南海北部神狐区域SH2站位甲烷水合物成藏动力学模拟研究

ANALYSES ON DYNAMIC METHANE HYDRATE ACCUMULATION SIMULATION IN SHENHU AREA OF THE NORTHERN SOUTH CHINA SEA

南海北部神狐区域海底的高丰度水合物储层与生物成因为主的甲烷气源表明该区域很可能是一种特殊的复合型海洋水合物系统,其成藏动力学机制有待进一步的研究和澄清。建立了一个耦合沉积层地质属性-流体流动过程-水合物反应动力学的传输-反应模型,区别了两种不同类型的水合物形成(分解)动力学过程:(1)在通常情况下溶解甲烷和游离气共同形成水合物,(2)特殊情况下游离气直接生成水合物,结果表明在神狐海域热力学环境下游离气形成水合物速度比溶解甲烷快约4倍,气体含量和动力学常数比值越大生成水合物越快,而对比水合物分布的模拟结果与实测数据表明该区域水合物储层聚集和产状很可能受到了其他地质活动的影响。

The deposit in Shenhu area is a kind of complicated marine hydrate system.Thus the mechanism of its dynamic accumulation still needs to be further studied and clarified.A flow-transport-reaction model,coupled with the kinetic characteristic of hydrate reaction,has been established to evaluate the formation of the hydrate deposits. Two types of the marine hydrate systems,one formed by only dissolved methane and the other formed by both dissolved methane and free gas,have been respectively discussed about how they contribute to the accumulation of the hydrate-bearing sediments.The hydrate saturation at the bottom of hydrate stable zone has been deduced,and the influences of the free gas content and the hydrate kinetic characteristics have also been studied to examine the collection process of hydrate deposits in this area.The results imply that certain kinds of special geologic events have happened to transform the formation and aggregation of the hydrate deposits in this area.