STAGE CEMENTING TOOL AND METHOD

Abstract

A stage cementing tool for wellbore cementing, the stage cementing tool including a side pocket conduit and opening and closing pistons in the conduit. An actuator extends from the closing piston to an inner diameter of the stage cementing tool through a passage in the tool wall. The actuator has a contact surface actuatable from within the inner diameter to cause the closing piston to move into the closing position.

Description

FIELD OF THE INVENTION

The invention relates to wellbore tools and operations including, particularly, apparatus and methods for stage cementing a casing string.

BACKGROUND OF THE INVENTION

In the oil and gas industry, cement is often pumped into the annular area surrounding the casing string, which is between the casing string and the wellbore wall and/or other concentric strings of casing. This cement sets and provides fluid, including pressure, isolation, stopping leakage outside the casing along the wellbore.

This tool is designed for stage cementing which means there is more than one stage of cement pumped while cementing the casing. This is normally done when the formation will not support a long column of cement due to high pressures from hydrostatic density of cement.

Stage cementing tools have a body that can be connected into the casing string. The body is a hollow cylindrical wall with substantially the same diameter as the casing and is open to the casing inner diameter both above and below the tool. A typical stage cementing tool has a first sleeve and a second sleeve encircling the inner diameter or the outer diameter of the body. The first and second sleeves are concentric with the tool cylindrical wall.

The first sleeve covers and closes lateral ports through the tool wall, but can be moved either by pressure or by a plug or by mechanical means, to expose and open the lateral ports. Once opened, then cement is pumped from the inner diameter of the casing/tool, through the lateral ports in the tool. Then the second sleeve can be moved to re-cover the lateral ports. The second sleeve can be moved to close the ports, generally with a plug or a ball that is pumped downhole onto a seat, and pressure is applied to slide the second sleeve closed.

A specific problem in cementing stage tools is particularly present in tools that are built in larger diameters. While larger diameters might be or generally would be considered to be something above 6 or 7 inches in diameter, problems intensify in sizes such as 9⅝, 13⅜, 18 inches, etc.

These problems often relate to difficulty in seal integrity in large diameters. It is typical for the first and second sleeves to have seals that are either stationary or moveable depending on their function. As casing diameter, and therefore stage tool diameter becomes larger, it is more difficult to maintain integrity in those seals, especially at higher pressures. The reasons are multiple, but some problems are:

• • Deflection—there is always some variability in wall thickness in oilfield casing and tubulars, those may lead to irregular deformation so that functions such as ballooning do not occur perfectly radially;
  • Seal interference—as diameters increase, it becomes more difficult to provide exact accuracy on the squeeze on either O-rings or other types of elastomers. Thus, you may get uneven loading of the seal material and that may produce seal failure;
  • Seal placement—proper placement and seal squeeze is difficult in large diameters because of complications in tool assembly such as forces required to push seals into a bore;
  • Accuracy and machining—is difficult with large diameters because large diameter cylinders may tend to flex while being machine or there may be thermal issues during machining which will give you an irregular surface. These are not normally seen in smaller oil field sizes such as 4½ inch and 7 inch but they will be particularly problematic in larger sizes over 7 inches.

SUMMARY

In accordance with a broad aspect of the present invention, there is provided a stage cementing tool for wellbore cementing, the stage cementing tool comprising: a cylindrical body with a cylindrical wall encircling an inner diameter and ends configured for coupling to a casing string; a first lateral port through the cylindrical wall; a second lateral passage through the cylindrical wall adjacent the first lateral port; a conduit extending along an outer surface of the cylindrical wall and including an open end opening to the outer surface, the conduit positioned such that the first lateral port and the second lateral passage open into the conduit; an opening piston in the conduit in a sealing position positioned to seal against fluid flow from the first lateral port to the open end, the opening piston being configured to be movable from the sealing position to an open position permitting fluid flow from the first lateral port to the open end; a closing piston in the conduit, the closing piston being moveable into a closing position to seal against fluid flow out the open end of the conduit; and an actuator extending from the closing piston to the inner diameter through the second lateral passage, the actuator having a contact surface actuatable from within the inner diameter to cause the closing piston to move into the closing position.

