Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
Contents lists available at ScienceDirect
Journal of Unconventional Oil and Gas Resources
journal homepage: www.elsevier.com/locate/juogr
Regular Articles
Coalbed methane produced water screening tool for treatment technology
and beneficial use
Megan H. Plumlee a,⇑, Jean-François Debroux a, Dawn Taffler a, James W. Graydon a, Xanthe Mayer b,
Katharine G. Dahm b,1, Nathan T. Hancock b, Katie L. Guerra b,1, Pei Xu b,2, Jörg E. Drewes b,3, Tzahi Y. Cath b,⇑
a
b
Kennedy/Jenks Consultants, San Francisco, CA 94107, United States
Colorado School of Mines, Golden, CO 80401, United States
a r t i c l e
i n f o
Article history:
Received 8 June 2013
Revised 1 November 2013
Accepted 13 December 2013
Available online 28 December 2013
Keywords:
Produced water
Beneficial use
Environment
Treatment costs
Coal bed methane
a b s t r a c t
Produced water is a byproduct of oil and gas production and represents the largest volume waste stream
in the oil and gas industry. Due to the high demand for water and the costs associated with current produced water disposal practices, energy companies and local water users are interested in cost-effective
alternatives for beneficial use of produced water. The main objective of this study was to apply a previously developed and publicly available coalbed methane produced water screening tool to two simulated
case studies to determine site-specific produced water treatment technologies and beneficial use options,
as well as costs, using realistic conditions and assumptions. Case studies were located in the Powder River
(Wyoming) and San Juan (New Mexico) Basins. Potential beneficial uses evaluated include crop irrigation,
on-site use, potable use, and instream flow augmentation. The screening tool recommended treatment
trains capable of generating the water quality required for beneficial use at overall project costs that were
comparable to or less than existing produced water disposal costs, given site-specific conditions and
source (raw produced) water quality. In this way, the tool may be used to perform a screening-level cost
estimate for a particular site to determine whether the costs per barrel for beneficial use are more or less
than site-specific disposal costs. The demonstrated technical and economic feasibility provide incentives
to address the institutional and legal challenges associated with beneficial use of produced water.
Ó 2013 Elsevier Ltd. All rights reserved.
Introduction
Water is generated as a byproduct of oil and gas production and
represents the largest volume waste stream in the industry (GWI,
2011). For coalbed methane (CBM) (coalbed natural gas), produced
water is pumped to the surface during well development and production, dewatering the formation to enable release of gas from the
coal seams. CBM production in the western United States (US) has
grown significantly during the past two decades and will play a key
role in the nation’s energy portfolio in the future. Water produced
during gas extraction must be managed and disposed of according
to state and federal regulatory and permit requirements, and
⇑ Corresponding authors. Address: Kennedy/Jenks Consultants, 303 Second St.,
Suite 300 South, San Francisco, CA 94107, United States. Tel.: +1 (415) 243 2471
(M.H. Plumlee). Address: Department of Civil and Environmental Engineering,
Colorado School of Mines, 1500 Illinois St., Golden, CO 80401, United States.
Tel.: +1 (303) 273 3402 (T.Y. Cath).
E-mail addresses: MeganPlumlee@KennedyJenks.com (M.H. Plumlee), tcath@
mines.edu (T.Y. Cath).
1
Present address: Bureau of Reclamation, Denver, CO 80225, United States.
2
Present address: New Mexico State University, Las Cruces, NM 88011, United
States.
3
Present address: Technische Universität München, 85748 Garching, Germany.
2213-3976/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.juogr.2013.12.002
therefore produced water is a significant factor in the profitability
of oil and gas production wells. Once the cost of managing and disposing of produced water reaches a critical threshold relative to
the value of extracted gas, the CBM well is ‘‘shut in’’ (gas production is discontinued). Produced water disposal is typically via deep
well injection or treatment and discharge, and therefore represents
an operational challenge, an environmental risk, and a major cost
for energy companies (NRC, 2010).
Faced with increasing regulations, discharge water quality
requirements, and costs associated with current disposal practices,
energy companies are interested in cost-effective alternatives for
disposal or beneficial use of their produced water. Produced water
quantity, supply duration, and quality are key factors in evaluating
potential beneficial uses. Beneficial use of produced water has the
potential to minimize environmental impacts while providing a
cost effective alternative to disposal, enhancing longevity and
therefore gas recovery of CBM and gas shale fields. It also represents a new water source, potentially significant for the arid and
semi-arid west of the United States and other regions around the
globe. However, beneficial use of produced water faces many technical, economic, regulatory, and institutional challenges.
More than 80% of current US CBM production takes place in the
Rocky Mountain region, which includes the Powder River and San
M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
Juan Basins (Fig. 1). These two basins capture and contrast the
known range of produced water quantity, quality, and management in western CBM basins (NRC, 2010) and were therefore selected as the locations for the case studies evaluated. The Powder
River Basin extends between Wyoming and Montana, encompassing more than 25,000 square miles. The number of wells, gas production, and associated water production in the basin have
increased dramatically since 1997. CBM and co-produced water
are extracted from coal layers in the Paleocene Fort Union Formation and the overlying Eocene Wasatch Formation. The coal beds in
the Fort Union Formation are on average 25 feet thick (NRC, 2010;
Rice et al., 2002). The San Juan Basin covers approximately 7500
square miles in northwestern New Mexico and southwestern Colorado, with the majority located in the New Mexico portion of the
basin (Fig. 1). Much of the CBM development in the San Juan Basin
began in the 1980s, and by 2009, over 7000 CBM wells were active
in the basin (NRC, 2010). The main methane-bearing unit is the
Fruitland Formation, with CBM production at depths ranging from
550 to 4000 feet (NRC, 2010). The average thickness of coal seams
is 6–9 feet with a maximum of 40 feet (ALL, 2003).
