AER says Primrose bitumen leaks preventable, But regulator leaves limits in place on Canadian Natural Resources by Dan Healing, July 22, 2014, Calgary Herald
Bitumen emulsion leaks to surface from the Primrose oilsands play near Cold Lake are preventable, says the Alberta Energy Regulator, but it won’t immediately lift limits placed on the producer. In a news release Tuesday, the AER said it accepts a report submitted last month by operator Canadian Natural Resources Ltd. of Calgary explaining how four releases to surface occurred in spring of 2013. The leaks affected 20.7 hectares and an ongoing cleanup effort has so far recovered about 7,400 barrels (1.2 million litres) of bitumen emulsion. “Our assessment of the reports leads us to believe that these flow-to-surface events can be prevented if proper mitigation measures are put in place,” said AER president and CEO Jim Ellis in the release.
“That said, the AER is not prepared to approve a return to full operations at these sites until all potential risks are addressed and proper requirements are in place to avoid a similar incident. This will require a gradual, step-by-step approach that allows us to manage those risks.”
The AER imposed restrictions on steaming activity at Primrose East and within one kilometre of Primrose South in June 2013.
Canadian Natural submitted its causation report to the AER last month and the regulator then had an independent technical review of the report into incidents at the east and south sections of the company’s Primrose project.
It said the technical review determined that the “enabling factors” were the steaming strategy used by Canadian Natural — to inject large volumes of steam at fracture pressure in closely spaced wells — and wellbore issues.
The Primrose field is produced using cyclic steam stimulation, where wells are steamed for a period of some months to mobilize the heavy oil, then the steam is halted while the oil is pumped to surface.
Canadian Natural has maintained that faulty well bores are the cause of the leaking, not cracks in the caprock overlying the oilsands formation, but a spokeswoman agreed after its report was released that large injected steam volumes can cause a fracture to work its way to the surface.
Chris Severson-Baker of the environmental Pembina Institute said earlier the Canadian Natural report “calls into question” the use of high pressure steam. “I think we need a broader review of this technique — how long should it be used in one formation? Is it appropriate, given the geology of the area, or is it too risky?” Severson-Baker also questioned the regulator’s approval of a project without knowing if the caprock is susceptible to cracking. [Emphasis added]
Athabasca Chipewyan Knew that Cracked Caprock Could Cause Bitumen Leaks in Cold Lake – Company Finally Agrees by Meagan Wholberg, July 11, 2014, One River News
After years of denying that a break in the caprock could be responsible for the series of blowouts at its oilsands operations near Cold Lake, Canadian Natural Resources Ltd. (CNRL) acknowledged for the first time this month that the factors contributing to ongoing bitumen seepage on its Primrose lease could be more than simply failed wellbores.
Though maintaining that the leaks are still “most likely” the results of wellbore failure, the report admitted that high pressurized steaming of bitumen below the protective caprock has the potential to “stress” the capping shale. …
The report marks the first time the company has indicated anything other than its stance that the leaks were caused by wellbore failures. For scientists, First Nations and environmental groups who have been pointing to the issue of caprock integrity as the problem behind CNRL’s leaks, the company’s acknowledgement offers some vindication.
The Athabasca Chipewyan First Nation in northeastern Alberta was among the first to challenge CNRL’s messaging that the leaks were due to a failed or partially failed wellbore, instead asserting that the formation was over-pressurized by high powered steam injection used to melt down and extract the bitumen.
“They’ve been super-heating and pressurizing the ground for the last decade now in that region and lo and behold, something has happened and they have no idea how to control it,” Eriel Deranger, communications coordinator for ACFN, told Northern Journal back in July 2013. “They don’t know the long-term impacts of these projects and this is a prime example that government and industry don’t have the foresight or the technology to back up their assumptions of what these projects will really do to the land, environment and ultimately the people.”
A report released in February of this year by independent scientists Kevin Timoney and Peter Lee backed those assertions.
Timoney and Lee argued that it was unlikely to have four wellbores located 6 km apart fail at the same time. Rather, they said, the leaks were likely the product of a fracture in the caprock overlaying the bitumen formation.
“Simultaneous multiple wellbore failure is unlikely to explain the incidents. A more likely explanation might be stress-induced fracture of a single geologic structure, the shale cap rock,” they wrote.
“Given the fractured nature of the bedrock in the region, it is possible that a single wellbore failure resulted in the conduction of emulsion through the cap rock containment, after which the bitumen emulsion was free to migrate along the three-dimensional network of bedrock fissures to later surface at four locations.”
Those at the Pembina Institute say CNRL’s report is unlikely to come as a surprise to the AER, whose investigation (then done as the Energy Resources Conservation Board) of the company’s 2009 blowout on the same lease concluded the leaked bitumen was the result of high steam pressure and weakness in the caprock.
The AER has yet to announce the results of its investigation into the more recent leaks, though CNRL has been permitted restricted steaming operations at the site. [Emphasis added]
Cracks in rock could be connected to Cold Lake bitumen leaks, CNRL acknowledges by Sheila Pratt, July 8, 2014, Edmonton Journal
A new report by oil giant Canadian Natural Resources Ltd. acknowledges cracks in rock layers could be part of the reason bitumen is leaking at four sites on its Cold Lake high pressure steam operation.
An environmental group says the company’s report, released Monday, should prompt the Alberta Energy Regulator to review whether CNRL’s unique high-pressure steaming process is too risky in the area.
At the four leak sites, discovered in spring 2013, about 12,000 barrels of bitumen have come to the surface. A regulator’s report on a similar 2009 leak in the area pointed to possible geological weakness in layers of rock in the area.
