The effect of anisotropy оn the elastic properties of rock

Abstract

With the growing interest in hard-to-recover hydrocarbon reserves, there is a need to increase the detail and quality of modeling the rock mass and reservoir formation. Taking into account the mechanical anisotropy of the medium, in particular caused by the layering of thin layers, provides a more complete picture of the stress-strain state of both the reservoir formation itself and barriers / bridges, which in turn opens up additional opportunities for optimizing the processes of field development, increasing the efficiency of hydraulic fracturing, as well as drilling wells. The technology of conducting laboratory studies of core material to study the anisotropy of elastic properties is described in the present study. Based on the results, the correlations for the elastic characteristics of rocks of the Sortym, Bazhenov and Abalak formations were obtained. Using the example of one of the deposits in Western Siberia, the results of constructing two types of hemechanical models (isotropic and anisotropic) are demonstrated. With the reference to comparison of values of the minimum horizontal stress and the absorption onset gradient, it is shown that the anisotropy of elastic properties has a significant effect on the stress-strain state of the rock mass. The use of isotropic models for anisotropic media leads to a significant underestimation of horizontal stresses / gradients of the onset of absorption, which, in turn, does not allow to unlock the potential of hydraulic fracturing, as well as to choose the optimal depth range for casing descent, which is critically important when drilling wells under conditions of AHFP. The obtained dependences can be used as a priori information in constructing geomechanical models of these objects in Western Siberia.