Enhanced gas production from silty clay hydrate reservoirs using multi-branch wells combined with multi-stage fracturing: Influence of fracture parameters

Abstract

Natural gas hydrates are typically deposited in low-permeability clayey-silty sediments with low gas production. The two main methods for enhancing gas production are complex structural wells and hydraulic fracturing. However, using only one of those methods does not significantly increase gas production. Herein, a method of combined multi-branch well with multi-stage fracturing was proposed. A novel evaluation method for increased gas production under fracturing was first proposed to reveal the effects of fracturing domain area and number. Then five fracturing distribution models were designed and analyzed. Results indicate that the combined method increased the gas recovery ratio by 829.13% and the hydrate dissociation ratio by 710.34% compared to branching wells because of enlarging pressure propagation and communicating deep thermal fluids. The dissociation of hydrates is enhanced by an increase in the area and the number of fractures, but the rangeability of the increased stimulating effect declines. Different fracture distributions influence production performances at different stages. Short-term production is beneficial when fractures are in the branch well centers. Long-term gas production can be improved when fractures are mainly located at the branch distal end. This novel study has important implications for commercial exploitation at different production stages.