But CNRL has adamantly disagreed, saying the hard caprock (the layer on top of the bitumen deposit) does not crack. The bitumen flows to the surface through old, faulty well bores, CNRL says. In November, company president Steve Laut told investors: “We have not see any evidence that would indicate any other possible route to the surface” than through an old well bore.
But the new report takes a different view, citing natural cracks or cracks caused by steaming that could allow the bitumen to leak.
The report lays out four conditions that could cause the leaking, including “vertical hydraulic induced fractures” — cracks in the deeper rock layers or in the top layers of shale caused by steam pressure.
CNRL spokeswoman Zoe Addington said the company has not changed its position. Faulty well bores are still the cause of the leaking, but CNRL is “committed to reviewing all options.”
“We have learned in the presence of large injected steam volumes … the fracture can work its way to the surface,” Addington said in an email.
The report says the company could “make changes to steaming strategy” to prevent leaking from deep underground in the future.
Chris Severson Baker of the Pembina Institute says the report “calls into question” CNRL’s technique of sending high pressure steam into the ground for weeks, letting the pressure build up, then forcing the bitumen up the wells.
”I think we need a broader review of this technique — how long should it be used in one formation? Is it appropriate, given the geology of the area, or is it too risky?”
Severson-Baker also questioned the regulator’s approval of a project without knowing if the caprock is susceptible to cracking.
Federal scientists used satellite photographs to record how the landscape heaved up and was deformed by the underground pressure around the leaking sites.
As conventional oil dries up, oil companies “push the limit” using steam and pressure to extract more bitumen from in situ sites, said Severson-Baker.
“So that puts the onus on the (regulator) to act as a check on these methods as industry expands into harder-to-get reserves,” he said.
The Pembina Institute describes the leaks at CNRL’s Primrose sites as an “uncontrolled blowout in an oil reservoir deep underground.” [Emphasis added]
PRIMROSE FLOW TO SURFACE CAUSATION REPORT by Canadian Natural Resources Ltd., June 27, 2014
5. HYDROGEOLOGY OVERVIEW
Groundwater monitoring wells were installed at the four FTS sites discovered in 2013. The wells are completed in non-saline Quaternary aquifers identified during drilling. Wells drilled at these sites has shown bitumen emulsion passed through the aquifers and on to the surface through vertical hydraulically induced fractures.
Bitumen emulsion flow mechanisms through the Colorado Group were evaluated and the integration of historical data with the causation review has resulted in the following findings:
1 Existing wellbores with poor hydraulic isolation due to cement placement are low resistance flow paths for vertical movement.
4 Significant vertical flow occurs within natural fractures and faults only under unusual conditions:
a) A pressure equal to or greater than the normal stress acting upon a natural fracture, fault, or bedding plane
b) Sufficient vertical connectivity of the natural fractures or faults
c) The existence of more isotropic stress conditions that may be promoted by overburden uplift
5 Tensile parting (i.e. opening of natural fractures, faults and bedding planes) can only occur at high pressures at or above the minimum principal in-situ stress. This means that the stress state heavily influences the orientation of bitumen emulsion hydraulically induced fractures.
6 With CSS operations, one mechanism to modify in-situ stresses is uplift induced stress change. The greater the amount of uplift, the greater the change of in-situ stresses.
7 The uplift induced stress changes increase the vertical stress above the area of CSS injection and this results in:
A reduced stress contrast between the vertical principal stress and the minimum horizontal principal stress within the Joli Fou Formation and higher
An increased hydraulic fracture pressure within the Joli Fou Formation
An increased minimum principal stress contrast between the Grand Rapids and Joli Fou formations
Under conditions of significant uplift induced stress changes the permeability of natural fractures, faults, and bedding planes increases sufficiently to accommodate FTS bitumen emulsion flow rates, in the presence of hydraulic fracture pressure
8.1 Excessive Release of Bitumen Emulsion from the Clearwater Reservoir
into the Next Overlying Permeable Formation, the Grand Rapids
Fluid leaving the Clearwater reservoir initiates FTS events. Geochemical analysis has shown a relationship between the fluid recovered at surface and the fluid in the Clearwater reservoir. … Intermittent releases from the Clearwater reservoir to the Grand Rapids Formation can occur with or without wellbores. It is believed that the releases are related to dilation of the Clearwater reservoir. The intermittent releases have occurred during uplift of the Clearwater Capping Shale, and the releases are due to a wellbore, injectite, shear movement of natural fractures or faults, hydraulically induced fracturing, or a combination thereof.
8.2 Vertical Hydraulically Induced Fracture that Propagates up to the top of
the Grand Rapids Formation
Intermittent fluid releases into the lower Grand Rapids Formation will initially be characterized by porous media diffusion into the Grand Rapids B12 water saturated sand. With sufficient flow rate, duration, and potential decreases in water permeability due to bitumen emulsion saturation increases, the pressure within the Grand Rapids B12 will increase to a point where a hydraulically induced fracture will initiate. Fracture growth is expected when the injection flow rate exceeds leak off. Excessive release volumes into the Grand Rapids Formation result in vertical hydraulically induced fractures propagating up to the top of the Grand Rapids Formation. [Emphasis added]
[Refer also to:
March 10, 2014: AER denies one of two CNRL applications to resume high-pressure steam injection near Cold Lake; AER keeps approving Encana’s high pressure frac fluid injection around dangerously contaminated water wells and Rosebud municipal drinking water supply
February 3, 2014: Satellite data sound alarm on safety of high pressure injection; data shows significant ground deformation (subsidence and uplift) in area of CNRL leak, 10 times faster than lower-pressure injection
“We should probably stop fracking there right now”