Wellbore desanding system

Abstract

The invention relates to system and method for desanding an oil well that includes a fluidizing device (TORE), connected to a downhole pump that connects to a production tubing such that a supply duct is connected to the discharge of the pump and a discharge duct is connected to the suction of the pump. Embodiments include a pressure balance transition device between the TORE and the pump and/or a flow splitting device in the production tubing after the discharge of the pump. Other embodiments relate to a system and method for desanding an oil well in which a fluidizing unit is connected to a pump such that the supply duct is connected to an opening in the pump body or pump rotor and a discharge duct is connected to the suction of the pump. If connected to the rotor, the supply duct is integral to the pump rotor.

Claims

1. A lift pump for use in a wellbore system including a production tubing and a fluidizing device configured for desanding the wellbore, the pump comprising: a suction port configured for receiving fluid from the fluidizing device; a priming rotor section rotatable in a priming stator section; a discharge port configured for passing the fluid to a chamber; a supply duct connected to the chamber and configured for feeding a portion of the fluid to the fluidizing device; and a production rotor section rotatable in a production stator section and configured for passing a reminder portion of the fluid to the production tubing, wherein the priming rotor section is rotationally coupled to the production rotor section.

2. The pump of claim 1, wherein the supply duct is integral with the priming rotor section.

3. The pump of claim 1, wherein the supply duct is external to a pump casing.

4. The pump of claim 1, further comprising a discharge duct connected between the suction port of the pump and the fluidizing device.

5. The pump of claim 4, wherein the discharge duct comprises a pressure balance transition device including inlets configured for entering wellbore fluid, and a low pressure zone, wherein the pressure balance transition device is configured for mixing the wellbore fluid with the fluid received from the fluidizing device.

6. The pump of claim 5, wherein the pressure balance transition device further includes a flow restriction area for generating the low pressure zone.

7. A method of lifting fluid from a wellbore, comprising: placing a production tubing and a fluidizing device configured for desanding the wellbore in the wellbore; rotating a priming rotor section within a priming stator section for sucking fluid from the fluidizing device; discharging the fluid into a chamber; rotating a production rotor section rotationally coupled to the priming rotor section within a production stator section for passing a portion of the fluid from the chamber to the production tubing; and feeding a remainder portion of the fluid to the fluidizing device via a supply duct connected to the chamber.

8. The method of claim 7, wherein the fluidizing device is placed below casing perforations.

9. The method of claim 7, further comprising: entering wellbore fluid in a pressure balance transition device; and mixing the wellbore fluid with the fluid received from the fluidizing device in the pressure balance transition device.

10. The method of claim 9, further comprising generating a low pressure zone in the pressure balance transition device using a flow restriction area.

11. A lift pump for use in a wellbore system including a production tubing and a fluidizing device configured for desanding the wellbore, the pump comprising: a suction port configured for receiving fluid from the fluidizing device; a priming rotor section connected to the suction port and rotatably disposed in a priming stator section; a discharge port connecting the priming rotor section to a chamber to pass the fluid to the chamber; a supply duct connecting the chamber to the fluidizing device to feed a portion of the fluid to the fluidizing device; and a production rotor section connecting the chamber to the production tubing and rotatably disposed in a production stator section to pass a reminder portion of the fluid to the production tubing, wherein the priming rotor section is rotationally coupled to the production rotor section.

12. The pump of claim 11, wherein the supply duct is integral with the priming rotor section.

13. The pump of claim 11, wherein the supply duct is external to a pump casing.

14. The pump of claim 11, further comprising a discharge duct connected between the suction port of the pump and the fluidizing device.

15. The pump of claim 14, wherein the discharge duct comprises a pressure balance transition device including inlets configured for entering wellbore fluid, and a low pressure zone, wherein the pressure balance transition device is configured for mixing the wellbore fluid with the fluid received from the fluidizing device.

16. The pump of claim 15, wherein the pressure balance transition device further includes a flow restriction area for generating the low pressure zone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An example of an oil-well and associated system, constructed in accordance with the present invention is illustrated diagrammatically in the accompanying drawings in which:

(2) FIG. 1 schematically shows a partial view, in longitudinal section, of an embodiment of the present invention.

(3) FIG. 2 schematically shows a partial view, in longitudinal section, of an alternate embodiment of the present invention in which the supply duct is connected to an opening in the pump body or stator.

(4) FIG. 3 schematically shows a partial view, in longitudinal section, of an alternate embodiment of the present invention in which the supply duct is connected to an opening in the pump rotor.

