Coal Bed Methane

The fol­low­ing is the sec­tion on Coal-bed Methane excerpt­ed from Oil and Gas at Your Door? — A Landown­er’s Guide to Oil and Gas Devel­op­ment, reprint­ed with per­mis­sion from a report pub­lished by the Oil & Gas Account­abil­i­ty Project.

As many landown­ers in Wyoming, Mon­tana, Col­orado, New Mex­i­co and Alaba­ma can attest, an increas­ing­ly sig­nif­i­cant source of nat­ur­al gas is coalbed methane. Two decades ago, coalbed methane was not a high­ly prof­itable source of nat­ur­al gas. By the year 2004, how­ev­er, CBM account­ed for more than 8% of nat­ur­al gas pro­duc­tion in the U.S.¹⁵³

Accord­ing to the CBM Asso­ci­a­tion of Alaba­ma, 13% of the land in the low­er 48 Unit­ed States has some coal under it, and in all coal deposits methane is found as a byprod­uct of the coal for­ma­tion process. His­tor­i­cal­ly, this methane was con­sid­ered a safe­ty haz­ard in the coal min­ing process and was pur­pose­ly vent­ed to the atmos­phere. Recent­ly, how­ev­er, com­pa­nies have begun to cap­ture the methane found in coal mines, as well as recov­er methane from coalbed deposits that are too deep to mine.¹⁵⁴

Coal beds are an attrac­tive prospect for devel­op­ment because of their abil­i­ty to retain large amounts of gas — coal is able to store six to sev­en times more gas than an equiv­a­lent vol­ume of rock com­mon to con­ven­tion­al gas reser­voirs.¹⁵⁵ On a dai­ly basis, how­ev­er, CBM wells typ­i­cal­ly do not pro­duce as much gas as con­ven­tion­al wells.¹⁵⁶ In most regions of the U.S., coalbed methane wells pro­duce between 100 and 500 thou­sand cubic feet (Mcf) per day, while the aver­age con­ven­tion­al well in the low­er 48 states pro­duces approx­i­mate­ly 1.7 mil­lion cubic feet (MMcf) per day.¹⁵⁷ There are, how­ev­er, some extreme­ly pro­duc­tive coalbed methane areas, such as the San Juan basin in Col­orado and New Mex­i­co, where some wells pro­duce up to 3 MMcf of methane per day.¹⁵⁸

The amount of methane in a coal deposit depends on the qual­i­ty and depth of the deposit. In gen­er­al, the high­er the ener­gy val­ue of the coal¹⁵⁹ and the deep­er the coal bed, the more methane in the deposit.¹⁶⁰

Methane is loose­ly bound to coal — held in place by the water in the coal deposits. The water con­tributes pres­sure that keeps methane gas attached to the coal. In CBM devel­op­ment, water is removed from the coal bed (by pump­ing), which decreas­es the pres­sure on the gas and allows it to detach from the coal and flow up the well.

Fig­ure I‑24. Typ­i­cal Coalbed Methane Well. Source: Ecos Consulting

In the ini­tial pro­duc­tion stage of coalbed methane, the wells pro­duce most­ly water. Even­tu­al­ly, as the coal beds near the pump­ing well are dewa­tered, the vol­ume of pumped water decreas­es and the pro­duc­tion of gas increas­es.¹⁶¹ Depend­ing on the geo­log­i­cal con­di­tions, it may take sev­er­al years to achieve full-scale gas pro­duc­tion. Gen­er­al­ly, the deep­er the coal bed the less water present, and the soon­er the well will begin to pro­duce gas.

