Prediction of CO2 Saturation by Using Well Logging Data, in the Process of CO2-EOR and Geological Storage of CO2

Abstract

CO2 saturation monitoring is one of the key parameters to determine the geological storage of CO2. Because of the CO2-EOR or CO2 injection, the CO2-brine-rock interactions in reservoirs will lead to a series of complex changes in the mineral composition of rocks, porosity, pore structure, properties of formation water and residual oil saturation. At the same time, the difference of the CO2 spread range in reservoirs will cause the different CO2 saturation in different regions; in the same region, the reservoir CO2 saturation will also be different at the different time. To predict the complex variation of CO2 saturation in reservoirs, the processing and interpretation of the time-lapse logging data and the comparative analysis are needed. The steps for determining the CO2 saturation are as follows. Before CO2 injection, the background values of the formation water, rock mineral composition, porosity, pore structure and oil saturation are determined by the implementation of well logging. Firstly, the formation water parameters were monitored and determined at a specified time in the process of CO2 injection or CO2-EOR. Secondly, the time-lapse well logging was carried out to determine the rock mineral composition, porosity, pore structure, oil saturation and saturation CO2. The case-hole formation resistivity, pulsed neutron logging series and C/O logging series are often used to process and interpret the results of well logging data and to predict the residual oil and CO2 saturation. In addition, if the variety of porosity would be ignored, CO2 saturation is based on the prediction. CO2 saturation is equal to the parameter such as: ((the background value of the acoustic logging porosity) – (the time-lapse neutron logging porosity))/ (the background value of the acoustic logging porosity).