This contract is a multi-tasked project with an overall objective of developing a portfolio of technologies to address produced-water issues in a comprehensive manner.

Colorado School of Mines (CSM), Golden, CO

Results
The project has been completed. The final report has been completed on the two year Produced Water Management and Beneficial Use project that was overseen by the Colorado Energy Research Institute (CERI) at Colorado School of Mines, Golden, Colorado. Large quantities of water are associated with the production of coalbed methane (CBM) in the Powder River Basin (PRB), Wyoming, and the chemistry of the water often makes it unsuitable for direct agricultural use, however, the water does hold potential for beneficial use mandating a water management strategy. The fundamental logic of this project was the recognition that no single treatment can be applied to all co-produced water from coal bed methane (CBM) operations. There are several unique challenges to the disposal of CBM water. The production of CBM water follows an inverse pattern compared to traditional wells (high to low). CBM wells need to maintain low reservoir pressures to promote gas production making the normal practice of re-injection counterproductive. The unique water chemistry of the produced water can reduce soil permeability, making surface disposal difficult. Finally, the produced water is potable, making it a valuable resource in the western US rather than an undesirable by-product, the usual case in traditional petroleum operations. Therefore, a variety of options were developed and evaluated to provide CBM operators with the most cost-effective and environmentally sound practices for co-produced water. While this project focused on the Powder River Basin of Wyoming, the management and treatment procedures can be exported to other CBM areas in the US.

Benefits
The opportunity to resolve the oil and gas industry’s growing problem with producing, handling, and treating produced water presents a potential double benefit to the Nation: boosting domestic hydrocarbon production while bolstering America’s fresh water supply.

The production of oil and gas—conventional as well as unconventional, notably coalbed natural gas (CBNG) extraction—also yields large volumes of water of varying quality. Due to this variability, there is no single treatment or handling scenario for all produced waters. Research by industry, government, and academia has provided treatment technologies and handling methods, usually with consideration for beneficial use. However, these approaches are frequently costly and often suitable for only one area or field. In addition, there is often no incentive to change current treatment methods, due to lack of market for the treated water or for the treatment byproduct.

As there is no single best method, producers do not have solid information on which treatment technique or which disposal method to use in a given produced-water scenario. The research in the produced-water arena is not easily accessible, often the chemistry and technical terminology make it difficult to understand, and many of the proven technologies in this area are considered too expensive. Thus, even though an appropriate solution may be available, it may not be utilized.

In response to this challenge, DOE’s Oil and Gas Environmental Solutions Program sponsors a comprehensive, integrated plan to address the issues related to treatment, handling, and beneficial use of produced water in a printed and/or electronic “cookbook” of best-management options and the benefits of utilizing these practices (including cost comparisons) for various scenarios. This long-term DOE project requires coordination with industry partners, national laboratories, universities, and other agencies or divisions as well as Federal and State governments working on this issue.

Summary 
This project is focused on the Powder River Basin of Wyoming, with the assumption that successful management and treatment procedures can be exported to other CBNG areas.

The project milestones to date follow, broken down by task:

