracture. Here, using real data we show these processes can be seen from features of the spatio-temporal distributions of the induced microseismicity. Especially, the initial stage of the fracture volume opening as well as the back front of the induced seismicity starting to propagate after termination of the fluid injection can be well identified and used for reservoir engineering.
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Seismic Location of Emission Centers - A New Technology for Monitoring the Production of Hydrocarbons
Proposed is a technology of Seismic Location of Emission Centers (SLEC) – a new modification of passive seismic monitoring of processes taking place in reservoirs in course of production. SLEC technology features the use of standard seismic equipment for the surface acquisition of seismic wavefield and application of “Slionkin Focusing Transform” (SFT) which provides high spatial selection (focusing), noise immunity, and prompt interactive processing of results of seismic observations. Presented are results of industrial testing of the SLEC technology for monitoring hydrofracturing operations, fluid injection performed to maintain the formation pressure and natural fluid dynamics in reservoir during production.
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Synthesis of 30 Years of Seismicity Induced by the Exploitation of the Lacq Gas Field
Authors G. Sénéchal, T. Bardainne and N. Dubos-SalléeDuring the last 30 years, more than 1700 earthquakes have been recorded near the Lacq gas field. This large database has been recorded by a local network of 16 1-component seismometer from 1974 to 1997. Considering this seismicity as the brittle response of stress variations due to the depletion, we determine a synthetic model of deformation for the reservoir. This model is constrained by the spacial distribution of seismological events and by the geometry of the main faults obtained from 3D seismic data. This geometry appears strongly coherent with the analog model of deformation proposed by Odonne et al. (1999). Moreover, we observe a temporal evolution of the spacial distribution of the earthquakes: they are mainly located in the center of the structure during the first years and, later, we clearly observe a spacial migration of the events, showing a ring pattern distribution. Based on this various results, we propose a model of deformation of the Lacq gas field. New data, recently recorded with the new local network deployed in the vicinity of Lacq, are coherent with the proposed model.
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Earthquakes and Hydrocarbons
By M. PuckettIs there any scientific connection between earthquakes and hydrocarbons? Do geophysicists in the energy industry become involved in the study of seismic events? Geophysicists in the petroleum industry do monitor seismic events as they relate to hydraulic fracturing and reservoir monitoring. Borehole seismology in the energy sector involves detection of seismic events on a microseismic, i.e., Richter magnitudes less than 0.0, scale. Hydraulic fracture monitoring using microseismic techniques operational setup issues and two case studies are presented in this discussion.
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Theory of the Virtual Source Method
Authors A.V. Bakulin and V. KorneevThe Virtual Source method (VSM) has recently been proposed as a new practical approach to reduce distortions of seismic images caused by shallow heterogeneous overburden. VSM is demanding at the acquisition stage because it requires placing downhole geophones below the most complex part of the heterogeneous overburden. Where such acquisition is possible, however, it pays off later at the processing stage because it does not require knowledge of the velocity model above the downhole receivers. This paper demonstrates that VSM can be viewed as an application of the Kirchhoff-Helmholtz integral (KHI) with an experimentally measured Green’s function. Direct measurement of the Green’s function ensures the effectiveness of the method in highly heterogeneous subsurface conditions.
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Virtual Source Method for Imaging and Monitoring Below Complex Near-Surface
Authors A.V. Bakulin and R.W. CalvertWe propose the Virtual Source method (VSM) that is designed to provide imaging and monitoring in case of very complex overburdens.
VSM acknowledges upfront that our data inversion techniques are unable to unravel the details of the complex overburdens to the extent necessary to remove the distortions caused by them. Instead VSM suggests placing downhole geophones below that most complex overburden while still exciting signals with a surface sources. Receivers may sit in horizontal or slanted wells, which may be producers/injectors or dedicated sidetracks and first applications include drilling such wells below complicated near-surface, basalt or salt layers. By performing data-driven redatuming with measured Green\'s functions, these data can be recast into complete downhole dataset with buried Virtual Sources located at each downhole geophone. This step can be effectively thought of as a time reversal and it's remarkable feature is that velocity model between sources and receivers is not required to perform it. Therefore not only we can image through the overburden of any complexity, but also we can effectively monitor even if those overburdens change between the surveys. We illustrate VSM by applying to synthetic and monitoring 4D field case.
