Formation Mechanism Of Medium-deep Buried Effective Reservoir In Huzhuangji Area Of Dongpu Depression

On the basis of the observation and description of the core and casting thin section, with the use of collected date about mercury injection, petrophysical property and so on, this thesis researched the mid-deep reservoir(mainly Es3-4) in Huzhuangji Area, Dongpu Depression. Combined with the former research results, we made comprehensively researches based on the analysis of regional geological background. This research includes reservoir development characteristics, identification of effective reservoir, controlling factors and reservoir formation mechanism.Huzhuangji Area has the feature of nearer provenance and multiple origins. The sedimentary assemblage is mainly fan delta sandstones of coast and shallow lake.Feldspathic lithic quartz sandstone is the main kind of sandstone, and the reservoir is relatively fine-grained, composed of siltstone and fine sandstone, and a little anisomerous sandstone. The cemented type is mostly hole-cemented, with sorting levels range from poor to well. In reservoir there are mainly angular and subangular grains with relatively good roundness. The whole area can be divided into three steps by placanticline fault zone and Shijiaji fult zone: Step I mainly developed secondary pores and micro fractures, while the Step II and III are shallower and the physical properties are better preserved, so they belong to medium porosity-low permeability, and medium porosity, medium permeability reservoirs. Three effective porosity zones are vertically developed in the second and third steps. The mid-deep reservoir in the study area can be divided into three types. According to the comparison of reservoir properties of Es3-4, reservoirs of Type I and II are mainly distributed across Step II and III, and reservoirs of Step II have better properties than reservoirs of the other two steps. Reservoirs of Step I and II have reached middle diagenetic period, and reservoirs of Step III is still among B sub-stage of early diagenetic period. There are various kinds of diagenetic types, among which, compaction, cementation and metasomatism are the main factors to decreasing reservoir properties, especially the carbonate cementation. On the other hand, resolution is the main factor to improving reservoir properties. The controlling factors of mid-deep effective reservoirs in Huzhuangji Area include sedimentary environment, reservoir mono-layer thickness, structural movement, diagenesis and hydrocarbon filling.Based on the researches of diagenetic evolution and controlling factors, the effective reservoir formation mechanism is: the effective reservoirs of Step I and II mainly belong to erosion type and hydrocarbon filling type; while of Step III those mainly belong to erosion type.