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The Paleogene system of the Zhuyi Depression exhibits a pronounced mechanical compaction background. Despite this compaction, remarkable secondary porosity is observed in deep clastic rocks due to dissolution processes, with well-developed hydrocarbon reservoirs persisting in deeper strata. We conducted a comprehensive study utilising various analytical techniques to gain insights into the dissolution and transformation mechanisms of deep clastic rock reservoirs in the steep slope zone of the Lufeng Sag. The study encompassed the collection and analysis of the rock thin sections, XRD whole-rock mineralogy, and petrophysical properties from seven wells drilled into the Eocene. Our findings reveal that the nature of the parent rock, tuffaceous content, dominant sedimentary facies, and the thickness of individual sand bodies are crucial factors that influence the development of high-quality reservoirs under intense compaction conditions. Moreover, the sustained modification and efficient expulsion of organic–inorganic acidic fluids play a main role in forming secondary dissolution porosity zones within the En-4 Member of the LF X transition zone. Notably, it has been established that the front edge of the fan delta, the front of the thin layer, and the near margin of the thick layer of the braided river delta represent favorable zones for developing deep sweet-spot reservoirs. Furthermore, we have identified the LF X and LF Y areas as favourable exploration zones and established an Eocene petroleum-accumulation model. These insights will significantly aid in predicting high-quality dissolution reservoirs and facilitate deep oil and gas exploration efforts in the steep slope zone of the Zhuyi Depression. [ABSTRACT FROM AUTHOR]

The Lower Paleozoic carbonate reservoir in the Tarim Basin is a hotspot area for deep oil and gas exploration in China. Although the Lower Cambrian of the Bachu Uplift has not encountered industrial oil flow, rich bitumen has been found there. As the most direct trace of petroleum migration, the effective identification of bitumen is the key to studying the hydrocarbon transportation path. In this study, the Adobe Photoshop quantification (PSQ) method is used to identify the bitumen content in the Xiaoerblak Formation in Well Shutan 1, and, combined with the bitumen characteristics of the Shihuiyao section, a high-quality petroleum transverse transport layer is determined. The results indicate the following: (1) In Well Shutan 1, bitumen is mainly concentrated in the middle and upper parts of the Xiaoerblak Formation with high porosity and high permeability. (2) The shale of the Yuertus Formation in the Shihuiyao section has low hydrocarbon generation potential. However, the overlying Xiaoerblak Formation has developed multistage bituminous veins and bitumen-encapsulated gravels, which is the result of multiple instances of horizontal hydrocarbon migration. (3) After combining the bitumen characteristics of Well Shutan 1 and the Shihuiyao section, it is confirmed that there are high-quality lateral transport conductors in the middle and upper parts of the Xiaoerblak Formation, and the Subsalt Cambrian dolomite reservoir has great exploration potential. [ABSTRACT FROM AUTHOR]