## 4 Conclusions  
(1) The lower depth limit of effective hydrocarbon reservoirs in elastic rocks is influenced by geological understanding and engineering technology, rather than strict geological boundaries. It evolves with exploration progress and varies across different basins, lithology exploration stages, and technical conditions.  
(2) Primary sedimentation determines the mineral composition, grain size, sorting, rounding, and matrix content, shaping the initial pore conditions of clastic rock reservoirs. It also influences diagenesis and pore evolution trends. High-energy sedimentary environments enhance compositional maturity and rigid particle content, providing high-quality reservoirs.  
(3) Protective diagenesis processes preserve reservoir pores by inhibiting cementation. Clay mineral films and liquid hydrocarbon charging prevent pore fluids from contacting particle surfaces. A long-lasting low geothermal field can slow diagenesis while overpressure near the major hydrocarbon sources delays reservoir densification, preserving effective clastic rock reservoirs.  
(4) In deep reservoirs, high-temperature and high-pressure fluids can induce dissolution, while multi-stage tectonic activity creates complex fractures. These processes enhance porosity and permeability in densified reservoirs, improving sweet spot quality and potentially converting non-reservoirs into reservoirs.  
(5) Future exploration should focus on source-rock internal and near-source strata in hydrocarbon-rich depressions. In marine sedimentary systems, the Devonian and Silurian formations near the Manijaer Depression (Tarim Basin) facilitate vertical hydrocarbon migration, forming large reservoirs controlled by NE-trending strike-slip faults. In the Sichuan Basin, proximity between source and reservoir in the Silurian system is key for tight oil and gas breakthroughs. In continental systems, source-reservoir integration or closely adjacent formations in the P-T (Junggar Basin), the T-J (Tarim Basin), T (Sichuan Basin), and C-P (Ordos Basin) offer prime exploration targets, particularly in the ramp zones of hydrocarbon-rich depressions.  
Conceptualization, Y.Q. and Q.W.; methodology, Z.H.; investigation, Q.W., H.W. and H.H.; writing--original draft preparation, X.W.; writing--review and editing, J.W.; visualization, F.Z. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
We sincerely appreciate all anonymous reviewers and the handling editor for their constructive comments and suggestions that significantly improved this manuscript.  
Authors [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] were employed by the company China Petroleum & Chemical Corporation (SINOPEC). Author [PERSON] was employed by the company The Third Oil Production Plant of Daqing Oilfield Limited Company. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.