One of the possible mechanisms causing significant emissions of methane into the atmosphere within the Arctic shelf may be the decomposition of gas hydrates. Their accumulations within the Arctic shelf formed almost simultaneously with the formation of permafrost, which contributed to the emergence of a zone of stable existence of gas hydrates. The subsequent flooding of the Arctic shelf led to the degradation of the permafrost and the violation of the conditions for the existence of hydrates. To assess the state of the stability zone, methods of mathematical numerical modeling are used. Standard seismic methods are widely used to localize gas hydrates, but monitoring their physical state requires the development of fundamentally new approaches based on solving multiparameter inverse seismic problems. In particular, the degree of attenuation of seismic energy is one of the objective parameters for assessing the consolidation of gas hydrates: the closer they are to the beginning of decomposition, the higher the attenuation, and hence the lower the quality factor. Thus, the methods of seismic monitoring of the state of gas hydrates in order to predict the possibility of developing dangerous scenarios should be based on solving a multi-parameter inverse seismic problem. This publication is devoted to the presentation of this approach.

An approach to reconstructing a velocity depth model of the near surface using full wave inversion is proposed, implemented, and tested. We have shown previously that, although the involvement of multiples formed on the free surface increases the method stability, it decreases its resolving capacity. Therefore, at the first stage we engaged the entire wave field in processing, but afterwards we suppressed the free-surface related multiples. The results obtained demonstrate the potential of using this method to reconstruct quite complex near-surface structures, even if they have trap intrusions.

—The efficiency of the development of an oil and gas field is largely determined by the knowledge of its geologic structure. In the recent decade, complex fractured carbonate reservoirs have attracted more and more attention. This paper is concerned with a new technology for constructing 3D images of complex reservoirs, based on Gaussian beam processing of scattered seismic waves. This technology was developed at OOO RN-KrasnoyarskNIPIneft’ in cooperation with the Trofimuk Institute of Petroleum Geology and Geophysics. To test it, a special synthetic model was constructed, which is analogous to one of the licensed objects of PAO NK Rosneft’. For this purpose, a full-scale 3D seismic was performed, which provided us with synthetic wave fields and made it possible to carry out well-controlled numerical experiments for reconstructing the geologic structure of the object of study. One of the distinctive features of the constructed digital model (digital twin) is the presentation of faults not as some ideal slip surfaces but as 3D geologic bodies filled with tectonic breccias. A series of numerical experiments was performed to simulate such breccias, the geometry of these bodies, and the geomechanical processes of fault formation. To select the parameters of the used method of discrete elements, we used the information obtained by geophysical studies in horizontal wells crossing the fault within the geologic prototype of the constructed digital model.

The procedure of 3D seismic diffraction imaging for the depth structure followed by calculation of the diffraction attributes is considered. The algorithm is based on asymmetric summation of seismic data and makes it possible to identify three characteristics of the medium: the structural diffraction attribute, the point diffraction attribute, and the structural diffraction azimuth. These attributes allow one to distinguish between the fracture and cavernous zones and to determine the orientation of fractures. The practical evaluation of the approach is presented on real seismic data.

Представлен алгоритм расчета потенциального электрического поля в образцах горных пород и предложены оценки их удельного электрического сопротивления (проводимости). Алгоритм ориентирован на расчет поля в существенно неоднородных моделях среды с частично насыщенными и полиминеральными образцами горных пород. В основе алгоритма – итерационные методы крыловского типа, в качестве предобусловливателя используется оператор, обратный к оператору Лапласа для однородной среды. Для вычисления предобусловливателя используется спектральный метод в направлениях, нормальных к основному направлению электрического тока, а серия одномерных задач решается методом прогонки. Решатель реализован с использованием графических процессоров (GPU) и позволяет обрабатывать образцы размером до 4003 вокселей на одном GPU. We present a numerical algorithm for computing the electric field in digital rock samples and estimating their electrical resistivity (conductivity). The main peculiarity of the algorithm is its applicability tostrongly heterogeneous models including partially saturated and multi-mineral rock samples. The algorithm is based on the iterative Krylov-type solver preconditioned by the inverse Laplace operator for homogeneous media. The preconditioner is computed using the spectral method in directions orthogonal to the direction of the main electric current, whereas the series of 1D problems are solved by the Thomas algorithm. We implement the algorithm using GPUs, which allows us to use a single GPU to solve the problems for samples whose size is up to 4003 voxels.

