Shale
gas has become one of the most important natural gas resources.
The Sichuan Basin in China is one of the main shale gas production
areas and has entered large-scale commercial development. The mechanism
of shale gas accumulation is an important scientific problem in shale
gas exploration. This work systematically summarizes the understanding
of shale gas accumulation in terms of shale gas generation mechanisms,
pore evolution mechanisms, gas migration mechanisms, and gas accumulation
models. This work reviews the formation process of methane in shale
and clarifies that the causes of methane formation vary according
to the evolutionary stage. The formation and evolution of organic
pores and mineral pores in shale are analyzed using a thermal simulation;
the organic pore content is found to vary significantly with evolutionary
stage. In addition, this work focuses on an analysis of the migration
mechanism of shale gas, discussing the impacts of shale anisotropy,
self-sealing, porosity and permeability, various forces, and pathway
availability on shale gas migration. In addition to the actual gas
content of the shale gas reservoir, shale gas accumulation is analyzed
using mathematical and evolutionary models, and the accumulation process
is revealed. This work provides important guidelines for shale gas
exploration in the Sichuan Basin, which has undergone complex tectonic
evolution.