Sedimentary System Evolution and its Response to Tectonic Movement in Changchang-Heshan Depression, Deep Water Area of Pearl River Mouth Basin

Key words: 
• sequence stratigraphic framework /
• sedimentary system /
• transfer zone /
• Changchang-Heshan depression /
• Pearl River Mouth Basin /

Abstract: Changchang-Heshan depression, located in southwest Zhu-IV subbasin of Pearl River Mouth Basin, extends in NE-SW direction. It is an important strategic exploration block after oil and gas exploration breakthrough in Baiyun and Liwan depression in deep water area. Changchang-Heshan depression is a new area to oil and gas exploration and has no wells, so the basic geological research is particularly important. Based on fault interpretation and formation thickness analysis, rift stages and structural characteristics were studied in detail. Wenchang and Enping Formation experienced two successive tectonic stages, which respectively corresponded to intensive rift stage and weak rift stage. A variety of different levels and types of structural transfer zones were identified at the same time. Guided by the theory of classic sequence stratigraphy, Wenchang and Enping Formation were divided into two second-order sequences and seven third-order sequences based on the two-dimensional seismic data. According to the characteristics of the seismic reflection, transfer the classic seismic facies to sedimentary facies within the sequence framework, and then rebuilt the process of sedimentary system evolution in the study area. Classified two levels(Ⅰ and Ⅱ) and six types of structural transfer zones(syntropy non-overlapping, syntropy non-overlapping, syntropy parallel, syntropy collineation, opposite overlapping and back to back overlapping). The degree of the fault activity controlled the sequence evolution and sedimentation system. Furthermore, structural transfer zone and slope break controlled the distribution and scale of sand bodies. The study area is a new region for oil and gas exploration, this method is focused on the close relation between tectonism and sedimentation. Finally, it offers reliable evidence for favourable region exploration and supports a solid scientific evidence for the low degree oil and gas exploration in deep water area.