摘要
针对南海神狐海区含天然气水合物的高孔隙度、以粉砂质黏土为主的未固结的深水沉积地层,采用Lee提出的改进的Biot-Gassmann(BGTL)模型,利用纵波速度数据估算了A井天然气水合物的饱和度。BGTL模型假设非固结沉积地层的横波速度与纵波速度比与地层骨架的横波速度与纵波速度比与地层孔隙度有关。模型中参数的选择与天然气水合物在沉积物中的赋存方式、沉积物的矿物组成、地层压差、孔隙度及微观孔隙结构等参数密切相关。A井中天然气水合物在沉积物中赋存模式接近于颗粒骨架支撑模式。根据岩心分析资料将A井的矿物骨架简化为黏土矿物、碳酸盐、陆源碎屑3类,根据各矿物组分的理论弹性参数和体积百分比可以计算得到地层骨架的弹性模量和密度。应用BGTL理论估算得到的A井天然气水合物主要赋存于海底以下195～220mbsf井段,饱和度多数为20%～40%,最大饱和度为47%左右,与实测结果吻合。
The modified Biot-Gassmann theory （BGTL） proposed by Lee （2002） is applied in this study to estimation of the saturation of gas hydroate in the deep-water unconsolidated clayey sediments from the Well A, Shenhu area, northern South China Sea. The BGTL theory assumes that the ratio of the shear to compressional velocities of an unconsolidated sediment is related to the ratio of the shear to compressional velocities of the solid matrix in the sediment and its porosity. Parameters involved in the model are related to the occurrence of gas hydrate, mineral components, pressure differentiation, porosity, and pore structure of the sediments. The cross plot of velocity from sonic logging vs. concentration of gas hydrate from core measurements suggest that the occurrence of gas hydrate in the sediments of Well A is more or less close to the matrix model. Statistics from core smear slide data suggest that the sediment matrix in well A can be simplified as three major mineral components, i. e clay, carbonate, and terrigenous clastic minerals. The e- lastic modulus and density values of the matrix are calculated by the elastic modulus and density values of the individual mineral components and their volume percentage. As estimated, the gas hydrate in Well A is mainly distributed in the depth interval of 195 to 220 meters below sea floor with a highest concentration of gas hydrate up to 47%, which matches well with the results from core measurements.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2012年第4期83-89,共7页
Marine Geology & Quaternary Geology
基金
国家自然科学基金项目(91028003
40476030)
南海天然气水合物成矿理论及分布预测研究项目(GZH2011003-05)
