Abstract:

 The main lithological types are feldspathic lithic sandstone, lithic feldspar sandstone, lithic sandstone and greywacke with low compositional and textural maturities in the Paleogene reservoir in the west sag of the beach area, Liaohe Depression. The sedimentary environment is nearsource and multisource depositional system. The pore types are primary pores, secondary pores and compound pores. The physical properties alter regularly with the burial depth and the abnormal high values of porosity and permeability at the depth scale of 1,400 to 2,600 meters and 2,800 to 3,400 meters. The research infers that the diagenetic stage of this reservoir is from B substage of early diagenesis to A substage of late diagenesis and the primary types contain mechanic compaction, cementation, dissolution and metasomatism. In detail, the metasomatism is constructive with prevalence and strong degree, and the other three are detrimental with medium degree. The main controlling factors are the intensity and stages of diagenesis. These two abnormal porosity zones are attributable to the composite effects of various diagenesis activities. The first zone is related to the organic maturity in the acid diagenetic environment and the second one in the alkaline environment, in which the dissolution of silica components contribute the formation and reservation of secondary pores to a great degree.

Key words:  Paleogene reservoir, diagenesis, reservoir physical property, west sag of the beach, Liaohe Depression