Underground Injection for Future Water Use

Fact Sheet - Underground Injection for Future Water Use

   
 
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Produced water has value for reuse in two ways. One value of produced water is as a fluid that can be used to occupy space (i.e., for hydrological purposes). The hydrological reuse of produced water is discussed in a separate fact sheet. A second value of produced water is as a source of raw water that can be treated to meet various end uses. It can be reused immediately or can be placed into storage or reserve for future use. This fact sheet discusses the option of injecting produced water into an underground formation where it can be withdrawn later for reuse. This process is known as aquifer storage and recovery (ASR).

  Diagram of ASR well cross-section.ASR well cross-section; Source: U.S. Geological Survey.
  Photo of ASR well in Florida.ASR well in Florida; Source: U.S. Geological Survey.

When water of any sort is intentionally introduced into a drinking water aquifer through injection or other means, the quality of the water must comply with all applicable drinking water standards adopted by the U.S. Environmental Protection Agency (EPA) (for the list in alphabetical order, see http://www.epa.gov/safewater/consumer/pdf/mcl.pdf [PDF]). It is paramount that the produced water has been treated to the extent necessary for the purpose of meeting these standards prior to injection.

Most produced water is very salty. The cost of removing salinity from produced water poses a barrier to injecting it into an aquifer. However, some types of produced water are relatively fresh, and hence, can be used directly with little or no treatment. This has been particularly true for produced water from some coal bed methane (CBM) fields.

The EPA treats ASR wells as Class V injection wells. In a survey conducted in 1999, the EPA identified at least 130 ASR wells in use throughout the country (EPA 1999). However, at the time, none of these were injecting produced water.

IOGCC and ALL (2006) describe an example in which CBM produced water has been injected into the aquifer of a city's well field. In the example, the City of Gillette, Wyoming, had depleted its local well field by continued pumping for many years. The well field was completed in Lower Fort Union sands at a depth of approximately 1,500 feet. The city then coordinated with a CBM operator to install Class V aquifer recharge wells with the capacity to manage all the produced water from a small, CBM-producing project.

Brost (2002) describes an operation in the Kern River field of California. Here, a blend of produced water and treated ground water is filtered and then sent to the local water district for use in irrigation and aquifer recharge. The paper does not offer more details describing how the water is further treated or injected.

An example from Colorado is described by Stewart (2006). A new project near Wellington, Colorado, is treating produced water from oil wells as a raw water resource that will be used to augment shallow water aquifers to ensure adequate water supplies for holders of senior water rights. The oil company is embarking on this project to increase oil production. A separate company will then purchase and utilize this water as an augmentation water source. This water will eventually be used to allow the Town of Wellington and northern Colorado water users to increase their drinking water supplies by 300 percent.

Before selecting ASR as the preferred technology for managing produced water, oil and gas operators must evaluate various relevant factors, including:

  • The availability of an aquifer suitable for recharge. Suitability considerations involve the areal extent, thickness, depth of the aquifer, and the presence and size of confining layers or aquitards.
  • The hydrogeology of the aquifer formation, including its porosity, permeability, transmissivity, hydraulic conductivity, flow direction and velocity.
  • The chemical characteristics of the water already residing in the aquifer and the incoming produced water. These should be compared to ensure that undesirable chemical reactions are not likely to occur in the aquifer.
  • The willingness of the jurisdictions ultimately using the water to emplace produced water in the aquifer. Operators must have the ability to obtain the necessary permits. Further, they must know the types and extent of monitoring that will subsequently be required.
  • The cost of treating the produced water to ensure compliance with all applicable injection standards.

References 
Brost, D.F., 2002, "Water Quality Monitoring at the Kern River Field," presented at the 2002 Ground Water Protection Council Produced Water Conference, Colorado Springs, CO, Oct. 16 17. Available at http://www.gwpc.org/meetings/special/PW%202002/Papers/Dale_Brost_PWC2002.pdf [PDF external site].

EPA, 1999, "The Class V Underground Injection Control Study, Volume 21, Aquifer Recharge and Aquifer Storage and Recovery Wells," EPA/816-R-99-014u, U.S. Environmental Protection Agency, Sept. Available at http://www.epa.gov/ogwdw/uic/class5/pdf/study_uic-class5_classvstudy_volume21-aquiferrecharge.pdf [PDF external site].

IOGCC and ALL, 2006, "A Guide to Practical Management of Produced Water from Onshore Oil and Gas Operations in the United States," prepared for U.S. Department of Energy, National Energy Technology Laboratory, by the Interstate Oil and Gas Compact Commission and ALL Consulting, Oct. Available at http://www.all-llc.com/IOGCC/ProdWtr/ProjInfo.htm. [external site]

Stewart, D.R., 2006, "Developing a New Water Resource from Production Water," presented at the 13th International Petroleum Environmental Conference, San Antonio, TX, Oct. 23-27. Available at http://ipec.utulsa.edu/Conf2006/Papers/Stewart_18.pdf [PDF external site].

Veil, J.A., M.G. Puder, D. Elcock, and R.J. Redweik, Jr., 2004, "A White Paper Describing Produced Water from Production of Crude Oil, Natural Gas, and Coal Bed Methane," prepared by Argonne National Laboratory for the U.S. Department of Energy, National Energy Technology Laboratory, January. Available at http://www.evs.anl.gov/pub/dsp_detail.cfm?PubID=1715 [external site].

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