Specific Stratigraphic Division and Interpretation Method Using DNA Sequencing of Cuttings for Sustainable Development of Shale Resources

The specific division and interpretation of shale formations are crucial for the sustainable development of shale reservoirs. Conventional methods, which rely on well logging curves, seismic analysis, and geochemistry often face high costs, subjective uncertainties, and limited resolution. However, microbial DNA distribution analysis provides a promising alternative. Previous studies have primarily applied underground microbial distribution to production dynamic monitoring, such as interwell communication, production profiling, and fracture height monitoring. However, the application of microbial DNA in specific stratigraphic division has not been fully explored. This paper presents an approach for stratigraphic division and interpretation based on DNA sequencing in shale cuttings. Using DNA sequencing results and rank abundance, a method is developed to establish a geological microbial response profile and monitor the microbial diversity. In addition, a preliminary division method is developed to identify representative bacteria markers for each formation. Furthermore, a specific division method is established through a principal coordinate analysis of bacteria markers. This method provides a resolution of 1–2 m and can assist in stratigraphic division when logging curves have multiple solutions. This user-friendly, environment-friendly, and cost-effective approach offers a more scientific foundation and technical support for the sustainable development of shale oil and gas in a carbon-constrained world.