Water removed from coal beds is known as pro­duced water. The amount of water pro­duced from most CBM wells is rel­a­tive­ly high com­pared to con­ven­tion­al gas wells because coal beds con­tain many frac­tures and pores that can con­tain and move large amounts of water.¹⁶²

CBM wells are drilled with tech­niques sim­i­lar to those used for con­ven­tion­al wells. In some regions where the coal beds are shal­low, small­er, less expen­sive rigs, such as mod­i­fied water-well drilling rigs, can be used to drill CBM wells, rather than the more expen­sive, spe­cial­ized oil and gas drilling rigs.¹⁶³

As with con­ven­tion­al gas wells, hydraulic frac­tur­ing is used as a pri­ma­ry means of stim­u­lat­ing gas flow in CBM wells.¹⁶⁴ Anoth­er gas stim­u­la­tion tech­nique, unique to CBM wells, is known as cav­i­ta­tion (also known as open-hole cav­i­ty completion).

Cav­i­ta­tion is a sim­i­lar phe­nom­e­non to open­ing a shak­en pop bot­tle, only on a much larg­er scale.¹⁶⁵ Water, and air or foam are pumped into the well to increase the pres­sure in the reser­voir. Short­ly there­after, the pres­sure is sud­den­ly released, and the well vio­lent­ly blows out, spew­ing gas, water, coal and rock frag­ments out of the well. This action is some­times referred to as “surg­ing,” and it is accom­pa­nied by a jet engine-like noise, which can last up to 15 min­utes.¹⁶⁶

The coal frag­ments and gas that escape from the well are direct­ed at an earth­en berm, which is sup­posed to pre­vent the mate­ri­als from enter­ing the greater envi­ron­ment. The gas is burned or flared, and the coal fines and flu­ids ini­tial­ly col­lect in a pit at the base of the berm. Some loose rock and coal mate­ri­als remains in the well. They are cleaned out by cir­cu­lat­ing water (and often a soap solu­tion or sur­fac­tant) with­in the well and pump­ing the mate­r­i­al into a pit. The coal refuse is then typ­i­cal­ly burned on-site in a pit, which is either referred to as a “burn pit” or “blooie pit.”

The cav­i­ta­tion process is repeat­ed sev­er­al dozen times over a 2‑week peri­od.¹⁶⁷ This results in an enlarge­ment of the ini­tial­ly drilled hole (well bore) by as much as 16 feet in diam­e­ter in the coal zone, as well as frac­tures that extend from the well bore.¹⁶⁸ If the cav­i­ta­tion frac­tures con­nect to nat­ur­al frac­tures in the coal, they pro­vide chan­nels for gas to more eas­i­ly flow to the well.

At the present time, cav­i­ta­tion is not wide­ly prac­ticed. The U.S. Depart­ment of Ener­gy report­ed that in 2000, the only “cav­i­ty fair­way” in the Unit­ed States was locat­ed in the cen­tral San Juan Basin, in Col­orado and New Mex­i­co.¹⁶⁹

Fig­ure I‑25. Cav­i­ta­tion Burn Pit

Produced Water

Pro­duced water qual­i­ty varies depend­ing pri­mar­i­ly upon the geol­o­gy of the coal for­ma­tion. Typ­i­cal­ly, salti­er water is pro­duced from deep­er coal for­ma­tions. Pro­duced water may con­tain nitrate, nitrite, chlo­rides, oth­er salts, ben­zene, toluene, eth­yl­ben­zene, oth­er min­er­als, met­als and high lev­els of total dis­solved solids.¹⁷⁰

Depend­ing on which state you live in, pro­duced water may be: dis­charged onto land, spread onto roads, dis­charged into evaporation/percolation pits, rein­ject­ed into aquifers, dis­charged into exist­ing water cours­es (with the prop­er per­mit), or dis­posed of in com­mer­cial facil­i­ties. In some states, stan­dards for pro­duced water dis­pos­al are becom­ing more rig­or­ous, and cer­tain dis­pos­al prac­tices are los­ing favor. Sur­face dis­charge, for exam­ple, is a con­tro­ver­sial method of dis­pos­al, as it can lead to a build-up of salts and oth­er sub­stances in the soil, and affect the pro­duc­tiv­i­ty of the land. In some states, re-injec­tion is the only option for dis­pos­al.¹⁷¹ See sec­tion on Impacts Asso­ci­at­ed with Oil and Gas Oper­a­tions for more infor­ma­tion on pro­duced water dis­pos­al options.

