Characteristics of in-situ stress field and its influence on coal reservoir permeability in Enhong Basin of Eastern Yunnan Region

:The present in-situ stress field is an important factor for exploration and development of coalbed methane (CBM), which affects the permeability of coal reservoirs and the formation and spreading of hydraulic fractures. A large volume of coalbed methane resources distributes in Enhong Basin of eastern Yunnan region in China. However, current studies on the in-situ stresses in this area are rare, which limits the efficient development of coalbed methane. In order to solve above problems,this paper studies the characteristics of present in-situ stress distributions in this area using the finite element numerical simulation method. The Upper Permian Xuanwei Formation No.16 coal seam was selected as the research target and comprehensive analysis of the measured in-situ stress in the study area was conducted.The results show that the shallow coal layers are in the stress region of strike-slip faults while the deep coal layers are in normal faults stress region. The maximum principal stress of No.16 coal seam of Xuanwei Formation in Enhong area is between 11.0 MPa and 38.9 MPa, with higher stress in the southwest and lower stress in the north and southeast. The distributions of presentin-situ stress are affected by tectonic movements, with lower value in fault and fold development area. Different faults and folds affect the distributions of in-situ stresses differently. It is also found that the present in-situ stress has in significant influence on the permeability of coal reservoirs while the stress mechanism has significant influence on the permeability of coal reservoirs.