—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.

––Acoustic-emission events in core samples are detected from total wave energy by time reversal mirror (TRM) inversion using equations of the elastodynamic theory in polar coordinates. The acoustic emission parameters used in the modeling correspond to laboratory testing data on core samples. The simulation results for digital core have implications for the configuration of multichannel data acquisition, including the optimal number of receivers or channels and the placement of sensors. Testing with different numbers of receivers/channels and at different frequencies shows that the method can provide satisfactory resolution even at a relatively low frequency.

Summary We present 3D scattering waves imaging procedure based on the use of velocity model in time domain. This procedure gives the possibility to construct selective images corresponding to different directions of incident and scattering energy propagation. We tested the approach on realistic synthetic data greeted for 3D geological model, containing typical diffraction objects: faults, caves and fracture corridors. Approbation of the developed approach was provided on several real data from Eastern Siberia.

Summary The object of the research is a three-dimensional digital seismic-geological model of a real geological object and the corresponding field observations, both by the method of vertical seismic profiling and surface acquisition. The purpose of the work is as follows: 1. Construction of a digital structural model and its verification by comparing field observations and individual synthetic data sets; 2. Constructing a synthetic data set for a structural model for an areal excitation and registration system with a given overlap; 3. Construction of a model of a fractured medium based on the use of DFN and application of the concept of ideal seismic images. 4. Calculation of total wave fields for a fractured medium and analysis of the contribution made by the presence of fracturing.

Summary The paper presents the results of laboratory experiments and numerical modeling for solving the problem of acoustic emission event recovery. The equations of the dynamic theory of elasticity in the polar coordinate system were used as a mathematical model. For reconstructing acoustic emission events Time Reverse Mirror approach with total energy imaging was used. The simulation results made it possible to evaluate a number of basic characteristics for the configuration of a multichannel data acquisition system, the frequency of the acoustic emission signals, to determine the required number of recording channels and the position of the sensors in the core.

Summary We present 3D scattering waves imaging procedure based on the use of the velocity model in the time domain. The imaging is done by special summation of multicomponent multi shot – multi offset seismic data with special weights. The weights of this kind of summation we compute by tracing Gaussian beams from the imaging point towards the acquisition. This procedure gives the possibility to construct selective images corresponding to different directions of incident and scattering energy propagation that allows reconstruction of scattering indicatrices. To test this approach, we developed a realistic 3D geological model, containing typical diffraction objects, like faults, caves and fracture corridors. Synthetic seismic data for this model have been used as input data to verify the resolution and information content of the imaging procedure.

Summary We propose the new numerical algorithm for evaluating elastic properties of the rock core samples by 3D CT digital images. This approach is based on the numerical simulation of a series of physical experiments by combination of the energy equivalence principle and the new iterative relaxation method. On this base, the effective compliance and stiffness tensors of a representative volume of a core sample is computed. The proposed method is verified using synthetic samples with specified properties.

Summary A parallel algorithm for evaluating the elastic properties of rock samples from 2D and 3D images of computed tomography is presented. The method is based on the principle of the equivalence of the strain energy, in which the static boundary conditions simulating a physical experiment are chosen as homogeneous ones and the components of the compliance tensor are determined. A special feature of the algorithm is a new scheme for solving problems of static loading of a sample by establishing the problem of dynamic elasticity theory and a parallel implementation scheme based on MPI + OpenMP. The results of numerical calculations are presented. The accuracy of determining the effective parameters was verified on homogeneous samples with known properties, and layered ones, for which the effective parameters were calculated using the Schoenberg method.

Summary Estimations of the elastic properties of a core sample are extremely sensitive to the quality of the CT-scan image. A coarse image resolution does not allow separating the grains and estimating their roughness. The size of images with fine resolution is either below representative volume or so representatively large that require huge computational resources for the numerical simulation of static loading tests. We present a new multi-scale numerical methodology that combines the geostatistics, computational topology and numerical upscaling. The essence of the approach is to estimate the distribution of the grain surface roughness, the distance between them and cement material by microscopic images (SEM), then to calculate the effective parameters of cement distribution for an equivalent model with flat contacts between grains. Finally, to use this effective cement to fill the interfaces between grains in a digital model built on CT images of medium resolution by computational topology.

In the recent study of the Yurubcheno - Tokhomskoye field more and more attention is paid to the intervals with high cavernosity. Current estimates of specialists working in this area forecast within these intervals about 30% of geological reserves of hydrocarbons. At the moment the origin of these intervals and their areal distribution are unclear. To assess the possibility of seismic techniques, primarily, the method of the scattered waves, we perform full scale mathematical modeling. The choice of scattered waves is done because there is almost no hope to reveal these intervals in the reflected waves. In contrast, the high concentration of subseismic cavities produce intensive scattering which can be used to image these cavernous areas. To increase the resolution of images in scattered waves we use multicomponent Gaussian beams. In contrast to the plane waves used in conventional focusing transformations, Gaussian beams are much localized in the space, namely, they are concentrated within the exponentially narrow vicinity of some predetermined ray. Thereby, it becomes possible to study the local scattering in the spatial domain. The realistic model of the void space used to construct two scale elastic models for numerical experiments is obtained from 3D computer tomography of D = 100 mm core samples from the layers of intense caving. Presentation Date: Wednesday, September 27, 2017 Start Time: 11:00 AM Location: 381A Presentation Type: ORAL

