Diagenesis and diagenetic facies distribution prediction of Chang 8 tight oil reservoir in Maling area, Ordos Basin, NW China

In this study, characteristics of Chang 8 tight sandstone pore structure and diagenesis are analyzed. A classification standard for sandstone diagenetic facies is established. Combined with the probabilistic neural network method, logging curves are used to predict the distribution of diagenetic facies. The following results are found: the Chang 8 reservoir has low porosity-low permeability characteristics, and the pore-throat structures have strong microscopic heterogeneity; both compaction and siliceous and carbonate cementation promote reservoir densification; chlorite cement lining, hydrocarbon emplacement, and the dissolution of feldspar and rock fragments have constructive effects on reservoir development; and two favorable diagenetic facies, a weakly compacted and chlorite-authigenic quartz cementation facies and an intensely compacted-dissolution facies, are developed in the middle of the thick sandstone and are a good match in their horizontal distribution with distributary channel sands. The Chang 81 member has a much larger area that is more favorable for the development of reservoir diagenetic facies than the Chang 82