Evaluation of the Gas Production Enhancement Effect of Boundary Sealing and Near-Wellbore Stimulation for Class 1 Hydrate Reservoir Step-Wise Depressurization with a Horizontal Well

Natural gas hydrates (NGHs) currently lack economic feasibility; efficient exploitation methods must be continuously explored to increase their production capacity. Drawing on field data from China’s first offshore NGH trial production, a numerical simulation method was used to evaluate a comprehensive development strategy that combines a horizontal well with boundary sealing, near-wellbore stimulation, and step-wise depressurization to improve the recovery of Class 1 NGH reservoirs. The results indicated that boundary sealing has a strong enhancement effect: it inhibits water invasion and thus concentrates the energy for hydrate dissociation. The use of high-pressure water jets for near-wellbore stimulation generates highly permeable channels, greatly accelerating hydrate dissociation and gas flow; step-wise depressurization optimizes the production behavior by controlling water production. The combined application of these technologies significantly improves development performance, with cumulative gas production (Vg) increasing to 220.1% and the gas-to-water ratio (Rgw) increasing to 102.6% compared to the base case, providing an effective strategy for the development of Class 1 NGH reservoirs.