Methodology of Calculating Oil Saturation and the GOR of Shale Based on Logging Data

Because the accuracy of shale oil saturation calculated with geochemical pyrolysis parameters fails to meet agreed-upon requirements, the logging data of key shale oil core wells were utilized, and the ratio of oil saturation from core analysis to that from pyrolysis analysis was proposed as the scale coefficient, so as to correct the model of calculating oil saturation by pyrolysis. The case example analysis shows that the accuracy of the oil saturation calculated by the improved oil saturation calculation model by pyrolysis meets the requirements. In order to solve the problem of the inaccurate gas-oil ratio (GOR) of shale calculated with gas measurement values, two GOR calculation methods based on logging data were established. In the first method, ambient corrections of many factors such as well diameter, drilling time, discharge, core, and basic gas measurement value were carried out on the gas measurement total hydrocarbon curve. According to the definition of the GOR, the model of calculating the GOR with a multi-component method was established, and the applications of the hydrocarbon moisture method and balancing value method in the calculation of the GOR were tried. In the second method, the GOR calculation model based on the maturity index I_M was established with logging data. The case examples show that the two methods are simple and practical, and they complement each other to improve the accuracy of the GOR. The results show that the accuracy of shale oil saturation and GOR can be improved with the method of calculating shale oil saturation and GOR based on logging data.