• Task 1: Membrane-enhanced CBNG production to minimize produced water, University of Wyoming (UW). Laboratory mass transfer experiments were used to parameterize a mathematical model from which the gas composition within the fiber lumen can be determined as a function of fiber length. The limits of effective recovery were determined by normalizing model predictions to an average conventional well producing 1.6 x 104 m3 day-1 CH4 (550,000 scf/d). Using this approach, it was estimated that 4.1 x 105 m3 of CO2 would be sequestered daily, while the produced gas composition would be 95% CH4, 4.4% CO2, and 0.6% H2O vapor. A total of 16.8% of the dissolved CH4 in the formation water would be removed during a single pass. For a hypothetical coal seam 36.6 m thick located at an average depth of 107 m with a corresponding average pore pressure of 1.05 x 103 kPa and a lateral groundwater velocity of 100 cm day-1, 290,000 m2 of membrane surface area would be required. A coal seam at 457 m with a pore pressure of 4.48 MPa would require only 7728 m2 of membrane surface area, 97% fewer fibers as compared to the hypothetical coal seam located at 107 m. These calculations were made assuming methane is present in the coalbed water at the saturation limit with no free gas phase present.
• Task 2: Electrodialysis treatment of CBNG produced water for beneficial use, Argonne National Laboratory (see FWP49243 project fact sheet).
• Task 3: Isotopic tracing of CBNG produced water, University of Wyoming (UW). Task 3 used stable isotopic environmental tracers along with standard water quality data to accomplish three subtasks: 1) to monitor the infiltration and dispersion of coalbed methane (CBM)-produced water into the shallow subsurface, 2) to determine locations where coal seams are isolated from adjacent aquifers and co-produced water will be limited to coal, and 3) evaluate what information may be provided by isotopic analyses of carbon, oxygen, and hydrogen in CBM-co-produced waters. In subtask UW used the Sr isotopic ratio, 87Sr/86Sr, to trace the infiltration of product water and show a connection between changes in water quality and strontium concentration at an on-channel CBM disposal site. It is suggested that on-channel discharge shows promise for future disposal in that there are fewer salts in existing channels due to annual flushing. However, the amount and duration of CBM discharge may exceed the water mounding caused by annual flooding, in which case stream bank salts may be mobilized. In subtask 2 UW suggests that the Upper Wyodak coal zone aquifer in the Gillette and Schoonover areas is a well-confined combined sand and coal aquifer unit but that the Wyodak Rider coal zone aquifers are only partially confined allowing interactions between sandstone and possibly other coal aquifers with the Wyodak Rider aquifer. Faults in the northeastern part of the Powder River basin affect aquifer connectivity, either by acting as seals or conduits. The Sr isotopic ratio is not well-correlated to fracture pattern developed during the well enhancement process because there are many factors in addition to fracture pattern that control interactions between aquifers. In subtask 3 research shows that the fractionation in oxygen and hydrogen isotopes caused by evaporation of light-element isotopes can be used to identify watersheds that have been infiltrated by CBM holding ponds. This indicator could be useful when infiltration rates are uncertain. Our initial carbon isotopic results demonstrate that d13C of dissolved inorganic carbon (DIC) and DIC concentration in co-produced CBM water is distinct from shallow ground water and surface water in Powder River Basin. This may be a very useful indicator of the presence of CBM produced waters in the near-surface environment.
• Task 4: Geomechanics and the effectiveness of wellbore completion methods in CBNG water in the Powder River Basin, Stanford University. Large quantities of water are associated with the production of coalbed methane (CBM) in the Powder River Basin (PRB), Wyoming, and this water has high saline and sodium contents, making it unsuitable for agricultural use and environmentally damaging. In order to determine if there are ways for CBM operators to produce less CBM water Stanford evaluated CBM wellbore completion methods in the PRB. Project work found that CBM operators in the PRB routinely carry out water-enhancement on their wells, where water-enhancement procedures are used to connect the coal cleats to the wellbore to increase gas production. Operators in the PRB are routinely fracturing the coal through this water-enhancement process (Colmenares and Zoback, 2007). Stanford analyzed ~200 water-enhancement tests from CBM wells in the PRB in order to determine the magnitude of the least principal stress and the orientation of hydraulic fracture growth. Results found that both horizontal and vertical hydraulic fractures are created and that some wells with vertical hydraulic fractures produce excessive volumes of CBM water. The creation of both vertical and horizontal hydraulic fractures implies that the magnitude of the least principal stress is varying throughout the basin and this has lead us to define three different stress states in the PRB: areas that have active normal faults, areas that are slightly more compressive (either normal or strike-slip stress regimes) and finally, areas with reverse faulting regimes. Researchers observed that for the Big George coal, wells with excessive water production are within normal faulting areas, suggesting that vertical hydraulic fractures in communication with normal faults may play a role in the water production.
• Task 5: Evaluating produced water during CBNG extraction for land application in the Powder River Basin, PVES Inc. Irrigation with untreated Powder River Basin (PRB) CBM co-produced water can lead to the loss of soil structure, a process known as dispersion. Soil dispersion results in a compacted soil that has little permeability so that water runs off the surface rather than infiltrating, decreasing crop production. Soil dispersion is caused when divalent cations, primarily calcium and magnesium that normally form ionic bridges between clay particles are displaced by mono-valent cations such as sodium causing the bridge to be destroyed. A ratio know as the sodium adsorption ratio (SAR) that characterizes the amount of sodium is a water relative to the amount of magnesium and calcium is commonly used to predict when soil dispersion will occur. Typically, water with a SAR of less than 4 is considered to be safe for irrigation purposes, PRB water has a SAR much higher than 4. CBM water can cause soil dispersion in two ways. First, CBM water is typically high in sodium and low in divalent cations, leading to the displacement of divalent cations in the soil structure with sodium ions. Secondly, PRB CBM water also has a high carbonate concentration. The high carbonate concentration leads to scavenging of calcium and magnesium ions from the soil thorough the precipitation of CaCO3 and MgCO3 minerals, lowering the soil water SAR. Two strategies can be used to combat these effects. The mineral gypsum (CaSO4) can be added to the soil. Gypsum is highly soluble and increases the Ca2+ concentration in soil water. The other strategy commonly used is to add elemental sulfur as a soil amendment. Microbially catalyzed oxidation of elemental sulfur produces sulfuric acid, the acidic conditions promote off-gassing of the carbonate ions in the CBM water as CO2.
• Task 6: Regional siting criteria for CBNG infiltration ponds, Montana Bureau of Mines and Geology, Montana Technical University. Infiltration ponds provide an economical means of managing CBM production water. Water infiltrating from these ponds may recharge shallow aquifers, potentially enhancing ground-water resources. However, as the infiltrating water moves through the previously unsaturated material, a series of geochemical reactions may occur that increase TDS and the concentration of other constituents. Predicting these changes is an important step in successfully designing and siting infiltration ponds. Data from a 5-year study at the Coal Creek off-channel site show that about 64% of the total water discharged to the pond actually helped recharge shallow aquifers. However, reduced rates of infiltration with time at CBM ponds can be expected, especially at off-channel sites. Sodium in the CBM-production water appears to cause dispersion of the clays in the pond floor and walls, thus decreasing infiltration over a period of time. Even a small percentage of clay can result in reduced infiltration rates. The vertical hydraulic conductivity at the Coal Creek infiltration pond site was estimated to have decreased by one order of magnitude from approximately 0.1 to 0.01 feet/day, apparently in response to dispersion of clays.

