Patent ID: 7757781
Filing Date: 2010-07-20
Classification: E21B,F04C

Abstract:
1. A downhole motor assembly for driving a drill bit to form a borehole, the downhole motor assembly including: a hydraulic drive section operatively connected to the drill bit and a drill string, the hydraulic drive section including a stator and a rotor located inside the stator, the stator and rotor forming a flow path between the stator and the rotor such that fluid flowing through the flow path in response to a pressure differential across the hydraulic drive section creates an operative force to rotate the drill bit; and a regulation mechanism including a valve and a fluid flow diversion bore for diverting at least some fluid from the flow path when the pressure differential across the hydraulic drive section is greater than or equal to a transition pressure differential, wherein the fluid flow diversion bore extends radially outward through the stator to an annulus between the drill string and a sidewall of the borehole.