Numerical Study of Lateral Layout in Multilateral Wells for Depressurization of Class 1 Hydrate Reservoirs with Boundary Sealing

Efficient development of marine natural gas hydrates (NGHs) remains challenging. Employing depressurization combined with complex structured wells and reservoir stimulation techniques is one of the key approaches to enhancing production. This study aims to theoretically evaluate the production response of different lateral layouts of multilateral wells under the conceptual condition of an idealized boundary sealing for the depressurization exploitation of Class 1 hydrate reservoirs. Based on data from China’s first offshore trial production, a numerical simulation method was used to systematically compare the development performance of various lateral layouts integrated with boundary sealing. Under the idealized modeling scenario, the simulation results indicate that the low-permeability barrier formed by boundary sealing can significantly suppress water invasion, promote pressure propagation, and thereby improve productivity. More importantly, optimizing the lateral layout can further enhance gas production performance. Under boundary sealing conditions, Case 8B with six downward-deployed laterals, compared to Case 1A without sealing and with six laterals in a planar staggered layout, its cumulative gas production (1733.75 × 104 m3) was 2.08 times that of Case 1A (831.68 × 104 m3), and its gas-to-water ratio (327.64) was 1.62 times that of Case 1A (202.09). This indicates that under boundary sealing conditions, lateral layout is one of the key levers to improve productivity. Under the modeling assumptions of this work, the research findings can provide a theoretical reference for evaluating the development of Class 1 hydrate reservoirs with multilateral wells where boundary sealing is considered.