Patent Grant
7549475
The subject matter of the present application is related to U.S. patent application Ser. No. 11/674,020 filed Feb. 12, 2007 and entitled “Methods for Actuating a Downhole Tool,” which is hereby incorporated herein by reference in its entirety for all purposes.
Not applicable.
Not applicable.
The present invention relates generally to apparatus and methods of releasing mechanical plugs into a well bore. More particularly, the present invention relates to compressible mechanical plugs that may be released into a work string disposed within a well bore to actuate downhole tools, and methods of releasing the mechanical plugs remotely from the work string.
In general, when drilling hydrocarbon wells, a drill bit is disposed at the end of a drill string, and typically, the drill string is rotated from the surface utilizing either a top drive unit or a rotary table set in the drilling rig floor. As drilling progresses, increasingly smaller diameter tubulars comprising casing and/or liner strings may be installed end-to-end to line the borehole wall. As the well is drilled deeper, each string is run through and secured to the lower end of the previous string to line the borehole wall. Finally, the string is cemented into place by flowing cement down the flowbore of the string and up the annulus formed by the string and the borehole wall.
To perform the cementing operation, a cementing manifold is usually disposed between the top drive unit or rotary table and a work string extending into the well. Due to its position, the cementing manifold must suspend the weight of the work string and the casing string, contain pressure, transmit torque, and allow unimpeded rotation of the work string. The cementing manifold is designed to allow fluids, such as drilling mud or cement, to flow therethrough while simultaneously enclosing and protecting from flow one or more darts that are released on demand and in sequence to perform various operations downhole, including wiping pipe surfaces, separating fluids, and actuating downhole tools. Thus, as fluid flows through the cementing manifold, the darts are isolated from the fluid flow until they are ready for release.
Within the borehole, the work string, with one or more cementing plugs disposed at a lower end thereof, extends into and connects to a casing running tool that suspends the casing string to be cemented. Thus, the work string is positioned upstream of the casing string. The work string runs the casing string into the borehole to the desired depth, and the casing string fills with drilling fluid or other fluid in the well as it is being run in. When the casing string is positioned at the desired depth, cement is pumped downhole through the work string. As the cement is pumped, a dart or other device is released from the cementing manifold and propelled down the work string ahead of the batch of cement. The dart lands in a seat in one of the cementing plugs at the lower end of the work string, and the pressure behind the dart causes the cementing plug to be released as the cement pushes the plug down. Thus, the cementing plug is released by the dart ahead of the cement batch. This cementing plug maintains a separation between the cement slurry and the drilling fluid, and thereby reduces contamination of the cement slurry as it flows into the casing string. The cementing plug that precedes the cement slurry and separates it from the drilling fluid is referred to herein as the “bottom cementing plug.” This bottom cementing plug also sealingly engages the inner surface of the casing string to wipe the drilling fluid from the walls of the casing string ahead of the cement slurry. The bottom cementing plug then lands on a float collar or float shoe attached within the bottom end of the casing string.
When the bottom cementing plug lands on the float collar or float shoe attached to the bottom of the casing string, a bypass mechanism in the bottom cementing plug is actuated to allow the cement slurry to proceed through the bottom cementing plug, through the float collar or float shoe and upwardly into the well bore annulus between the casing string and the borehole wall. When the required quantity of cement slurry has been pumped through the work string, a second dart or other device is launched from the cementing manifold to follow the cement batch. This dart is pushed along by a displacement fluid and wipes cement from the walls of the work string, then lands in a releasing sleeve of a second cementing plug at the lower end of the work string. The second cementing plug, referred to herein as the “top cementing plug”, is thereby released from the work string to separate the cement slurry from additional drilling fluid or other fluid used to displace the cement slurry through the casing string. The design of the top cementing plug is such that when it lands on the bottom cementing plug at the lower end of the casing string, it shuts off fluid flow through both the top and bottom cementing plugs, which prevents the displacement fluid from entering the well bore annulus.
