Well Done!
Simplicity can sometimes break the shackles of complexity and open the door to lost potential.
At least that’s the case of the “wedge well,” Cenovus Energy’s solution to accessing stranded yet partially mobilized bitumen between its steam assisted gravity drainage (SAGD) well pairs.
Now considered commercial by the Calgary-based company at its Foster Creek project and on its way to the Christina Lake installation near Fort McMurray, wedge wells have people talking,
from researchers at TD Newcrest and the Canadian Energy Research Institute (CERI) to emerging producers including Southern Pacific Resource Corp.
“There is beauty in simplicity; if an area of heated, mobile, stranded bitumen exits between two existing SAGD well pairs, why not simply drill a horizontal well and pump it out?” asked TD Newcrest in a research document earlier this year, with the answer already in hand. “This is exactly what Cenovus wedge wells do.”
Cenovus Energy, which can boast the talk-first commercial application of SAGD at Foster Creek in 2001 and some of the highest performances of the technology in the business, describes its wedge wells this way:
“SAGD well pairs are drilled with about 100 metres between them. After about two years of production, the steam chambers between pairs begin to commingle and eventually overlap. This leaves a wedge of unproduced oil between the well pairs at the base of the reservoir.”
In 2004, Cenovus Energy initiated its wedge well pilot at Foster Creek.
“Wedge wells are single, horizontal wells drilled between two SAGD well pairs. They allow us to extract much of the bitumen that was previously unrecovered,” the company says. “Since wedge wells require minimal steam to extract the remaining bitumen, we have been able to increase our bitumen production by about 500 barrels per day per wedge well while at the same time reducing our per barrel operating costs, water use and environmental impact.”
To better understand this incremental technology advantage, Harbir Chhina, Cenovus Energy’s vice-president of upstream operations in its integrated oil division, explains that wedge wells have been “in the back of our minds” for close to a decade, but to fully appreciate them, one must get to know Foster Creek.
Before the project was even a pilot, which (once expansions are complete later this year) will become the largest capacity installation of its kind, the company drilled vertical wells without steam and was successful producing bitumen.
“Foster Creek is the only project I know of that can produce Athabasca McMurray oil without heat,” Chhina says. He adds, however, that that means producing sand as well.
“We don’t like producing sand. It’s a high maintenance thing. We knew we needed SAGD to get in there; we knew (the wedge wells) would be successful, we just didn’t want to do them right away.”
Last year there were 30 wedge wells operating at Foster Creek. Each one takes about $1.4 million to drill and complete. Another 13 are planned at Foster Creek this year.
However, Cenovus Energy is not expecting the technology to be as successful outside the leases of the first commercial SAGD project.
Chhina says the API gravity of Foster Creek oil is between 10 and 10.5, while at its newest new site at Christina Lake, it is about nine.
“That makes a huge difference.” At Christina Lake, he says steam circulation needs to reach about 90 degrees Celsius before viscosity starts to get lowered enough to produce. On the other hand, “at Foster Creek we are almost moving oil at reservoir pressure. 10-20 degrees at Foster Creek goes a long way in decreasing viscosity.”
But the success of wedge wells at Foster Creek practically begs attempting them in other places.
Chhina says the average wedge well production is about 700 barrels per day, compared to about 800-850 barrels per day from SAGD well pairs.
“It’s actually very comparative to SAGD well pairs, without much steam.”
He says the company will “play around with one well first” at Christina Lake. It will take drilling and operating three to four wells at the smaller project before Cenovus will decide to include the technology in commercial operations.
“It’s an economic question,” Chhina says.
The economics at Foster Creek have been encouraging so far, including the benchmark steam-to-oil ratio (SOR), which is already low at about 2.6 ( “That includes all the start-up steam,” Chhina says). He adds that the cumulative SOR of the wedge wells over the last three to four years is 0.08.
“We do put in some heat, but it’s not a whole lot. I think this changes a lot of metrics by about 10 to 15 per cent.”
Those metrics include dropping the SOR, as well as operating costs and capital investment. Chhina also cites the pressure to reclaim land as one of the benefits wedge wells provide.
“It helps me reuse the existing equipment on pads. Hopefully I can be in and out in 10 to 12 years rather than 30.”
When CERI lead researcher David McColl introduced the report Green Bitumen: The Role of Nuclear, Gasification and CCS in Alberta’s Oil Sands to attendees at the Calgary Petroleum Club last year, he mentioned wedge wells as one of the incremental technologies that could benefit the sector. These technologies were not included in the report because they are not considered commercial, which CERI defines as being deployed by two or more companies at two or more sites. Perhaps wedge wells will one day, even soon, fit into that category.
In its January research note, TD Newcrest reported that Suncor Energy had drilled its first wedge well at its Firebag SAGD project. Suncor denies that claim but emerging producers are talking about wedge wells.
In a recent interview with the Business News Network (BNN), Southern Pacific Resource Corp. president and chief executive officer Byron Lutes, spent time addressing the technology and its importance to SAGD.
Southern Pacific has plans for its own 12,000 barrel per day project in the Athabasca region.
“(SAGD) is still new technology in a sense because it has only been on-stream commercially for about seven years and so right now there’s a lot of perfections that are going on to enhance the efficiency of it and we hope to take advantage of some of those,” Lutes told BNN.
“(One) is a concept called wedge wells that has been proven by Cenovus Energy. A wedge well is essentially a single horizontal well that is put in between the two SAGD pairs to recover unswept oil that’s been heated by the steam in the first round of steaming. You can get up to 7 to 10 per cent incremental recovery by just putting a well in and no additional steam.”
Whether the wedge well will be successful outside the seemingly ideal reservoir of Foster Creek has yet to be seen. Cenovus Energy has a patent pending.
*This Report has written by Deborah Jaremko, Editor of Oilsands Review, a JuneWarren-
Nickel’s Publication and a sister magazine to Canadian Mining Journal.
Comments