In the past, the oil and gas industry considered gas locked in tight, impermeable shale uneconomical to produce. However, advances in directional well drilling and reservoir stimulation have dramatically increased gas production from unconventional shales. Due to the demands for natural gas different countries in the world (e.g. Germany, Poland, Romania, Algeria, Saudi Arabia, China and others) follow North American experience to produce the gas from shales.
Unlike conventional reservoirs, unconventional gas shales are both the source and the reservoir rock for natural gas. In the shales, gas occupies pore spaces, and organic matter adsorbs gas on its surface. The reservoir systems have a gas-bearing strata that are not densely stratified, do not have a gas/water contact, and persist over a very large geographic area.
The shales may be as porous as other sedimentary reservoir rocks, their extremely small pore sizes make them relatively impermeable to gas flow, unless natural or artificial fractures occur. Directional drilling and “hydraulic fracturing” are instrumental in exploiting this resource; their application has opened up significant new resources in these rocks and added significant volumes to the natural gas supply in North America.
It is very important for gas producers to follow a well-defined screening procedure that helps them to decide whether to go after shale gas reservoirs exploitation. The selection criteria presented are meant to serve as the first-pass screening procedure that compares the candidate shale gas reservoir with other reservoirs that have been produced. Shale gas development history, reserves, similarities and differences, economics, regional prospective, screening, shale core analysis and shale gas in place estimates will be presented.

свернуть