Correspondence/Rebuttal pubs.acs.org/est
Comment on “Comparison of Water Use for Hydraulic Fracturing for Unconventional Oil and Gas versus Conventional Oil”
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from the formation. Figure 1 compares the literature values of water injections, makeup injection water requirements, and
he unconventional extraction of oil and gas from shale formations has recently become economical due to advances in hydraulic fracturing and horizontal drilling technologies. A byproduct of this new production is the consumption of water associated with hydraulic fracturing technology. Scanlan et al. (2014)1 analyzed the consumption of water resources associated with new unconventional production of oil and gas from the Bakken formation in Eastern Montana and Western North Dakota and the Eagle Ford Formation in South Texas. In the manuscript, the authors estimated ratios of the water consumed to oil produced (WORs) in new shale plays and compared these estimates to WORs from conventional production. The conclusion drawn is that the WORs of unconventional shale oil plays “are within the lower range of those for conventional oil production, considering the well lifetime.” The comparisons made in the paper fail to account for the large differences in the maturity of conventional and unconventional wells and thus unfairly characterize new shale oil plays as having lower water intensity than conventional operations. Recovery operations from conventional wells typically progress through several stages of development as the well matures. Following well construction, the reservoir produces petroleum with little to no external stimulus. After the primary production period, water is typically injected during a secondary water flooding period that is often followed by a tertiary recovery period that may utilize chemicals, heat, and/or gases in addition to water to maintain reservoir pressure. The comparison of current levels of water consumption in shale plays associated solely with well development and primary production to water consumption from mature wells utilizing secondary and tertiary recovery technologies is unreasonable, particularly in the context of estimated ultimate recoveries. At this time it is unclear whether enhanced recovery technologies will be economical in shale formations as they have been in other formations because of lower permeability; however, water flooding and other enhanced recovery technologies for shale are under investigation.2−4 CO2 injection appears particularly viable and may have lower water intensity; however, gas injection is often accompanied by water injection and the literature5 indicates higher WORs for CO2 injection than water flooding. In any case, the cover art and several of the figures presented by Scanlan et al. (2014) compare water consumption estimates for primary, secondary, and tertiary recovery stages from conventional wells to production solely from the primary period in these new shale plays. As such they unfairly portray shale oil recovery as having lower water intensity across its lifecycle than recovery from conventional operations. The WORs for conventional recovery presented by Scanlan et al. (2014) are derived primarily from Wu and Chiu (2011),5 who compiled literature values for different technologies and estimated a US average injection of 8 gallons of water per gallon crude oil produced consisting of 2.1−5.4 gallons makeup water with the remainder coming from recycled produced water © 2015 American Chemical Society
Figure 1. Comparison of water injection and consumption for different technologies throughout the lifecycle of petroleum reservoirs. Primary production requires water for well development (drilling and fracturing) but not for operations. Emerging technologies should be compared with conventional technologies on a consistent basis (at the same stage in the well lifecycle).
water used for well development (i.e., drilling and fracturing) for various technologies from Wu and Chiu (2011)5 and Scanlan et al. (2014).1 The water consumption estimate associated with well development (i.e., primary production only) in conventional formations is less than water consumption associated with the new shale plays. It is important to distinguish between water consumption/injection associated with primary, secondary, and tertiary recovery operations from formations so they can be compared with conventional recovery operations on a consistent basis.
David J. Lampert*
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Energy Systems Division, Argonne National Laboratory, Lemont, Ilinois 60439, United States
AUTHOR INFORMATION
Corresponding Author
*Phone: 630 252 2533; e-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Scanlon, B. R.; Reedy, R. C.; Nicot, J. P. Comparison of water use for hydraulic fracturing for unconventional oil and gas versus conventional Oil. Environ. Sci. Technol. 2014, 48 (20), 12386−12393.
Published: May 4, 2015 6358
DOI: 10.1021/acs.est.5b00963 Environ. Sci. Technol. 2015, 49, 6358−6359
Environmental Science & Technology
Correspondence/Rebuttal
(2) Iwere, F. O.; Heim, R. N.; Cherian, B. V. Numerical Simulation of Enhanced Oil Recovery in the Middle Bakken and Upper Three Forks Tight Oil Reservoirs of the Williston Basin. In SPE Americas Unconventional Resources Conference; Society of Petroleum Engineers, 2012. (3) Morsy, S.; Sheng, J. J.; Roland, O. E. Potential of Waterflooding in Shale Formations. In SPE Nigeria Annual International Conference and Exhibition; Society of Petroleum Engineers, 2013. (4) Mirchi, V.; Saraji, S.; Goual, L.; Piri, M. Dynamic interfacial tensions and contact angles of surfactant-in-brine/oil/shale systems: Implications to enhanced oil recovery in shale oil reservoirs. In SPE Improved Oil Recovery Symposium; Society of Petroleum Engineers, 2014. (5) Wu, M.; Chiu, Y. Consumptive Water Use in the Production of Ethanol and Petroleum Gasoline−2011 Update; Argonne National Laboratory Technical Report, ANL/ESD/09-Update 2011, 2011.
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DOI: 10.1021/acs.est.5b00963 Environ. Sci. Technol. 2015, 49, 6358−6359
