Seismic Forward Modeling And Wide-angle Reflection Research In The Area Of High Velocity Shielding Layers Of The South Yellow Sea

As the land resources will be exhausted, in the21st century, gradually theoffshore oil and gas exploration become more important. China’s Bohai sea, theYellow Sea, the East China Sea and the continental shelf of the northern South ChinaSea area are important source of China’s offshore oil and gas. The offshore oil and gasresources are abundant. As the ocean exploration is started late in China and thetechnology is not advanced, the level of exploration is very low，so improving thelevel of ocean exploration technology and expanding offshore exploration scale areparticularly important.The South Yellow Sea is a primary area which stores offshore oil and gas in ourcountry. It has a considerable exploration prospect. But due to the complexity ofgeological structure of the South Yellow Sea, the data acquisition and post-processingwork of the region become more difficult. There is a thick layer of high velocity in thecentral rise and WuNanSha rise of the South Yellow Sea basin area. The existence ofthe high velocity layer makes the shallow multiples more abundant, at the same time，it seriously affects the access of effective information in the substratum. It makes theexploration of deep target strata in the research work very difficult.In order to reduce the impact of high velocity layer, and to get more effectiveinformation of the deep area, firstly the propagation rules and characteristics of theseismic wave in the region of high velocity layer should be understood. Acquisition ofactual seismic data can help us to know the underground structure characteristics ofthe target area and the seismic wave propagation mechanism, but it also has somelimitations. Using of the seismic wave field forward modeling can help to more fullyand accurately analyze of wave field characteristics. It can provide theory support forthe practical seismic data acquisition and reduce the cost by adjusting the geometry parameters for designing reasonable acquisition scheme.Wave field simulation technique is applied to the high layer shielding problem inSouth Yellow Sea. Based on previous research data to establish the geological modelof the South Yellow Sea basin, and calculated the seismic response of the model, theforward modeling results were analyzed, and the analysis of seismic wavepropagation characteristics contains the region of high velocity layer. By comparingthe wave field characteristic of the region of high velocity layer with that of no highvelocity layer, the shallow high velocity layer’s effect of the South Yellow Sea to theaccess of the effective information from the deep strata is analyzed.When the incident angle of the wave is larger than the critical angle，a specialkind of reflected wave will be received，it is called the wide angle reflection wave. Inview of the influence of the high velocity layer, we adjust the system parameters ofthe forward modeling observation to increase the receiving array. With this method,the wide angle reflecting information of the deep layers is received.