ISSUE DATE: 08/27/08 

PROGRAM INFORMATION BULLETIN NO. P08-20 

FROM: KEVIN G. STRICKLIN

 Administrator for 

 Coal Mine Safety and Health 

SUBJECT: Surface Drilled Coalbed Methane Wells with Horizontal Branches in the 

Coal Seam 

Who needs this information?

Underground coal mine operators, miner’s representatives, coalbed methane producers, 

independent contractors, state mining agencies, Coal Mine Safety and Health 

enforcement personnel and other interested parties need this information. 

What is the purpose of this bulletin?

The bulletin is intended to inform the mining industry and coalbed methane industry of 

a methane inundation hazard that may occur if unplugged or inadequately plugged 

horizontal coalbed methane well systems are intersected during coal mining. 

Directionally drilling coalbed methane wells from the surface is a relatively new 

technology and plugging or other methods that will protect coal miners have not been 

established. 

Information

Due to the potential methane inundation hazard to miners, the Mine Safety and Health 

Administration (MSHA) has determined that the barrier specified in 30 C.F.R. § 75.1700, 

i.e., 300 feet in diameter, must be maintained by the mine operator to protect miners. 

This barrier must be maintained around all vertical and horizontal legs and branches of 

the gas well that are within the coal seam. 

Recent coalbed methane extraction technological developments include directionally 

drilled wells that utilize a vertical well drilled from the surface connecting to multiple 

horizontal legs that are located within coal seams. The horizontal legs can be developed 

over large areas (up to 2 square miles) and may contain many interconnected branches. 

The legs and branches in the coal seam can contain large volumes of pressurized 

methane that may inundate the coal mine if intersected during mine development. 

Plugging methods that have been attempted include injecting gel or cement into the 

well and its horizontal legs and branches. Plugging with gel, however, may not be safe 

because the gel can blow-out as the pressure builds up. Plugging the well with cement 
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may be a safer, though a more costly, alternative. Conventional cement plugs can be 

difficult to place in these wells due to the undulating horizontal nature of the holes, 

water cutting, gas cutting, numerous branches, length of the holes, and logistics of 

cement setting times. Plugging is further complicated by potential caving of the hole. 

Any plug that does not completely fill the system of holes can result in pressurized 

methane reservoirs in the remaining voids. 

Non-plugging methods to control the methane output from the well have been 

proposed. A system of water infusion seems to work well for the initial intersection. 

Water is infused at the full hydrostatic head for several months and then is pumped out 

immediately prior to intersection. The well is left open to the atmosphere or put on 

vacuum for the intersection. Problems develop when rubber packers are used to seal 

the holes to prevent the development entries from gassing off after intersection. 

Recharge pressures build back up and subsequent intersections often involve 

pressurized voids and methane influx. In-mine degas pipelines and vacuum systems 

may be useful to control subsequent intersections. Another non-plugging proposal is to 

“kill” the formation around the wellbore with bentonite slurry infused at hydrostatic or 

higher pressures. This could reduce the coal seam permeability for some distance 

around the wellbore and limit the inflow of methane. 

If a mine operator proposes to mine within the 300 ft. barrier near a well, the District 

Manager should consider the accuracy of the well location before permitting this 

encroachment. Any well location is subject to the normal inaccuracies and errors 

inherent in surveying of the well head location and the surveying of the mine. In 

addition, the instrumentation used in directionally drilled wells has a measurement 

error of approximately one degree [± 17.5 feet (ft.) per 1,000-ft. of hole length]. A 

petition for modification will be required to mine through the well or mine within the 

safe barrier as determined by the District Manager. 

What is the background for this bulletin?

A development section in an underground coal mine was recently inundated with 

methane after mining into an inadequately plugged directionally drilled gas well. This 

well was approximately 700 feet from the surface and had two 4,000-foot horizontal legs 

in the coal seam. The gel that was intended to plug this well did not contain the gas 

pressure. 

The Mine Safety and Health Administration (MSHA) supports and encourages CBM 

extraction because it can significantly reduce methane emissions in coal mines and has 

been proven to decrease the incidence of face ignitions in gassy coal mines. However, 

procedures to address the potential hazards presented by CBM wells must be 

developed and implemented to protect the coal miners who will be exposed to these 

wells. A long history of methane-related coal mine disasters in the United States 
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underscores the potential hazards that unplugged or incorrectly plugged CBM wells 

could present during mine intersection. 

What is MSHA’s authority for this Program Information Bulletin?

The Federal Mine Safety and Health Act of 1977 as amended, 30 U.S.C. § 801 et. seq.; 

30 C.F.R. § 75.1700. 

Is this Program Information Bulletin on the Internet?

This information bulletin may be viewed on the World Wide Web by accessing MSHA’s 

home page (http://www.msha.gov), choosing “Compliance Info” and “Program 

Information Bulletins.” 

Who is the MSHA contact person for this bulletin?

Coal Mine Safety and Health 

Erik Sherer, (202) 693-9523 

E-mail: Sherer.Hubert@dol.gov 

Who will receive this bulletin?

MSHA PPM holders 

Underground Mine Operators-Coal 

Miners’ Representatives-Coal 

Independent Contractors