Optimal design of the parameters of U-shaped horizontal well for deep coalbed methane in southern Yanchuan

The coalbed methane field in the east edge of Ordos basin has the characteristics of "high storage and low permeability". In order to improve the production of deep coalbed methane of single well, the U-shaped horizontal well and its fracturing mode were designed based on the regional structural features, coalbed burial depth, gas content and hydrogeological characteristics. Through numerical simulation, the main factors that affect the output of horizontal well(such as the length of horizontal section and the fractured cracks)were studied. The results show that with the increase of horizontal section length, the output of coalbed methane increases gradually, when the horizontal section exceeds 800 m, the gas production will be reduced by about 10% per every 100 m. The number of fractured cracks and the half length of fractured cracks have great influence on gas production. The optimal number of fractured cracks is 4-5, and the optimum half length is 80-120 m. Fracture spacing and fracture conductivity have little effect on coalbed methane production. Field fracturing test proves that according to the optimal parameters of numerical simulation, CBM well S1 in this area is fractured. Under the same conditions, CBM production is more than 10 times higher than that of well S2 without fracturing.