Qualitative Identification And Quantitative Evaluation Of CO₂ In Baiyun Deep Water Area Of Eastern South China Sea

The baiyun deep water area in the eastern South China Sea is rich in natural gas.Carbon dioxide associated with oil and gas reduces the economic value,affects the evaluation of reservoir fluids,and brings great challenges to subsequent oil and gas development,therefore,it is necessary to carry out qualitative identification and quantitative evaluation of carbon dioxide in deep water area.In this paper,the neutron and density logging responses of carbon dioxide under different formation conditions are simulated by Monte Carlo by establishing a three dimensional rock volume model.Neutron and density logging cross plot,thermal cross section parameters and the neutron and density parameters cross plot and dual slope cross plot are carried on the qualitative identification,at the same time,based on the study between density and thermal cross section of the slope and the carbon dioxide saturation,the quantitative calculation model is established.The qualitative identification method and quantitative calculation model are verified in wells.Results show that,among the qualitative identification methods,the cross plot of neutron density logging parameters has a low identification degree,while the cross plot of thermal neutron cross section and neutron and density logging parameters has a certain identification degree but it is affected by formation porosity.The dual slope cross plot can effectively eliminate the influence of formation porosity and the identification accuracy of carbon dioxide in the study area is more than 92%,which has obvious advantages.There is a good correlation between the slope and carbon dioxide saturation,The quantitative calculation model established by this method has high saturation calculation accuracy.The interpretation results of wells prove the validity of the qualitative identification and quantitative calculation method of carbon dioxide.