PreviousNext No AccessSEG 2018 Workshop: SEG Seismic Imaging Workshop, Beijing, China, 12–14 November 2018Application of asymmetric summation of seismic data for fault and fracture imagingAuthors: V.A. CheverdaM.I. ProtasovG.V. ReshetovaA.I. LedyaevD.A. PetrovV.V. ShilikovA.S. MerzlikinaV.V VolyanskayaV.A. CheverdaIPGG SB RASSearch for more papers by this author, M.I. ProtasovIPGG SB RASSearch for more papers by this author, G.V. ReshetovaIPGG SB RASSearch for more papers by this author, A.I. LedyaevRosneftSearch for more papers by this author, D.A. PetrovRosneftSearch for more papers by this author, V.V. ShilikovRosneftSearch for more papers by this author, A.S. MerzlikinaRosneftSearch for more papers by this author, and V.V VolyanskayaRosneftSearch for more papers by this authorhttps://doi.org/10.1190/SEIM2018-20.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract An approach to diffraction imaging of fractures and faults by multicomponent surface data is presented and discussed. It is based on a specific imaging procedure, which consists of the weighted summation of multicomponent data. These weights are computed by tracing a specially chosen Gaussian beams. In order to get an image of fault and fractures, these beams are taken in a way forming so-called selective images (Pozdnyakov and Tcheverda, 2006; Protasov and Tcheverda, 2011). Their geometry provides suppression of regularly reflected waves and, thus, emphasizes the presence of small-scale heterogeneities that give rise to diffracted/scattered waves. Numerical experiments with synthetic and real data from Eastern Siberia are presented and discussed. Keywords: fractures, fault, imagingPermalink: https://doi.org/10.1190/SEIM2018-20.1FiguresReferencesRelatedDetails SEG 2018 Workshop: SEG Seismic Imaging Workshop, Beijing, China, 12–14 November 2018ISSN (online):2159-6832Copyright: 2019 Pages: 115 publication data© 2018 Published in electronic format with permission by the Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 05 Jun 2019 CITATION INFORMATION V.A. Cheverda, M.I. Protasov, G.V. Reshetova, A.I. Ledyaev, D.A. Petrov, V.V. Shilikov, A.S. Merzlikina, and V.V Volyanskaya, (2019), "Application of asymmetric summation of seismic data for fault and fracture imaging," SEG Global Meeting Abstracts : 78-81. https://doi.org/10.1190/SEIM2018-20.1 Plain-Language Summary KeywordsfracturesfaultimagingPDF DownloadLoading ...

Summary One of the main ways to identify possible risks when conducting field seismic observations is the method of direct modeling based on real geological models that describe the structure of the geological section in the most detailed way over the entire depth interval. The object of study in the innovation project, which includes the modeling and processing of 3D seismic data, is the pre-Jurassic complex of the Tomsk region. The task of 3D modeling is the preparation of synthetic seismograms, which are further subject to analysis, processing and migration. The first difficult problem is the construction of the geological model itself. The initial three-dimensional geological model included various structural elements that may be potential objects for oil deposits in the pre-Jurassic complex. The velocity model were determined according to information from wells that uncovered Paleozoic sediments. In this paper, the main stages of the 3D modeling project implementation from building a model to obtaining synthetic seismograms are considered.

Summary An approach to innovative method for the extraction of scattered waves, developed by OOO RN-KrasnoyarskNIPIneft, using the method of Gaussian beams to detect fractured-cavernous reservoirs and faults. Gaussian beams are a new round in the development of techniques using scattered waves. The new technology has a high and uniform resolving power, which will allow obtaining accurate diffraction images of the fine structure of fractured-cavernous reservoirs.

Summary In the recent study of the Yurubcheno - Tokhomskoye oil field more and more attention is paid to the Riphean intervals with high cavitary. Current estimates of specialists working in this area forecast about 30% of geological reserves of hydrocarbons within these intervals. At the moment nor the origin or dissemination of these intervals are not clear. There is some general geological knowledge about these layers. In particular, it is worth mentioning that their average width is 0.5 m – 1 m, the average voidage is about 10% and they are located just below the Riphean interface at a depth around 2000 m. To assess the possibility of seismic techniques for imaging these objects we perform full scale numerical simulation of seismic waves’ propagation and generate synthetic multishot - multioffset data. The simulation was done by parallel software on the base of finite-difference technique with local grid refinement in time and space. Next, we use multicomponent Gaussian beams to construct scattered waves’ images of thin cavernous layers.

