Hydro-mechanical coupled numerical investigation of coalbed fracturing under the influence of orthogonal cleats

The strategic development of coalbed methane resources presents a viable solution to mitigate the depletion pressure on conventional natural gas reserves, garnering increasing global attention as an unconventional energy alternative. Pre-fracturing numerical modeling of fracture propagation based on reservoir geomechanical properties and geological characteristics provides critical insights for optimizing completion designs, thereby reducing operational expenditures and minimizing. Nevertheless, the inherent complexity of coal reservoirs characterized by well-developed cleat systems and natural fracture networks poses significant modeling challenges. This study introduces a MATLAB-based automated data interface for batch processing of discrete fracture networks, enabling efficient simulation of hydraulic fracture interaction with preexisting discontinuities. The results reveal that as the angle between the natural cleats and the minimum horizontal principal stress increases, the fracture area expands, with cleats at 45° and 135° achieving maximum stimulation efficiency. An excessive horizontal stress difference prevents the formation of a fracture network, while fracturing operations in coalbed with lower horizontal stress differences may produce better results. An excessively high horizontal stress difference inhibits the formation of fracture network, whereas fracturing operations in coalbeds with lower horizontal stress differences are more likely to yield favorable outcomes. The presence of natural cleat system introduces additional complexity to hydraulic fracture propagation by facilitating the unpredictable opening of interface planes. In this study, configuring five clusters of fractures with a cluster spacing of 12.5 m yields the optimal fracturing effect.