Prediction of Shale Volume and Water Saturation using Pre-Stack Seismic and Well-Log Data in an Oil Field

The petrophysical parameters of the Ghar Formation are characterized in this study. A combination of pre-stack seismic data gathers and well-log data is used to estimate water saturation and shale volume in the Ghar reservoir. For such a purpose, first, the highest possible correlation between the well logs and the seismic inverse data was established. After extracting the best wavelet, an accurate relationship between the estimated and the values from core data was obtained. Secondly, using the data of another well, the validity of the constructed model was examined. The results showed that the combination of three attributes of instantaneous cosine of phase, √(Z_P ), and √(V_P ) is suitable to estimate the shale volume of the reservoir with considerable accuracy with a correlation coefficient of about ۷۰%. Although the two layers in the Ghar section have a shale volume of about ۱۰%, in general, the shale volume in the reservoir area is negligible. The logarithm of the ratio of compressional wave velocity to shear wave velocity attribute shows the highest correlation, about ۶۲%. Finally, validation of the results of the mentioned properties with unintroduced well-log data showed an accuracy of about ۹۰% in prediction.

Keywords:

Pre-stack Seismic gathers , Reservoir Shale volume , Seismic attributes , Water saturation , Well Logs