EFFECTS OF INTRUSIVE IGNEOUS ROCK ON COAL-BED METHANE HORIZONTAL WELL PRODUCTIVITY

Choosing the Fuxin LiuJia Coal-bed Methane block as the study subject, a dual system seepage model is established in this study to simulate the dynamics of porosity and permeability resulted from pressure variation during gas desorption, diffusion and drainage. A geological model of heterogeneous coal-bed methane reservoir is also established involving complex geological tectonics. The influence on the productivity of horizontal wells from igneous rock intrusion is analyzed. Results show that the pressure expansion of Coal-bed Methane reservoir is remarkably affected by complicated geological tectonics. Locating a horizontal well SPJ1 in between two igneous rock zones leads to a substantial pressure drop and large methane desorption area in the middle of the two zones. On the other hand, when a horizontal well SPJ2 is located between the igneous rock zone and a fault zone, the effect of weaken fault and an appropriate distance from the northern igneous rock zone need to be taken into consideration. Modelling results show that 140m is the optimal distance from the igneous rock zone, where the maximum pressure drop and coal-bed methane production are detected. The comparison between SPJ2 and SPJ1 suggests that horizontal wells in LiuJia block be placed at SPJ2.