Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
  • E21B43/12—Methods or apparatus for controlling the flow of the obtained fluid to or in wells
  • E21B43/121—Lifting well fluids
  • E21B43/128—Adaptation of pump systems with down-hole electric drives
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B17/00—Pumps characterised by combination with, or adaptation to, specific driving engines or motors
  • F04B17/03—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by electric motors
  • F04B17/04—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by electric motors using solenoids
  • F04B17/046—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by electric motors using solenoids the fluid flowing through the moving part of the motor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B47/00—Pumps or pumping installations specially adapted for raising fluids from great depths, e.g. well pumps
  • F04B47/06—Pumps or pumping installations specially adapted for raising fluids from great depths, e.g. well pumps having motor-pump units situated at great depth

Definitions

• the present invention relates to an electric pump with a linear motor, and more particularly to such an electric pump intended to be installed at the bottom of a well, for example an oil well.
• an assistance system or well activation system can be used.
• Stem pumping systems consist of a volumetric bottom pump installed in the casing, the piston of which is driven in translation from the surface by means of steel or fiberglass rods. On the surface, the movement is given to the drill string by a balance structure driven by a rotary electric motor or a hydraulic cylinder.
• the dead weight, inertia, friction and mechanical fatigue of the rods limit the pumping capacity and performance of these systems. They are unsuitable for eruptive wells on which bottom safety devices are required, deep wells or high flow rates (greater than 200 m ⁇ / d of liquid).
• the pump can be driven by an electric motor immersed in the bottom of the well which is supplied by a cable arranged in the annular space between the casing and the casing of the well.
• an electric motor immersed in the bottom of the well which is supplied by a cable arranged in the annular space between the casing and the casing of the well.
• An example of this type of pump is given in document US Pat. No. 4,928,771 which describes a rotary pump driven by an electric motor, placed in the well above the pump.
• This type of pump has drawbacks, firstly because it is bulky, the pump and the motor forming two separate units, and, moreover, because the two units are immersed in the fluid flowing in the well. This fluid constitutes an aggressive medium which is at the origin of a significant number of failures undergone by this type of pump.
• Electropumps powered by linear motors have also been proposed.
• a linear electric motor drives the piston of a reciprocating pump.
• Document US Pat. No. 4,687,054 describes an electric motor with a linear motor intended to be placed at the bottom of an oil well, the linear motor being arranged above the pump which forms a separate sub-assembly.
• the fact that the motor and the pump form two separate sub-assemblies makes the electric pump bulky and heavy.
• the operations of installing the electropump in the well, operations which are carried out by cable or by means of a small diameter tube and its periodic removal for maintenance, are made more difficult and laborious by the presence of the two and their weight.
• an electric pump formed of two sub-assemblies has a high inertia, and in addition, the connection between the sub-assemblies constitutes a weak point of one electric pump.
• the present invention therefore relates to a linear motor electric pump which is simple, compact and reliable in construction and which makes it possible to remedy the drawbacks mentioned above.
• the invention provides an electric pump comprising a linear motor formed by a stator and a mobile element displaceable under the effect of the electromagnetic field generated by the stator, a pump piston displaceable by the linear motor at l inside the stator of the electric pump and constituting the movable element of the linear motor, the piston comprising a non-return valve, the electric pump further comprising a non-return valve fixed relative to the piston, characterized in that the non-return valve is arranged at the end of the piston in order to reduce to a minimum the dead volume between the two non-return valves and of a movable element displaceable under the effect of electromagnetic field generated by the stator, and a pump piston displaceable by the linear motor characterized in that the piston is placed inside the stator of the electropump and constitutes the mobile element of the linear motor.
• the invention also provides an installation for an oil well extending from the surface to a layer of petroleum rock comprising a casing arranged in the well and forming a flow path towards the surface for hydrocarbons coming from the rock layer.
• petroleum a pump arranged in the casing and comprising a piston, forming the movable element of a linear motor, the piston comprising a non-return valve
• the installation comprising, in addition, a non-return valve fixed relative to the piston, characterized in that the non-return valve is arranged at the end of the piston in order to reduce to a minimum the dead volume between the two non-return valves.
• FIG. 1 is a schematic sectional view of an oil well provided with a linear motor electric pump according to the invention
• FIG. 2 is a schematic sectional view of an electropump with a linear motor according to the invention.
• FIG. 1 is shown, generally at 10, an installation for an oil well in which a well
• the well 12 extends between the surface 14 and a layer of petroleum rock 16.
• the well 12 has a casing 18 which makes the well tight with respect to the layers of rock crossed by the well.
• a production casing 20 between a well head, represented schematically at 22, and a seal 24, more commonly called “packer” which is arranged, for example, at about 100 m above above the level of the oil rock 16.
