HomeMy WebLinkAbout20092346.tiffSTATE OF
COLORADO
OIL&
GAS
CONSERVATION COMMISSION
DEPARTMENT OF NATURAL RESOURCES
Bill Ritter, Jr., Governor
1120 Lincoln St. Suite 801
Denver, CO 80203
Phone: (303) 894-2100
FAX: (303) 894-2109
www.colorado.gov/cogcc
August 7, 2009
Mr. and Mrs. Ellsworth
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Fort Lupton, CO 80621
RE: Ellsworth Water Well Investigation (WW Permit No. 201558)
SESE Section 16 — Township 2 North - Range 65 West
COGCC Complaint Investigation No. 200196553
Weld County, Colorado
Dear Mr. and Mrs. Ellsworth:
This letter summarizes the process, results, and conclusions of the Colorado Oil and Gas
Conservation Commission (COGCC) staff investigation into the occurrence of hydrocarbon
gases in your water well under COGCC Complaint Investigation No. 200196553.
The Division of Water Resources (DWR) permit number for your water well is No. 201558 and
according to the DWR water well record it was drilled in October 1998 to a total depth of 695
feet below the ground surface (fbgs) and completed as a Laramie -Fox Hills Aquifer water well.
The well is screened from 475 to 685 fbgs. The well was drilled under a permit issued to Ronald
Lakey of Longmont, Colorado. In 2001, the Dickhausens of Thornton, Colorado submitted to
DWR a Pump Installation and Test Report for this water well. The test report shows the
installation of a submersible water pump with an intake at a depth of 500 fbgs and a pumping
rate of 15 gallon per minute.
On or around September 18, 2008, Mrs. Ellsworth contacted COGCC staff for assistance in
investigating the occurrence of methane gas in your water well. You indicated that you had
recently purchased the property and water well at 20991 WCR 2, and that when the water well
was pumped you noticed significant bubbling in the water and when the water treatment system
was "back -washed" into the septic tank the septic pump shut off automatically. On your behalf,
a third party contractor had collected and analyzed samples of the gas collected from the house
kitchen sink and determined that the gas was methane. Because there are active oil and gas
production wells and facilities in the area in which you live, you were concerned that the
methane gas in your water well might be related to a release from one of these facilities/wells.
On August 10, 2008, you had also collected samples from the water well and submitted these
samples to Weld County Department of Public Health and Environment (WCDPHE) for
analysis. Methane was not one of the constituents analyzed by the WCDPHE. You have
provided the COGCC staff with the analytical results from that sampling.
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✓ DEPARTMENT OF NATURAL nCraig
RESOURCES: Harris Sherman, w Executive -Joshua B. Ep
COGCC COMMISSION: Richard Alwerd - Thomas L. Cem Dire - Da De Craig l Mark nviCutright -
onme Michael mewling B. THaupt-Jim Marlin - Harris Sherman
COGCC STAFF: David Neslin, Director - Debbie Baldwin, Environmental Manager - David K. Dillon, Engineering Manager
i�� 3//G' 2009-2346
August 7, 2009
Ellsworth — Complaint No. 200196553
Page 2
In response to your complaint, on September 22, 2008, COGCC staff collected samples from
your water well for analysis of general water quality parameters, organic compounds associated
with oil and gas production, gas composition and stable isotopes of methane and deuterium, and
for nuisance bacteria. Upon receipt of the analytical results the COGCC staff sent you a
summary letter on October 27, 2008, presenting and discussing the results from the COGCC
sampling. In addition, the COGCC letter compared the results with those from the WCDPHE
analyses. The methane gas present in the September 22, 2009, COGCC sample was identified as
being a mixture of thermogenic and biogenic gas and the heavier hydrocarbon gases were
thermogenic. The thermogenic gases are likely related to oil and gas operations.