In some areas, coal beds may be impor­tant local or region­al aquifers (nat­ur­al under­ground water stor­age zones), and impor­tant sources for drink­ing water.¹⁷² It is impor­tant, there­fore, that landown­ers find out how com­pa­nies are plan­ning on dis­pos­ing of pro­duced water, and what impact its removal and dis­pos­al might have on water supplies.

Water Quality and Methane/Hydrogen Sulfide Migration

A study con­duct­ed by the US Envi­ron­men­tal Pro­tec­tion Agency (EPA) doc­u­ments a num­ber of exam­ples of water qual­i­ty impacts and oth­er issues encoun­tered after CBM extrac­tion occurred.¹⁷³ These include report­ed inci­dents of:

• Explo­sive lev­els of hydro­gen sul­fide and methane under build­ings and inside homes
• Death of veg­e­ta­tion (pos­si­bly due to seep­age of methane and decreased air in root zones)
• Increased con­cen­tra­tions of methane and hydro­gen sul­fide in domes­tic water wells
• Cloudy well water with increased sed­i­ment con­cen­tra­tions fol­low­ing hydraulic fracturing
• Strong odors and black coal fines in water wells
• Brown, slimy well water that smelled like petroleum
• Decrease in well water lev­els and sur­face water flows fol­low­ing hydraulic fracturing
• The dis­charge of pro­duced water cre­at­ing new ponds and swamps that were not nat­u­ral­ly
  
  occur­ring in par­tic­u­lar regions

Fig­ure I‑26.Improp­er­ly Con­tained Cav­i­ta­tion Prod­ucts.A work­er attempts to remove coal dust from trees.

A decline in water qual­i­ty may be cre­at­ed by hydraulic frac­tur­ing flu­ids. The EPA has stat­ed that

“if coalbeds are locat­ed with­in under­ground sources of drink­ing water (USDW), then any frac­tur­ing flu­ids inject­ed into coalbeds have the poten­tial to con­t­a­m­i­nate the USDW. Stim­u­la­tion flu­ids in coal pen­e­trate from 50 to 100 feet away from the frac­ture and into the sur­round­ing for­ma­tion. In these and oth­er cas­es, when stim­u­la­tion ceas­es and pro­duc­tion resumes, these chem­i­cals may not be com­plete­ly recov­ered and pumped back to the coalbed methane well, and, if mobile, may be avail­able to migrate through an aquifer.“¹⁷⁴

Water Quantity

Rur­al res­i­dents across the coun­try have expe­ri­enced decreas­es in the lev­els of their drink­ing water wells, as well as the dry­ing up of springs.¹⁷⁵ Mon­i­tor­ing wells main­tained by the fed­er­al Bureau of Land Man­age­ment in the Pow­der Riv­er Basin of Wyoming/Montana have indi­cat­ed a drop in the aquifer of more than 200 feet.¹⁷⁶ Esti­mates are that the water lev­els could drop to
a total of 600–800 feet over the course of CBM devel­op­ment in that basin.¹⁷⁷

Spontaneous Combustion of Dewatered Coalbeds

The EPA has report­ed the spon­ta­neous com­bus­tion and con­tin­ued burn­ing of com­plete­ly dewa­tered coalbeds as a con­cern relat­ed to CBM devel­op­ment.¹⁷⁸ When water is pumped out of coal seams, coal becomes exposed to oxy­gen, and coal fires are pos­si­ble. This can occur spon­ta­neous­ly, or from light­ning strikes or igni­tion by grass fires or wild­fires. The areas most like­ly to be the site of a coal fire are along the edges of basins where coal is close to the sur­face and oxy­gen can most eas­i­ly enter the coal when water is removed. At least one coal fire is burn­ing north of Sheri­dan, Wyoming. This old fire could expand as dewa­ter­ing low­ers the ground­wa­ter lev­el (thus expos­ing more coal to oxy­gen).¹⁷⁹ If coal fires occur, by-prod­ucts, such as poly­cyclic aro­mat­ic hydro­car­bons (PAHs), from the under­ground fires could poten­tial­ly lead to con­t­a­m­i­na­tion of under­ground sources of drink­ing water.¹⁸⁰