In accordance with another broad aspect of the present invention, there is provided a method for cementing an annulus of a wellbore, the method comprising: applying hydraulic pressure to a cementing tool as summarized above that is within the wellbore, the hydraulic pressure moving the opening piston from the sealing position to the open position; pumping cement through the first lateral port and the conduit into the annulus; and applying a force from within the inner diameter against the contact surface of the actuator, thereby causing the closing piston to move into the closing position.

It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:

FIG. 1 is a schematic illustration of a long section through a stage cementing tool body according to the present invention;

FIG. 2 is a schematic illustration of an orthogonal section through the stage cementing tool body of FIG. 1;

FIGS. 3A, 3B and 3C are side sections showing schematically illustrated stage cementing tool in three operational positions: closed (run in), cementing ports open, and fully closed, respectively;

FIG. 4 is a schematic illustration of cementing tool with a side pocket piston in greater detail;

FIG. 5 is an enlarged side elevation of a possible piston assembly with a closing piston and an opening piston. An actuator in the form of a crosslink pin is attached to the closing piston;

FIG. 6A is a landing sleeve for actuation of the actuator cross link pin;

FIG. 6B is a long section view along line I-I of FIG. 6A, showing a possible shear mechanism; and

FIG. 7 is a schematic illustration of another cementing tool with a side pocket piston in greater detail.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles of various aspects of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention in its various aspects. The drawings are not necessarily to scale and in some instances proportions may have been exaggerated in order more clearly to depict certain features. Throughout the drawings, from time to time, the same number is used to reference similar, but not necessarily identical, parts.

A stage cementing tool has been invented. The stage cementing tool is intended for installation in a casing string. It can be opened and cement can be pumped through the stage tool to fill the annulus around the tool and the string. The stage cementing tool also has a closing mechanism to hold cement in the annular area. The stage cementing tool is quite useful in large diameter casing.

While most cementing stage tools contain concentric sleeves that fit within the main, largest diameter cylindrical body of the tool, the present stage cementing tool has an alternate design that has a side exit. Specifically, the tool has a port sealing apparatus that is in a side port, rather than a concentric sleeve in the main body. As such, the port sealing apparatus can have a reduced diameter compared to the diameter of the stage tool body. This can simplify construction, improve pressure reliability, improve seal integrity, and reduce overall cost to manufacture while improving dependability.

The present cementing stage tool is a unique design that is operable even in higher pressures that would typically cause large diameter pipe to deform radially, and lose pressure integrity.

In particular, with reference to the Figures, the stage cementing tool 10 includes a cylindrical body 12, as shown in FIG. 1, with a cylindrical wall 12a encircling an open inner diameter ID and ends 12b, 12c configured for coupling to a casing string.

The tool further includes a side cementing port 14 on a side of the cylindrical body 12. The side cementing port 14 includes:

• • a first lateral port 14a through the cylindrical wall;
  • a second lateral passage 14b through the cylindrical wall adjacent the first lateral port; and
  • a conduit 14c extending along an outer surface 12d of the cylindrical wall and including an open end 14d that opens to the outer surface. The conduit is positioned such that the first lateral port 14a and the second lateral 14b passage open into the conduit, with the first lateral port 14a being closer to the open end 14d than the second lateral passage 14b.

The tool further includes:

• • an opening piston 16 positioned in the conduit 14c. As shown in FIG. 3A, the opening piston is normally in a sealing position in the conduit, wherein piston 16 is positioned to seal against fluid flow from the first lateral port 14a to the open end 14d. The opening piston is configured to be movable from the sealing position (FIG. 3A) to an open position (FIG. 3B) permitting fluid flow from the first lateral port 14a to the open end 14d; and
  • a closing piston 18 acting in the conduit 14c. The closing piston includes a piston body 18a and an actuator 18b. The actuator extends from the piston body, through the second lateral passage 14b into the inner diameter ID of the cylindrical body 12. The closing piston 18 is normally in a non-sealing position in the conduit (FIGS. 3A and 3B), but is moveable by actuation of the actuator. Actuation is effected from within the inner diameter. Actuation causes the closing piston body 18a to move into a closing position (FIG. 3C) to seal against fluid flow between the inside and the outside of the tool, for example out through the open end 14d.

