Review on Main Controlling Factors and Key Simulation Techniques of Hydro-Fracturing Potential for Coalbed Methane Reservoirs: Recent Progress, Challenges, and Prospects

The study on the hydraulic fracturing potential of coalbed methane (CBM) reservoirs aims to assess the ability of coal seams to increase permeability and gas well productivity under the action of hydraulic fracturing. It provides a theoretical basis and technical support for optimizing reservoir fracturing design and improving the efficiency of CBM development, thereby addressing the issue of unstable production enhancement effects of the reservoirs. This review analyzes the primary factors influencing the hydro-fracturing potential of CBM reservoirs, taking into account both geological conditions and mechanical characteristics, and discusses the key physical and numerical simulation techniques for stimulating CBM reservoirs. Physical simulation techniques mainly focus on pore-fracture structure characterization, rock mechanics testing, logging interpretation, and injection falloff testing in the well. Numerical simulation technologies mainly focus on geomechanics simulation, digital core simulation, fracture propagation simulation, and fracturing operation simulation. There are many problems in the current research. The results of indoor tests differ significantly from the field application effects. The calculation accuracy of the evaluation parameters for the hydro-fracturing potential of CBM reservoirs is low. The construction of digital models is influenced by mathematical statistical methods, leading to the fallacy of equivalent cognition. The prediction of the fracturing improvement effect of CBM reservoirs faces systematic deviations in engineering applications. There is a lack of a comprehensive evaluation system that covers the coordination of multienergy systems, as well as environmental and economic factors. The analysis suggests that the breakthrough paths for future research should focus on the following aspects. Improve the physical compatibility between the experimental conditions and the actual reservoir environment. Innovate modeling methods that integrate geological measurement mechanisms and data-driven approaches. Establish a dynamic simulation system that covers the evolution of multi-scale fractures and the coupling of stress. Construct a multi-source dynamic evaluation system that integrates the goals of energy integration systems, environmental constraints, and economic benefits. This is to establish a geological-engineering collaborative research framework covering the entire time and space domain, thereby promoting the precise and efficient transformation of reservoirs and the efficient development of CBM.