Logging evaluation of shale oil “sweet spot” in Da’anzhai member, Longgang area, Sichuan Basin

Shale oil has received extensive attention all over the world. The Da’anzhai member is the most potential exploration member of shale oil of the Jurassic in Sichuan Basin. Due to the high maturity and light oil quality of shale in the Longgang area, it is a pioneer area for shale oil exploration in the Sichuan Basin. During the initial stage (started in 2020), the number of shale oil wells was small (only 4) and the samples were limited. In order to evaluate genetic potential in study area, it is critical to combine geochemical parameters and logging data. Through multiple regression of related logging curves, a logging calculation model for TOC (total organic carbon) in the study area is established. Based on this model, using the relationship between other geochemical parameters and TOC, a calculation model of the related parameters could be obtained. The high correlation between the model value and the measured value (all the fitting coefficients are greater than 0.7), indicates that this method is applicable. The results show that the Longgang area has a higher abundance of TOC (the distribution area of high TOC of Da2a sub-member in the study is wider, and its average of TOC is more than 1.5%), better oil-bearing properties and greater genetic potential in the Da2a sub-member (the average value of free hydrocarbon is 0.96 mg/g and its genetic potential average value is 1.94 mg/g). There are obvious zoning features on the plane, and the area with high geochemical parameters is east of well Pc1 (the genetic potential value is greater than 2.15 mg/g), which is a “sweet spot region” for shale oil exploration. These results are of great significance for shale oil exploration and development in Sichuan Basin.