{{short description|Water as a byproduct of oil production}} [[File:Marcellus Shale Gas Drilling Tower 1 crop.jpg|thumb|A shale gas well being drilled by a drilling rig in Pennsylvania]] '''Produced water''' is a term used in the oil industry or geothermal industry to describe water that is produced as a byproduct during the extraction of oil and natural gas,<ref>{{Cite journal |last1=Klemz |first1=Ana Caroline |last2=Weschenfelder |first2=Silvio Edegar |last3=Lima de Carvalho Neto |first3=Sálvio |last4=Pascoal Damas |first4=Mayra Stéphanie |last5=Toledo Viviani |first5=Juliano Cesar |last6=Mazur |first6=Luciana Prazeres |last7=Marinho |first7=Belisa Alcantara |last8=Pereira |first8=Leonardo dos Santos |last9=da Silva |first9=Adriano |last10=Borges Valle |first10=José Alexandre |last11=de Souza |first11=Antônio Augusto U. |last12=Guelli U. de Souza |first12=Selene M. A. |date=2021-04-01 |title=Oilfield produced water treatment by liquid-liquid extraction: A review |url=https://www.sciencedirect.com/science/article/pii/S092041052031336X |journal=Journal of Petroleum Science and Engineering |language=en |volume=199 |article-number=108282 |doi=10.1016/j.petrol.2020.108282 |bibcode=2021JPSE..19908282K |s2cid=233073324 |issn=0920-4105|url-access=subscription }}</ref> or used as a medium for heat extraction.<ref name=":0">{{Cite journal |last1=Su |first1=Shujuan |last2=Li |first2=Ying |last3=Chen |first3=Zhi |last4=Chen |first4=Qifeng |last5=Liu |first5=Zhaofei |last6=Lu |first6=Chang |last7=Hu |first7=Le |date=2022-06-01 |title=Geochemistry of geothermal fluids in the Zhangjiakou-Penglai Fault Zone, North China: Implications for structural segmentation |url=https://www.sciencedirect.com/science/article/pii/S1367912022001419 |journal=Journal of Asian Earth Sciences |language=en |volume=230 |article-number=105218 |doi=10.1016/j.jseaes.2022.105218 |bibcode=2022JAESc.23005218S |s2cid=248019293 |issn=1367-9120|url-access=subscription }}</ref><ref>{{Cite journal |last1=Song |first1=Guofeng |last2=Song |first2=Xianzhi |last3=Ji |first3=Jiayan |last4=Wu |first4=Xiaoguang |last5=Li |first5=Gensheng |last6=Xu |first6=Fuqiang |last7=Shi |first7=Yu |last8=Wang |first8=Gaosheng |date=2022-03-01 |title=Evolution of fracture aperture and thermal productivity influenced by chemical reaction in enhanced geothermal system |url=https://www.sciencedirect.com/science/article/pii/S0960148121018632 |journal=Renewable Energy |language=en |volume=186 |pages=126–142 |doi=10.1016/j.renene.2021.12.133 |bibcode=2022REne..186..126S |s2cid=245682408 |issn=0960-1481|url-access=subscription }}</ref><ref>{{Cite journal |last1=Tao |first1=Jian |last2=Yang |first2=Xing-Guo |last3=Ding |first3=Pei-Pei |last4=Li |first4=Xi-Long |last5=Zhou |first5=Jia-Wen |last6=Lu |first6=Gong-Da |date=2022-06-05 |title=A fully coupled thermo-hydro-mechanical-chemical model for cemented backfill application in geothermal conditions |url=https://www.sciencedirect.com/science/article/pii/S0013795222001284 |journal=Engineering Geology |language=en |volume=302 |article-number=106643 |doi=10.1016/j.enggeo.2022.106643 |bibcode=2022EngGe.30206643T |s2cid=247848365 |issn=0013-7952|url-access=subscription }}</ref><ref>{{Cite journal |last1=Li |first1=S. |last2=Wang |first2=S. |last3=Tang |first3=H. |date=2022-03-01 |title=Stimulation mechanism and design of enhanced geothermal systems: A comprehensive review |url=https://www.sciencedirect.com/science/article/pii/S1364032121011795 |journal=Renewable and Sustainable Energy Reviews |language=en |volume=155 |article-number=111914 |doi=10.1016/j.rser.2021.111914 |bibcode=2022RSERv.15511914L |s2cid=244823147 |issn=1364-0321|url-access=subscription }}</ref> Water that is produced along with the hydrocarbons is generally brackish and saline in nature.<ref>{{Cite journal|last1=D. Atoufi|first1=Hossein|last2=Lampert|first2=David J.|date=2020|title=Impacts of Oil and Gas Production on Contaminant Levels in Sediments|journal=Current Pollution Reports|language=en|volume=6|issue=2|pages=43–53|doi=10.1007/s40726-020-00137-5|bibcode=2020CPolR...6...43D |s2cid=211080984|issn=2198-6592|via=Springer Nature}}</ref> Oil and gas reservoirs often have water as well as hydrocarbons, sometimes in a zone that lies under the hydrocarbons, and sometimes in the same zone with the oil and gas. In geothermal plants, the produced water is usually hot. It contains steam with dissolved solutes and gases, providing important information on the geological, chemical, and hydrological characteristics of geothermal systems.<ref name=":0" /> Oil wells sometimes produce large volumes of water with the oil, while gas wells tend to produce water in smaller proportions.