The main objective of the present study was to apply a previously developed and publicly available spreadsheet-based screening tool for CBM produced water to two simulated case studies
to determine site-specific produced water treatment technologies
and beneficial use options, using realistic conditions and assumptions. Potential beneficial uses that were evaluated include crop
23
irrigation, on-site use, potable use, and instream flow augmentation, among others.
Methodology
Case studies development
Two simulated case studies were evaluated using the Produced
Water Treatment and Beneficial Use Screening Tool (Screening
Tool). The Screening Tool was previously developed by the
Colorado School of Mines, Kennedy/Jenks Consultants, Stratus
Consulting, and Argonne National Laboratory as a decision framework to aid in the evaluation of CBM produced water treatment
and use given particular site conditions and user preferences
(CSM/AQWATEC, 2013a). The Screening Tool was developed as part
of an effort to address a lack of public information on selecting and
applying technologies to treat produced water for beneficial use,
increasingly important as interest in beneficial use of produced
water grows (Stewart and Takaichi, 2007). The Screening Tool
and related information are available on the project website
(CSM/AQWATEC, 2013b), including a case study report that
provides screenshots of the tool. Potential users include energy
companies and water practitioners that are interested in reducing
the disposal costs associated with, and the beneficial use of,
produced water.
Given CBM produced water volume, quality, anticipated supply
duration, and other conditions, the Screening Tool was used to
determine treatment technology alternatives and costs, potential
beneficial uses, and overall project costs for these uses. The Screening Tool also predicts treated water quality for the recommended
treatment train. The simulated case studies use data and information that are representative of the selected site locations. This
information was developed using interviews with representatives
of two energy companies, literature review, and data analysis. Sufficient information was collected or assumed to utilize all aspects
of the Screening Tool. Because local regulations control the allowed
produced water disposal methods or beneficial uses to an energy
company, an evaluation of relevant Wyoming and New Mexico
regulations (where the case studies take place) was conducted
and a summary is available in the Supporting information (SI).
Screening Tool inputs
Fig. 1. Selected coalbed methane basins in the Rocky Mountain region of the
western US.
The Screening Tool evaluates potential beneficial use projects
using four modules: Water Quality Module (WQM), Treatment
Selection Module (TSM), Beneficial Use Selection Module (BSM),
and Beneficial Use Economic Module (BEM). A description of the
modules is available in the Screening Tool User’s Manual
(CSM/AQWATEC, 2013c), and the flow of data is illustrated in
Fig. 2. Inputs to the WQM include the project location, produced
water quality, and average and peak flow rates from the well field
available for beneficial use. For produced water quality, the user
may input known water quality or use default water quality based
on the location from an extensive produced water quality database
that was developed to support the Screening Tool (CSM/AQWATEC,
2013a; Dahm et al., 2011). Peak flow rate is used by the Screening
Tool to size the treatment influent storage facility, and for the
present case studies, was estimated as a 50% increase of the average flow rate to account for operation of additional wells or wells
at peak (initial) flow. For the Powder River Basin case study, water
quality data available for wells in the region were input to the
WQM (see screenshot of Screening Tool step in Fig. 3), whereas
for the San Juan Basin case study, default water quality available
in the Screening Tool was selected based on project location (see
screenshot in Fig. 4).
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M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
Fig. 2. Flow of information through the four modules of the Screening Tool
(CSM/AQWATEC, 2013c).
In addition to data imported from the WQM, the TSM requires scoring based on the importance determined by the user
for 12 screening criteria (i.e., footprint, energy demand, modularity, capital cost, etc.; see screenshot in Fig. 5 for example),
as well as information on the preferred percent water recovery
for any desalination technologies. The preferable treatment approach for produced water depends on the beneficial use. Several potential beneficial uses may be considered (NRC, 2010;
ALL, 2003, 2006). The Screening Tool groups beneficial uses into
five categories listed in the first column of Table 1, and uses a
set of water quality criteria for key parameters for each of the
five categories. For example, the TDS criterion for Category 2
(crop irrigation) is 5000 mg/L, compared to 500 mg/L for Category 5 (potable use). In addition to the treated water quality
criteria, the influent quality (produced water source) from the
WQM, and the above user-input screening criteria, the TSM selects treatment technologies based on an analysis of over 40
produced water treatment technologies reported previously
(CSM/AQWATEC, 2009).
Inputs to the BSM include data generated by the TSM, information on the anticipated produced water supply duration and
reliability, and the estimated current cost of produced water
disposal ($/barrel (bbl)) for comparison to the beneficial use costs.
Based on these inputs, the BSM estimates treatment costs and
scores project feasibility (more details are provided in
Section ‘Beneficial uses’).
The BEM requires information on the selected overall beneficial
use project, such as land area and infrastructure required, in
addition to the information generated in the WQM, TSM, and
BSM. Based on these inputs, the BEM estimates the overall project
costs. Additionally, the BEM provides a range of the estimated
potential value of the produced water for the selected beneficial
use ($mil/year), as well as estimated environmental and social benefits ($mil/year), to provide further context for the estimated costs.
The value ranges are provided in the tool for each beneficial use
and were based on input from one of the tool developers (Stratus
Consulting) with expertise in water resources valuation (Stratus
Consulting, 2006). An exhaustive presentation of the assumptions
and analysis for determining the value of the water and associated
benefits is outside the scope of this article. The estimated value of
environmental and social benefits are intended to provide a broad
assessment of potential opportunities that may be available to
support the beneficial reuse of produced water.
Many of the case study inputs are presented with the results
below, and more detailed information on the inputs and screen
shots of the module outputs are available online (CSM/AQWATEC,
2013b).
Background on case study locations
Produced water volume and quality
The average water production rate during CBM extraction for
the 1995–2005 period in the Powder River Basin was 2.2 bbl per
thousand cubic feet (MCF) of gas, compared to 0.03 bbl per MCF
Fig. 3. Produced water quality data for Powder River Basin case study (screenshot of WQM output). Notes: Water quality data input from Dahm et al. (2011) or, if no data was
available, from the Screening Tool WQM database.
