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Produced water (PW) is the largest waste stream associated with oil and gas (O&G) operations and contains petroleum hydrocarbons, heavy metals, salts, naturally occurring radioactive materials and any remaining chemical additives. In some areas in Wyoming, constructed wetlands (CWs) are used to polish PW downstream of National Pollutant Discharge Elimination System (NPDES) PW release points. In recent years, there has been increased interest in finding lower cost options, such as CWs, for PW treatment. The goal of this study was to understand the efficacy of removal and environmental fate of O&G organic chemical additives in CW systems used to treat PW released for agricultural beneficial reuse. To achieve this goal, we analyzed water and sediment samples for organic O&G chemical additives and conducted 16S rRNA gene sequencing for microbial community characterization on three such systems in Wyoming, USA. Three surfactants (polyethylene glycols, polypropylene glycols, and nonylphenol ethoxylates) and one biocide (alkyldimethylammonium chloride) were detected in all three PW discharges and >94% removal of all species from PW was achieved after treatment in two CWs in series. These O&G extraction additives were detected in all sediment samples collected downstream of PW discharges. Chemical and microbial analyses indicated that sorption and biodegradation were the main attenuation mechanisms for these species. Additionally, all three discharges showed a trend of increasingly diverse, but similar, microbial communities with greater distance from NPDES PW discharge points. Results of this study can be used to inform design and management of constructed wetlands for produced water treatment.
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This content will become publicly available on February 1, 2026
Biogenic hydrogen production from oil hydrocarbons at geological carbon storage conditions
We found that supercritical CO2 and the availability of protein-rich matter in depleted oil reservoirs can result in the biogenic production of H2 from oil hydrocarbons by indigenous microbial communities. Our experimental results support the hypothesis that a decrease in pH to acidic levels due to the dissolution of supercritical CO2 into the formation water and availability of protein-rich matter favors the activity of H2-producing microbial communities over the activity of H2-using microbial communities. To determine where, when, and how much H2 could be produced in a depleted oil reservoir injected with CO2 and produced water (PW) supplied with protein-rich matter, we simulated the biogenic production of H2 for the Morrow B sandstone reservoir. Simulations were conducted using CO2Bio, a program developed to simulate the multiphase bio-geochemical reactive transport of CO2-CH4-H2-H2S gases in geological carbon storage (GCS) sites. The microbiological capabilities of CO2Bio are validated against batch reaction experimental results. Our field-scale simulation results indicate that 154 – 1673 kg of H2 could be produced after 100 days of CO2 and PW co-injection into a single well of radial flow, and that sandstone reservoirs are more suitable than carbonate reservoirs to produce H2 from dissolved hydrocarbons. Based on the obtained experimental and simulation results, we propose a new H2 production method that couples GCS and PW disposal in depleted oil reservoirs to attenuate environmental and energy issues related to global warming derived from atmospheric pollution with CO2, risk of freshwater resources contamination with PW, and depletion of energy resources.
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- Award ID(s):
- 2041648
- PAR ID:
- 10567320
- Publisher / Repository:
- ScienceDirect
- Date Published:
- Journal Name:
- Energy Conversion and Management
- Volume:
- 325
- Issue:
- C
- ISSN:
- 0196-8904
- Page Range / eLocation ID:
- 119438
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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