SHALLOW MIGRATION AND ACCUMULATION SYSTEMS IN THE DEEP WATER AREAS OF THE QIONGDONGNAN BASIN AND THEIR CONTROL ON NATURAL GAS HYDRATE ACCUMULATION

Continuous 3D seismic survey has been carried out in the Qiongdongnan Basin, and various types of migration channels are discovered. Based on the characteristics of shallow migration and accumulation system in the deep-water areas of the basin, this paper is devoted to the mechanisms which controls the deposition and accumulation of natural gas hydrate (NGH). Favorable target areas for NGH exploration are predicted upon the basis. It is revealed that the shallow fluid migration channels of the Qiongdongnan Basin mainly consist of faults, gas chimneys, fractures, erosion unconformities and large reservoirs along the border of the basin. Various types of migration channels are always combined in space to form shallow migration and accumulation systems. The development status of the shallow fluid migration channels system varies from place to place. The most developed areas include the Lingnan - Songnan Low Uplift and the Central Depression of the basin, while in the shallow water areas, the systems are relatively undeveloped. The shallow fluid migration and accumulation systems in the deep-water areas of the Qiongdongnan Basin not only control the distribution of NGH, but also influence the gas exploration of the middle and deep layer deposits. To sum up, the shallow fluid migration channels are relatively developed in the Qiongdongnan Basin, and the Lingnan-Songnan Low Uplift is the most favorable zone within the basin, and the continental slope areas of the Songnan-Baodao Sag also have excellent conditions for NGH accumulation.