Research on Optimal Design of Fracture Parameters for Horizontal Wells Multi-Stage Fracturing in Coalbed Methane Reservoirs

Hydraulic fracturing has become a key technology for developing unconventional coalbed methane reservoirs. Fracture parameters directly affect the fracture propagation patterns and the effect of hydraulic fracturing. However, how to optimize fracture parameters to improve coalbed methane recovery after fracturing is still unclear. In this study, combined with Petrel and WellWhiz3.3 numerical simulation software, a fracture propagation model of multi-stage fracturing in the horizontal well and a postfracturing production simulation model were established based on the basic characteristics of the coalbed methane reservoir in the Daning-Jixian block. The model was used to investigate the mechanism of the influence of cluster number and cluster spacing on the fracture propagation pattern of multi-stage hydraulic fracturing in horizontal wells, and revealed the impact of stage cluster ratio, fracturing stages number, cluster spacing and fracture half-length on the productivity of horizontal well after fracturing. Numerical simulation results show that: competitive propagation behavior exists among fractures when multiple clusters of fractures initiate and propagate simultaneously. The exterior fractures will suppress the extension of inner fractures and the complexity of fracture competitive propagation behavior increased with the number of clusters and the reduction of cluster spacing. Moreover, the cumulative gas production of the gas wells increases with the increase of stage cluster ratio, number of fracturing stages and half-length of fractures, and initially increased and then decreased with the increase of cluster spacing. Overall, this study can aid in improving the productivity of horizontal wells in coalbed methane reservoirs, thereby enhancing the economic feasibility of coalbed methane development.