Simulation of gas hydrate dissociation caused by repeated tectonic uplift events

Abstract

Gas hydrate dissociation by tectonic uplift is often used to explain geologic and geophysical phenomena, such as hydrate accumulation probably caused by hydrate recycling and the occurrence of double bottom‐simulating reflectors in tectonically active areas. However, little is known of gas hydrate dissociation resulting from tectonic uplift. This study investigates gas hydrate dissociation in marine sediments caused by repeated tectonic uplift events using a numerical model incorporating the latent heat of gas hydrate dissociation. The simulations showed that tectonic uplift causes upward movement of some depth interval of hydrate‐bearing sediment immediately above the base of gas hydrate stability (BGHS) to the gas hydrate instability zone because the sediment initially maintains its temperature: in that interval, gas hydrate dissociates while absorbing heat; consequently, the temperature of the interval decreases to that of the hydrate stability boundary at that depth. Until the next uplift event, endothermic gas hydrate dissociation proceeds at the BGHS using heat mainly supplied from the sediment around the BGHS, lowering the temperature of that sediment. The cumulative effects of these two endothermic gas hydrate dissociations caused by repeated uplift events lower the sediment temperature around the BGHS, suggesting that in a marine area in which sediment with a highly concentrated hydrate‐bearing layer just above the BGHS has been frequently uplifted, the endothermic gas hydrate dissociation produces a gradual decrease in thermal gradient from the seafloor to the BGHS. Sensitivity analysis for model parameters showed that water depth, amount of uplift, gas hydrate saturation, and basal heat flow strongly influence the gas hydrate dissociation rate and sediment temperature around the BGHS.

Magnetic Mineralogical Approach for the Exploration of Gas Hydrates in the Bay of Bengal

“…Geodynamics, tectonism, global climatic change, sea level fluctuations, and variable sedimentation rate can affect the development of gas hydrate systems in marine sedimentary environments (García‐Tortosa et al, ; Herbozo et al, ; Milkov & Sassen, ; Moore et al, ; Paull et al, ). For example, neotectonic activity can potentially alter the base of the gas hydrate stability zone, leading to the gas hydrate dissociation and intensified methane expulsion/seepage events (Dewangan et al, ; Goto et al, ; Jahren et al, ; Riedel et al, ; von Huene & Pecher, ). Rapid sediment loading triggered by abrupt climatic changes and supply from major river systems can generate overpressured sedimentary strata, thereby creating an efficient fluid migration system and sedimentary reservoir for methane trapping and gas hydrate formation (Hustoft et al, ; Karstens et al, ; Torres et al, ; Wang et al, ; Yu et al, ).…”

A Fluid Pulse on the Hikurangi Subduction Margin: Evidence From a Heat Flux Transect Across the Upper Limit of Gas Hydrate Stability

“…This process has long been thought to affect seafloor stability and to play a role in climate change (e.g., Kvenvolden, 1993). A number of studies have focused on gas hydrate dissociation following ocean warming and sea level lowering (e.g., Davy et al, 2010;Goto et al, 2016;Phrampus & Hornbach, 2012) as well as the effects of subsurface fluid flow (e.g., Crutchley et al, 2014;Tréhu et al, 2003).…”

Simulation Study on the Effect of Fracturing Technology on the Production Efficiency of Natural Gas Hydrate

“…Oceanic NGH mining may exacerbate global greenhouse effects and worsen the marine ecological environment, resulting in a series of environmental effects, and also probably lead to submarine landslides, seabed collapse, and other geological disasters [39,40]. There is a certain Increasing the permeability of the hydrate layer can improve heat and mass transfer efficiency, increase the gas migration channels in the hydrate layer, accelerate the hydrate dissociation and discharge, and increase the gas production rate and the cumulative production of CH 4 [4,13,28,30,36].…”

“…The fracturing effect is not easy to control, sometimes resulting in a failure in fracturing. In addition, there is a certain risk that fracturing can cause formation instability [39,40].…”

“…Oceanic NGH mining may exacerbate global greenhouse effects and worsen the marine ecological environment, resulting in a series of environmental effects, and also probably lead to submarine landslides, seabed collapse, and other geological disasters [39,40]. There is a certain amount of risk in the application of fracturing technology to oceanic NGH mining, as it will further reduce the stability of submarine formations.…”