Sealing Mechanism to Be Used in a Well Beyond a Tight Spot or in Inverted Casing

Abstract

Downhole oil tools such as anchors and packers with mechanical setting and sealing mechanisms are not able to travel through narrower casing and then set in wider casing. This invention is a sealing mechanism which can expand enough to set a tool in a wider casing, but still travel through the narrower casing or tight spot above.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to downhole oil tools which are used during completion and production of a well, particularly a sealing mechanism which prevents liquids and other materials from travelling through the annular space of the well, outside of and around the tool.

Description of the Related Art

When drilling a well, casing is often installed to protect the integrity of the hole. Wider casing is set at the top of the hole, and successively narrower casing must travel down the hole through the wider casings, so that the inner diameter of the well gets narrower as the depth increases. In other words, the inner diameter is wider at the top of the hole, and narrower at the bottom of the hole, and the inner diameter steadily decreases from top to bottom. Occasionally, the casing is installed in a different configuration, with wider casing placed below narrower casing. We call this inverted casing.

Sizes of casing are referred to by outer diameter in inches, and weight in pounds per foot, which can be used to figure the inner diameter. Sometimes a “tight spot” exists in the casing, which can be caused for example by a casing patch, or inverted casing installation. At the tight spot, the inner diameter of the casing is smaller than the inner diameter below the tight spot.

During the completion and production stages of an oil or gas well, downhole tools such as packers must be lowered down the well, inside the casing, and set to stay at a given depth. Conventional downhole tools are made to travel down through the wider casing, then set at a given depth and size of casing. A conventional tool has an outer diameter which is slightly less than the diameter of the well casing where it is intended to set. Such a tool is not able to travel through a tight spot, because its outer diameter is too wide to fit. Conventional mechanical setting and sealing mechanisms must expand only a very short distance between the tool and the casing. For example, in 2⅜ inch casing, a standard tool's mechanical sealing mechanism expands radially approximately ⅛ of an inch (32 mm.)

No existing mechanical downhole tools are able to travel through a narrower casing than that in which they are made to set. They simply cannot both fit through a narrower casing or tight spot, and still expand enough to set and/or seal in the lower wider casing. Mechanical tools have the advantage of being retrievable and reusable; they set and seal immediately; do not require fluid or pressure to be present in the well or tubing; and are available in a wide range of sizes.

The inventors are aware of inflatable packers which are set through either fluid or hydraulic means. Inflatable packers require fluid and pressure to set, are significantly more expensive than mechanical packers, and have a lower pressure rating. Swellable packers may take days to set, require an activating agent such as water or oil, are not removable, and are significantly more expensive than mechanical packers. Hydraulically set downhole tools and packers require more equipment to set, and are more expensive than mechanical packers.

BRIEF SUMMARY OF THE INVENTION

Downhole tools which set at a certain depth in the well often have a setting mechanism which angles out and grabs onto the sides of the well casing, preventing movement of the tool. The setting mechanism is often made of small machined or cast pieces of metal alloy called slips, which are pushed out by a cone.

Some downhole tools also have a separate sealing mechanism which creates a seal between the tool and the well casing, so that fluid or gas cannot flow around the tool in the annulus, up or down the well. This sealing mechanism is often made of dense synthetic rubber, such as nitrile, butyl or urethane, and is known in the field as an elastomeric or rubber element. The term “rubber element” as used herein is a tube which may be made of natural rubber, nitrile, butyl, urethane, or other synthetic rubber. During the setting process, a portion of the tool moves and compresses the rubber element longitudinally, causing it to expand radially, outward toward the casing.

