MULTI-SECTIONAL SWELLABLE PACKER

Abstract

A multi-sectional swellable packer for a wellbore has a mandrel and multiple packer elements mounted on the mandrel. The packer elements are formed of swellable materials that swell when contacted with a swelling fluid. In various embodiments, the outer diameter of the central element is larger than that of the end elements with or without gap between elements. In other embodiments, a multi-sectional swellable packer for a wellbore has multiple mandrels with multiple packer elements which are interconnected by flexible joints/connections. The outer diameter of the central element can be different from that of the end elements. The swellable rubber of the central element can be different from that of the end elements. The packer increases flexibility of operation and reduces the risk of run-in-hole.

Description

FIELD

The disclosure relates generally to a wellbore system for oil exploration. The disclosure relates specifically to a packer for a wellbore system.

BACKGROUND

Many wellbore systems include a packer, which is designed to expand radially outwardly from a pipe against the wall of the wellbore. The packer is intended to seal segments of the pipe against wellbore in order to isolate some sections of the wellbore from others. Known sealing members for packers include mechanical packers which are arranged in the borehole to seal an annular space between a wellbore casing and a production pipe extending into the borehole. Such a packer is radially deformable between a retracted position, in which the packer is lowered into the borehole, and an expanded position, in which the packer forms a seal.

In horizontal laterals, especially long ones, cementing can be very difficult and can easily damage the formation. It, therefore, brings the opportunities to open-hole fracturing. In Open-hole completion, swellable packer can be used to seal irregular well bores in open holes.

Operationally, the benefit of a swellable packer is simplicity. There is no moving part required to work, through pipe manipulation or by applying hydraulic pressure. No special service personnel are needed. The packers are simply run to depth, similar to the casing, and allowed to swell before production or injection operations begin.

Pressure rating of swellable rubber is typically low per unit length. A lengthy swellable rubber is needed to hold the specific differential pressure.

In general, each foot of swellable rubber provides 1 ksi differential pressure. In order to achieve 10 ksi differential pressure, it is required the swellable packer to be at least 12 feet. The lengthy swellable rubber brings up the difficulty and risk of run-in-hole. In the meantime, however, the real pressure rating required from the field may not be as high as 10 ksi. It is, therefore, a need of flexibility of operation if there is a multi-section swellable packer.

Both ends of a long rubber swell and come into contact with the well bore earlier than the rest due to their full contact with the fluid at the ends. On the other hand, the swelling capability of rubber in the middle is delayed since the absorption of water from brine by the rubber increases the salinity of the surrounding brine. Since the rubber at the two ends contact with the wall first, the middle of most of the rubber lacks sufficient contact with fresh brine. The delayed swelling in the middle forms a “saddle” effect. As an overall impact, the swelling efficiency and pressure rating of a swellable packer with lengthy rubber is negatively affected.

Running a multi-mandrel packer in a hole provides flexibility. The length of the packer can be adjusted by changing the number of mandrels in the pack, such that the length of the packer can match the pressure required from the field. Furthermore, when the connection is flexible, the multi-mandrel packer can be easier to run-in-hole than a one mandrel packer, especially in a long horizontal well where the well bore trajectory is torturous, because each mandrel in a multi-mandrel packer is much shorter than the mandrel in one mandrel packer.

SUMMARY

An embodiment of the disclosure is a packer comprising: a mandrel; and a plurality of packer elements mounted on the mandrel; wherein the packer elements comprise end elements and a central element arranged between the end elements; wherein the packer elements are formed of swellable material that swells when contacted with a swelling fluid. In an embodiment, the outer diameter of the central element is different than that of the end elements. In an embodiment, the outer diameter of the central element is larger than that of the end elements. In an embodiment, the outer diameters of the central element and end elements are increased gradually along the direction from ends to the center of the mandrel. In an embodiment, the packer elements abut each other. In an embodiment, gaps exist between the packer elements. In an embodiment, the central element and end elements are formed of a unitary packer member.

