Mud-lubricated bearing assembly with mechanical seal

摘要

In a mud-lubricated bearing assembly for a downhole motor, a mechanical seal is provided between the mandrel and the lower end of the bearing housing to prevent discharge of drilling fluid (mud) from the bearing assembly into the wellbore annulus. The mechanical seal is effected by mating wear-resistant annular contact surfaces provided on the mandrel and the bearing housing, with biasing means preferably being provided to keep the contact surfaces in sealing engagement during both on-bottom and off-bottom operational modes. The diverted drilling fluid passing through the bearings is redirected into the bore of the mandrel via ports through the mandrel wall to rejoin the main flow to the drill bit, such that substantially all of the drilling fluid flows through the bit.

主权项

1. A mud-lubricated bearing assembly comprising:
a generally cylindrical housing; an elongate mandrel having a longitudinal bore, said mandrel being coaxially disposed within the housing and being rotatable relative to the housing; a thrust bearing configured to transfer axial on-bottom loads and off-bottom loads from the mandrel to the housing; a radial bearing disposed within the annular space between the mandrel and the housing and configured to maintain coaxial alignment of the mandrel and the housing; an annular lower seal ring coaxially and non-rotatably secured to a lower region of the mandrel, said lower seal ring having an annular upper seal surface in a plane perpendicularly transverse to the longitudinal axis of the mandrel; and an annular upper seal ring mounted to a lower region of the housing such that the upper seal ring is non-rotatable relative to the housing and axially movable relative to the housing within a defined range of travel, said upper seal ring having an annular lower seal surface matingly engageable with the upper seal surface of the lower seal ring; wherein the mandrel includes one or more fluid ports configured to allow fluid flow into the mandrel bore from an annular space between the mandrel and the housing.