Feasibility of Using Brackish Groundwater Desalination Concentrate ...

Shale Energy Engineering 2014 ©ASCE 2014

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Feasibility of Using Brackish Groundwater Desalination Concentrate as Hydraulic Fracturing Fluid in the Eagle Ford Shale Nima Ghahremani1 and Lee Clapp2, Ph.D., P.E. 1

Doctoral Candidate, Texas A&M University-Kingsville, Department of Environmental Engineering, 917 W. Avenue B, Kingsville, TX, 78363, U.S.A., [email protected]. 2 Associate Professor, Texas A&M University-Kingsville, Department of Environmental Engineering, 917 W. Avenue B, Kingsville, TX, 78363, U.S.A., [email protected].

ABSTRACT: Recent estimates predict over 20,000 wells will be drilled for hydraulic fracturing in the Eagle Ford Shale over the next 15 years, accounting for approximately 5-7% of the total water use within the main 16-county area, and as high as 89% in one rural county. Since each well requires about 10000-25000 m3 of water, there is significant concern about fresh water consumption in drought-stricken South Texas. Hence, development of the Eagle Ford Shale will require water management strategies that maximize use of non-potable water. The main objective of this study is to evaluate the feasibility of using reject concentrate streams from groundwater RO desalination plants located within the Eagle Ford Shale region as hydraulic fracturing fluid. This could have two synergistic advantages: (1) elimination of brackish desalination concentrate discharges to surface waters, and (2) provision of a source of water for the oil and gas industry that does not consume freshwater supplies. This study will perform comprehensive chemical characterization of both an RO reject concentrate stream and hydraulic fracturing flowback water, and also will perform a geochemical modeling analysis to assess the down-hole scaling potential associated with the RO concentrate if used as hydraulic fracturing fluid in the Eagle Ford. BACKGROUND Fresh Water Use for Hydraulic Fracturing in Eagle Ford Natural gas production in the Eagle Ford Shale is projected to last well past 2050, and natural gas will replace coal as the largest source of U.S. electricity by 2040, contributing to energy-related carbon emissions in the U.S. remaining below 2005 levels through 2040 (U.S. EIA, 2013).Water is a key factor in the development of the oil and gas industry in Texas. For example, recent estimates predict that over the next 15 years between 20,000 and 30,000 wells will be drilled for hydraulic fracturing in the Eagle Ford Shale, and that each of these wells will require 10000-25000 m3 of water. Overall, it is estimated that the water utilization for development of the Eagle Ford

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Shale will account for approximately 5-7% of the total water use (including agricultural, industrial, and municipal) within the main 16-county area (Jester, 2011). Unfortunately, the Eagle Ford Shale boom has coincided with severe drought in Texas. For example, 2010-2011 was the most intense one-year drought in Texas since at least 1985 when statewide weather records began (Nielsen-Gammon, 2011). Thousands of Texas farmers, including those in Matagorda County, did not receive water for irrigation this year because lakes and rivers remain low after more than a year of drought (Washington Post, 2012). A recent study determined that if Texas were to experience drought of record conditions, available sources of fresh water would not meet residential, industrial and agricultural demands (Ward, 2011). Of 11,634 shale wells in Texas in 2013, 5,891 (51%) were in high or extremely high water stress areas (“extremely high water stress” means over 80 percent of available water is already being withdrawn for municipal, industrial and agricultural purposes) (Freyman and Salmon, 2013). It is thus not surprising that the Texas legislature is pursuing measures such as mandatory flowback water recycling requirements (Boman, 2013), while the Texas Railroad Commission recently changed permitting requirements to make it easier to treat and recycle flowback water (TRC, 2013). Although hydraulic fracturing operations have been estimated as having consumed less than 3% of the total annual water supply in the Dallas-Fort Worth area (Fry et al., 2012), a recent study projected that hydraulic fracturing operations in the Eagle Ford Shale could be as high as 89% of the total annual water consumption in La Salle County by 2019 (Nicot and Scanlon, 2012). This indicates that freshwater consumption by the oil and gas industry could significantly compete with other uses, particularly if drought conditions persist. This concern is especially relevant in the Eagle Ford Shale, where fresh surface water is scarce and fresh groundwater from the Corrizo-Wilcox aquifer has a limited yield (Hanson, 2009). The development of shale gas formations has realized a secure natural gas supply for decades to come. However, to minimize competition between the oil and gas industry and other users for fresh water resources in draught stricken regions like South Texas, non-potable water supplies – particularly brackish water – should be substituted for freshwater for hydraulic fracturing operations whenever possible. Although data related to water use for shale energy extraction is improving (FracFocus, 2013), information about the sources of water used, amount of water withdrawn from each source, and the volume and quality of flowback and produced water returned to the surface is sparse (Freyman and Salmon, 2013). While flowback recycling rates are estimated to be as high as 40% in the Marcellus Shale (Lutz et al., 2013), recycling rates in the Eagle Ford remain at below 5%. However, use of saline water for hydraulic fracturing in the Eagle Ford Shale was estimated to be about 20% (Nicot et al., 2012). Brackish Groundwater in the Eagle Ford Shale Region Although fresh groundwater resources are limited in Texas, the State has significant brackish groundwater resources (defined as between 1,000 and 10,000 mg/L of total dissolved solids). The largest amount of brackish groundwater (514 billion m3) in Texas is present in the Region L (South Central Texas) water planning region, and