The accuracy of a seal construction is much easier with the two pistons 16, 18, both of which can be much smaller in diameter than the overall inner diameter ID of the cylindrical main body 12. For example, the conduit inner diameter and therefore the diameters of pistons 16, 18 can be from 0.75 inches to as large as 3 inches, depending on the diameters of the stage tool body. That is much smaller than the diameter of the cylindrical main body, which may be greater than 6 inches, for example sizes such as 9⅝, 13⅜ or 18 inches.

The side port 14 is outside of the inner diameter ID of the cylindrical body 12. The side port may be integral with the cylindrical body or may be a structure that is coupled to the outer surface of the cylindrical body. In one embodiment, the tool body 12 can have an eccentric shape in orthogonal section (FIG. 2), where side port 14 protrudes from the side of the tubular wall 12a. Alternatively, if outer diameters and wall thickness allow, the side port can be incorporated into a cylindrical tool structure.

As noted, the side port conduit structure can be installed on an outer surface of a casing tubular. For example, in one embodiment, a piece of bar stock can be machined it to an eccentric shape, and then a face can be formed and hollowed out to build the conduit for the side exit piston. That structure can be added to the side of a cylindrical section of tubing. That is a huge cost savings especially in larger sizes and although the machining might be more, the ability to avoid internal connections and concentric seal tubes greatly enhances the efficiency of manufacture as well as the stability of the final assembled tool.

Operations for this tool are unique. While most cementing stage tools have a sleeve that slides to the open position, in this tool a cementing passageway is opened via movement of piston 16 that is in the side port of the tool. To commence a cementing operation, the inner diameter of the tool cylindrical body 12 can be pressured up, which moves that piston 16 to open a pathway through first lateral port 14a, conduit 14c and end 14d. The piston can have a very small diameter compared to the inner diameter of the main body of the tool. Once the conduit of the side port is open between the first lateral port and the open end, circulation can be established and cement as well as spacers and displacement fluid can be pumped down the internal diameter of the casing and out the side exit port (arrows C). This flow is, in particular, through the first lateral port, the conduit and the open end of the conduit, and then up to provide cement isolation between the casing and the drilled hole.

The cylindrical main body of the tool can be built from a single piece of material avoiding connections using the eccentric design. Pull strength of the tool should be greatly enhanced with this construction as the body is robust and stout with a significant cross-section of material and no large diameter connections. Failure points in tension or in compression are typically in conjunction with the connections or with changes in diameter. Most of those are eliminated using this tool.

In one embodiment, the opening piston 16 can be a pump out style closure, moveable by hydraulic pressure. Hydraulic pump out pressures can be achieved by raising the casing pressure, pumping a plug to land and create pressure or opening a closure for the first lateral port 14a to communicate pressure to the piston 16. Hydraulic pressure can force the opening piston out the open end 14d of the conduit 14c. The opening piston can have a selectable pump out pressure and can be built with a variety of seal materials depending on downhole conditions. The pump out pressure can be for example greater than 1500 PSI or for example between about 1750 and 2250 PSI.

The opening piston can be secured with a shear screw into the side of the conduit. The shear screw can be installed from the inner diameter or through the wall of the side pocket. Alternately, or in addition, the opening plug 16 can be connected to the closing plug 18 using a coupling 20 with a known pressure and break force, such as with a shear plane. In such an embodiment, the shear screw is not needed between the opening piston and the conduit.

