Rotary Steering System
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MWD Sub
Reservoir Navigation Sensor Sub
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Top Stabilizer
Alternator/Pulser Sub
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Non Rotating Sleeve With Steering Ribs
Drive Sub
Figure 10 Rotary steering system (Courtesy of Baker Hughes Inteq.)
The rotary steering system described here operates on the priciple of the application of a sideforce in a similar way to the non-rotating systems described above. However, in these systems it is also possible to rotate the drillstring even when drilling directionally or as described above when in the "oriented mode" of drilling. It is therefore possible to rotate the string at all times during the drilling operation. This is desirable for many reasons but mostly because it has been found that it is much easier to transport drilled cuttings from the wellbore when the drillstring is rotating. When the drillstring is not rotating there is a tendency for the cuttings to settle around the drillstring and it may become stuck.
There are a number of tools which have been developed in order to allow the string to be rotated whilst drilling in the oriented mode but only one of these devices will be described below. Other systems (developed and offered by other service companies) can be found on the internet.
The main elements of the rotary steerable steering system that is described here (the AutoTrak" RCLS system) are the: Downhole System and the Surface System