Novel Wellbore–Reservoir Coupling Fluid Flow Model for Natural Gas Hydrate Production

The exploitation of natural gas hydrates, strategic emerging energy resources, involves complex physical processes coupling heat, mass transfer, and phase change. Current hydrate exploitation numerical simulations mainly focus on the reservoir, treating production wells as pseudoporous media and ignoring non-Darcy flow in the wellbore. Such simplification causes multiphase flow resistance calculation errors, impeding an accurate description of transient temperature and pressure field changes and a precise depiction of the dynamic evolution between hydrate decomposed gas production and multiphase flow migration. Based on the Tough+hydrate code, this study introduced the Drift Flux Model and multiphase momentum conservation equations. A wellbore–reservoir coupling model considering kinetic-potential energy conversion was established, and the Tough+Hydrate Wellbore–Reservoir simulation code was developed. Taking China’s Shenhu Sea hydrate production test as a case, the temperature, pressure, and multicomponent distribution of the wellbore–reservoir system were obtained. The findings show: (a) Wellbore turbulence reduces flow resistance by 30–40%, and the calculated gas production peak by the TH + WR code is 13% higher than traditional models. (b) Non-Darcy flow increases the pressure-drop front propagation speed by 20% and expands the low-pressure influence range by 18%. (c) Wellbore high-speed flow enhances heat exchange, raising near-well temperature by 1.5–2.0 °C during stable production, accelerating hydrate decomposition by 15%. (d) The gas production prediction error is less than 8%. These results advance the natural gas hydrate exploitation field, providing theoretical and technical support for understanding wellbore–reservoir coupling, optimizing production schemes, and improving the exploitation efficiency.