Abstract:

The main rock types of Yingcheng Formation in Lishu Fault Depression of Songliao Basin are arkose and lithic arkose. The result of reservoir physical property test showed that reservoir physical properties are poor in this area, which have characteristics of low to ultra-low porosity and special low to super-low permeability. This paper analyzed the low-permeability reservoir's characteristics and its property controlling factors by utilization of core observation, thin section identification, image analysis, mercury testing and other technical methods. The main reservoir pore spaces are primary, secondary dissolution pores and a small amount of mixed pores. The diagenetic types of the reservoir are compaction, dissolution, cementation, metasomatism, and so on, and the diagenetic evolution sequence is compaction→feldspar and debris dissolution→carbonate cementation→carbonate dissolution. Thus the sedimentation and diagenesis coupling relationship determines the quality of reservoir properties. On the basis of the above, the inversion method of back stripping was used to recover the reservoir properties and its evolution history during the geological time under the constraint of reservoir diagenesis evolution sequence and reservoir pore structure. The results show that the low-permeability reservoir's physical properties are fundamentally controlled by deposition, moreover, the low-permeability characteristics are predominated by compaction and enhanced by cementation.

Key words: Lishu Fault Depression, Yingcheng Formation, low-permeability reservoir, genetic mechanism, inversion method of back stripping