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Ensuring safety of gas storage facilities Joint task force report makes recommendations from lessons learned from massive leakage from California storage site in late 2015 ALAN BAILEY Petroleum News
In the wake of a massive leak of natural gas from the Aliso Canyon gas storage facility in California between October 2015 and February 2016, a joint task force headed by the U.S. Department of Energy and the U.S. Department of Transportation has published a report with recommendations for the future safety of gas storage facilities in the United States.
The Aliso Canyon leak, the largest in U.S. history from a storage facility, released 90,000 metric tons of methane, caused health issues for local people and deposited an oily residue on many residences. Thousands of households were displaced, and the governor of California declared a state of emergency for the impacted area, the task force report says.
After the failure of multiple attempts to stop the gas leak by pumping heavy “kill fluids” into the well, the well was eventually plugged by the drilling of a relief well that intercepted the renegade well bore.
Warehousing gas Gas storage facilities, typically using underground rock reservoirs, warehouse excess natural gas during periods of low gas demand, so that the stored gas can be used to bolster gas supplies when gas demand rises. In Southcentral Alaska, the tightening of gas supplies from the Cook Inlet basin has caused gas storage facilities in the region to become critical in ensuring the availability of adequate amounts of gas for power generation and for the heating of buildings during cold winter weather.
The task force report says that a detailed root cause analysis of the Aliso Canyon leak is still underway. However, it appears that gas was leaking through the casing of the problem well and that, because gas flowed up the well through both the casing and the internal well production tubing, there was only a single barrier between the gas and the outside of the well. Complex subsurface flow paths for the leaking gas may have impeded the ability of the kill fluids to suppress the gas flow, the report says.
In fact, rather than fixing the problem, the use of the kill fluids made the situation worse by eroding a large vent around the wellhead, the report says.
Apparently - as with other wells in the storage facility - the problem well had been monitored for leaks annually, although well logs that could have been used to assess the risk to the well could not be located. The well had been completed in 1954.
Recommendations In the light of what it already known about the Aliso Canyon accident, the task force has made a number of recommendations.
New storage facility wells should be designed in a manner that ensures that a single point of failure cannot lead to gas leakage and an uncontrolled gas flow. And, except under limited circumstances, the operators of storage facilities should phase out the use of wells that have single points of failure, the report says.
Risk management plans for storage facilities should include a rigorous monitoring program, well integrity evaluations, leakage surveys, mechanical integrity tests and conservative assessment intervals.
Also, the Department of Energy and the Department of the Environment should conduct “a specific and thorough joint study” of subsurface safety valves, the report says. Apparently the problem well did not have a subsurface safety valve that might have cut off the flow of leaking gas.
Health and the environment From the perspective of health and the environment, the report recommends the prompt formation of a unified command in the event of a gas leak large enough to impact multiple jurisdictions. A unified command is a protocol commonly used to coordinate government agencies and other stakeholders in a response to an emergency situation. A unified command could coordinate communications about a gas leak and facilitate an understanding of any potential public health impacts, the report says.
States and local agencies should consider establishing an air monitoring plan that can be deployed in the event of a gas leak. And states should review their authority to require greenhouse gas mitigation plans in the event of a leak, the report says.
One concern about the possibility of a leak from a gas storage facility is the potential impact on gas supplies and energy reliability in the region that the facility serves. Industry and government agencies should strengthen their planning for mitigation of the impacts of disruption to the natural gas infrastructure - consideration is needed for backup strategies to reduce the energy reliability risks associated with the abrupt loss of natural gas supplies, the report says.
CINGSA In Southcentral Alaska Cook Inlet Natural Gas Storage Alaska Inc., or CINGSA, operates a gas storage facility on the Kenai Peninsula, south of the city of Kenai. The facility primarily supports Southcentral gas and electricity utilities, enabling the utilities to warehouse gas for winter use. The CINGSA facility was completed in 2012, using a depleted gas reservoir in the Cannery Loop gas field and involving the drilling of all new wells for the injection and withdrawal of gas.
CINGSA has told Petroleum News that its storage facility complies with Alaska Oil and Gas Conservation Commission regulations, which constitute some of the most stringent safety regulations in the United States.
“CINGSA was designed in 2012 to the highest standards for underground natural gas storage operation and safety,” wrote Lindsay Hobson, CINGSA communications manager, in an Oct. 19 email. “As such, the CINGSA storage facility, along with its established monitoring and maintenance procedures, meets or exceeds the applicable recommendations from the Department of Energy report.”
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