海底水合物地球化学探测方法的试验研究

选择西沙海槽水合物潜在富集区作为已知区 ,利用陆上油气地球化学勘查方法 (酸解烃、热释烃、蚀变碳酸盐方法 )开展了试验性研究。通过对海底浅表层沉积物各项测试指标的分析 ,发现酸解烃方法效果好 ,而热释烃方法和蚀变碳酸盐方法的试验效果并不理想。同时还对海底浅表层沉积物酸解烃重新进行了释义 ,认为酸解烃方法适合于海底水合物的勘查 ,值得进一步推广

EXPERIMENTAL RESEARCH ON GEOCHEMICAL METHODS FOR PROSPECTING GAS HYDRATES IN MARINE SEDIMENTS

In this paper,the Xisha trough of the South China Sea is taken as a known area for gas hydrate to occur because there exist a lot of indicators such as Bottom Simulating Reflectors(BSRs).Some geochemical methods such as acid degassing, heat degassing and ΔC are utilized to conduct the experimental research. Through analyses of the indicative results of the subsurface sediment samples, it is discovered methane gases acid degassed from the sediments are distributed evenly at both the upper and the bottom of the short box core about 40cm except for few sites,and the positions of high values are extremely accordant with those by thermo luminescence method used in another paper by the authors and they are also consistent with BSR indicators. Hence,acid degassing method proved to be effective and suitable for marine hydrate exploration. In contrast,heat degassed gases from the sediments contain lots of olefin besides methane and the methane va lues vary greatly at the upper and bottom of short box core samples, showing heat degassing method isn′t fit for marine hydrate exploration. The ΔC values are very low, changing from 1 72 to 5 00 w ( CO 2 )%,which suggest ΔC method isn't good for this region. Therefore acid degassing method deserves to be recommended for use to explore marine hydrate. Finally, the implication of acid degassing method is re explained: hydrocarbons produced by acid degassing method from the subsurface sediment not only embrace the methane occluded in carbonates, but also include the methane absorbed on the surface of grains.