Study on the Influence of Complicated Geological Condition Permeability in Coal Reservoirs on Horizontal Well Drainage and Production

Abstract

Based on the engineering background of coalbed methane block in Liujia District of Fuxin with complex geological conditions, a seepage mathematical model considering the dynamic changes of porosity and permeability of coal reservoir caused by coal matrix shrinkage under the conditions of gas adsorption, desorption, and stress change is established. A geological model of heterogeneous coalbed methane reservoir is established, which includes igneous rock and fault geological structure. The influence of permeability on coalbed methane productivity and reservoir pressure under complex geological conditions is studied by numerical simulation. The results show that the permeability of coal seam is an important factor affecting the yield of coalbed methane. The higher the permeability, the faster the output rate of coalbed methane, the higher the output, the faster the pressure drop of coal reservoir, and the faster the desorption rate of coalbed methane. Under the premise that the horizontal wellbore is perpendicular to the maximum permeability direction of the coal seam, the productivity of the well arrangement method is higher than that of the parallel maximum permeability direction. However, the length of the horizontal well in the Liujia block is limited by the dense igneous rock distribution, and the desorption area of the coalbed methane is reduced and the production is reduced when the vertical arrangement is arranged. Therefore, the horizontal wells in the Liujia block should be parallel to the maximum permeability direction and set along the direction of igneous rock. The greater the vertical permeability of the coal seam, the faster the reservoir pressure decreases, and the better the horizontal well productivity.