A Practical Production Solution for Multilateral Horizontal Well in Natural Gas Hydrate: Superposition Principle and Reciprocity

Abstract

Abstract Due to high energy density, clean combustion products and abundant resources, natural gas hydrates (NGHs) have been regarded as an important clean energy source with the potential for large-scale development and utilization. However, pilot tests in NGHs show that their production rates are far below commercial needs. Multilateral well technology may lead to a solution to this problem because it can dramatically expand the drainage area of production wells. This paper presents a practical production model for multilateral horizontal wells in NGHs. In developing our solution to the diffusivity equation to model this process, we applied the superposition principle and reciprocity. We wrote the governing equation in cylindrical coordinates to describe the natural gas hydrate flow process. We used moving boundaries and dissociation coefficients to model the solid-to-gas transition process in hydrates. We used Laplace transforms and the Stehfest numerical inversion method to obtain solutions for flow in hydrate reservoirs. We applied the superposition principle and Gaussian elimination to obtain the desired solution for multilateral horizontal wells. We validated our proposed model with a commercial numerical simulator. We also performed sensitivity analyses to determine the effects on production behavior of the number of branches, dissociation coefficient, radius of the region with dissociated hydrate, and dispersion ratio. We used properties from the Nankai Trough as inputs in a case study we conducted.