Abstract:

The DaningJixian Area is one of the key areas of coalbed methane exploitation in China. The modern stress principally controls the coal reservoir permeability. This paper explored a stress evaluation method and technique process fitted for coal reservoir, based on the analysis and calculation of well log for coalbed methane exploitation. The study has revealed that the maximum and minimum horizontal principal stress of the 5# coal seam has a general waving variation trend of lowhighlowhigh from the east to the west of the DaningJixian Area; The vertical principal stress has a general variation trend of low in East and high in West, but the increasing trend decreases in the middle area with complex geological structures. The 5# coal seam is generally under the stress transition depth, and is significantly affected by the vertical principal stress, which is in favour of the stretch of coal seam fracture and the increase of permeability, as in a tension stress environment. The orientation of the maximum horizontal principal stress is close to the development direction of the dominant fracture, which benefits the stretch of the fracture and results in the improvement of the coal seam permeability. There is a higher permeability in the areas of low minimum principal stress and of high principal stress difference.

Key words: DaningJixian Area, stress, coal reservoir, permeability