WATERFLOOD COMPLETION SYSTEM AND ASSEMBLY

Abstract

A waterflood completion system usable in a well includes a mandrel disposed on a tubing string deployable down a borehole. The mandrel has a side pocket with one or more ports for communicating the tubing string with an annulus of the borehole A waterflood regulator arrangement is connected to the mandrel and has at least one screen directly included therein spaced from the mandrel and lying adjacent the tubing string.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application relates to and claims priority from U.S. Provisional Application Ser. No. 61/253,983, filed Oct. 22, 2009, which is fully incorporated herein by reference.

FIELD

The present disclosure generally relates to downhole oilwell technology, and more particularly, pertains to waterflood side pocket mandrel installations, such as used in injector wells.

BACKGROUND

Only a portion of oil can be recovered from a permeable oil-bearing subterranean formation as a result of the natural pressure of the reservoir. So called secondary recovery techniques are thus used to force the oil out of the reservoir. The simplest method of expelling oil of the reservoir formation is by direct replacement with another fluid, typically water or gas.

Waterflooding is one of the most successful and extensively used secondary recovery methods. As depicted in FIG. 1, water is injected under pressure into the reservoir R via an injector well IW driving the oil through the reservoir into a production well PW. In this manner, wells that have finished primary production can continue to produce oil thereby extending the economic life of the well field, and increasing the total recovered oil from the reservoir.

In a typical waterflood completion system, the injector well has a casing that passes through the reservoir. A tubing string positioned in the casing is provided with a number of side pocket mandrels which are typically located between packers. Surrounding the tubing string, these packers separate the annulus (the space between the tubing string and the casing) into multiple isolated zones in communication with the reservoir that can be separately treated. Particular to the waterflood application, each side pocket mandrel is installed with a waterflood regulating device that enables precision subsurface control. Water injected through the tubing string enters a waterflood regulator valve, passes through an orifice and exits through a port into a zone to be flooded.

Waterflood applications provide a metered flow rate of water into the reservoir. The injected water aids in maintaining the injector well static bottomhole pressure, and washes the oil production through the formation from the injector well to the production well significantly increasing a recoverable reserve of the reservoir. The design of the side pocket mandrel allows for retrieval and placement of flow control devices by the use of wireline, slickline and other deployment methods that will allow for changing the flow characteristics of the waterflood regulator valve and matching the required injection rates to optimize production of the reservoir. Using packers to isolate separate zones in a single injector well, the waterflood completion system is designed so that each zone receives the appropriate rates of injected water.

Known waterflood side pocket mandrels are similar in that they are part of the tubing string that utilizes a snorkel or flow tube to inject the water at a regular rate from the tubing string into the annulus. The snorkel is currently designed as a short length of pipe that connects from an outlet on the mandrel using a threaded connection to a standard separate check valve which prevents backflow from the reservoir. Water controlled and delivered at the surface of the well exits from the regulator valve into the annulus, passes through perforations in the casing and interacts with the surrounding reservoir. In some cases, sandscreens are located at the injector zones and are controlled separately from the tubing string in an attempt to prevent introduction of backflow particulates from the reservoir into the side pocket mandrel. In other designs, sliding sleeves are required to control injection rates into the individual zones to provide a continuous injection rate. In the past, it has been customary to utilize more than one tubing string to effect the desired secondary oil recovery.

SUMMARY

The present inventors have found that the prior art waterflood completion systems as described above have number of drawbacks which can limit the efficiency of secondary oil recovery. Accordingly, the present disclosure provides solutions which improve upon waterflood regulator arrangements installed in side pocket mandrels by adapting the mandrels directly to the sandscreens, integrating the check valve into the regulator arrangement and eliminating the slickline operations for adjustment to the regulator valve and the requirement for sliding sleeves in the tubing string. The present disclosure further contemplates compensating for variations in the particular mandrel and regulator arrangement, easing installation cost and complexity and removing the need for surface control of the water flow.

In one example, a waterflood completion system usable in a well includes a mandrel disposed on a tubing string deployable down a borehole. The mandrel has a side pocket with one or more ports for communicating the tubing string with an annulus of the borehole. A waterflood regulator arrangement is connected to the mandrel and has at least one screen directly included therein spaced from the mandrel and lying adjacent the tubing string.

The regulator arrangement defines at least one flow path for regulating flow of fluid into the mandrel through the regulator arrangement and out of the screen into the annulus. The regulator arrangement typically includes a regulator valve installed in the side pocket, a flow tube connected to the mandrel and a support structure operatively connected between the flow tube and the tubing string for supporting the screen. The support structure includes an adapter connected to the flow tube, and a shroud attached to the tubing string and supporting the screen. The screen is positioned between the adapter and the shroud. The support structure includes a connector joined to the screen and retained by the shroud. A check valve is incorporated within the flow tube, and the flow tube is made adjustable in length. The present disclosure also contemplates the regulator arrangement defining a first flow path for delivering fluid to a first screen located beneath the mandrel, and a second flow path for delivering fluid to a second screen located above the mandrel.