An embodiment of the disclosure is a packer comprising: a plurality of mandrels having the same inner diameter; a plurality of connection elements coupled to the plurality of mandrels; a plurality of packer elements that circumferentially fit over the mandrels, wherein the plurality of packer element each have an outer diameter; and wherein the packer elements are formed of a swellable material. In an embodiment, the plurality of connection elements can connect adjacent mandrels in the plurality of mandrels. In an embodiment, the connection elements are flexible connections. In an embodiment, the connection elements are screw type closure structures. In an embodiment, the screw type closure structure comprises a male threaded member; a female threaded member; wherein the male threaded member and the female threaded member are screwed into a complementary threaded engagement. In an embodiment, a gullet is set below the normal root portion of at least one of two mating threads and wherein a flank of at least one of the mating threads is crowned. In an embodiment, when the mandrels connect with each other to form a multi-mandrel packer wherein the outer diameter of the center packer element is different the outer diameter of the end packer element. In an embodiment, the outer diameter of the central packer element is larger than the outer diameter of the end packer element. In an embodiment, when the mandrels connect with each other to form a multi-mandrel packer wherein the swellable materials of the packer elements have different swelling speeds. In an embodiment, the swelling speed of the center packer element is faster than the swelling speed of the end packer element.

An embodiment of the disclosure is a method of manufacturing the packer above comprising vulcanizing different materials on a mandrel to form packer elements; and machining the packer elements to form different outer diameters.

As a first aspect, embodiments of the present disclosure are directed to a multi-sectional swellable packer for a wellbore. The packer comprises a mandrel and multiple packer elements mounted on the mandrel. The packer elements are formed of swellable material that swells when contacted with a swelling fluid.

In one embodiment, select a fast swelling rubber in the center of the mandrel and select a slow swelling rubber in the ends of the mandrel.

In another embodiment, make large outer diameter (OD) of the rubber in the center and make small OD of the rubber in the ends of the mandrel.

As a second aspect, embodiments of the present disclosure are directed to a multiple mandrels swellable packer for a wellbore. The packer comprises multiple mandrels having the same inner diameter, connection elements coupled to the mandrels which can connect adjacent mandrels, packer elements that fit circumferentially over the mandrels and are formed of swellable material, and each packer element having an outer diameter.

In one embodiment, the connection elements are a screw type closure structure, a male threaded member and a female threaded member screwed into a complementary threaded engagement, a gullet set below the normal root portion of at least one of the two mating threads, and the flank of at least one of said mating threads being crowned.

In another embodiment, the outer diameter of the center packer element is larger than that of the end packer element.

In yet another embodiment, the swellable materials of the packer elements have a different swelling speed. The swelling speed of the center packer element is faster than that of the end packer element.

In another embodiment, the manufacturing process of multi-section swellable packer is to vulcanize the different materials on one mandrel followed by OD machining. After machining, the rubbers are bonded strongly on the mandrel.

The present disclosure can significantly improve the sealing efficiency of the packer by multi-section packers with different rubber materials, different OD and specially designed connection, improve effective sealing area of the swellable rubber by increasing the sealing pressure per unit of length of the rubber, Improve the flexibility of run-in-hole, and improve the flexibility of assembly of multiple sections on the well site, reducing the challenge of run-in-hole and saving the overall cost.

By applying the multi-sectional swellable packer, the sealing efficiency of the packer will significantly improve by multi-section packers with different rubber materials, different OD and specially designed connection; improve effective sealing area of the swellable rubber by increasing the sealing pressure per unit of length of the rubber; improve the flexibility of run-in-hole; improve the flexibility of assembly of multiple sections on the well site, reducing the challenge of run-in-hole and saving the overall cost.

The foregoing has outlined rather broadly the features of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter, which form the subject of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and other enhancements and objects of the disclosure are obtained, a more particular description of the disclosure briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 shows a swellable packer annular seal in an irregular holes;

FIG. 2 shows a multi-section swellable packer in a prior art;

FIG. 3 shows another multi-section swellable packer in a prior art;

FIG. 4 shows stacking water swell sleeves: 2 ft. and 3 ft. elements to hold 5 ksi in a prior art;

FIG. 5 shows a SwellFix Packer that can hold up to 10 ksi, depending on the rubber length combination in the prior art;

FIG. 6 shows a saddle effect of a swellable packer in the prior art;

FIG. 7 shows a multi-section swellable packer with a large outer diameter in the center and without a gap between sections;

FIG. 8 shows a swellable packer with a gradual outer diameter change;

FIG. 9 shows a multi-section swellable packer with a large outer diameter in the center and having gaps between sections;

FIG. 10 shows a multi-section swellable packer with gradual outer diameter change and having a gap between sections;

FIG. 11 shows a multi-section swellable packer with different diameter rubber;

FIG. 12 shows a multi-mandrel swellable packer with flexible joints/connections;

FIG. 13 shows the connection of FIG. 12;

FIG. 14 shows a multi-mandrel swellable packer with connections; and

FIG. 15 shows the multi-stage fracturing using a multi-mandrel swellable packer.