M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
25
Fig. 4. Produced water quality data for San Juan Basin case study (screenshot of WQM output). Notes: Water quality data input from the Screening Tool WQM database.
Fig. 5. TSM selection criteria user scores for the Powder River Basin case study (screenshot).
Table 1
Potential beneficial uses and preferred treatment trains for the Powder River Basin, Wyoming case study from the Treatment Selection Module (TSM) of the Produced Water
Treatment and Beneficial Use Screening Tool.
Screening tool category beneficial use
Preferred treatment traina
1
2
3
4
No treatment required
Anion IX
Anion IX
Chemical disinfection, media filter, tight NF (brine disposal: deep well injection)
– Livestock watering; impoundments; dust control
– Crop irrigation; non-potable use
– Constructed wetlands
– Surface water discharge/instream flow augmentation;
fisheries
5 – Potable use; aquifer storage and recovery (ASR)
Chemical disinfection, media filter, tight NF, chemical disinfection (brine disposal: deep well
injection)
Anion IX = anion exchange; ASR = aquifer storage and recovery; NF = nanofiltration.
a
Descriptive information for each unit process is available in CSM/AQWATEC (CSM/AQWATEC, 2009).
in the San Juan Basin (Osborne and Adams, 2005), where one bbl is
equal to 42 US gallons (159 L). Based on average data, water
production from San Juan Basin CBM wells is 25 bbl/day per well
(USGS, 2000). The amount of water produced from an individual
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M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
CBM extraction well typically declines over the course of gas production (e.g., approximately 10 years, see Fig. 6). For a group of
wells or a well field, the total water production available for beneficial use depends on management practices such as the timing of
bringing new wells online while others are being shut in or their
water production rate declines. Well spacing ranges approximately
40–80 acres per well in the Powder River Basin (ALL, 2003) and
160–320 acres per well in the San Juan Basin (Bryner, 2002). A produced water supply may be maintained by the operation of new
wells within the well field or nearby.
With respect to water quality, the major constituents of interest
in produced water are the salt content (as total dissolved solids
[TDS] and conductivity), oil and grease, total organic carbon, various inorganic and organic chemicals, and naturally occurring
radioactive material (CSM/AQWATEC, 2013d). The salt content of
produced water can range from as high as 170,000 mg/L TDS,
which is approximately five times the concentration of seawater,
to as low as 200 mg/L TDS, which is below the EPA secondary
drinking water standard (500 mg/L TDS) (NRC, 2010; Rice et al.,
2002; CSM/AQWATEC, 2013d). Compared to CBM produced water
from the Powder River Basin in Wyoming and Montana, produced
water from the San Juan Basin in Colorado and New Mexico is high
in salinity, with TDS concentrations that can sometimes exceed
100,000 mg/L. Therefore, produced water from the San Juan Basin,
without treatment, is expected to exceed water quality standards
for drinking water, agricultural irrigation, and livestock watering
applications (NRC, 2010).
Existing disposal infrastructure
Information on existing produced water disposal practices is
not necessary to run the CBM produced water Screening Tool,
but was reviewed for informational purposes based on case study
interviews and literature review.
In the Powder River Basin, multiple disposal options for produced water may be exercised by a single energy company in a given area (ALL, 2003, 2006). Disposal methods and uses that require
treatment are generally avoided where possible given the cost of
water treatment and the fact that no revenue is typically received
for produced water delivery (e.g., for irrigation and livestock
watering by local ranchers). The primary disposal options in the
state of Wyoming are direct discharge to surface waters with or
without treatment, depending on water quality, injection (such
as into a deep well or using shallow, subsurface drip systems), or
disposal into impoundments, referred to as pits or reservoirs in
Wyoming regulations (NRC, 2010; Wyoming SEO, 2011; WOGCC,
2011; Wyoming DEQ, 2011). A description of the Wyoming CBM
regulatory framework is provided in the SI. Even though stream
discharge may be considered beneficial use (i.e., instream flow
augmentation), operators view it as disposal.
In a typical scenario, an operator will construct a pipeline network to transport water from wells to various disposal routes
and uses, none of which usually produce revenue. The pipelines
are located 6 feet underground and deliver water produced from
a single well, if it is in a geographically remote location, or more
often from a group of nearby wells (e.g., up to 100 wells), to a trunk
line. The produced water discharges are comingled regardless of
water quality, which can vary for different wells. Water is rarely
delivered by gravity and must be pumped. Depending on the distance between clusters of wells and disposal routes, as well as limitations imposed by local land owners or other factors, water may
be transported over distances ranging from less than a mile to
more than 20 miles. Water may be delivered to multiple endpoints
including on or offsite treatment plants if treatment is required for
disposal compliance, to stream discharge, to a deep injection well,
or most commonly, to impoundments.
A typical Powder River Basin operator may manage hundreds
of impoundments near wells and groups of wells ranging in
capacity from less than 1 acre-foot (1233 m3) to up to 100 acrefeet (123,000 m3). Photographs of a produced water aeration
structure (for treatment) and nearby impoundment are provided
in Fig. 7. Impounded water evaporates and infiltrates into the
ground as a means of disposal. Wyoming regulations require
groundwater monitoring beneath the impoundments. From
impoundments, some water may be diverted to beneficial uses
such as irrigation by local ranchers, livestock watering, or on-site
uses (e.g., road dust control, drilling, and enhancing wells). For
untreated irrigation water where water quality is sometimes
unsuitable for ranchers, the produced water may be treated by
gypsum addition to reduce sodium adsorption ratio (SAR) and
salting of the soils.
In contrast to CBM producers in the Powder River and other basins who rely on a combination of multiple disposal options, the
primary disposal option in the San Juan Basin is deep well injection
with minimal treatment (NRC, 2010). A 2002 study indicated that
99.9% of produced water in the San Juan Basin is injected (Bryner,
2002). This is due to the relatively low volumes and high salinity of
produced water in the San Juan Basin. However, deep well injection is a costly disposal method and provides no significant benefit.
