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March 18, 2009

Underground Burning Variations for Oilsand Recovery and Gasifying Coal Underground

Alberta has several large scale pilot projects to perform many more oil refining and combustion steps underground and coal gasification underground. The advantages can be significantly lower costs and improved environmental effects.

This site has covered the work of Petrobank to develop the THAI (Toe-to-Heel Air Injection)and CAPRI processes for upgrading oilsand bitumen underground for increased recovery rates and lower costs. There are other projects to lower the cost and increase the recovery rate of the oilsands.

Combustion Overhead Gravity Drainage
Excelsior Energy Limited now plans to deploy a proprietary in situ combustion bitumen-recovery process called Combustion Overhead Gravity Drainage at its Hangingstone oilsands property.

Excelsior has developed the COGD process in cooperation with Hot-Tec Energy Inc., a private company affiliated with members of the In-situ Combustion Research Group from the Department of Chemical and Petroleum Engineering at the Schulich School of Engineering, University of Calgary.

COGD employs an array of vertical air injector ignition wells above a horizontal production well located at the base of the bitumen pay zone. A short initial period of steaming prepares the cold bitumen for ignition and develops enhanced bitumen mobility in the reservoir. Upon ignition a combustion chamber develops above and along the length of the horizontal well with combustion gases segregated in the upper part of the reservoir and hot bitumen flowing by gravity into the horizontal production well.

The COGD process is expected to bring a significant reduction in water usage for steam generation by up to 80% compared to a similar sized SAGD process. It is expected to yield a significant reduction in fuel gas consumption for steam generation by up to 80% compared to a similar sized SAGD process, as COGD uses the in situ energy of the bitumen which would otherwise be unrecoverable.

It also involves a reduction in diluent demand as a result of potential in situ bitumen upgrading and a reduced environmental impact through decreased water draw and water recycling, decreased fuel gas and diluent demand.

All of these should significantly improve project economics as COGD recoveries are estimated to be as much as 50% greater than SAGD recoveries, and capital and operating costs are estimated to be considerably lower than comparable SAGD projects.


Underground Coal Gasification

Underground coal gasification has been used commercially outside of North America for close to 40 years with minimal surface impact when compared to traditional coal mining and production.

The syngas produced by underground coal gasification is amenable to efficient pre-combustion carbon dioxide (CO2) capture, producing a high-purity CO2 byproduct. It may also be feasible to sequester captured CO2 in coal seams depleted by underground coal gasification.





The project with Swan Hills Synfuels LP is the first of its kind in North America to demonstrate coal gasification at depths greater than 1,000 meters below the surface.

Underground coal gasification does not use fresh water in its operation and is significantly different than other in situ processes, such as those used in oil sands development. Underground coal gasification is used at depths where conventional coal mining is not economic or currently possible.



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