Glossary - Introduction to Carbon Capture and Sequestration - page 557

Fracking

The propagation of fractures in a rock layer by a pressurized fl uid.
Induced hydraulic fracturing or hydrofracturing is a technique used to
release petroleum, natural gas (including shale gas, tight gas, and coal
seam gas), or other substances for extraction.
See also hydraulic fracturing.

Fracture permeability

Fractures can impart very high permeability to otherwise low-permeabil-
ity rocks. In fact, even a single fracture with a small aperture can impart
a fairly large overall permeability to a rock. It has been shown that frac-
tures provide permeability k (in m 2 ) according to the so-called Cubic Law,
which follows from the fl ow of a fl uid between two parallel plates:

3

Nb

k = ,

12

where N is the number of fractures per meter and b is the fracture
aperture.

Geo-engineering

Large-scale human intervention in processes of the earth.

Greenhouse gas

A greenhouse gas (GHG) is a gas in an atmosphere that absorbs and
emits radiation within the thermal infrared range. The primary greenhouse
gasses in the earth's atmosphere are water vapor, carbon dioxide, meth-
ane, nitrous oxide, and ozone.

Heat of absorption

The heat that is released if we absorb a gas in a liquid absorbent.
See also heat of desorption.