Diagenesis Research Of Low Permeability-tight Sandstone Of 62-66 Block In Wuhaozhuang Oil Field

The target layer S2 member, S3 upper sub-member and S3 lower sub-member of block Zhuang 62-66 of Wuhaozhuang Oilfield are characterized by low permeability, complex deposition, large changes in layer thickness and complex oil-water relation, with local tight reservoir developed. It is the nebulous understanding of reservoir characteristics that impedes the development of oilfield, which requests imperatively to conduct the research on diagenesis of low-permeability and tight sandstone reservoir. On the basis of the study of the reservoir rock, through the comprehensive analysis of core observation, identification of casting thin section, X-ray diffraction analysis of clay mineral materials and other comprehensive analysis, the types of reservoir diagenesis and the effect of diagenesis exerting on reservoir properties have been figured out, which helps to classify the diagenesis facies and determine the favorable reservoir distribution.In the study area, the overall rock types are syrosem-feldspar sandstone and feldspathic litharenite. There are varieties of pore types and the main is secondary pores including intergranular dissolved pores, intragranular pores, moldic pores and extra large pores with small amount of fracture. According to the types of pores and throats, pore structure characteristics are divided into five kinds. Diagenesis types include compaction, cementation, metasomatism and dissolution etc.. On the basis of vitrinite reflectance, transformation of clay minerals and the characteristics of authigenic minerals, the diagenetic stage of the research area is middle diagenetic phase A1 to middle diagenetic phase A2. Five types of diagenetic facies are recognized in the area including strong compaction-siliceous cementation facies, carbonate cementation facies, authigenic clay mineral cementation facies, compaction filling diagenesis facies and unstable component dissolution diagenetic facies. Combined with reservoir properties, diagenetic facies and pore structure characteristics, low permeability reservoir evaluation of study area has been made and four reservoir types have been determined.