This invention includes a rubber element which radially expands more than a conventional rubber element, providing a seal with well casing of an inner diameter that is significantly wider than the outer diameter of the unexpanded rubber element. For example, a packer built and tested by the inventors uses a rubber element with an outer diameter of 1.875 inches (476 mm), and can set and seal in casing with inner diameter of 2.41 inches (612 mm), thus expanding 0.535 inches (136 mm) or 28.5%. This invention also includes downhole tools which use the novel rubber element, and may also use a system of slips which are able to angle out and grab onto the sides of well casing with an inner diameter which is significantly wider than the outer diameter of the tool.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a full exterior view of a packer with the setting mechanism of slips and sealing mechanism of a rubber element, before it is set in the casing.

FIG. 2 shows a lengthwise cutaway view of the packer in FIG. 1.

FIG. 3 shows a full exterior view of the same packer shown in FIGS. 1 and 2, which has been set in the well casing with the well casing shown cut away. The setting mechanism is shown holding onto the casing, as well as the sealing mechanism expanded against the casing.

FIG. 4 shows a lengthwise cutaway view of the packer shown installed in casing in FIG. 3.

FIG. 5 shows a lengthwise cross section of the uncompressed rubber element

FIG. 6 shows a lengthwise exterior view of the uncompressed rubber element.

FIG. 7 shows an angled exterior view of the uncompressed rubber element.

FIG. 8 shows an exterior view of a slip assembly.

FIG. 9 shows a full exterior view of a pump anchor with the setting mechanism of slips and sealing mechanism of a rubber element, before it is set in the casing.

FIG. 10 shows a lengthwise cutaway view of the pump anchor in FIG. 9.

FIG. 11 shows a full exterior view of the same pump anchor shown in FIGS. 9 and 10, which has been set in the well casing with the well casing shown cut away. The setting mechanism is shown holding onto the casing, as well as the sealing mechanism expanded against the casing.

FIG. 12 shows a lengthwise cutaway view of the pump anchor shown installed in casing in FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

The invention is a component of a sealing mechanism which seals the annular space between the outer surface of an object inside a pipe and the inner surface of the pipe. The invention can be used with a downhole oil tool, such as a packer or anchor. The described sealing mechanisms can be used with the described setting mechanism on any tool that requires both a setting and sealing mechanism, or it can be used without a setting mechanism. The sealing mechanism may be present on the same downhole tool as the setting mechanism, or it may be independently present on a downhole tool, utilizing alternative means of setting.

The sealing mechanism consists of a rubber element which is compressed by other parts of a downhole tool. The design of the rubber element is novel. When choosing the durometer and type of synthetic rubber of a rubber element, a person skilled in the art must know certain conditions in the well where the tool will be installed, such as the expected temperature and the depth where the tool will be set. Durometer is a standard measurement of the hardness of rubber. The rubber element in the claimed sealing mechanism must have a durometer which is lower, meaning softer, than what would normally be used in the field for a given set of conditions. The particular kind of synthetic rubber, such as nitrile rubber, may vary according to the conditions of the well where the tool is being used, and the choice of rubber should not affect the functionality as far as compression and expansion.

The staggered arrangement of grooves both inside and outside of the rubber element is novel, and the grooves make the shape of the expanded rubber element predictable and consistent. An inner groove makes the rubber on the outside at that point bulge out, and an outer groove makes the rubber on the inside at that point bulge inward. The rubber element shown in FIGS. 5, 6 and 7 (with five grooves, two on the outside and three on the inside) makes contact in at least three places on the outside against the casing, and in at least four places on the inside against the mandrel of the packer or other tool on which it is installed. If grooves were not present, the rubber element might expand in an unpredictable shape, and might not create a seal where needed.

The rubber element used in the claimed sealing mechanism is thinner than what would generally be used for a tool of a given size, to allow the inner diameter of the tool to be as wide as possible to maximize flow of fluid or gas inside the tool during use, but still allowing the tool to fit through a tight spot while it is being installed. Finally, the rubber element is relatively long from top to bottom as installed, to allow for room for the several grooves and the spacing between the grooves. The durometer, length and the placement of grooves are what allow the rubber element to expand more than a standard rubber element would on a tool of the same size. Other embodiments would include a longer element, and/or a greater number of interspersed outer and inner grooves, allowing for a greater number of contact points. In an embodiment built and tested by the inventors, which was a packer made to travel through 2⅜ casing and set and seal in 2⅞ casing, the rubber element was able to seal against well casing with an inner diameter between 0.6 and 0.7 inches (15.2 to 17.8 mm) wider than the outer diameter of the unexpanded rubber element.

