Research In Characteristic Of Sediment And Diagenesis Of Chang 4+5 Oil Layers In Jiyuan-Longdong Area Of Ordos Basin

Based on the predecessors’ study of ordos basin sedimentary characteristics and geological background, combined with field observation, thin section identification, X-ray diffraction analysis, cathodoluminescence, high-pressure mercury injection analysis test means, think the warden 4+5 reservoir group of normal sedimentary types of rocks of terrigenous clastic rock and lime coagulation, so the rock combination type, pore characteristics and diagenesis of detailed research, and obtain the following:(1) the normal sedimentary terrigenous clastic rocks, the primary rocks in Jiyuan area are feldspar sandstone and feldspar lithic sandstone. Granularity is silt-fine sand level, Roundness is time-sub rounded corners,the lithic fragment is given priority to with volcanic rock lithic fragments and sedimentary rock lithic fragments, the interstitial material is given priority to such as calcite, kaolinite and chlorite film iron; Zhenbei area mainly lithic sandstone and feldspathic litharenite, granularity to fine grinding roundness is cone, the lithic fragment is given priority to with metamorphic rock and sedimentary rock the lithic fragments, the interstitial material in quartz overgrowth, iron, dolomite, mainly illite etc. Diagenesis process with acid-alkali diagenesis process for characteristics of alternating, forming a multiple zones for the development of secondary pore development zone. Pore types in a native-residual intergranular pore, feldspar solution pores, and kaolinite intercrystal pore and micro crack.(2) The tuffaceous rocks. Research district 4+5 section of this class of rock is mainly composed of feldspar, quartz and biotite, serrated edges of feldspar and quartz dissolution, biotite hydration, cambium between seam. The interstitial materials are mainly chlorite films, and early mature hydrocarbon, kaolinite. Due to the volcanic material for land and lake basins caused by the contraction of evaporation in high temperature alkaline diagenetic environment, the organic matter maturity, early appeared in hydrocarbon filling as the main diagenesis characteristics. Pore types in native residual intergranular pore, kaolinite intercrystal pore, feldspar dissolved pore.(3) According to the shape of capillary pressure curve and the various parameters, will study district 4+5 reservoir pore structure types are divided into four categories:ⅡA～ⅡB low expulsion pressure type, ⅡB out displacement pressure～ⅢA low displacement pressure, IIIA middle pressure and displacement ⅢA～ⅡB high displacement pressure type.(4) Through the study on the quantitative study of 4+5 reservoir rock pore, combined with the diagenesis types, think compaction and dissolution is the main factor to improve reservoir performance, and the cementation greatly reduces the storage properties.