Print this pageThe Yinggehai basin lies in the northwestern shelf of the South China Sea. The maximum depth of the cenozoic sediments is 17km. Present gas exploration is mainly in the Neogene strata. But it's estimated that the Paleogene sediments (about 8km in depth) has productive potential. So research on the Paleogene rifting structure would greatly enlarge the exploration area.
According to disconformity, subsidence and sedimentation, the evolution of the basin can be divided into three stages: 1. late Paleocene to early Oligocene, rifting stage; 2. late Oligocene to early Miocene, rifting-subsiding stage; 3. late Miocene to Quaternary, subsiding stage. Based on the seismic analysis, the rifting structure was mainly controlled by northwest and northsouth trending faults. This makes Yinggehai basin a northwest trending rhombus. The depocenter formed during the rifting stage mainly lies in the northwest, it reversed during stage 2 and moved to the center of the basin. From Paleocene to Middle Miocene the basin is controlled by the sinistral strike-slip of the Red River Fault, whose later dextral movement caused a quick subsidence and large scale activities of mud-hot fluid diapirs in the basin.
Sand-silicone in 3D scale box is our analogue model for Yinggehai basin. Comparing modeling with the basin by frequency of the fault orientation distribution, the position of depocenter and the geometric similarity during rifting stage, we conclude that the basin was pulled apart obliquely along a zshape velocity discontinuity along and inside the basin, which tallies with the Bouguer anomaly.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid