Abstract:
Coal-measure gas co-production represents a pivotal approach to enhancing unconventional natural gas production in China. However, the material composition and physical characteristics of coal-measure gas reservoirs vary significantly, introducing uncertainty in the fracture propagation mode and degree of fracture development in different reservoirs during the fracturing process of coal-measure gas reservoirs. Effective coordination of multiple reservoir transformations for achieving multiple gas co-recovery is crucial for minimizing development costs and maximizing production capacity. This study focuses on the Linxing block, located on the northeastern margin of the Ordos Basin. It analyzes the geological and engineering factors influencing the fracturing effectiveness of Coal-measure gas reservoirs. Utilizing numerical simulation technology, the study simulates the propagation patterns of fractures in various reservoirs and proposes recommendations for multi-reservoir hydraulic fracturing in the Linxing block. The results show that the increase of the minimum horizontal in-situ stress difference, tensile strength difference, pumping displacement, and viscosity of the reservoir and barrier is conducive to the expansion of fracture height and width, and the higher the value, the greater the penetration capacity of the fracture. Specifically, the minimum horizontal in-situ stress and fracturing fluid viscosity of the rock layer primarily influence fracture width, where a larger relative minimum horizontal in-situ stress or lower fracturing fluid viscosity results in narrower fractures. Additionally, variations in the difference between the elastic modulus and Poisson's ratio of the reservoir have minimal impact on the overall fracturing effect, although an increase in the elastic modulus difference reduces the time required for fractures to penetrate through the bed, enabling faster attainment of ultimate height fracture. Based on these insights, the study proposes an optimal scheme and drainage recommendations for coal-measure gas co-production reservoirs in the Linxing area. Specifically, reservoirs with a minimum horizontal in-situ stress difference of 0~4 MPa and a tensile strength difference exceeding 4.5 MPa should be prioritized for co-production fracturing, utilizing larger pumping displacements to achieve more efficient resource development.