1999 saw a lot of well tractors introduced. Now there's a device that has a brain and goes downhole with instructions, recording devices and a payload. It operates on internal battery power and has no hard link back to the surface. It's being tested in the hope it can do the work of a well tractor and then some.
The device follows the directions of an internal computer and software. So it is more than an untethered, smart tractor. You could call it a robot. That's the designation given it by its manufacturer, IIC Corp. of Newton, Mass. IIC has named the device the Micro Rig and classifies it as a free-roving robot with one degree of freedom - in other words, it can move through a single dimension. IIC developed it in an early partnership with Baker Hughes, and it has performed well in lab tests and field demonstrations.
Now IIC has formed a consortium with BP Amoco and Marathon to put the Micro Rig through field trials and prove it as a commercial working system. The project is expecting a third partner and open to a fourth, said IIC director of technology Thomas McIntyre. Barring unforeseen complications, he said, "We expect to see a small fleet of Micro Rigs by the end of this year."
Caterpillar treads (left in photo) drive the Micro Rig forward and backward with idler wheels spring-loaded to press the treads against the borehole wall. Loading of the idler wheels is completely passive and nominally 60lb per idler. For power, the caterpillar tread passes over an internal drive sprocket driven by an electric motor. Lithium battery cells that place 250lb force at each end of the Micro Rig's drive unit power it. The tool can carry a 250lb payload.
Micro Rig can be set into a lubricator for introduction into the wellbore. The drive section contains a computer programmed at the surface with the tool's downhole routine. Other sections contain devices that measure pressure and temperature and induce magnetic and gamma radiation for logging. The magnetic section is hypersensitive to collars, and when combined with pick-offs in the caterpillar drive, enables the tool to compute its depth and go to a preset spot.
The Micro Rig watches out for itself. If the temperature gets too high, it backs up and leaves. Similarly, Micro Rig will not pass rotten pipe that could trap it downhole, nor will it enter a tight spot detected when its motor current increases above preset limits. When it returns to the surface, it brings along a record of why it returned.
"We built the Micro Rig with plenty of power and engineered so it can go beyond logging chores and place and remove downhole tools, actuate devices and work as a fishing tool," McIntyre said.
Part of the upcoming field trials will obtain fingerprints for library use by the internal software. The collar locator will be calibrated to recognize such downhole hardware as sidepockets, sleeves and laterals. Well production operations such as logging, plugging and perforating will be conducted. For most wells, adequate annular space around the Micro Rig should allow production operations to proceed normally. Other plans for the field trials include testing gamma radiation detectors and building a heftier Micro Rig for 3¾- to 7½in. wellbores and larger tubing sizes.
During field trials IIC plans to test the Micro Rig in open holes. The caterpillar tread drive makes it different from either the wheeled or anchored type of tractor drive though it is more like the anchored devices.
McIntyre expects to confirm depth capability to 25,000ft measured depth and 15,000ft true vertical depth. One aspect of the upcoming trials will be tests of installation and recovery of the Micro Rig in subsea riserless interventions.
IIC was scheduled to begin engineering design and conduct a few more lab tests (battery life to failure, operations in heavy debris) in early January prior to the field trials. For more information, E-mail tom@iitech.com.
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