In another example, a waterflood regulator arrangement usable in a well casing and adapted to regulate fluid flow between a tubing string and an annulus of a borehole includes a regulator valve adapted to be installed in a side pocket mandrel of the tubing string. A flow tube is positioned in communication with the regulator valve and is adapted to be secured to the mandrel. A support structure is operatively connected to at least the flow tube and supports a screen.

In a further example, a waterflood completion system usable in a well includes a mandrel disposed on a tubing string deployable down a borehole, the mandrel having at least one side pocket with one or more ports for communicating the tubing string with an annulus of the borehole. At least one regulator valve is installed in the side pocket of the mandrel for regulating flow between the mandrel and the annulus. At least one adapter is spaced from the mandrel and surrounds the tubing string. At least one flow tube connects the mandrel and the adapter. At least one shroud is attached to the tubing string, and at least one screen is coupled to the shroud. Fluid delivered from the tubing string into the mandrel is regulated by the valve and flows through the flow tube into the adapter and out the screen relative to at least one side of the mandrel for delivery into the annulus.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of a cross section of a reservoir positioned between an injector well and a production well;

FIG. 2 is a schematic diagram of the injector well provided with a waterflood completion system according to the present disclosure;

FIG. 3 is an enlarged fragmentary sectional view of one example of a waterflood regulator arrangement used in FIG. 2;

FIG. 4 is an enlarged detail view of a flow tube of the waterflood regulator arrangement shown in a retracted position;

FIG. 5 is a view similar to FIG. 4 showing the flow tube in an extended position;

FIG. 6 is an enlarged detail view of an adapter, a shroud and a screen of the waterflood regulator arrangement taken on line 6-6 of FIG. 3; and

FIGS. 7 and 8 are fragmentary sectional views of another example of a waterflood regulator arrangement.

DETAILED DESCRIPTION

In the following description, certain terms have been used for brevity, clearance and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different configurations and methods described herein may be used alone or in combination with other configurations, systems and methods. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims.

Referring now to the drawings, FIG. 2 illustrates a waterflood completion system 10 for an injector well 12 used in secondary oil recovery and having a casing 14 that passes through a reservoir formation 16 containing residual oil. A tubing string 18 positioned inside the casing 14 is provided with a series of spaced apart side pocket mandrels 20 which are located between packers 22. Each mandrel 20 is in communication with the tubing string 18 and an annulus 24 extending between the tubing string 18 and the casing 14. The packers 22 surround the tubing string 18 and separate the annulus 24 into multiple isolated zones that can be separately treated. Installed in each mandrel 20 is a waterflood regulator arrangement 26 which functions to regulate fluid (e.g. water or the like), such as delivered into the tubing string 18 by a pump at the surface of well 12, between the tubing string 18 and the annulus 24. Once in the annulus 24, fluid can then pass through perforations 28 formed in the casing 14 at each zone, and interact with the surrounding formation 16 to forcibly sweep residual oil therefrom into an adjacent production well.

FIGS. 3-6 show one example of waterflood regulator arrangement 26 comprised of a waterflood regulator valve 30, an elongated, adjustable flow tube or snorkel 32, a tubular adapter 34 and tubular shroud 36 with a surrounding cylindrical sandscreen 38. Each waterflood regulator arrangement 26 used in the completion system 10 is designed to operate independently of one another, and separately controls the volume of fluid that can enter the isolated zone adjacent the formation 16 to be treated. In this way, each of the waterflood regulator arrangements 26 can compensate for differential pressure changes and provide a constant volume of fluid for each zone.

As seen in FIG. 3, the tubing string 18 has an inner wall 40 with a constant diameter that defines a flow passageway for transporting fluid to each mandrel 20 and waterflood regulator arrangement 26 installed relative thereto. The inner wall 40 is formed with inlet ports 42 which are in communication with inlets on the waterflood regulator valve 30 installed directly within the mandrel 20. As is known, water injected into the tubing string 18 via inlet ports 42 typically enters a filter in the regulator valve 30, passes through a fixed orifice in a stem and flows from an outlet aligned with an exit port 44 formed in the mandrel 20. If the differential pressure through the regulator valve 30 increases or decreases, the position of the stem changes. This regulates fluid flow through the outlet of the valve 30 while maintaining a constant flow rate independent of pressure variations.