As an oilfield becomes old, its natural drive to produce hydrocarbons decreases leading to decline in production. To achieve maximum oil recovery, waterflooding is often implemented, in which water is injected into the reservoirs to help force the oil to the production wells. In offshore areas, sea water is used. In onshore installations, the injected water is obtained from rivers, treated produced water, or underground. Injected water is treated with many chemicals to make it suitable for injection. The injected water eventually reaches the production wells, and so in the later stages of water flooding, the produced water's proportion ("cut") of the total production increases.<ref>{{cite journal |last1=Mesa |first1=Sandra Liliana |last2=Orjuela |first2=Johana Milena |last3=Ortega Ramírez |first3=Angie Tatiana |last4=Sandoval |first4=Juan-Andrés |title=Revisión del panorama actual del manejo de agua de producción en la industria petrolera colombiana |journal=Gestión y Ambiente |date=1 January 2018 |volume=21 |issue=1 |pages=87–98 |doi=10.15446/ga.v21n1.69792 |url=https://www.academia.edu/37606464 |access-date=23 December 2024|doi-access=free }}</ref>
==Water quality== The water composition ranges widely from well to well and even over the life of the same well. Much produced water is brine, and most formations result in total dissolved solids that are too high for beneficial reuse. In oil fields, almost all produced water contains oil and suspended solids.<ref>{{cite web |url=https://www.americangeosciences.org/critical-issues/faq/what-produced-water |title= What is produced water? |work=American Geosciences Institute - AmericanGeoSciences.org |date= 10 June 2016 |access-date=December 31, 2023}}</ref> Some produced water contains heavy metals and traces of naturally occurring radioactive material (NORM), which over time deposits radioactive scale in the piping at the well.<ref>{{cite web |url=http://aqwatec.mines.edu/produced_water/intro/pw/ |title=About Produced Water |author=<!--Staff writer(s); no by-line.--> |website=Advanced Water Technology Center |publisher=Colorado School of Mines |location=Golden, CO |access-date=2016-05-14}}</ref><ref>{{cite journal |last1=Igunnu |first1=Ebenezer T. |last2=Chen |first2=George Z. |title=Produced water treatment technologies |journal=International Journal of Low-Carbon Technologies |date=September 2014 |volume=9 |issue=3 |pages=157–177 |doi=10.1093/ijlct/cts049 |doi-access=free }}</ref> Metals found in produced water include zinc, lead, manganese, iron, and barium.<ref name="Veil">{{cite report |last1=Veil |first1=John A. |last2=Puder |first2=Markus G. |last3=Elcock |first3=Deborah |last4=Redweik |first4=Robert J. |date=2004 |title=A white paper describing produced water from production of crude oil, natural gas, and coal bed methane |url=http://www.evs.anl.gov/publications/doc/ProducedWatersWP0401.pdf |publisher=US Argonne National Laboratory |location=Argonne, IL |id=ANL/EA/RP-112631}}</ref> In geothermal fields, produced waters are classified into 3 chemical types: HCO3-Ca⋅Mg, HCO3-Na and SO4⋅Cl-Na.<ref name=":0" /> The U.S. Environmental Protection Agency (EPA) in 1987 and 1999 indicates that during drilling and operations, additives may be used to reduce solid deposition on equipment and casings. Water produced from underground formations for geothermal electric power generation often exceeds primary and secondary drinking water standards for total dissolved solids, fluoride, chloride, and sulfate.
