The Research Of The Upper 4th Member Of Shahejie Formation In Dongfenggang Oil Field

Reservoir of the Upper 4th Member of Shahejie Formation in Dongfenggang oil field have a lot of change with depth,thin single-layer thickness and which is in the middle-late diagenesis, overall, physical propertiesthe in the area were less strong and non-homogeneous. Diagenesis research of the oil fields is an important aspect to reduce costs, improve developed efficiency and achieve a stable output.Sandstone in the research section is mainly to quartz-based components, debris content is the second and feldspar content is at least. Type of sandstone is mainly to sublitbarenite, feldspathic litharenite and lithoclastic feldspar are account for a large proportion. Clastic particles is mainly to quartz, feldspar and metamorphics debris. The main component of cement is carbonate,a small amount of siliceous cement and iron cement. Miscellaneous-based is mainly to mud and clay minerals. Interstitial material has a larger change, 6%-32%.The main diagenetic change of quartz in research section is secondary growth and corrosion; the main diagenetic change of feldspar is secondary growth, clay mineralization, carbonatation and dissolution. Chemical precipited cement including carbonate cement, silica cement and clay mineralization, and the main types of carbonate cements are calcite ,iron calcite, dolomite and iron dolomite; the main types of siliceous cement are quartz secondary growth; the main types of clay minerals including kaolinite, illite, andreattite and chlorite.Depth of the research section is from 2100m to 4200m, which change is larger and types of diagenetic including compaction pressure,solution, cementation, metasomasis, re-crystallization and the transformation of clay minerals. The original porosity of research section is about 10% at the highest, there is a clear downward trend with an increase in depth, compaction is the main type of diagenesis in the upper strata. The main types of cementation including carbonate cementation, silica cementation and clay mineral cementation. The main types of corrosion is feldspar particles, metamorphic rock debris and clay particles. The main types of metasomatism including carbonate alter quartz, feldspar and unstable debris particles, alternation between the carbonate minerals, carbonate minerals alter clay minerals and clay minerals alter quartz, feldspar. The main type of recrystallization is Carbonate minerals recrystallization.Stages of diagenesis in research section is divided into Medium-term A and Medium-term B, and the Medium-term A stage is divided into Medium A1sub-period and the A2 sub-period. Homogenization temperature of fluid inclusions is from 87℃to 153℃, the temperature range of diagenesis in research section is from 85℃to 150℃, the boundarie temperature between the medium-term diagenesis A phase and B phase is about 120℃, the boundarie temperature between A1 sub-period and the A2 sub-period is about 100℃.According to the type of diagenesis , diagenetic phase and the type of mineral under microscope, the form order, dissolution with the strong or weak, miscellaneous clay-based type and content-based, Diagenetic phase is divided respectively at Es4上1, Es4上2, Es4上3layer in the research section ,types of diagenetic phase including corrosion, cemented with calcium, cemented with clay, mixed cement and compaction phase of cracks.Diagenetic evolution in research section is at a higher degree and diagenesis is strong, skeleton particles and cement particles have been corrosed,and the corrosion of feldspar particles, metamorphic debris and mud debris particles are the most obvious solution, primary porosity is not developed, secondary porosity developed relatively. Control factors of reservoir diagenesis including compaction, cementation and dissolution, compaction and cementation reduce reservoir porosity, so that deteriorate to physical properties, while dissolution enhance porosity reservoir, so that improve the physical properties.