With further reference to FIGS. 4 and 5, the flow tube or snorkel 32 has a flow path defined by a central passageway 46 in communication with a flow chamber 48, an annular passageway 50 and an outlet 52. A portion of the central passageway 46 is formed in an inner member 54 which is threadably adjustable relative to an outer sleeve 56. The outer sleeve 56 is fixed to an intermediate section 58 that is joined to a check valve housing assembly 60 that is provided with a check valve 62 for normally preventing backflow from the annulus 24 into the mandrel 20. The check valve 62 has a valve member 64 normally biased by a spring 66 against a valve seat 68 formed on the intermediate section 58. Knurled rings 70, 72 and 74 are provided to facilitate selective adjustment of the inner member 54 relative to the outer sleeve 56, intermediate section 58 and check valve housing 60 so that the snorkel 32 may be varied in length (e.g. ±0.5 inches) to compensate for variations in manufacturing the remaining elements of the mandrel 20 and the regulator arrangement 26. A locking ring 76 is provided on the outer sleeve 56 to enable locking the snorkel 32 in either a retracted position shown in FIG. 4 or an extended position shown in FIG. 5. The snorkel 32 is connected to the mandrel 20 by means of an end 78 of the inner member 54 which is threadably secured in the mandrel outlet port 44. As seen best in FIG. 3, the snorkel 32 extends externally of the mandrel 20 along an outer surface of the tubing string 18.

Referring to FIG. 6, the adapter 34 surrounds the tubing string 18 and is connected to the snorkel 32 by means of an end 80 of the check valve housing 60 which is threadably received in an inlet 82 on the adapter 34. Outlet 52 of the snorkel 32 is in communication with an annular chamber 84 formed in the adapter 34. Inner portions 86 of the adapter 34 are in sealed relationship with the external surface of the tubing string 18. The outer diameter of the adapter 34 is substantially equal to the outer diameter of the mandrel 20.

The shroud 36 is a non-perforated, solid tube having an end 88 which is threadably coupled at 90 to a lower end 92 of the tubing string 18. The shroud 36 defines a channel 94 for retaining a connector 96 that is attached to the perforated sandscreen 38 by a number of torque bolts 98. A sandscreen 38 has one solid portion 100 which extends between the adapter 34 and shroud 36, and another solid portion 102 which runs between the external surface of the tubing string 18 and a sealing surface 104 on the adapter 34. A number of set screws 106 on the adapter 34 helps maintain the desired spacing of the sandscreen 38. The inner diameter of the shroud 36 is substantially equal to the inner diameter of the tubing string 18.

With the waterflood completion of FIG. 2 having the regulator arrangement 26 installed, well operators can proceed with a waterflood operation by injecting fluid (e.g. water or the like) into the tubing string 18. As depicted by the arrows A in FIGS. 3 and 6, the injected fluid passing down the tubing string 18 enters inlet ports 42, the regulator valve 30 and the central passageway 46 of the snorkel 32. When the pressure of the fluid has reached a predetermined value, the valve member 64 opens against the bias of spring 66 and allows the fluid to flow from the flow chamber 48 through the annular passageway 50 and outlet 52 into the adapter chamber 84. The fluid then flows between portion 102 and an external surface of tubing string 18, and between the portion 100 and the shroud end 88 and flows out of a perforated portion 108 of sandscreen 38 into the annulus 24 and through the casing perforations 28 to the formation 16. Thus, it should be appreciated that fluid is injected along a flow path through the snorkel 32, the adapter 34, the shroud 36 and the sandscreen 38 which are all conveniently located beneath the mandrel 20 in a substantially inline arrangement adjacent the tubing string 18.

FIGS. 7 and 8 illustrate another example of a water regulator arrangement 26′ which modifies the waterflood regulator arrangement 26 described above to include a manifold 110 in the adapter 34. The manifold 110 defines a pathway 112 in communication with the chamber 84 in adapter 34. An elongated tubular side pipe 114 in communication with the pathway 112 is connected between the adapter 34 positioned beneath the mandrel 20 and an adapter 34′ positioned above the mandrel 20. An open end of the adapter 34′ is sealed with a plug 116. A shroud 36′ is connected to an upper end 118 of tubing string 18 and carries a sandscreen 38′. In this example, one flow path will enable injection of fluid into the sandscreen 38 as described above, while another flow path defined by the pathway 112 and the side pipe 114 will enable simultaneous injection of fluid into a pathway 120 of adapter 34′ so that fluid is also delivered to the sandscreen 38′ above the mandrel 20.

