CA3090126C - Method and apparatus for producing hydrocarbons - Google Patents

Abstract

A method and apparatus for producing hydrocarbons from a well that has a production string positioned within a casing string. A progressive cavity pump is provided that has a rotor, a stator, an inlet in fluid communication with the hydrocarbon producing formation, and an outlet in fluid communication with the production string. The well is stimulated by reciprocating the stator of the progressive cavity pump along the rotor and relative to the casing string while operating the progressive cavity pump, stimulating the well.

Description

METHOD AND APPARATUS FOR PRODUCING HYDROCARBONS
TECHNICAL FIELD
[0001] This relates to production of hydrocarbons from a well, in particular using a reciprocating string to stimulate production from the well.
BACKGROUND

[0002] Hydrocarbon wells can be stimulated to improve the efficiency of hydrocarbon production. U.S. Patent No. 3,520,362 entitled "Well Stimulation Method"
describes a method of stimulating a well using acoustic vibrations.
SUMMARY

[0003] According to an aspect, there is provided a method of producing hydrocarbons from a well that has a production string positioned within a casing string. The method may comprise the steps of: providing a progressive cavity pump having a rotor, a stator, an inlet in fluid communication with the hydrocarbon producing formation, and an outlet in fluid communication with the production string; and while operating the progressive cavity pump, stimulating the well by reciprocating the stator of the progressive cavity pump and relative to the casing string.

[0004] According to other aspects, the method may include one or more of the following features, alone or in combination: the rotor may be axially fixed relative to the casing string such that the stator is reciprocated along the rotor; the stator may be rotationally fixed; the rotor may reciprocate with the stator; one or more agitators may be provided that move with the stator, the agitators extending toward the casing string relative to the stator;
stimulating the well may comprise generating pressure fluctuations in the hydrocarbon producing formation or turbulence in the casing string; the rotor of the progressive cavity pump may be at least 36 inches longer than the stator of the progressive cavity pump; when the stator is in a raised position relative to Date Recue/Date Received 2020-08-14 the rotor, the rotor of the progressive cavity pump may extend past a bottom end of the rotor; the stator may be reciprocated by a hydraulic actuator attached to the production string; the stator of the progressive cavity pump may be attached to the production string; and reciprocating the stator may comprise reciprocating the production string.

[0005] According to an aspect, there is provided an apparatus for producing hydrocarbons from a well that has a casing string. The apparatus may comprise a production string adapted to be inserted into the casing string, and a progressive cavity pump carried by the production string.
The progressive cavity pump comprises a rotor, a stator, an inlet adapted to be in fluid communication with a hydrocarbon producing formation, and an outlet in fluid communication with the production string. One or more agitators are in a fixed position relative to the stator, the one or more agitators extending radially outward relative to the stator. An actuator is provided that is adapted to axially reciprocate the stator relative to the casing string while the progressive cavity pump is operating.

[0006] According to other aspects, the apparatus may comprise one or more of the following features, alone or in combination: the rotor may be axially fixed relative to the casing string such that the stator is reciprocated along the rotor; the stator may be rotationally fixed relative to the casing string; the rotor may reciprocate with the stator; the rotor of the progressive cavity pump may be at least 36 inches longer than the stator of the progressive cavity pump; the actuator may be at or above a wellhead of the well; the actuator may be a hydraulic actuator; the one or more agitators may be carried by the stator of the progressive cavity or the production string; the one or more agitators may comprise annular cups having a diameter sufficient to at least partially engage an inner surface of the casing string; and there may be a drive rod that connects to the rotor of the progressive cavity pump from a drive head at surface.

