Process for pumping a gas/liquid mixture in an oil extraction well and device for implementing the process

Claim 1

A process for pumping a two-phase gas/liquid mixture in an extraction well whose initial gas percentage is greater than approximately 40% by volume, comprising: passing said mixture through at least a first centrifugal separating module to reduce the percentage of free gas in said mixture to below 40%; passing the mixture which emerges from said first separating module annularly around a drive motor to cool said motor; passing the mixture through at least a second centrifugal separating module to reduce the percentage of free gas in said mixture to below about 10% by volume; and pumping the mixture emerging from said second centrifugal module by means of a centrifugal pump driven by said drive motor.

Claim 5

An apparatus for pumping a two-phase gas/liquid mixture in an extraction well whose initial gas percentage is greater than approximately 40% by volume, comprising: a first centrifugal separating module having a cylindrical casing providing for axial flow of the gas/liquid mixture and means for discharging the separating gases outside the casing; a cooling module comprising an outer casing connected in a sealing manner to the casing of the first separating module and, within said outer casing, a second coaxial cylindrical casing containing a motor which is surrounded on either side, in the longitudinal direction, by means for maintaining a seal towards the upstream and downstream sides at the level of the drive spindles of the motor; means for diverting the axial flow of the gas/liquid mixture outside the second casing at the entry of the cooling module; and means at the exit of the cooling module for bringing the flow along the axis of a centrifugal pumping module connected to a pipe string for discharging the fluid, the pumping module and separator being driven by the motor.

Claim 6

An apparatus for pumping a two-phase gas/liquid mixture in an extraction well whose initial gas percentage is greater than approximately 40% by volume, comprising: a first centrifugal separating module having a cylindrical casing providing for axial flow of the gas/liquid mixture and means for discharging the separating gases outside the casing; a cooling module comprising an outer casing connected in a sealing manner to the casing of the first separating module and, within said outer casing, a second coaxial cylindrical casing containing a motor which is surrounded on either side, in the longitudinal direction, by means for maintaining a seal towards the upstream and downstream sides at the level of the drive spindles of the motor; means for diverting the axial flow of the gas/liquid mixture outside the second casing at the entry of the cooling module; and means at the exit of the cooling module for bringing the flow along the axis of a centrifugal pumping module connected to a pipe string for discharging the fluid, the pumping module and separator being driven by the motor.