In a further example, two waterflood regulator arrangements are installed in two side pockets of a mandrel. One flow path will enable injection of fluid into an adapter and a sandscreen beneath the mandrel, while another flow path defined by a feed tube connected between adapters located above and below the mandrel will again enable simultaneous injection of fluid into a sandscreen above the mandrel. This example is similar to, but more efficient than that shown in FIGS. 7 and 8 as the inlet ports of the two regulator valves are independently flooded with fluid.

The present disclosure thus provides a waterflood completion system in which side pocket mandrels may be adapted directly to sandscreens that prevent the backflow of particulates from the formation into the mandrels. The present design has been found to ease installation and reduce cost and complexity of running the completion as only one completion string needs to be installed, instead of two as has been done in the past. In the present completion system, the check valve is integrally designed in the snorkel so that there is no need to externally install the check valve. In multi-zone applications, the check valve operates to prevent reverse flow of fluid back into the tubing string so as to stop any contamination. The present design further eliminates the need for surface control of the flow as the waterflood regulator valves adjust automatically to pressure rate fluctuations and meter the flow along at least one flow path as required. Traditional sliding sleeves used in the tubing string and screens separately run and landed at the injection zones are eliminated, and there is no need for slickline operations to replace or adjust the waterflood regulator valves because the fluid flow is continuously regulated.

Claims

1. A waterflood completion system usable in a well comprising:

a mandrel disposed on a tubing string deployable within a borehole, the mandrel having a side pocket with one or more ports for communicating the tubing string with an annulus of the borehole; and

a waterflood regulator arrangement connected to the mandrel and having at least one screen directly included therein spaced from the mandrel and lying adjacent the tubing string.

2. The system of claim 1, wherein the regulator arrangement defines at least one flow path for regulating flow of fluid into the mandrel through the regulator arrangement and out of the screen into the annulus.

3. The system of claim 1, wherein the regulator arrangement includes:

a regulator valve installed in the side pocket;

a flow tube connected to the mandrel; and

a support structure operatively connected between the flow tube and the tubing string for supporting the screen.

4. The system of claim 3, wherein the support structure includes an adapter connected to the flow tube, and a shroud attached to the tubing string and supporting the screen.

5. The system of claim 4, wherein the screen is positioned between the adapter and the shroud.

6. The system of claim 4, wherein the support structure includes a connector joined to the screen and retained by the shroud.

7. The system of claim 3, wherein a check valve is incorporated within the flow tube.

8. The system of claim 3, wherein the flow tube is adjustable in length.

9. The system of claim 1, wherein the regulator arrangement defines a first flow path for delivering fluid to a first screen located beneath the mandrel, and a second flow path for delivering fluid to a second screen located above the mandrel.

10. A waterflood regulator arrangement usable in a well casing and adapted to regulate fluid flow between a tubing string and an annulus of a borehole, the arrangement comprising:

a regulator valve adapted to be installed in a side pocket mandrel of the tubing string;

a flow tube positioned in communication with the regulator valve and adapted to be secured to the mandrel; and

a support structure operatively connected to at least the flow tube and supporting a screen.

11. The arrangement of claim 10, wherein a check valve is incorporated within the flow tube.

12. The arrangement of claim 10, wherein the flow tube is adjustable in length.

13. The arrangement of claim 10, wherein the support structure includes:

an adapter connected to the flow tube, and a shroud adapted to be joined to the tubing string and directly supporting the screen.

14. A waterflood completion system usable in a well comprising:

a mandrel disposed on a tubing string deployable down a borehole, the mandrel having at least one side pocket with one or more ports for communicating the tubing string with an annulus of the borehole;

at least one regulator valve installed in the side pocket of the mandrel for regulating fluid flow between the mandrel and the annulus;

at least one adapter spaced from the mandrel and surrounding the tubing string;

at least one flow tube connecting the mandrel and the adapter;

at least one shroud attached to the tubing string; and

at least one screen coupled to the shroud,

whereby fluid delivered by the tubing string into the mandrel is regulated by the valve and flows through the flow tube into the adapter and out the screen relative to at least one side of the mandrel for delivery into the annulus.

15. The system of claim 14, wherein the adapter has a flow chamber which is in communication with the flow tube.

16. The system of claim 14, wherein the flow tube has an inner member which is threadably connected relative to the outer sleeve so that the flow tube is adjustable between a retracted position and an extended position.

17. The system of claim 14, wherein an inner diameter of the shroud is equal to an inner diameter to the tubing string.

18. The system of claim 14, wherein the screen is positioned between the adapter and the shroud.

19. The system of claim 14, wherein the screen extends beyond the adapter.

20. The system of claim 14, wherein a portion of the fluid flow to the adapter is delivered to another adapter and flows out of another screen relative to an opposite side of the mandrel.