WO2019187622A1

WO2019187622A1 - Downhole plug comprising protection member

Info

Publication number: WO2019187622A1
Application number: PCT/JP2019/003604
Authority: WO
Inventors: 輝明吉井
Original assignee: 株式会社クレハ
Priority date: 2018-03-30
Filing date: 2019-02-01
Publication date: 2019-10-03
Also published as: US20210108482A1; CA3094937A1; CN111801484A; CN111801484B; JP2019178569A; CA3094937C; GB2587124A; GB202016485D0; GB2587124B

Abstract

Provided is a plug with excellent pressure resistance. A downhole plug (20) comprises a mandrel (1), a center element (2), at least one lip (3), and a pressure transmission means. The ratio (b/a) of the length (b) in the axial direction of the portion where the mandrel (1) and the center element (2) are in contact to the maximum length (a) in the axial direction of the center element (2) in a cross section taken along the axial direction in a state where the center element (2) is deformed as a result of a pressure of 50 MPa being applied to the downhole plug (20) in the axial direction is less than 0.5.

Description

Downhole plug with protective member

The present invention relates to a plug, and more particularly to a downhole plug used for closing a well hole.

In order to mine shale oil or shale gas, various tools called downhole tools have been developed. As one type of these downhole tools, a downhole plug such as a bridge plug or a flack plug is known (for example, Patent Document 1). One function of this downhole plug is to close the wellbore during hydraulic fracturing.

As a method of hydraulic fracturing, for example, a downhole plug is sent to a predetermined position of a well hole, and the downhole plug is operated and fixed to a well wall, while an elastic member included in the downhole plug is deformed, Close the well. After that, water is pumped from the ground into the well, and the water pressure is applied to the part closer to the ground than the downhole plug fixed to the well wall. The method of producing is mentioned.

Therefore, the downhole plug is required to withstand high water pressure from the ground and to maintain the wellhole blockage while being fixed to the well wall. On the other hand, Patent Document 2 describes a downhole tool using a polymer composite material containing fibers in order to improve the water pressure resistance.

US Patent No. 2017/234103 US 2010/288488

However, when high pressure is applied after the downhole plug elastic member is deformed to close the wellbore, the unintentional deformation of the elastic member causes damage to other parts that make up the downhole plug. There is a problem that the pressure resistance of the hole plug is lowered.

Therefore, an object of the present invention is to provide a downhole plug excellent in pressure resistance.

In order to solve the above problems, the present invention is a plug for closing a well hole,
A tubular body;
An annular elastic member that surrounds the outer peripheral surface of the cylindrical body and deforms under pressure;
At least one protective member that surrounds the outer peripheral surface of the cylindrical main body and prevents at least a part of the elastic member from coming into contact with the cylindrical main body;
A pair of pressure transmitting means for sandwiching the elastic member in the axial direction of the plug and compressing the elastic member by applying pressure in the axial direction to the elastic member;
The cylinder with respect to the maximum axial length (а) of the elastic member in a cross section along the axial direction when the elastic member is deformed by applying a pressure of 50 MPa to the plug in the axial direction. The plug is characterized in that the ratio (b / а) of the length (b) in the axial direction of the portion where the main body contacts the elastic member is less than 0.5.

According to the present invention, a downhole plug excellent in pressure resistance can be provided.

It is the schematic of the cross section of a downhole plug when it exists in the predetermined position in a well based on Embodiment 1 of this invention. It is the schematic of the cross section of a downhole plug when receiving the hydraulic pressure by the well hole based on Embodiment 1 of this invention. It is the schematic diagram which expanded a part of cross section of the downhole plug when receiving the hydraulic pressure by the wellbore according to Embodiment 1 of the present invention. It is the schematic of the cross section of a downhole plug when it exists in the predetermined position in a well based on Embodiment 2 of this invention. It is the schematic of the cross section of a downhole plug when receiving the hydraulic pressure by the well hole based on Embodiment 2 of this invention. It is the schematic diagram which expanded a part of cross section of the downhaul plug when it exists in the predetermined position in a well based on Embodiment 3 of this invention. It is the schematic diagram which expanded a part of cross section of the downhole plug when receiving the hydraulic pressure by the well hole based on Embodiment 3 of this invention. It is the schematic diagram which expanded a part of cross section of the downhole plug when it exists in the predetermined position in a wellbottle based on Embodiment 4 of this invention. It is the schematic diagram which expanded a part of cross section of the downhole plug when receiving the hydraulic pressure by the well hole based on Embodiment 4 of this invention. It is the schematic which showed a part of cross section of the lip based on Embodiment 5 of this invention.

