Comparison in petroleum geology between Biyang Depression and Nanyang Depression in Nanxiang Basin and its exploration significance

Biyang Depression and Nanyang Depression are secondary structural units of Nanxiang Basin. They are separated by Tanghe low uplift and have similar effective exploration areas. However, the resources, proven geological reserves and oil productions of the two depressions are quite different. Based on the seismic, drilling, logging, geochemical data and current exploration knowledge of the two depressions, we compared their similarities and differences from the prospective of geotectonics, basin analysis and petroleum geology. We have found they share the following points : geotectonic setting, tectonic evolution stages, depression plane modality and stratigraphic systems. However, they are different more remarkably in basement properties, boundary fault characteristics, subsidence characteristics, geothermal characteristics, source rock characteristics, sedimentary system, reservoir physical properties, source-reservoir-seal rock associations, trap conditions, petroleum accumulation mechanisms and preservation patterns. Among these aspects, the overwhelming important factors for controlling the oil and gas distributions are the basement properties and geological framework that control the accumulation factors and effects. The analogy of petroleum geological characteristics shows that the exploration degree in Nanyang Depression is relatively low. Our understanding of the successful exploration experience of Biyang Depression, our geological knowledge, and key exploration technologies, and multi-domain, multi-level, and multi-reservoir type stereoscopic exploration, suggests that the depression still have great exploration potential.