Study of Multibranch Wells for Productivity Increase in Hydrate Reservoirs Based on a 3D Heterogeneous Geological Model: A Case in the Shenhu Area, South China Sea

Abstract

Summary So far, a total of 11 hydrate trial production projects have been carried out all over the world, all of which used a single vertical well or horizontal well to carry out hydrate production by the depressurization method or depressurization combined with other methods. These traditional production methods have some limitations: The single vertical well has a small contact area with the reservoir, and the transmission range of the temperature and pressure is limited; therefore, the productivity is low. The horizontal well can improve hydrate productivity from magnitude order; however, there is a long distance from the standard of commercial production of marine hydrate. Therefore, it is an inevitable trend to find a highly efficient and advanced drilling technology for heterogeneous hydrate reservoirs. The multibranch wells based on horizontal wells can not only increase the contact area between the hydrate reservoir and well by branch structure to improve the conductivity of the reservoir temperature and pressure but also improve the hydrate productivity by laying the branch at high hydrate saturation for areas with extremely uneven distribution. Therefore, for this paper, we chose the Shenhu area as the research area to establish an approximate realistic 3D heterogeneous geological model contained with hydrate, then we laid the multibranch wells based on horizontal wells in high hydrate saturation area and optimized the branch direction, location, and spacing, and the production increasing effect was assessed. Finally, an optimal multibranch well scheme was obtained under the conditions of this paper setting, which is as follows: The vertical multibranch well was set at the root end of the horizontal main well with a branch spacing of 10 m, and the productivity after optimization was 31.64% higher than that before optimization.