Compaction/Subsidence

Water is part of the fab­ric of a geo­log­ic for­ma­tion — it holds the rock open. When water is removed from the rock, the pore spaces are left open, and the rock can col­lapse. In parts of the world, there have been inci­dents where enor­mous quan­ti­ties of water have been removed from shal­low aquifers, fol­lowed by as much as a 40-foot drop (or sub­si­dence) in the sur­face of the land. The con­se­quences of the sub­si­dence have includ­ed the rup­tur­ing of util­i­ty lines (gas, sewage, water, elec­tric), col­lapse of build­ings, and dam­age to roads.¹⁸¹

Noise

From explo­ration through site aban­don­ment, noise is gen­er­at­ed by truck traf­fic, heavy equip­ment, seis­mic explo­sions, drilling rigs, motors that pow­er pumps, and gas com­pres­sors. The noise from all of the equip­ment may be a frus­tra­tion for landown­ers. The con­stant noise from pumps and com­pres­sors, how­ev­er, can great­ly affect a landown­er’s qual­i­ty of life, and have neg­a­tive impacts on live­stock and wildlife.

Cavitation Fire

In 2001, a fire out­side of Duran­go, Col­orado, was ignit­ed dur­ing the cav­i­ta­tion of a coalbed methane well. When the well was surged the escap­ing gas ignit­ed a grass fire, which quick­ly spread to sur­round­ing trees. For­tu­nate­ly, the fire did not reach any of the near­by res­i­dences. The total cost of the fire sup­pres­sion was esti­mat­ed by the Bureau of Land Man­age­ment to be $500,000.- Pear­son, Mark. Octo­ber, 2003. “Coalbed Methane Well Ignites For­est Fire.“¹⁸²

Cavitation

The coal brought to the sur­face (100 tons on aver­age) dur­ing cav­i­ta­tion is burned on site, which can last any­where from 7 to 10 days. The pol­lu­tion from burn­ing this waste coal can be a con­cern for near­by res­i­dents, espe­cial­ly because oil and gas well “com­ple­tion tech­niques” like cav­i­ta­tion are large­ly unreg­u­lat­ed (e.g., they are exempt from cer­tain envi­ron­men­tal laws like the Clean Air Act).

• Pol­lu­tion nor­mal­ly asso­ci­at­ed with coal burn­ing includes: nitro­gen oxides, car­bon diox­ide green­house gas­es, sul­fur diox­ide, lead and mercury.
• The noise asso­ci­at­ed with cav­i­ta­tion is a major con­cern for landown­ers, live­stock and wildlife. As men­tioned above, jet-like nois­es can last for up to 15 min­utes. If no notice is pro­vid­ed to landown­ers, the abrupt and shock­ing sound can star­tle live­stock and residents.
• Accord­ing to one landown­er, cav­i­ta­tion is one of the most “intim­i­dat­ing, dra­mat­ic and dis­rup­tive gas well process­es that impacts the liv­ing con­di­tions” of res­i­dents in the Igna­cio-Blan­co gas field in Col­orado and New Mex­i­co.¹⁸³ He describes: huge plumes of coal dust and methane, which is then flared, pro­duc­ing an enor­mous fire­ball blast, often larg­er than the height of the drilling rig; the blast also cre­ates shock waves; the mate­r­i­al removed from the cav­i­ty is almost entire­ly coal, which is burned in a “blooie pit,” cre­at­ing fire balls
  
  of the size men­tioned above.

It is pos­si­ble that coal debris could find its way into local drink­ing water wells. The under­ground explo­sions are not con­tained, and con­se­quent­ly, could come in con­tact with ground­wa­ter flows.