  Multispectral satellite data were evaluated to determine if specific mineral species in the soils could be identified and associated with salt loading in the ground water beneath the Coal Creek pond. Analysis of ASTER data indicate dominance of epsomite (MgSO4*7H2O) in soils at the Coal Creek site which is consistent with water-quality changes measured beneath the pond. ASTER data may provide a useful tool to assess possible pond sites, but needs further evaluation. While this analysis did indicate a possible suite of specific mineral species, remote sensing data interpretations should be confirmed by soils analyses on the site.

• Task 7: Controls on the fate of CBNG waters and impacts to shallow aquifer quality, Pennsylvania State University. Analyses of well water level data indicate a continuing trend of groundwater mounding beneath the stream channel. The rate of mounding has decreased over time. Two well nests at different distances downstream of in-channel discharge sites exhibited water level increases (referenced to a control site) of 2.6 ft and 3.3 ft from July 2003-2004, and rises of 0.9 ft and ~1.2 ft from July 2004-2005. From fall 2005 through October, 2006, the relative water levels increased by ~0.8 ft. Water budget analysis shows that conveyance losses in the channel and ponds themselves account for ~50% of the discharged water, with the remainder of discharged water flowing down-channel out of the study area as artificial surface runoff - though this varies substantially through time. Based on infiltration rates deduced from water budget analyses, we project that runoff leaving the study site will fully infiltrate within 2 miles of stream length. The full time series of water budgets shows that water losses in ponds has decreased systematically over the study period. In contrast, conveyance losses in stream channels have increased and seasonal variation has increased as vegetation cover and transpiration have increased. The temporal trends in the water budget are a key finding, because they indicate (1) significantly increased peak transpiration losses in the channels over time resulting from vegetation growth, and (2) decreased infiltration rates in the ponds, most likely caused by disruption of clays and/or silting.
• Task 8: Field laboratory and standard method of testing performance of water-quality treatment systems, Montana Bureau of Mines and Geology, Montana Technical University. The purpose of Task 8 was to establish procedures and design and build a field laboratory for comparative evaluation of treatment technologies that are offered for reducing sodium content of coalbed-methane-production water.

  To accomplish this goal a mobile facility was designed and constructed to test proposed treatment units under field conditions. The facility will allow correlation between performances of treatment units from different manufacturers, and during the testing phase allow manufacturers to fine tune their systems to the demands of coalbed methane. Basic longevity of treatment systems will also be documented to allow gas companies to choose performance based on comparable testing. Testing will involve beta units and final productions units would likely be improved versions.

  The final report describes the need for testing, approach that will be used in testing, and the operating procedures for the testing facility. The test method includes a list of the critical test parameters, as provided by the Montana Department of Environmental Quality. This task was designed with 3 subtasks: 1) design and construct the mobile testing facility; 2) deploy the facility to a test site; and 3) apply the testing facility to treatment systems. The facility is completed and ready to be deployed to a test site. The first testing is currently scheduled for early spring, 2008.

  The facility consists of a camper-style shell for a pickup truck, a small cargo trailer and instrumentation. The instrumentation allows continuous measuring and recording of water flow rates, specific conductivity, water temperature, sodium concentration, pH and oxidation/reduction potential. The facility is powered by a portable generator, solar panels and a power-take off from the pickup truck and it can be plugged in to a standard 120V outlet.

