Estimation of Enriched Shale Oil Resource Potential in E(2)s(4)(L) of Damintun Sag in Bohai Bay Basin, China

摘要

Qualitative and quantitative evaluations of resource potential are of significant importance for both exploration and exploitation of shale oil. We investigate the shale oil resource potential in E(2)s(4)(L) (the lower submember of the fourth member of the Paleogene Shahejie Formation) of Damintun Sag by both qualitative and quantitative methods. From the viewpoint of qualitative evaluation, it is reasonable to hope that the target shale, with adequate oil-prone organic matter (OM) in the peak and late oil generation stage, forms a shale oil reservoir. The total oil content in shale is evaluated from free hydrocarbons in shale (S-1) by correcting the heavy and light hydrocarbons and the resins and asphaltenes. The total oil content is found to be over 4.45 times greater than the original S-1. The evaluation threshold of high-abundance oil is determined by both the total oil content (S-T) and the ratio of S-T to the total organic carbon content with values that are greater than 8 mg/g and 1, respectively. Based on the total oil content in shale and the evaluation threshold of high-abundance oil, the resource potential of high-abundance shale oil is obtained to be around 2.2 x 10(8) t. The average oil-bearing rate is about 0.033 m(3)/m(3), which is equivalent to that of Upper and Lower Bakken shale and much higher than that of the Middle Bakken shale. From the viewpoint of the resource potential and the oil-bearing rate, the shale oil in E(2)s(4)(L) of Damintun Sag is found to be promising. The evaluation results and the methods to correct the S-1 and to determine the high-abundance oil threshold are of practical importance for shale reservoir development.