Problem of Acoustic Diagnostics of a Damaged Zone
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UTER SCIENCE
Problem of Acoustic Diagnostics of a Damaged Zone Corresponding Member of the RAS I. B. Petrova,b,*, V. I. Golubeva,b, and A. V. Shevchenkoa Received January 24, 2020; revised January 24, 2020; accepted February 29, 2020
Abstract—The problem of seismic wave propagation from a source located in a well is considered. Acoustic equations are used to describe the dynamic behavior of the fluid. The damaged zone is described as a porous fluid-saturated medium by applying the Dorovsky model. The elastic approximation is used to describe the dynamic behavior of the surrounding rock. A unified algorithm based on the grid-characteristic approach with curvilinear grids is proposed for full-wave modeling in the entire computational domain. Its distinctive feature is that the necessary contact conditions on the boundary between media with different rheological properties are stated explicitly. The possibility of acoustic diagnostics of the heterogeneity of the damaged zone is numerically explored. Keywords: mathematical modeling, grid-characteristic method, seismic survey process, porous media, Dorovsky model, damaged zone, fractured medium DOI: 10.1134/S1064562420020180
INTRODUCTION Seismic research methods are extensively used in oil and gas reservoir exploration and engineering, namely, in land and offshore seismic exploration, fullwave inversion, and crosswell seismic profiling. The discovery of unconventional oil and gas resources and the depletion of conventional fields have motivated the development of methods for more accurate recovery of internal medium structures. They would allow choosing an optimal engineering scheme, for example, to improve the efficiency of oil extraction. Substantial help with the development of new technologies can be provided by mathematical modeling, which is capable of producing synthetic wave fields for various source and receiver arrangements and models with a given complex internal structure. Thanks to the development of multiprocessor systems, much progress has been achieved in the creation of modern computational methods for solving seismic problems [1, 2]. Direct problems of wave propagation in heterogeneous media can be successfully solved numerically by applying the grid-characteristic method [3], which takes into account the internal mathematical structure of a hyperbolic problem,
namely, propagation of discontinuities along characteristics. Previously, this method was used to solve a number of direct problems in acoustic, elastic, layered, and fractured media [4, 5] in two- and threedimensional formulations and the inverse migration problem [6]. In this work, we consider the problem of acoustic sensing of a damaged near-well zone. The goal of the study is to develop an approach that explicitly takes into account the fluid-saturability and possible inhomogeneity of the zone, for example, the presence of a region with higher porosity and permeability. We construct a two-dimensional cylindrical model of the well, the surrounding colmatage zone, and the rock mass. The flui
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