In such an embodiment, the closing piston 16 and the opening piston 18 are coupled together via coupling 20. The coupling 20 between them is configured to separate, for example fail as by shearing at a shear plane, when sufficient hydraulic pressure is reached to move the opening piston. The coupling can be a structure such as shaft with a known break force. This opening piston to closing piston coupling provides great simplicity as well as accuracy in the opening pressure of the stage tool, as the connection between the pistons can be accurately configured prior to installation of piston 16 in the tool conduit. Thus, a piston assembly of piston 16, coupling 20 and piston 18 can be installed as one pre-configured unit into the side port conduit 14c. In such an embodiment with coupling, only the closing piston 18 need be held in place by simple means such as a shear pin 22 or by connection to a secured structure 28, 32 within the main body. Once the coupling between the opening piston and the closing piston breaks 20′ (FIG. 3B) due to pressure on the opening piston, the opening piston can be expelled to open the first lateral port.

The closing piston 18 is moveable to close communication between the inside of the tool and the outside of the tool, for example, by plugging the conduit of the side port at or near the open end 14d. In one embodiment, the closing piston is installed in a closed end 14e of the conduit, which has no communication with the outer surface. The closed end of the conduit effectively acts as a receptacle for the closing piston. When it is desired to close the side port, the closing piston is moved toward the open end 14d to plug the conduit. In one embodiment, the closing piston moves to a position plugging the open end. For example, the closing piston may block or plug the open end of the conduit. In one embodiment, it seals access from the first lateral port 14a to the conduit 14c. The closing piston may have seals 18c to seal between the first lateral port and the conduit's open end. In one embodiment, there are seals 18c, 18d to seal both above and below the first lateral port. The seals may be for example, o-rings, V-seals for example in a stack or metal.

The closing piston seals against flow from both the first lateral port 14a and from the lateral passage 14b to the open end 14d. The closing piston is lockable in place in its position closing off the open end. For example, the closing piston 18 may include an expandable lock ring 24 configured to lock into a gland 24a in the conduit.

Conduit 14c may have a polished walls to facilitate sealing action of the seals 18c, 18d against the conduit walls. Since some seals may pass the port 14a and passage 14b openings, these openings may be dressed so as not to cut the seals.

Actuator 18b is operable to move the closing piston 18. The actuator extends from the closing piston body 18a into the inner diameter ID through the second lateral passage 14b. Actuation of the actuator from within the inner diameter of the tool causes the moveable closing piston to move to close communication from the inside to the outside of the stage tool. The actuator can be actuatable by various means such as pressure or physical contact.

Actuator 18b is securely coupled to the closing piston body 18a. For example, the two parts may be integral with each other. In one embodiment, the actuator 18b is connected to the closing piston by adhesives or screws such that they are connected. The second lateral passage 14b may be a slot along which the pin can slide to thereby move the closing piston. The actuator may be elongated, such as oval or rectangular, in cross sectional shape to slide more easily along the slot shape of the second lateral passage.

Actuator 18b may be structure with a contact surface 18b′ exposed within the inner diameter and that is actuable by direct pushing drive contact against the contact surface. The contact surface is a structure coupled to the closing piston, for example a part of, integral with, the closing piston or securely attached to the closing piston. As such, movement of the actuator structure moves the closing piston.

In one embodiment, shown in FIG. 4, the actuator 18b is a cross link pin that is coupled to the moveable closing piston 18a. A contact surface 18b′ of the cross link pin is accessible in the inner diameter of the tool by extension from the closing piston through the second lateral passage. The cross link pin is configured such that actuation to move the cross link pin from within the inner diameter of the tool causes the moveable closing piston to move, for example, to close the first lateral port. The cross link pin can be actuatable by various means such as pressure or physical contact

In another embodiment, shown in FIG. 7, the actuator 18b is a portion of the closing piston 18a that extends into the inner diameter. The actuator 18b presents a surface 18b′ in the inner diameter for receiving force thereagainst, thereby for actuation of closing piston 18 to move along the conduit. The contact surface 18b′ is integral with the closing piston 18. The actuator is an end of the overall piston that is angled to extend through the second lateral passage 14b to be accessible in the inner diameter ID of the tool. Force applied against the contact surface from within the inner diameter of the tool causes the moveable closing piston to move towards a closed position relative to conduit open end. Force can be applied against the contact surface by various means such as pressure or physical contact. In this tool, the side exit conduit 14c is machined at an angle relative to the long axis through body 12. Thus, force applied against contact surface 18b′ is generally in line, directly into the width, thickness of the piston main body 18a, along the path of sliding movement of the piston 18. As such, there is less tendency for the piston 18 to tilt off its long axis during actuation.

