Visualization and investigation of the erosion process for natural gas hydrate using water jet through experiments and simulation

Abstract

Natural Gas Hydrate (NGH) and Hydrate-bearing Sediments (HBS) are emerging as an important potential energy resource. Radial Jet Drilling (RJD) technology, turning sharply in the casing and drilling laterals by using water jet, is a valid approach to solve problems of high cost, low efficiency during the exploitation of NGHs. The performance of water jet drilling remains unclear, and traditional finite element methods cannot accurately depict the water jet drilling ability due to mesh distortion. This paper analyzes the water jet erosion process of NGH and HBS. Experiments on the erosion of reconstituted gas hydrates are conducted and visualized in both submerged and submerged confining pressure conditions. Subsequently, two coupled nozzle–target models are solved by Arbitrary Lagrangian Eulerian (ALE) and Smooth Particle Hydrodynamics (SPH) methods. The flow field, the deformation and erosion of the hydrates induced by water jet are simulated. The experimental results show that there are specific shapes of cylindrical erosion pits for NGH and HBS. The numerical results are consistent with the experiments, which proves the effectiveness of water jet exploring hydrate resources. The submerged condition and the confining pressure condition will hinder the erosion efficiency, and the critical erosion velocities for both HBS and NGH are obtained. ALE method has superior accuracy in modeling the damaged area and erosion pit characteristics; while SPH method, has advantages in showing the motion state of the single particles and unstable and discontinuous flow field. This paper provides a good guidance for understanding the water jet drilling performance and selecting the appropriate simulation method in NGH reservoirs development.