Apparatus and method for high temperature drilling operations

Abstract

An apparatus (50) for drilling a wellbore that transverses a subterranean hydrocarbon bearing formation. The apparatus (50) includes a drill string (52) having an inner fluid passageway (66). A drill bit (64) is disposed at a distal end of the drill string (52) and is operable to rotate relative to at least a portion of the drill string (52). A fluid motor (54) is disposed within the drill string (52) and is operable to rotate the drill bit (64) in response to a circulating fluid received via the inner fluid passageway (66) of the drill string (52). The fluid motor (54) has a stator (68) with (n) lobes and a rotor (70) with (n−1) lobes. The stator (68) includes an inner surface formed from a first material and the rotor (70) includes an outer surface formed from a second material that is dissimilar to the first material.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS[0001]This is a continuation-in-part application of copending application Ser. No. 12 / 002,710, filed on Dec. 18, 2007.TECHNICAL FIELD OF THE INVENTION[0002]This invention relates, in general, to rotor and stator assemblies for use in fluid motors and progressive cavity pumps and, in particular, to an improved rotor and stator assembly for use in high temperature operations.BACKGROUND OF THE INVENTION[0003]Without limiting the scope of the present invention, its background will be described with reference to stator and rotor assemblies of power sections of positive displacement fluid motors for use in downhole drilling operations, as an example.[0004]In a typical power section of a positive displacement fluid motor used in drilling a wellbore that traverses subterranean hydrocarbon bearing formations, power generation is based upon the Moineau pump principle. In this type of motor design, a stator and rotor assembly converts the hydraulic...

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