Evaluation On Low Permeability Reservoir Quality And Dessert Prediction Of Putaohua Oil Layer In The South Of Songliao Basin

Putaohua oil layer of Daqingzijing area belongs to the anastomosed deltaic deposits.The reservoir has low porosity,low permeability,thin interbed and big difference in reservoir quality and all of these influence the oil and gas exploration and development.Using well logging,mud logging,core observation,core analysis,well testing and early production test data,this paper carried out the research on reservoir characteristics of Putaohua oil layer,analysed the controlling factors of reservoir quality,established reservoir evaluation parameter system and conducted evaluation on low permeability reservoir quality and dessert prediction with appropriate evaluation methods.The study area developed shallow-slope anastomosed deltaic deposits and experienced relatively strong diagenetic transformation.The main rock types were siltstone and fine sandstone,calcareous cements were common,sorting and grinding were medium,which showed characteristics of low compositional maturity and medium structure maturity.The main pore type was secondary dissolution pore and the main type of pore structure was low-to-middle or low porosity and thin throat type.The reservoir average porosity was 14.8% and average permeability was 13.2×10-3?m2,belonged to typical low porosity and low permeability reservoir.On this basis,analysed the controlling factors of reservoir quality in respects of the structure,deposition and diagenesis.The study considered that a weaker compaction effect of the tectonic uplift region was favorable to the preservation of pore space,the rational allocation of reservoir sand bodies and faults was conducive to the hydrocarbon enrichment,the deposition condition controlled original reservoir physical properties,and the diagenesis was the key factor of improving the reservoir quality in late stage.Considering the above factors,evaluation on reservoir quality of ? sand group had been conducted through optimizing 7 parameters including the types of sand body,diagenetic facies,pore structures,porosity,permeability,effective thickness and net-gross ratio and revealed the imparity distribution characteristics of the reservoir.The results showed that the sand-body distribution characteristics of the main river channel controlled the macroscopic distribution of the reservoir and the braided channel crotch was the favorable area of class ? “dessert”.