南海神狐海域天然气水合物声波测井速度与饱和度关系分析

利用南海北部神狐海域A站位的地震和测井资料综合分析神狐海域含天然气水合物沉积层的声波测井速度及水合物饱和度的分布特征和变化规律，并对水合物饱和度的理论计算值和实测值进行对比分析，同时对水合物稳定带的纵波速度特征与饱和度的关系进行了综合研究。结果表明：神狐海域A站位的水合物层厚度约20 m，纵波速度在1 873～2 226m/s之间，水合物饱和度在15.0%～47.3%之间变化，水合物饱和度值相对较高；受海底复杂地质因素的影响，根据岩心孔隙水的氯离子淡化程度实测的水合物饱和度随声波速度的变化并不是单一的正比例关系，而是随声波速度的升高而上下波动，波动幅度在10%～20%之间，总体趋势上随声波速度的升高而升高，并集中分布在理论曲线附近；利用热弹性理论速度模型计算并校正后的水合物饱和度随声波速度的增加而有规律地增加，水合物饱和度的理论计算值与实测数据比较吻合，说明所建立的岩石物理模型正确，模型参数选取合理。根据声波速度计算水合物饱和度这一方法可扩展到整个研究区域，并为研究区的水合物资源量评价提供基础数据。

Relationship between the Sonic Logging Velocity and Saturation of Gas Hydrate in Shenhu Area, Northern Slope of South China Sea

The distributing features and change of sonic logging velocity and gas hydrate saturation in gas hydrate-bearing sediments were summarized with seismic and well logging data,furthermore,a comparative study was conducted between the theoretical calculation and in-situ measurement of gas hydrate saturation in site A,Shenhu area,northern slope of South China Sea.The relationship between sonic velocity and gas hydrate saturation in gas hydrate stability zone has been analyzed,too.The analysis results show that:(1)the thickness,sonic velocity,and gas hydrate saturation of gas hydrate-bearing zone are about 20 m,1,873-2,226 m/s,15.0%-47.3%,respectively;(2)the in-situ measurement of gas hydrate saturation which was derived from the field test of the chloride content in pore water is not direct proportion to sonic velocity for the influence of seafloor geological factors,but fluctuates according to sonic velocity with the range of 10%-20%,and generally increases with increasing sonic velocity;(3)the calculated value of gas hydrate saturation from velocity model of heat elasticity theory regularly rises with increasing velocity.The fit relationship between the theoretical calculation and in-situ value of gas hydrate saturation indicates that the established rock physics model is correct,and the selected parameters of model are reasonable.This method can be extended to the total study area to provide valuable data for resource evaluation of gas hydrate.