• a sealed chamber 26 is defined between the outer wall of the casing 20 and the inner wall of the casing 18.
• a safety valve 27 is placed in the casing 20 at about 50 m from the surface 14.
• the casing 20 comprises, towards its lower end, an electric pump, generally represented at 28 which comprises a reciprocating pump 30 intended to be actuated in the direction of the arrow 32 by a linear electric motor 34.
• the electric motor linear 34 which, in the example illustrated, is three-phase, is supplied from the surface 14 by an electric cable 38 placed in the chamber 26.
• the electrical supply can be made by the casing 20 and the casing 18, isolated from each other by non-conductive separators (not shown). Such an electrical supply makes it possible to dispense with the use of the cable 38.
• the linear motor 34 comprises a stator 40 and a mobile element 42 which can be displaced under the effect of the magnetic field generated by the stator.
• the stator 40 is mounted outside the casing 20 inside the chamber 26.
• the casing 20, at least in the region 43 adjoining the linear motor 34, is formed from magnetic material, chosen for example from ceramic bronze or chrome.
• the movable element 42 as well as the part 43 of the casing, are arranged and dimensioned so as to allow the casing to be removed from the movable element 42.
• the movable element 42 is provided, at its upper end with a head attachment 44 which makes it possible to raise it to the surface, for example by means of a cable or a tube with a small diameter, more commonly called "coiled tubing".
• the lower end of the casing 20 is provided with a non-return valve 46 allowing the flow of fluid, coming from the oil layer 16, towards the electric pump 28 in the direction of the arrows 48. This valve can advantageously be arranged to allow it to be brought up to the surface using a cable.
• the mobile element 42 of the linear motor 34 also forms the piston of the electric pump 28.
• This mobile element 42 comprises an armature 50, formed, for example, of several laminated magnetic sections 52 preferably made of soft iron.
• the movable element At its lower end, the movable element comprises a non-return valve 54 allowing the passage of fluid, coming from the bottom of the well, towards the surface.
• This configuration is particularly conducive to pumping efficiency when the effluent contains high proportions of gas.
• the non-return valve can alternatively be mounted at the upper end of the movable element. This type of arrangement can be used particularly when the effluent to be pumped contains little or no gas.
• the movable element 42 When the linear motor is energized, the movable element 42 is driven in axial movement in the direction of the arrow 56, displacing towards the surface 14 the fluid present in the casing 20. Then the movable element descends to its initial position , closest to the lower end of the casing 20, the non-return valve 54 opens to allow the fluid present between the closed non-return valve 48 and the piston of the electropump to pass through the movable element 42 by an axial passage 58.
• the movable element can descend under the effect of its own weight, or by actuating the linear motor in the opposite direction.
• the duration of a pumping cycle depends on the axial length of the stator. This length may possibly exceed 10 m.
• a long stroke of the piston of the electric pump has the advantage of reducing the number of operations of the non-return valves 46 and 54.
• a long stroke of the electric pump is particularly suitable when The pumped effluent is heavy or heavily gaseous crude oil.
• the non-return valve 54 or discharge valve, is disposed at the lower end of the mobile element 42 which forms the piston of the electric pump 28.
• the mobile element 42 When the mobile element 42 is in its most extreme lower position, that is to say when this element is closest to the non-return valve 46, the dead volume between the two valves is reduced to a minimum. This results in increasing the efficiency of the pump.
• the speed of movement of the piston of the electric pump can be varied as a function of the characteristics of the effluent to be pumped, by using a frequency converter arranged in the electrical supply circuit of the stator.
• the linear motor 34 is cooled by the extracted effluent which passes through the axial passage 58.
• the chamber 26 containing the stator 40 and the electric cable 38 can, in a preferred embodiment, receive a dielectric substance, a liquid or a frost, to further strengthen the sustainability of the installation.
• the use of a gel also has the advantage of thermally insulating the tubing, which thus retains all the heat of the fluid including that received from the engine, as well as that dissipated by the cable 38 which runs along the casing, the latter itself acting as a cooling radiator. This thermal insulation will ensure a better overall energy efficiency of the installation, by facilitating the flows.
• the lubrication between the mobile and fixed parts is done with suitable non-magnetic materials (ceramic, zirconium, teflon, carbides or bronze), and / or with an effluent film put in place by hydrodynamic effect.
• suitable non-magnetic materials ceramic, zirconium, teflon, carbides or bronze
• a parallel lubrication system could also be implemented.
• the pump can also be easily placed below or above the motor, which offers more flexibility in the architecture of completions, and possible improvements for certain types of effluents, especially viscous or gassed, beneficial to the production performance of the well.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Fluid Mechanics (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
• Reciprocating Pumps (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1996
  • 1996-03-29 FR FR9603999A patent/FR2746858B1/fr not_active Expired - Lifetime
• 1997
  • 1997-03-27 US US08/952,490 patent/US5960875A/en not_active Expired - Lifetime
  • 1997-03-27 EP EP97919436A patent/EP0840855A1/de not_active Withdrawn
  • 1997-03-27 WO PCT/FR1997/000561 patent/WO1997037131A1/fr not_active Ceased

Non-Patent Citations (1)

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