Distribution and evaluation of geostress in coal reservoirs in Xishan block, Taiyuan

Geostress is a key parameter affecting the development of coalbed methane, in order to analyze the geostress conditions of Xishan coal reservoir in Taiyuan and provide theoretical basis for exploration and development of coalbed methane, the geostress was measured by hydraulic fracturing, the geostress data of 35 coal reservoirs in Taiyuan Xishan mining area were statistically analyzed, the correlations and their models between geostress of No.2 coal seam in Permian Shanxi Formation and the burial depth of coal seam were established, and the present geostress conditions and controlling mechanism were clarified. The results show that the average value of the fracture pressure gradients, closure pressure gradients and coal reservoir pressure gradients of No.2 coal seam in the study area are 4.77 MPa/hm, 2.82 MPa/hm, 0.6 MPa/hm respectively. The average value of the minimum horizontal principal stress gradients, the horizontal principal stress gradients and vertical principal stress gradients are 2.82 MPa/hm, 3.24 MPa/hm and 2.7 MPa/hm, respectively. The principal stress increased linearly with the burial depth. According to the minimum horizontal principal stress, the study area was divided into low stress zone, moderate stress zone and high stress zone, and the stress state of each zone was defined.