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The Correction of the Surface Heterogeneity Irregularity at Processing 2D/3D Seismic Data (Gazprom,Western Siberia)
Authors A.D. Avramenko and E.K. VyalkovaThe processing of seismic data of complex shallow structures over the territory of Yamal-Nenets autonomous district requires specific software and techniques to correct the shallow structure heterogeneity. The application of the proven processing techniques depends on the cost, Seismic-geological conditions and on the improved procedure. The article describes the theoretical view points on the heterogeneity correction and gives the examples of processed data results with allowance to the shallow structure heterogeneity over certain areas of Western Siberia, Gazprom.
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Velocity Determination in 3D Seismic
Authors A.A. Shevchenko and B.R. ZavalishinVelocity analysis still remains a weak link of 3D seismic inheriting the profiling (2D) technologies. The development of modern 3D seismic resulted in significant growth of number of channels in acquisition systems and use of migration of raw seismograms, that making it possible to enhance the resolution provided that a velocity model of medium is specified adequately. However it is difficult to count upon a noticeable increase in detail level of a survey where velocities are determined and, hence, smoothed, over several-kilometer-long arrays.
The proposed approach to determining seismic velocities is based upon two principles: Controlled Directional Reception (CDR) – i.e. slant stacking along a plane and the theory of diffraction by aperture. Amplitude analysis on sets of stacked traces computed with increasing aperture makes it possible to measure the first Fresnel zone radius of any regular wave that is proportional to its effective velocity. The ray parameters and effective velocities of all regular waves measurable at any point of a single 3D seismogram make it possible to construct more detailed depth-velocity model. Robustness of the first Fresnel zone radius measurement is discussed here.
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Seismic Imaging with and without Velocity
Authors T.J. Moser and E. LandaA new type of seismic imaging, based on Feynman path integrals for waveform modeling, is capable of producing accurate subsurface images without precise knowledge of a reference velocity model.
Instead of the usual optimization of the semblance objective function, a weighted summation over all representative curves avoids the need of velocity analysis, with its common difficulties of subjective and time consuming manual picking.
The path integral imaging can be applied to stacking to zero-offset, time- and depth migration.
In all these cases, a properly defined weighting function plays a vital role, to emphasize contributions from traveltime curves close to the optimal one and suppress contributions from unrealistic curves.
The path integral method is an authentic model-independent technique, in the sense that there is strictly no parameter optimization or estimation involved.
Synthetic and real data examples shows that it has the potential of becoming a fully automatic imaging technique.
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True Amplitude Thin Slab Multi-One-Way Inversion - Application to Marine-Type Seismic Data
Authors D.A. Kiyashchenko, R.E. Plessix, B.M. Kashtan and V.N. TroyanTrue-amplitude wave-equation migration can be obtained by using a modified imaging principle and a multi-one-way scheme. In order to avoid the artifacts of the multi-one-way scheme due to the turning rays, a thin-slab approach is investigated. A wave-equation inversion formula is proposed to recover the reflectivity. Under the high-frequency approximation, it is similar to the pseudo-inverse formula. This formula is applied on a synthetic and real example.
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Innovative Depth Imaging in Complex Permafrost - The Taglu 3D PSDM Project
Authors G.L. Reed, P.H. Chang and K.F. BrittleInnovative new velocity model building approaches developed for a recent, successful anisotropic 3-D prestack depth imaging project from surface through the complex permafrost layer above the Taglu Gas field are presented. Discovered and delineated in the early 1970's by Imperial Oil , Taglu is a giant gas-condensate field located onshore in the Mackenzie Delta region of Arctic Canada, approximately 120 km north-northwest of the City of Inuvik.
The final Taglu APSDM seismic volume is considered a greatly improved structural image over previous time imaging products. Structural imaging now conforms to the available field well data, with the mapped seismic structure closing for the first time on the known GWC depth without adjustment. In addition, DHI image quality has improved substantially and independent confirmation of DHI structural conformance is now clearly demonstrated directly in the seismic data.
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Gaussian Beams Based True Amplitude Imaging
Authors V.A. Tcheverda and M.I. ProtasovWe present an original approach of true amplitude seismic imaging by means of weighted summation of multi-shot multi-offset data. In order to compute these weights one should trace Gaussian beam starting from some current point within target area towards acquisition system. The special choice of Gaussian beam provides possibility in advance to take into account geometrical spreading and illumination condition for specific acquisition system. Global Gaussian beam regularity enables one to deal with central ray field with any kind of singularities.
