Coal bed methane drilling — Specialized drilling to access methane-rich coal formations.

Coal bed methane (CBM) drilling is a highly specialized process for extracting natural gas that is trapped within coal seams. Unlike conventional drilling, which targets gas in porous rock formations, CBM drilling is designed to overcome a unique geological challenge: the gas is adsorbed, or physically attached, to the solid matrix of the coal. The process of releasing and capturing this gas requires a different set of technologies and a deep understanding of the coal seam's unique properties.

The Role of Dewatering
The most crucial step in CBM drilling is dewatering. The methane is held in the coal by hydrostatic pressure, or the weight of the water in the formation. The first step is to drill a well into the coal seam and then install a pump to remove the water. As the water is pumped out, the pressure drops. This reduction in pressure causes the methane to desorb, or release, from the coal surface. Once the pressure has been sufficiently reduced, the gas begins to flow up the wellbore.

The dewatering process can take months or even years, and the produced water must be managed carefully. It can be treated and reused for other purposes, such as in agriculture, or reinjected into a different formation.

Key Drilling Techniques
Several advanced drilling techniques have made CBM extraction a viable commercial enterprise.

Vertical Drilling: This is the most straightforward method, where a well is drilled straight down into a coal seam. While effective, it provides limited contact with the gas-rich coal.

Horizontal Drilling: This is a major innovation that has transformed the CBM industry. After drilling a vertical wellbore, the drill bit is turned horizontally, allowing it to run along the length of a coal seam for thousands of feet. This vastly increases the surface area exposed to the well, which significantly boosts gas production from a single well.