Operation parameter optimization of a gas hydrate reservoir developed by cyclic hot water stimulation with a separated-zone horizontal well based on particle swarm algorithm

• Cyclic hot water stimulation by separated-zone well to develop gas hydrate was studied.
• Operation parameters of this method was optimized by maximizing net energy via PSO.
• Production characteristics and feasibility of this method were evaluated.

This paper numerically investigated the production characteristics of a gas hydrate reservoir by cyclic hot water stimulation with a separated-zone horizontal well, which combines depressurization and thermal stimulation to improve the development effect. A class II conception model of a heterogeneous gas hydrate reservoir was established based on the reservoir parameters of the China Shenhu area. Optimal operation parameters of this method was determined by maximizing the net energy via PSO (particle swarm optimization). The results show that: (1) high gas production rate (>2 × 104 m3/d) and high energy ratio (>100) can be obtained using this method. (2) The gas hydrate in the low-permeability area can be recovered effectively, and there is a comparatively uniform cumulative gas production along the horizontal well, indicating the feasibility of the production scheme in recovering heterogeneous gas hydrate reservoirs. (3) To gain high net energy, the temperature of the injected water, the lower gas production rate limit of each cycle, the total amount of injected water and the injection rate should be maintained at high levels within the allowed range; For each segment, the amount of water and the injection rate should remain at a comparable level between areas with high and low permeability, whereas the injection rate should be lowered in the middle areas.