Producing hydrocarbons from tight formation source rocks, through the advent of improved technologies in hydraulic fracturing, has become one of the most important changes in the North American petroleum industry in decades. In the last decade, the practice has evolved from a novelty concept to a common method of extraction. Between 2009 and 2011, permits acquired for the Eagle Ford Play (EF) went from 50 to 600 (Driskill et al., 2012). Tapping the shale resources in the EF is advancing at an astonishing pace; today the permitted well count stands at 5,458 wells in the EF (Texas Railroad Commission, accessed April 13, 2013). A multitude of recent studies has found that the hydraulic fracturing process itself has had very little impact on environmental quality and most incidences of contamination occurred on the surface (Duncan, 2012).
Under Texas state water code, groundwater withdrawal for oil and gas exploration, fracking included, is exempt from the regulatory authority of the groundwater conservation districts (Rahm, 2011). Interdependency exists between energy and water production. Shale gas production currently accounts for less than 1% of statewide water withdrawals in Texas; however, impacts on a local level vary with competing demands and water availability. Between the years 2006 and 2010 shale gas production increased by an annual average rate of 50%. To date, most studies have focused attention on water quality effects from shale gas activity. Published studies on the environmental impacts of hydraulic fracturing and the quantity of water used are few. In his June 10th, 2011 presentation to a Laredo, Texas town hall meeting, Robert Mace (2011) from the Texas Water Development Board demonstrated how the Groundwater Availability Model (GAM) simulates groundwater levels in the Carrizo-Wilcox Aquifer well below desired future conditions which limit groundwater level decline to 23 feet (Mace 2011).
Source: (Mace presentation, 2011)
Although water for oil and gas production is less than 1% in Texas, Mace estimates the water for oil and gas production will be responsible for less than 10% of all water consumption in the EF region. There is currently some focus on using brackish groundwater for fracking; however, the commonly used polyacrylamide friction reducers do not perform as well in slightly saline water (Nicot and Scanlon, 2012). In September of 2012, Nicot and al. (2012) updated their projected water use analysis based on recent shifts in hydraulic fracturing technologies. Water use had increased in the EF, however, the increased use was due to an additional 1400 wells coming on line in 2011. The operators in the EF have managed to halve their water consumption per well in approximately four years. This is due to a transition into the practice of using cross-linking gels to deliver the proppant. Mauer (2011) reports that the massive fracs required in the EF range in cost from $3 to $5 million each. According to Mauer (2011), current technologies typically require 4 million gallons of water, five million pounds of proppants and 40,000 horsepower worth of high pressure pumping capability. Mauer estimates potential savings for well operators of 1$ to 1.5$ million per well with the accelerated developments in cross-linking gels as the proppant carrier in the Eagle Ford Play. The use of gels has proven to facilitate improvements to hydrocarbon recovery while eliminating complications caused by the use of more water intensive fracturing while also not requiring such big expensive pumps. The use of gels has proven to also be more compatible with flowback water reuse and the use of brackish water (Mauer, 2012; Nicot et. al. 2012). Advancement in fracing techniques has allowed Nicot et al. (2012) to reduce projections of anticipated water use of 13 million gallons per well to approximately 5 million gallons per well. However, the EF Play has been projected to have the most wells, at approximately 100,000 drilled with a high lateral density, compared to other shale plays in Texas (Nicot and Scanlon, 2012).
Eagle Ford Shale Water Intensity:
Source: (Nicot et. al., 2012)
Eagle Ford Shale county-level average lateral spacing.
Source: (Nicot et. al., 2012)
Shale gas production may be limited by water availability in semi-arid regions (Arthur et. al. 2009). Surface water is scarce in the EF play. To date, most of the fresh water used to produce the EF has been drawn from the Carrizo-Wilcox aquifer, except for small usages of water drawn from the Rio Grande at the border of Mexico. Nicot and Scanlon (2012) estimate the net water use for EF production to reach 1870 Mm3 (1515 kAF) with peak consumption in the year 2024 at 58Mm3(48 kAF). However, these projections are likely to change in light of Nicot et al. (2012) findings which show a decreasing water intensity trend for the EF Play. Nicot et al. (2012) estimate the net water usage in the EF for 2011 to be 24kAF. As shale plays develop it is likely that unique fracing blends will evolve for specialized regions within each play (Mauer, 2012; Nicot et al, 2012).
