Electric submersible pump, tubing and method for borehole production

A pumping system for pumping well fluid from a borehole, the system comprising a production tube and an electric submersible pump assembly,

• the electric submersible pump assembly including a motor and a pump, the pump having an inlet and an outlet,
• and a tether for lowering the electric submersible pump assembly down the production tube into a deployed position,
• wherein the production tube has an upper portion proximate an upper end thereof, the upper portion defining a first inner wall, and an enlarged diameter portion defining a second inner wall below the upper portion, the second inner wall having a greater diameter than the first inner wall;
• and the motor is located within the enlarged diameter portion in the deployed position,
• such that in the deployed position the motor is spaced apart from the second inner wall by a gap through which fluid can flow entirely around the motor.

An electric submersible pump assembly for deployment within a production tube in a borehole for pumping well fluid therefrom,

• the electric submersible pump assembly including a motor and a pump, the pump having an inlet and an outlet,
• and a tether for lowering the electric submersible pump assembly down the production tube to a deployed position,
• wherein the tube has an upper portion proximate an upper end thereof and an enlarged diameter portion below the upper portion, and the motor is located within the enlarged diameter portion in the deployed position,
• wherein the electric submersible pump assembly includes a plurality of stabilising elements spaced apart around the electric submersible pump assembly and extending radially outwardly to engage the production tube,
• the stabilising elements being arranged to space the motor from the production tube so as to define a conduit therebetween sufficient for the passage of the well fluid passing through the pump.

A method for preventing overheating in an electric submersible pump producing well fluid from a borehole, comprising the steps of:

• arranging a production tube in the borehole, the production tube having an upper portion proximate an upper end thereof, the upper portion defining a first inner wall, and an enlarged diameter portion defining a second inner wall below the upper portion, the second inner wall having a greater diameter than the first inner wall;
• introducing an electric submersible pump assembly into the upper end of the tube, the electric submersible pump assembly having a motor and a pump, the pump having an inlet and an outlet;
• and
• lowering the electric submersible pump assembly down the upper portion of the tube to a deployed position in which the motor is positioned within the enlarged diameter portion of the tube,
• so as to define a conduit between the motor and the second inner wall of the tube sufficient for the passage of the well fluid passing through the pump, wherein the conduit extends entirely around the motor.