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most of this (113 billion m3) has a TDS of less than 3,000 mg/L (Kalaswad et al., 2004). Region L also contains ten counties at the center of the Eagle Ford Shale activity (i.e., Atascosa, DeWitt, Dimmit, Frio, Goliad, Gonzales, Karnes, La Salle, Wilson and Zavala). The productivity of the Corrizo-Wilcox aquifer, one of the best potential sources of brackish groundwater in Texas, is high (where productivity is a relative measure of the ease at which groundwater can be produced from an aquifer). However, because depths to brackish groundwater may range from 900 to 1,800 meters, costs to produce brackish groundwater from the Corrizo-Wilcox are projected to be relatively high. The Goliad Coast aquifer, located at the southern end of Region L in Karnes and Goliad counties, also has high productivity and low production costs for brackish groundwater (LBG-Guyton, 2003). In 2010, Region L had approximately 10 percent of the state’s population, and it is projected that by 2060 its population will increase by 75 percent. The Region’s water demands are projected to increase 32 percent during this time, with municipal water use constituting the greatest increase. In 2013, Region L faced water supply needs of 215 million m3 per year, and by 2060 water needs are projected to increase to 164 m3 per year and to be dominated by municipal water use. Recommended water management strategies for meeting the Region L water supply includes 16.5% desalination by 2060 (TWDB, 2012). Desalination Concentrate Use for Hydraulic Fracturing Although freshwater resources are currently predominantly used for hydraulic fracturing operations, freshwater resources in the Eagle Ford Shale region are scarce. However, there are abundant supplies of brackish groundwater in South Texas (Chowdhury and Mace, 2007). Moreover, there is general consensus within the oil and gas industry that alternatives to freshwater need to be developed in the face of uncertain drought conditions and regulatory environment; indeed, the API Water Management Associated with Hydraulic Fracturing Manual states that non-potable water should be used “whenever practicable” (API, 2010). The proposed study will evaluate some of the geochemical aspects that may affect the potential for using brackish groundwater desalination concentrate streams as hydraulic fracturing fluid. This concept has the advantage of reducing the consumption of freshwater for hydraulic fracturing while simultaneously providing desalination facilities with a low-cost, or even profit-making, alternative for concentrate disposal (Burnett and Bateman, 2012). Although the availability of fresh surface water and groundwater in Texas has declined with increasing population, installed brackish desalination capacity has increased by 445% since 1999 (Ward, 2011). Consequently, brackish groundwater desalination is becoming an important “drought resistant” source of fresh water, especially in coastal areas where fresh groundwater availability is limited, and is projected to supply 11% of the “new” water supply in Texas by 2060 (Arroyo, 2011). Of particular interest, the San Antonio Water System (SAWS) plans to complete a full-scale 38000 m3/day brackish groundwater desalination plant (with a 12500 m3/day brine reject stream) in 2016. Current plans are to dispose of the saline

