Managing Produced Water

Once produced water reaches the surface it must be properly managed. Traditionally, produced water has been considered a waste product of the oil and natural gas industry because it commonly contains levels of total dissolved solids (TDS) and other constituents (organic chemicals, inorganic chemicals, metals and naturally occurring radioactive materials). Let’s look at conventional produced water management practices, and some innovative ideas and scenarios scientists are investigating to address not only produced water issues but water challenges in general. As part of managing produced water, regulatory requirements act as a guide for activities to preserve the environment and maintain health and safety.

Conventional Produced Water Management

Produced water is often managed in storage tanks, then trucked or piped to an underground injection control (UIC) well. The underground injection well, sometimes referred to as a salt water disposal well or UIC Class II injection well, is used to dispose of the produced water deep underground. A Class II well is one used to inject fluids associated with oil and natural gas production (for example, disposal of brine, injection of water for enhanced oil recovery, hydrocarbon storage). Class II wells account for injection of over two billion gallons of fluid daily within the U.S. alone.¹U.S. Environmental Protection Agency. (n.d.). Class II Oil and Gas Related Injection Wells. Retrieved July 11, 2021, from https://www.epa.gov/uic/underground-injection-control-well-classes.

In other instances, produced water may be used for enhanced oil recovery or reused in the oilfield as make up water for drilling and stimulation activities. Advances in water treatment technology have shown promise in turning this wastewater into a future water resource. However, important scientific questions remain related to human health and environmental implications of using treated produced water for applications outside of the oil and natural gas industry.²U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Re-use, Recycled, and Renewable Water Scenarios for Produced Water

There are several ways produced water can be recycled and used for various purposes. However, the barrier to this is how much treatment is required and the economics. Depending on the purpose, more or less treatment is required. Let’s look at various scenarios, some in operation and some undergoing consideration and research in various parts of the country, for management of produced water. For example, re-using produced water for municipal purposes such as drinking water, is currently extremely taxing and expensive; therefore, it’s not a viable option yet. These scenarios involve levels of re-use, recycling, and disposal. First a few definitions for clarity:³U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Re-use water is any fluid that is generated from an oil and natural gas well, undergoes minimal treatment, and is used again in an oil or natural gas well before disposal in an underground injection well.

Recycled water is any water that is generated from an oil or natural gas well, undergoes significant treatment, and is used again outside of the oil and gas sector.

Renewable water is fluid that is generated from an oil or natural gas well that undergoes significant treatment and is used outside the oil and natural gas industry and is added to the hydrologic cycle, as opposed to disposed of in an underground injection well.

Disposed water is fluid that is disposed of in the appropriate UIC injection well: for example, a UIC Class II injection well.

Re-use/ Recycled Water Within the Oil and Natural Gas Industry

In this scenario, produced water is managed in storage vessels and piped or trucked to either a treatment plant or a UIC Class II injection well. The produced water entering the treatment plant undergoes the necessary treatment to ensure the quality of the effluent is sufficient for the desired use or application. In this case, the minimally treated produced water is re-used or recycled for use in the oil and natural gas industry. The residuals are those materials that are generated from the treatment process. The residuals may be a commodity product sold to another party. Wastes from such a process are managed in the appropriate UIC injection well or otherwise disposed of as regulated oilfield wastes.⁴U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Examples of re-use and recycling of produced water in oil and natural gas operations include: drilling, drilling muds, mixing of hydraulic fracturing fluids, cementing, workovers, secondary recovery, pressure maintenance, enhanced oil recovery in waterfloods, and plugging operations.⁵U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Renewable Water/ Surface Water Discharge

In this scenario, produced water is managed in storage vessels and piped or trucked to either a treatment plant or a UIC Class II injection well. Produced water entering the treatment plant undergoes the necessary treatment to ensure the quality of the effluent is sufficient for the desired use or application. In this case, the treated produced water is discharged to a surface water body. Both the quality of the effluent and the receiving water body’s water quality is regulated.⁶U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Industrial Use/ Commercial Sales Outside the Oil and Natural Gas Industry

In this scenario, produced water is managed in storage vessels and piped or trucked to either a treatment plant or a UIC Class II injection well. Produced water entering the treatment plant undergoes the necessary treatment to ensure the quality of the effluent is sufficient for the desired use or application. In this example, the treated produced water is sold to industrial/commercial users outside the oil and natural gas industry. The quality of the effluent is likely dictated by the industrial/commercial user specifications and possibly other government agencies.⁷U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

The energy sector is responsible for withdrawing water for activities related to electricity generation, such as cooling thermoelectric power plants. Depending upon the economics, produced water may or may not be a viable alternative for these procedures. Additionally, produced water can be used for mining operations, such as extracting coal and lithium.⁸Scanlon, B. R., Reedy, R. C., Xu, P., Engle, M., Nicot, J. P., Yoxtheimer, D., Yang, Q., & Ikonnikova, S. (2020, February 3). Can we beneficially reuse produced water from oil and gas extraction in the U.S.? Science of The Total Environment. https://www.sciencedirect.com/science/article/pii/S0048969720305957. https://doi.org/10.1016/j.scitotenv.2020.137085 The industrial sector involves manufacturing of goods and other vital supplies for our everyday lives. However, manufacturing of goods and services requires water, and generally a lot of it. Treatable produced water therefore can suffice as a resource for water withdrawal. 