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of various embodiments of the disclosure. In this regard, no attempt is made to show structural details of the disclosure in more detail than is necessary for the fundamental understanding of the disclosure, the description taken with the drawings making apparent to those skilled in the art how the several forms of the disclosure may be embodied in practice.

The following definitions and explanations are meant and intended to be controlling in any future construction unless clearly and unambiguously modified in the following examples or when application of the meaning renders any construction meaningless or essentially meaningless. In cases where the construction of the term would render it meaningless or essentially meaningless, the definition should be taken from Webster's Dictionary 3^rd Edition.

In an embodiment, the multi-section swellable packer can comprise a combination of different swellable rubbers and connection designs. In an embodiment, the multi-section swellable packer possesses high efficiency of swellable rubber per unit length and high flexibility of assembly at the well site. In an embodiment, the difficulty and the risk of swellable packer run-in-hole process is reduced. In an embodiment, the E&P efficiency of hydrocarbons from formations with low pressure, low permeability, and low abundance is improved by increasing the fracturing efficiency using the multi-section swellable packer.

FIG. 1 shows a swellable packer annular seal in irregular holes. The seal is formed of swellable elastomer. The elastomer expands radially when exposed to an activating liquid, such as water or hydrocarbon. Exemplary elastomer materials that swell in hydrocarbon include but are not limited to ethylene propylene rubber (EPM and EPDM), ethylene-propylene-diene terpolymer rubber (EPT), butyl rubber, brominated butyl rubber, chlorinated butyl rubber), chlorinated polyethylene, neoprene rubber, styrene butadiene copolymer rubber (SBR), sulphonated polyethylene, ethylene acrylate rubber, epichlorohydrin ethylene oxide copolymer, silicone rubbers and fluorsilicone rubber. Exemplary materials that swell in water include starch-polyacrylate acid graft copolymer, polyvinyl alcohol cyclic acid anhydride graft copolymer, isobutylene maleic anhydride, acrylic acid type polymers, vinylacetate-acrylate copolymer, polyethylene oxide polymers, carboxymethyl cellulose type polymers, starch-polyacrylonitrile graft copolymers and the like and highly swelling clay minerals such as sodium bentonite. The shape of the annular seal can adapt to irregular holes.

FIG. 2 depicts a Q-Seal multi-section vulcanized swellable packer by Ruma Rubber. FIG. 3 depicts a Q-Stax multi-section slide-on swellable packer by Ruma Rubber. They use the same rubber with the same outer diameter (OD) and have space or a space ring between the sections. Both ends of a rubber swell come into contact with the well bore earlier than the rest due to their full contact with the fluid at the ends. On the other hand, the swelling capability of rubber in the middle is delayed since the absorption of water from brine by the rubber increases the salinity of the surrounding brine. Since the rubber at the two ends contacts with the wall first, the middle of most of the rubber lacks sufficient contact with fresh brine.

FIGS. 4 and 5 show Stacking Water Swell Sleeves and SwellFix multi-section swellable packer by Tendeka. In an embodiment, the same rubber is used with the same OD. In an embodiment, there is a spacer or spacer ring between the sections. FIG. 4 shows stacking water swell sleeves: 2 ft. and 3 ft. elements to hold 5 ksi. FIG. 5 shows a SwellFix Packer that can hold up to 10 ksi, depending on the rubber length combination.

FIG. 6 depicts that the delayed swelling in the middle forms a “saddle” effect. As an overall impact, the swelling efficiency and pressure rating of swellable packer with lengthy rubber is negatively affected.

FIG. 7 shows a multi-section swellable packer with a large outer diameter in the center. The swellable packer includes a mandrel and multiple packer elements mounted on the mandrel. The packer elements are formed of swellable material that swells when contacted with a swelling fluid. A large outer diameter swelling element is present in the center of the mandrel and two small outer diameter swelling rubbers are present at the both ends of the mandrel. There is no gap between the swellable elements. In an embodiment, the packer comprises one mandrel made of one material.

FIG. 8 shows a swellable packer with gradual outer diameter change in accordance with one embodiment of the present disclosure. In this embodiment, the swellable packer includes a mandrel and a packer element mounted on the mandrel, the packer element is formed of a single material, but it is tapered, such that it has a larger central portion and narrow ends. Thus, when the packer element is contacted with an activating liquid, the central portion and the ends may swell, but the central portion seals the wall more rapidly than the ends, which avoids forming a “saddle” in the packer. In another embodiment, for example in FIG. 10, the swellable packer in FIG. 8 can be separated into a plurality of elements which have gaps between them. In an embodiment, the packer comprises one mandrel made of one material.