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concentrate stream using deep injection wells located in southern Bexar County near the center of the Eagle Ford Shale, at a cost of millions of dollars (SAWS, 2012). The primary environmental concern associated with desalination is concentrate disposal (UNEP, 2008; Gamboa & Clapp, 2012). One alternative for RO desalination concentrate disposal in Texas is to use it as hydraulic fracturing for hydraulic fracturing operations. This would have two synergistic advantages (1) elimination of desalination concentrate discharges to surface waters, (2) provision of a low-cost source of water for the oil and gas industry that does not consume freshwater supplies. The oil and gas industry is moving towards treatment and reuse of flow back water, largely because treatment-and-reuse strategies are economically competitive with current deep-well injection methods. However, flowback water typically constitutes only 20-40% of the injected fluid and consequently, even if 100% of the flowback water were treated and reused, there would still be need for significant volumes of supplemental water. Fortunately, frac water does not have to be fresh water; rather, the best water for fracturing is clean salt water with low concentrations of multivalent cations and bacteria. Recent studies have indicated that increasing the chloride concentration in fracturing water actually boosts gas production (Jenkins, 2012). Other potential advantages of using desalination concentrate instead of, or in addition to, treated and recycled flowback water include: (1) lower TDS (~12,000 mg/L); (2) significantly less variability in overall water quality; (3) lower concentrations of problematic scale-forming ions like barium and strontium; (4) lower microbial and suspended solids concentrations due to desalination pretreatment steps (e.g., 5-μm cartridge filters); and possibly (5) residual scale inhibitor (added to the desalination feed water to prevent scale forming on the RO membranes). A potential problem with using desalination concentrate for hydraulic fracturing fluid is that when high-salinity water (particularly with high multivalent cation concentrations) is injected into shale formations, it will interact with the host rock at the increased temperature and pressure, often resulting in scaling that can lead to formation damage and diminished gas recovery (Alotaibi and Nasr-El-Din, 2009; Burnett and Veil, 2004). Although calcite (CaCO3) precipitation can be minimized through pH control, precipitation of gypsum (CaSO4), barite (BaSO4), celestite (SrSO4) and other scale-forming minerals are much harder to control and can significantly decrease the hydraulic conductivity of shale formations during hydraulic fracturing operations (Blauch, 2010). In addition, injection of slick water fracturing fluids can potentially mobilize clayey materials and fines, which can also damage the formation (Nicot and Chowdhury, 2005). Unfortunately, commercially available chemical additives (e.g., friction reducers, surfactants, clay stabilizers, scale inhibitors, and biocides) do not all perform well in waters with high salinity, and particularly in waters with high divalent cations like calcium and magnesium. To overcome the limitations of commercially available chemical additives when used with brackish water, chemical manufactures and service companies are developing high-brine tolerant additives). For example, Chesapeake Energy, Inc., has developed salt-tolerant friction reducers and cross-linked gels as part of their Green Frac® program (Chesapeake Energy, 2012). In some cases studies have found significant improvement of slick water treatments where high brine water is used in shale fracturing. For example, use of brackish water can eliminate the

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necessity of adding 2% KCl as a clay stabilizer (Paktinat et al., 2011). However, due to the geological complexities of each shale formation, it is necessary to assess chemical additives on a case-by-case basis to avoid incompatibilities (e.g., hardness will affect various polyacrylamide friction reducers differently). RESEARCH OBJECTIVES The main research objective of this study is to investigate the feasibility of using brackish groundwater desalination concentrate streams as hydraulic fracturing fluid in the Eagle Ford Shale. This objective will be achieved by initially performing the following tasks: 1. Performing a comprehensive time-series chemical characterization of the concentrate stream from a brackish groundwater reverse osmosis (BWRO) desalination plant in the City of Kenedy in Karnes County, Texas; 2. Performing a thorough chemical characterization of frac flowback water generated from hydraulic fracturing operations in the Eagle Ford Shale in Karnes County. 3. Performing a geochemical modeling analysis (using the PHREEQC software package [Parkhurst, 2013]) to assess the down-hole scaling potential associated with: (i) the desalination concentrate alone, (ii) the frac flowback water alone (assuming it is treated to remove suspended solids, oil, and grease), and (iii) blended desalination concentrate and treated frac flowback water. RESEARCH METHODS Chemical Characterization of RO Concentrate The City of Kenedy is the largest community in Karnes County, which is in the middle of the Eagle Ford Shale play. A brackish water reverse osmosis (BWRO) desalination plant was constructed on the south side of the city in 1995, and was expanded in 2005. It is currently operated by Veolia Water for the City of Kenedy. In 2007, actual permeate production was 2700 m3/day and actual concentrate discharge was 1350 m3/day. The facility discharges the concentrate through a pipe to the abandoned arm of Escondido Creek. A comprehensive chemical time-series characterization of the City of Kenedy RO reject concentrate stream will be performed for the water quality parameters listed below (under “Analytical Methods”). The research team is currently coordinating with Veolia Water and the City of Kenedy to set up a schedule for collecting concentrate samples once per month over a 12-month period. Chemical Characterization of Flowback Water Pioneer Natural Resources has a number of drilling permits in the Eagle Ford Shale located within a few kilometers from the BWRO desalination plant in Kenedy County (Fig. 1). Each one of these wells is expected to produce roughly 1900 m3 of

