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Water Facts
• What is Methane?
• Methane Health and Safety
• Ground Water/Methane Investigations
• Ground Water Quantity Concerns
• Additional Fruitland Infill Water Testing
Information in this section was found at Encyclopædia Britannica > Methane, and Molecule of the Day: 9/28/98.
Additional information about septic systems is also available on the Internet at American Petroleum Institute > Facts About Natural Gas.
Methane also called MARSH GAS, colorless, odorless gas that occurs abundantly in nature as the chief constituent of natural gas, as a component of firedamp in coal mines, and as a product of the anaerobic bacterial decomposition of vegetable matter under water (hence its alternate name, marsh gas). Methane also is produced industrially by the destructive distillation of bituminous coal in the manufacture of coal gas and coke-oven gas. The decomposition of sludge by anaerobic bacteria in sewage-treatment processes also produces a gas rich in methane.
Methane in general is very stable, but mixtures of methane and air, with the methane content between 5 and 14 percent by volume, are explosive. Explosions of such mixtures have been frequent in coalmines and collieries and have been the cause of many mine disasters.
The chief source of methane is natural gas, which contains from 50 to 90 percent methane, depending on the source. Since commercial natural gas is composed largely of methane, their uses may for all practical purposes be considered identical. Because of its abundance, low cost, ease of handling, and cleanliness, such gas is widely used as a fuel in homes, commercial establishments, and factories.
In its natural state you can’t see or smell natural gas. It is colorless, odorless and lighter than air. Mercaptan, a chemical odorant, is added to natural gas so it can be smelled if it leaks.
Natural gas is made up mostly of methane, which has a simple hydrocarbon structure of one carbon atom and four hydrogen atoms (CH4). This means it burns easily and emits less pollution.
When natural gas is burned, it produces mostly carbon dioxide and water vapor—the same substances emitted when people breathe. Compared with other fossil fuels, natural gas emits the least amount of carbon dioxide into the air, as it is used—making natural gas the cleanest burning fossil fuel.
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Information in this section was found at: La Plata County Government publication, "Methane Health & Safety," and La Plata County Energy Council, Inc. publication, "Gas Facts."
Methane is a gas that is created naturally from decomposition. It is not toxic, not poisonous and does not cause cancer. However, methane gas is highly flammable and/or explosive under certain conditions. It will flame in the open and explode when confined. Methane can enter the home by way of water from domestic water well. Water from many wells in this area contains small concentrations of dissolved methane, which is not an explosion or fire threat. If methane is confined in an area with little or no ventilation and exposed to a heat source it can explode and will burn. Water wells confined within well houses or any other confined space can create a risk of explosion. Good ventilation will lessen the danger of any confined gas.
Methane gas in its natural state does not smell. The odor you smell from gas coming from a home stove has been treated with a chemical smell, mercaptan, so that gas leaks can be detected for safety reasons. Due to its odorless characteristic, you cannot rely on your sense of smell to detect methane. Numerous meters are available to monitor whether it is present.
To arrange for methane testing call La Plata County Government at (970) 382-6219.
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Ground Water/Methane Investigations
"Summary Report of Bradenhead Testing, Gas Well Remediation, and Ground Water Investigations, San Juan Basin, La Plata County, May 2000," by Colorado Oil and Gas Conservation Commission
Geologic reports, newspaper accounts, and sworn statements taken from old time residents of La Plata indicate that methane seepage occurred at most of the current seep locations along the outcrop of the Fruitland Formation and that many water wells contained methane prior to either conventional or coalbed methane development. In the early 1990’s, however, these conditions appeared to worsen in some areas. In response to these changes the Colorado Oil and Gas Conservation Commission ("COGCC") and the Bureau of Land Management ("BLM") in cooperation with the Southern Ute Indian Tribe ("SUIT"):
Have undertaken numerous large scale ground water investigations;
Have responded to individual landowners complaints to verify and to determine the nature, extent, and cause, if any, of these changes; and
Have adopted aggressive procedures to ensure that older gas wells that may have been acting as conduits for migration of gas into ground water aquifers were remediated and that new and future gas wells can not act as conduits.
There are 4 main areas where high concentrations of methane have been detected in the ground water. The methane in 2 of these areas appears to be created by bacterial activity (biogenic gas) and not related to gas operations. Both existing and new water wells in these areas have a high likelihood of containing methane because biological processes are still generating it. Methane in the other 2 areas appears to be thermogenic and probably has migrated into ground water aquifers via natural features such as fractures or pre-1988 conventional gas wells in which the aquifers and/or Fruitland Formation were not isolated. Although remediation or plugging of the offending conventional gas wells has eliminated the man-made conduits for gas migration, water wells in these areas may contain methane that is still entrained in the water.
