From mud to blue flame: how is shale gas produced?

China holds the largest recoverable shale gas resources in the world. Shale gas is an unconventional natural gas resource that resides in organic-rich mud shales, and is predominantly thermogenic in origin, formed through the transformation of organic matter under high temperature and pressure in deep geological settings. Due to the low porosity and permeability of shale reservoirs, the extraction of shale gas requires the use of unconventional techniques such as hydraulic fracturing. Hydraulic fracturing involves injecting high-pressure fluid into the formation to create fractures that release the trapped gas. In China, shale gas characterized by its clean-burning blue flame is considered a cleaner alternative to coal, contributing to the optimization of the national energy structure and the enhancement of energy security. This paper presents an overview of the origin, reservoir characteristics, and development technologies of shale gas, and explores the complete evolution process from organic matter to energy utilization.