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Wastewater Disposal from Unconventional Oil and Gas Development Degrades Stream Quality at a West Virginia Injection Facility Denise M. Akob, Adam C. Mumford, William H Orem, Mark A. Engle, J. Grace Klinges, Douglas B. Kent, and Isabelle M. Cozzarelli Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b00428 • Publication Date (Web): 09 May 2016 Downloaded from http://pubs.acs.org on May 11, 2016
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Environmental Science & Technology
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Wastewater Disposal from Unconventional Oil and Gas Development Degrades
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Stream Quality at a West Virginia Injection Facility
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Denise M. Akob1,*, Adam C. Mumford1, William Orem2, Mark A. Engle2, J. Grace
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Klinges1,#, Douglas B. Kent3, and Isabelle M. Cozzarelli1
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U.S. Geological Survey, National Research Program, Reston, VA 20192 USA
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U.S. Geological Survey, Eastern Energy Resources Science Center, Reston, VA
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20192 USA 3
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U.S. Geological Survey, National Research Program, Menlo Park, CA 94025 US
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*Corresponding Author: Dr. Denise M. Akob, U.S. Geological Survey, National
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Research Program, 12201 Sunrise Valley Dr., MS 430, Reston, VA 20192 USA, Phone:
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703-648-5819, Fax: 703-648-5484, Email:
[email protected] 16
#
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Superfund Remediation and Technology Innovation, Science Policy Branch
Present address: ORISE Fellow, U.S. Environmental Protection Agency, Office of
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Keywords: unconventional oil and gas production, wastewaters, class II injection, shale
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gas production, Marcellus Shale, produced water
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Abstract
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The development of unconventional oil and gas (UOG) resources has rapidly
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increased in recent years; however, the environmental impacts and risks are poorly
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understood. A single well can generate millions of liters of wastewater, representing a
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mixture of formation brine and injected hydraulic fracturing fluids. One of the most
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common methods for wastewater disposal is underground injection; we are assessing
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potential risks of this method through an intensive, interdisciplinary study at an injection
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disposal facility in West Virginia. In June 2014, waters collected downstream from the
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site had elevated specific conductance (416 µS/cm) and Na, Cl, Ba, Br, Sr and Li
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concentrations, compared to upstream, background waters (conductivity, 74 µS/cm).
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Elevated TDS, a marker of UOG wastewater, provided an early indication of impacts in
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the stream. Wastewater inputs are also evident by changes in 87Sr/86Sr in stream water
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adjacent to the disposal facility. Sediments downstream from the facility were enriched
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in Ra and had high bioavailable Fe(III) concentrations relative to upstream sediments.
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Microbial communities in downstream sediments had lower diversity and shifts in
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composition. Although the hydrologic pathways were not able to be assessed, these
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data provide evidence demonstrating that activities at the disposal facility are impacting
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a nearby stream and altering the biogeochemistry of nearby ecosystems.
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Introduction Increasing demand for fossil fuels and depletion of traditional oil and gas
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reservoirs has driven the development of shale gas, coal-bed methane (CBM), and
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other unconventional oil and gas (UOG) resources using technologies such as
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directional drilling and hydraulic fracturing e.g., 1. These resources are an important part
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of the United States’ energy resource portfolio. While CBM production is estimated to
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remain at current levels of national gas production (8%), development of shale gas is
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estimated to account for at least 50% of all natural gas produced in the U.S. by 2040.2
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Production of UOG resources results in liquid (e.g., produced waters or wastewaters),
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solid (e.g., drill cuttings), and gaseous wastes, which pose unknown risks and potential
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consequences to the quality of atmospheric, groundwater, surface-water, soil, and
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environmental resources.
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Wastewaters from UOG production are mixtures of residual fluids used to
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complete the well and formation brine.1, 3-7 Initially these wastewaters reflect the
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composition of the injected fluid, then over time, the chemistry shifts to reflect the
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chemical composition of the formation, e.g., 5. Wastewaters from the Marcellus Shale
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typically have elevated total dissolved solids (TDS, up to 300,000 mg/L),5, 8-10 variable
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concentrations of organic compounds,6, 11 and naturally occurring radioactive material
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(NORM12). An average well producing from the Marcellus Shale yields approximately 5
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million liters of wastewater over its lifetime; these large volumes of returned fluids, with
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complex chemistries, present water management challenges. The chemistry can affect
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the suitability of wastewaters for reuse or the strategy for disposal.3, 4, 13, 14
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UOG wastewaters are managed in a variety of ways including treatment and re-
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use for new well completions,15 disposal through publicly owned or commercial
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wastewater treatment plants,14, 15 or disposal in Class II underground injection control
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(UIC) wells.4, 14, 15 Class II disposal wells are estimated to be disposing of over 2 billion
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gallons of wastewater from oil and gas operations every day.16 They are located across
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the United States and there are approximately 36,000 Class II UIC wells handling
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wastewaters from UOG operations.16 Impacts on environmental health from accidental
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or intentional releases during handling, disposal, treatment, or re-use are poorly
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documented, with few reports in the literature.17 Potential pathways for wastewater to
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enter surface water or groundwater include: (1) releases from pipelines or tanker trucks
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transporting fluids, (2) leakage from wastewater storage ponds through compromised
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liners and overflows from the ponds, or (3) migration of the fluids through the
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subsurface at the injection depth or through failed injection well casings. Research is
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needed to examine the potential impacts of wastewater releases on environmental
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health, which are likely to accelerate with the growing pace of UOG development.