The traditional cementing method described above involves a cementing manifold that comprises an integral part of the work string, thus requiring field personnel to work in close proximity to the work string to manually release darts during cementing operations. When operating from a drilling platform, for example, field personnel may be wenched into a harness and suspended from a derrick within reach of the cementing manifold so that such personnel may manually manipulate valves to release darts into the work string at desired times. This manual method of releasing darts creates the risk of injury to field personnel, especially when operating from an offshore floating platform, for example, where wind and waves create additional hazards to personnel suspended in a harness. Therefore, such manual methods of releasing darts from conventional cementing manifolds are not permitted in some countries, such as Norway, for example. Thus, an alternative method of releasing darts from the cementing manifold was developed wherein the cementing manifold valves are remotely actuated rather than manually actuated. Although such remote actuation methods address the concern about field personnel working in close proximity to the work string, the cementing manifold must still be capable of suspending the weight of the work string and casing string, containing pressure, transmitting torque, and rotating the work string. In addition, remote actuation of the cementing manifold valves to release darts adds complexity to the system, and therefore more cost and less reliability as compared to the traditional manual method using field personnel to manipulate the valves.
Thus, a need exists for apparatus and methods to remotely release actuating, wiping, and/or separating devices, such as mechanical plugs, into the work string during cementing operations, while reducing design complexity of the cementing manifold, reducing manufacturing costs, and increasing operational reliability.
Disclosed herein is a system for actuating a downhole tool disposed within a work string comprising a support suspending the work string into a well bore, a launching apparatus positioned at a location remote from the work string, a tortuous path connected between the launching apparatus and the work string, and a mechanical plug that launches from the launching apparatus, traverses the tortuous path, enters the work string, and actuates the downhole tool.
For a more detailed description of the present invention, reference will now be made to the accompanying drawings, wherein:
Certain terms are used throughout the following description and claims to refer to particular assembly components. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”.
A remote launching apparatus and mechanical plugs that may be released into a work string to actuate downhole tools will now be described with reference to the accompanying drawings, wherein like reference numerals are used for like features throughout the several views. There is shown in the drawings, and herein will be described in detail, one embodiment of a remote launching apparatus and two embodiments of mechanical plugs with the understanding that this disclosure is representative only and is not intended to limit the invention to the specific embodiments illustrated and described herein. One skilled in the art will readily appreciate that the remote launching apparatus is not limited to a design that launches any particular number of devices, but may be designed to launch one, two, or more devices, such as mechanical plugs. Moreover, one skilled in the art will understand that the mechanical plugs are not limited to the shapes disclosed herein but may assume many other shapes. Furthermore, the embodiments of the apparatus and methods disclosed herein may be used not only in a cementing operation, but in any well bore operation.
In the cementing operation shown in
While the representative cementing operation of
Referring now to
In operation, fluid 600 is conveyed by the supply pump 500 through the fluid supply line 123 into the inlet 445 of the remote launching apparatus 200. Depending upon the positions of valves 405, 406, 407, and 408, the fluid 600 then flows through the remote launching apparatus 200 along one or more of three paths: the throughbore 435, the first by-pass loop 425, and/or the second by-pass loop 430. The fluid 600 then exits the remote launching apparatus 200 at the outlet port 450 where it flows through the fluid delivery line 122 towards the cementing swivel 300. Two mechanical plugs 410, 420 are shown positioned within the throughbore 435 of the remote launching apparatus for release into the flowing fluid 600. These mechanical plugs 410, 420 may be released and transported by the fluid 600 to the work string 146 through manipulation of valves 405, 406, 407 and 408, either manually by field personnel, or by automated means. The mechanical plugs 410, 420 may be released either one at a time or simultaneously. Further, the dual mechanical plug configuration of the remote launching apparatus 200 shown in
