Petroleum Geology Of Superimposed Petroliferous Pre-Caspian Basin And Hydrocarbon Accumulation Mechanism In Pre-salt Petroleum System Of The East Pre-Caspian Basin

China National Oil and Gas Exploration & Development Corporation (CNODC) holds the equity of Kenziyak and Zhanarol oil-field, which has recoverable reserves of 120 million tons with annual production of 7 million tons. In addition, there is an exploration block with acreage of 3262.3km2. These oil-fields and exploration block will provide 10 million tons of crude oil to the Kazakhstan-China oil pipeline, which has connection with Kenziyak oilfield when the pipeline is finished.Four tectonic evolution stages are stated after the tectonic features of Pre-Caspian basin have been analyzed. And the Pre-Caspian basin is considered as a rift-sag superimposed one.This research focuses on the geological features of eastern Pre-Caspian basin, which will help to facilitate the exploration process of the middle block.Analysis of core and oil samples, as well as geological study, shows hydrocarbons in pre-salt and post-salt reservoirs share the same source origin of Lower Carboniferous carbonate. All of above certifies the petroleum system of eastern Pre-Caspian basin. Three fairways are classified in the eastern Pre-Caspian basin, with the middle fairway being the exploration focus.At present, pre-salt hydrocarbon is the main exploration target. Due to the existence of salt formation in the Lower Permian, some problems appeared in the processing of seismic data. Some advanced seismic techniques are used to solve the salt-related problem to certify pre-salt structure.Seismic, well-logging and geological data are used to study the sedimentary facies in Pre-Caspian basin. Sedimentary model of eastern Pre-Caspian basin is established, which deny the reef model set by geologists of the former Soviet Union. Techniques such as seismic facies are used to forecast reservoir distribution, which proved the existence of excellent carbonate reservoir in the middle block. The results do not agree with the opinions of geologists of the former Soviet Union, who favor low porosity and low permeability in the carbonate reservoir of middle block.With the above research results, the characteristics of petroleum system in the eastern Pre-Caspian basin are clear. Some exploration techniques are developed for areas with thick salt, which promoted the exploration of the middle block in the Pre-Caspian basin as a result of discovery of Wumzhal oilfield. The discovery of Wumzhal oilfield shows the competitive edge of China National Oil Corporation in oil industry;Most importantly, it enriches the ideas for exploration of salt-related and carbonate basins, and brings a good example for the exploration of similar basins.