==Water management== [[File:Figure 2- Injection Wells for Produced Water (6847703607).jpg|thumb|Diagram of an injection well for disposal of produced water]] Water is required for both traditional geothermal systems and EGS throughout the life cycle of a power plant. For traditional projects, the water available at the resource is typically used for energy generation during plant operations.<ref>{{Cite report |last1=Clark |first1=C. E. |last2=Harto |first2=C. B. |last3=Sullivan |first3=J. L. |last4=Wang |first4=M. Q. |date=2010-09-17 |title=Water use in the development and operation of geothermal power plants |url=https://www.osti.gov/biblio/1013997 |language=ENGLISH |doi=10.2172/1013997|osti=1013997 }}</ref>
Historically, produced water was disposed of in large evaporation ponds. However, this has become an increasingly unacceptable disposal method from both environmental and human health perspectives. Produced water is considered industrial waste.<ref>{{cite journal |last1=Ibrahim |first1=Muhammad |last2=Nawaz |first2=Muhammad Haq |last3=Rout |first3=Prangya Ranjan |last4=Lim |first4=Jun-Wei |last5=Mainali |first5=Bandita |last6=Shahid |first6=Muhammad Kashif |title=Advances in Produced Water Treatment Technologies: An In-Depth Exploration with an Emphasis on Membrane-Based Systems and Future Perspectives |journal=Water |date=18 August 2023 |volume=15 |issue=16 |page=2980 |doi=10.3390/w15162980 |doi-access=free }}</ref>
The broad management options for re-use are direct injection, environmentally acceptable direct-use of untreated water, or treatment to a government-issued standard before disposal or supply to users. Treatment requirements vary throughout the world. In the United States, these standards are issued by the U.S. Environmental Protection Agency (EPA) for underground injection<ref name="EPA Regs">{{cite web |title=Underground Injection Control Regulations and Safe Drinking Water Act Provisions |url=https://www.epa.gov/uic/underground-injection-control-regulations-and-safe-drinking-water-act-provisions |date=2016-10-17 |publisher=U.S. Environmental Protection Agency (EPA) |location=Washington, DC}}</ref><ref>{{cite web |title=General Information About Injection Wells |url=https://www.epa.gov/uic/general-information-about-injection-wells |date=2016-09-06 |publisher=EPA}}</ref> and discharges to surface waters.<ref>{{cite web |title=Oil and Gas Extraction Effluent Guidelines |url=https://www.epa.gov/eg/oil-and-gas-extraction-effluent-guidelines |date=2019-05-15 |publisher=EPA}}</ref> Although beneficial reuse for drinking water and agriculture have been researched, the industry has not adopted these measures due to cost, water availability, and public health concerns.<ref>{{cite journal |last1=Dawoud |first1=Hana D. |last2=Saleem |first2=Haleema |last3=Alnuaimi |first3=Nasser Abdullah |last4=Zaidi |first4=Syed Javaid |title=Characterization and Treatment Technologies Applied for Produced Water in Qatar |journal=Water |date=13 December 2021 |volume=13 |issue=24 |page=3573 |doi=10.3390/w13243573 |doi-access=free |hdl=10576/56639 |hdl-access=free }}</ref>
Gravity separators, hydrocyclones, plate coalescers, dissolved gas flotation, and nut shell filters are some of the technologies used in treating wastes from produced water.<ref name="EPA 1993">{{cite report |date=1993 |title=Development Document for Final Effluent Limitations Guidelines and New Source Performance Standards for the Offshore Subcategory of the Oil and Gas Extraction Point Source Category |url=https://www.epa.gov/eg/oil-and-gas-extraction-effluent-guidelines-documents-offshore-facilities |publisher=EPA |pages=IX-15–IX-19 |id=EPA-821-R-93-003}}</ref>
==Radioactivity== The use of produced water for road deicing has been criticized as unsafe.<ref>{{cite journal |last1=Bain |first1=Daniel J |last2=Cantlay |first2=Tetiana |last3=Garman |first3=Brittany |last4=Stolz |first4=John F |title=Oil and gas wastewater as road treatment: radioactive material exposure implications at the residential lot and block scale |journal=Environmental Research Communications |date=1 November 2021 |volume=3 |issue=11 |page=115008 |doi=10.1088/2515-7620/ac35be|doi-access=free |bibcode=2021ERCom...3k5008B }}</ref>
In January 2020, ''Rolling Stone'' magazine published an extensive report about radioactivity content in produced water and its effects on workers and communities across the United States. It was reported that brine sampled from a plant in Ohio was tested in a University of Pittsburgh laboratory and registered radium levels above 3,500 pCi/L. The Nuclear Regulatory Commission requires industrial discharges to remain below 60 pCi/L for each of the most common isotopes of radium, radium-226 and radium-228.<ref>{{Cite magazine |last=Nobel |first=Justin |url=https://www.rollingstone.com/politics/politics-features/oil-gas-fracking-radioactive-investigation-937389/ |title=America's Radioactive Secret |date=21 January 2020 |magazine=Rolling Stone}}</ref>
==See also== * Industrial waste water treatment * Oil–water separator
==References== {{Reflist}}
{{Wastewater}}
Category:Petroleum production Category:Water pollution Category:Natural gas