Based upon current analytical data, methane concentrations in ground water in La Plata County appear to be relatively stable. Comparison of data from 198 water wells that have been sampled at least twice indicate that the methane concentrations in 129 wells have not changed significantly, in 50 wells the concentrations have decreased, and in 19 wells the concentration have increased.
One factor that is changing is the number of domestic water wells being drilled. Approximately 45% of all water well permits issued by the State Engineer’s Office in La Plata County were issued in the last 10 years. The obvious result of this is that more water wells could encounter methane that is already in the ground water.
The rigorous requirements for gas well completion, routine Bradenhead testing, and rapid remediation of any downhole problems that have been in place for about ten years have greatly reduced or eliminated the potential for existing and future gas wells to act as conduits for gas migration into ground water aquifers.
Bradenhead Testing and Gas Well Remediation
The COGCC and the BLM have implemented Bradenhead testing and gas well remediation programs that pertain to our respective jurisdictional wells. The purpose of these programs is to identify and remediate any wells that have the potential to contaminate ground water. Remediation of a well failing a bradenhead test proceeds even though there is usually no evidence that the particular well is contaminating ground water.
There are 2150 gas wells in La Plata County. Approximately half of these wells are Fruitland Coal Wells and the other half are conventional gas wells usually completed in the deeper Pictured Cliffs, Mesaverde or Dakota Formations.
All gas wells in La Plata County have been tested annually since January 1991 to ensure that methane gas is contained in the well bore. Since that time approximately 254 wells have failed this test and have been repaired. Although most wells only need to be repaired once, some wells have been repaired twice making a total of 269 repair procedures.
These repair procedures are of two types. One type of procedure replaces the wellhead seals. This is a mechanical repair that isolates gas leaking from the production casing to the surface casing at the surface. The other type of procedure requires placing cement outside of the production casing at a depth to isolate ground water aquifers and other geologic zones from leaking gas.
The number of wells requiring repairs has steadily dropped since the start of this program. In 1994 a high of 69 wells were repaired. The number of repairs in 1998 (the last complete year of statistics) was 18 wells.
Only approximately 36 repairs of the total 269 repair procedures have been performed on Fruitland Coal wells. The remaining procedures have been performed on Dakota and Mesaverde wells. Dakota and Mesaverde wells are generally older wells which did not have the casing cemented through the Fruitland Formation to prevent coalbed methane migration.
Since August 1988, COGCC rules (in cooperation with the BLM and the SUIT) have required that all Fruitland Coal wells have production casing cemented to surface. Cementing this casing to surface greatly reduces the possibility of methane gas collecting outside of the casing and migrating into ground water aquifers.
Approximately 1050 Fruitland Coal wells have been drilled in La Plata County. Of these wells approximately 800 have been drilled since this cementing requirement was initiated.
Ground Water and Gas Sampling and Analysis
Ground water samples have been collected from approximately 600 water wells and 26 gas wells in La Plata County. These data have been used to identify the potential sources of the methane gas detected in a number of water wells and to track changes in concentrations. In addition, an extensive database of other water quality parameters has been established. The largest single event occurred in 1994 when approximately 383 water samples were collected and analyzed. This work was co-sponsored by COGCC and BLM. The various ground water sampling and analysis events are summarized below:
1990 – USGS collected water samples from 70 domestic wells in the Animas River valley, south of Durango for chemical analysis.
1993 – BLM investigated domestic water wells in the vicinity of the HD Mountains as a follow up to the "HD Mountains EIS". The study was expanded to include approximately 200 domestic water well tests.
Early 1990’s – Ignacio-Blanco Groundwater Task Force and the State of Colorado Division of Water Resources performed other studies of methane in ground water, but the sampling and analytical techniques were different than those used by USGS and BLM so direct comparison of results was not possible.
1993 - Pine River Fruitland Coal Outcrop Investigative Team (IT) requested additional data gathering and technical assistance from BLM.
1994 – COGCC and BLM teamed up to evaluate methane occurrence in the aquifers of La Plata County beyond the Pine River area and not previously investigated. The goal of the project was to acquire information to determine whether gas wells had impacted the shallow ground water aquifers in La Plata County. A total of 383 sites were sampled including, 320 water wells not tested in the 1993 BLM study, re-testing 49 sites visited in 1993, and 14 new sites in the Pine River Ranches Subdivision area.