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Depth Imaging of 2D Data Using 3D Grid-Based Tomography
Authors A. Zarkhidze, T. Grechishnikova and D. YanchakA description of the workflow of successful application of 3D grid-based tomography to 2D seismic data in the area of a complex weathering zone. This approach allows to incorporate refraction wave-based velocity information into a depth velocity model to properly handle actual raypaths through the near surface.
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Correcting Long-Wavelength Traveltime Distortion in the Presence of Inhomogeneous Permafrost Using Grid-Based Tomography
Authors T. Grechishnikova, A. Zarkhidze, D. Yanchak and R. MayThis paper describes a process of depth-velocity model building in the shallow subsurface using grid-based tomography in order to properly compensate for the long-wavelength distortion in the traveltimes.
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VSP – Beyond Time-to-Depth
Authors B.E. Hornby, J. Yu, J.A. Sharp, A. Ray and Y. QuistVSP or Vertical Seismic Profile was originally designed and is currently primarily used, to give us time-to-depth for seismic well tie. Beyond time-to-depth a number of possibilities exist. Recently, there has been considerable interest in VSP imaging, with extensive surveys being acquired both on land and offshore. Modeling studies using full-waveform finite-difference method (FDM) show us what we can image for a particular acquisition geometry and geology, with best image results seen with 3D VSP surveys incorporating a large VSP array in the well and a 2D source pattern acquired using a surface seismic shooting vessel. Traditionally, VSP imaging has been implemented using surface seismic processing algorithms. However, the VSP geometry poses its own challenges and unique opportunities. In this article we explore some imaging methods to attempt to take advantage of the VSP geometry. In addition we discuss the use of permanent in-well seismic sensors for reservoir monitoring.
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A Method for 3D Surface-Related Multiples Prediction in Case of Coarse Sampling
Authors E. Kurin, M.S. Denisov and D. LokshtanovA method for 3D surface-related multiple prediction (SRMP) is suggested. It uses both raw common source gathers and azimuth-dependent inverse-NMO corrected traces of a stack cube, or a CMP gather, to produce common-source gathers of multiples. The application of the method is illustrated on a complex real dataset.
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Robust Methods of Adaptive Seismic Multiple Suppression
Authors M.S. Denisov, M.A. Polubojarinov and D.B. FinikovOne of the widely used approaches to multiple suppression is a two-step scheme. In the first step, multiples are predicted. In the second step, multiples are adapted to the input data with matching filters and subsequently subtracted. It is known that a non-stationary adaptation is usually required. A method for computation of smoothly varying matching filters is proposed. The behavior of the non-stationarity is parameterized with decomposition of the variations into a set of smooth basic functions. Besides, substantial improvement is usually achieved by application of multichannel adaptation. Such approach requires a multichannel version of the Levinson’s algorithm, but the computations loose their stability. An iterative robust procedure that does not require regularization is proposed to improve the stability of the scheme.
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The Medium Directional Vision Time Section in a Seismic Survey by Works of Multifold Coverage
More LessThe new approach to creation the special seismic record by works of multifold coverage - the common deep area (CDA) gather is offered. The reflection time-distance equation of the CDA method is resulted. On the basis of numerical modeling is shown, that seismic records of multifold coverage allow confidently carrying out definition of spatial coordinates of reflecting boundary – dip azimuths and reflector dip. The new modified common-offset gather and new technology of time section formation (the medium directional vision time section) is offered.
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Statics Estimation and Raw Data Quality Control in CDP Data by Means of POLYCOR Method
Authors A.V. Kopchikov, A.A. Tabakov and V.N. FerentsiPOLYCOR is an alternative method of static shifts correction in CDP data processing based on multiple correlations. It is based on four-factor model of time shifts. This model includes kinematical shifts, dip shifts and shot point (SP)/ observation point (OP) statics. POLYCOR method features high noise immunity. Accuracy of SP and OP statics determination in practice does not depend on shift values (for wide range of shift values). When using this method it is not necessary to involve a priori estimation of velocity. Paper contains description and efficiency estimation of POLYCOR method. Efficiency estimation is based on the synthetic data experiment. Results of synthetic data experiment are described and illustrated. Synthetic data experiment results confirm that an accuracy of SP static determination does not depend on a priori defined SP static shifts. Presence of white noise signal in most case does not affect accuracy and reliability of algorithm.
