Tracer Research Methods for Hydrocarbon Substances in Shale Oil Reservoirs

Shale oil is currently a key area for unconventional oil and gas exploration and represents a new field to ensure national energy security. As a major contributor to unconventional oil and gas in China, Sichuan Basin has enormous potential as an oil and gas resource.The exploration of Jurassic shale oil reservoirs is in its infancy, with diverse reservoir lithology and the ability to store oil and gas. Therefore, whether the generated hydrocarbon substances in shale are still gathering in situ or have undergone short distance migration plays a guiding role in the formulation of the next oil and gas exploration and development plan. In this study, we focused on the shale oil reservoirs of Lianggaoshan Formation in northeastern Sichuan Basin. Firstly, the lithological characteristics of shale oil reservoirs, as well as the physical and geochemical characteristics of different lithological reservoirs were determined via core observations and conventional reservoir geological characteristic experiments. Secondly, Laser confocal scanning microscopy (LCSM) was used to conduct three-dimensional modeling and quantitative testing of the shale oil occurrence characteristics of different lithological reservoirs. Finally, based on the differences in the occurrence of hydrocarbons in different lithological reservoirs and the physical characteristics of rocks, hydrocarbon migration is traced.The following three insights were obtained based on the experimental results: The crude oil produced was primarily composed of light hydrocarbons.The physical properties of sandstone profiles are superior, with a higher proportion of light hydrocarbons compared to shale reservoirs.The above experimental results indicate that hydrocarbons generated in shale migrated over short distances and were enriched in adjacent sandstone and siltstone bands with relatively desirable physical properties. This study provides experimental means and data support for subsequent flowability evaluations and development plan preparation for Jurassic shale oil extraction in northeastern Sichuan.