关键词: 深层—超深层, 碎屑岩优质储层, 储集空间, 成储机制, 保存极限

Abstract: The deep and ultra-deep reservoirs of petroliferous basin are one of the three new fields for global oil and gas exploration. In the context of low permeability and densification on the whole, the high-quality reservoirs with relatively high porosity/permeability are the sweet spots for deep-ultra-deep exploration. Exploration practices and researches show that high-quality reservoirs dominated by primary porosity, secondary porosity and pore-fracture assemblage and fractures can also be developed in the deep-ultra-deep clastic rocks of petroliferous basin (at the depth of 4-8 km); in the deep-ultra-deep high-quality clastic reservoirs, Paleozoic reservoirs are dominated by secondary pores, supplemented by primary pores; Mesozoic Jurassic-Cretaceous reservoirs are dominated by primary pores, supplemented by secondary pores; Cenozoic reservoirs are dominated by the massive development of primary and secondary pores. Moreover, the exploration depth in the Mesozoic reservoir is generally greater than that in the Paleozoic and Cenozoic reservoirs. The development of secondary pores in deep-ultra-deep reservoirs is controlled by shallow-deep polygenetic dissolution pores, the development of cracks is controlled by tectonism, and the effective preservation of pores and fractures in the deep-ultra-deep layers under different geological background condtions is controlled by early cementation (chlorite cladding and carbonate cement crust), shallow fluid overpressure, early hydrocarbon charging and burial-thermal evolution history with low time-temperature index. The development of high-quality oil and gas reservoirs in deep-ultra-deep reservoirs attributes to the inter-coupling of different geological factors, including favorable sedimentation, burial-thermal evolution history, fluid pressure history, diagenetic evolution history-pore evolution history and oil-gas charging history, and are classified into 5 typical types as follows:(1) mainly controlled by fluid overpressure and oil-gas charging in shallow-medium layers, dominated by primary pores; (2) mainly controlled by chlorite cladding in shallow layers and oil-gas charging in medium-shallow/deep layers, dominated by primary pores; (3) mainly under the control of overpressure formed by early long-term shallow burial and late rapid deep burial as well as oil-gas charging in medium-deep layers, dominated by primary pores; (4) mainly controlled by surface leaching poers and oil-gas charging in medium-shallow layers, dominated by secondary pores; (5) mainly controlled by polygenetic dissolution and late hydrocarbon charging, dominated by secondary pores. In the absence of connection between large-scale fracture systems, the porosity increased by burial dissolution is limited, and various types of "shallow accumulation-deep preservation" are the key to the development of deep-ultra-deep high-quality oil-gas reservoirs. In addition, the preservation limit of clastic oil-gas reservoir porosity determines the lower limit for the oil-gas exploration in deep-ultra-deep layers; organic-inorganic interaction of "hydrocarbon-water-rock" in deep-ultra-deep oil-gas reservoirs continues to affect reservoir quality and oil-gas quality evolution; the organic-inorganic interaction mechanism under high temperature and high pressure and the depth limit for the preservation of reservoir pores constrained by it are the focus of further study.

Key words: deep-ultra-deep layer, high-quality clastic reservoir, reservoir space, reservoiring mechanism, preservation limit