摘要
含水合物储层纵横波速度不仅与天然气水合物饱和度有关,还取决于水合物的赋存形态.本文基于考虑水合物微观形态的岩石物理模型预测了水合物海脊1247B和1250F井位的水合物饱和度,并与核磁共振——密度孔隙度评价的饱和度进行比较,以确定水合物在沉积物中的存在形态.而且对比了有效介质模型、改进的Boit-Gassmann模型和简化的三相方程在同一赋存形态下预测的饱和度,以此探究三种模型在含水合物储层定量评价中的适用性.对比预测结果显示,1247B和1250F井位的天然气水合物主要以骨架支撑形态存在.虽然各岩石物理模型在含水合物层段预测趋势一致,但是,相对于简化三相方程预测结果而言,有效介质模型和改进的BiotGassmann模型能更准确预测出海底沉积物中水合物饱和度,并且在同一种模型中纵横波速度联合反演比单纵波预测的水合物饱和度更合理.
Elevated elastic velocities are a distinct physical property in gas hydrate-bearing sediments. A number of hydrate accumulation models and equations have been frequently used to estimate hydrate saturations.However,the elastic properties of gas hydrate-bearing sediments not only depend on the amount of hydrates,but also on how gas hydrates form and distribute within marine sediments.In order to determine in which from gas hydrate exists in unconsolidated sediments,the saturation estimations considered in different morphologies are then compared with those evaluated from NMR-density porosity logs in well sites 1247B and 1250F.Meanwhile,We make a comparison of the hydrate saturations estimated from effective medium theory, modified BiotGassmann theory and simplified three phrase equation for given hydrate morphology to investigate the applications and limitations of these three models.Based on our estimations,the saturations from the form of matrix-supporting fit the inferred data well,which reveals that the hydrate mainly exists as a part of frame at these two sites.Though the saturation estimations predicted from the three models show nearly identical trends,the estimates from effective medium theory and modified Biot-Gassamnn theory are more accurate than those from simplified three phrase equation.Additionally,the saturations from joint inversion of P-and S-wave velocities are more reliable than those from single P-wave velocity inversion.
出处
《地球物理学进展》
CSCD
北大核心
2014年第4期1735-1740,共6页
Progress in Geophysics
基金
济大学海洋地质国家重点实验室自主课题(MG20120205)资助
