Abstract: A system for downhole drilling and coring includes a roller vane motor for driving a drill bit. The motor has a single jacket with a lower end and an upper end and being embodied such that all drilling fluid passes inside the jacket to the drill bit. The system further has a bent sub connected to the upper end of the motor. The jacket has outwardly projecting curved members forming recesses therebetween for the passage of return drilling fluid, the curved members creating a circular surface having a diameter approximately equal to that of the drill bit. The curved members as well as the recesses therebetween each extend in longitudinal direction over the full length of the jacket of the motor.

Abstract: A system for downhole drilling and coring, said system includes a roller vane motor for driving a drill bit. The motor has a single jacket with a lower end and an upper end and being embodied such that all drilling fluid passes inside the jacket to the drill bit. The system further has a bent sub connected to the upper end of the motor. The jacket is provided with outwardly projecting curved members forming recesses therebetween for the passage of return drilling fluid, the curved members creating a circular surface having a diameter approximately equal to that of the drill bit. The curved members as well as the recesses therebetween each extend in longitudinal direction over the full length of the jacket of the motor.