Abstract:

Existing drilling and seismic data reveal that Mesozoic strata are widely developed in the southern South China Sea (SCS)．In order to further understand the distribution characteristics and oil and gas geological significance of the Mesozoic strata in the southern SCS，the latest satellite gravity data are used to invert the depth and thickness of Mesozoic strata in this paper．Firstly，the gravity field forward modeling technique is used to eliminate the influence of the sea water，and the Bouguer gravity anomaly in the southern SCS is obtained． Secondly，in order to eliminate the influence of the Cenozoic sedimentary layer，this layer is divided into three layers： 0-3 km，3-6 km and 6-10 km． According to the relationship between density and depth obtained by predecessors in the SCS，the gravity influence of Cenozoic sedimentary layers is calculated by using the variable density Parker forward modeling method, and it is subtracted from the Bouguer gravity anomaly． The Pre-Cenozoic gravity anomaly was obtained. On this basis，the wavelet multi-scale decomposition technique is used to eliminate the gravity influence of deep Moho and local rock mass，so as to calculate the gravity anomaly derived by Mesozoic strata．Finally，the depth and thickness of Mesozoic strata in the southern SCS are derived by using the 3D Parker variable density interface fast inversion technique． The inversion results correspond well with the known Mesozoic wells． The Mesozoic strata in southern SCS are mainly distributed in Liyue Bank, the north part of Palawan Island and Wan’an area，with the thickness less than 9 km，while in most other areas less than 1 km or no Mesozoic strata．The Mesozoic is the most developed in Liyue Bank area, followed by the northern part of Palawan Island. Combined with the previous research results of oil and gas geological conditions in this area, it is concluded that the Mesozoic of Liyue Bank area in the southern SCS has a good oil and gas exploration prospect.

Key words: southern South China Sea, Liyue Bank, Mesozoic, satellite gravity, density interface