A new method for connate water saturation calculation using time-lapse logging data

Connate water saturation is an important parameter from well logging evaluation. In order to accurately determine reservoir connate water saturation using the time-lapse logging data, on the basis of the study of the mud filtrate dynamic invasion process and the dynamic change laws of reservoir parameters around borehole, this study established a logging response equation according to the volumetric element integration method. In this paper, the exponential water saturation relationships between water saturation and invasion time as well as the calculation algorithm of connate water saturation using the new dynamic response equation have been given. The results of two case studies from QingHai Oilfield have shown that the connate water saturation derived from the exponential water saturation relationships and the calculation algorithm of connate water saturation presented in this paper is in great agreement with the results from the field testing and results from mercury injection analysis.