Tom Copley maintains WikiMarcellus, which provides an objective, educational perspective on Marcellus Shale natural gas development.  It is a resource to any serious student of what’s happening with this industry.  Here is an example of Tom’s most recent effort; a summary of what stray gas migration is all about and what’s being done about it.

Stray natural gas migration refers to the movement of natural gas (mostly methane) through bedrock and soil. It can leak from a variety of sources, including reservoir rock, coal seams, landfill, or pipelines. It can also occur from drilling any well–gas, oil, or water–as well as from abandoned wells.  Whenever the water table is penetrated by boring a well, methane gas may be given an escape route.  It tends to move from areas of high pressure to low.

http://eidmarcellus.org/marcellus-shale/the-simple-facts-on-stray-g...