Britannica
Sources used in this answer
How is coal-bed methane stored inside underground coal seams?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
natural gas
The Troll A natural gas production platform in the North Sea, 80 km (50 miles) northwest of Bergen, Norway. Troll A, the largest movable structure ever built, rests on the seafloor some 300 metres (990 feet) below the surface and rises more than 100 metres (330 feet) above the sea. The platform regulates the recovery of gas from 40 wells located on the seafloor.
Methane is stored within underground coal seams through two primary mechanisms:
- Free Gas: A portion of the methane exists as free gas trapped within the natural joints and fractures of the coal seam.1
- Adsorbed Gas: The majority of the methane is adsorbedāmeaning it is held by molecular forcesāonto the internal surfaces of the coal's [micropores].12
Because coal possesses a high internal surface area, these pores can store significant quantities of gas. To extract this methane, wells are drilled into the seam, and water is pumped out to reduce the pressure. This pressure drop allows the adsorbed methane to desorb from the pore surfaces and migrate as free gas into the fracture systems, where it can then be collected through the wellbore.21