Experimental study on natural gas hydrate production under different heat injection well patterns

Abstract

Natural gas hydrate is an alternative energy source with both reserve advantages and environmental friendliness. Thermal stimulation is a common method for extracting natural gas hydrate, and how to improve the extraction efficiency of natural gas hydrate by optimizing the layout of thermal injection well pattern is a subject worthy of in-depth exploration. This study conducted three sets of hydrate decomposition experiments in a pilot-scale hydrate simulator (PHS) with an effective volume of 117.8 L under different thermal injection well pattern conditions, including single-point heating, two-point heating, and four-point heating. The gas-water production characteristics and heat transfer processes of the three experimental groups were analyzed, and the real-time decomposition rate and energy efficiency ratio of hydrate decomposition under different extraction methods were quantitatively investigated. Experimental results show that under conditions of consistent total heating rate and hydrate saturation, the cumulative gas production of the experiments remained essentially the same, but increasing the density of heat source arrangements shortened the hydrate extraction time. Compared with two-point and single-point heating, four-point heating intensified heat diffusion, but the reservoir temperature gradient in the four-point heating system decreased compared to single-point and two-point modes. Increasing the density of heating points improved heat exchange efficiency, but the dispersed arrangement of heat sources also increased heat losses. The two-point configuration exhibited the highest gas production rate and energy efficiency ratio, followed by four-point, while single-point showed the lowest values. These results may hold implications for optimizing thermal injection well patterns in trial production projects and future commercial exploitation of natural gas hydrates.