Abstract
Fracturing design needs to consider the effect of proppant embedding as the production decreases rapidly due to proppant embedding after fracturing of coalbed methane wells. Coal fracture conductivity experiments were carried out to analyze the changes in coal fracture conductivity due to proppant embedding. A model of coal fracture conductivity was established considering proppant embedding. A proppant index method, which considers the dynamic change of conductivity over time, was adopted to establish a proppant embedding-based optimal design method for fracturing coal bed methane wells. The optimal design of coalbed methane wells in the southern block of Qinshui Basin was carried out. The results show that the fracture conductivity decreased with the increase of formation closure pressure. It increased with the rise of proppant grain size, number of placement layers, and Young's modulus of the formation. The simulation results were in good agreement with the indoor fracture conductivity experiments. The proppant embedding reduced the fracture width and fracture conductivity. The optimized fracture length considering proppant embedding decreased with an average decrease of 10.6%, and the fracture width increased with an average increase of 11.5%. Consideration of proppant embedment during fracture optimization of coalbed methane wells compared to no consideration resulted in a decrease in design fracture length, an increase in design fracture width, and a relative increase in average production. The validity and practicability of the method were verified, and it was of great guiding significance for the optimal design of fracturing in coalbed methane wells.