5

Remediation and Reclamation

This chapter explores key considerations and techniques for remediating failed orphan wells and reclaiming the associated surface area, including whether modern plugging methods are satisfactory to support future surface and subsurface use. Depending on the condition and specifications of the original wellbore (e.g., casing, hole size) and the resource potential of the local area, a well may be repurposed once oil and natural gas production has ceased. Future use is not the only goal of remediation and reclamation, of course, and reuse can have significant challenges. If a plug has failed, steps have to be taken to repair or remediate the wellbore and clean up or reclaim any surface area that may have been contaminated. In most cases, operators are required to reclaim the surface and return it to the state it was in prior to hydrocarbon extraction activity.¹

The chapter first identifies subsurface considerations that may impact the remediation of an orphan well. It then discusses surface and site reclamation issues regarding orphan wells. The chapter returns to the topic of well and surface reuse and outlines some of the recent research on possibilities for reuse.

SUBSURFACE CONSIDERATIONS

Many subsurface issues that can contribute to plug failure also impact the remediation process. Chapter 3 examines the subsurface characteristics that influence the type of operated well used, including its construction specifications, the subsequent changes to the surface and subsurface that can take place over the lifetime of a producing

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¹ Note that the term “remediation” can also be used in terms of surfaces. “Reclamation” will be used here in reference to surface reclamation (as used by the Bureau of Land Management, e.g., https://www.blm.gov/programs/energy-and-minerals/oil-and-gas/reclamation), and “remediation” will be used here in association with the wellbore and subsurface.

well, and the resulting situation presented when the well is plugged. These “lifetime” circumstances are more difficult to reconstruct if a well is orphan and lacks modern documentation. This chapter focuses on the impact such circumstances may have on the direct remediation of failed plugging attempts.

Reservoir Characteristics

Prior to any remediation or reclamation efforts, it is important that a wellbore evaluation include an examination of the porosity and permeability of formations penetrated by the well (Lupardus et al. 2023). These characteristics can influence to what degree contaminants could migrate across zones, thereby helping to determine efforts needed for remediation and reclamation and whether the wellbore can be reused (Jello and Baser 2022). Information from well logs, including porosity logs (or, for some older wells, microlog suites), can be used to better understand the subsurface environment. Given their age, many orphan wells have never been logged, or their logs have been lost. When logs are missing, it is important to make every effort to characterize the reservoir by either analyzing nearby offset wells (i.e., nearby wells that share common geological or reservoir characteristics) or inferring conditions based on knowledge of regional reservoir characteristics (NASEM 2025).

Addressing reservoir compaction is also important, because the loss of pore pressure as oil and gas reservoirs are depleted can lead to increased effective pressure (due to an increase in the total load or stress from the rock overburden) and therefore reservoir compaction (Sharifi 2023). As Sharifi (2023, p. 2440) notes, “reservoir compaction can cause porosity loss, wellbore instability, fault reactivation, and even subsidence at the surface (Gurevich and Chilingarian 1995; Settari 2002; Hagin and Zoback 2004; Jelmert and Toverud 2018; Gazzola et al. 2023).” In addition, the type of hydrocarbon (e.g., heavy oil, light oil, wet gas, dry gas) can influence fluid behavior during pressure depletion and therefore affect remediation decisions (DiGiulio 2024).

Certain subsurface formation properties may contribute to the corrosion of downhole wellbore equipment, including the presence of salt and/or anhydrite, brines, carbon dioxide, and hydrogen sulfide (previously discussed in Chapter 3). Specific remediation strategies have been proposed for wells burdened with excessive salt deposition in the wellbore (e.g., cold-water removal, hot washing, chemical salt prevention) (Wang et al. 2023), but their efficacy and applicability may be limited in wells that were orphaned long ago, allowing cumulative salt deposition to continue over time.

Produced waters, especially those with low pH levels, may also negatively impact wellbore integrity and remediation efforts because of their corrosive potential. Multiple studies have indicated that the relative abundance of certain elements and organic compounds in produced waters reflects not only the well location but also the geological formation from which the fluids are derived (Al-Ghouti et al. 2019; Sanchez-Rosario and Hildenbrand 2022). These fluids can contain high levels of sodium and chlorine ions that can cause corrosion within a wellbore.

