Environmental Risk and Well Integrity of Plugged and Abandoned Wells

King, George E.; Valencia, Randy

doi:10.2118/170949-ms

Cited by 34 publications

(21 citation statements)

References 60 publications

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“…Recent measurements of methane emissions from abandoned oil and gas wells in Pennsylvania indicate that these wells may be a significant source of methane to the atmosphere (3). Across the United States, the number of abandoned oil/gas wells is estimated to be 3 million or more (4,5), and this number will continue to increase in the future. As of February of 2016, abandoned oil/gas wells remain outside of GHG emissions inventories, despite evidence that emissions may be substantial nationally.…”

mentioning

confidence: 99%

Identification and characterization of high methane-emitting abandoned oil and gas wells

Kang

Christian

Celia

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

159

151

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Recent measurements of methane emissions from abandoned oil/gas wells show that these wells can be a substantial source of methane to the atmosphere, particularly from a small proportion of high-emitting wells. However, identifying high emitters remains a challenge. We couple 163 well measurements of methane flow rates; ethane, propane, andn-butane concentrations; isotopes of methane; and noble gas concentrations from 88 wells in Pennsylvania with synthesized data from historical documents, field investigations, and state databases. Using our databases, we (i) improve estimates of the number of abandoned wells in Pennsylvania; (ii) characterize key attributes that accompany high emitters, including depth, type, plugging status, and coal area designation; and (iii) estimate attribute-specific and overall methane emissions from abandoned wells. High emitters are best predicted as unplugged gas wells and plugged/vented gas wells in coal areas and appear to be unrelated to the presence of underground natural gas storage areas or unconventional oil/gas production. Repeat measurements over 2 years show that flow rates of high emitters are sustained through time. Our attribute-based methane emission data and our comprehensive estimate of 470,000–750,000 abandoned wells in Pennsylvania result in estimated state-wide emissions of 0.04–0.07 Mt (1012g) CH4per year. This estimate represents 5–8% of annual anthropogenic methane emissions in Pennsylvania. Our methodology combining new field measurements with data mining of previously unavailable well attributes and numbers of wells can be used to improve methane emission estimates and prioritize cost-effective mitigation strategies for Pennsylvania and beyond.

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confidence: 99%

Identification and characterization of high methane-emitting abandoned oil and gas wells

Kang

Christian

Celia

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

159

151

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“…There is a large body of literature on wellbore integrity, in addition to oil and gas industry standards [17,18], considering environmental impacts of oil and gas development [3,4,[35][36][37] and potential leakage in geologic storage of carbon dioxide projects [2,5,6,38]. These studies show that wellbore integrity failures can occur due to a wide range of chemical and mechanical alterations or defects that could be caused by existing or injected fluids, oil and gas operations, and existing or induced geomechanical stresses [4].…”

Section: Wellbore Integritymentioning

confidence: 99%

“…Chemical alterations may also be promoted by earthquakes as changes in pore fluid pressure drive fluids with corrosive substances to the wellbore. To avoid leakage, wellbores typically contain numerous barriers including multiple layers of steel casing and cementing [3]. Nevertheless, leakage along a wellbore can occur within cemented zones, between cement and steel casing, and between cement and the neighboring rock formation [2,5].…”

Section: Wellbore Integritymentioning

confidence: 99%

“…Subsurface leakage via oil and gas wells are identified as a major concern in geologic storage of carbon dioxide projects and oil and gas production [1]. Failure in barriers to well leakage, or wellbore integrity issues, can occur due to thermal, chemical, and/or mechanical stresses during oil and gas production and other activities and create or enhance fluid leakage in and around wellbores [2][3][4][5]. Database analysis are used to estimate rates of wellbore integrity failures such as cement and casing impairment and to link these issues to well characteristics, spud date, well type and construction, production history, well location, geology, operator, abandonment method, oil price, and regulatory changes [6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

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Potential increase in oil and gas well leakage due to earthquakes

Kang

Dong

Liu

et al. 2019

Environ. Res. Commun.

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Earthquakes occurring naturally or induced by human activities can damage surface and subsurface infrastructure. Oil and gas wells represent a category of subsurface infrastructure that can act as leakage pathways connecting oil and gas reservoirs, groundwater aquifers, and the atmosphere. The integrity of these wells can be compromised through a wide range of processes and contribute to groundwater contamination, greenhouse gas emissions, and air quality degradation. We estimate the increase in such subsurface leakage potential due to seismic activity through geospatial analysis of 579,378 oil and gas well and 196,315 earthquake (magnitudes greater than 1.0) locations in Oklahoma, California, and British Columbia. We perform density-based clustering analysis and point density mapping using ArcGIS. We combine the well and earthquake point density maps to identify hot spots of joint high well and earthquake densities. We find that oil and gas wells and earthquakes are clustered in space, with densities reaching ∼60 wells per km 2 and ∼40 earthquakes per km 2 in California. There are at least two hot spots where these clusters overlap in each state/province. In Oklahoma and British Columbia, the hot spots are more correlated with earthquake densities; while, in California, the hot spots are more correlated with well densities. Our findings indicate the need to investigate the role of earthquakes on wellbore leakage through additional analysis of earthquake characteristics, wellbore attributes, improved data collection, and empirical field studies for all oil and gas wells, including those that are abandoned. In particular, large scale geospatial analysis establishing the scope of the problem and empirical field studies focusing on identified hot spots are needed to understand potential environmental impacts of earthquakes, especially those induced by oil and gas activities.

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“…Abandoned wells can cause leakages to the environment if they are not plugged and abandoned properly (King and Valencia, 2014), and it is important to ensure good sealing and maintain well integrity after abandonment. The objective of plug and abandonment (P&A) operations can thus be described asЉrestoring the cap rockЉ (Oil & Gas UK, 2015).…”

Section: Introductionmentioning

confidence: 99%

Long-Term Integrity of Well Cements at Downhole Conditions

Vrålstad

Todorović

Saasen

et al. 2016

Day 1 Wed, April 20, 2016

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The objective of plug and abandonment of wells can be described as Љrestoring the cap rockЉ. In that respect, the long-term integrity of the plugging material is crucial. I.e. it is important that the plugging material can resist downhole chemicals and otherwise withstand downhole conditions. In this paper, we have performed ageing tests with cement samples at relevant downhole conditions to determine the long-term integrity of well cement as plugging material. Portland cement samples with and without silica flour as additive have been separately exposed to crude oil, brine and H 2 S (in brine) at 100°C and 500 bar for 1, 3, 6 and 12 months. The long-term integrity of the samples was determined by measuring changes in weight, volume, mechanical strength and permeability, as well as physical appearance.It is seen from the results that the addition of a pozzolan such as silica has a significant impact on the long-term integrity of Portland cement, especially in a corrosive environment such as H 2 S. All the samples were affected by most of the different chemical environments, but the cement samples without silica were considerably more affected than the samples with silica as additive. Furthermore, the exposure to H 2 S in brine resulted in the formation of an unexpected white deposit, which precipitated both inside and outside the samples.

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Environmental Risk and Well Integrity of Plugged and Abandoned Wells

Cited by 34 publications

References 60 publications

Identification and characterization of high methane-emitting abandoned oil and gas wells

Identification and characterization of high methane-emitting abandoned oil and gas wells

Potential increase in oil and gas well leakage due to earthquakes

Long-Term Integrity of Well Cements at Downhole Conditions

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