Embodiment 1
The downhole plug (plug) according to Embodiment 1 of the present invention is a plug for closing a wellbore. The downhole plug according to the first embodiment includes a first form that is a form when the downhole plug is sent from the ground to a predetermined position of the wellbore, and a second form in which the downhole plug is operated and fixed to the well. And a third configuration when the downhole plug is under water pressure. The first form corresponds to FIG. 1, and the third form corresponds to FIG. The second form is not shown. FIG. 1 is a schematic view of a cross-section of a downhole plug in a first form at a predetermined position in a well according to the first embodiment. FIG. 2 is a schematic view of a cross-section of the downhole plug in the third embodiment in a state of being subjected to water pressure according to the first embodiment. In FIG. 1 and FIG. 2, only one of the cross sections of the downhole plug that is symmetric with respect to the axis (one-dot chain line in the figure) is shown.

Hereinafter, the downhole plug according to the first embodiment will be described in detail with reference to FIGS. 1 and 2.

1. 1st form of a downhole plug The 1st form of a downhole plug is demonstrated using FIG. FIG. 1 shows a state where there is a gap between the well wall and the downhole plug in the well.

As shown in FIG. 1, the downhole plug 20 includes a mandrel (cylindrical main body) 1, a center element (elastic member) 2, a lip (protective member) 3, sockets (pressure transmitting means) 4a and 4b, a cone (Pressure transmission means) 5a and 5b and slips (pressure transmission means) 6a and 6b are provided. The downhole plug 20 further includes equalizer rings (pressure transmission means) 7 a and 7 b, a load ring (pressure transmission means) 8, and a bottom 9. The downhole plug 20 has a cylindrical shape as a whole. In the following description, “axis” or “axial direction” simply refers to the axis or axial direction of the downhole plug 20 that is cylindrical as a whole.

Hereinafter, each member will be described in detail.

[Mandrel]
The mandrel 1 is a member for ensuring the strength of the downhole plug 20 and is a hollow member that exists along the axis at the center of the downhole plug 20. Various members for constituting the downhole plug 20 are attached to the outer peripheral surface of the mandrel 1 as a whole.

Examples of the material forming the mandrel 1 include metal materials such as aluminum, steel, and stainless steel, fibers, wood, composite materials, and resins. The mandrel 1 may be formed of a composite material containing a reinforcing material such as carbon fiber, specifically, a composite material containing a polymer such as an epoxy resin and a phenol resin, for example.

Of these, the mandrel 1 is preferably formed of a decomposable resin or a degradable metal. Thereby, after performing a well treatment using the downhole plug 20, the removal of the downhole plug 20 becomes easy.

In the present specification, the term “degradable resin or degradable metal” refers to biodegradation or hydrolysis, dissolved in water or hydrocarbons in wells, and further decomposed or embrittled by some chemical method. It means a resin or metal that can be disintegrated.

Examples of the decomposable resin include hydroxycarboxylic acid-based aliphatic polyesters such as polylactic acid (PLA) and polyglycolic acid (PGA), lactone-based aliphatic polyesters such as poly-caprolactone (PCL), polyethylene succinate, and polybutylene. Diol / dicarboxylic acid aliphatic polyester such as succinate, copolymers of these, for example, glycolic acid / lactic acid copolymer, and mixtures thereof, as well as combinations of aromatic components such as polyethylene adipate / terephthalate And aliphatic polyester.

Examples of the water-soluble resin include polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, polyacrylamide (may be N- and N-substituted products), polyacrylic acid, and polymethacrylic acid. Monomers that form these resins Examples of such copolymers include ethylene-vinyl alcohol copolymer (EVOH) and acrylamide-acrylic acid-methacrylic acid interpolymers.

Examples of the decomposable metal include alloys containing magnesium, aluminum, calcium and the like as main components.

[Center element]
The center element 2 is an annular rubber member for filling the gap between the mandrel 1 and the well wall in the downhole plug 20 and closing the well hole, and is deformed by receiving pressure. The center element 2 is attached so as to surround the outer peripheral surface of the mandrel 1.

