Shale Gas Opportunities and Challenges(页岩气带来的机遇与挑战).pdf

Shale Gas Opportunities and Challenges*

R. Marc Bustin1, A. Bustin1, D. Ross, G. Chalmers, V. Murthy, C. Laxmi, and
X. Cui

Search and Discovery Articles #40382 (2009)
Posted February 20, 2009

*Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008

1University of British Columbia

Synopsis

Shale gas is defined as a fine-grained reservoir in which gas is self-sourced, and some of the gas is stored in the sorbed state. Sorbed
gas is predominantly stored in anic fraction– anics are present. Shale gas is not just ‘shale’.

Productive gas shales range anic-rich, fine-grained rocks, such as the Antrim or Ohio Shale, to variable facies rocks, such as
Lewis Shale.

Pore size in fine-grained rocks is really small; pore size distribution is variable; porosity, which is variable (order of magnitude
variation), reflects mineralogy and fabric.

Maturity and TOC effect
Thermal maturation structurally anic fraction, creating more microporosity, hence potential adsorption sites
Slope of line showing absorbed gas capacity vs. TOC is proportional to maturity/kerogen type.

General Observations
• porosity decreases with diagenesis and effective stress

• quartz maybe positive (biogenic) or negatively (detrital) correlated with TOC
- more siliceous and silicified shales are more brittle than clay, organic or carbonate rich shales and have greater propensity to be
fractured and to be fraced - (greater Young’s modulus and lower Poisson’s Ratio)
- BUT TOO SILICOUS = NO K or Porosity
CRITICAL TO DEFINE MECHANICAL STRATIGRAPHY

Background—learnings to date

thick sequences of shale with variable amounts of gas exist in many/most basins

shales are extremely heterogeneous in their properties but at a scale not generally considered

early views anic geochemistry is “the” screen for prospectively is proving incorrect

evaluating gas in place and testin