FIGS. 1 and 2 show the claimed sealing mechanism installed on an embodiment of a packer. Packers are used to isolate a zone in a well during the completion, production and stimulation phases of an oil and gas well.

The packer, in an embodiment shown in FIGS. 1, 2, 3 and 4, is to be installed in the orientation shown, with 1 on top and 11 on the bottom. The packer is an assembly of several distinct parts, as labeled in FIGS. 1, 2, 3 and 4. 1 is a top sub, which is screwed onto the outside of the mandrel 2. The mandrel 2 extends all the way down to the bottom sub 12, which is screwed onto the outside of the bottom end of the mandrel 2. These three pieces are hollow inside, to allow a rod to be inserted all the way through the packer after the packer is installed and set in the hole. 3 is a J-housing, which surrounds the mandrel 2 like a pipe, and which has two j-shaped openings, only one of which is shown, into each of which a pin 4 on the mandrel fits.

5 labels three drag springs, which are attached to the J-housing 3, and which prevent the J-housing from rotating in the well during the setting process. 6 is a slip assembly which includes three slips, some of which are shown, which are attached to the J-housing 3. Just below the slip assembly 6 is the cone 7. The cone 7 touches the rubber element 8, which in turn is above the guide 9. The guide 9 is fixed to the mandrel 2 with shear pins 10, whereas the J-housing 3, slip assembly 6, cone 7 and rubber element 8 are not fixed to the mandrel 2, and can slide up and down around the mandrel 2.

FIG. 3 shows the same packer, except in this figure, the packer is installed in the well casing, meaning that both the setting mechanism and the sealing mechanism have been engaged, so that the packer will not move up or down in the hole, and no fluid or gas can flow in the annular space around the packer. 12 is the well casing, which lines the inside of the well, protecting the integrity of the hole so that it does not collapse, and preventing fluids travelling up and down the hole from seeping into formations along the sides of the hole, as well as preventing unwanted formation fluids from flowing into the hole. The casing 12 is the surface upon which the setting mechanism grabs, and the sealing mechanism seals. The crosshatched areas surrounding the casing represent the geological formation through which the well has been drilled. The end of the tubing 13, which lowers the tool into the well, is shown screwed into the top sub 1.

In FIG. 3, items 1 through 11 represent the same items in FIG. 1, except that the cone 7 has slid upwards, forcing the slips on the slip assembly 6 to move radially outward and press against the casing 12, holding the packer in place. In addition, the guide 9, along with the mandrel 2, has moved upwards, and vertically compressed the rubber element 8, causing the rubber element 8 to expand its outer diameter to make enough contact with the casing 12 to make a seal.

FIGS. 2 and 4 are cutaway views to show more particularly the mandrel 2, which extends inside other components throughout almost the entire length of the tool.

FIGS. 1, 2, 3 and 4 show one embodiment of how the disclosed setting mechanism and sealing mechanism can be used with a packer.

FIG. 5 shows a cross section, lengthwise, of an embodiment of the claimed rubber element. The pictured embodiment has two grooves on the outer surface which extend all the way around the outer circumference of the hollow cylindrical tube, and three grooves on the inner surface which extend all the way around the inner circumference of the hollow cylindrical tube. All grooves are parallel to each other. The cut or mold of the grooves pictured have a semicircular shape, but grooves with other shapes such as a U or V shape, or a rectangular shape would give the same functionality. The grooves might also have different sizes. The grooves in this embodiment were machined, but grooves created by molding or other method would give the same functionality.