DETAILED DESCRIPTION

(5) In accordance with the present invention, a wellbore desanding system is provided that comprises a fluidizing device at the bottom of the well, placed, for example, below the casing perforations in the bottom of the well, to continuously fluidize and lift solids from the well bottom thereby preventing accumulation of solids in the well that can stop the flow of fluids into the well, wherein the fluidizing device is connected to a pump such that the supply duct (water supply conduit for example) is connected to the discharge of the pump and a discharge duct is connected to the suction of the pump. Artificial lift of heavy oil with sand is primarily carried out by progressive cavity pumps or jet pumps. The current invention can be adapted to be used with any type of a downhole pump including progressive cavity and jet pumps.

(6) Also in accordance with the present invention, a wellbore desanding system is provided that comprises a fluidizing device at the bottom of the well, placed, for example, below the casing perforations in the bottom of the well, to continuously fluidize and lift solids from the well bottom thereby preventing accumulation of solids in the well that can stop the flow of fluids into the well, wherein the fluidizing device is connected to a pump such that the supply duct (water supply conduit for example) is connected to an opening in the pump body or pump rotor and a discharge duct is connected to the suction of the pump.

(7) Fluids entering an oil production well from an oil bearing reservoir must travel up through the well to reach the surface. The fluid pathway from the reservoir to the surfaces is usually as follows: 1. fluid passes from the reservoir through perforations in the well casing to enter the bottom of the well; 2. fluid travels up through the well casing to a pump which boosts the pressure of the fluid giving it the energy it needs to travel to the surface; 3. fluid exits the pump and enters the bottom of a small diameter production tubing; and 4. fluid travels up the production tubing to the surface. The velocity of the fluids travelling up the wellbore changes depending on the diameter of the conduit it is flowing through according to the formula

(8) $v=\frac{4*Q}{\pi *d^2}$
Where: v=velocity, Q=flow rate and d=conduit diameter
Therefore, the fluids flowing through the large wellbore casing at the bottom of the well travel upwards at much lower velocity than fluids flowing through the production tubing.

(9) Sand will fall downward through the upward flowing fluid at a velocity that is dependent on the size of the sand grains. In order to lift the sand from the well, the velocity of the fluid in the upward direction must be greater than the velocity of the sand falling through the fluid. Once the sand reaches the smaller diameter production tubing, the upward velocity within the tubing is high enough to carry the sand all the way to the surface. The desanding system of the current invention comprises a means for fluidizing the sand that settles through the slow moving fluid in the well casing, and to transport the sand through a small diameter conduit to the inlet of the pump.

(10) TORE solid fluidizers are described in U.S. Pat. No. 4,978,251, U.S. Pat. No. 4,952,099, U.S. Pat. No. 4,992,006 and U.S. Pat. No. 5,853,266, all of which are incorporated herein by reference, and are well known by a person skilled in the art. In accordance with an embodiment of the present invention, a TORE is placed below the casing perforations in the bottom of a well.

(11) As shown in FIG. 1, a well 3, is bored down with a casing 4. Production fluid enters the casing 4 through wellbore perforations 5 into a flow balancing transition device 30, into a pump 40, and into a flow splitting device 60. A portion of the production fluids passing through the flow splitting device 60 enter a TORE supply conduit 12 and into the supply duct of a TORE 10, wherein the TORE fluidizes solids in the bottom of a well 3 and passes the fluidized solids through the TORE 10 into the discharge duct 11 and into a flow balancing transition device 30 that receives the sand laden fluid from the TORE 10, mixes it with the well production fluids from the well casing 4 and feeds the combined stream to the inlet of a pump 40. The flow balance transition device is designed such that the well fluids entering the transition device from the casing will pass through a restricted area in order to create a zone of low pressure within the transition device. The difference in pressure between the casing 4 and the transition device 30 will then provide the energy required to lift the heavier sand laden fluid from the TORE discharge through the discharge duct 11 also referred to as a small diameter conduit) and into the transition device. Leaving the transition device 30, fluids enter the production tubing 50 through pump 40. The production tubing, in an embodiment of the invention, may comprise a flow splitting device 60, just after the discharge of the downhole pump. The flow splitting device 60 diverts a portion of the fluids discharged from the pump 40 into the conduit that is connected to the supply duct 12 of the TORE 10. The flow splitting device 60 includes a restriction that will reduce the pressure from the discharge of the pump and control the flow to the supply duct of the TORE.

