Summary The exploitation of marine natural gas hydrates is frequently hindered by poor reservoir permeability and low single-well productivity. Hydraulic fracturing serves as a key technology to enhance reservoir permeability and improve well productivity. Furthermore, thermal stimulation methods, which promote hydrate dissociation by directly injecting hot fluids into the reservoir, have proved effective in increasing permeability and boosting single-well production. In this study, we investigate a combined hydraulic fracturing and thermal stimulation strategy to enhance recovery from these challenging environments. We developed a numerical simulator using the embedded discrete fracture model (EDFM) to analyze the coupled thermo-hydromechanical processes and multiphase flow dynamics during thermal recovery. The simulations reveal that the design of the fracture network and the operational injection/production parameters are critical determinants of development efficiency. The numerical simulation results show that an asymmetric conductivity profile, with higher conductivity at the production well than the injection well, optimizes the injection/production balance compared to conventional symmetric designs. An optimal well spacing of 70–90 m maximizes reservoir sweep efficiency while preventing premature water breakthrough seen at closer distances. Moderately deviated fracture geometries enhance the uniformity of thermal front propagation, improving heat utilization. While a sufficient number of connected fractures is essential for establishing an effective 3D recovery network, excessive connectivity can lead to severe water breakthrough in later production stages, significantly compromising well productivity. Water breakthrough causes a 20% decline in daily gas output and a 10.12% loss in total production by Day 100 while wells are fully connected. This work provides a theoretical framework and practical guidance for optimizing the design and efficiency of fracturing-thermal recovery operations in marine natural gas hydrate reservoirs.
Cui et al. (Sun,) studied this question.
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