The biogeochemical makeup of certain produced waters can yield an optimal environment for a range of microorganisms that can also lead to downhole corrosion

(Sanchez-Rosario and Hildenbrand 2022), thereby complicating remediation efforts. Examples range from aerobic to anaerobic microbes, including sulfate-reducing bacteria,² iron-oxidizing bacteria,³ acid-producing bacteria, sulfur-oxidizing bacteria,⁴ and extremophiles. Sulfate-reducing bacteria may lead to souring of natural gas, and iron-oxidizing bacteria can cause downhole corrosion (de Oliveira et al. 2021; Mohan et al. 2014). Additionally, sulfur-oxidizing bacteria can promote downhole corrosion (principally in carbon steel) by triggering the oxidation of sulfur compounds to sulfate, ultimately generating sulfuric acid (de Oliveira et al. 2021).

Faulting and Subsurface Fractures

Faults and other subsurface fractures can be a major barrier to remediating orphan oil and gas wells, just as they can be a contributing factor to plug failures. Complications from either a natural or induced fracture network could compromise a remedial plugging operation if the subsurface environment has not been properly characterized or subsurface data are unavailable, which may be the case for many orphan wells (DiGiulio 2024). Studies have emphasized that the amount of fault throw relative to reservoir thickness and pore pressure change needs to be evaluated when assessing fault reactivation risks, and that faults with large throw–reservoir thickness ratios have higher reactivation risks (Bisdom and Chan 2024). This phenomenon holds true not only for remediation and reclamation efforts but also if an orphan well is repurposed for geologic carbon sequestration and energy storage (Bisdom and Chan 2024).

Many states have regulations to mitigate seismicity and aid in the reclamation process. For example, the Railroad Commission of Texas (n.d.) suspended or curtailed injection volumes for deep disposal wells in high-seismicity areas to limit the amount of waste fluid being injected underground. In addition, it designated specific geographic areas with high seismic activity as Seismicity Response Areas, which allows for more stringent regulatory oversight and control over injection operations (Railroad Commission of Texas, n.d.). Likewise, the Oklahoma Corporation Commission manages seismicity from injection wells by limiting deep wastewater disposal volumes, monitoring and shutting down wells in high-activity areas, and using a “traffic light” system that assigns colors based on seismic risk (Murray et al. 2023). While these issues may not directly impact an orphan well, they must be considered, since injection into nearby wells could induce seismic activity and create the potential for new methane and contaminant pathways to the surface.

SURFACE AND NEAR-SURFACE CONSIDERATIONS

While many parts of this section address subsurface factors, significant issues at the surface also need to be evaluated when considering methods for remediating orphan oil

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² For example, desulfomicrobium, desulfovibrio, desulfohalubium, desulfobacter.

³ For example, desulfuromusa, pelobacter, malonomonas, desulfuromonas.

⁴ For example, Acidithiobacillus caldus, A. thiooxidans, A. albertensis.

and gas wells. This section addresses surface and near-surface contamination reclamation and potential repurposing of well sites.

Surface Contamination

Orphan well sites may exhibit recent or past releases of oil, produced water, or other fluids. After plugging and removing any production equipment, the site is evaluated for contaminated soils. A reclamation plan considers the time required for applying certain corrective techniques successfully. For example, excavation and disposal of contaminated soil may be more pragmatic than natural attenuation or bioreclamation, which could take years if site contamination is significant (Lupardus et al. 2023).

Site Reclamation Best Practices

The goal of most site reclamation is to return the land to as near natural conditions as possible while considering surrounding land use and landowner intent (Lupardus et al. 2023). However, jurisdictions’ goals and requirements will differ (DiGiulio 2024). A jurisdiction may require meeting certain standards, or it may permit leaving the site in accordance with the landowner’s instruction (Lupardus et al. 2023). Orphan well locations that have been undisturbed for long periods may have experienced some level of natural reclamation (Azubuike et al. 2016). If that meets the jurisdiction’s standards for site reclamation, minimizing new disturbance during the plugging process will reduce the reclamation efforts and could significantly reduce the time and cost of final site reclamation. This would be especially true in regions where weather and soil conditions make reclamation difficult.

