On the thermal impact of gas venting and hydrate crystallization
On the thermal impact of gas venting and hydrate crystallization
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DOI：
10.1029/2004jb003533
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发表时间：
2005-11
影响因子：
--
通讯作者：
Duofu Chen;L. Cathles
中科院分区：
文献类型：
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作者：
Duofu Chen;L. Cathles
[1]在某些海底观测到的气体泄放速率下，热平流和水合物结晶的潜热可以显著地加热地下，减小水合物稳定带厚度，并分解先前结晶的水合物。然而，热平流和水合物结晶的潜热的影响受到发生喷口的持续时间的限制，最终受到水合物堵塞喷口的时间的限制。我们使用具有恒定水合物结晶的稳态热流方程的新的一维解析解来研究气体排放、水合物结晶和地下温度之间的关系，并使用包括空间和时间相关的水合物溶解和结晶的瞬变热流方程的一维有限元解来考察排气持续时间的影响。结果表明，在侧向热损失可以忽略的情况下，水合物结晶和在海底观察到的更猛烈的气体排放速率的气流热平流可以使地表附近的温度梯度增加一个数量级以上，并将水合物稳定带厚度从喷口堵塞水合物之前的∼570降至<；200m。我们计算了当排气口堵塞水合物时，气体和结晶水合物的化学性质是如何演化的。
[1] At the gas venting rates observed in some seafloor localities, heat advection and the latent heat of hydrate crystallization could significantly warm the subsurface, reduce the hydrate stability zone thickness, and decompose previously crystallized hydrate. Effects of heat advection and the latent heat of hydrate crystallization are limited by the duration of time over which venting occurs and ultimately by the time it takes to plug vents with hydrate, however. We examine the connection between gas venting, hydrate crystallization, and subsurface temperature using a new one-dimensional analytical solution to the steady state heat flow equation with constant hydrate crystallization, and we examine the effects of the duration of venting employing one-dimensional finite element solutions to the transient heat flow equation that include space- and time-dependent hydrate dissolution and crystallization. We show that if lateral losses of heat are negligible, hydrate crystallization and the advection of heat by gas flow at the more vigorous rates of gas discharge observed on the seafloor could increase the temperature gradient near the surface by more than an order of magnitude and decrease the feed gas hydrate stability zone thickness from ∼570 to <200 m before the vents plug with hydrate. We compute how the chemistry of the venting gas and crystallizing hydrate evolve as a vent plugs with hydrate.