In order to study the effect of the micro-CT scan resolution and size on the accuracy of upscaled digital rock property estimation of core samples Bentheimer sandstone images with the resolution varying from 0.9m to 24m are used. We statistically show that the correlation length of the pore-to-matrix distribution can be reliably determined for the images with the resolution finer than 9 voxels per correlation length and the representative volume for this property is about 15(3) correlation length. Similar resolution values for the statistically representative volume are also valid for the estimation of the total porosity, specific surface area, mean curvature, and topology of the pore space. Only the total porosity and the number of isolated pores are stably recovered, whereas geometry and the topological measures of the pore space are strongly affected by the resolution change. We also simulate fluid flow in the pore space and estimate permeability and tortuosity of the sample. The results demonstrate that the representative volume for the transport property calculation should be greater than 50 correlation lengths of pore-to-matrix distribution. On the other hand, permeability estimation based on the statistical analysis of equivalent realizations shows some weak influence of the resolution on the transport properties. The reason for this might be that the characteristic scale of the particular physical processes may affect the result stronger than the model (image) scale.

In this paper we present an efficient and accurate numerical algorithm for simulation of sonic logging experiments. The basis of the approach is a heterogeneous finite difference method applied to acoustic-elastic wave equation written in velocity-stress formulation. The approach was designed to simulate wave propagation in 3D arbitrary anisotropic elastic media with attenuation. Moreover due to universality of heterogeneous finite-differences the algorithm allows to handle with surrounding models of extreme complexity. We also present and discuss results of simulation for arbitrary anisotropic inhomogeneous models.

In this paper we present an efficient and accurate numerical algorithm for simulation of sonic logging experiments. The basis of the approach is a heterogeneous finite difference method applied to acoustic-elastic wave equation written in velocity-stress formulation. The approach was designed to simulate wave propagation in 3D arbitrary anisotropic elastic media with attenuation. Moreover due to universality of heterogeneous finite-differences the algorithm allows to handle with surrounding models of extreme complexity. We also present and discuss results of simulation for arbitrary anisotropic inhomogeneous models.

This paper presents a problem-oriented approach, designed for numerical simulation of seismic wave propagation in models containing geological formations with complex properties such as anisotropy, attenuation, and small-scale heterogeneities. Each of the named property requires special treatment which increases computational complexity of the algorithm in comparison with ideally elastic isotropic media. At the same time these formations are typically relatively small taking up to 25% of the model, thus the computationally expensive approaches can be used only locally to speed-up the simulations. In this paper we discuss both mathematical and numerical aspects of hybrid algorithm paying the main attention to its parallel implementation.

Summary Common Middle Point seismic sections and their successive time migration provide extremely important knowledge about the internal structure of the 3D heterogeneous geological media and are key elements for successive geological interpretation. Full scale numerical simulation, that is one which starts with single shot seismograms, provides a deep understanding how the features of the image are linked with its subsurface prototype. Unfortunately, this kind of simulations for realistic geological media and 3D seismic surveys needs huge computer resources, especially for simulation of seismic waves’ propagation through multiscale media like cavernous fractured reservoirs. In order to significantly reduce the query of computer resources we propose to model these 3D seismic cubes directly rather than shot-by-shot simulation with subsequent CMP stacking. In order to do that the well known “exploding reflectors principle” is modified for 3D heterogeneous multiscale media. Its parallel implementation allows modeling of realistic 3D Common Middle Point stacks with reasonable computational costs. Numerical results for simulation of Common Middle Points sections and their time migration are presented and discussed.

Summary The process of seismic waves' propagation through 3D heterogeneous multiscale media is analyzed by means of finite-difference simulation using locally refined grids. In order to do reliable conclusion on the base of results of this simulation the digital geological model (3D distribution of P- and S-wave propagation velocities and density) is developed on the base of real life observations: 3D routine seismic processing, detailed well-logging analysis and laboratory study of core samples. Careful analysis of results of numerical simulation reveals intensive multiple scattering in the fluid saturated areas which are clearly observed in images of scattering energy. The same structures are presented in real field images of scattering energy and correlate with high permeability of deep wells.

The process of seismic waves’ propagation through 3D heterogeneous multiscale media is analyzed by means of finite-difference simulation using locally refined grids. In order to do reliable conclusion from results of this simulation the digital geological model (3D distribution of P- and S-wave propagation velocities and density) should be developed on the base of real observations: 3D routine seismic and detailed well-logging. Results of numerical simulation reveal appearance of intensive multiple scattering in the fluid saturated areas which are clearly observed in images of scattering energy. The same structures are presented in real field images of scattering energy and correlate with permeability of deep wells.