Site reclamation projects could also prioritize the highest and best-use opportunity of a contaminated site, especially when the overall contamination risk has been deemed low. Private landowners may provide input to ensure that final reclamation standards match their current or intended use of the area (Simmers et al. 2024). For example, they may not want reclamation if their intended use will further disturb the site. However, potential future impacts beyond a landowner’s interests need to be considered (Lupardus et al. 2023). For example, if in situ and/or ex situ remediation would inhibit future use of the surface near a well site, then subsurface studies to accurately identify potential soil–groundwater contaminant pathways become very important. Coordination with landowners includes starting communication early and documenting their wishes so the well records are clear regarding the completed reclamation (NASEM 2025). Cooperation to reclaim a site in accordance with landowners’ instructions could save money that could then be applied to other plugging or reclamation projects.

Sites for new oil and gas development are commonly assessed during the Application for Permit to Drill process to develop appropriate site mitigation and reclamation plans (Lupardus et al. 2023). A pre-development plan includes examining local geology, soil types, elevation, precipitation, temperatures, local ecology, and other conditions, which will be used to lay out expectations for final site reclamation. Even though most orphan well sites do not have such a plan, similar data and standards can aid in the final

reclamation plan. The plan includes a timeline, because time-sensitive activities, such as soil preparation and seeding, are essential to successful reclamation. For example, seedbeds are best seeded closely after preparation and when environmental conditions are optimal (Lupardus et al. 2023). Areas with conditions that are relatively conducive to reclamation, such as higher-quality soils, more precipitation, lower elevation, and warmer temperatures, may not require as much planning for successful reclamation efforts as would areas with more adverse conditions. In areas with high elevation, lower temperatures, poor soils, little topsoil, aridity, or other issues, the timing of reclamation activities can be crucial to site recovery (Lupardus et al. 2023).

Several federal agencies have developed guidance and best practices for reclamation operations and monitoring for oil and gas sites located on federal lands. For example, Chapter 2840 of the U.S. Forest Service Manual 2800 has standards for managing reclamation (USDA Forest Service 1990). The U.S. Geological Survey, with the Bureau of Land Management, recently updated its guidelines to include standards for reclamation, revegetation, and abandonment that are intended to ensure that land and water character and productivity are restored (Lupardus et al. 2023). These documents include best-management practices for soil preparation, soil amendments, erosion control, seeding, and other activities and can thus serve as resources for many jurisdictions.

RECLAMATION METHODS

Reclamation is crucial for mitigating environmental damage and restoring ecological health. Methods used to clean up contamination depend on the type and quantity of the contaminant(s), site characteristics (e.g., geology, hydrology, hydrogeochemistry, hydrogeology), and location in the soil and/or groundwater (Azubuike et al. 2016). For example, cleaning up oil spills involves multiple steps. Immediate responses include containing the spill and recovering the oil—soil berms can contain the oil so it cannot spread further on the land surface or flow downhill to surface water, and booms can be deployed if the oil was released to surface water. Once the oil is contained, it can be recovered using vacuum trucks, skimmers or pumps, or sorbents (Allison and Mandler 2018). Reclamation of the soil begins once recovery of the spilled oil is complete, and methods used will be determined by the volume of oil that has infiltrated the soil. Natural processes, such as evaporation, oxidation, and biodegradation, can also remove or reclaim oil from the environment (EPA 1999). Physical methods include excavation, pressure washing, or cutting and removing vegetation. Light coatings of oil on the surface of the soil and vegetation can be monitored for natural attenuation or, under appropriate conditions, burned off. When oil has pooled or seeped deep into the ground, the soil can be excavated and then disposed of or moved to a treatment cell for bioreclamation.