1995 – BLM conducted a further investigation of an area southeast of Durango in the Animas River Valley near the junction of Highway 550 and Highway 160. Nine additional domestic water wells and 5 gas wells were tested plus several other domestic water wells were re-tested.
1996 – BLM sampled approximately 100 wells in the HD Mountains and Bondad/Sunnyside Areas to monitor how effective gas well remediation was on reducing methane concentrations.
1998 – COGCC and BLM collected water samples from approximately 140 wells. These wells had been previously sampled and were located near remediated gas wells.
Analytical results of various sampling events were compared to determine whether gas well remediation was reducing the concentration of methane in the shallow aquifers. This type of comparison is difficult because a certain amount of fluctuation in methane concentration occurs normally in any water well containing methane. From this comparison it appears that the methane concentration has decreased in 50 water wells, increased in 19 wells, and remained about the same in 129 wells.
Industry ground water sampling: BP Amoco monitors 20 domestic water wells for the Tiffany Project. J.M. Huber monitors 24 domestic water wells as part of their 1998 Development Plan.
Many La Plata County natural gas producers contributed manpower and funding to help complete many of the studies mentioned in this section.
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In addition to water quality concerns, there continues to be concerns regarding impacts from gas well completion activities to water quantity in domestic water wells. COGCC has investigated several of these types of complaints. To date we have not found any indication that activities associated with gas wells have impacted ground water levels or quantity of water.
In at least 2 instances the drillers logs for the wells indicated that the wells were completed in shales and only produced limited amounts of water during the initial well tests conducted by the water well contractor.
Tertiary aged continental deposits underlie most of the area of ground water concern. The Animas Formation is a thick wedge of fluvial, composed of varicolored shale with interbedded breccia, conglomerate, and tuffaceous sandstone with some very thin coal beds. (These thin coal beds have been encountered and noted in domestic water wells completed in the Animas Formation. They are another potential source of methane in ground water.) The Nacimiento Formation is composed of interbedded sandstone and shale. The San Jose Formation is composed of interbedded sandstone, shale, and conglomerate. These fluvial deposits are extremely heterogeneous in nature and would account for localized variations in water quantity and quality.
In addition, seasonal fluctuations in ground water levels of more than 10 feet have been recorded in 1 of the 2 water wells continuously monitored by the USGS in the Florida Mesa area, southeast of Durango. Water wells in this 39 square mile area are completed in older gravels and alluvium that cap the mesa and could be expected to have seasonal fluctuations in water levels regardless of the wells’ domestic usage. The primary sources of recharge to this ground water system is infiltration of irrigation water (80%) and seepage from unlined irrigation canals and ditches (15%). Only about 5% of recharge in this area comes from infiltration of precipitation on non-irrigated areas. Studies such as this of other areas would be useful for understanding the ground water resources and water balance elsewhere in La Plata County.
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Information in this section was found at: Colorado Oil & Gas Conservation Commission > Order #112-156.
The [COGCC] Director shall apply appropriate drilling permit conditions to require water well sampling near proposed additional wells. Details of water well sampling requirements are on the COGCC's web site.
If free gas or a methane concentration level greater than 2 mg/L is detected in a water quality testing well, compositional analysis and carbon isotopic analyses of methane carbon shall be performed to determine gas type (thermogenic, biogenic or an intermediate mix of both). If the testing results reveal biogenic gas, no further isotopic testing shall be done. If the carbon isotope test results in a thermogenic or intermediate mix signature, annual testing shall be performed thereafter and an action plan shall be drafted by the operator to determine the source of the gas. If the methane concentration level increases by more than 5 mg/L between sampling periods, or increases to more than 10 mg/L, an action plan shall be drafted to determine the source of the gas.
The initial baseline testing shall occur prior to the drilling of the proposed additional well. Within one (1) year after completion of the proposed additional well, a "post completion" test shall be performed for the same parameters above and repeated three (3) and six (6) years thereafter. If no significant changes from the baseline have been identified after the third test (the six year test), no further testing shall be required. Additional "post completion" test(s) may be required if changes in water quality are identified during follow-up testing. The Director may require further water well sampling at any time in response to complaints from water well owners.
Copies of all test results described above shall be provided to the COGCC, La Plata County or Archuleta County and the landowner where the water quality testing well is located within three (3) months of collecting the samples used for the test.
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