关键词: 深层煤层气, 大规模压裂, 动态地应力, 水平井, 应力场研究

Abstract:

China’s deep coalbed methane demonstration base has been preliminarily established and is gradually entering an important stage of large-scale exploration and development. This breakthrough has brought new opportunities and challenges to the energy sector. With ongoing development, traditional 3D static models have proven inadequate for predicting the dynamic in-situ stress evolution of coupled seepage-stress interaction in strongly heterogeneous reservoirs under large-scale horizontal well fracturing conditions. In response, this study takes the deep coalbed methane reservoir in the Daning-Jixian block as an example to conduct in-depth investigation of the dynamic stress field during reservoir fracturing. This study adopts an integrated geological engineering fracture network model for coalbed methane reservoirs to simulate the horizontal well platform fracturing process, comprehensively considering both geological conditions and engineering factors, thereby more accurately reflecting the actual situation. A time-dependent simulation study of the dynamic stress field during large-scale fracturing for horizontal well platform S was carried out. The results indicate that after multiple rounds of fracturing-induced stress superposition, the present in-situ stress distribution has undergone significant alterations. In order to quantify this impact, a key indicator—the horizontal principal stress difference coefficient, defined as the ratio of the two horizontal principal stresses—was introduced. When this coefficient approaches 1, it indicates an optimal fracturing effect. The simulation results show that the range of the horizontal principal stress difference coefficient in the post-fracturing area gradually decreases from 1.15-1.25 to 1.05-1.15, with most areas around the well exhibiting a value of less than 1.10, demonstrating that the large-scale fracturing in horizontal wells is effective. This research achievement not only provides a more reasonable simulation method for the large-scale fracturing development of deep coalbed methane, but also offers a scientific basis for optimizing fracturing design and improving coalbed methane recovery. Through an integrated geological engineering method, it is possible to more accurately predict and assess the dynamic stress field changes during the fracturing process, thereby guiding the fracturing operations in actual production.

Key words: deep coalbed methane, large-scale fracturing, dynamic in-situ stress, horizontal well, stress field study