Corrosion causes half of oil, gas flowline spills
That means that as much as a quarter of all spills in the state reported to the Colorado Oil and Gas Conservation Commission relate to flowline corrosion. Mark Schlagenhauf, engineering integrity supervisor for the commission, said flowlines account for 40 to 50 percent of all spills that energy companies report to the agency.
Flowlines are pipelines running directly from wells, typically to the point of gas metering or where tanks collect produced oil. Flowlines also may carry water associated with oil and gas development. The commission doesn’t regulate other pipelines, such as gas gathering and transportation lines moving gas farther downstream.
The commission’s newly formed Engineering Integrity Group has undertaken a flowline audit program, and since the start of 2016 it has conducted 30 audits, mostly focused on larger companies operating in the Denver Julesburg Basin, North Park, and in western Colorado’s Piceance Basin.
The audit has its roots in direction the commission received several years ago from the Legislature to develop and implement a risk-based strategy for inspections in the state. An ensuing consultant’s evaluation of 1,638 spills reported from January 2010 to August 2013 found that 78 percent occurred during production.
The Legislature then appropriated funding for the Engineering Integrity Group, which includes a supervisor, engineer and field inspector. The group has turned its initial attention to flowlines, the source of the majority of production-related spills.
The audit’s review of causes reported from September of last year through February of this year showed that 48 percent of the spills resulted from corrosion, Schlagenhauf said. He said that number is consistent with other time periods evaluated since his group’s formation in late 2015.
“There’s a lot of old metal pipe out there,” he said.
The review found that natural events like freezing accounted for about 20 percent of the other flowline spills, with the remainder resulting from excavation damage, operator error, equipment failure, and weld or joint failures.
Identifying causes can help zero in on preventative measures such as more frequent adding of corrosion inhibitors to pipes, replacing older pipes and burying lines below the freeze line underground.
The commission requires flowlines to be pressure tested before being put in service, and then annually. The auditors have reviewed more than 3,800 pressure tests, audited more than 2,800 wells and done more than 400 flowline-related inspections.
Schlagenhauf said while the audit has resulted in some notices of alleged violations, typically in response to a spill, its focus has been on helping companies improve prevention efforts.
Preventing spills, or keeping them small, can spare companies the cost of a major cleanup, he said.
As an example, Schlagenhauf said one company has seen its spill numbers drop from 20 in 2015 to about six last year and one so far this year.
Oil and gas spills dropped from more than 700 in 2014 to 509 last year, a drop that may partly be because of reduced oil and gas development levels, but the commission also thinks may be because of its audit program.