Select the fast swelling rubber in the center; select the slow swelling rubber in the ends; make large OD of the rubber in the center; and make small OD of the rubber in the ends. The manufacturing process of a multi-section swellable packer is to vulcanize the different materials on one mandrel followed by OD machining. After machining, the rubbers are bonded strongly on the mandrel.

FIG. 9 depicts a multi-section swellable packer with a large outer diameter in the center. The swellable packer includes a mandrel and multiple packer elements mounted on the mandrel. The packer elements are formed of swellable material that swells when contacted with a swelling fluid. A large outer diameter swelling element is present in the center of the mandrel and two small outer diameter swelling rubbers are present at both ends of the mandrel. In some embodiments, gaps may exist between the swellable elements (FIG. 9). In an embodiment, the packer comprises one mandrel made of one material.

FIG. 10 shows a multi-section swellable packer with different diameter rubber. The swellable packer includes a mandrel and multiple packer elements mounted on the mandrel. The packer elements are formed of a swellable material that swells when contacted with a swelling fluid. In an embodiment, the packer includes a center element with a large outer diameter in the center and a decreasing outer diameter toward the ends of the center element. There are two end elements that are directly or indirectly adjacent to the center element. The two end elements have a decreasing outer diameter away from the center element. The largest outer diameter of the end elements is smaller than the smallest outer diameter of the center element. The elements may abut each other or have gaps between adjacent elements. When contacted with activating liquid, the center element swells and takes less time to contact and seal against the wall of wellbore than the end elements. Thus the center element can sufficiently swell to seal against the wall. In an embodiment, the packer comprises one mandrel made of one material.

A conventional single element swellable packer swells fast at the ends. After the two ends contact the well bore or casing, the rubber in the center is swelling by diffusion which is slow and affects the swelling rate of the whole packer. By using different rubber materials, it allows swelling faster in the center so that the whole packer can evenly and thoroughly swell. Similarly, with a larger OD in the center than the end, the rubber in the center can contact the well bore or casing earlier so that the whole packer can finish swelling evenly and thoroughly.

FIG. 11 shows a multi-section swellable packer with different diameter rubber.

FIG. 12 shows a multi-mandrel swellable packer with flexible joints/connections.

In another embodiment, a multiple mandrel swellable packer for a wellbore is provided. Referring to FIG. 12, the packer comprises multiple mandrels having the same inner diameter, connection elements coupled to the mandrels which can connect adjacent mandrels, packer elements that fit circumferentially around the mandrels and are formed of swellable material, and each packer element having an outer diameter.

In an embodiment, the multiple mandrel swellable packer of FIG. 13 has the same OD and same material.

In an embodiment, the multiple mandrel swellable packer of FIG. 13 has the same OD and a different material (faster swelling in center, slower swelling in ends)

In an embodiment, the multiple mandrel swellable packer of FIG. 13 has a different OD (larger OD in center, smaller OD in ends) and the same material

In an embodiment, the multiple mandrel swellable packer of FIG. 13 has a different OD (larger or smaller OD in center) and a different material (faster or slower swelling in center). The final goals of these combinations are to make the swelling even in order to evenly set onto the well bore from the ends to the center of the packer.

FIG. 13 shows a possible connection for FIG. 12. FIG. 13 is found in U.S. Pat. No. 3,487,442, directed to flexible thread systems for high pressure vessels and the like. Referring to FIG. 13, the connection elements are screw type closure structures, a male threaded member and a female threaded member are screwed into a complementary threaded engagement. A gullet is set below the normal root portion of at least one of the two mating threads, the flank of at least one of said mating threads being crowned. The connections are designed for high bending flexibility and are manufactured to prevent unwanted back-off failures. Stress reliefs in the packer minimize bending loads on the break point allowing high flexibility.

FIG. 14 shows a multi-mandrel swellable packer in an embodiment with flexible joints which was applied on a drilling tool made by TTS Drilling Solutions who stated “Safety Joints are designed for high bending flexibility. They are manufactured with a proprietary thread designed to prevent unwanted back-off failures. Stress reliefs in the tools minimize bending loads on the break point allowing high flexibility.” Available at http://www.ttsdrilling.com/Products-Solutions/Safety-Joints.aspx. Referring to FIG. 14, the packer comprises multiple mandrels having the same inner diameter, connection elements coupled to the mandrels which can connect adjacent mandrels, packer elements that fit circumferentially around the mandrels and are formed of swellable material, and each packer element having an outer diameter.

FIG. 15 shows multi-stage fracturing using a multi-mandrel swellable packer.

