E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
E21B 4/00 (2006.01)
Patent
CA 2353113
A flow retarder is provided for use in the bearing assembly of a downhole drilling motor. The bearing assembly is connected to the motor power section by an inner tubular adapter and an outer tubular adjustable housing, which between them define a clearance through which drilling fluid from the motor can move. The bearing assembly comprises an inner tubular mandrel and an outer tubular housing. The flow retarder is positioned at the upper end of a pressure balancing chamber, formed between the mandrel and housing. This chamber also contains a floating piston seal at its lower end. The flow retarder functions as a seal which restricts the entry of drilling fluid from the adapter/adjustable housing clearance into the pressure balancing chamber. It also substantially isolates the pressure balancing chamber from the high pressure present in the drilling fluid moving down from the motor power section, and it enables equalization of the pressure internal of the chamber with the annulus/wellbore pressure external of the bearing assembly. The flow retarder comprises: an inner carbide sleeve connected to the rotating mandrel by a resilient elastomer layer bonded to a driver ring which is locked on the rotating mandrel; an outer carbide sleeve affixed to the stationary tubular housing; the sleeves forming a narrow annular clearance or metering gap between them; a secondary port extending through the mandrel side wall directly above the carbide sleeves; and a housing port extending through the housing side wall below the flow retarder sleeves. Drilling fluid leaks down from the adapter/adjustable housing clearance and passes through the metering gap to lubricate 14 the carbide sleeves. Part of this fluid returns through the secondary port to the main bore of the mandrel. By providing the elastomer layer, the transmission of radial loads from the inner sleeve to the outer sleeve is reduced. As a consequence, wear of the sleeves is reduced and the gap can be maintained narrower, thereby minimizing loss of drilling fluid through the flow retarder and providing more effective metering of the drilling fluid.
Cavare Ltd.
Parlee Mclaws Llp
Robin Lawrence E.
LandOfFree
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