As a result of the determination that the gas in your water well was in part thermogenic, the
COGCC staff began an investigation of the producing oil and gas wells in the vicinity of your
water well for evidence of a release of production gas into the Laramie -Fox Hills Aquifer. The
operators of these wells are Noble Energy (Noble) and Kerr McGee/Anadarko (KMG). COGCC
staff contacted Noble and KMG to inform them that a water well impacted by thermogenic gas
had been discovered and that the COGCC would be investigating the source of the gas.
From the date of your original contact with the COGCC, the staff has devoted significant
resources to try to determine the source of the thermogenic hydrocarbon gases in your water
well. Six staff members have been involved to varying degrees in this effort. As is the COGCC's
standard procedure, you have been kept informed about all phases of the investigation. When
available, analytical results and a discussion of the COGCC's interpretation of the results have
been sent to you. The COGCC staff has answered numerous inquiries from you totaling
approximately 40 separate email and telephone communications. In addition, staff has prepared
approximately 20 written communications for you explaining the steps being taken in our
investigation. The following is a summary of our investigation activities and conclusions.
ENGNEERING AND WATER WELL INVESTIGATION
Engineering Investigation — Oil and Gas Wells
Concurrent with evaluation of your water well sample results, the COGCC Engineering staff
initiated review of drilling, well construction, and well completion records for the 37 oil and gas
wells within a one -mile radius of your water well. The review included checking the surface
casing depth, checking whether the Laramie -Fox Hills Aquifer was protected by the well
construction, and checking whether there were anomalies in gas production that might indicate
gas leakage from the well.
Based on COGCC staff experience investigating impacts to ground water, we focused the field
testing of oil and gas wells to those within th mile of your water well. This is because, except in
very rare instances, oil and gas wells that have impacted water wells are located less than 1,000
feet from the impacted water well, so our process of field testing oil and gas wells located up to
1/2 mile or 2,640 feet from an impacted water well extends by more than 2t/ times this distance.
In addition, thermogenic gas or a mixture of thermogenic and biogenic gas was not detected in
August 7, 2009
Ellsworth — Complaint No. 200196553
Page 3
any other water wells so we conclude that the impact to the Laramie -Fox Hills Aquifer that is
affecting your well is localized.
There are nine oil and gas wells within'' /2 mile of your water well. On October 15, 2008,
COGCC staff witnessed measurement of bradenhead pressures on these nine wells. The
bradenhead valve is connected to the open space between the production casing and the surface
casing and opening the valve to measure pressure and check for gas and fluids is a technique
used to help determine whether there is a casing or wellhead leak. Bradenhead pressures were
not measured and fluids were not present in any of the nine wells tested.
On January 8, 2009, Noble performed a mechanical integrity test (MIT) on the Powers 21-22
well which had been selected by the COGCC staff for further investigation based on some earlier
well casing/well cementing issues. The MIT involves pressuring -up the production casing of an
oil and gas well and observing any pressure loss which would indicate a possible production
casing leak. This well passed the MIT. In March 2009, the remaining wells within the 1/2 mile
radius were MITed. All these wells passed the MITs.
The results of the bradenhead pressure measurements and MITs indicate that the oil and gas
wells within 1/2 mile of your water well are operating properly and not leaking gas, but do not
negate the possibility of a prior leak that was subsequently remediated.
Former Powers No. 1 well
Staff review of COGCC well files showed that an old well, the Powers No. 1 (API 05-123-
05076), had been drilled sometime around 1946 in Section 22, Township 2 North, Range 65
West, which is southeast of your property. However, the COGCC records regarding the Powers
No. I did not specify the exact well location or include information about the depth, casing, or
how the well was abandoned. Because of the limited amount of information in the COGCC
records and because this old well had the potential to be a source or conduit for ground water
contamination, the COGCC conducted a search for additional information about this well.
Records concerning the Powers No. 1 well were found at the Denver Earth Resources Library,
which provided a specific location and information about both well casing and depth. According
to the records, the Powers No. 1 well was spud on April 18, 1946 by J. Clayton and drilled to a
total depth of 1,005 fbgs with well casing set to a depth of 335 fbgs. Other than some
information about the rocks encountered during the drilling of the well (i.e., lithologic
information), no additional information was found.
