An Integrated Geology and Engineering Workflow for Optimal Hydraulic Fracturing Design in Deep Coalbed Methane Multiwells Pads

Abstract The extraction of methane from deep coal seams (over 2000 meters) has gained increasing attention recently. The deep coal seams present distinct characteristics, including lower reservoir permeability, higher in-situ stress, and stronger plastic deformation, when compared to shallower coal seams. An effective hydraulic fracturing design is crucial, taking into account sophisticated geological information and realistic, three-dimensional fracture networks. However, conventional fracturing design methods has challenges of timeliness and adaptability, particularly regarding the fracture-driven interactions (FDIs) among multiple wells. Here, we proposed an AI-driven workflow that integrates a geological model, fracture propagation model and reservoir simulator. An algorithm was introduced to quantify the spatial overlap of grid cells between wells, enabling the establishment of a multi-objective optimization model targeting both stimulated reservoir volume (SRV) and FDIs. AI-assisted automated history matching facilitates rapid and reliable fracturing optimization design. The proposed framework was applied on two multiwells pads in Linxing and Shenfu deep coalbed methane (CBM) field at the eastern edge of Ordos Basin. In Linxing field, the vertical-height separation between the laterals of two adjacent wells in a multiwells pad is 10~20 m (in a cross-sectional view). Special fracturing treatment design and parameters were considered to control the fracture height in case of fracture hit. In Shenfu field, a nine-wells pad was investigated. The completion design effectiveness of the proposed workflow was verified through these field applications. The framework explicitly predicts the fracture swarms and determines optimal pumping schedules based on the effective permeability area (EPA), SRV, estimated ultimate recovery (EUR), and FDIs. Furthermore, our findings suggest that multi-round diverting fracturing (combined with temporary plugging) is suitable for exploiting deep CBM resources. The results provide valuable insights into the selection of optimal completion parameters and the development of effective strategies. The key insights from this research are expected to serve as a theoretical guide for the effective development of deep unconventional resources.