Optimization of a multi-fractured multilateral well network in advantageous structural positions of ultralow-permeability hydrate reservoirs.

In this study, we propose a production enhancement strategy that combines multiplanar fractures with a multilateral well network, namely multi-fractured multilateral well network (MMWN), to improve the production efficiency of ultralow-permeability hydrate reservoirs (ULPHs). Considering that natural gas hydrate is generally disseminated in nonhorizontal strata, the influence of topography on the productivity of multilateral wells was first revealed, and then the stimulation effects of MMWN with different geometries and properties in advantageous structural positions of ULPHs on gas production were systematically analyzed. Results indicate that gas extraction from multilateral wells is good at the structural low of ULPHs. MMWN significantly increased the stimulated reservoir volume, leading to an increase in gas production by more than 23 times compared to using the depressurization method alone. Using the MMWN did not require extra energy and caused no ice formation. Improving the planar fracture number, area, width, and permeability effectively facilitated gas recovery. Enlarged fracture spacing is suitable for long-term production. Gas production is not influenced by porosity, overlarge width, or high permeability (over 10 D) of planar fractures. This novel study suggests that the combination of multilateral well networks and highly intensive reconstruction is an effective method to produce gas hydrates. • Multi-fractured multilateral well network (MMWN) is proposed. • Favorable deployment of structural position and fracturing strategy revealed. • Structural low of reservoir is most suitable for multilateral wells to extract gas. • Appropriate geometry and properties of multi-planar fractures are necessary. [ABSTRACT FROM AUTHOR]