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Near Lochgelly, West Virginia, wastewaters from UOG development are
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disposed of in a Class II UIC well. A small stream runs through the facility and provides
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an opportunity to sample surface water and sediments near a wastewater disposal
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operation (Fig. 1). This study is a part of a larger effort by the US Geological Survey
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(USGS) and university researchers to quantify biogeochemical and human health
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changes resulting from UOG wastewater disposal.18 Here, we used key field and
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inorganic chemical signatures, as well as microbial community compositions, to identify
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UOG wastewater impacts to stream biogeochemistry by characterizing differences
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between sites within the disposal facility and background sites located upstream or in a
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separate drainage with no known inputs from oil and gas development. Although the
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pathway of contaminants from the disposal facility to the stream could not be assessed,
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these results clearly demonstrate that wastewater handling practices at the site affect
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stream and sediment quality.
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Materials and Methods Site Description. The study area is located near a UOG wastewater UIC facility
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(disposal facility) in central West Virginia (Fig. 1 and S10). The disposal well was
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originally drilled in 1981 as a natural gas production well to a depth of 990.6 m. The well
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was reworked as a Class II injection well in 2002, with fluids injected into a sandstone
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reservoir at a depth of 792.5 m. In addition to the disposal well, the facility has brine
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storage tanks, an access road, and two small, lined impoundment ponds. Until the
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spring 2014, a portion of the wastewaters were temporarily stored in the holding ponds
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prior to injection to allow for settling of particulates that could potentially clog the pore
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space in the receiving reservoir. The ponds operated from 2002 to spring 2014 when
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they were removed and the area re-contoured and planted with grass.
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A certified record inventory for the site was obtained from the West Virginia
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Environmental Quality Board (WVEQB), which provided API numbers for 25 wells
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shipping wastewaters to the facility. Between 2002 and 2014 the UIC well injected
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approximately 1.5 million barrels (equal to ~178 million liters) of wastewater from the 25
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production wells located in West Virginia. Information about these production wells was
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obtained from the West Virginia Department of Environmental Protection (WVDEP),
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Office of Oil and Gas permit database ((http://tagis.dep.wv.gov/oog/) as detailed in
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Table S1. All of the wells are producing natural gas, with 15 wells producing coal bed
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methane, while four wells are producing from the Marcellus Shale. An additional 4 wells
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are characterized as horizontal gas wells producing from the Lower Huron shale
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formation (Lower Huron is WVDEP nomenclature, USGS usage is Huron Member of the
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Ohio Shale). We were unable to find records for the remaining two wells listed in the
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WVEQB document.
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The Wolf Creek watershed encompasses 4430 hectares with Wolf Creek flowing
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to the northeast and joining the New River ~10 km downstream from the facility (Fig.
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S10). The New River is used for recreation and is a local drinking-water source. The
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headwaters of Wolf Creek flow through areas of past surface coal mining that have
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since been covered or reclaimed and are primarily residential or agricultural land.19
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Despite reclamation, Wolf Creek was classified as biologically impaired by the WVDEP
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in 2008, due to high levels of iron and dissolved aluminum,20 which may be due to acid
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mine drainage from the Summerlee coal mine.21
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An initial reconnaissance-sampling trip conducted in September 2013 indicated
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potential impacts to the headwaters requiring additional investigation (Table 1, Fig. 1).
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To further study impacts from the disposal facility, samples were collected from two
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control locations within the Wolf Creek watershed: 1) a small tributary that runs through
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the disposal facility and 2) a separate drainage (referred to as “background drainage”),
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Site 2, with no potential impact from the disposal facility (Fig. 1A, Table 1). The tributary
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begins upstream from the disposal facility and runs adjacent to the disposal well, and
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downhill from the two former impoundments (Fig. 1B). The background drainage-stream
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meets the disposal-facility-stream prior to joining the main stem of Wolf Creek, ~ 1,000
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m downstream from the facility (Fig. 1A). No samples were obtained for the current
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study below Site 3 due to other industrial activities in the area (e.g., an automotive
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junkyard).
