Experimental study on the influence of well inclination angle of coalbed methane well on the cementation strength of cement-formation interface

In order to control the problem of water channeling in the process of coalbed methane(CBM) production, based on the self-designed test device and method, the test data of the shear strength at cement-aquiclude interface (CAI) is obtained under the conditions of well inclination of 0°, 30°, 60° and 90°. The mechanism of the influence of inclination angle on the shear strength at CAI is analyzed. The results show that the shear strength at CAI decreases with the increase of the inclination angle. The reason is that as the inclination angle increases, the upper part of the mud cake ring becomes thinner in turn, and the lower part becomes thicker in turn. When the inclination angle is 90°, the mud cake is thickest. As the mud cake thickens, the clay minerals in the mud cake is decreasing, and the content of drill cuttings and barite increase. Through the analysis it is also believed that the main factors affecting the shear strength at CAI are cohesion, moisture content, grain compaction, particle structure and mineral composition in the mud cake. Therefore, the CBM well type has a great influence on the hear strength at CAI. If the horizontal well is used to extract CBM, the problem of water channeling may be more prominent.