Effects of perforation degree and deployment position of multilateral horizontal wells on gas production from inclined clay hydrate reservoirs

Natural gas hydrate (NGH) is generally disseminated in inclined mud sediments in South China Sea (SCS), China. It is of great significance to investigate the production performance of multilateral horizontal wells in actual inclined NGH reservoirs. We implemented a real 3D inclined clay hydrate reservoir model based on geological and topographical data from the site X01, Shenhu Area, SCS, to simulate the production performance of multilateral horizontal wells with TOUGH+HYDRATE software and verified the modeling method. We studied the effects of perforation degree on the production performance of multilateral horizontal wells. The differences in production were compared when multilateral horizontal wells were deployed at different tectonic settings of NGH reservoirs (i.e., structural high position, inclined position, and structural low position). The optimal well configuration and placement position were determined. Results show that multilateral horizontal wells that are perforated simultaneously in horizontal branch and vertical main well are beneficial to enhance NGH dissociation and gas production. However, the perforation section of vertical main wells should not be too long. The optimal length ratio of vertical main well and horizontal branch is 0.5～1.0. Moreover, the inclination of the hydrate reservoirs affects significantly the production performance of multilateral horizontal wells. Comparatively, deploying multilateral horizontal wells at horizontal places at low structural positions of clay hydrate reservoirs is conducive to long-term and efficient production of NGH.