An Analysis Of The Geological Conditions For Developing Gas Hydrate In Qiongdongnan Basin And A New Method In Identification Technology

The high developing speed of the society in this new century asks for a kind of energy which is not only large in quantity but also clean and high effective. Obviously, the gas hydrate is such a kind of energy. China has found samples of gas hydrate in Shenhu area of the South China Sea in May of 2007, which has proved that there is gas hydrate in the South China Sea. So investigating the advantageous enrichment regions and the characteristics of distribution of gas hydrate in South China Sea should be the next step in our research. As having done lots of work in Qiongdongnan basin, and having getting large quantity of data, in this thesis, we plan to investigate the occurrence state of gas hydrate in this basin.Firstly, we analyzed the tectonic, sedimentological, thermodynamic and gas source conditions for gas hydrate developing; then, by interpreting the four seismic sections located at the south border of Qiongdongnan basin, along with the result of the new gas hydrate identification method’s application in these four sections, which is on basis of elastic parameters of stratums , deduced the occurrence state of gas hydrate in these four sections; finally, from the analytic result of above two points, we tried to tell about the occurrence state of gas hydrate in the whole Qiongdongnan basin.In the research of gas hydrate identification, a problem need to be solved is how to distinguish the geophysical anomaly caused by gas hydrate or other factors. High wave speed anomaly can be also caused by other factors except for gas hydrate, and then strong reflection parallel to the sea floor may develop. Elastic parameters of stratums are playing a more and more important role in gas hydrate identification. In this thesis, the new gas hydrate identification method, which is on the basis of elastic parameters of stratums, is applied in four sections of this research, and by comparing with the traditional geophysical identification sign of gas hydrate-BSR (bottom-simulating reflector), try to discuss about the advantages and disadvantages of these two methods, and to forecast the new method’s prospect. In this thesis, drew the conclusions about subjects above as follow:The Qiongdongnan basin has good conditions for gas hydrate developing in tectonics, sedimentology and gas source, but the thermodynamics condition is relatively poor. Generally speaking, the Qiongdongnan basin has a nice gas hydrate prospect.The process of gas hydrate in the Qiongdongnan basin is belong to the permeating model, and as a result, gas hydrate here is densely distributed, having exploiting prospect; the section of Line 344, which is located at the edge of the basin, has a feature of diffusion model.The nice hydrocarbon source condition of the subsiding center is a key factor for gas hydrate development, and its occurrence has a close relation with the location of the subsiding center. Generally, the closer to the subsiding center, the better gas hydrate prospect it may have.The new gas hydrate identification method on basis of elastic parameters of stratums may be superior to the traditional geophysical identification sign-BSR, however, this new method needs further test.