Decline in Property Values

A study in LaPla­ta Coun­ty, Col­orado, found that the loca­tion of a coalbed methane well on a prop­er­ty at the time of sale led to a net reduc­tion in sell­ing price of approx­i­mate­ly 22%.¹⁸⁴

Decline in property values of 22%

La Pla­ta Coun­try, CO

End­notes:

153.  
154.  
155. Petro­le­um Tech­nol­o­gy Trans­fer Coun­cil (PTTC). 2004. “Coalbed Methane Resources in the South­east.” (http://www.pttc.org/solutions/sol_2004/537.htm)
     
     
156. U.S. Envi­ron­men­tal Pro­tec­tion Agency (U.S. EPA). Octo­ber 2000. Pro­file of the Oil and Gas Extrac­tion Indus­try. EPA Office of Com­pli­ance Sec­tor Note­book Project. EPA/310-R-99–006. p.7. (http://www.epa.gov/compliance/resources/publications/assistance/sectors/notebooks/oil.html)
     
     
157. West­ern Orga­ni­za­tion of Resource Coun­cils (WORC). 2003. Fact­sheet. Coalbed methane devel­op­ment: Boon or bane for Rur­al Res­i­dents. (http://www.worc.org/pdfs/CBM.pdf)
     
     
158. Coalbed Methane Trans­ac­tions News (sources: Dow Jones Inter­ac­tive, dia­log and North­ern Lights). In Coal Bed Methane Alert, No. 13, August, 2002.
     
     
159. Stevens, Scott H., Kuuskraa, Jason, Kuuskraa, Vel­lo. 1998. Uncon­ven­tion­al Nat­ur­al Gas in the Unit­ed States: Pro­duc­tion, Reserves and Resource Poten­tial (1991–1997). Pre­pared for the Cal­i­for­nia Ener­gy Com­mis­sion. pp. 11–13. (http://www.energy.ca.gov/FR99/documents/98–12_STEVENS.PDF)
     
     
160. U.S. Ener­gy Infor­ma­tion Admin­is­tra­tion, U.S. Depart­ment of Ener­gy. 2001. “Recent Effi­cien­cy Improve­ments in the Nat­ur­al Gas Pro­duc­tion Indus­try,” U.S. Nat­ur­al Gas Mar­kets: Mid-Term Prospects for Nat­ur­al Gas Sup­ply. (http://www.eia.doe.gov/oiaf/servicerpt/natgas/boxtext.html)
     
     
161. Types of coal include: sub-bitu­mi­nous (soft, low­est ener­gy con­tent), bitu­mi­nous, and anthracite coal (hard, high­est ener­gy content).
     
     
162. WORC. See end­note 155.
     
     
163. U.S. Geo­log­i­cal Sur­vey (USGS). 2000. Water pro­duct­ed with Coal-bed Methane. USGS Fact Sheet 156–00. (http://pubs.usgs.gov/fs/fs-0156–00/fs-0156–00.pdf)
     
     
164. USGS. See end­note 161.
     
     
165. Wells, Richard B. August, 1999. “Coal Bed Methane Fields,” in the Nation­al Drillers Buy­ers Guide. (http://www.sci.uwaterloo.ca/earth/waton/f9913.html)
     
     
166. A Brief His­to­ry and Envi­ron­men­tal Obser­va­tions. A Work­ing Doc­u­ment Com­piled by the Bureau of Land Man­age­ment, San Juan Field Office. Decem­ber 1999. (http://oil-gas.state.co.us/)
     
     
167. La Pla­ta Coun­ty Ener­gy Coun­cil. Gas Facts — Pro­duc­tion Overview. (http://www.energycouncil.org/gasfacts/prodover.htm)
     
     
168. La Pla­ta Coun­ty Ener­gy Coun­cil. See end­note 165.
     
     
169. Bureau of Land Man­age­ment. June 2004. North­ern San Juan Coal Basin Methane Project Draft Envi­ron­men­tal Impact State­ment. Appen­dix E. “Well Field Devel­op­ment Activ­i­ties Com­mon to All Alter­na­tives,” p. E15. (p2-42 in Final EIS: http://www.nsjb-eis.net/Data/Chap-02.pdf)
     
