Feasibility Analysis on Hydrate Exploitation by Heat Generation Powders Thermal Stimulation

Abstract

A rigorous study was conducted to assess the potential of a novel “in situ heat generation method using heat generation powders” for natural gas hydrate (NGH) exploitation. This method was evaluated based on its ability to accelerate NGH decomposition through efficient heating. The experiment meticulously examined the impact of heat generation powders thermal stimulation (HPTS) on gas extraction from hydrate-bearing sediments (HBSs) at temperatures of 14 and 8 °C. Key parameters, such as gas production, temperature variations, energy efficiency, and thermal efficiency, were closely monitored throughout the NGH exploitation process. The study documented the cementation of HBS, where hydration products bonded loose sand grains after hydrate decomposition. Additionally, it provided a comprehensive overview of the five major mechanisms of heat generation powders: in situ heat supply, high expansion force, cementation, porosity enhancement, and increased pore volume. Gas production was feasible at both 14 and 8 °C, with the in situ hydration reaction at 14 °C demonstrating greater intensity, leading to higher average gas production rates, rapid cementation of loose sand grains, and reduced hydration and exploitation durations. HPTS effectively mitigated temperature disturbances, fostering a safer and more stable environment for NGH exploitation. Notably, the energy efficiency (η) and thermal efficiency (ξ) of HPTS surpassed those of traditional thermal stimulation methods at both HBS temperatures. At 8 °C, HPTS exhibited superior η and ξ, reaching values of 13.255 and 0.8109, respectively, thus offering substantial advantages over conventional methods. Post-experiment observations revealed that hydration products facilitated the cementation of all loose sand particles in Reservoir 1 and a portion in Reservoir 2, forming visually striking cemented cores. The findings underscored HPTS’s ability to deliver favorable gas production, improved heat transfer, and exceptional HBS cementation. With three hydration heat regulation methods, the hydration heat for heating the reservoir skeleton is expected to be further reduced, increasing the proportion of hydration heat consumed in hydrate decomposition, thereby enhancing heat utilization efficiency and achieving higher η. In conclusion, the HPTS method demonstrates significant promise at HBS temperatures of 14 and 8 °C, with the potential to drive sustainable development and foster environmentally friendly production practices.