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Current Demands to Accuracy of Near-Surface Studies for Performing CDP Reflection Surveys
Authors YU.N. Dolgikh, S.I. Shulik and I.N. BerdyuginSteady toughening of demands to accuracy of seismic exploration results against amplitude contraction and reduction of prospect-target areas being brought into operation is a present-day tendency seen in West Siberia. A complex but rather urgent practical task of CDP reflection surveying is to identify low-amplitude small-sized and shallow-buried (at level of S-G horizons) targets which presence in a wave field of time sections is hidden by near-surface velocity inhomogeneities, i.e. when a near-surface factor is dominant or comparable to a structure factor. It is necessary to provide a proper accuracy of near-surface inhomogeneities corrections in the conditions typical for northern areas of West Siberia. To perform accurate correction for near-surface structures, it is necessary to apply special near-surface targets’ observation systems, for example: multi-level seismic technologies that envisage use of several receiving systems different in their specification parameters. A report gives a brief overview of the existing approaches to near-surface correction, as applied, mainly, to weathering and permafrost zones; draws attention to distortion effects of these inhomogeneities; formulates methodic conditions at which a seismic exploration method provides the accuracy needed.
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Azimuthal Anisotropy in Marine Streamer Data
Authors G. Williams and R.J. WombellTowed-streamer acquisition samples a narrow range of azimuths. We discuss the resulting sensitivity of such data to azimuthal velocity anisotropy. Correction for such effects, using either a residual moveout correction before migration or incorporating the anisotropy within the migration step itself, can significantly improve the imaging of the data.
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Massive 3D VSP Data Migration with Energy Hashing Technique
Authors V.A. Mishin, S.I. Alexandrov and V.H. KivelidyNew migration technique of massive 3D VSP data is presented. The method is based on energy hashing algorithm. This technique is designed to enhance the quality of seismic images of complex geological structure under limited priory information. The method effectiveness is demonstrated on experimental data processing result.
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3D Acquisition Geometries as the Way to Overcome Drawbacks of Today's Seismic Exploration Technologies
By A.A. TabakovThe need for highly detailed investigation of complicated and small reservoirs as well as efficient extraction of residual resources from mature deposits has been constantly growing in recent years. This fact sets up new requirements to efficiency of implemented geophysical exploration methods and first of all seismic methods as the main tool for hydrocarbon reservoirs study. In this paper exploration abilities of modern land and borehole seismic are discussed. Their general features, resolution power and accuracy are mentioned and principal shortcomings are formulated. Integrated surface-downhole seismic acquisition geometries are proposed as the way to compensate specific drawbacks of land seismic and VSP. Case stories prove the efficiency of the new acquisition system.
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Post-Stack Velocity Analysis by Separation and Imaging of Seismic Diffractions
Authors S. Fomel, E. Landa and M.T. TanerSmall geological features manifest themselves in seismic data in form of diffracted waves, which are fundamentally different from seismic reflections. Using two field data examples, we demonstrate the possibility of separating seismic diffractions in the data and imaging them with optimally chosen migration velocities. Our criterion for separating reflection and diffraction events is the smoothness and continuity of local event slopes. Our criterion for optimal focusing is the local varimax measure. The objective is fast velocity analysis in the post-stack domain and high-resolution imaging of small-scale heterogeneities. Our examples demonstrate the effectiveness of the proposed method for high-resolution imaging of such geological features as faults and salt boundaries.
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Gas-Field Prediction in Transit Zone Based on Seismic Tomography Data
Authors Y.V. Roslov, N.T. Dergunov, N.N. Efimova and T.S. SakoulinaLong offset seismic data acquisition in shallow water allows the use of complex seismic tomography technology for gas-field prediction. The technology is based on the a complex processing of refracted and reflected waves. The effectiveness of the complex seismic data processing was evaluated on a test model and on seismic data acquired in a shallow-water zone of Ob Bay. Low velocity anomalies detected with seismic tomography correspond to anomalous dynamic parameters of seismic data and morphological evidences within this explored gas-field.
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Local Disturbances Cut off by Nonlinear Estimation of Trends
Authors A.V. Masjukov and V.I. ShlyonkinA new nonlinear method is proposed for attenuation of noise, which spatial width is a priory bounded above. The algorithm is based on successive rejections of digital signal points used for trend estimation.
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Geological Disintegration Zones and Their Representation in the Fields of Reflected and Scattered Waves
Authors S.I. Shlionkin, V.A. Ganiev and G.V. KashirinThe vertical geological structure disintegration, appearing as a result of depth tectonic processes, in most cases is a determing factor in generation of oil and gas accumulations. Locations of many hydrocarbon deposits are confined to tectonic active zones. Geological disintegration leads to formation of a deep-seated structure of gas-liquid migration channels. It has also an influence on filtration-accumulation properties of already formed epigenesis sediments. We suppose that the channels of vertical disintegration may be considered as self-dependent geological objects to which hydrocarbon traps are confined. The paper is devoted to the problem of investigation, detection and exploration of such objects by new seismic technologies.