In an alternative embodiment, as depicted in
Turning now to
Referring again to
Many different operations may be performed by launching one or more mechanical plugs 410, 420 from the remote launching apparatus 200, through the swivel 300, and into the work string 146 to actuate one or more downhole tools. One such operation comprises actuating a liner hanger 138 to suspend a new casing string 148 from existing and previously cemented casing 144. To perform this operation, the first mechanical plug 410 may be released from the remote launching apparatus 200 as will be described in more detail herein. In this case, the mechanical plug 410 is launched by pumping drilling fluid 600 via supply pump 500 for delivery through fluid delivery line 122. Before releasing the first mechanical plug 410, the top drive unit 108 is deactivated so that the mandrel 310 inside the cementing swivel 300 ceases to rotate. In an embodiment, the cementing swivel 300 comprises a locking mechanism (not shown) that enables the mandrel 310 to be locked into a position where the fluid channel 325 and the fluid port 330 align to maintain a flowpath through which the first mechanical plug 410 may pass as it travels through the cementing swivel 300 and into the work string 146. After the first mechanical plug 410 passes through the cementing swivel 300 and down the work string 146 past the flag sub 130, the mandrel 310 may be unlocked, and the top drive unit 108 reactivated to resume rotating the work string 146. As the mandrel 310 is rotating, drilling fluid may be supplied through the drilling fluid line 110, or through the fluid delivery line 122 via the fluid apertures 327 in the mandrel 310.
To begin the cementing operation, the remote launching apparatus 200 is first reloaded with another first mechanical plug 410 so that both mechanical plugs 410 and 420 may be launched during cementing. As will be described in more detail below, the embodiment of the remote launching apparatus 200 depicted in
As depicted in
As shown in
With the remote launching apparatus 200 loaded with mechanical plugs 410, 420, the cementing operation can commence. The kelly valve 112 is closed to block off the drilling fluid line 110, and the delivery valve 120 to the fluid delivery line 122 is opened, thereby opening a pathway for the first mechanical plug 410 propelled by the fluid 600, in this case cement, to flow through the swivel 300 and down into the work string 146. Again, the top drive unit 108 is deactivated and the mandrel 310 of the cementing swivel 300 is aligned and locked in place until the first mechanical plug 410 passes through. Downhole, the first mechanical plug 410 actuates the bottom cementing plug 150, which releases to land on the float collar 142 at the bottom of tubular 148. Thereafter, it is preferable to rotate the work string 146 during cementing to ensure that cement is distributed evenly around the new casing string 148 downhole. More specifically, because the cement is a thick slurry, it tends to follow the path of least resistance. Therefore, if the new casing string 148 is not centered in the well bore 140, the annular area 140 will not be symmetrical, and cement may not completely surround the tubular 148. Thus, in an embodiment, the mandrel 310 is unlocked and the top drive unit 108 is reactivated to continue rotating the work string 146 through the cementing swivel 300 while cement 600 is introduced from the fluid delivery line 122 into the throughbore 305 of the mandrel 310 via fluid apertures 327.
Referring to
Referring to
When the appropriate volume of cement has been pumped into the work string 146, a second mechanical plug 420 may be released from the remote launching apparatus 200 to wipe cement from the inner wall of the tubular 148 and launch the top cementing plug 152 to land on the bottom cementing plug 150 disposed on the float collar 142. Before the second mechanical plug 420 is released from the remote launching apparatus 200, the top drive unit 108 is again deactivated, and the mandrel 310 inside the cementing swivel 300 is aligned and locked into position so that the fluid channel 325 and the fluid port 330 align. This opens a flowpath through which the second mechanical plug 420 may pass as it travels through the cementing swivel 300 and into the work string 146. In one embodiment, the second mechanical plug 420 is propelled by drilling fluid. Once the second mechanical plug 420 has passed through the cementing swivel 300, the mandrel 310 may be unlocked and the top drive 108 reactivated to resume rotating the work string 146 and continue supplying drilling fluid, either through the drilling fluid line 110, or through the fluid supply line 122 and into the throughbore 305 of the swivel 300 via fluid apertures 327 in the mandrel 310. To resume normal operations, the delivery valve 120 to the fluid delivery line 122 is closed, and the kelly valve 112 to the drilling fluid line 110 is opened to supply drilling fluid to the work string 146.