The grooves are staggered, with an inner groove closest to the top end, then an outer groove a bit closer to the midpoint of the hollow cylindrical tube, then an inner groove at or close to the midpoint of the hollow cylindrical tube, then the second outer groove closer to the bottom end, then the last inner groove still closer to the bottom end of the hollow cylindrical tube. The five grooves are spaced approximately evenly from each other, and an inner and an outer groove are never placed concentrically to each other. Other embodiments would include different numbers of inner and outer grooves, placed in a similar staggered configuration, to make the rubber element expand in a predictable way. Other embodiments would include grooves which are not equidistant from each other. A further example of a possible embodiment includes the possibility for multiple inner grooves (or outer grooves) between a pair of outer grooves (or inner grooves). Furthermore, it is possible that the outermost grooves be located either on the inside or the outside of the element, or one of each.

FIGS. 6 and 7 are views of the exterior of the rubber element, showing only the outer grooves, with the inner grooves hidden.

FIG. 8 is an exterior view of a slip assembly, which is part of the setting mechanism used in the packer shown in FIGS. 1, 2, 3 and 4, and the pump anchor shown in FIGS. 9, 10, 11 and 12.

Many downhole tools use slips as a setting mechanism, as well as a rubber element as a sealing mechanism. The new features of this invention allow the rubber element to seal at a significantly wider inside diameter of casing than where a downhole tool of given outer diameter would traditionally be able to set and seal.

FIGS. 1, 2, 3 and 4 show the setting mechanism and sealing mechanism on a tension set packer. Tubing is attached to the top sub 1, as shown in FIGS. 3 and 4, and then the packer is lowered down the well hole. As the packer Is lowered through successively narrower inside diameters of casing, the drag springs 5 may touch the casing. The drag springs 5 are made to compress radially and extend down as the inside diameter of casing gets tighter. In order for the packer to pass through casing, the packer's outside diameter, which is widest at the guide 9, must be narrower than the narrowest inside diameter of the casing.

When the packer reaches the desired depth, the installer stops lowering the tubing, and then lifts up and turns the tubing approximately 90 degrees to make the top sub 1, mandrel 2, guide 9 and bottom sub 11 twist. The J-housing 3 does not twist, because the drag springs 5 attached to the J-housing 3 create friction to prevent the J-housing 3 from twisting. The pins 4 which are attached to the mandrel 2 move through the J-shaped openings in the J-housing 3. The installer then pulls up more on the tubing, which causes the top sub 1, mandrel 2, cone 7, rubber element 8, bottom sub 11 and guide 9 to travel up, while the J-housing 3, drag springs 5, and slip assembly 6 stay in place. The guide 9 pushes up on the rubber element 8, which begins to compress vertically and expand radially, but also pushes up in turn on the cone 7. As the cone 7 travels up, it pushes the slips on the slip assembly 6 out toward the casing 12. The cone 7 continues to travel up until the slips in the slip assembly 6 have been pushed out enough to grab onto the inside of the casing 12. At this point, the cone 7 can travel no further, as the slips cannot move further. The guide 9 continues to travel upwards, vertically compressing the rubber element 8 further against the cone 7 until it expands radially enough to create seals both against the inner surface of the casing 12 and against the outer surface of the mandrel of the packer 2. FIGS. 3 and 4 show an embodiment of a packer with both the setting mechanism and sealing mechanism engaged with the casing 12. A comparison of FIGS. 3 and 4 with FIGS. 1 and 2 show that when both mechanisms are engaged, the drag springs 5 are pushed in by the casing 12; the slips in the slip assembly 6 are pushed out by the cone against the casing 12; and the rubber element 8 has been vertically compressed but radially expanded so that it presses against both the casing 12 and the mandrel 2.

