Patent ID: 8511906

Claim:
A bearing section for a mud motor, comprising: an elongate mandrel rotatably and coaxially disposed within an elongate cylindrical housing; said mandrel having an upper end, a lower end, an outer surface extending from the upper end to the lower end, and a central bore extending from the upper end to the lower end; an annular first bearing chamber radially disposed between the mandrel and the housing, the first bearing chamber having a lower end defined by an annular abutment associated with the housing and an upper end defined by a lower end of a cylindrical drive shaft adapter mounted to the upper end of the mandrel; a mud-lubricated thrust bearing assembly disposed within said first bearing chamber axially adjacent the lower end of the first bearing chamber, wherein the mud-lubricated thrust bearing assembly is configured to support compressional loads between said annular abutment and said drive shaft adapter when the bearing section is under axial tension; an annular space disposed between the drive shaft adapter and the housing, wherein the annular space is in fluid communication with the first bearing chamber and is configured to flow drilling fluid into the first bearing chamber; one or more ports extending through the mandrel from the first bearing chamber to the central bore, wherein the one or more ports are configured to flow drilling fluid from the first bearing chamber into the central bore; an annular oil reservoir radially disposed between the mandrel and the housing, and extending axially between an upper rotary seal positioned between the mandrel and the housing and a lower rotary seal positioned between the mandrel and the housing, a portion of said oil reservoir defining an annular second bearing chamber, wherein said second bearing chamber has a lower end bounded by an annular lower shoulder associated with the mandrel and an upper end bounded by an annular upper shoulder associated with the housing; and a thrust bearing disposed within said second bearing chamber, wherein said thrust bearing is configured to support compressional loads between said upper and lower shoulders when the bearing section is under axial compression.