A Study On Fine Reservoir Characteristics And Water Flooding Policy For Complex Fault-block Oil Reservoir

There are many fault-blocks oilfield of Mesozoic and Cenozoic,the water injection policy is controlled by the reservoir properties.The paper took Huachang oilfield as an example,a systematic study of reservoir sensitivity,water injection policy and influence of production measures was carried out,by analysis of composition,structure,cement content,pore throat characteristics,diagenesis and heterogeneity-of rock.The results provided theoretical basis for the development of fault-blocks.The paper mainly studied diagenetic evolutionary stages,reservoir pore throat characteristics,reservoir characteristics of skeleton particles,reservoir characteristics of cement,water absorption characteristics,water injection limits and technology policy.The method,including inclusion homogenization temperature,vitrinite reflectance,pyrolysis Tmax,XRD,the common thin section,cast thin section analysis,mercury injection experiment,sensitivity experiment,laboratory physical simulation experiment and reservoir engineering,were used in the paper.It was observed from the microscopic chip,that the rock debris of Liuyi formation in the oilfild is quartziferous(metamorphic lithic),which has high compaction ability and could protect pores.Therefore,the quartz,chert and quartzose cuttings are classified as quartz type of detrital composition.The sandstone of Liuyi formation was considered as lithic sandstone,while it is actually feldspar quartz-sandstone.The Liuyi formation of fault-block Hua114,115,117 are flat structure and argillaceous tear crumbs,the Shale content increased obviously,which hindered the seepage of water,oil and gas in the reservoir.Meanwhile,it also results in lowering reservoir permeability and enhancing the heterogeneity and water sensitivity.The sedimentation and diagenesis the obvious control action on the reservoir on reservoir physical property.In order to study the anomalously high porosity region,further subdivided the mesogenetic stage A2 into A21 and A22 creatively.There are four anomalously high porosity region,medium-deep-depth are mainly produced by the kerogen degradation organic acid and clay mineral transformation of inorganic acid corrosion of the reservoir formation.The Lower limit depth of exploration is 4050 meters,by study of the anomalously high porosity region.Based on the geological research,the water flooding policy is studied using ways of mathematical method,reservoir engineering method and the physical model experiments.The calculation equation of reasonable injection-production ratio was established considering gas oil ratio and edge-bottom water energy.The production formula of high and low permeability layerwas derivated when water injected generally.The result was verified by long core doubletube parallel simulation experiment,and the permeability differential of development limits for seperated layer water injection is determined as 5.Acidification and seperated layer water injection are the preferred measures.The reasonable injection production ratio for different fault-block is 1.1~1.2,the reasonable pressure recovery rate is 0.57~1.45MPa/a,reasonable production rate is 0.9% ~1.6%,reasonable injection rate is 1% ~1.95%,reasonable well spacing is 250~280m,and the reasonable injection-production well ratio is 0.5~0.76.The method of injection in thin layers production in thick layers and seperated layer water injection can be used to improve the suitation of nonuniformity of injection profile and high water injection pressure.The mud acid is optimized to realize lowing injection pressure and improving injection volume.