Referring to
Referring to
As stated previously, the remote launching apparatus 200 may be positioned on the rig floor 126 or another location remote from the work string 146, thus allowing manual release of mechanical plugs 410, 420 by field personnel without placing those personnel in close proximity to the work string 146, and without requiring such personnel to be suspended from a harness connected to the derrick 132, for example. Also, by locating the launching apparatus 200 remote from the work string 146, it need not be designed to handle the weight of the work string 146 and the casing string 148, nor to transmit torque, nor to allow rotation therethrough. Positioning the launching apparatus 200 remotely from the work string 146 does, however, necessitate a different design for the mechanical plugs 410, 420 as compared to traditional darts used to wipe pipe surfaces, separate fluids, and/or actuate downhole tools.
Because conventional cementing methods use a cementing manifold installed in substantial vertical alignment with the work string 146 to form an integral part thereof, the darts released from a conventional cementing manifold are designed for travel along an essentially straight path downwardly through the work string 146. Such conventional darts are not designed to traverse a tortuous path, such as the flowpath provided by the fluid delivery line 122 between the remote launching apparatus 200 and the swivel 300. As shown in
Thus, in contrast to conventional darts that only travel along an essentially straight-line path, the mechanical plugs 410, 420 disclosed herein are released from a launching apparatus 200 located remotely from the work string 146, such as the rig floor 126 or another remote location, to travel through the tortuous path provided by the fluid delivery line 122 into the swivel 300. By the time these mechanical plugs 410, 420 reach the swivel 300, they may have traversed a flowpath that changed elevation, diameters, and direction a number of times. Because this flowpath is a tortuous path comprising multiple obstacles, the use of conventional darts would be unsuitable for the methods disclosed herein because such conventional darts would become stuck inside the tortuous path presented by the fluid delivery line 122 and/or become damaged by traversing the obstacles presented therein.
To address such limitations,
The spherical mechanical plug 400 comprises a spherical solid core 460 surrounded by a concentric flexible layer 470. The solid core 460 is constructed from any material suitable for use in a well bore environment, including, but not limited to plastics, phenolics, composite materials, high strength thermoplastics, wood, glass, metals such as aluminum or brass, or combinations thereof. If the spherical mechanical plug 400 is intended to actuate a particular downhole tool, the size of the solid core 460 is designed to seat on that downhole tool and also pass through any constrictions in the tortuous flowpath, such as the interior of valves as well as corners and bends. The thickness of the flexible layer 470 is determined based upon the internal diameter of the work string 146 and tubular 148 such that the flexible layer remains substantially in contact with the surrounding pipe wall as the spherical mechanical plug 400 travels. The flexible layer 470 may be constructed from any flexible material having sufficient density, firmness and resilience to resume approximately its original shape after passing through a constriction. Such flexible materials include, but are not limited to, natural rubber, nitrile rubber, styrene butadiene rubber, polyurethane, or combinations thereof. As the spherical mechanical plug 400 travels along the flowpath from the remote launching apparatus 200 to its final destination inside the work string 146, the mass of the solid core 460 prevents the spherical mechanical plug 400 from becoming stuck when the flowpath changes direction, while the flexible layer 470 repeatedly compresses and expands through constrictions to remain in contact with the surrounding pipe wall. Substantially regular contact between the flexible layer 470 and the surrounding pipe wall surfaces permits the spherical mechanical plug 400 to effectively wipe the pipe wall surfaces and/or separate the fluid ahead of the spherical mechanical plug 400 from the fluid following the spherical mechanical plug 400. Upon arriving at its final destination, the mass of the solid core 460 permits the spherical mechanical plug 400 to exert sufficient force to actuate a downhole tool.
While various embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this disclosure. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the apparatus and methods are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.
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