The goal of this project is to evaluate several desalination technologies so that brackish waters produced in the course of coalbed natural gas (CBNG) production can be treated to meet irrigation and rangeland rehabilitation uses. This included characterization of CBNG produced water in the San Juan and Raton basins, laboratory work on novel desalination technologies, and emphasizing the pretreatment of the produced brackish water.
Sandia National Laboratories
Biosphere Environmental Sciences and Technologies
CBNG accounts for about 7 percent of total U.S. natural gas production. Spurred by increased energy needs, advantages of natural gas regarding environmental concerns, and exploration and production technology advances, CBNG production could easily double in the next 8-10 years, accounting for up to 15 percent of the Nation's total natural gas production. CBNG operators face increasing environmental challenges and costs in hauling off and disposing produced water (from $3 to more than $4 per barrel in the San Juan Basin) that threaten to hobble further CBNG development.
CBNG fields such as those in the San Juan and Raton basins generally have relatively little infrastructure, especially when compared with other fields where complete gathering systems exist. In these relatively new CBNG areas, desalination treatment of produced water may have to be done well pad by well pads, or by gathering the produced CBNG water from two or three adjacent pads. Because these isolated pads are off the electric grid, providing solar power to the desalination effort seems appropriate.
At the outset, an industry advisory group was formed to help steer the project. CBNG produced water was characterized in the San Juan Basin, with more-limited sampling conducted in the Raton Basin. Two novel desalination technologies have been examined in the laboratory: artificial zoeolites (Permutite and Hydrotalcite) and capacitive deionization (CDI).
Extensive studies have been made in the laboratory on a (Capacitive Deionization) CDI laboratory demonstration leased to Sandia that includes performance optimization, analysis of yields and removal efficiencies, cost performance, and sizing of an appropriate photovoltaic (PV) system to power this technology at remote well sites. Exploiting this technology has been one of the main thrusts of this project.
Progress was made on removing divalent ions from an inlet stream of produced water and removing organic materials with membranes. Use of produced water for jump-starting/germinating grasses for rangeland and grassland improvement looks very promising.
San Juan Basin water quality was characterized. Limited water quality characterization has been accomplished in the Raton Basin.
Researchers optimized procedures for synthesizing artificial materials for desalination and examined regeneration of these materials. An initial run using ~11,000 TDS CBNG water was promising, resulting in desalinated water at ~600 TDS. Cost estimates of the desalination process were generated, and scale up to a pilot system was considered-including using a PV system to power the system.
Thorough laboratory studies on desalination of CBNG water with CDI technology were accomplished with ~3,000 and ~5,000 TDS CBNG (San Juan Basin) produced water. After optimizing the demonstration unit's performance, researchers determined the removal efficiencies of many ions and analyzed energy consumption and yields for this CDI technology. The zoelite first technology was too incipient to use in a pilot demonstration and the upshot of the work of the CDI technology is annotated in the present status section below.
Using nanofiltration alone, researchers removed divalent ions ~12,000 TDS produced water from gas wells in New Mexico's Permian Basin. Ultrafiltration has been used successfully to remove the vast majority of organic materials from this same source of produced water. Removal of H2S from the inlet stream of produced water is underway.
The hardiest grasses for the arid Southwest climate were identified. A matrix of these hardy grasses was spot-watered with various TDS values of CBNG produced water to see which of these grasses would best sprout when irrigated with CBNG produced water. The sprouting of grasses watered with produced water is encouraging. Sodium absorption ratios and conductivity values were within safe limits for the grasses planted at all sites watered with CBNG produced water by New Mexico State Agricultural Experiment Station Farmington. Chief Intermediate Wheatgrass Hy-Crest Crested Wheatgrass and San Louis Slender Wheatgrass had the best overall rating for stands of grass for seedlings watered with CBNG produced water.
Discussions were held over many months with BLM’s Farmington, NM, field office. BLM felt that while it allowed the New Mexico State Agricultural Experiment Station (NMSAES) at Farmington to water seedlings with produced water on a pilot basis, the standards for treated water should be significantly higher. A TDS level of ~1,500 was suggested for the water treated. BLM has given the project guidance that 1,500 TDS desalinated CBNG water may be put on the soil on a pilot basis. The water desalinated in the pilot operation will be used to water the grasses already planted on the well pad of the pilot operation.
Very recently, as a prelude to a field demonstration, sampling of the produced water from the Conoco Phillips Test well (where the desalination field operation is to commence) has been accomplished. The analysis helped determine the final experiment design. Design work has commenced for the mechanical pre-filter system, and a detailed safety document was written.
The environmental problems posed by the brackish CBNG produced water are severe. Portions of this brackish CBNG produced water so that it can be used beneficially, thus opening a way to help sustain and even increase the Nation's CBNG production. The technology can be applied to treating saline water in general. This project could allow the reuse of impaired water in water-intensive sectors such as agriculture and livestock grazing.
Discussions were held over many months with the US BLM Farmington, New Mexico Field Office. They felt that while they allowed the New Mexico State Agricultural Experiment Station, Farmington, to water seedlings on grasses on the Conoco Phillips pad with produced water on a pilot basis, the standards for treated water should be higher. A TDS Level of ~1500 was suggested for the water treated with capacitive deionization. The water desalinated in the pilot operation will be used to water the grasses already planted on the well pad of the pilot operation.
Soil Conductivity and Sodium Absorption Ratio values remain under critical limits for forage production for the grasses planted at all sites watered with CBNG produced water by the New Mexico State Agricultural Experiment Station, Farmington. Chief Intermediate Wheatgrass Hy-Crest Crested Wheatgrass and San Louis Slender Wheatgrass had the best overall rating for stands of grass for seedlings watered with CBNG produced water.
The Pilot Operation is going to be taken to the field the summer of 07. More details are provided in the bullets below.
Anticipated DOE/NGOTP Contribution: $840,000
ConocoPhillips Contribution: >$100, 000
State of New Mexico Contribution: ~$150,000
DOE Southwest Regional Partnership on Carbon Sequestration Contribution, FY 07: $50,000
Sandia Desalination Program: ~$150,000
Hoffman, G.K., and Brister, B.S., New Mexico Raton Basin Coalbed Methane Play, New Mexico Geology, Vol. 25, No. 4, November 2003, pp. 95-110.
Brister, B.S., et al., Coalbed Methane in New Mexico, published by the New Mexico Bureau of Geology at New Mexico Tech, Winter 2004.
Richard N. Arnold, "Regeneration of Pipeline Right-of Way or Well Sites with Cool and Warm Season Cultivar's and Forbes for Palatability, Stand Establishment and Erosion Control in the Intermountain Region of Northwest New Mexico," New Mexico State University Agricultural Research Center, Farmington NM, February 2005.
Hightower, M., et al., Managing Coal Bed Methane Produced Water for Beneficial Uses, Initially Using the San Juan and Raton Basins as a Model, (Interim Progress Report),
Pless, J., et al., Desalination of Brackish Ground Waters and Produced Waters using In-situ Precipitation, Sandia National Laboratories Report 2004-3908, August 2004.
Donahe et al: “Capacitive Deionization for Inland Produced Water Desalination Analysis of Economics, Technical Performance Optimization, and Approximate Cost Behavior,” Sandia Report, SAND 2005-4520P, Given at Intern Symposium and WRRI, Socorro, Aug 05.
Kottenstette, Richard and Sattler, A.R. “The Sandia Desalination Program and Capacitive Deionization Technology,” Sandia Report, SAND 2006-1250A, given at Four Corners Oil and Gas Show, Farmington, May 06.