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A Simple Seismic Data Discovery Portal for Scientific Collaborative Research
More LessAn Open Source web based Discovery portal is presented, that aims to support scientific collaborative work in the field of Seismic Data analysis. Based on the Simple Object Access Protocol (SOAP) it allows setting up a layer of networked archives where data and metadata can be easily found and shared. Data structure and methods are kept as simple as possible, to avoid, on one side, the need of human interaction (a cost that small institutions cannot afford), and on the other side to obtain a lightweight and flexible tool that could easily be used in a non prescriptive environment as Scientific Research.
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Review of Missions, Strategies and Solutions for Effective IT in E&P
By K.N. TimakovReview of modern IT technologies, their strategies, major problems and solutions for E&P and knowledge management.Complex analysis of IT applied in E&P, based on open sources publications for last 5 years.
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A New Approach to Interpreting and Holding Geologic-Geophysical Data on the Basis of Geoinformation Technologies and Principles of Fractal Analysis
Authors A.A. Simanov and A.V. PuginAt present the complex analysis of the whole available information about the subjects of inquiry occupy an important place in interpretation process. In this paper we propose a new approach to interpreting and holding of geologic-geophysical data based on joint use of geoinformation technologies, fractal analysis and approximation by equivalent sources.
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The Geoinformation Analysis - Debatable Questions
More LessDebatable questions of ideology and methods of the geoinformation analysis are considered within the framework of geodata classification over levels of generalization of the information. 3 levels of generalization are suggested: initial data; fields of geological and geophysical characteristics; geological objects formally described as cartographic elements. The thesis according to which fields should be used for detection not deposits, and rather homogeneous geological objects, such as intrusions, structures, tectonic unconformities, zones of better collector proprieties, etc. is proved. At the third level of generalization of information these objects are used for the forecast of complex geosystems, including various deposits. In consideration of the problems solved at the second level of information generalization, debatable questions of interpolation, division of fields and estimations of geological objects parameters from the geophysical data are discussed. In particular unacceptibility for geology of the so called metrological approximation of fields is proved. Arguments in favour of the statistical theory of interpretation are given: geological interpretation of the geophysical data always consists in transition from priori evaluations of objects’ parameters to posteriori evaluations.
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Mathematical Modeling in Impulsive Induction Surveying during Prospecting of Kimberlite Bodies of Yakutian Diamondiferou
Authors V.M. Zhandalinov and V.V. StognyTransient electromagnetic method in modification of soundings is one of the basic methods of kimberlite pipes exploration in Yakutian diamondiferous province. Particular features of mathematical modeling at different stages from planning and acquisition by TEM sounding to construction of effective models and issuance of recommendations on performed investigations are discussed.
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Resource Optimization and Subsurface Mapping - Making the Most of Oil Fields, Aquifers and Geothermal Reservoirs
By P. RollinsThis paper will introduce a new subsurface mapping technique, analyzing its potential to improve upon the speed and accuracy of traditional imaging technologies while detailing its applications in oil recovery, ground water utilization and geothermal exploration.
The procedure entails the strategic placement of electrodes within the designated reservoir. The electrodes charge the extant water with a low voltage, low amperage, audio-frequency current. (In the case of oil recovery, the charged substance is the water flood or steam injection frequently used in residual oil extraction). The current running through the charged water creates a distinctive magnetic field that represents the location and character of the flow occurring between the electrodes and thereby reveals the essential features of the reservoir. This unique field is identified from the surface using a highly sensitive receiver. The data thus received is used to create either aerial maps or serial profiles of the reservoir in question.
This paper will examine the science behind the procedure, discuss its relevance for exploration geophysics, and analyze the lessons learned from recent case-study deployments of the technology.
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Geoelectric Investigations Results along Basic Geophysical Profiles in Eastern Siberia
Authors A.V. Pospeev, Y.A. Agafonov, V.V. Gomulskiy, V.A. Kondratiev, E.A. Olkhovik and A.M. PashevinThe geoelectric structure of a sedimentary cover of the south of the Siberian platform is characterized as rather favorable for studying by methods of inductive electroinvestigation. High electric resistance of surrounding rocks of a sedimentary cover considerably differs from resistance of horizons - reservoirs. Saturation of reservoirs by mineralized fluids causes precise correlation of electric properties of horizons and their collecting properties, and also allows to estimate fluid type.
