Back in July, 1985, the Alberta Oil Sands Technology Research Authority (aostra) invited tenders to design and manufacture an underground drill rig to test a proposed method of recovering bitumen from the Alberta oil sands deposits. The drill rig is now undergoing surface tests at the Steel Bros. cement plant near Exchaw, Alta., and should be going underground on the aostra project sometime early this year.
The bitumen recovery method involves drilling a series of wells up into the oil-bearing sands from an underground mine and using a thermal method to get the bitumen to flow. Aostra specifications for the required drill rig include:
* Capability to drill 222-mm holes to 600 m.
* Capability to drill inclined holes within an area extending from the horizontal to the vertical.
* Minimum thrust of 200,000 lb.
* Minimum pulldown of 200,000 lb.
* Minimum torque of 10,000 ft-lb.
* Rotation speed of 1-200 rpm.
* A fluid circulating system capable of handling 1,500 L per min at 14,000 KPa.
* A pipe-handling system.
* Drill to be self-propelled and crawler-mounted.
* Powered by 1,100/550-volt prime movers.
In addition the drill rig would have to operate in mine tunnels four m high and five m wide. Finally, the equipment design would require components with dimensions less than 4.5 m high by 1.8 m wide in order to be lowered into the mine.
In October, 1985, the contract to design, construct and test the drill rig was awarded to Drill Systems International of Calgary. All concepts and designs were completed under the direction of aostra’s project manager Jack Haston, drill systems vice- president of research and development Floyd Becker and Cal Bohme, P.Eng., project manager for Norwest Engineering.
Norwest had previously been awarded the contract to act as drilling consultants for the entire project. This included all underground drilling operations by Sedco Drilling of Calgary.
All design and drafting functions were completed over a 10-month period. Final design specifications were remarkably close to the original aostra requirements but also incorporated a number of features which provided greater drilling efficiencies and broadened the capability of the drill rig. These features include:
* A dual electrical and hydraulic power drive. The unit will operate at half power should a single electrical motor or hydraulic pump fail.
* A Hiab type of crane to handle heavy components, such as blowout preventors, and to lift the portable console onto the bottom of the derrick for the travel mode.
* A remote operator’s console capable of handling the drilling function from a distance of six m from the drill rig. In addition the controls for the pipe-handler and the crane can be separated from the main console and operated by a helper. . Hydraulic rams to anchor the derrick to the mine walls. All drilling forces are transmitted through the derrick.
* A sliding mast to facilitate positioning of the drill rig.
* The rotary top drive has a 254- mm, inside-diameter, hollow spindle and is capable of drilling down, as well as up, at full torque and pull-up- pull-down ratings.
* A pipe and casing breakout system provides 25,000 ft-lb of force to break connections.
* The pipe-handling system is capable of lifting drill pipe and casing from pipe racks to a position directly under the rotary drive and directly in line with the drill hole. Drilling continues without physical handling of drill pipe or casing.
* A front operator’s console for the travel mode.
* A 52 degrees C cooling system.
* A 150-m depth rating with 140-mm drill pipe.
* A dual drill pipe capability.
Final drill rig design also involved meeting all federal government mine safety requirements, Alberta occupational health and safety standards as well as all related Alberta Energy Resources Conservation Board regulations.
While the drill rig was in the construction phase, aostra completed the underground mine about 50 km northwest of Fort McMurray, Alta. Pilot phase “A” includes two main shafts 250 m deep, utilizing 3.9-m steel cribbing. About 750 m of drifts have been constructed for this test phase. Drilling chambers four m high by seven m wide have been widened from the planned 4×5-m drifts.
The drilling program under pilot phase “A” provides for a series of six wells, 160 m deep, and possibly two test wells 660 m deep. All wells will be drilled upslope at a 17 degrees angle from the horizontal, through 30 m of limestone and into the oil-bearing formation above. The wells will be drilled in pairs.
The upper well will be used for production. Each hole will be drilled with a dual pipe system. The inner pipe is required for the directional drillng guidance system and for pressure control. An optical survey tool supplied by Abem Fotobar (Sweden) provides the capability of directional guidance to an accuracy of one m in 1,000 m. A mud system with a capacity of 500 gal per min at 2,000 lb per sq in as well as a 1,500-cu-ft-per-min- at-300-lb-per-sq-in air-compressor will be located on the surface. All drill holes will require the use of a blowout preventor and the installation of casing.
Once the bitumen recovery concept has been proven, pilot phase “B” will be implemented and the mine will be expanded to incorporate additional drifts. Wells in this phase will be 660 m long. Bruce Sutherland is general manager of Drill Systems International in Calgary, Alta.
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