The thickness, elasticity, inner diameter, outer diameter, or axial width of the center element 2 may be appropriately determined according to the size of the mandrel 1 or the pressure applied to the downhole plug 20.

The center element 2 is preferably formed of a material that does not lose the function of closing the wellbore even under high temperature and high pressure environments such as 100 ° C. and 30 MPa. Preferable materials for forming the center element 2 include, for example, nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluorine rubber. Also, degradable rubbers such as aliphatic polyester rubber, polyurethane rubber, natural rubber, polyisoprene, acrylic rubber, aliphatic polyester rubber, polyester thermoplastic elastomer, and polyamide thermoplastic elastomer can be used.

[lip]
The lip 3 is a member that prevents the mandrel 1 from being damaged by preventing at least a part of the center element 2 from coming into contact with the mandrel 1 when the downhole plug 20 is used to close the wellbore. In the first embodiment, the lip 3 is inserted between the mandrel 1 and the center element 2, thereby preventing at least a part of the center element 2 from coming into contact with the mandrel 1. The lip 3 only needs to be inserted at least partially between the mandrel 1 and the center element 2 when pressure is applied to the downhole plug 20.

Although details will be described later, when the downhole plug 20 receives water pressure and the center element 2 is compressed, force is applied from the center element 2 to the mandrel 1. In the third form after being deformed by water pressure, the portion where the center element 2 is in contact with the mandrel 1 is reduced by the lip 3, so that the force received by the mandrel 1 from the center element 2 can be reduced. Thereby, it can prevent that the mandrel 1 is damaged. By preventing the mandrel 1 from being damaged by the lip 3, a downhole plug having excellent pressure resistance can be provided.

As described above, the mandrel 1 is a member for ensuring the strength of the downhole plug 20. However, depending on the material or thickness of the mandrel 1, the strength of the mandrel 1 is less than the force received from the center element 2. May not be enough. The material forming the mandrel 1 is as described in the section of [Mandrel]. Generally, the resin material has a lower strength than the metal material, and the non-composite material containing no reinforcing material is the strength of the resin material. Is low. Thus, even if the strength of the mandrel 1 is not sufficient, the pressure resistance of the downhole plug 20 is ensured because the downhole plug 20 includes the lip 3.

The lip 3 according to the first embodiment is an annular member attached so as to surround the outer peripheral surface of the mandrel 1, and is integrated with a cone 5a described later. That is, the lip 3 is provided as a part of the cone 5a. Specifically, the inner peripheral edge of the cone 5 a that contacts the mandrel 1 protrudes toward the center element 2, and the entire inner peripheral surface of the cone 5 a including the protruding portion contacts the mandrel 1. This protruding portion is a portion corresponding to the lip 3. The inner peripheral edge of the cone 5 a that contacts the mandrel 1 protrudes toward the center element 2 in contact with the mandrel 1, thereby preventing a part of the center element 2 from contacting the mandrel 1.

The length of the lip 3 is designed based on a third form to be described later.

The thickness of the lip 3 is not particularly limited as long as it does not prevent the lip 3 from moving between the center element 2 and the mandrel 1 when the cone 5a moves to the center element 2 side under pressure. Good. Further, the thickness may be constant, or the thickness may be changed so as to decrease toward the tip of the lip 3 that is the protruding portion. Alternatively, the lip 3 may be designed so that the thickness is constant on the side close to the cone 5a and the thickness is reduced toward the tip on the side close to the tip.

The material of the lip 3 is not particularly limited, and materials described as materials for forming the mandrel 1 described above can be used. Among these, for the same reason as the mandrel 1, it is preferably formed of a degradable resin or a degradable metal.

[Pressure transmission means]
The pressure transmission elements constituting the pressure transmission means include

sockets

4a and 4b,

cones

5a and 5b, slips 6a and 6b, equalizer rings 7a and 7b, and load ring 8.

(socket)
The

sockets

4a and 4b are arbitrary members constituting pressure transmission means, and receive deformation of the center element 2 when the center element 2 is deformed by receiving the axial pressure of the downhole plug 20 in the well.

Sockets

4 a and 4 b are annular members surrounding the outer peripheral surface of the mandrel 1. The

sockets

4a and 4b are attached adjacent to one end of the center element 2, and the socket 4a and the socket 4b are in contact with each other. The socket 4b is attached in contact with the mandrel 1, whereas the socket 4a is not in contact with the mandrel 1. That is, the outer diameters of the

sockets

4a and 4b are equal, while the inner diameter of the socket 4a is larger. The socket 4a is movably attached to the socket 4b.