(12) The invention described is sufficient to remove sand from the bottom of the well during normal operation of the pump. In the above embodiment of the invention, the TORE is stationary (can be for example in the stator assembly of the pump). In this configuration the external capillary tube for the TORE feed may become damaged/blocked during installation or operation. An additional aspect of the invention is included to be able to recover operation of the pump in the event of a shut-down in which a large amount of sand enters the well and blocks the inlet to the transition device 30. The flow splitting device 60, will include an opening to the casing. The opening will have a non-return valve (check valve) 65 that only allows fluids to enter the conduit connected to the TORE supply duct. A second non-return valve 66 will be installed between the flow splitting device and the opening to the casing. This arrangement will allow pressurized fluid to be fed to the TORE supply duct either from the discharge of the pump, or from the casing. In the event that the transition device is covered with sand, water or fluid can be fed into the casing of the well from the surface. This water or fluid will pass through the TORE fluidizing the sand in the bottom of the well and discharging the sand laden fluid though the pump and into the tubing. Once the sand blocking the transition device has been removed, the pump can then be restarted so the remaining sand can be removed from the well. The complete system or arrangement enables an operator of the well to clear sand from the bottom of the well without removing the pump and tubing from the well, such as with the use of a surface pump, for example. This will greatly reduce the cost of operating wells that produce significant amounts of sand and that require periodic cleaning with expensive surface equipment.

(13) As shown in FIG. 2, an alternate embodiment of the current invention is herein provided in which the supply duct 12 (referred to as TORE feed) is connected to a point in the pump stator rather than the discharge of the pump.

(14) This embodiment circumvents having to regulate the differential pressure from the pump discharge. With the supply duct connected to a midpoint in the lift pump, for example, a constant feed pressure may be supplied to the TORE regardless of the depth of the well and the discharge pressure of the pump. According to this embodiment, a well 3 includes casing 4, production tubing 50 and sucker rod string 170. Inside the well, a fluid dispersing device, TORE 10 and a pump 40 is placed. The pump situated above TORE 10, includes a pump installation device 200, pump seating assembly 220, no-turn tool section 230 (not shown) and a tag bar assembly 190, TORE inlet coupling/rotor connector 140, TORE inlet tube 12 (supply duct which allows diverting a portion of the flow from the mid-section of the pump at an appropriate pressure for feeding the TORE device), TORE/priming stator 120 and production stator 150, TORE/priming rotor 110, and production rotor 160. Sand-laden production fluid enters the casing 4 through well perforations 5 and is mixed with fluid received from the TORE 10. The fluidized production flow continues upwards through a suction port 240, a space between the TORE/priming rotor 110 and the TORE priming stator 120, through a discharge port 250, and into a TORE inlet chamber 130 which is shown situated in the middle of pump 40. A portion of the fluid is diverted through a TORE inlet tube 12, down to the TORE 10 where it helps fluidize the produced sand as described above. The remaining sand-laden production fluid is lifted by pump 40 and travels upwards through production tubing 50. The agitating flow going down from the TORE inlet chamber 130 to TORE 10 is shown by solid arrows, whereas the fluidized production flow moving upwards in production tubing 50 is shown by broken arrows.

(15) As shown in FIG. 3, an alternate embodiment of the current invention is herein provided in which the supply duct 12 (referred to as TORE feed) is connected to a point in the pump body rather than the discharge of the pump, such as for example through the lower rotor of the pump. In this embodiment, the supply duct 12 (TORE feed) is integral to the priming rotor 110 and the TORE unit can be part of the rotating assembly fitted on the end of the rotor.

(16) This embodiment circumvents having to regulate the differential pressure from the pump discharge. With the supply duct connected to a midpoint in the lift pump, for example, a constant feed pressure may be supplied to the TORE regardless of the depth of the well and the discharge pressure of the pump. According to this embodiment, a well 3 includes casing 4, production tubing 50 and sucker rod string 170. Inside the well, a fluid dispersing device, TORE 10 and a pump 40 is placed. The pump situated above TORE 10, includes a pump installation device 200, pump seating assembly 220, no-turn tool section 230, TORE inlet coupling/rotor connector 140, TORE inlet chamber 130 (which allows diverting a portion of the flow from the mid-section of the pump at an appropriate pressure for feeding the TORE device), TORE/priming rotor 110, TORE/priming stator 120 and production stator 150, production rotor 160. Sand-laden production fluid enters the casing 4 through well perforations 5 and is mixed with fluid received from the TORE 10. The fluidized production flow continues upwards through a suction port 240, a space between the TORE/priming rotor 110 and the TORE priming stator 120, through a discharge port 250, and into a TORE inlet chamber 130 which is shown situated in the middle of pump 40. A portion of the fluid is diverted down to the TORE 10 where it helps fluidize the produced sand as described above. The remaining sand-laden production fluid is lifted by pump 40 and travels upwards through production tubing 50. The agitating flow going down from the TORE inlet chamber 130 to TORE 10 is shown by solid arrows, whereas the fluidized production flow moving upwards in production tubing 50 is shown by broken arrows.