The Lower Jurassic reservoir has recently made a significant breakthrough in petroleum exploration in the Tugerming area of the eastern Kuqa depression, Tarim Basin, northwest China. Therefore, it is significantly essential to simulate the hydrocarbon charging process and analyze the accumulation mechanism in the study area. In our study, we mainly combine three geochemical techniques to identify the origin of crude oils and fluid inclusion characteristics in the target well (Tudong 2), including gas chromatography–mass spectrometry (GC–MS), comprehensive two-dimensional GC-time-of-flight MS (GC × GC–TOFMS), fluid inclusion analysis, and quantitative fluorescence technique. Combined comprehensive experiments with a set of burial history and tectonic thermal evolution history realize the reconstruction of the hydrocarbon charging process in the Yangxia formation. The results show that Jurassic coal-bearing source rocks are primary hydrocarbon sources, and there are three hydrocarbon charging events in the Lower Jurassic reservoir. First, the mature oils have expelled into the reservoir during the early-middle period (15–10 Ma) of the Miocene Kangcun Formation, forming yellow fluorescent oil inclusions and most of the quantitative grain fluorescence (QGF) indexes exceed 4. Second, numerous condensate oils have charged into the reservoir in the period of late Miocene Kangcun Formation-early Kuqa Formation (9–6 Ma), accompanied by blue-white oil inclusions and QGF on extract intensity greater than 4. Finally, vast natural gas has accumulated in the reservoir since Kuqa Formation (5–0 Ma), resulting in the adjustment of ancient reservoir and residual bitumen. Interestingly, we find that the hydrocarbon accumulation mechanism is characterized by self-generation and self-storage in the Jurassic Yangxia Formation, and the study area has prominent characteristics of late accumulation. Thus, the evidence obtained from our analysis suggests favorable geological conditions for the formation of a large oil and gas reservoir in the eastern Kuqa Depression.

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There has been significant progress in hydrocarbon exploration of the eastern Kuqa Depression, Tarim Basin, whose Jurassic reservoir is a key area for abundant hydrocarbon with poorly understood accumulation mechanism. This study conducts an integrated investigation comprising petrographic observations, microthermometry measurements, and fluorescence spectroscopy analyses on fluid inclusions to reconstruct hydrocarbon accumulation history in the Jurassic reservoir. These conclusions are combined with biomarker characteristics to reveal the burial history and thermal evolution of the study area. The results show that (1) there were two episodes of oil charging that occurred at 6~4 Ma and 4~2 Ma, respectively. The QGF experiment response and yellow fluorescent oil inclusions indicated that low-maturity medium crude oil from the Triassic source rocks was expelled into the upper Ahe Formation. In the second charging stage, some mature oil generated from Jurassic source rocks was charged into the reservoir of the Kezilenuer and Yangxia formations, while the condensate from the Triassic source rocks was migrated upward to the Jurassic reservoir, consistent with smaller QGF-E intensity values and blue-white fluorescent petroleum inclusions. (2) There were two kinds of hydrocarbon accumulation models including the lower-generation and upper-storage and the self-generated and self-stored models. (3) It was noted that active faults were developed under the compression stress to provide channels for hydrocarbon vertical migration. Moreover, the early reservoir was destroyed resulting from the strata denudation and a large amount of crude oil was escaped to the surface. The findings of this study can help for better understanding of hydrocarbon accumulation mechanism in the eastern Kuqa Depression and provide theoretical guidance for further oil and gas exploration.