Most producers temporarily store the produced water in aboveground storage tanks prior to injection. Treatment by chlorination
is required prior to injection to address bacterial contamination,
Barrels of Produced Water Per Day (bbl/d)
1400
Well 1
1200
Well 2
Well 3
1000
Well 4
Well 5
800
Well 6
600
Well 7
Well 8
400
Well 9
Well 10
200
Mean
0
0
2
4
6
8
10
12
Time (years)
Fig. 6. Mean water production curves (bbl/d) over the life of CBM wells (Powder River Basin case study).
M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
27
Fig. 7. Produced water aeration structures in the Powder River Basin used to remove iron and manganese prior to impoundment.
and filtration is commonly conducted to prevent plugging of the
injection well (NRC, 2010).
Deep injection wells in the San Juan Basin are either companyowned or commercially operated. To transport produced water
from the storage tanks to the injection wells, operators use pipelines or commercial trucking services, depending upon the location
of the well. Aquifer replenishment and enhanced gas recovery may
be ancillary benefits of well injection (NRC, 2010). With respect to
produced water disposal, a description of the New Mexico CBM
regulatory framework is available in the SI.
Hydraulic fracturing
In the course of completing this study, hydraulic fracturing was
identified as a key potential beneficial use of interest for the San
Juan Basin produced water. Hydraulic fracturing is a well stimulation process that uses water to enhance natural gas recovery. Produced water is increasingly recognized as a source water and is
being used for hydraulic fracturing, driven by high produced water
disposal costs coupled with water scarcity (AWI, 2011). Fluids and
sand are injected under pressure into the formation to form fractures and pathways for gas (or oil, in the case of oil production)
to reach the well. Then the gas, fracturing fluids, and produced
water are pumped to the surface (flowback) for recovery and disposal. Estimates of the fluids recovered range from 15% to 80%
(i.e., a portion of the water used for hydraulic fracturing returns
to the surface in the flowback, along with produced water [groundwater]) (AWI, 2011; EPA, 2004).
Hydraulic fracturing is infrequently used in the Powder River
Basin where the natural permeability of the methane-bearing formations is high, but it is commonly used in the San Juan Basin
(NRC, 2010). Each well may require fracturing at multiple depths,
and each fracturing event requires thousands of barrels of water,
depending on the fracturing method used. Required volumes range
from 50,000 to 350,000 gallons in a coalbed formation (EPA, 2004)
to 2–6 million gallons per well in a shale formation (AWI, 2011;
Stewart, 2011; EPA, 2010). Currently, water from the San Juan
and Animas Rivers is used as the base fluid for hydraulic fracturing
in the San Juan Basin (Huang et al., 2005). Alternatively, produced
water from adjacent wells can be beneficially used for fracturing
operations. Produced water volume from a given well will typically
exceed the volume required for hydraulic fracturing of that well,
and thus excess water is available for other beneficial uses or must
be disposed. These other beneficial uses may be considered using
the Screening Tool.
Results and discussion
Powder River Basin, Wyoming
Produced water volume and quality
The Powder River Basin simulated case study focuses on produced water from an assumed group of 400 wells operating in an
80-square mile area in the Wyoming part of the basin. The
assumed well spacing is relatively large at approximately 130 acres
per well. The anticipated life of this well field and associated water
production, in terms of the longevity of the gas resource, is
10–20 years, depending upon the continued development of
additional wells within the well field area.
The produced water volume, quality, and existing disposal
approach utilized for the case study are representative of energy
companies operating in the basin. A mean production curve
(Fig. 6) was developed by averaging produced water quantity data
for ten CBM wells having at least a ten-year history, available from
the Montana Online Oil and Gas Information System for Big Horn
County (DNRC, 2010) located in the Powder River Basin. The production curve is consistent with production behavior described
by energy companies during case study interviews. Operators stagger the initiation of new wells in order to manage and minimize
the total volume and variability of produced water from a well
field, because water production is highest at the early stage of well
production. Additional constraints, such as wildlife-related permitting restrictions, may limit new well construction to certain periods. The case study produced water volume available for
beneficial use from the 400-well field was estimated assuming
the mean well production curve (Fig. 6) and yearly initiation of
new wells according to an assumed permitting schedule over a
20 year period, resulting in an average total water production of
45,000 bbl/d (1.9 MGD; 2120 acre feet per year; 7200 m3/d). This
value was input to the WQM of the Screening Tool.
Average produced water quality utilized for the case study is
provided in Fig. 3 and was based on water quality data for approximately 90 wells in the Powder River Basin in Wyoming (Dahm
et al., 2011). The average TDS concentration of the dataset is
912 mg/L, which is less than the limit for beneficial use for irrigation in Wyoming (2000 mg/L) and for livestock watering (5000 mg/
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M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
L), and would generally be considered fresh water (<1000 mg/L
TDS) (NRC, 2010). The average conductivity and SAR are 1493 lS/
cm and 12.9, respectively. Based on these parameters, the
produced water has a slight to moderate infiltration hazard with
respect to irrigation (Ayers et al., 1985). With respect to stream
discharge, the average conductivity meets standards for the Powder River in Wyoming (Montana DEQ, 2003; based on requirements for downstream Montana), but the average SAR exceeds
the standard and thus the produced water requires treatment prior
to any stream discharge.
Treatment technology
For the Powder River Basin case study, the Screening Tool recommended the treatment trains listed in Table 1 for the five beneficial use categories. No treatment is necessary in this case for
uses such as dust control and livestock watering, but treatment
is recommended for other beneficial use categories. For all categories, product water quality using the recommended treatment
meets the category water quality criteria, with brines ranging from
2400 to 3600 mg/L TDS for an influent quality of 1200 mg/L TDS
(using 75th percentile constituent concentration values for conservative design). Alternative treatment trains are also recommended
by the Screening Tool for each category (not shown), which the
user may choose to carry forward for further beneficial use and
economic evaluation in later modules. The recommended brine
(a high-TDS, concentrated waste stream) disposal method is deep
well injection, which may not require costly well construction if
an injection well is already available to the operator, such as from
previous injection of anion exchange wastewater from produced
water treatment (e.g., EMIT Technologies system (CSM/AQWATEC,
2009)) for disposal compliance.
