A New Method for Quantitative Study of Shale Oil Rock Type Combination and Reservoir Capacity: A Case Study from Chang 7 oil Member of the Yanchang Formation in the Longdong, Ordos Basin

Key words: 
• Ordos Basin /
• Chang 7 oil member /
• Shale oil /
• rock type combined form /
• rock type combination /
• reservoir capacity /
• quantitative study

Abstract: [Objective] In the geological logging of the shale oil core of Chang 7 oil Member of the Yanchang Formation in the Longdong, Ordos Basin, the resolution of single layer thickness of each rock type is basically 10 cm, resulting in a large number of rock type combinations being described as a single rock type for a long time. Exploring a new method for quantitative study of shale oil rock type combination and reservoir Capacity is conducive to the efficient exploration and development of shale oil of the Chang 7 oil member. [Methods] Through the high resolution core observation of the single layer thickness resolution of 1~5 cm, stereo microscope and thin section identification of 405 samples, as well as physical property analysis data, the shale oil rock type of Chang 7 oil member is re-identified, and then the rock type combination and reservoir capacity of Chang 7 oil member are explored quantitatively in this study. [Results] There are 11 main rock types in the shale oil of Chang 7 oil Member of the Yanchang Formation in the Longdong, Ordos Basin. Firstly, four rock type combined forms, including unitype, stratified type, interstratified type and interstratified type, and 65 rock type combinations are quantitatively divided for the first time in Chang 7 oil Member of the Yanchang Formation in the Longdong, Ordos Basin. Secondly, on the basis of quantitative evaluation of reservoir capacity of above 11 rock types, combined with the thickness percentage of each rock type, a new method for quantitatively calculating reservoir capacity of above 65 rock type combinations is proposed for the first time. [Conclusions] In conclusion, this study proves that to guide the efficient exploration and development of shale oil of Chang 7 oil Member, the long-term single rock type study of shale oil should be changed to the study of rock type combination study of shale oil in Chang 7 oil Member of the Yanchang Formation in the Longdong, Ordos Basin. However, this research is still in the exploratory stage and needs to be further improved by combined with a large number of shale oil exploration and development effect of Chang 7 oil Member.