The Characteristics Of Hydrocarbon Accumulation And The Favorable Exploration Zone In Eastern Kuqa Depression

Kuqa depression which is rich in oil and gas resources with good petroleum accumulation condition is one of the important gas sources of Tarim Basin. We have studied the geochemical characteristics of the hydrocarbon source rocks, natural gas and crude oil and the oil-gas and source correlation in the east of Kuqa depression by the method of geochemical, deposition and so on. In this paper, we also have analyzed the hydrocarbon accumulation, pool-forming period, the characteristics of migration and accumulation and predicting the favorable exploration zone in the east of Kuqa depression.The Jurassic and Triassic hydrocarbon source rocks which have similar genetic types are two sets of main hydrocarbon source rocks in eastern Kuqa depression. It is difficult to distinguish these two sets of hydrocarbon source rocks by conventional analysis method and geochemical indicators. We have studied the source rocks, eastern Kuqa depression by the biomarker compounds. Result shows that the Jurassic and Triassic hydrocarbon source rocks are the typical continental hydrocarbon source rocks and formed in freshwater, brackish water weak oxidation depositional environment. These two sets of hydrocarbon source rocks existed small difference and it is hard to distinguish.Thanks to the problem that the two sets of hydrocarbon source rocks of Jurassic and Triassic in east Kuqa depression are hard to identify, we have come up with a good idea to distinguish these two sets of similar source rocks by the method of hydrocarbon source rock thermal simulation. By the study of the hydrocarbon source rock thermal simulation light hydrocarbons, we have found that the relative contents of branched alkanes and aromatic hydrocarbons of the hydrocarbon source rock thermal simulation light hydrocarbons have a certain differences. So, we have established the relationship chart of the branched alkanes and aromatic hydrocarbons and have identified the hydrocarbon source rocks, eastern Kuqa depression.Using the geochemical indicators such as light hydrocarbon, isotope and so on, we have studied the oil-gas and source correlation in the east of Kuqa depression. Researches reveal that the gas in eastern Kuqa depression is mainly high mature coal-type gas, and mixed with a small amount of oil-type gas. The gas in Dibei and Dina area is mainly from the Triassic hydrocarbon source rocks, and the oil in eastern Kuqa depression is mainly from the Jurassic hydrocarbon source rocks. The oil source rocks is mainly humic type hydrocarbon source rocks, mainly terrestrial biological organic matter input and the hydrocarbon generation paleoenvironment is partial oxidation environment.The gas reservoir of eastern Kuqa depression have two phases accumulation, early is given priority to with liquid hydrocarbon filling, late is given priority to with gaseous hydrocarbon filling. The reservoir compact before the gaseous hydrocarbon filling time. The petroleum accumulation happened sooner than the reservoir compact, showing the characteristics of dense gas reservoir. The Dibei slope and Tugeerming tectonic belts both are large structural slope belts. The source and reservoir distribute in large area, the source is sufficient and the reservoir is compact. The two structural slope belts are the favorable exploration zones with the advantage of tight sandstone gas reservoir development.This study for the oil and gas exploration of Jurassic in eastern Kuqa depression is of important theoretical significance and application value, which will deepen the understanding of oil and gas enrichment regularity and guide the further exploration in the region of eastern Kuqa depression.