Shale is a rock; a very fine grained, organic-rich, sedimentary rock. Geologists have known for years that natural gas may be found in shale rock but until a short time ago it could not be cost-effectively extracted. However, recently we have had:
- Major advances in horizontal drilling;
- Major advances in hydraulic fracturing.
It is possible to combine these processes to form an extraction process known as ‘fracking’ or ‘unconventional’ gas production.
Natural gas vs shale gas
Conventional gas reservoirs are created when natural gas moves towards the surface from an organic-rich source formation into highly permeable reservoir rock, where an overlying layer of impermeable rock then traps it. In contrast, shale gas resources form within ...