Research on the prediction of permeability distribution characteristics of shale reservoirs based on current tectonic stress field: case study of the Feng’gang Shale Gas Block III in the northern Guizhou area, China

Abstract

Prediction studies of the permeability distributions of shale reservoirs are important for advanced predictions of potential shale gas exploration sites. Therefore, accurate predictions of the permeability distributions in these areas are critical to facilitate the efficient exploration and development of shale gas reservoirs. In this paper, using relevant drilling data, a mathematical relationship was established between geostress and shale reservoir permeability. The study revealed that the shale reservoir permeabilities decrease exponentially as the principal stress increases. By integrating the current tectonic stresses in the northern Guizhou area that were obtained from the anelastic strain recovery method measurements, as well as drilling and seismic data, we have developed a reasonable geomechanical model of the study area. On this basis, we established a 3D mathematical model of the shale reservoir in the Niutitang Formation of the Feng’gang Shale Gas Block III via ABAQUS finite element software. The model simulates current tectonic stress field data and predicts the permeability distribution within a reservoir. As a result, we obtain a reliable model for evaluating the permeabilities of shale reservoirs. The results of the simulation show that the current tectonic stresses are influenced by variations in rock features across fracture zones, fold zones, and normal sedimentary layers. Reservoir permeabilities are affected by the current tectonic stress and complex geological structures. Notably, high permeability values are typically concentrated along fracture zones and at their intersections with sedimentary layers, with the highest values occurring at the endpoints of fracture zones and where two fracture zones meet. Some fold zones exhibit gradual increases in permeability outwards from the damage zone caused by the disruptive effect of the fracture zone.