Reclamation methods for soil and groundwater can be separated into two broad categories. In situ treatment happens at the site; for ex situ treatment, the contaminated soil or water is removed and treated elsewhere. The latter results in more effective and uniform treatment, but the volume of material and containment of the contamination can present challenges (Utting and Heshka 2019). In situ treatment requires no excavation, resulting in cost savings (FRTR 2007); however, it commonly takes longer and can

vary in effectiveness. Multiple parameters, not only a well’s status as orphan, influence which method is used. Because they are more cost-effective than ex situ methods, this section focuses on in situ treatments.

Groundwater Treatment

Multiple documented cases show that produced water and, in some instances, petroleum-related contaminants have leaked from oil and gas production activities into freshwater aquifers, creating persistent plumes that required long-term, costly subsurface remediation and containment efforts (Peterman et al. 2010; Rubin et al. 2001; Thamke and Smith 2014). Various techniques can be used to treat contaminated groundwater. These include air stripping and filtration. Air stripping—also known as air sparging—brings contaminated water into contact with air to transfer volatile contaminants from the liquid (water) phase to the gaseous (air) phase, effectively separating the contaminants from the water. Filtration uses permeable reactive barriers, such as granulated activated carbon filters (Al-Hashimi et al. 2021).

Remediation of Soils Impacted by Produced Waters

Several practices are available to remediate soils impacted by produced waters (including brine). Many of these are in situ treatments, using water to leach salts or amendments such as gypsum to restore the soil structure. Common remediation practices include the following (Green et al. 2020; Sublette 2017):

• Soil washing/dilution: The excess salinity of produced waters can create an osmotic imbalance, which can reduce water uptake by plant roots and lead to plants going into drought stress despite abundant water in the soil. Fresh water can be used to mobilize salts and flush them downward in the soil profile.
• Ion exchange soil amendments: Sodicity (an excess of sodium relative to calcium and magnesium found in produced waters) can cause clay particles to disperse, leading to soil structure breakdown, poor water infiltration, surface crusting, and reduced aeration, all of which can hinder plant growth. Gypsum can be applied to replace sodium with calcium, reducing sodicity and improving soil structure. Organic amendments, such as manure or straw, can also be used.
• Soil extraction methods (ex situ): For sites that are contaminated with salts, situated near important water resources, or incompatible with in situ remediation methods, soil can be excavated and removed. However, this may require heavy equipment that can damage adjacent non-contaminated soils through compaction and vegetation removal. Potential for contact with buried infrastructure near the wellbore could also limit soil extraction.

In Situ Bioremediation

Encouraging the growth of bacteria to break down contaminants in the subsurface is another approach. Bioremediation uses microorganisms and plants to consume or transform contaminants into other chemicals. Bacteria that are native to the soil or water may degrade a contaminant, or a different bacterium that is known to consume the contaminant can be added. Alternatively, amendments, such as fertilizers, can be added to contaminated soil to enhance biodegradation (Azubuike et al. 2016).

In Situ Chemical Oxidation

In situ chemical oxidation can be used to treat soil and groundwater by destroying or transforming contaminants in place within the subsurface (Wei et al. 2022). This technique consists of injecting oxidants and additives into a subsurface zone, which then react with contaminants and lead to their breakdown over time due to physical, chemical, and biological effects (Stroo et al. 2012). The method addresses a variety of contaminants, including benzene, toluene, ethylbenzene, and xylenes; total petroleum hydrocarbons; polyaromatic hydrocarbons; and organic pesticides (insecticides and herbicides). Oxidants have different lifetimes, mechanisms, and impacts on biodegradation that may affect the choice of oxidants, distribution of injection wells, and injection intervals (Silva et al. 2017).

Soil Vapor Extraction and Thermal Treatment

Soil vapor extraction is a method for in situ extraction of volatile contaminants (Meuser 2013). A vacuum is applied to the soil to increase volatilization of volatile organic compounds. It has been used as a remediation technology at multiple sites across the United States, including at more than 285 Superfund sites (Stewart et al. 2020). Another method is thermal treatment, which can be used to increase volatilization and breakdown of contaminants (Ding et al. 2019).

Monitored Natural Attenuation

Monitored natural attenuation is not a reclamation technology but a method for monitoring a site while contaminant concentrations decrease by natural processes. The concentrations and extent of contaminants are measured over time, based on the hypothesis that the concentrations will decrease without artificial intervention (Lundegard and Johnson 2006).