FIGS. 9 and 10 show the claimed sealing mechanism installed on a pump anchor. Pump anchors are used during the production phase of an oil and gas well, just above a pump, to anchor (hold in place) and pack off (seal and isolate from the well above or below) the pump.

The pump anchor, in an embodiment shown in FIGS. 9 and 10, is to be installed in the orientation shown, with 21 on top and 32 on the bottom. The pump anchor is an assembly of several distinct parts, as labeled in FIGS. 9 and 10. 21 is a top sub, which is screwed onto the outside of the mandrel 25. The mandrel 25 extends all the way down to the bottom sub 32, which is screwed onto the outside of the bottom end of the mandrel 25. Much like the packer embodiment described above, the pump anchor has a guide 22, a rubber element 23, a cone 24, and a slip assembly 26. The drag springs 30 are attached to the upper drag ring 27 and lower drag ring 31 with the screws 28. The control ring 29 is held between the upper drag ring 27 and the lower drag ring 31.

Tubing and/or a sucker rod 33 is attached to the pump anchor at the top sub 21, as shown in FIGS. 11 and 12. A pump (not shown) would be below the bottom sub 32. The pump anchor and pump are lowered down the well, and when they reach the desired depth, the operator pulls up slightly. This causes a pin in the control ring 29 to catch in a slot in the mandrel 25, so that when the operator allows the pump anchor to lower again, the slip assembly 26, upper drag ring 27, control ring 29, lower drag ring 31, and drag springs 30 stay in place while the mandrel 25, cone 24, rubber element 23 and guide 22 travel downwards. Like the packer described above, the cone 24 travels downward until it goes under the slip assembly 26 and causes the slips to jut outward and grab onto the well casing or tubing. The guide 22 continues to move downwards, compressing the rubber element 23 between the guide 22 and the cone 24, until the rubber element 23 expands radially enough to create a seal against both the casing or tubing and the mandrel 25.

The claimed sealing mechanism could also be used with a downhole tool which is set using compression, rather than tension. The configuration of parts of the tool would be slightly different, and generally reversed, so that instead of pulling up to activate the setting mechanism and sealing mechanism, the operator would push down on the tubing.

The claimed sealing mechanism could also be used with a downhole tool which is set using rotation, rather than tension or compression. For a rotationally set tool, the setting mechanism would be installed on an anchor, which would travel down into the casing before and under a packer, which would have the claimed sealing mechanism. After the anchor is set, the operator rotates the packer in order to engage the seal.

The claimed sealing mechanism could also be used with a downhole tool which is set by a hydraulic method. For a hydraulically set tool, the setting procedure causes fluid in the tubing to make a cylinder inside the tool push up or down, which in turn packs off the rubber element, meaning it compresses the rubber element longitudinally, so that the rubber element expands radially, and engages the seal.

Claims

1. A component of an apparatus for sealing an annular space, the component comprising: A tube made of synthetic rubber; THE IMPROVEMENT COMPRISING: A circumferential groove or grooves located on the inner and/or outer surface of the tube.

2. An apparatus comprising: a tube made of synthetic rubber, with a circumferential groove or grooves located on the inner and/or outer surface of the tube; and means for compressing the tube longitudinally.

3. The apparatus of claim 2, wherein the tube has a plurality of circumferential parallel grooves arranged in an alternating pattern between the inner and outer surface of the tube.

4. The apparatus of claim 2, wherein the tube's circumferential parallel grooves are arranged as follows, from one end to the other: outer, then inner, then outer, then inner, then outer; with none radially concentric.

5. A packer which includes the invention of claim 2 as a sealing mechanism.

6. A packer which includes the invention of claim 3 as a sealing mechanism.

7. A packer which includes the invention of claim 4 as a sealing mechanism.

8. A pump anchor which includes the invention of claim 2 as a sealing mechanism.

9. A pump anchor which includes the invention of claim 3 as a sealing mechanism.

10. A pump anchor which includes the invention of claim 3 as a sealing mechanism.