[0007] In other aspects, the features described above may be combined together in any reasonable combination as will be recognized by those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
Date Recue/Date Received 2020-08-14

[0008] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:
FIG. 1 is an elevated side view in cross section of an apparatus for producing hydrocarbons.
FIG. 2 is an elevated side view in cross section of a well head of an apparatus for producing hydrocarbons in a raised position.
FIG. 3 is an elevated side view in cross section of a well head of an apparatus for producing hydrocarbons in a lowered position.
FIG. 4 is an elevated side view in cross section of a downhole portion of an apparatus for producing hydrocarbons with the stator in a raised position.
FIG. 5 is an elevated side view in cross section of a downhole portion of an apparatus for producing hydrocarbons with the stator in a lowered position.
FIG. 6 is an elevated side view in cross section of a downhole portion of an apparatus for producing hydrocarbons with the stator and rotor in a raised position.
FIG. 7 is an elevated side view in cross section of a downhole portion of an apparatus for producing hydrocarbons with the stator and rotor in a lowered position.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0009] An apparatus for producing hydrocarbons, generally identified by reference numeral

10, will now be described with reference to FIG. 1 through 5.
[0010] Referring to FIG. 1, apparatus 10 is used to produce hydrocarbons from a well 12 that has a casing string 14 that forms the outer edge of well 12 and that has been drilled into a hydrocarbon producing formation 100.

[0011] Referring to FIG. 1, apparatus 10 has a production string 16 that is adapted to be inserted into casing string 14. Production string 16 may be inserted such that it extends into Date Recue/Date Received 2020-08-14 hydrocarbon formation 100. A progressive cavity pump 20 is carried by production string 16 and adapted to be inserted into well 12. Progressive cavity pump 20 has a rotor 22, a stator 24, an inlet 26, and an outlet 28. Inlet 26 is in fluid communication with hydrocarbon producing formation 100 and outlet 28 is in fluid communication with production string 16. Stator 24 may be fixed to production string 16 using one or more connectors 25, as shown, or stator 24 and production string 16 may be attached together using other methods well known in the art. Rotor 22 may be driven by a drive rod 30 that extends between a drive head 44 at surface to rotor 22, such as through production tubing 16 as shown. In one example, stator 24 may be 10 ¨ 30 feet long and rotor 22 may be at least 36 inches longer than stator 24; other progressive cavity pump 20 dimensions may also be used.

[0012] Referring to FIG. 4 and FIG. 5, stator 24 is adapted to reciprocate along the length of rotor 22 while rotor 22 is rotated, where stator 24 moves relative to casing string 14. Stator 24 is preferably rotationally fixed relative to casing string 14, and rotor 22 is preferably axially fixed relative to casing string 14 as allowing movement of rotor 22 would require additional equipment. A bottom portion 13 of casing string 14 is open to allow hydrocarbons to enter well 12 as is known in the art. Progressive cavity pump 20 is in communication with fluid that enters well 12 via bottom portion 13.

[0013] Apparatus 10 has one or more agitators 32 that extend radially outward relative to stator 24 and are fixed relative to stator 24. Agitators 32 may be carried by one or both of production string 16 and stator 24, or to a joint or tool installed between production string 16 and stator 24. In one example, shown in FIG. 4 and FIG. 5, agitators 32 may be annular cups that have a sufficient diameter to engage an inner surface of casing 14. The degree to which cups 32 engage with casing 14 may be adjusted, and may be designed to be "leaky".
Agitators 32 may take other forms, such as fins, flanges, etc., that may be designed to accomplish different effects downhole, depending on the characteristics of the well 12 and the type of well stimulation desired. For example, agitators 32 may be used to generate pressure fluctuations between well 12 and downhole formation 100, or may be used to create turbulence in the wellbore fluids within casing 14.
Date Recue/Date Received 2020-08-14

[0014] Referring to FIG. 2 and FIG. 3, apparatus 10 has an actuator 40 that axially reciprocates stator 24 relative to rotor 22. Reciprocating stator 24 while rotor 22 is rotating may be used to generate turbulence within casing string 14. As shown, actuator 40 is connected to production string 16, and reciprocates production string 16 and stator 24 together. As shown, actuator 40 is attached above a well head 42 of well 12, however it will be understood that actuator may be located in other positions, such as partially or fully in well 14, or underground.
A drive head 44 for driving drive rod 30 may be connected above actuator 40.
Other components may also be attached at well head 42 that are not shown, such as a blow-out preventer, ports for flow lines, or other equipment known in the art. Actuator 40 as depicted in FIG. 2 and FIG. 3 is one example of actuator 40; other variations may be possible, such as other types of hydraulic or mechanical actuators.