The water quality criteria used by the TSM are representative of
general requirements for beneficial uses, and therefore may differ
in some cases from site-specific user requirements. With respect
to the Powder River Basin case study, for example, Wyoming regulations specify effluent limitations of 2000 mg/L chloride,
3000 mg/L sulfate, and 5000 mg/L TDS for stream discharge and
water accessible to livestock and/or wildlife (CSM/AQWATEC,
2013e). Additionally, stream discharge to the Powder River must
not exceed a monthly average conductivity of 2000 lS/cm and an
SAR of 5.0 during the irrigation season (NRC, 2010; Wyoming
DEQ, 2003) to protect downstream uses of surface water for irrigation in Montana. However, the influent produced water quality for
the case study already meets the chloride, sulfate, TDS, and conductivity criteria. The TSM-predicted product water quality for
SAR exceeds the regulatory limit, and therefore post-treatment
(SAR adjustment) may be required for beneficial use by stream discharge and crop irrigation. This evaluation demonstrates that for
Table 2
Summary of the Beneficial Use Selection Module (BSM) results for the Powder River Basin case study. Feasibility is scored from
most feasible (5) to least feasible (1).
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M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
site-specific water quality criteria not captured by the Screening
Tool, if any, evaluation of TSM-predicted product water quality
against these criteria will be required.
Beneficial uses
All of the produced water (45,000 bbl/day; 2120 acre feet per
year; 7200 m3/d) from the Powder River Basin well field in the case
study is theoretically available for beneficial use, excluding the volume of any brine produced. While treatment may be used to address water quality requirements, the total water quantity and,
importantly, the anticipated duration and reliability of the supply,
have a significant bearing on the feasibility of beneficial use. For
the Powder River Basin case study BSM inputs, the water quantity
range was 1–5 MGD (3785–19,000 m3/d), the supply timing/reliability was indicated as ‘‘consistent’’ for (at least) 5 years, and
the base flow duration was indicated as (at least) five years. These
inputs were selected based on an anticipated well field life of 10–
20 years, given that 30-year time frames are the next-highest BSM
input choice.
Using this information, the BSM of the Screening Tool scores the
feasibility for each of those three criteria (water quantity, timing/
reliability, and duration), resulting in a net feasibility for each beneficial use. Also estimated are the potential economic value, capital
cost for treatment equipment, and power consumption. The Powder River Basin case study beneficial uses were all at least moderately feasible, as summarized in Table 2. Assumptions that provide
the basis for the feasibility and other scores are provided in graphs
and tables in the Screening Tool. As an example, the score of 3.7 for
potable use was based on equally-weighted scores of 5, 3, and 3 for
water quantity, supply timing/reliability, and duration of supply,
respectively. The weighting can be changed by the user. Water
quantity received a high score based on the Screening Tool
assumption of maximum feasibility when the flow is at least 1
MGD. The supply reliability and duration are moderate (consistent
base flow for at least 5 years); therefore, the Screening Tool assumes a score of 3 for each. These are qualitative assumptions
translated into a quantitative score based on professional
experience and judgment of the tool developers. In this case, large
flow projects are preferable to initiate a potable use project due to
regulatory requirements, public perception, and technical issues.
Though aquifer storage and recovery (ASR) has a relatively high
treatment capital cost (Table 2), it ranked the highest in terms of
project feasibility and highly for potential value, with moderate
power consumption. Potable use and non-potable use screening
results were similar to ASR except for lower project feasibility. Surface water discharge/instream flow augmentation ranked highest
in potential economic value (i.e., to potential downstream users)
with moderate feasibility and power consumption, though at a
high treatment capital cost. Crop irrigation had a fairly high feasibility with some potential value at a low treatment capital cost,
though at a relatively high power consumption. As reported in
the TSM Output, the relatively high power consumption (also for
constructed wetland and non-potable use) is due to the anion exchange unit process in the recommended treatment train for these
beneficial uses.
Project costs assumptions
Project costs beyond the treatment capital costs (output by the
BSM) were explored for beneficial uses of interest using the BEM of
the Screening Tool. For example, land may need to be purchased or
leased, pipelines built, and facilities require operations and maintenance (O&M). Three potential beneficial uses were selected to
carry through to the evaluation in the BSM: ASR, surface water
discharge/instream flow augmentation, and crop irrigation. For
all three projects, the project life is assumed to be 15 years, required land is leased (not purchased or previously owned), and
the local interest rate and energy cost are indicated – all user inputs to the Screening Tool. To estimate costs associated with flow
storage and equalization prior to treatment, a storage volume associated with 60 days of peak flow above design capacity was selected. Staff number and control system assumptions were also
input. For ASR, percolation ponds (rather than injection wells)
were selected as the new infrastructure with a project area of
approximately 70 acres (based on an estimate available from the
Screening Tool). For surface water discharge and crop irrigation
projects, a project area of 1-acre (for delivery pipeline and
discharge facility to the stream) and 0-acres (assume land is owned
by rancher), respectively, was assumed. The associated new infrastructure was a discharge facility for surface water discharge, and
retrofits to existing irrigation systems for crop irrigation. The
Table 3
Comparison of three potential project scenarios (beneficial uses) and cost estimates for the Powder River Basin case study from the Beneficial Use Economic Module (BEM).