In one embodiment, the actuator is actuated to slide along passage and thereby to move closing piston 18 by contacting the contact surface directly or indirectly by a structure moved through the inner diameter of the cementing tool. For example, a shifting sleeve 28 may be installed in the tool inner diameter that is movable down (arrow D) to apply a force against the contact surface of the actuator. There may be an interference fit between the shifting sleeve and the actuator. For example, as shown in FIG. 7, there may be a projection or a ledge 28a on the shifting sleeve that catches and bears against the contact surface, for example the end of the piston or the cross link pin, that define the contact surfaces 18b′.

The shifting sleeve 28 may, for example, be moved by a plug 30, such as a ball or pumpable plug such as a wiper plug. The plug can be moved through the casing at the conclusion of cementing and can be configured to land in the sleeve. As shown in FIG. 3C, when the plug 30 lands in the sleeve 28, the sleeve is moved down and this movement moves the cross link pin and causes the closing piston 18a to move to close the port 14a and passage 14b, by plugging conduit 14c at open end 14d.

The shifting sleeve 28 may include a unique support system. For example, as shown in FIGS. 6A and 6B, the shifting sleeve may incorporate a shear ring 32. The shear ring may include a protrusion 32a around its outer diameter, that is placed into a groove in the ID of body 12. As the plug 30 lands and pressure is applied, there is a great amount of force that must be supported. That is done through of the strength of shear ring 32 and also will provide accuracy in the closing force. Once the sleeve slides down it is supported by a shoulder 12e in the ID of body 12.

The shear ring 32 may be secured onto the lower annular end of the sliding sleeve 28, for example via fasteners 32b and/or adhesives. Fasteners can be shear type fasteners to allow the ring to release from its locking groove when a certain force is applied. The ring may be a c-ring or split and it may be constructed of brass, for example. There may be a notch into which the actuator 18b resides, engages or is secured.

Shear ring 32 can eliminate any need for shear pin 22, where piston actuator 18b is retained to move with sleeve 28 and the sleeve is held in place by shear ring 32.

While the shifting sleeve may require a simple seal to hold sufficient pressure to move the sleeve, the seal may be simple as it need not hold significant or sustained pressures. The cementing side port 14 is not sealed off by the sleeve 28 but rather by the closing piston 18.

The sleeve 28 may have a dome shaped landing seat, as shown in FIG. 4, for receiving a cementing plug.

At least the sleeve 28, its wiper plug 30 and the cross link pin 18b may be drillable to open the ID of the tool after cementing. Possibly the shoulder 12e, may be drillable. Regardless, the drilling process does not affect the closing piston 18, as it remains in the closed position in the side port 14. The tying of actuator 18b into sleeve 28 (FIG. 6A) may provide a torque lock and facilitate drill out. In one embodiment, as shown in FIG. 5, the sleeve can have a faceted, such as toothed lower end to engage against a shaped shoulder 12e, so that the sleeve cannot rotate during the drilling process.

The pistons seal within the conduit of the side port. Because the seals 16a, 18c, 18d on the pistons are only¾ to 3 inches in diameter, they typically have good dependability under wellbore pressures and temperatures. Seals can be V seal type stack, O-rings, or a Chevron type of seal stack such as Aflas Teflon Ryton™.

The machining accuracy of the side port components is more reliable due to their small diameters over the larger diameters of the tool body.

