Low-cost drilling and completion techniques for coalbed methane in southern Qinshui Basin,Central China

The southern Qinshui basin is rich in coalbed methane(CBM),it is the first area that obtained good results in the commercial development of CBM in China.No.3 layer,the main producing zone,is buried shallow and the formation pressure is stable.So the low-cost drilling techniques,such as the small rig,second-spudding well structure and air or clean water drilling can satisfy the production demand.Based on the special requirements in the CBM development,such as drilling geology,draining water during gas production and low cost technology,this article establishes the optimum trajectory model of cluster wells for producing CBM,and makes a in-depth study on the optimum design of well trajectory and the composition of drilling tool.It also evaluates the economic benefits of low-cost vertical wells and four-well-composition cluster wells.The result indicates that CBM can be produced with high profits using the low-cost drilling and completion techniques.The four-well-composition cluster well technique is cheaper than the vertical well and may save 4.518% of the total drilling cost.