Experiment and Observation of Methane Hydrate Formation in Silty Clay Sediments of the South China Sea with 50–85% Water Saturation

Abstract

In this paper, the impact of initial water saturation (S iw) and multiple repetitive formations on the formation process of CH4 hydrate in silty clay sediments was examined in a homemade high-pressure visual reactor. The silty clay sediments were from the Shenhu area of the South China Sea. The results showed that the saturation of the CH4 hydrate decreased with the increase of S iw when they were at the same formation time. When the S iw’s were 50% and 60%, the formation process of the CH4 hydrate could be divided into two stages: a rapid formation stage and a slow formation stage. When the S iw was greater than 75%, the formation rate of the hydrate was just in a slow stage. After three repeated formation experiments were performed, we found that the saturation of the CH4 hydrate in the silty clay sediments increased with the time of the repeated experiments. Through camera observation, it was found that the repeated formation and dissociation process produced fractures or cracks in the sediment, which is conducive to reducing the resistance of the gas–liquid transport, providing space for the hydrate formation and storage, and increasing the porosity and hydrate saturation. The CH4 hydrate in the silty clay sediments occurred in the form of a disseminated or thin covering, and the hydrate saturation was from 11.2% to 60.8%, which covered the major hydrate core samplings from the Shenhu area of the South China Sea. The influential factors of forming a high CH4 hydrate saturation are interpreted and discussed in this paper.

Pore-Scale Investigation of CH4 Hydrate Kinetics in Clayey-Silty Sediments by Low-Field NMR

“…Wu et al also found that the rate of MH formation in marine sediments with the low initial water saturation ( S iw ) is greater than that of sediments with higher S iw . The content of water in the pores will directly affect the pore fluid distribution and the gas–liquid contact area.…”

2022 Pioneers in Energy Research: John Ripmeester

“…They observed that CH 4 hydrate in the silty clay sediments occurred in a form of disseminated or thin covering, and the hydrate saturation was from 11.2 to 60.8%, which covered the major hydrate core samplings from the Shenhu area of the South China Sea. 34 Sand production behavior of methane hydrate reservoirs of different particle sizes is very different, and one may reduce the sand production by optimizing the location of the production well. The study by Xu et al 35 reported that the production well should be in the upper layer of the reservoir for larger particle size sediments, whereas for sediments with smaller particles, the production well should be located in the bottom layer of the reservoir.…”

“…A study by Chuvilin et al reported gas hydrate dissociation in frozen sediments exposed to dissolved salts, resulting in destabilization of intrapermafrost gas hydrates and methane emission in the Arctic areas. Wu et al reported the effect of initial water saturation (50–85%) on methane hydrate formation in the presence of silty clay sediments of South China Sea. They observed that CH 4 hydrate in the silty clay sediments occurred in a form of disseminated or thin covering, and the hydrate saturation was from 11.2 to 60.8%, which covered the major hydrate core samplings from the Shenhu area of the South China Sea .…”

“…Wu et al reported the effect of initial water saturation (50–85%) on methane hydrate formation in the presence of silty clay sediments of South China Sea. They observed that CH 4 hydrate in the silty clay sediments occurred in a form of disseminated or thin covering, and the hydrate saturation was from 11.2 to 60.8%, which covered the major hydrate core samplings from the Shenhu area of the South China Sea . Sand production behavior of methane hydrate reservoirs of different particle sizes is very different, and one may reduce the sand production by optimizing the location of the production well.…”

Effect of CO2–Brine–Rock Interactions on the Pore Structure of the Tight Sandstone during CO2 Flooding: A Case Study of Chang 7 Member of the Triassic Yanchang Formation in the Ordos Basin, China

“…studied changes in pore-throat microstructure during CO 2 flooding by rate-controlled porosimetry and fractal method . In addition, numerical modeling methods and visual observation techniques have been recently utilized to investigate the pore structure change in CO 2 flooding, which enhanced the understanding of CO 2 flooding from microscopic and visual perspectives. − These research studies show that the alternation of mineral components may affect the pore throat characteristics, thereby changing the flow behavior during CO 2 flooding. Therefore, determining the pore throat change during CO 2 flooding is an essential prerequisite to understanding the flow characteristics in tight sandstone.…”