Example of the decision of new geoecological problems are monitoring studying of a sedimentary cover in area of large industrial plants. TEM parameters maps and geoelectric sections allow to study evolution of underground geological structure, changing of horizons saturation.
During deep-well drilling there are frequent serious problems connected with zones of abnormal high strata pressure and also zones of drilling fluid absorption. Prediction of deep-well drilling conditions - both at a design stage, and during drilling became possible with introduction of new electromagnetic sounding technology. Specificity of this problem is complicated by presence of a powerful source of 50-Hz noise - electrogenerators and other power-plants used during drilling. Results of works with TEM get possibilities to allocate depth intervals with reservoir-horizons, estimate their saturation and predict possible complications.
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The New Opinion about Geoelectrical Model of Hydrocarbon Deposit
Authors K.V. Tertyshnikov, E.S. Kiselev, A.S. Gorunov and E.I. LarionovA new geoelectrical model is described, based on oil and its analogs properties in electromagnetic field and description of oilas disperse-colloidal system. In this model oil deposit is defined as anomalous active electrical object. Advantages of this model are shown in using electrical methods for localization deposits. Successful examples of electrical survey for exploration and reservoir delineation are described
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The Newest Geophysical Exploration Results of Mutnovskoe Hydrothermal Deposit on Kamchatka Peninsula
Authors A.G. Nurmukhamedov, I.I. Chernev, A.G. Yakovlev, O.V. Pankratov, R.G. Batyrshin and D.A. AlexeevConsidered some recent results of electroprospecting survey, carried out in 2004-2005 in Mutnovskoe hydrothermal deposit region using newest technologies. The goal of the survey was supplementary exploration of deposit to provide heat-carrier for Mutnovskaya hydrothermal power station. AMT-MT (in 0.01-1000 sec periods interval) and frequency soundings were carried out. As a result of interpretation of acquired data some geoelectrical cross-sections and resistivity maps were obtained. Finally, an anomalous conductive region was detected, with most of productive boreholes located inside.
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Fast Processes of Induced Polarization - Nature, Properties, Geological Information
Authors E.YU. Yuditskikh, A.P. Karasyov and V.V. Olentchenkotheoretical and experimental data about rocks and ores inducted polarization fast processes (FIP) are considered. The most important FIP properties and their connection with electrochemical parameters and natural electronic conductors material constituents are supplied. The possibility of the method application is shown in the search for ores and in investigation of frozen ground zones. FIP measurement technique in a current feeding line with the linear grounding is explained which lines in the basis of ground shooting in movement and in continuous well logging
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Experimental Geoelectric Investigation within the Gold Field in Ukraine
Authors M. Yakymchuk, I. Korchagin, S. Levashov, Y. Pyschaniy and A. KovalThe results of experimental geoelectric investigation within the gold field in Ukraine are given. The obtained data show that developed express-technology of geoelectric research can be used for ore (and gold) fields prospecting.
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Some Features of Geological and Geophysical Model of Kimberlite Pipe for Archangelskaya Diamondiferous Province
Authors V.Y. Abramov, Y.K. Golubev, P.O. Barsukov and A.G. YakovlevNew geological and geophysical model of kimberlite pipe for Archangelskaya diamondiferous province
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Nonlinear Effects in Liquid and in Fluid Saturated Friable Media under DC Field
Authors M. Podberezhnyy, Y. Nefedkin and A. LamukhinThe series of experiments on research of nonlinear properties amplification in liquid and fluid saturated rock under an electric field action have been carried out in the laboratory physical models. As a physical models there were used the one-dimensional liqiud and sand model saturated with water. Acoustic source of biharmonic signal was used. The parameters of diferental frequensy wave in acoustical frequency range of 250Hz-5kHz have been studied under influence of external direct electric current. The significant changes of diferental friquency wave's amplitudes were observed depending on DC action. At the same time there were no considerable changes of seismic parameters in the case of rock saturated with non-conductance liquid or in dry medium. A possible mechanism of these effects is discussed.