a
b
[Input] or Output
Units
Beneficial Use Economic Module, project scenarios
[Project name]
–
Percolation ponds
[Location]
–
City A, Wyoming, Powder River Basin
Surface water discharge
Crop irrigation
[Beneficial use]
–
Aquifer Recharge, Storage and Recovery
Surface Water Discharge/ Instream Flow Augmentation
Crop irrigation
Treatment traina
–
Filter-NF-Re-inject
Filter-NF-Re-inject
Anion IX
[Water quantity (design flow)]
mgd
gpm
bbl/day
1.9
1300
45,000
1.9
1300
45,000
1.9
1300
45,000
[Project life]
years
15
15
15
[Interest rate]
%
5%
5%
5%
Estimated project capital cost total
$ million
45
35
30
Annualized capital costs
$mil/year
4.0
3.1
2.5
Annual O&M costs
$mil/year
1.8
1.1
2.1
Total annualized costs
$mil/year
avg $/bblb
5.8
0.35
4.2
0.26
4.5
0.27
Estimated value of produced water
for selected beneficial use
$mil/year
$3.4–$10
$3.8–$15.4
$0.3–$3.1
Estimated environmental benefits
$mil/year
n/a
$0.2–$1.24
n/a
Estimated social benefits
$mil/year
$0.03–$3.94
$0.03–$3.94
$0.07–$3.59
For complete treatment train, see Table 1.
Based on design flow.
30
M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
estimated conveyance distance for pipeline construction was five
miles between the produced water source (collected from the well
field using existing water management infrastructure) and the project area for ASR and surface water discharge (e.g., percolation
ponds, stream) and 15 miles for crop irrigation.
Screening-level estimated project costs
A summary of the project costs is presented in Table 3.
Compared to disposal costs for produced water, the results indicate
that beneficial use can be economically competitive. If revenue is
received for the beneficial use, then the comparison becomes
increasingly favorable. The BEM results indicate that the total estimated annualized costs, which include the cost of the treatment
technology and additional costs associated with the beneficial
use project, are $4.2 million per year ($0.26/bbl) for surface water
discharge, $4.5 million per year ($0.27/bbl) for crop irrigation, and
$5.8 million per year ($0.35/bbl) for ASR. The per-barrel estimates
refer to barrels of raw produced water. These low costs may reflect
the relatively high quality of CBM produced water in the Powder
River Basin.
For comparison to these costs of beneficial use, a range of costs
for produced water disposal is reported by operators in the Powder
River Basin. There is no one ‘‘typical’’ disposal cost per barrel that is
representative of all sites. Based on interviews conducted in 2000–
2001 for the area, reported costs range from $0.01/bbl (for utilizing
a pipeline collection system with impoundment discharge), $0.20/
bbl (for pumping to an injection system), to $2/bbl (for hiring a
commercial water hauling service). Estimated values may not take
into account full costs such as weed control for pit maintenance
(Boysen et al., 2002), environmental compliance monitoring, company truck fuel, and chemicals for corrosion and scale control at
injection wells. Approximately 15–18% of produced water in the
Powder River Basin is treated to address SAR and conductivity for
NPDES-permitted discharge, at reported treatment costs of approximately $0.12 to $0.60/bbl (NRC, 2010). In this way, the Screening
Tool may be used to perform a screening-level cost estimate for a
particular site to determine whether the costs per barrel for beneficial use are more or less than site-specific disposal costs. Potential
value of the beneficial use may also be considered (Table 3), which
could significantly offset or even exceed the beneficial use project
costs if realized by seeking revenue or project cost sharing for providing the high quality water to a user.
San Juan Basin, New Mexico
Produced water volume and quality
For the San Juan Basin simulated case study, an area of approximately 550 square miles was assumed to contain over 1500 wells,
with continual development of new wells via increasing well
density and development in new areas. At rates typical for the
San Juan Basin, the total water production for the case study is
approximately 37,500 bbl/day, or 1.6 MGD (1800 acre feet per
year; 6056 m3/d).
Default water quality data available in the Screening Tool was
used for the San Juan Basin produced water quality (Fig. 4). The default San Juan Basin TDS concentration for the Fruitland Formation
is approximately 8000 mg/L. The SAR is also relatively high at 81.
Some organic contaminants (e.g., benzene, xylenes) are present
at low concentrations.
Treatment technology
For the San Juan Basin case study, the Screening Tool recommended the treatment trains listed in Table 4 for the five beneficial
use categories, based on user-input criteria and default influent
(produced water source) quality. The default water quality is
determined from an extensive database that was constructed to
support the Screening Tool, as described in Section ‘Screening Tool
inputs’. The Screening Tool provides estimates of the treated water
and brine water quality, capital costs, power consumption, equipment life, and brine volume produced from each of the treatment
trains. For four of the five beneficial use categories, the Screening
Tool recommended treatment involving an artificial wetland and
thermal distillation (among other unit processes, Table 4). The similarity of recommended treatment trains is driven by the influent
water quality and user-input selection criteria (weighted preferences). Thermal distillation is recommended over membrane treatment (nanofiltration, NF) due to the high TDS of the feed water. In
practice, an engineer may prefer NF/reverse osmosis (RO) followed
by brine distillation for these beneficial use categories. Recognizing
certain limitations of the existing Screening Tool, the next version
(currently under development) will allow the user to define a
treatment technology process (such as by excluding or including
specific processes).
For the San Juan Basin case study, percent recovery was set as
85%, as this higher recovery resulted in a lower cost due to the
decreased brine volume. The TSM provides the anticipated product
water and brine quality for each treatment train/beneficial use
category. With respect to the brine produced from thermal distillation, the TSM indicated a brine concentration and flow rate of
approximately 54,000 mg/L TDS and 5600 bbl/day, respectively
(for 85% recovery). The daily brine volume is larger if the combined
waste streams from other unit treatment processes in the treatment
train are considered (resulting in 10,000–14,000 bbl/day total for
the San Juan Basin case study, depending on the treatment train).
In the course of completing this study, hydraulic fracturing was
identified as a key potential beneficial use of interest for the San
Juan Basin. Water quality requirements for the base water used
in hydraulic fracturing vary depending upon the operator and their
site-specific hydraulic fracturing chemistry (i.e., proprietary
chemicals that will be added to the base water), as well as local
regulations. When river or ground water is used as the base fluid,
disinfection and low levels of organics, TDS (e.g., 500 mg/L),
Table 4
Potential beneficial uses and preferred treatment trains for the San Juan Basin, New Mexico case study from the Treatment Selection Module (TSM).