Agricultural Uses

In this scenario, produced water is managed in storage vessels and piped or trucked to either a treatment plant or a UIC Class II injection well. Produced water entering the treatment plant undergoes the necessary treatment to ensure the quality of the effluent is sufficient for the desired use or application. In this case, the water is treated for an agricultural use. As with industrial use/commercial sales outside the oil and natural gas industry, the quality of the water may be dictated by industry standards and/or a federal or state agency. The quality of the treated water may also be regulated by a regulatory agency permit if used for irrigation or another agricultural use that could affect groundwater quality.⁹U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

For example, the Ogallala Aquifer, underlying portions of the Texas Panhandle, is being depleted at an exceedingly high rate. Produced water resources can help to mitigate the use of groundwater extraction in this area and areas alike. However, irrigating crops that humans consume requires intensive treatment of the produced water for chemicals and dissolved solids. Additionally, research has found that water scarcity issues in these semi-arid/arid regions will not be lessened by the use of produced water alone, given water demand for irrigation greatly exceeds what produced water can do to mitigate scarcity.¹⁰Scanlon, B. R., Reedy, R. C., Xu, P., Engle, M., Nicot, J. P., Yoxtheimer, D., Yang, Q., & Ikonnikova, S. (2020, February 3). Can we beneficially reuse produced water from oil and gas extraction in the U.S.? Science of The Total Environment. https://www.sciencedirect.com/science/article/pii/S0048969720305957. https://doi.org/10.1016/j.scitotenv.2020.137085

Municipal Uses

In this scenario, produced water is managed in storage vessels and piped or trucked to either a treatment plant or a UIC Class II injection well. Produced water entering the treatment plant undergoes the necessary treatment to ensure the quality of the effluent is sufficient for the desired use or application. In this case, the treated produced water is used for non-potable or potable uses.¹¹U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Typical uses of reclaimed water include irrigation of parks, golf courses, athletic fields, and cemeteries, firefighting, aesthetic ponds, dust suppression, construction, and street cleaning.¹²U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Subsurface Discharges for Groundwater Management

In this scenario, produced water is managed in storage vessels and piped or trucked to either a treatment plant or a UIC Class II injection well. Produced water entering the treatment plant undergoes the necessary treatment to ensure the quality of the effluent is sufficient for the desired use or application. In this case, the treated produced water is used to recharge groundwater for managing underground hydrologic conditions by increasing aquifer storage. Discharge of treated produced water into groundwater for a groundwater management purpose would be subject to the applicable Class V UIC requirements.¹³U.S. Environmental Protection Agency and State of New Mexico. (2018, November 9). Oil and Natural Gas Produced Water Governance in the State of New Mexico—Draft White Paper. www.epa.gov/sites/production/files/2018-11/documents/oil_and_natural_gas_produced_water_governance_in_the_state_of_new_mexico_draft_white_paper_508.pdf

Feasibility of this type of re-use is currently being determined in shale plays such as the Permian Basin in West Texas.¹⁴Scanlon, B. R., Reedy, R. C., Xu, P., Engle, M., Nicot, J. P., Yoxtheimer, D., Yang, Q., & Ikonnikova, S. (2020, February 3). Can we beneficially reuse produced water from oil and gas extraction in the U.S.? Science of The Total Environment. https://www.sciencedirect.com/science/article/pii/S0048969720305957. https://doi.org/10.1016/j.scitotenv.2020.137085 Another option includes storing produced water in groundwater confining units that can later be used for various purposes in the energy and industrial sectors, such as injection fluids for hydraulic fracturing.

Produced Water and the Hydrologic Cycle

One of the major criticisms of the use of water in the development of oil and natural gas supplies, particularly in the hydraulic fracturing of shale plays, is the so-called “permanent removal” of water from the surface and near sub-surface (effective) hydrologic cycle. Because the majority of produced water either remains in the formation or is disposed of in another suitable geologic formation (via Class II SWDs), this water is indeed removed from the effective hydrologic cycle.¹⁵Mantell, M. (2011, March 10-11). Produced Water Reuse and Recycling Challenges and Opportunities Across Major Shale Plays. EPA Hydraulic Fracturing Study Technical Workshop #4Water Resources Management https://www.epa.gov/sites/production/files/documents/09_Mantell_-_Reuse_508.pdf

But a number of statistics suggest the story doesn’t end there. When natural gas is combusted with oxygen, there are two by-products: carbon dioxide and water vapor. The generation of water vapor ultimately offsets the removal of water from the effective hydrologic cycle. Industry data from U.S. shale operations in the Haynesville, Marcellus, Barnett, and Fayetteville formations, show that a well in these areas produces enough natural gas in less than nine months, that when combusted, offsets the entire volume of water used in the development of that well. These numbers assume that wells will produce natural gas for more than 20 years.¹⁶Mantell, M. (2011, March 10-11). Produced Water Reuse and Recycling Challenges and Opportunities Across Major Shale Plays. EPA Hydraulic Fracturing Study Technical Workshop #4Water Resources Management https://www.epa.gov/sites/production/files/documents/09_Mantell_-_Reuse_508.pdf

Regulating Produced Water Disposal 

Disposal wells for produced water are regulated by the U.S. Environmental Protection Agency (EPA), or if regulatory authority has been granted to the state, a local agency. Guidelines have been established under the EPA’s Underground Injection Control (UIC) Program. The UIC Program was implemented for the purpose of protecting water resources, specifically drinking water under the Safe Drinking Water Act. Regulatory sections in the UIC Program detail a number of requirements that must be met by both the regulatory authority and the party operating the injection well, such as sufficient monitoring procedures, operational reports, public posting of reporting.¹⁷Environmental Protection Agency. (2016, September 6). Underground Injection Control Well Classes. EPA. https://www.epa.gov/uic/underground-injection-control-well-classes.