【摘要】 除合适的温度和压力条件外,甲烷水合物的形成还需要有充足的甲烷供给,沉积物孔隙水中的甲烷浓度必须大于甲烷水合物的溶解度.本文建立了水合物-水-游离气三相体系、水合物-水二相体系、气-水二相体系的甲烷溶解度计算优选方法,计算确定了水合物系统的甲烷溶解度-深度相图,依此划分出游离气、溶解气、水-水合物、水-水合物-游离气四个甲烷不同相态分布区.对水合物脊ODP1249和1250钻位、布莱克海台ODP997钻位稳定带甲烷水合物含量和稳定带之下游离气含量进行了计算.ODP1249浅部13.5~72.4 mbsf(mbsf表示海底以下深度)的甲烷水合物是沉积物孔隙体积的10%~61%,ODP1250钻位35~106.5 mbsf的甲烷水合物约为孔隙体积的0.7%~1.9%,水合物层之下游离气层厚约22 m,游离气含量约占孔隙的4%.布莱克海台ODP997钻位的浅部146.9 mbsf处无水合物发育,202.4~433.3 mbsf之间水合物占孔隙体积的约5%~7%,水合物层之下游离气层厚约80 m,游离甲烷含量为孔隙的0.2%~28%.更多还原

【Abstract】 Besides appropriate temperature and pressure,sufficient gas supply is necessary for gas hydrate crystallization within gas hydrate stable zone(GHSZ) of marine environment.In this article we construct the calculation of methane solubilities in the equilibrium system of hydrate-water-free gas,hydrate-water,and water-free gas.The phase diagram of methane solubility versus depth is figured out,by which four phase fields of methane occurrence,namely free gas field,dissolved gas field,hydrate-water field and hydrate-water-free gas field.The contents of hydrate and free gas at sites 1249,1250,997 are computed.At site 1249 and 1250,hydrate content is 10%～61%(13.5～72.4 mbsf) and 0.7%～1.9%(35～106.5 mbsf) in sediment pores,respectively.The layer of free gas immediately below the base of GHSZ at these two sites is about 22 m thick,and its free gas content is about 4% in sediment pores.At site 997,there is no hydrate in the sediment above 146.9 mbsf,hydrate occurs from 202.4 to 433.3 mbsf occupying about 5%～7% of porosity.The free gas layer is about 80 m thick below the hydrate layer,and concentration of methane free gas is about 0.2%～28% in the pore.更多还原