In an embodiment, packer elements of a multiple mandrel swellable packer have the same outer diameter and are made of the same material. Those skilled in the art will appreciate that other embodiments may also be suitable. For example, they can have the same outer diameter and different materials, such as the swelling speed of the center packer element is faster than that of the end packer element. As an alternative, they can have the same material and different outer diameters, but the outer diameter of the center packer element is larger than that of the end packer element. In yet another embodiment, the packer elements can have different outer diameters and can be made of different materials. There can be larger or smaller outer diameter in center, and there can be faster or slower swelling speed material in center.

The multiple mandrel swellable packer makes it possible for flexible selection of section amounts based on requirements from the wellbore. The specially designed connection can provide sufficient tension/compression as well as sealing capability.

In an embodiment of the manufacturing process, each section is vulcanized individually. Each section can have the same or different rubber materials, and the same or different ODs. They are connected later when needed.

In an embodiment, there is a multi-mandrel with specially designed connection with sealing capability. In an embodiment, there is flexible selection of section amounts based on requirements from the wellbore. In an embodiment, there is a specially designed connection to provide sufficient tension/compression as well as sealing capacity. In an embodiment in the manufacturing process, each section is vulcanized individually. Each section can have the same or different rubber materials and the same or different ODs. They are connected later when needed.

Conventional swellable packers for fracturing are normally lengthy, which causes difficulty or risk during run-in-hole. Using multi-mandrel design, the properly selected length will be determined on-site to meet the specific wellbore requirement (referring to FIGS. 12 and 14). It can possibly save the length of rubber, and save the difficulty or risk during run-in-hole. Specially designed connections can be tubing joints or modified ball bearing connections, or the like. With more connections, the overall packer increases the flexibility and reduces the risk of run-in-hole.

EXAMPLES

Example 1

A large amount of rubber materials and ODs will be tested. Material selection will be carefully conducted.

Example 2

The design of the special connection will be easily assembled in the field and needs sealing capability.

All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this disclosure have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and methods and in the steps or in the sequence of steps of the methods described herein without departing from the concept, spirit and scope of the disclosure. More specifically, it will be apparent that certain agents which are both chemically related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the disclosure as defined by the appended claims.

Claims

1. A packer comprising: a mandrel; anda plurality of packer elements mounted on the mandrel;wherein the packer elements comprise end elements and a central element arranged between the end elements;wherein the packer elements are formed of swellable material that swells when contacted with a swelling fluid.

2. The packer of claim 1, wherein the outer diameter of the central element is different than that of the end elements.

3. The packer of claim 2, wherein the outer diameter of the central element is larger than that of the end elements.

4. The packer of claim 1, wherein the outer diameters of the central element and end elements are increased gradually along the direction from ends to the center of the mandrel.

5. The packer of claim 1, wherein the packer elements abut each other.

6. The packer of claim 5, wherein gaps exist between the packer elements.

7. The packer of claim 3, wherein the central element and end elements are formed of a unitary packer member.

8. A packer comprising: a plurality of mandrels having the same inner diameter;a plurality of connection elements coupled to the plurality of mandrels;a plurality of packer elements that circumferentially fit over the mandrels, wherein the plurality of packer element each have an outer diameter; andwherein the packer elements are formed of a swellable material.

9. The packer of claim 8 wherein the plurality of connection elements can connect adjacent mandrels in the plurality of mandrels.

10. The packer of claim 8, wherein the connection elements are flexible connections.

11. The packer of claim 9, wherein the connection elements are screw type closure structures.

12. The packer of claim 11 wherein the screw type closure structure comprises a male threaded member;a female threaded member;wherein the male threaded member and the female threaded member are screwed into a complementary threaded engagement.

13. The packer of claim 12 wherein a gullet is set below the normal root portion of at least one of two mating threads and wherein a flank of at least one of the mating threads is crowned.

14. The packer of claim 8 wherein when the mandrels connect with each other to form a multi-mandrel packer wherein the outer diameter of the center packer element is different the outer diameter of the end packer element.

15. The packer of claim 14, wherein the outer diameter of the central packer element is larger than the outer diameter of the end packer element.

16. The packer of claim 8, wherein when the mandrels connect with each other to form a multi-mandrel packer wherein the swellable materials of the packer elements have different swelling speeds.

17. The packer of claim 16, wherein the swelling speed of the center packer element is faster than the swelling speed of the end packer element.

18. A method of manufacturing the packer of claim 3 comprising vulcanizing different materials on a mandrel to form packer elements; andmachining the packer elements to form different outer diameters.