[0015] In the depicted example, actuator 40 may include a barrel 46, a piston 48 within barrel 46, and a cylinder ram 50 connected to piston 48 that extends out of barrel 46 and is connected to production string 16. Piston 48 may slide along a stationary tube 47 within barrel 46. Ram 50 may be connected to production string 16 by connectors 25.
Hydraulic power may be provided through hydraulic ports 52 in barrel 46. As shown, a pipe 54 with seals 56 may be hung from well head 42 to isolate the top of production string 16 from gas within casing string 14. One or more additional seals 56 may be used to seal barrel 46, piston 48, production string

16, casing string 14, or other chambers not shown.
[0016] Referring to FIG. 6 and FIG. 7, in another example, actuator 40 may reciprocate stator 24 and rotor 22 together relative to casing string 14 as progressive cavity pump 20 continues to operate. This may be contrasted to the example shown in FIG. 4 and FIG. 5, where stator 24 reciprocates relative to rotor 22 and casing string 14. In this manner, stator and 24 and rotor 22 may be reciprocated to stimulate formation 100 while they are in the same axial position relative to each other. Stator 24 and rotor 22 may be reciprocated together by mounting drive head 44 to actuator 40, such that drive rod 30 and production string 16 are reciprocated together.
In this case, rotor 22 would not have to be substantially longer than stator 24 as in FIG. 4 and FIG. 5, but could be a similar size typical of progressive cavity pumps. As with typical Date Recue/Date Received 2020-08-14 progressive cavity pumps, rotor 22 extends past the end of stator 24 although variations may be possible.

[0017] An example of a method of producing hydrocarbons from well 12 using apparatus 10 will now be described with reference to FIG. 2 to FIG. 7.

[0018] Apparatus 10 as described above is provided, and progressive cavity pump 20 is operated to produce fluid from hydrocarbon producing formation 100. Fluid enters inlet 26 of pump 20 and exits outlet 28 where it travels to well head 42 through production string 16.
Progressive cavity pump 20 may be operated by driving rotor 22 with drive head 44 via drive rod 30. While progressive cavity pump 20 is being operated, stator 24 is reciprocated relative to rotor 22 to stimulate well 12.

[0019] Stator 24 may be reciprocated by actuator 40 and may be rotationally fixed while it is being reciprocated. Rotor 22 may be axially fixed. Stator 24 is reciprocated between a raised position, such as shown in FIG. 4, and a lowered position, such as shown in FIG. 5. The corresponding raised and lower positions for actuator 40 is shown in FIG. 2 and FIG. 3, respectively. If actuator 40 is connected to stator 24 via production string 16, production string 16 may be reciprocated as well. Stator 24 may be reciprocated such that at least a portion of rotor 22 remains extends out of inlet 26.

[0020] In the example shown in FIG. 6 and 7, stator 24 and rotor 22 are reciprocated together between the raised position, as shown in FIG. 6, and the lowered position, as shown in FIG. 7. This may be accomplished by mounting stator 24 via production string 16 and rotor 22 via drive rod 30 to actuator 40.

[0021] In many situations, stator 24 may be reciprocated continuously, or sufficiently continuous to stimulate well 12. This may include controlling variables of the reciprocation pattern such as changes in speed or rest periods to achieve an acceptable level of efficiency of fluid production. Reciprocation may also be at a constant frequency for extended periods of time.
For example, stator 24 may be reciprocated constantly outside of start up or shut down Date Recue/Date Received 2020-08-14 procedures.

