|Chevron will use SAGD to produce the bitumen. Click to enlarge. (Explanation below.)|
Chevron Corporation has acquired five oil sands leases in the Athabasca region of northern Alberta, spanning more than 180,000 acres and possessing an estimated 7.5 billion barrels of oil in place. The company hopes to be producing 100,000 barrels of oil a day within 10 years from the project.
Chevron already is active in the Canadian oil sands. The company is a 20% joint venture participant in the Athabasca Oil Sands Project (AOSP), which includes the Muskeg River Mine and the Scotford Upgrader. AOSP produces approximately 155,000 barrels per day.
The new leases are approximately 76 miles west of Fort Mackay in northern Alberta, and 24 miles south west of AOSP.
Chevron will use Steam Assisted Gravity Drainage (SAGD), an in-situ technology that uses steam and horizontal drilling to extract the bitumen. Shell Canada and Western Oil Sands will each have the right to elect to acquire a 20% working interest in these leases.
The SAGD process involves drilling pairs of horizontal wells in the oil sands reservoir. Steam is injected through an upper well—about 3 to 10 meters above the lower—and contacts the bitumen. The heated bitumen becomes mobile and flows with condensed water from the steam chamber to the lower well through gravity drainage. Thence it is lifted to the surface for upgrading.
Each well pair is typically 2,500 to 3,000 feet in length, and optimally produces 1,000 to 1,500 barrels per day. Well pairs are drilled parallel to one another, and spaced 300 to 650 feet apart.
The main operating cost for SAGD projects is the natural gas to fuel the steam generators. The Steam to Oil Ratio (SOR), which measures the volume of steam required to extract the bitumen, is the key measure of a thermal project’s efficiency. The lower the SOR, the better. Industry SOR rates for SAGD range from 2 to 4.
Cyclic Steam Stimulation (CSS), an older thermal processing technique that uses a single vertical steam injection that lets the steam “soak” the target zone for several weeks before recovering the liquid, is less efficient, with SORs ranging from 3.0 to 8.0.
CHOPS: Cold Heavy Oil Production with Sand in the Canadian Heavy Oil Industry; Dr. Maurice Dusseault, March 2002
Nexen Long Lake Project