The constitutive equations of motion of an elastic medium with given initial stresses are formulated in the form of a hyperbolic system of first order differential equations. Equations describing the propagation of small perturbations in a prestressed isotropic medium with an arbitrary dependence of the elastic strain energy on the strain tensor are derived, and equations for the quadratic dependence of elastic strain energy on the strain tensor are given.

Рассматривается реализация последовательно численного метода построения глубинной скоростной модели на основе метода обращения полного волнового поля. При этом обратная динамическая задача сейсмики сводится к отысканию точки минимума целевого функционала, характеризующего среднеквадратичное уклонение зарегистрированных данных от рассчитанных для текущей модели среды. Отличительной чертой предлагаемого подхода является декомпозиция пространства моделей на две составляющие: плавно меняющийся пропагатор (макроскоростная модель) и резко изменчивая по пространству компонента, называемая рефлектором. Отыскание точки минимума производится поочерёдно в этих двух подпространствах. Приведены результаты численных экспериментов по реконструкции скоростной модели Marmoussi2 с использованием реального диапазона частот и выносов источник-приёмник.

The consecutive numerical method is implemented for construction of a depth velocity model by full waveform inversion. The inverse dynamic seismic problem is reduced to finding the minimum point of the objective functional characterizing the mean square deviation of the recorded data from those calculated for the current model of the medium. A distinctive feature of the proposed approach is decomposition of the model space into two components: a smoothly varying propagator (macrovelocity model) and a rapidly spatially varying component called a reflector. The minimum point is calculated in sequence in these two subspaces. This paper reports the obtained data on numerical experiments related to reconstruction of the Marmoussi2 velocity model using a real frequency range and a source–receiver offset.

In article methodical aspects of training for the inverse problems for differential equations of students of higher education institutions of the physical and mathematical and natural-science directions of preparation are stated. The attention to expediency of development in students of scientific outlook allowing to acquire fundamental knowledge of methods and methodology of research of mathematical models of the inverse problems, to master the principles of the organization of theoretical and practical researches of the inverse problem, to create ideas of the inverse problems as universal tools of knowledge of world around is paid. In article attention that development of scientific outlook in training activity to the inverse problems for differential equations allows students to deep understanding of idea of integrity of the world, assimilation of disciplines of applied mathematics, disciplines from other data domains is paid. It is marked that in the course of such training in students lines of humanitarization take root. Students acquire skills to analyze the received solutions of the inverse problems for differential equations, to formulate logical outputs about an ecological status of air space, earth’s environment or the water environment, to apply results of solutions of the inverse problems for differential equations in the humanitarian analysis of applied researches.

Предложен алгоритм решения систем линейных алгебраических уравнений (СЛАУ), основанный на методе исключении Гаусса и предназначенный для решения уравнения Гельмгольца в трехмерных неоднородных средах. Для решения СЛАУ, возникающих в геофизических приложениях, разработана параллельная версия алгоритма, направленная на использование гетерогенных высокопроизводительных вычислительных систем, содержащих узлы с MPP- и SMP-архитектурой. Малоранговая аппроксимация, HSS-формат и динамическое распределение промежуточных результатов среди кластерных узлов позволяют решать задачи в разы большие, чем при использовании традиционных прямых методов, сохраняющих блоки $L$-фактора в полном ранге (Full-Rank, FR). Использование предложенного алгоритма позволяет сократить время расчетов, что актуально для решения трехмерных задач геофизики. Численные эксперименты подтверждают упомянутые преимущества предложенного малорангового прямого метода (Low-Rank, LR) по сравнению с прямыми FR-методами. На модельных геофизических задачах показана жизнеспособность реализованного алгоритма. An algorithm for solving systems of linear algebraic equations based on the Gaussian elimination method is proposed. The algorithm is aimed to solve boundary value problems for the Helmholtz equation in 3D heterogeneous media. In order to solve linear systems raised from geophysical applications, we developed a parallel version targeted on heterogeneous high-performance computing clusters (MPP and SMP architecture). Using the low-rank approximation technique and the HSS format allows us to solve problems larger than by the use of traditional direct solvers with saving the L-factor in full rank (FR). Using the proposed approach reduces computation time; it is the key-point of 3D geophysical problems. Numerical experiments demonstrate a number of advantages of the proposed low-rank approach in comparison with direct solvers (FR-approaches).