Between May 26, 2009, and June 16, 2009, the COGCC reentered the old well bore, sampled the
well for gas and general water quality, and abandoned the well by cementing the borehole from
total depth to the surface. Results of a sample collected on May 27, 2009, show that the former
Powers No. 1 did not have gas in it and there were no unusual water quality results observed. A
second sample collected on June 11, 2009, was analyzed for gas composition and stable isotopes
of carbon and hydrogen. A small amount of biogenic methane gas, similar to the biogenic gas
that occurs frequently in the Laramie -Fox Hills aquifer, was detected.
August 7,2009
Ellsworth —Complaint No. 200196553
Page 4
As a result of the reentry and sampling, the COGCC staff determined that the Powers No. I well
is not the source of the thermogenic gas observed in your water well. The COGCC spent
approximately $107,000 on reentering and properly plugging this well.
Water Well Investigation
On February 20, 2009, COGCC staff collected a second sample of gas from your water well and
on March II, 2009, a second water sample was collected. The analytical results for these two
samples are similar to the results for the water and gas samples collected by staff on September
22, 2008.
Between October 22, 2008, and April 7, 2009, COGCC staff collected production gas samples
from the nine oil and gas wells within 1/2 mile of your water well for gas composition and stable
isotope analysis. As part of the COGCC staff evaluation of the theromgenic gas in your water
well, the analytical results of these production gas samples were compared to the analytical
results for the gas from your water well. Unfortunately, after a thorough review of all of the
analytical results the COGCC staff is unable to identify any of the oil and gas wells within 1/2
mile of your water well as the source of the thermogenic hydrocarbon gases (methane, ethane,
propane, iso- and n -butanes, iso- and n -pentanes, and hexanes) present in your well.
Throughout large areas of Weld County the Laramie -Fox Hills Aquifer, in which your water well
is completed, has naturally occurring bacterially produced methane (biogenic methane). The
source of this natural methane is likely from coals present in the aquifer. Isotopically and
compositionally, this biogenic gas has a distinctive signature that is different from the
composition of the thermogenic gas and the stable isotopes of the methane produced from the oil
and gas wells in your area. Generally, these differences make identifying the presence of
thermogenic gas in a water well versus naturally occurring biogenic gas relatively straight
forward. However, when the gas in a water well is a mixture of biogenic and thermogenic gas
the isotopic signature of the gas is not as definitive a tool for determining the source. When this
occurs, the evaluation of the other hydrocarbon gases, propane, iso- and n -butanes, iso- and n -
pentanes, and hexanes (C3 through C6), which are present in the production gas, is very
important and often helps in identifying a possible source. The biogenic gas in the Laramie -Fox
Hills Aquifer does not contain C3 through C6 gases and, when present in a Laramie -Fox Hills
Aquifer water well, it is evidence of an impact from thermogenic gas (as was noted in the
October 2008 evaluation of your water well).
Comparison of the C3 through C6 compounds from an impacted water well to those in the gas
produced from oil and gas wells in the area is a tool used by the COGCC staff to identify a
possible source. The COGCC staff looked at both the isotopes of methane and the occurrences
of the other hydrocarbon gases in the samples collected both from your water well and the oil
and gas wells. The methane gas in your water well is a mixture of both naturally occurring
biogenic gas and thermogenic gas which, as discussed earlier, makes the identification of a
specific source difficult. Based on isotopic evaluation of the methane in your water well and the
samples from the production wells, the COGCC staff are unable to identify a particular oil and
gas well as the source of thermogenic gas in your water well. Our evaluation of the C3 through
August 7, 2009
Ellsworth — Complaint No, 200196553
Page 5
C6 compounds from the production well samples and your water well also failed to positively
identify a particular oil and gas well as the source.
