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COMPENDIUM 3.0: Part 3 - Engineering

This content is derived from the Physicians For Social Responsibility Compendium 3.0

Studies consistently show that oil and gas wells routinely leak, allowing for the migration of natural gas and potentially other substances into groundwater and/or the atmosphere. Recent research suggests that the act of fracking itself may induce pathways for leaks. Leakage from faulty wells is an issue that the industry has identified and for which it has no solution. According to Schlumberger, one of the world’s largest companies specializing in fracking, about five percent of wells leak immediately, 50 percent leak after 15 years, and 60 percent leak after 30 years. Data from Pennsylvania’s Department of Environmental Protection (DEP) for 2000-2012 show over nine percent of shale gas wells drilled in the state’s northeastern counties leaking within the first five years. Leaks pose serious risks including potential loss of life or property from explosions and the migration of gas or other chemicals into drinking water supplies.

Leaks also allow methane to escape into the atmosphere, where it acts as a more powerful greenhouse gas than carbon dioxide. Indeed, over a 20-year time frame, methane is 86 times more potent a heat accumulator than carbon dioxide. There is no evidence to suggest that the problem of cement and well casing impairment is abating. Indeed, a 2014 analysis of more than 75,000 compliance reports for more than 41,000 wells in Pennsylvania found that newer wells have higher leakage rates and that unconventional shale gas wells leak more than conventional wells drilled within the same time period. Industry has no solution for rectifying the chronic problem of well casing/cement leakage.

It's been found that well failures have been triggered by underground movements that cause well casings to shear. Sheared well casings can allow gas and fluids from the fracking zone to migrate to overlying aquifers. Prolonged drought can also damage the integrity of well casings: as groundwater levels fall, landforms can sink and contribute to casing shear. California is particularly suceptible to both conditions of drought and unstable ground. Other findings show there is a risk that well integrity can fail, especially over time, and questions have arisen about whether high-volume hydraulic fracturing can cause seismic changes which could potentially result in fracturing fluid migration through abandoned wells or existing fissures and faults. Fracking older wells poses additional risks because of well casing degradation and corrosion from chemicals used in drilling operations.

Besides water contaminiation, natural gas can also escape around well casings or through cracks that allow combustible gas to leak into the atmosphere. It is projected that 40 percent of shale gas wells in Northeastern Pennsylvania will leak methane into groundwater or the atmosphere over time. The state currently has 41,000 gas wells since 2000. A comparative analysis showed that newer, unconventional (horizontally fracked) shale gas wells were leaking at six times the rate of conventional (vertical) wells drilled over the same time period.

A panel from the Council of Canadian Academies identified inherent problems with well integrity as one of it's top concerns. They wrote:

"Two issues of particular concern to panel members are water resources, especially groundwater, and greenhouse gas, GHG, emissions. Both related to well integrity…. Natural gas leakage from improperly formed, damaged, or deteriorated cement seals is a long-recognized yet unresolved problem …. Leaky wells due to improperly placed cement seals, damage from repeated fracturing treatments, or cement deterioration over time, have the potential to create pathways for contamination of groundwater resources and to increase GHG emissions."

University of Waterloo in Ontario, and the Society of Petroleum Engineers, reported that oil and natural gas wells routinely leak gas through cracks in their cement casings, likely caused by cement shrinkage over time and exacerbated by upward pressure from natural gas. According to their paper, in Alberta, it is common for wells to leak natural gas into aquifers. “Because of the nature of the mechanism, the problem is unlikely to attenuate,” they wrote, “and the concentration of the gases in the shallow aquifers will increase with time.

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