Research On Logging Evaluation Method For Carbonate Reservoirs In The First Member Of Maokou Formation In Southeastern Sichuan

The marine gas resources in the southeastern Sichuan Basin are very rich.In the early stage,many wells have achieved good oil and gas display in the Maokou Formation carbonate reservoir.Previous studies have shown that the carbonate reservoir has abundant organic matter,high thermal evolution degree and good transformation conditions,which has provided a great exploration and development potential in first member of Maokou Formation.However,the logging identification and classification evaluation techniques for the Maokou reservoir are still immature,which seriously restricts the oil and gas exploration and development process in the region.Therefore,it has become an urgent problem to form a set of comprehensive logging evaluation technology suitable for carbonate reservoirs in the first member of Maokou Formation to promote oil and gas exploration and development in southeastern Sichuan Basin.In view of the above problems,on the basis of understanding the geological law,this paper combines logging data,geology data,core analysis data,core photographs,gas testing data,mud logging data and other data,carries out the research on the relationship among reservoir "four properties”,analyses the relationship among lithology,physical property,electrical property and gas-bearing property,and determines the type of reservoir space.Combining with imaging data,this paper analyses and summarizes the logging response characteristics of different lithologies,structures and reservoirs,and establishes the logging identification methods of lithology,structure and reservoir.Based on mud logging data and gas test data,this paper uses P-S wave ratio method,deep-shallow lateral difference ratio method and P1/2 method to identify the gas reservoirs.In this paper,the shale content model is established by using conventional calculation formula,and the porosity calculation model is established by using cross plot method and dual mineral model.The saturation model is established based on Archie formula,and the parameters of rock electricity are determined according to the analysis of rock electricity experiment data.Based on the interpretation model,the lower limits of porosity and permeability are determined by mathematical statistics,classification of pore structure,minimum pore throat radius and conventional porosity-permeability relationship.Combining with mercury injection data,reservoir classification criteria are established.Finally,the above research methods are summarized,and fine logging interpretation is carried out for 5 key wells in the study area.The completion of this paper provides a complete set of logging evaluation scheme for the carbonate source rock reservoir of the first member of Maokou Formation in southeastern Sichuan,and also provides a reliable theoretical basis for subsequent exploration and development.