Laboratory Study on Hydrate Production Using a Slow, Multistage Depressurization Strategy

Abstract

Optimization of the depressurization pathways plays a crucial role in avoiding potential geohazards while increasing hydrate production efficiency. In this study, methane hydrate was formed in a flexible plastic vessel and then gas production processes were conducted at constant confining pressure and constant confining temperature. The CMG-STARS simulator was applied to match the experimental gas production behavior and to derive the hydrate intrinsic dissociation constant. Secondly, fluid production behavior, pressure-temperature ( P ‐ T ) responses, and hydrate saturation evolution behaviors under different depressurization pathways were analyzed. The results show that integrated gas-water ratio (IGWR) decreases linearly with the increase in depressurizing magnitude in each step, while it rises logarithmically with the increase in the number of steps. Under the same initial average hydrate saturation and the same total pressure-drop magnitude, a slow and multistage depressurization strategy would help to increase the IGWR and avoid severe temperature drop. The pore pressure rebounds logarithmically once the gas production is suspended, and would decrease to the regular level instantaneously once the shut-in operation is ended. We speculate that the shut-in operation could barely affect the IGWR and formation P ‐ T response in the long-term level.

The effects of time variable fracture conductivity on gas production of horizontal well fracturing in natural gas hydrate reservoirs

“…The simulator considers the coupling effect of fluid flow, heat transfer, and fines transport in porous media and wellbore. 58…”

“…The CMG‐STARS is primarily developed for thermal recovery. The simulator considers the coupling effect of fluid flow, heat transfer, and fines transport in porous media and wellbore 58 . Many scholars use this software to simulate hydrate.…”

Progress on Laboratory-Scale Reactors for Simulating Gas Production from Hydrate Reservoir

“…This causes the decomposition of hydrate to slow down and reduces the exploitation rate. The main purpose of the laboratory to simulate the decompression of hydrate production is to optimize the rate and range of decompression. , In addition, other methods can be combined to increase the gas production rate and recovery efficiency. − The following mainly describes the development of the reactor used in the laboratory simulation exploitation experiment, the comparison of the gas recovery efficiency, and various parameters of the main reduced pressure exploitation scheme on reactors of different scales.…”

Research on Natural Gas Production Behavior Using Stepwise Depressurization with a Horizontal Well

“…The results showed that stepwise depressurization could obtain a more stable gas production rate but would prolong the decomposition time of hydrate. Li et al 35 studied the gas production behavior of hydrate reservoirs under different depressurization paths by combining experiment and simulation. The results show that the slow stepwise depressurization strategy is helpful to improve the gas−water ratio and avoid the sharp temperature drop in the reservoir.…”