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Effect of Dolomitization on Physical Properties of Palaeozoic Carbonate Rocks - Case Study from South Estonia
Authors A. Shogenova, A. Kleesment, A. Teedumäe, K. Shogenov and A. JõelehtInfluence of dolomitization on Ordovician, Silurian and Devonian carbonate rocks was studied on 555 rock samples from 9 boreholes located at the south of Estonia. Density porosity and magnetic susceptibility of rock samples were analysed together with bulk chemical composition. Dolomitized rocks (dolostones and dolomitic marlstones) were compared to primary rocks (limestones and calcitic marlstones). Devonian rocks overlay either Silurian or Upper Ordovician rocks. Devonian fully dolomitized rocks could be compared only with Ordovician and Silurian primary rocks. Devonian rocks were also compared with Ordovician and Silurian dolomitized rocks in order to reveal influence of Devonian dolomitization on them. Porosity of Devonian and Silurian rocks was the highest and had secondary genesis. Many of the studied Palaeozoic dolomitized rocks have increased magnetic susceptibility and iron content. Early diagenetic dolomitized rocks from the lowermost part of the Ordovician and late diagenetic rocks from middle-upper Ordovician have the most significant increase (2-3 times) in magnetic susceptibility and total iron content. Close values of magnetic susceptibility of Devonian, Upper Ordovician early diagenetic and Ordovician late diagenetic dolomitized rocks permits to support idea about influence of Devonian dolomitization on Ordovician rocks and Devonian time of late diagenetic dolomitization in Ordovician succession.
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Probing of Discontinuity of a Core by a Profilograph for Boosting Reliability a Hybrid Module
Authors V.V. Semenov, E.V. Moreva and I.B. RatnikovThe particular difficulties are called by a quantitative assessment of thickness finely - and microlayers by methods a hybrid module, which one do not participate in development, though they contain all tags of saturation by naphtha. The reliable methods permitting uniquely to select thin interlayers, miss. In this connection, the special urgency is gained by development of methods of a quantitative assessment of effective thicknesses of a nonuniform header representing an interbedding of different lithological types of rocks by thickness from 0,4 meters and up to units of a millimeter.
In the given job the procedure of separation by saturated naphtha of microlayers - reservoir in a layer is considered, which one is diagnosticated till a hybrid module as clay.
The actual lithological types and their thicknesses on a core are determined with application of a profilograph. On value of extremums on a profile record the lithological type of a rock, and also border of junction of one type of a rock to other is determined. The data of contouring of a core, and also value of porosity and permeability are put on the diagram GR, that allows in detail to differentiate a drilling log in lithological and petrophysics aspect.
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Magnetic Properties of PT-Bearing Dunite of the Konder Massif (Russian Far East)
Authors P.S. Martyshko, V.A. Pyankov and A.A. EfimovThe observed gravitational field of the Konder pipe-like dunite-pyroxenite body coincides well with model field designed for a vertical cylinder with radius 2.7 km and density 3.3 g/cm3. It forced its way through crystalline basement and sedimentary cover of the Aldan Shield. Such process is a combination of rolling and hydroextrusion. Magnetic properties of dunite depend on distance from the pyroxenite rim and have a multiextreme character. The distance between extremes is 150-200 m. Magnetic susceptibility χ decreases from value ~ 0,01 unit SI. Variations of residual magnetization Іn are in an antiphase with spatial χ changes. Thermodemagnetization extremes at 310°C are characteristic of maghemite and localize in minimum zones of χ curves. Values, which are characteristic of magnetite are observed in maximum zones. Thus, various redox conditions are characteristic of maximum and minimum zones. Magnetic data explain some features of geochemical structure of the massif generated during emplacement because of localization of shift deformation in accommodation bands.
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3D Modelling of the Low-Density Zones in a Dam Site through Micro-Gravity Data
More LessA micro-gravity survey was conducted for detecting the low-density anomalies in a site
considered for construction of a dam close to Shiraz, Iran.
Residual anomalies are determined through Bouguer gravity anomalies.
The 3-D gravity inversion prescribed by Camacho et al. (2002) is applied to model the
anomalies.
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Gaz Deposits Phenomenon at Ob-Taz Shallow Water in the Anomalies of Potential Fields
Authors A.A. Chernov, A.N. Zaitsev, V.A. Kholodilov, V.V. Kolesov and M.B. LurieОписаны закономерности распределения гравимагнитных полей и соотношения их аномалий со структурно-тектоническими элементами и нефтегазоносностью Западно-Сибирской плиты. Дан анализ взаиморасположения экстремумов геопотенциальных полей и продуктивных антиклинальных структур в районе Обь-Тазовского мелководья. Наиболее интересной особенностью аномальных магнитного и гравитационного полей в рассматриваемой области является устойчивая локализация подавляющего большинства открых здесь месторождений УВ близ локальных минимумов того и другого поля, т.е., непосредственная связь залежей УВ с аномалиями полей. Анализируются различные эффекты, приводящие к возникновению этого явления. На модели крупного месторождения произведена оценка вклада в формирование гравитационной аномалии непосредственного эффекта залежи, обусловленного воздействием минерализации на контакте нефти с вмещающими породами, миграцией флюидов по разрезу и другими эффектами. На основании изложенного делается вывод о целесообразности использования данных грави- и магниторазведки в комплексе нефтегазопоисковых работ в данном районе.
