Application of a lithofacies model to characterise the gas shale in the Wufeng and Lungmachi formations, NE Sichuan Basin, China

ABSTRACT

A practical model that uses a combination of the variations in total organic carbon (TOC) content and mineralogy is developed to determine the shale facies. By using a ternary plot, four main lithofacies and 14 subfacies were identified. This method is applied to describe the shale lithofacies and to identify the favourable lithofacies in the Wufeng and Lungmachi formations based on drill cores from well WX2, NE Sichuan Basin, China. The results show five classes of lithofacies are present and the organic-rich siliceous shale at the base of the Lungmachi Formation (LMF) is the most promising lithofacies, as it has the highest in-situ gas content, abundant TOC, and a high brittleness index, which are all favourable for the generation and development of shale gas. No significant changes in lateral continuity exist in the study area. The core based model can be used to quantify shale lithofacies in other areas.

KEYWORDS:

• Wufeng and Lungmachi formations
• shale gas
• lithofacies classification
• favourable lithofacies
• Sichuan Basin

Acknowledgements

The authors would like to thank LetPub (www.letpub.com) for providing linguistic assistance during the preparation of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by the National Science and Technology Major Project of the Ministry of Science and Technology of China [Project No. 2017ZX05035-001].