REUSE OF ORPHAN WELL SITES AND WELLBORES

Oil and gas sites cover significant acreage. In some places and under some circumstances, these surface sites could be repurposed for activities such as energy production as part of a reclamation strategy. Theoretically, many orphan oil and gas well sites may

be repurposed for wind and solar energy. A fraction of the wells can be redeveloped for use in geothermal energy production (Boutot and Kang 2025; Jello and Baser 2022; Meenakshisundaram et al. 2024; Santos et al. 2022), lithium extraction from oilfield and geothermal-produced water (Ettehadi et al. 2024; Huang et al. 2021; Kumar et al. 2019), and carbon capture and storage (DiGiulio 2024; Hoskin 2022; Yu et al. 2024).

An important consideration in possible well or well site reuse is that the well owner usually does not own the property, and a lease allowing exploration and production governs legal ownership. A different use of the subsurface or surface estate will require a new legal agreement with the landowner (private or government) in most cases. Therefore, significant reuse opportunities cannot be presumed. The following examples may be considered potential opportunities but not at-scale developments. Reuse opportunities that have not incorporated this challenging legal issue are best considered conceptual.

Orphan well sites often already have necessary infrastructure, such as access roads and well pads, that can reduce startup costs for renewable projects. Converting these sites to solar farms or using the infrastructure for wind energy storage could allow for reuse of already disturbed lands (Buto et al. 2010). Estimates suggest that orphan well sites in the United States and Canada could boost current solar capacity by more than 5 percent (Boutot and Kang 2025). The greatest solar capacity potential (8 MW each) is found in Ohio, Pennsylvania, and Kentucky; these states have a relatively high number of orphan wells (Boutot and Kang 2025). The wind capacity of orphan well sites in the United States and Canada has been estimated at more than 15 TW, which exceeds current installed capacity (Boutot and Kang 2025). The highest wind capacities are in Oklahoma (110 GW) (which also has many orphan wells), Ohio (85 GW), and Pennsylvania (70 GW) (Boutot and Kang 2025).

Research on the potential for repurposing idle and orphan oil and gas wells close to existing grid infrastructure has focused on activities such as natural gas storage, waste fluid disposal, or monitoring. These repurposed wells could be converted into utility-scale gravity energy storage systems, which rely on gravity and resulting kinetic energy to capture and release energy that can then be supplied to the grid (Sundeep et al. 2024; Tong et al. 2022).

Almost all reuse applications will require mechanical integrity and well-known subsurface configurations. Because the mechanical integrity of orphan wells—including that of the casing and cement—is often poorly known, reuse is unlikely to be a major opportunity (Meehan et al. 2025). Energy storage and geothermal heat production require relatively large wellbore diameters. Geothermal reuse involves moving significant volumes of fluids in both injection and production, and most opportunities are “closed-loop” technologies, which have not yet been proven at commercial scale for electric power generation. The vast majority of orphan wells are relatively shallow and, even if in areas of high temperature gradients, may not have sufficient reservoir temperatures to justify geothermal development; such applications would be limited to providing space or industrial heating (Meehan et al. 2025). While lithium and other commercially valuable chemicals may be extracted from subsurface produced water, few orphan wells have yet been tested.

An attractive reuse opportunity is subsurface monitoring of temperatures, pressure, subsurface strain, and other measurements that can be obtained from installing fiber optics in orphan wells (Ashry et al. 2021). It is unlikely that orphan wells would qualify as Class VI injection wells for carbon capture, utilization, and storage or monitoring wells in an injection reservoir, but they could be considered for monitoring wells above the active storage reservoir (Meehan et al. 2025).

CONCLUSION

Conclusion 5-1: Orphan well sites may exhibit releases of oil, produced water, or other fluids to the surface. In the subsurface, geologic characteristics such as porosity, permeability, fluid content, and faulting can impact the ability of contaminants to migrate across multiple zones within a wellbore and affect groundwater aquifers. Priorities for site reclamation include containing and preventing leaks and ensuring reclamation is achieved according to state regulatory requirements.