Cutting tool and method for cutting tubular member

A downhole cutting tool assembly for use at the downhole end of an elongate conduit in a well, the assembly comprising:

• a fluid-driven downhole motor adapted to receive only a single source of fluid, the motor comprising:
• a tubular housing with an uphole end and a downhole end, wherein the uphole end is removably connectable to the elongate conduit and comprises a single fluid inlet continuous with the elongate conduit;
• a rotor with a downhole end, the rotor being supported in the housing and sized to form an annular fluid flow space between the rotor and the housing, the annular fluid flow space continuous with the fluid inlet in the uphole end of the housing whereby the rotor is rotatable in response to the flow of fluid from the elongate conduit through the annular fluid flow space;
• and
• an output shaft having an uphole end and a downhole end, the uphole end fixed to the downhole end of the rotor and adapted to rotate with the output shaft at the same speed as the rotor, wherein the downhole end of the output shaft comprises a single outlet by which fluid exits the motor and continuous with the fluid flow space between the housing and the rotor;
• and
• a cutting tool comprising a body with an uphole end and having a longitudinal axis, wherein the uphole end is removably connectable to the downhole end of the output shaft of the downhole motor for rotation therewith at the same speed as the rotor, the cutting tool comprising a fluid conduit continuous with the single outlet in the downhole end of the output shaft when the uphole end of the cutting tool is connected thereto, and wherein the body comprises at least one port in fluid communication with the fluid conduit, the at least one port positioned to direct fluid from the fluid conduit out of the body at an angle to the longitudinal axis of the body;
• whereby, when the tool assembly is in operation, a single source of fluid passing through the motor and the cutting tool drives the motor and serves as the sole cutting element of the tool.