[0022]
Stimulation of well 12 is done to improve the ability of apparatus 10 to produce fluids from hydrocarbon formation 100, such as increasing fluid flow into well 12, keeping solids suspended in fluid flowing through progressive cavity pump 20. Stimulation may include inducing turbulence in fluid within well 12, such as with agitators 32 attached to stator 24 or production string 16. Rotor 22 may also contribute to stimulation of well 12 when rotor extends out of stator 24, such as when stator 24 is in the raised position relative to rotor 22 depicted in FIG. 4. Stimulation may include generating pressure fluctuations within hydrocarbon producing formation 100, such as by using agitators 32 that are annular cups extending between stator 24 or production string 16 and casing string 14. Stimulation of well 12 is done to improve the ability of apparatus 10 to produce fluids from hydrocarbon formation 100, such as increasing fluid flow into well 12, or keeping solids suspended in the fluid.

[0023]
In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not .. excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.

[0024]
The scope of the following claims should not be limited by the preferred embodiments set forth in the examples above and in the drawings, but should be given the broadest .. interpretation consistent with the description as a whole.
Date Recue/Date Received 2020-08-14

Claims (20)

What is Claimed is:

1. A method of producing hydrocarbons from a hydrocarbon producing formation, the well having a production string positioned within a casing string, the method comprising the steps of:
providing a progressive cavity pump having a rotor, a stator, an inlet in fluid communication with the hydrocarbon producing formation, and an outlet in fluid communication with the production string; and while operating the progressive cavity pump, stimulating the hydrocarbon producing formation by reciprocating the stator of the progressive cavity pump relative to the casing string.

2. The method of claim 1, wherein the rotor is axially fixed relative to the casing string such that the stator is reciprocated along the rotor.

3. The method of claim 1, wherein the stator is rotationally fixed.

4. The method of claim 1, wherein the rotor reciprocates with the stator.

5. The method of claim 1, further comprising the step of providing one or more agitators that move with the stator, the agitators extending toward the casing string relative to the stator.

6. The method of claim 1, wherein stimulating the hydrocarbon producing formation comprises generating pressure fluctuations in the hydrocarbon producing formation or turbulence in the casing string.

7. The method of claim 1, wherein the rotor of the progressive cavity pump is at least 36 inches longer than the stator of the progressive cavity pump.

8. The method of claim 7, wherein, when the stator is in a raised position relative to the rotor, the rotor of the progressive cavity pump extends past a bottom end of the rotor.
Date Recue/Date Received 2020-08-14

9. The method of claim 1, wherein the stator is reciprocated by a hydraulic actuator attached to the production string.

10. The method of claim 1, wherein the stator of the progressive cavity pump is attached to the production string, and the step of reciprocating the stator comprising reciprocating the production string.

11. An apparatus for producing hydrocarbons from a well, the well having a casing string, the apparatus comprising:
a production string adapted to be inserted into the casing string;
a progressive cavity pump carried by the production string, the progressive cavity pump comprising a rotor, a stator, an inlet adapted to be in fluid communication with a hydrocarbon producing formation, and an outlet in fluid communication with the production string;
one or more agitators in a fixed position relative to the stator, the one or more agitators extending radially outward relative to the stator; and an actuator that is adapted to axially reciprocate the stator relative to the casing string while the progressive cavity pump is operating.

12. The apparatus of claim 11, wherein the rotor is axially fixed relative to the casing string such that the stator is reciprocated along the rotor.

13. The apparatus of claim 11, wherein the stator is rotationally fixed relative to the casing string.

14. The apparatus of claim 11, wherein the rotor reciprocates with the stator.

15. The apparatus of claim 11, wherein the rotor of the progressive cavity pump is at least 36 inches longer than the stator of the progressive cavity pump.

16. The apparatus of claim 11, wherein the actuator is at or above a wellhead of the well.
Date Recue/Date Received 2020-08-14

17. The apparatus of claim 11, wherein the actuator is a hydraulic actuator.

18. The apparatus of claim 11, wherein the one or more agitators are carried by the stator of the progressive cavity pump or the production string.

19. The apparatus of claim 11, wherein the one or more agitators comprise annular cups having a diameter sufficient to at least partially engage an inner surface of the casing string.

20. The apparatus of claim 11, further comprising a drive rod that connects to the rotor of the progressive cavity pump from a drive head at surface.
Date Recue/Date Received 2020-08-14