Quantitative Logging Evaluation Method For Pore Structure Of Deep Paleogene Complex Lithologic Reservoirs

In the transitional zone of Marine and continental facies,there are many kinds of complex lithologic reservoirs,including glutenite,fine sandstone and bioclastic dolomite.Reservoir pore space types are diverse,particle size is different,pore throat distribution is uneven,the quantitative characterization of pore structure is difficult.The complex pore structure makes accurate fluid identification difficult,and the estimated production rate differs greatly from the actual tested production rate.In this paper,by analyzing the development characteristics,influencing factors and logging response characteristics of pore structure in three lithologic reservoirs of paleogene sandstone,sandstone and dolomite in Bohai Bay Basin,China,the evaluation method and characterization parameters of pore structure based on single pore throat configuration relationship and double pore throat configuration relationship of NUCLEAR magnetic resonance logging are proposed.The capillary pressure curve was constructed by multiple regression of NMR T2 geometric mean,mercury saturation and porosity for single pore-throat reservoir.The capillary pressure curve was constructed by power function relation between T2 and PC at large and small pore size for dual pore-throat reservoir.For the reservoir without NMR logging,a conventional logging pore structure evaluation method based on Swanson parameter is established.By analyzing the pore structure parameters of different lithology controlling permeability,the comprehensive characterization factors of reservoir pore structure are constructed,and a set of quantitative evaluation methods of complex lithology reservoir pore structure are finally formed.