In South Texas, many large springs have disappeared and a transition from gaining to losing streams is already occurring due to extensive over pumping by the Winter Garden region for irrigation. Water level declines greater than 60m over a 6500km2 region have been observed (Nicot and Scanlon, 2012). It is unknown whether the large Carrizo-Wilcox aquifer with extensive water reserves can recover from transient stress quickly enough to also accommodate additional demand from population increases. However, in a recent personal communication with Dr. Charles Kreitler who works for both the University of Texas at Austin and LBG Guyton Associates, he stated “This is a problem that developed in the outcrop area of the Carrizo in the first half of the 20th century. Pumpage has been down significantly in the 80’s and 90’s in the confined section of the Carrizo (SE of Carrizo Springs) and the water levels have responded” (Kreitler, 2013). Nicot and Scanlon (2012) stress the need for financial resources to be assigned to better understand the sustainability and rebound potential of the Carrizo-Wilcox Aquifer. Mean annual precipitation is 740mm/yr in the EF play. The area goes through frequent periods of wet/drought cycles and is likely to be more pronounced with climate change. Brownlow (2010) estimates the impact to the Carrizo-Wilcox Aquifer to be very minimal over the life of the EF play. He states that currently 275,000 acre feet are withdrawn annually from the Carrizo-Wilcox and that 300,000 acre feet would be the total withdrawal for EF production over a 10-15 year life of the play. Brownlow (2010) also calculates an acre foot value of Carrizo-Wilcox water of $520,000 by landowners receiving oil and gas royalties versus $250 acre foot value to those growing crops with this water (Brownlow, 2010).
Arthur, J.D., D. Bohm, and D. Cornue. 2009. “Envrironmental Considerations of Modern Shale Gas Development.” Society of Petroleum Engineers SPE 122931: 10. http://www.spe.org/atce/2009/pages/schedule/documents/spe1229311.pdf.
Brownlow, Darrel T. 2010. “Eagle Ford Shale Play and the Carrizo Aquifer.” Fountainhead 4th quarter 2010: 4. http://www.tgwa.org/downloads/newsletter/Fountainhead-Q4-2012.pdf.
Duncan, Ian. 2012. “Fact-based Regulation for Environmental Protection in Shale Gas Resource Development.” The Energy Institute: 127. http://groundwork.iogcc.org/sites/default/files/UT%20Energy%20Inst%20%20Fracking%20Report%202-15-12%20.pdf.
Kreitler, Charles, Ph.D. 2013.
Mace, Robert E. 2011. “Fracking and Water Resources: The Pearsall/Eagle Ford Shale and South Texas.” Presentation atTown Hall Meeting June 10, 2011; Laredo, Texas (June 10): 24. http://safefrackingcoalition.files.wordpress.com/2011/08/2011-0610-mace-laredo-fracking.pdf.
Mauer, Dr. William. 2011. “JIP to Improve Eagle Ford Hydraulic Fracturing Technology.” Mauer Engineering Inc. Austin, TX 78733 TP11-1 (May 9): 46. http://maurerengineering.com/PDFfiles/FRACING%20PROPOSAL%20%20WITH%20SLIDES%20MAY%2010%20PDF.pdf.
Nicot, Jean-Philippe, Robert C. Reedy, Ruth A. Costley, and Yun Huang. 2012. “Oil & Gas Water Use in Texas: Update to the 2011 Mining Water Use Report.” Texas Oil & Gas Association, Austin, Texas (September): 117. http://www.twdb.state.tx.us/publications/reports/contracted_reports/doc/0904830939_2012Update_MiningWaterUse.pdf.
Nicot, Jean-Philippe, and Bridget R. Scanlon. 2012. “Water Use for Shale-gas Production in Texas, U.S.” Environmental Science and Technology 46: 3580–3586. doi:dx.doi.org/10.1021/es204602t | Environ. Sci. Technol. 2012, 46, 3580−3586.
Rahm, D. 2011. “Regulating Hydraulic Fracturing in Shale Gas Plays: ‘The Case of Texas’.” Energy Policy 39: 2974–2981.
Texas Railroad Commission. 2013. http://www.rrc.state.tx.us/eagleford/images/EagleFordShalePlay201303-large.jpg.