The Lower Paleozoic shale in south China has a
very high maturity and experienced strong tectonic deformation.
This character is quite different from the North
America shale and has inhibited the shale gas evaluation and
exploration in this area. The present paper reports a comprehensive
investigation of maturity, reservoir properties,
fluid pressure, gas content, preservation conditions, and
other relevant aspects of the Lower Paleozoic shale from the
Sichuan Basin and its surrounding areas. It is found that
within the main maturity range (2.5 %\EqRo\3.5 %) of
the shale, its porosity develops well, having a positive correlation
with the TOC content, and its gas content is controlled
mainly by the preservation conditions related to the
tectonic deformation, but shale with a super high maturity
(EqRo[3.5 %) is considered a high risk for shale gas
exploration. Taking the southern area of the Sichuan Basin
and the southeastern area of Chongqing as examples of
uplifted/folded and faulted/folded areas, respectively, geological
models of shale gas content and loss were proposed.
For the uplifted/folded area with a simple tectonic deformation,
the shale system (with a depth[2000 m) has largely
retained overpressure during uplifting without a great
loss of gas, and an industrial shale gas potential is generally
possible. However, for the faulted/folded area with a strong
tectonic deformation, the sealing condition of the shale
system was usually destroyed to a certain degree with a great
loss of free gas, which decreased the pressure coefficient and
resulted in a low production capacity. It is predicted that the
deeply buried shale ([3000 m) has a greater gas potential
and will become the focus for further exploration and
development in most of the south China region (outside the
Sichuan Basin).