• Task 9: Water treatment by injection, Montana Bureau of Mines and Geology, Montana Technical University. This task has been completed and the final report has been published and distributed to NETL. CBNG produced water in Montana is of sufficiently good quality for domestic and livestock uses. But it has high sodium adsorption ratio (SAR) values, making it unusable for irrigation for most of the soils in the area (SAR=[Na/(Ca+Mg)]½). Consequently, disposal options must preserve beneficial use while not degrading surface waters that are used for irrigation. The focus of this research was to identify specific potential injection targets. Channel sandstones are probably the best targets for injection because they have more favorable porosity and permeability and because injecting into coalbeds may have conflicts with future CBNG development. Six channel sandstone units were identified in the Tongue River Member, informally named ‘A’ through ‘F’ in ascending order. Clearly evident from isopach maps is that the channels are widely distributed and potential injection targets will not be available in every location where an injection well is desired. In other words, injection may not be technically feasible in all locations at any cost.
• Task 10: Ensuring that technology meshes with regulatory requirements, ANL (See FWP 15549csm project fact sheet)

This project has been completed. The Final Report is available below under "Additional Information".

Funding
The project was selected under the Focused Research in Federal Lands Access and Produced Water Management in Oil and Gas Exploration and Development solicitation DE-PS26-04NT15460-00, issued January 2004.

$2,176,198 

$549,402 (20% of total)

NETL - Jesse Garcia (jesse.garcia@netl.doe.gov or 918-699-2036)
CSM - Dag Nummedahl (nummedal@mines.edu or 303-384-2506)

Final Report [PDF-18.3MB]

Publications
Cramer, T. and D. W. Johnson, 2007, “Membrane gas transfer of methane and carbon dioxide in submerged coal deposits”, The North American Membrane Society Annual Conference, May 2007, Orlando, FL.

Pribyl, R., and M.A. Urynowicz, “The Effect of Swelling/Shrinkage on Gas Transfer Rates within Intact Cores of Powder River Basin Coals,” Rocky Mountain Section of the American Association of Petroleum Geologists, June 11-13, 2006. Billings, MT.

Colmenares, L.B., and M.D. Zoback, “Hydraulic Fracturing and Wellbore Completion of Coalbed Methane (CBNG) Wells in the Powder River Basin, Wyoming: Implications for Water and Gas Production,” AAPG Bulletin, 91, 51-67, 2007.

Ross, H.E., and Zoback, M. D., “Hydraulic communication between coalbeds and overlying sands in the Powder River Basin, Wyoming and Montana: Implications for reinjection of coalbed methane water,” American Geophysical Union, San Francisco, CA, December 11-15, 2006.

Ross, H. E. and Zoback, M. D., 2006, Sub-hydrostatic pore pressure in the Powder River Basin, WY and MT, and implications for re-injection of CBNG produced waters: AAPG-Rocky Mountain Section, Billings, MT, June 11-13.

Brinck, E. and Frost, C.D., submitted, Detecting infiltration and impacts of CBNG- produced water using strontium isotopes. Submitted to Ground Water, October 2006

Frost, C.D., and Brinck, E., “Strontium isotopic tracing of the effects of coal bed natural gas development on shallow and deep groundwater systems in the Powder River Basin, Wyoming,” Wyoming State Geological Survey Report of Investigations 55, p. 93-107, 2005.

Catherine Campbell, presentation on Subtask 2 for the University of Wyoming Graduate Student Symposium, Student Union, University of Wyoming, Laramie, WY, April 2006.

Wheaton, John R, and Brown, Terry, “Predicting changes in ground-water quality associated with coalbed methane infiltration ponds,” in Western Resources Project Final Report—Produced Groundwater Associated with Coalbed Natural Gas Production in the Powder River Basin, Wyoming State Geological Survey Report of Investigation No. 55, 2006.

Payne A., and Saffer, D.M., “Surface water hydrology and shallow groundwater effects of coalbed methane development, upper Beaver drainage, Powder River Basin, WY,” in Zoback, M.D. (Ed.), Wyoming State Geological Survey, Report of Investigations, V. 55, 2005.

D.A. Lopez, “Coalbed Methane Produced Water Disposal by Injection, PRB, MT,” Rocky Mountain Section of the American Association of Petroleum Geologists, June 11-13, 2006, Billings, MT.

Moon, P., S. Snyder, and T. Hayes, “Integrated Electrodialysis Process for CBNG Produced Water Treatment,” Paper No. 107248, abstract to AAPG Rocky Mountain Section, Jackson Hole, WY, June 11-13, 2006.

Hayes, T., P. Moon, and S. Snyder, “Electrodialysis for Cost-Effective CBNG Produced Water Treatment,” IPEC Conference, San Antonio, October 19, 2006.

Veil, J.A., “Overview of Water Disposal Regulations,” Produced-Water Project Meeting, Golden, CO, October 27-28, 2005.

Veil, J.A., “Environmental Policy and Regulatory Analysis Pave the Way for New Technology,” Produced Water Project Meeting, Golden, CO, January 5-6, 2005.