Analysis of changes in the internal structure of low-permeability reservoir rocks by means of computed tomography after implementation of the directional unloading method

Abstract

The article presents the results of comprehensive studies of changes in the internal structure and evolution of filtration properties of low-permeability rocks of the Astrakhan gas-condensate field when implementing the method of increasing well productivity – the directional unloading method. Physical modeling of the deformation and filtration processes on the unique Triaxial Independent Load Test System of the Institute for Problems in Mechanics of the Russian Academy of Sciences was carried out. A 3D scan of rocks after testing was performed using a ProCon CT-MINI high-resolution X-ray tomograph in order to analyze changes in the internal structure. A digital model of the rock was obtained, and numerical simulation of filtration flow in GeoDict software based on the results of microtomography scanning was performed. Velocity fields and permeability values for different computational models and computation optimization methods are calculated. The results obtained in different filtration models are compared with the laboratory measured value of permeability. The main differences in approaches to numerical estimation of rock permeability are described, and conclusions about the applicability of the modeling techniques used are made. The research results allow us to conclude that the directional unloading method can be successfully applied to the conditions of the Astrakhan gas-condensate field, allowing to significantly improve filtration properties of rocks in the vicinity of the well.