Enhanced gas production of silty clay hydrate reservoirs using multilateral wells and reservoir reformation techniques: Numerical simulations

Multilateral wells and reservoir reformation techniques are widely employed to increase yield for spatially heterogeneous oil and gas reservoirs. However, the multilateral wells integrated with reservoir reformation have not been evaluated for low-permeability silty clay hydrate reservoirs before. Here, the multilateral well schemes without and with reservoir reformation technologies including burden sealing and hydraulic slotting were proposed, and their production behaviors under depressurization were evaluated and compared to that of a vertical well using available data in the South China Sea. The results show that the multilateral wells significantly enhance gas extraction because of a synergistic inter-borehole depressurization and an increase in production interval. Increasing branch hole number can further promote the synergistic effect and involved area, which enhances more hydrate dissociation, but this stimulation effect decreases with the extension of the production cycle in the silty clay reservoirs. The multilateral well with the hydraulic slotting is more suitable for short-term field trials and the burden sealing is better for long-term gas recovery. Combining hydraulic slotting or fracture and burden sealing technique at different production stages would be an extremely promising way for a multilateral well design to achieve long-term stable and high gas production in the low-permeability hydrate reservoirs.