The Reservoir Diagenesis And Its Influence On Reservoir Property In Tongfosi And Dalazi Formation Of Yanji Basin

New technologies and methods on oil and gas exploration shed light on newdevelopment and harvests. Secondary exploration of existing oil and gas fieldsincluding revealing the distribution pattern of oil and gas and predicting favorableexploration targets attracts highly-focused attention. This research focuses on Yanjibasin, delicately describes the overall reservoir features and discusses the maincontrolling factors of high quality reservoir.On the basis of collected information, this paper adopts the methods of polarizingmicroscope, image analysis system, cathodoluminescence, scanning electionmicroscopy and X-ray diffraction analysis.The rock types of target stratum are arkose and lithic arkose, the host rock aremainly biotite granites and andesited, based on the microscopic identification ofa largenumber of thin sections and references of the identified iresults collected.Observations of polarization microscope and scanning electron microscope showthat the paragenesis in the target stratum is listed as follows：illite/mixed layers of illiteand semctite/pyrite, chlorite/micro-calcite/ankerite, oil and gas charging/feldspardissolution/micro-quartz and overgrowth quartz, kaolinite, overgrowth quartz andmicro-albite, laumontite/laumontite vein, coarse crystalline calcite/calcite vein.The pore types of target stratum in Yanji basin include primary pores andsecondary pores. Secondary pores include intergranular dissolved pores, residualintergranular dissolved pores, moldic pores, intragranular dissolved pores of feldspar,intragranular dissolved pores of rock fragments. Primary pores mainly include primaryintergranular pores, residual intergranular pores and intercrystal pores. The proportion of secondary porosity is larger as the burial depth increases in Chaoyangchuan sag andDexin sag.Reservoir physical property presenta a low porosity and permeability. Dalazireservoir physical property is slightly better than Tongfosi’s. Four abnormally highporosity intervals are vertically developed:700-850m,1000-1200m,1300-1500m and2050-2250m from shallow to deep. The influences of diagenesis acting upon reservoirphysical property are two folds: the acid pore fluids (atmospheric water and organicacids) and crevice effectively improved reservoir physical property and form theanomalously high porosity zones (mainly secondary porosity); massly precipitation oflaumontite and coarse crystalline calcite leads to poor reservoir properties.