Fewer surface facilities are required than for SAGD–mainly comprising an electric powered air compressor for injection and separators and tanks for the production well. Greaves predicts that overall, THAI will prove to be very competitive against SAGD, requiring about half of the comparable capital expenditure and operating costs.

The THAI process begins similarly to SAGD, with both well bores preheated using steam to initiate oil mobility and clear pore space between the injector and the toe of the producing well. Athabasca oil, heated to about 125 degC, auto-ignites when air is injected. The energy to sustain in situ combustion comes from the burning of the coke that is continuously laid down within the reservoir. THAI is therefore more thermally efficient than SAGD, and this aspect has always been recognized as one of the winning attributes of the ISC process. Sulfur is reduced by about 20-30% and heavy metals are reduced by around 90%, being left as an inert residue on the reservoir sand. No water or gas fuel is required during production and, according to Greaves, the produced water can be easily treated to a reusable industrial quality.

A further benefit of THAI is that it performs in situ upgrading through thermal cracking of the heavy oil. Laboratory tests achieved upgrading by up to 10 API. 8 API oil was upgraded to 16–18 API and Wolf Lake 10.9 API samples were upgraded to nearly 20 API. This is a very valuable feature of the process, considering that each API point is presently worth about one dollar per barrel. Upgrading seen in the pilot tests has been variable, but the best field results to date have seen 7.6 API Athabasca bitumen upgraded to as high as 16 API and viscosity reduced to less than 100 cp. As soon as the process is fully stabilized (i.e., when lateral expansion of the combustion front is complete and it then advances in pure line drive), it is expected that the upgrading quality of the produced oil will become more constant.

 
THAI field pilot tests
The first THAI field pilot was started in July 2006 by PetroBank in Canada. This is the WHITESANDS project, near Christina Lake, northeast Alberta. Three separate dual-well sections have been drilled, spaced 100 m apart. Each well pair is capable of producing up to 2,000 bbl/d with a 50–60% bitumen cut (1,000 bbl/d). Sand production, although less than 0.5%, has required production to be temporarily choked-back because the surface facilities were undersized. However, when new, larger separators are installed, bitumen production is expected to rise to about 1,500-2,000 bbl/d per well.

Greaves sees building industry confidence in THAI to be essential for its commercial success. He observes that the ongoing Petrobank pilot project is confounding the skeptics and adding value to the company. Start-up of the first pilot was completed in less than 12 months from the end of design to construction–about half the time it typically takes to startup a SAGD project. A second pilot, also comprising three pairs of wells, is scheduled to start production mid-2008 and this will also incorporate the first trial of the CAPRI process.  CAPRI involves ‘gravel packing’ of a layer of refinery-type catalyst along the outside of the horizontal producer well.  The CAPRI process was developed at Bath University with generous support from EPSRC. Drs. Ayasse and Turta also collaborated on this work. Dr. Ayasse is a co-patentee of CAPRI, along with Petrobank.

The Petrobank Web site provides more information about THAI and CAPRI technology, pilot tests and frequently asked questions (FAQs).

THAI and CAPRI are trademarks of Petrobank Energy and Resources Ltd.

Applications of THAI