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flowback water. The research team is currently coordinating with Pioneer Natural Resources to set up a schedule for collecting hourly grab samples of flowback water over two days at a minimum of two hydraulic fracturing sites. The collected samples will be analyzed for the water quality parameters listed below (under “Analytical Methods”) to characterize the quality of the flowback as a function of time.

FIG. 1. Location of eight Pioneer Natural Resources drilling sites and their proximity to the brackish groundwater RO desalination plant in the City of Kenedy (Mineral Rights Forum, 2013). Source: “Kenedy, Texas.” 28°50'20.74"N and 97°48'49.58"W. Google Earth. March 2, 2013. Analytical Methods The collected RO concentrate and flowback water samples will be analyzed for the following constituents: • Dissolved oxygen (DO), pH, conductivity and temperature will be measured in the field (both at RO desalination plant and hydraulic fracturing sites) using a calibrated YSI 6920 Multi-parameter Water Quality Sonde. • Alkalinity will be measured by titration with standardized H2SO4. Carbonate and bicarbonate concentrations will be calculated from the alkalinity and pH. • Dissolved sulfide will be measured in the field using the methylene blue spectrophotometric method.

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The residual phosphonate-based antiscalant in the concentrate stream will be determined using ASTM Method D6501-09: Standard Test Method for Phosphonate in Brines (ASTM, 2013). Total dissolved solids (TDS) and total suspended solids (TSS) will be measured gravimetrically. An inductively coupled plasma – mass spectrometer (ICP-MS) will be used for dissolved cation analyses (Ca, Mg, Na, K, Fe, Ba, Sr, Si, As, B). Samples will be filtered through as 0.45-μm nylon filter and acidified to pH below 2 using nitric acid before analysis. Samples for total iron analysis will be prepared by dissolving the sample in 1 N H2SO4 before filtration. An ion chromatograph (IC) will be used for anion (Br-, Cl-, F-, NO3-, SO42-, and PO43-) analyses. Samples will be filtered through as 0.45-μm nylon filter before analysis. Standard Methods 1020 and 1030 (APHA, 1998) will be followed to assure appropriate QA/QC methods are followed.

CONCLUSIONS Using reject concentrate streams from groundwater RO desalination plants located within the Eagle Ford Shale region as hydraulic fracturing fluid could have two synergistic advantages: (1) elimination of brackish desalination concentrate discharges to surface waters, and (2) provision of a source of water for the oil and gas industry that does not consume freshwater supplies. This research will identify opportunities and obstacles for using brackish groundwater desalination concentrate for hydraulic fracturing operations. Lessons learned can be applied to other brackish water sources, including cooling tower blow down from refineries and power stations. It is also expected that the water characterization and subsequent geochemical modeling studies will complement ongoing frac water treatment research, and will contribute towards forging productive collaboration between the oil and gas industry, the industrial water treatment industry, municipalities and academia in South Texas. ACKNOWLEDGMENTS This research is supported through a grant from the Texas General Land Office’s Coastal Impacts Technology Program (CITP), which is administered by the Houston Advanced Research Center (HARC), with additional seed funding from the Texas A&M University-Kingsville University Research Council. REFERENCES Alotaibi, M.B., and Nasr-El-Din, H.A. (2009). “Chemistry of injection water and its impact on gas recovery in carbonate and clastic formations.” SPE paper 121565, presented at the 2009 SPE International Symposium on Oilfield Chemistry held in The Woodlands, Texas, April 20-22, 2009.

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