Abstract:

Taking the Shan1 and He8 segments in Sulige gas field as an example, this study focused on the micro pore structures of low permeability reservoir. Based on the study of mercury injection test, scanning electron microscope, and casting slice of core wells, micro pore structure was classified into four types through analysis of reservoir pore types and structures. Characteristics of each micropore structure was analyzed in detail. Dual influence of sedimentary environment and diagenesis resulted in the complexity of the micro pore structures. It is indicated that the genetic mechanism of the low permeability in Sulige gas field is the strong compaction, filling and cementation of autogenetic minerals during diagenesis. Reservoir space was dominated by secondary pores, and the pore throat assemblage was mainly low poresmall throat. With the cluster and Bayes discriminant analyses, combined with seven macro and micro heterogeneity parameters, discriminant function of four pore structure types was established, pore structure types for Sulige gas field were recognized, and the universal evaluation maps of main mini layers were drawn. Further analysis indicates that type Ⅰ and type Ⅱ reservoirs are of highquality, and considered as the further targets for exploration and development of low permeability Shan1 and He8 segments.

Key words: low permeability, pore structure, discriminant analysis, reservoir evaluation