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Gravity Prospecting in Petroleum Geology
By Z.M. SlepakThe paper reviews the results of the rock density studies based on laboratory, logging and gravimetry data. It has been shown that major anomalous changes in the gravity field are due to lateral density variations adequately reflected in the block structure of the consolidated crust and in local structures of the sedimentary cover. The paper describes the gravity modelling technique that uses the density variations detected in the Earth's crust and permits the density modelling of geological environments and structures by Bouguer anomalies. It gives examples of successful gravity inversion solutions for the central portions of the Russian Plate and other regions of significant importance in oil and gas exploration. The paper also shows the high geological efficiency of gravity modelling used for studying the block structure of the consolidated crust and for exploring the local structures containing oil and gas fields.
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Evolution of the Ideas of Berezkin V.M. in Russian and International Geophysical Science
Authors A.A. Chernov, V.A. Boldyreva and P. PashtekaОсвещена научная и практическая деятельность В.М.Березкина на ниве применения гравиметрических данных в геологических изысканиях. Изложено содержание основных разработок В.М.Березкина во всех областях данной отрасли знаний. Особое внимание уделено разработке и применению функции полного нормированного градиента силы тяжести (ПНГ) – любимому детищу Валентина Макаровича, которое нашло широчайшее применение в геофизических исследованиях, как в России, так и за границей. Использование функции ПНГ породило множество модификаций и методик, различающихся как вычислительным аппаратом, так и геологической направленностью.
Наиболее известными и оригинальными являются, развиваемые в течение ряда лет, основанные на использовании функции ПНГ, методика КВОТ и метод ГРАДДИС, в которых совершенно различным образом, но весьма успешно решена проблема выбора оптимальной гармоники разложения в ряд Фурье – наиболее сложной при реализации метода Березкина.
Описаны основные положения и результаты практического использования метода ГРАДДИС – наиболее результативного при интерпретации данных грави- и магниторазведки при поисках и разведке месторождений ископаемых УВ.
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Using of Wavelet Analysis on Sourcewise Approximation of Geopotential Fields
By A.S. DolgalWe offer a new high-tech algorithm of approximation of gravity and magnetic fields by equivalent sources disposed at different depths. Spatial distribution of sources is determined by means of fast wavelet transform
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On Linear Inverse Gravimetric Problem Solution for Layered Media
Authors P.S. Martyshko and D.E. KoksharovTechnology has been developed for constructing density distributions in curve-edged layers using gravity data. It is based on fundamental results in field theory and theory of ill-posed inverse problems. This method involves algorithm of gravity field sources separation. We tested this approach for model samples and used it for building density sections using practical data.
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Basement Characterisation by Regional Isostatic Methods in the Barents Sea
Authors J. Ebbing, C. Braitenberg, H.M. Bjørnseth, C. Fichler and J.R. SkilbreiWe study the tectonic setting of the greater Barents Sea region by investigating the isostatic state and the gravity field. Forward gravity modelling utilizing available information from seismics and boreholes show an apparent shift between the level of observed and modelled gravity anomalies. The difference cannot be solely explained by crustal densities and is changing between the Western and Eastern Barents and the Kara Seas. Local isostatic calculations show that the present crustal thickness in the Eastern Barents Sea is larger than expected. Despite the large sedimentary basins in the Eastern Barents Sea of up to 20 km thickness, the average Moho depth is >35 km. To compensate the thick crust, high-density material in the lithospheric mantle is needed in agreement with the gravity modelling. Taking into account the isostatic compensated mantle densities, the gravity field of the Eastern Barents Sea Region can be modelled generally well with local changes in crustal densities. The results indicate that the basins of the Western Barents Sea are mainly affected by rifting, while the Eastern Barents Sea basins seem to be intracratonic basins, and the Zemlya basins are flexural basins related to the mountain chain of Novaya Zemlya.
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