Downhole rotary drive apparatus

A downhole tool for drilling or reaming a borehole, the downhole tool comprising:

• a bit;
• and
• an apparatus comprising:
• a body configured for coupling to, or forming part of, a tubular string for running into the borehole, wherein the body comprises one or more radially-projecting blade portions;
• an output shaft at least partially disposed within and rotatably mounted to the body, wherein the output shaft is configured for coupling to the bit such that rotation of the output shaft relative to the body drives rotation of the bit;
• a plurality of rotary drives disposed around the body, wherein each of the plurality of rotary drives comprises a respective rotor;
• and
• a transmission arrangement for converting rotation of the rotors of the rotary drives into rotation of the output shaft,
• wherein the transmission arrangement comprises a drive component mounted on at least one of the drive shafts of the plurality of rotary drives and a driven component mounted on the output shaft, the driven component being disposed radially inwards of the drive component such that an inner surface of the drive component engages an outer surface of the driven component so that rotation of the driven component by the drive component drives rotation of the output shaft, and
• wherein at least part of the rotary drives and/or part of the transmission arrangement are disposed within the blade portions.

A downhole assembly comprising:

• a downhole tool comprising:
• a bit;
• a body configured for coupling to, or forming part of, a tubular string for running into the borehole, wherein the body comprises one or more radially-projecting blade portions;
• an output shaft at least partially disposed within and rotatably mounted to the body, wherein the output shaft is configured for coupling to the bit such that rotation of the output shaft relative to the body drives rotation of the bit;
• a plurality of rotary drives disposed around the body, wherein each of the plurality of rotary drives comprises a respective rotor;
• and
• a transmission arrangement for converting rotation of the rotors of the rotary drives into rotation of the output shaft,
• wherein the transmission arrangement comprises a drive component mounted on at least one of the drive shafts of the plurality of rotary drives and a driven component mounted on the output shaft, the driven component being disposed radially inwards of the drive component such that an inner surface of the drive component engages an outer surface of the driven component so that rotation of the driven component by the drive component drives rotation of the output shaft, and
• wherein at least part of the rotary drives and/or part of the transmission arrangement are disposed within the blade portions;
• and
• a tubular string.

A method for drilling a borehole;

• comprising:
• using a downhole tool comprising:
• a bit;
• and
• an apparatus comprising:
• a body configured for coupling to, or forming part of, a tubular string for running into the borehole, wherein the body comprises one or more radially-projecting blade portions;
• an output shaft at least partially disposed within and rotatably mounted to the body, wherein the output shaft is configured for coupling to the bit such that rotation of the output shaft relative to the body drives rotation of the bit;
• a plurality of rotary drives disposed around the body, wherein each of the plurality of rotary drives comprises a respective rotor;
• and
• a transmission arrangement for converting rotation of the rotors of the rotary drives into rotation of the output shaft,
• wherein the transmission arrangement comprises a drive component mounted on at least one of the drive shafts of the plurality of rotary drives and a driven component mounted on the output shaft, the driven component being disposed radially inwards of the drive component such that an inner surface of the drive component engages an outer surface of the driven component so that rotation of the driven component by the drive component drives rotation of the output shaft, and
• wherein at least part of the rotary drives and/or part of the transmission arrangement are disposed within the blade portions.