Other Water Well Sampling
As part of the investigation into the occurrence of methane gas in your water well and to
determine whether other water wells had been impacted, 26 water wells were sampled. This
sampling and analysis was conducted by the COGCC, Noble, and KMG. Thermogenic gas was
not detected in any of these other water wells. Because the results of this sampling and analysis
have been discussed in earlier communication and correspondence with you, they will not be
discussed in this letter. The COGCC spent approximately $30,000 collecting and analyzing
samples from water wells and oil and gas wells.
You have expressed concern that some of the samples collected from water wells were collected
at a time when nearby oil and gas wells had been "killed." You have further stated that the
"killing" of these wells rendered the analytical results invalid because it had effectively cut off
gas that was leaking out of a well or wells. However, it is COGCC's experience that if an oil and
gas well has leaked and impacted ground water the effects of that leak can be detected long after
the leak has been repaired or the well has been plugged and abandoned; therefore, we believe
that if another water well had been impacted by gas leaking from an oil and gas well the
thermogenic gas that would have been entrained in the ground water would still be present and
would have been detected in the water sample. That being said, if any of your neighbors still
believe that their water well contains thermogenic gas or has been impacted by gas leaking from
an oil and gas well they should contact us and we will collect additional samples from their water
well for laboratory analysis.
Mitigation of the Gas in Your Water Well
On March 21, 2009, Noble voluntarily began providing you with temporary substitute water for
domestic use at your home. By letter dated June 17, 2009, you and Noble jointly advised me that
you had recently agreed upon certain measures to further mitigate the natural gas detected in
your water well. That letter states that Noble will install a filtration system to remove the gas
from your water well and make such well safe for your use. The letter also states that you and
Noble have further agreed to cooperate and work diligently to resolve any remaining issues
between you. It is our understanding that the filtration system is designed to mitigate the
methane and other gases entrained in your water and eliminate possible fire or explosion hazards
and is now operating.
August 7, 2009
Ellsworth — Complaint No. 200196553
Page 6
CONCLUSION
The method used by the COGCC staff to investigate and address the impact to your water well
has been thorough and appropriate. The COGCC staff's conclusion, supported by all the
investigation records, is that your water well contains a mixture of both biogenic and
thermogenic gas and that the thermogenic gas appears to be from oil and gas activity; however,
the COGCC staff has been unable to identify any current activity or existing well as the source of
the impact. As previously discussed, all current oil and gas wells within %2 mile of your water
well are operating properly and not leaking gas, but this does not negate the possibility of a prior
leak that was subsequently remediated. Based on our experience investigating other groundwater
impacts, as well as our review of oil and gas well records and water well samples, we do not
believe that the gas in your water well is attributable to an oil and gas well located more than 1/2
mile away.
Because no responsible party for the water well impact can be identified, the staff will not be
issuing a notice of violation (NOAV) or pursuing enforcement against any oil and gas operator as a
result of the investigation of Complaint No. 200196553. Because Noble voluntarily has
constructed a water treatment system to mitigate the gas in your well water and because all oil and
gas wells within 1/2 mile of your water well are operating properly, the COGCC staff considers the
situation mitigated and COGCC complaint No. 200196553 closed. Nonetheless, if you wish, the
COGCC staff will continue to collect samples from your water well for gas composition and stable
isotope analysis on an annual basis. In the event that such analysis or any other future information
allows us to identify the party responsible for the thermogenic gas in your water well, then we may
issue an NOAV or pursue enforcement at that time.
Under COGCC Rule 522, you as the complainant, have the right to file an application for a hearing
with the Commission regarding this complaint if you are not satisfied with this resolution. If you
wish to apply for a hearing, please contact Rob Willis, COGCC Hearings Officer at 303-894-2100
ext. 5125.
If you have any questions or would like to discuss these matters further, please contact me at
303-894-2100 ext. 5122, or Debbie Baldwin, COGCC Environmental Manager at ext. 5111, or
Dave Dillon, COGCC Engineering Manager at ext. 5104.
Respectfully,
8r4.enan
David Neslin
Director
Colorado Oil & Gas Conservation Commission
cc: Weld County Commissioners
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