Surface Casing Vent Flow: Canada’s Crutch

Tags: P&A | Orphan Wells | Canada

May 10, 2022

Canadian Concerns: Leaky Wells

Surface casing vent flow (SCVF), the uncontrolled migration of liquid and gas upward through leakage pathways in the annulus, has become a major issue in Canada. While operators are taking action to intervene and prevent the escape of greenhouse gases like methane, the cards are stacked against them.

Energy Legacy: Oil & Gas Abound

Oil and gas production in Canada dates to the mid-1800s, when the first well was dug by hand in Ontario to a depth of 4.62 m by James Miller Williams. Since then, tens of thousands of wells have been drilled across the country.

In the early days of production, permits for drilling and standards for well construction were non-existent. Old wells were often sealed with whatever was at hand – gravel, trees, or other local materials. Over time, the integrity of these wells has started to fail, resulting in thousands of legacy wells leaking methane into the atmosphere.

Fugitive Emissions: Spotlight on Methane

Methane is the primary gas emitted through leaks in oil and gas wells. It is an extremely potent greenhouse gas, trapping 80 times as much heat as carbon dioxide over a 20-year period and occasionally resulting in disaster (soil pollution, aquifer contamination, and even explosion).

When methane combines with oxygen, there is the potential for sudden explosion – as occurred in Wheatley. In August 2021, Wheatley, an Ontario town of 3,000, was devastated by a methane explosion from an abandoned, unmarked oil or gas well.

Government Action: Addressing Orphan Wells

The Canadian government has earmarked $1.7 billion to address a portion of these wells that no longer have an owner and are now the responsibility of the state (orphan wells). However, this issue is not limited to just orphan wells and addressing the problem of SCVF is expensive, as evidenced by the government’s assignment of $110,000 to plug each orphan well.

Maurice Dusseault, professor of engineering geology at the University of Waterloo, says addressing the province’s thousands of abandoned wells is a “wicked problem,” one with no easy solutions.

Sealing Leaks: An Expensive Fix

Costs to eliminate SCVF range from $30,000 to well over $100,000 depending on the specifics of the well and how many attempts it takes to fix the problem. Much of these expenses are due to costs associated with bringing rigs on-site to perform downhole intervention.

Currently, downhole intervention in the form of perforating casing to reach the leak and then squeezing in sealant is the most common way of dealing with this issue. This method often fails, as sealants like cement and resin are too viscous to flow into leakage pathways and eliminate the flow of gas.

A Cost-Effective Solution: BioSqueeze®

BioSqueeze® has proven to be a much more effective solution. Using the natural process of biomineralization, low-viscosity fluids are squeezed hundreds of feet into leakage pathways where they form limestone to eliminate leaks at their source. BioSqueeze® routinely seals leaks on the first attempt, limiting the release of fugitive emissions and cost of remediation with efficient operations.

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