Science-based model applied in Canadian Rockies

Permeability Trumps Storage in Shale Play

Shale formations can confound even the savviest geoscientist when it comes to determining the inner workings of the rock.

After expert evaluation, even the most attractive prospecting deal can be a tough sell owing to the fact that there are seldom any two zones that are laydowns. And there’s almost always a new piece to each of these puzzles that requires some sophisticated high-tech explaining.

The geologists and geoscientists at Shale Petroleum Ltd. in Calgary, Canada, are all too familiar with this scenario.

And they have their own way of dealing with the challenges.

“We’re geeks,” said company president and CEO Paul MacKay. “We do the science and then go after the land position. That’s our business strategy – and we then choose a U.S. partner or drill ourselves.”

MacKay, an AAPG member, noted that they buy land where the rocks are highly permeable, allowing fluid to migrate through them with relative ease. He sides with the geoscientists who favor permeability over storage as key to defining unconventional reservoirs.

The company’s landholdings in southern Alberta, largely within view of the Rocky Mountains, underscore his science-based opinion.

He noted that as the Rockies formed, the accompanying pressure on organic material converted it into oil and thrust it outward into the surrounding region.

“There is relic overpressure the closer we stay to the mountains, and we concentrate on defining the pressure window,” said MacKay, who is often dubbed a rock fracture specialist by his peers.

He likened the mountain range to a pump, with the surrounding prairies serving as a sponge of sorts. He and his team are focused on buying parts of the “sponge” that are still being subjected to pressure and are permeable and fractured.

Fractures Trump the Matrix

Canadian shale plays of Devonian age, such as the Horn River, Duvernay and Canol, are some of the more high profile names during this industry time of “shale rules.”

The Jurassic Nordegg play is attracting attention along with the now-familiar Triassic Montney shale.

The Cretaceous-age Colorado Group (Alberta Group) is in Shale Petroleum’s crosshairs, with the focus on the Second White Specks formation, which is a fractured marine, inter-bedded shale, siltstone and fine-grained sandstone.

The name comes from actual white specks observed by the drillers, which were identified as cocoliths.

This naturally fractured reservoir has provided many hydrocarbon shows, but not the repeatable success that would establish a resource play.

Despite the dearth of repeatability, there have been a few vertical wells of significance drilled in the Second White Specks over about a 300-mile area, according to MacKay. Four of these have produced over one million barrels each, and three of them are still producing after 20 years.

Production depths range between 4,000 and 8,000 feet.

There is no apparent reservoir, indicating they are not your father’s vertical well.

“In these cases, the well appears to have intersected a regional natural fracture system that has delivered significant volumes of hydrocarbons,” MacKay said.

“In resource plays, there is an ongoing debate over the merits of matrix permeability versus the permeability of the natural fracture system,” he noted. “In the case of the Second White Specks formation, the natural fracture system dominates the permeability system.

“Success in the Colorado Group is dependent on not only finding successful permeability pathways but also locating over-pressured areas that will provide the driving force for fluid flow,” he emphasized.

Team-Led Innovation

So, you ask, when will the drill bits start turning on the company’s lease holdings?

“We’re getting ready to drill two science wells, which will be vertical,” MacKay said. “We’re always looking for the right combination of pressure and fractures near mountain thrust belts, and it takes time to find that exact fit.

“We must understand the rocks because we’re a technology-driven company instead of one that’s opportunity driven.

“The key to unlocking the petroleum potential of the Colorado Group, particularly the Second White Specks, is to exploit the natural flow paths within the rock volume by means of an integrated approach of geology, rock mechanics and reservoir engineering,” MacKay emphasized.

“Innovation will come, not through one single discipline but through a team effort and a cross-discipline approach.

“As we work on fractured rocks, we must be communicating with reservoir engineers, or else the proposed prospect will never be drilled,” he noted. “Advancing the integrated side in science is a test of teamwork versus any individual, no matter how knowledgeable.

“That,” he added, “is really the challenge.”

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