Screening Tool category beneficial use
Preferred treatment traina
1 – Livestock watering impoundments; dust
control
2 – Crop irrigation; non-potable use
Wetland, UV disinfection, media filter, acid cation IX (H), GAC, thermal distillation (Brine disposal: evaporation
ponds)
Wetland UV disinfection media filter, acid cation IX (H), GAC, thermal distillation (Brine disposal: evaporation
ponds)
Wetland UV disinfection media filter, acid cation IX (H), GAC, thermal distillation (Brine disposal: evaporation ponds
Wetland, UV disinfection, media filter, acid cation IX (H), GAC, thermal distillation (Brine disposal: evaporation
ponds)
UV disinfection, chemical softening coagulation, media filter, acid cation IX (H), thermal distillation, chemical
disinfestion (Brine disposal: evaporation ponds
3 – Constructed wetlands
4 – Surface water discharge/instream flow
augmentation, fisheries
5 – Potable use; ASR
Acid cation IX = acid cation exchange; ASR = aquifer storage and recovery; GAC = granular activated carbon; UV = ultraviolet.
a
Descriptive information for each unit process is available in CSM/AQWATEC (CSM/AQWATEC, 2009).
M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
31
Table 5
Summary of the Beneficial Use Selection Module (BSM) results for the San Juan Basin case study. Feasibility is scored from most
feasible (5) to least feasible (1).
naturally occurring radionuclides (NORM), and barium or sulfate
are typically required (Stewart, 2011). However, new chemical
additives for hydraulic fracturing allow the use of higher TDS
water. This provision will be incorporated into the next version
of the Screening Tool. The current version of the Screening Tool
does not explicitly consider hydraulic fracturing as a type of beneficial use, and therefore does not score its feasibility in the BSM
(i.e., Table 5, next section) nor provide project cost estimates for
any necessary (non-treatment) infrastructure in the BEM. Nevertheless, the Screening Tool was valuable to assess potential treatment technologies and costs for this beneficial use by
conservatively assuming that water quality criteria for hydraulic
fracturing are similar to potable use criteria. Therefore, the treatment train recommended for potable use (Table 4) was assumed
to also be appropriate for hydraulic fracturing. Depending on the
operator, potable use criteria may be too stringent for hydraulic
fracturing; however, it represented a conservative choice for this
exercise. The next version of the Screening Tool (currently under
development) will accommodate additional beneficial uses and allow the user to define the target water quality for a specific beneficial use. In the meantime, users may select the beneficial use
category having water quality criteria (which are indicated in the
tool) most similar to their site-specific requirements.
Beneficial uses
For the San Juan Basin case study BSM inputs, the water
quantity range was 1–5 MGD, the supply timing/reliability was
indicated as ‘‘consistent’’ for (at least) 30 years, and the base flow
duration was indicated as (at least) 30 years. The reliability and
duration were based on an anticipated produced water supply life
of 15–20 years, or perhaps as long as 30 years depending on
continued development.
As described in the Powder River Basin case study, the BSM uses
this information to determine a net project feasibility, as well as
potential economic value, capital cost for treatment equipment,
and power consumption for five categories of beneficial use. The
case study beneficial uses were all characterized as highly feasible,
as summarized in Table 5, given that the water quantity is large,
the supply reliability is high, and the duration is long-term. All categories had similar capital costs and energy requirements associated with treatment due to the similar treatment trains
recommended.
Project costs assumptions
For the San Juan Basin case study, surface water discharge/instream augmentation use and hydraulic fracturing were selected
as the beneficial uses of interest for further evaluation and project
32
M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
Table 6
Potential project scenarios and cost estimates for the San Juan Basin case study from the Beneficial Use Economic Module (BEM).
[Input] or Output
Units
Beneficial use economic module, project scenarios
[Project name]
–
Surface water discharge
[Location]
–
City B, New Mexico, San Juan Basin
–
Surface water discharge/instream flow augmentation See footnotea
[Beneficial use]
Treatment train
b
Hydraulic fracturing
–
Filter-IX-GAC-Thermal Distillation-Evap
Filter-IX-Thermal Distillation-Evap
[Water quantity (design flow)]
mgd
gpm
bbl/day
1.6
1,100
37,000
1.6
1,100
37,000
[Project life]
years
20
20
[Interest rate]
%
5%
5%
Estimated project capital cost total
$ million
65
51
Annualized capital costs
$mil/year
5.1
4.0
Annual O&M costs
$mil/year
5.0
4.5
Total annualized costs
$mil/year 10.1
avg $/bbl 0.75
8.5
0.63
Estimated value of produced water for selected beneficial use $mil/year
$3.1–$12.7
NAc
Estimated Environmental Benefits
$mil/year
$0.16–$1.02
NAc
Estimated Social Benefits
$mil/year
$0.03–$3.24
NAc
a
Hydraulic fracturing is not a category of beneficial use that is explicitly considered by the Screening Tool. ‘‘Potable Use’’ was selected for beneficial use category because
the water quality criteria employed by the tool for this use are most similar to hydraulic fracturing criteria (driven by relatively low TDS criteria) compared to other Screening
Tool beneficial use categories.
b
For complete treatment train, see Table 4.
c
Related to footnote ‘a’, estimated potential values predicted by the BEM are specific to the beneficial use category, and therefore in this case the values generated relate to
potable use not hydraulic fracturing.
cost assessment in the BEM of the Screening Tool. Surface water
discharge may be of particular interest to some Screening Tool
users for the potential marketing of treated water via surface water
discharge to downstream users. As described previously, hydraulic
fracturing is particularly relevant to the San Juan Basin region.
