Oil & Gas Journal published an article in October outlining saltwater disposal (SWD) issues in West Texas, specifically as it relates to seismic activity (OGJ, Oct. 2, 2023, pp. 39-47). After experiencing a few 4.0 events in the Northern Culberson-Reeves (NCR) Seismic response area (SRA) in Northern Delaware basin, the article reported that the Texas Railroad Commission (RRC) would, given a 4.5+ M event occurring within the next year in the SRA, shut in deep wells within its boundary for 24 months from the date of the event.
An upcoming large-scale event wasn’t so much of an “if” rather than a “when”, and “when” occurred Nov. 8. A 5.3 magnitude earthquake struck south of Mentone in Loving County, a town with a population of 22 who are served by a courthouse, gas station, post office, and school building. None appear particularly earthquake resistant.
This quake could result in a 500,000 b/d total deep injection cutback in the SRA. While the restriction initially appeared non-negotiable, operators involved in an operator led response plan (OLRP) will get together with the RRC and other stakeholders in early December to review the data and chart a plan of action.
Combined with a 300,000 b/d restriction implemented earlier this year due to other seismic activity, the total cuts could be as much as 800,000 b/d, about half the amount of produced water New Mexico alone sends to Texas for disposal.
This action will reallocate water that would have been disposed of in deep wells to shallow-water disposal instead, mostly in zones away from deep quake epicenters, but this is not an indefinite solution. This redistribution will eventually exacerbate disposal problems elsewhere, and shallow injection will further pressurize zones that need to be drilled through to land in lower ones and migrate salt water into “zombie” wells and freshwater sources.
For these reasons, reuse applications which take produced water out of the disposal stream have been piloted, but not yet implemented at large scales. Recycling occasionally gets lumped in with reuse as an alternative to SWD, but recycling uses produced water for applications such as supply-water for fracturing which return the water back into the ground. It mainly serves to conserve freshwater sources.
Purifying produced water to levels required for irrigation, cooling, and other industrial uses is technically feasible, but not yet economically viable. Unfortunately, it is competing against freshwater for many of these applications, and freshwater is significantly cheaper.
With the increase in worldwide battery lithium demand, the industry is looking closer at produced water for its lithium. ExxonMobil and Standard Lithium have implemented lithium extraction projects in the Smackover formation in Arkansas. They will use direct lithium extraction (DLE) technology to remove lithium more efficiently and with a smaller footprint than surface evaporation ponds. Instead of processing the produced water byproduct from oil extraction, ExxonMobil will drill directly into high lithium-containing brines with vertical wells to produce water directly.
Although this application has perked up the ears of Permian basin landowners who are starting to think of produced water as an additional revenue stream, Permian basin produced water has relatively low lithium content (5-150 ppm) compared with other produced waters (50-500 ppm in Smackover and up to 1,500 ppm in South America). Generally, water must have a minimum of 80 ppm lithium for feasible recovery, and commercial applications in the Permian may be scarce. Hopefully, a combination of high water-volumes, which the Permian has in abundance, and large-scale efficient DLE will yield feasible results in some areas.
Lithium and other mineral extraction could indirectly relieve SWD issues. The water remains after extraction, but if produced water has value, opportunities for reuse rather than disposal would become economically feasible.