科研之友
微信
新浪微博
Facebook
分享链接
摘要
Marine hydrates are globally distributed in deep-sea sediments, such as the Makran accretionary prism, where high operational costs and drilling hazards cause a lack of well data. Although the seismic analyses are efficient methods for detection and delineation of hydrate resources for such unexplored regions, developing a scheme to quantify them would be the ultimate goal. In this study, a quantifying approach is introduced which is called reflectivity template (RT). This approach theoretically calculates normal incident (NI) and Poisson reflectivity (PR) attributes by the effective medium theory (EMT) and creates their intuitive crossplots across a bottom simulating reflector (BSR). By superimposing the attributes derived from amplitude-variation-with-offset (AVO) on RTs, the saturations of the hydrate and free gas near the BSR could be estimated. This technique acts as a quantitative interpretation tool when well log data is not available. It is only needed to make good assumptions about porosity and mineralogical composition of the host sediments. Reliability of this approach was validated by synthetic data and the results showed the RT should be created in a way that it was independent from the velocity ratio assumption. Applying this approach to a 2D marine pre-stack time migrated (PSTM) seismic line have implied geological control over hydrate and free gas saturations in the Makran accretionary prism. Estimated saturations near the BSR were approximately 4-30% for the gas hydrate and 1-7% for the free gas across the seismic line.
- 出版日期2014-2
