Computation on free gas seepage and associated seabed pockmark formation
Seabed pockmarks formed by seepage of subsurface fluids are very commonly located in areas where gas is present in near-surface sediments. Especially, they are widely observed on the seafloor at hydrate regions around the world. In this paper we consider that capillary sealing is the crucial mechanism for gas entrapment, gas escape, and pockmark formation. In the hydrate system, free gas is trapped beneath the hydrate layer. The gas overpressure increases as the gas accumulates beneath the hydrate, the hydrate layer is a capillary seal. Capillary seals have the property that they fail completely when the gas pressure reaches the point that they are invaded by gas. The release of gas is thus episodic and sudden. We imagine in our model that when it occurs the venting gas will push the overlying water upward at increasingly higher velocities as the gas pipe approaches the seafloor. As the water velocity increases, the near surface sediments will become quick at a depth that is a function of the thickness of free gas column under the hydrate seal and the depth of hydrate seal, leaving a pockmark on the seafloor. The model shows that at least a 22-m-thick free gas layer beneath the hydrate at Blake Ridge is needed to form the 4-m-deep pockmark at the seabed.
Hydrate Capillary Seal Gas Seepage Pockmarks
Z.Su Lawrence M.CATHLES D.F.CHEN N.Y.Wu
CAS Key Laboratory of Renewable Energy and Gas Hydrate, China Department of Earth & Atmospheric Sciences, Cornell University, USA Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, China
国际会议
西安
英文
1030-1035
2009-07-11（万方平台首次上网日期，不代表论文的发表时间）