     
170. McCal­lis­ter, Ted. (updat­ed 2002) Impact of Uncon­ven­tion­al Gas Tech­nol­o­gy in the Annu­al Ener­gy Out­look 2000. Ener­gy Infor­ma­tion Admin­is­tra­tion, US Depart­ment of Ener­gy. http://www.eia.doe.gov/oiaf/analysispaper/unconventional_gas.html
     
     
171. McCal­lis­ter, Ted. See end­note 168.
     
     
172. East of Hua­ja­tol­la Cit­i­zens Alliance. Infor­ma­tion Sheet #2, Pro­duced Water. (http://www.ehcitizens.org/cbmgas)
     
     
173. Boy­sen, Dei­dre B., Boy­sen, John E., and Boy­sen, Jes­si­ca A. “Strate­gic Pro­duced Water Man­age­ment and Dis­pos­al Eco­nom­ics in the Rocky Moun­tain Region.” Pre­sen­ta­tion at the Ground­wa­ter Pro­tec­tion Coun­cil Pro­duced Water Con­fer­ence. Oct 15–17, 2002. Col­orado Springs, CO. (http://www.gwpc.org/GWPC_Meetings/Information/PW2002/Papers/Deidre_B_Boysen_PWC2002.pdf)
     
     
174. USGS. See end­note 161.
     
     
175. U.S. Envi­ron­men­tal Pro­tec­tion Agency. August, 2002. DRAFT Eval­u­a­tion of Impacts to Under­ground Sources of Drink­ing Water by Hydraulic Frac­tur­ing of Coalbed Methane Reser­voirs. EPA 816-D-02–006. Chap­ter 6. Water Qual­i­ty Inci­dents. (http://www.epa.gov/safewater/uic/cbmstudy/docs.html)
     
     
176. U.S. EPA. pp. ES 1–5 and 3–10. See end­note 173. Cit­ed in a let­ter from the Nat­ur­al Resources Defense Coun­cil to the Chief of the EPA, Octo­ber 28, 2002.
     
     
177. WORC. p.3. See end­note 155.
     
     
178. WORC. p.3. See end­note 155.
     
     
179. Let­ter from John Bre­de­hoeft, Ph.D. to Joan Har­ri­g­an-Far­rel­ly, Chief, Under­ground Injec­tion Con­trol, Pre­ven­tion Pro­gram, Envi­ron­men­tal Pro­tec­tion Agency. May 22, 2003. Cit­ing data from the Final Envi­ron­men­tal Impact State­ment and Pro­posed Plan Amend­ment for the Pow­der Riv­er Basin Oil and Gas Project.. (http://www.earthworksaction.org/pubs/Bredehoeft_Testimony_Hydraulic_Fracturing.pdf)
     
     
180. U.S. EPA. August 2002. See end­note 173.
     
     
181. Tes­ti­mo­ny of Wal­ter R. Mer­schat (Sci­en­tif­ic Geo­chem­i­cal Ser­vices) at the hear­ing on “The Order­ly Devel­op­ment of Coalbed Methane Resources from Pub­lic Lands.” Sub­com­mit­tee on Ener­gy and Min­er­al Resources of the Com­mit­tee on Resources of the House of Rep­re­sen­ta­tives. Sept. 6, 2001. (text; pdf)
     
     
182. U.S. EPA. See end­note 173.
     
     
183. Mer­schat, Wal­ter. See end­note 179.
     
     
184. San Juan Cit­i­zens Alliance. Octo­ber, 2003. San Juan Cit­i­zens News, p.11. (http://www.sanjuancitizens.org/SJCANews_Oct03.pdf)
     
     
185. Cor­re­spon­dence between Carl West­on and the Oil and Gas Account­abil­i­ty Project.
     
     
186. BBC Research and Con­sult­ing. Novem­ber 12, 2001. Mea­sur­ing the Impact of Coalbed Methane Wells on Prop­er­ty Val­ues. p.1. (http://co.laplata.co.us/pdf/plan_doc/final_impactrpt/final_ir_appb.pdf)