If required, critical components can be coated with erosion resistant materials such as nitrate hardening or carbide. For example, the first lateral port 14a and conduit 14c may be coated with the erosion resistant materials. Passage 14b may also be coated with erosion resistant materials, if desired.

It is to be noted that while the pump out opening piston 16 and closing piston 18 are illustrated as cylindrical, they may be shaped with a non-cylindrical geometry, provided they can slide within conduit 14c of the side pocket.

In certain cases, it may be desirable to have multiple side ports and therefore multiple pump out opening plugs. For example, if erosion is a concern or there is an issue with flow, the use of more than one side port may increase the flow area through the stage tool. If multiple side pockets are used, it may be advantageous to tie the multiple hydraulic opening pistons together so that they will be expended at the same time, either with a linkage mechanism or by building them in a single piece.

Although this tool is described as solving problems specific to large diameter stage tool operations, the design also may be advantageous in smaller diameters. Thus, the invention is also useful for smaller diameter tools.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or “step for”.

Claims

1. A stage cementing tool for wellbore cementing, the stage cementing tool comprising: a cylindrical body with a cylindrical wall encircling an inner diameter and ends configured for coupling to a casing string;a first lateral port through the cylindrical wall;a second lateral passage through the cylindrical wall adjacent the first lateral port;a conduit extending outside the inner diameter of the cylindrical wall and including an open end opening to the outer surface, the conduit positioned such that the first lateral port and the second lateral passage open into the conduit;an opening piston in the conduit in a sealing position positioned to seal against fluid flow from the first lateral port to the open end, the opening piston being configured to be movable from the sealing position to an open position permitting fluid flow from the first lateral port to the open end;a closing piston in the conduit, the closing piston being moveable into a closing position to seal against fluid flow out the open end of the conduit; andan actuator extending from the closing piston to the inner diameter through the second lateral passage, the actuator having a contact surface actuatable from within the inner diameter to cause the closing piston to move into the closing position.

2. The stage cementing tool of claim 1, further comprising a sliding sleeve in the inner diameter configured to apply force to the contact surface of the actuator when the sliding sleeve is moved.

3. The stage cementing tool of claim 2 wherein the actuator is engaged with the sliding sleeve to restrict rotation of the sliding sleeve within the inner diameter.

4. The stage cementing tool of claim 2 further comprising a shearable connection between the sliding sleeve and the cylindrical body and the actuator is engaged for movement with the sliding sleeve.

5. The stage cementing tool of claim 1 wherein the closing piston moves along a path and the actuator extends laterally relative to the path.

6. The stage cementing tool of claim 1 wherein the closing piston moves along a path that is at an angle relative to a long axis of the inner diameter and the actuator is at an end of the closing piston.

7. The stage cementing tool of claim 1, wherein the opening piston is moveable by hydraulic pressure from the sealing position to an open position and in the open position, the opening piston is expelled out of the conduit.

8. The stage cementing tool of claim 7, further comprising a coupling connecting the opening piston to the closing piston and wherein the coupling has a selected break force, and the opening piston is moveable when the hydraulic pressure exceeds the break force and decouples the opening piston from the closing piston.

9. The stage cementing tool of claim 1, wherein the conduit includes an erosion resistant coating.

10. A method for cementing an annulus of a wellbore, the method comprising: applying hydraulic pressure to a cementing tool according to claim 1 that is within the wellbore, the hydraulic pressure moving the opening piston from the sealing position to the open position;pumping cement through the first lateral port and the conduit into the annulus; andapplying a force from within the inner diameter against the contact surface of the actuator, thereby causing the closing piston to move into the closing position.

11. The method of claim 10 wherein applying the force includes launching a plug to move into the inner diameter and apply force directly or indirectly against the contact surface.

12. The method of claim 11 further comprising landing the plug in a shiftable sleeve in the inner diameter, shifting the shiftable sleeve to move the shiftable sleeve against the contact surface.

13. The method of claim 12 further comprising drilling out the shiftable sleeve, while rotation of the shiftable sleeve is prevented by engagement with the actuator.