Abstract:

The high resolution sequence stratigraphy of salt lake in the third member of Qianjiang Formation in Zhongshi Oilfield is studied. Based on the characteristics of scoured surface, flooding surface and the rock salt boundary surface, and the facies association, three short-term base level cycles are identified, including deepening upward asymmetry base level cycle, shallowing-upward asymmetry base level cycle, and symmetry base level cycle. According to the stacked pattern, the third member of Qianjiang Formation is divided into five middle-term base level cycles and one long-term base level cycle. The distribution of sand bodies is controlled by the ratio of accommodation to supply (A/S) . When A/S is very smaller than 1, the sand bodies are best developed, with best formation communication, and under the condition that the weather is hot and the lake evaporation is greater than the supply, the salt is deposited. When A/S is close to 1, the sand bodies are relatively developed. When A/S is very greater than 1, the sand bodies are undeveloped.

Key words: seismite, sedimentary characteristics, seismic sequences, geological significance