The Grosmont Carbonate Trend

The Grosmont Formation is a stratigraphic unit of Upper Devonian (Frasnian) age. It is present in the sub-surface of north-eastern Alberta,1 south-west of the Sub-Cretaceous erosional edge and north-east of the Ireton Shale facies of central Alberta.

The ERCB estimates more than 400 billion barrels (65 billion m3) bitumen in place are trapped in the heavily karsted Grosmont Carbonate Trend.2 These reserves elevate the Grosmont to the likes of the Ghawar oilfield in Saudi Arabia (90 billion recoverable barrels) and Kirkuk carbonate oil filed in Iraq (15 billion recoverable barrels).

Grosmont Carbonate – bituminous lamination

The hydrocarbons contained in the Grosmont (and overlying Nisku Formation) have viscosities of 5 to 9 API, with specific gravity in excess of 1000 kg/m3, classified as extra heavy oil, commonly referred to as bitumen.

Experimenting with hydrocarbon extraction from the Grosmont dates back to the 1970s, when the Alberta Oil Sands Technology and Research Authority crown corporation, along with industry partners Union Oil Canada and Chevron Resources Canada encountered little success. Extraction pilot programs are currently conducted by Shell, Laricina Energy, Athabasca Oil Corporation, OSUM Oilsands Corp, Husky Energy and Sunshine Oilsands.

Investors in the emerging play include Canada Pension Plan Investment Board (backing Laricina), Korea Investment Corporation (OSUM and Laricina), China Investment Corp (large shareholder in Sunshine Oilsands), Blackstone Capital Partners, Goldman Sachs and many others.

Laricina experimented with cold solvent injection/production cycles staring in 2007 at Saleski (85-19W4). Recovery enhancing technologies currently being tested include SAGD, SC-SAGD and TAGD. These extraction techniques complement proven drilling methods (horizontal drilling) and high resolution seismic mapping. Shell operates a In situ Upgrading Process (IUP) since 2009 south of Chipewyan Lake (91-23W4), a process also known as TAGD (Thermal Assisted Gravity Drainage). Laricina and OSUM conduct a horizontal Solvent-Cyclic Steam-Assisted Gravity Drainage (SC-SAGD) pilot project in Saleski. Other technologies considered for the extraction of bitumen from the Grosmont include Electro-Thermal Dynamic Stripping Process (ET-DSP), In Situ Combustion (ISC), Cyclic Steam Stimulation (CSS), other variants of Vapour Extraction (VAPEX), and Steam Flooding.

Oil soaked Grosmont core

Technical challenges are not limited to hydrocarbon extraction. The low pressure, intensely karsted, vug ridden carbonate poses difficulty in drilling and appraisal. Lost circulation is a common occurrence (with the associated risk of stuck pipe), while low core recoveries due to the brittle nature of the rock can paint an incomplete picture of the reservoir. Bitumen filled vugs range in size from millimetres to tens of meters in diameter, creating difficult drilling conditions, especially in horizontal holes. The so called “dolo-fudge” (dolomite grains floating in bitumen matrix) is even less consolidated. Recent advances in coring techniques and horizontal drilling procedures overcame most of the drilling challenges and open the road towards commercial development.

If the commercial viability of heavy oil extraction from the Grosmont can be proved, it will be a game changer, not only for Alberta’s reserves, but for the entire global oil and gas landscape.

Chinook Consulting assists heavy oil operators with field and office geological supervision for delineation, production pilots and development projects targeting the Grosmont Carbonate. Several of our wellsite geologists have substantial exposure to this particular formation.

Calin Dragoie

Posted On:
June 8, 2012

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