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

The thesis was intended to study the medium-deep strata(the main formation of interest were Es2, Es3上, Es3中, Es3下 and Es4) of Puwei area in Dongpu depression with combination of the core, well logging, analytic experiment and the previous research achievements. The thesis researched the development characteristic, the limit of effective properties, the influencing factors and forming mechanism of Puwei area.The medium-deep reservoir has the following characteristics through analysis: (1)the main sandstone type is the subarkose, and the sublitbarenite take second place. The main reservoir space is secondary interstice, and fractures develop in the deep formation. (2)the primary diagenesis of the studying area is compaction, cementation, metasomatism and denudation, it can be known from those diagenesis and the vertical evolution of clay mineral that the diagenetic stage of the medium-deep strata in Puwei area is middle diagenetic substage A and B, the late diagenetic stage. (3)the limit of effective properties is calculated and verified through two different methods, and through the limit value, the four effective reservoir zones are identified. The paper analyses the evolution of effective pore using the method of inversion.The development of the effective reservoirs in medium-deep strata is affected by the original sedimentary conditions, hydrocarbon filling and the development of gypsolyte. Studies have shown that the physical properties of the fine sandstone in delta plain distributary channel facies and sublacustrine fan braided channel facies are better than others. The hydrocarbon filling favors the erosion of feldspar and carbonate cementation, and the porosity is proportional to the oil saturation, which demonstrates that hydrocarbon filling can improve the physical properties of reservoirs. The development of gypsolyte can lead to abnormal pressure, which is better for the conservation of properties, and through the method of doing statistics, it can be seen that the development of gypsolyte has positive impact on the porosity and permeability of effective reservoirs.