Beneficial Reuse of Permian Basin Produced Water

Introduction
The Permian Basin is the largest oil and gas production basin in the United States. Management of the produced water generated from these activities has become a major issue facing oil & gas operators as regulators increase restrictions on the traditional disposal well method. This has led to the pursuit of beneficially reusing the produced water by treating to surface water discharge or industrial reuse quality. Treatment of Permian Basin produced water is exceptionally challenging due to its high salinity (≈15 percent). This paper will provide an overview of beneficial reuse drivers, regulations, treatment technologies and challenges.

Overview
During oil and gas extraction, produced water that is naturally present in the geological formations is brought to the surface along with the hydrocarbons. It is estimated that 20 million barrels per day1 (bpd) of produced water is generated in the Permian Basin from the 6.6 million bpd2 of oil production. The water contains a mixture of salts, residual oil, and naturally occurring radioactive materials. The exact composition varies by geological formation.

Beneficial Reuse Drivers
Disposal of produced water in deep wells (i.e., depths below the Wolfcamp shale formation) is understood to induce regional seismicity. In January 2024, the Texas Railroad Commission (RRC) suspended a total of 56 deep disposal wells in the Northern-Culberson Reeves Seismic Response Area (SRA) and Gardendale SRA (both located in the Permian Basin) due to a series of seismic events, shown in Figure 1. Produced water may also be disposed in shallow disposal wells (i.e., depths above the Wolfcamp shale formation) but have had their capacity curtailed because of limits on allowable formation pressures, shown in Figure 2. The RRC now requires pressure monitoring and recording for all new or amended disposal well permits3. These two regulatory actions coupled with increasing oil and gas production4 are driving the need for an alternative ways to manage produced water.

Regulatory Update
The term 'Beneficial Reuse' is in reference to Environmental Protection Agency's Oil and Gas Point Source Category, Subcategory E titled 'Agricultural and Wildlife Water Use'5. This subcategory grants the oil and gas extraction industry the ability to discharge treated produced water west of the 98th meridian for the propagation of agriculture or wildlife. Discharge under this subcategory is regulated by Texas Commission on Environmental Quality (TCEQ) through the Texas Pollutant Discharge Elimination System (TDPES). Currently there is only one finalized TPDES application to discharge in Texas, located in near the Eagle Ford Basin in south Texas. Three other applications (all located in the Permian Basin) are pending administrative review. Other regulated produced water management methods include recycling the produced water for use in hydraulic fracturing (requires no permit), treatment and land application (requires RRC permit), or treatment for industrial reuse (requires no permit, contingent on quality). Industrial reuse applications not only include cooling tower water makeup, but also novel concepts such as feed water for green hydrogen projects or use in data center cooling — both of which will be discussed further in the report. On January 8, 2024, the RRC issued a framework6 for produced water treatment pilot study authorizations for discharge via land application. The pilot framework is intended to minimize the regulatory hurdles of produced water pilot testing and provide produced water quality data to regulators. Further discussion of this framework and its potential implication will be discussed in the paper.

The New Mexico regulatory framework will also be discussed in the paper since the Permian Basin crosses State lines.

Treatment Technology and Challenges
Typical Permian Basin produced water quality is presented in Table 1. The key driver for treatment design is desalination with the two main technologies7 being membranes and thermal desalination. Both technologies produce a brine waste stream that must be managed through well disposal or crystallization; or recovered as an asset and used to harvest critical minerals or generate power8.

The desalinated water requires polishing treatment for ammonia removal and other trace compounds. There are three main options for ammonia polishing: biological, adsorption, and stripping. The paper will present techno-economic evaluation of ammonia polishing options conducted by the authors. A comparison of desalination and ammonia removal technologies are presented in Table 2.

The paper will present the latest the technology options, their development and implementation status, and publicly-available performance data.

Conclusions
Beneficial reuse of produced water offers oil and gas operators an alternative management option to the restrictions being placed on well disposal. As treatment technologies are piloted and commercialized, the full scale produced water treatment may become feasible based on relative economics. Regulatory permitting will also become more favorable as additional knowledge and understanding of produced water is gained.