Application of the Inversion Stress Model for Estimating the Parameters of Fault Tectonics

The purpose of this work is to determine the parameters of fault tectonics by constructing an inversion stresses model with a weak quality of the seismic survey, as well as identification of compression and extension sectors by the structural-geomorphological method (SGM) in subsalt productive sediments. The tasks for achieving the goal of the paper: analysis of the quality of available information about fractures within the studied oil deposit, calculation of the inversion stress model, identification of the compression and extension sectors according to the SGM. Reconstruction of stress fields in conjunction with geomechanical analysis is a tool for studying the patterns of fracture development in rocks and tectonic evolution of the region. Determination of fault parameters and allocation of zones of intensive fracturing allows optimizing trajectories when drilling horizontal and inclined wells, assuming intervals of potential drilling complications, predicting risks during fracturing operations, and qualitatively evaluating the reservoir properties by deformation sectors. As inputs to the calculation of the inversion stress model, disjunctive dislocations that are confidently identified by seismic data and records of an electrical microimager appear. Based on information about the spatial location of the actual cracks and faults, the orientation of the tectonic force contributing to the formation of this fault system is calculated. The result of the construction of the inversion stress model are maps of displacement and deformation fields. Analysis of these maps in zones with different values of displacements and deformations allows to single out low-amplitude disjunctive dislocations, which are ambiguously determined when interpreting seismic survey. The calculation results are calibrated for microimager data, special core studies, drilling data. The initial data for the structural-geomorphological method are topographic maps, space images and digital surface models. As a result of applying the structural-geomorphological method, it is possible to reconstruct the orientation of the axes of compression and stretching of neotectonic stresses in the horizontal plane, determine the direction of the shear displacement along the fault (right or left shear), reveal additional stressed conditions in the formation of the fault, and identify the compression and extension sectors. Approbation of these methods was carried out at the oil field of the Leno-Tunguska oil and gas province of the Siberian platform. Based on the results of the calculation, a small-scale map of fault tectonics was compiled within the studied oil deposit. Further use of this map is planned as a basis for calculating a 3D geomechanical model and selecting a development system. In the process of obtaining new information (data on core research, microimages, drilling data), a map of fault tectonics will be modified.