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Site Sampling and Analysis. The disposal facility and background drainage
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streams (Site 2) were sampled in June 2014 at five points within the disposal facility,
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including locations upstream (Site 4), within (Site 5 and 6), and downstream (Sites 7
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and 3) from the disposal facility (Fig. 1B, Table 1). Conductivity, pH, and aqueous Fe2+
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were determined in the field as described in the SI Methods. Water samples were
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collected from the approximate center of the stream for analysis of alkalinity, cations,
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anions, strontium (Sr), oxygen (O) and hydrogen (H) isotopes, nonvolatile dissolved
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organic carbon (NVDOC), trace inorganic elements, and disinfection byproducts (DBP)
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as described in the SI Methods. Additional field measurements and water samples for
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NVDOC and major and minor cations were collected in September 2013 and 2014 at
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Sites 2, 7, and 3. Streambed sediment samples were collected for carbon, nitrogen and
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sulfur elemental analysis (CNS), Fe speciation, total inorganic elements, and microbial
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community analysis as described in the SI Methods. Detailed sampling, quality
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assurance/quality control (QA/QC) procedures, and analytical methods are described in
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the SI Methods. No hydrologic measurements were conducted or groundwater sampled
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during the September and June sampling efforts. Further investigations into the
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hydrology of the site were not possible due to site access limitations. The microbial
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community sequence dataset was deposited in the National Center for Biotechnology
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Information (NCBI) Sequence Read Archive (SRA) under accession number
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SRP073303.
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Results and Discussion Impacts to Stream Water Quality. Tributaries of Wolf Creek that were sampled
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in September 2013, June 2014, and September 2014 showed impacts on the tributary
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downstream from the injection disposal facility (Fig. 1, Table 1). In September 2013
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exploratory sampling indicated that there was elevated specific conductance at Sites 7
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and 3 compared to the background drainage Site 2 (Table 1). Intensive sampling in
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June 2014 revealed that background sites located in the separate drainage (Site 2) or
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upstream (Site 4), with no known UOG wastewater inputs, exhibited no visual signs of
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impacts or disturbance due to anthropogenic activity. Waters at these sites had neutral
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pH and specific conductance (~80 µS/cm, Table 1) in line with that of minimally
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impacted streams in the area. Sites 5, 6, 7 and 3, which were located on, adjacent to
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the disposal injection well, adjacent to the former holding ponds, or downstream,
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respectively, all exhibited visual signs of impacts. All 4 of these sites had red-orange
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sediments and waters characterized by neutral pH (Table 1). At Sites 6, 7, and 3 there
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were hydrocarbon odors once the sediment was disturbed, although Site 6 waters had a
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specific conductance in line with background sites and Site 5. Waters from sites
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downstream from the former impoundments (Sites 7 and 3) had elevated specific
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conductance (~400 µS/cm) indicating that visual impacts at these sites were associated
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with alterations to the stream chemistry. The elevated specific conductance provided
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the field evidence that impacts to the stream are due to UOG wastewaters, because
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produced waters from both conventional and unconventional oil and gas wells in the
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Appalachian Basin are characterized by high salinity.5, 6, 10, 22-26 Specific conductance at
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all of the sites was lowest at the June 2014 sampling time point, likely due to the fact
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that 3.0 cm of precipitation fell in 24 hours on June 12, 2014 in nearby Beckley, WV,27
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less than one week prior to our sampling on June 17, 2014.
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Water samples collected in June 2014 showed clear differences in chemistry
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upgradient and downgradient from the waste-disposal facility (Fig. 3 and Table S2).
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Streams in this region are naturally low in NVDOC; below 1.5 mg/L at both background
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sites at the time of sampling (Fig. 3a, Table S2). Concentrations increased to 2.2-3.3
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mg/L at sites on and downgradient from the facility. In contrast, nitrate (NO3-) and
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sulfate (SO42-) concentrations in the stream decreased on and below the disposal
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facility. Total Fe concentrations adjacent to the former impoundments were 8.1 mg/L, far
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in excess of the 0.13 mg/L found upstream from the facility (Table S2).
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Chloride (Cl-, 115 mg/L) and bromide (Br-, 0.80 mg/L) concentrations were
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elevated adjacent to the former impoundments (Site 7), compared to 0.88 mg/L Cl- and
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0.713), than the samples on or below the
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disposal facility suggesting contribution from additional sources of water into the stream.
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Because Sr isotopes do not fractionate appreciably in the environment, sources of Sr-
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rich water with a lower 87Sr/86Sr ratio appear to contribute to the stream near Site 6 and
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again below the disposal facility (Sites 3 and 7). For context, these data are compared
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against late stage produced waters from the Marcellus Shale from Greene County,
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Pennsylvania and mine drainage water from the various Pennsylvanian age coals in the
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area (external Sr data from 44). There is some spatial variability in strontium isotope
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geochemistry across the Marcellus Shale, so data from the closest county (Greene)
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were used. On this type of plot (87Sr/86Sr vs. 1/Sr), mixtures between any two end-
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members plot as straight lines (Fig. 4a). The data point for the Site 6 sample falls along
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a mixing line between upstream water (Site 4) and Marcellus Shale produced waters.
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End-member mixing calculations suggest the sample from Site 6 is the result of a small
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contribution of Marcellus Shale produced waters (0.004%). Such small contributions can
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be identified because of the high concentration of Sr in Marcellus Shale produced water
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(>1500 mg/L) relative to the stream water (