For surface water discharge, project inputs used to determine
overall project costs included one acre leased from the Bureau of
Land Management (BLM) for the treatment plant and construction
of the discharge facility to the river (which was selected as required new infrastructure). The conveyance distance from treatment to the discharge location was estimated to be 10 miles. For
hydraulic fracturing, the ‘‘potable use’’ beneficial use category
was used to represent hydraulic fracturing for the purposes of
treatment technology selection (as described in Section ‘Treatment
technology’), which automatically carries through to the BEM. The
resulting BEM project cost estimate is considered applicable because potable use-related infrastructure (e.g., pipelines, connection
to potable system) was indicated as not necessary via menu options in the BEM. This left an estimated project cost based solely
on treatment costs and 1-acre land area, plus facility, overhead,
and contingency costs. This is acceptable because hydraulic fracturing is an on-site activity already conducted using an alternate
water source and previously established infrastructure, and therefore additional land and infrastructure are not likely to be required
to employ use of produced water for this beneficial use other than
the treatment technology. For both projects, the project life was
estimated to be 20 years, local interest rates and energy costs were
assumed, and a storage pond with adequate volume for 14 days of
peak flow above design capacity was selected (for flow storage and
equalization prior to treatment).
Screening-level estimated project costs
A summary of the project costs is presented in Table 6.
Compared to disposal costs for produced water, the results indicate
that beneficial use can be economically competitive in the San Juan
Basin. If revenue is received for the beneficial use, then the
comparison becomes increasingly favorable. BEM results indicate
that the total estimated annualized costs, which include the
cost of the treatment technology and any additional costs associated with the beneficial use project are $10 million per year
($0.75/bbl) for surface water discharge and $8.5 million per year
($0.63/bbl) for hydraulic fracturing. These costs are comparable
to deep well injection costs for disposal of produced water in the
San Juan Basin, which is site-specific and averages $1 to $4 per
barrel. Produced water disposal costs per barrel tend to be higher
for commercially operated wells and/or if commercial trucking
services are used (Huang et al., 2005; Boysen et al., 2002). Screening Tool users estimating project costs for use of produced water
for hydraulic fracturing will also be interested in comparing the
costs to their existing (site-specific) costs for using other sources
of water.
The results of the BEM indicate that the potential beneficial use
projects may be less costly than the current disposal method in the
San Juan Basin. Additionally, for hydraulic fracturing, these costs
would replace the current costs of transporting the alternate water
source (e.g., San Juan River water). With respect to stream discharge, the potential economic value (Table 6) could significantly
offset or even exceed the beneficial use project costs.
Conclusions
Management and disposal of produced water, typically via deep
well injection or treatment and discharge, represents an operational challenge and a major cost for energy companies. The case
studies developed using the Produced Water Treatment and Beneficial Use Screening Tool were based on realistic conditions and
assumptions for the Powder River and San Juan Basins at the time
of the study, and demonstrated the feasibility of various beneficial
uses of produced water. Treatment technologies are available to
treat the produced water to the level of quality required for the
beneficial use, at an overall project cost that may be comparable
to or less than the existing disposal cost.
Further, costs associated with beneficial use may be offset by
potential value, if realized by seeking revenue for provision of
M.H. Plumlee et al. / Journal of Unconventional Oil and Gas Resources 5 (2014) 22–34
the high quality treated produced water. This may be achievable
given the high demand for water and its economic value in the arid
western United States. Example uses include local crop irrigation
and livestock watering, or indirect potable uses such as via ASR.
There are a few known cases in which produced water from oil
and gas activity was marketed and used for potable supplies
(NRC, 2010; Stewart and Takaichi, 2007; Stewart, 2006). Costs
may be offset by on-site use as well, such as for hydraulic fracturing. Unlike livestock watering, irrigation, and nearby potable users,
hydraulic fracturing and other on-site uses are not limited by the
proximity of a potential user to the produced water source and
do not require coordination between the energy company and another party. Water transfer to downstream users via stream discharge is also not limited by the proximity of the user. A
theoretical example is produced water discharged to rivers upstream of reservoirs used for potable water supply. Produced water
from the Powder River Basin is discharged to rivers upstream of
reservoirs and therefore has indirectly augmented these reservoirs
(ALL, 2006), though it has not been marketed or discharged directly
for this purpose.
The next version of the Screening Tool (currently under development) will accommodate additional beneficial uses and allow
the user to define the target water quality for a specific beneficial
use. Additionally, it will allow the user to define a treatment technology process and exclude or include specific processes, if desired.
The first update of the Screening Tool is estimated to be available
by the end of 2014.
While the Screening Tool case studies demonstrate the technical and economic feasibility of beneficial use of produced water,
which is increasingly recognized, there remain institutional and legal challenges, particularly with respect to water rights, water
marketing, and transfer. As an example, interstate water marketing
in the Colorado River Basin is discussed further in the SI. The oil
and gas industry’s unfamiliarity with the water industry, and vice
versa, represents a key challenge (Stewart and Takaichi, 2007).
Examples of other non-technical barriers to implementation of
beneficial use have been summarized in previous publications
(NRC, 2010; ALL, 2006).
The high demand and value of water, availability of cost-effective treatment technologies, and potential cost savings to energy
companies provide the incentives to address these challenges.
Technical and economic assessments like the presented case studies and some example projects (e.g., Stewart and Takaichi, 2007)
have taken steps forward to demonstrate feasibility.
Acknowledgments
The authors thank the Ultra-Deepwater and Unconventional
Natural Gas and Other Petroleum Resources Research and Development Program for funding the project (Grant #07122-12) as part of
the Research Partnership to Secure Energy for America program
administered by the US Department of Energy’s National Energy
Technology Laboratory. The authors also thank the regional participating CBM producers for their technical assistance, support, and
contributions of water quality and quantity data, and thank the
technical advisors of the study: David Stewart, John Veil, and
Wayne Buschmann.
Appendix A. Supplementary data
Supporting information associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.juogr.2013.12.002.
33
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