The material of the socket is not particularly limited, and materials described as materials for forming the mandrel 1 described above can be used. Among these, for the same reason as the mandrel 1, it is preferably formed of a degradable resin or a degradable metal. The socket 4a is preferably made of a material that can be deformed so that its diameter expands when subjected to pressure.

(corn)
The

cones

5a and 5b are members constituting pressure transmission means, and transmit pressure directly and indirectly to the center element 2, respectively.

The

cones

5 a and 5 b are attached so as to surround the outer peripheral surface of the mandrel 1. The cone 5a is attached adjacent to the end of the center element 2 opposite to the end where the

sockets

4a and 4b are in contact. On the other hand, the cone 5 b is attached to the opposite side of the center element 2 adjacent to the

sockets

4 a and 4 b on the outer peripheral surface of the mandrel 1. That is, the

sockets

4 a and 4 b are interposed between the cone 5 b and the center element 2.

The cone 5a is a hollow conical member. In the present specification, the term “conical shape” refers to a cone, a truncated cone, or a combination of a cylinder and these. Moreover, a hollow shape is a shape which follows the outer peripheral surface of a mandrel, and is a cylindrical shape normally.

As described above, in this embodiment, the lip 3 is provided integrally with the cone 5a. Accordingly, the cone 5a is a hollow having a diameter smaller than the maximum diameter of the conical solid on the side of the center element 2 in the hollow conical solid whose outer diameter increases from the end of the mandrel 1 toward the center element 2. The shape is made by joining the cylinders.

On the other hand, the cone 5b is a hollow conical member having a shape in which the outer diameter increases from the end of the mandrel 1 toward the center element 2.

The material of the cone is not particularly limited, and materials described as materials for forming the mandrel 1 described above can be used. Among these, for the same reason as the mandrel 1, it is preferably formed of a decomposable resin or a decomposable metal.

(slip)
The

slips

6 a and 6 b are members constituting pressure transmission means, and indirectly transmit pressure to the center element 2. The

slips

6a and 6b are attached so as to surround the outer peripheral surface of the mandrel 1, and are in contact with the

cones

5a and 5b, respectively.

The

slips

6a and 6b are annular members whose inner diameters decrease from the center element 2 side toward the end of the mandrel 1, respectively.

The material of the slip is not particularly limited, and materials described as materials for forming the mandrel 1 described above can be used. Among these, for the same reason as the mandrel 1, it is preferably formed of a decomposable resin or a decomposable metal.

(Equalizer ring)
The equalizer rings 7a and 7b are arbitrary members constituting the pressure transmission means, and slip 6a during the transition from the first form to the second form and from the second form to the third form, which will be described later. In addition to having a function of uniformly expanding the diameters of 6b and 6b, pressure is indirectly transmitted to the center element 2. The equalizer rings 7a and 7b are attached so as to surround the outer peripheral surface of the mandrel 1, and are in contact with the

slips

6a and 6b, respectively.

The material of the equalizer ring is not particularly limited, and materials described as materials for forming the mandrel 1 can be used. Among these, for the same reason as the mandrel 1, it is preferably formed of a degradable resin or a degradable metal.

(Road ring)
The load ring 8 is a member that constitutes a pressure transmission means, and receives pressure applied from the wellhead side directly and transmits the pressure to the adjacent member, thereby indirectly transmitting the pressure to the center element 2. The load ring 8 is attached so as to surround the outer peripheral surface of the mandrel 1, and is in contact with the equalizer ring 7a.

The material of the load ring is not particularly limited, and materials described as materials for forming the mandrel 1 described above can be used. Among these, for the same reason as the mandrel 1, it is preferably formed of a degradable resin or a degradable metal.

In the present specification, the term “a pair of pressure transmission means” does not mean that the two pressure transmission means provided so as to sandwich the center element 2 have the same configuration. That is, as long as each functions as a pressure transmission unit, the configuration included in each pressure transmission unit may be different. Usually, since the water pressure is received from only one of the plugs, one pressure transmission means transmits pressure to the center element 2, and the other pressure transmission means plays a role of receiving the center element 2. In this specification, it expresses as a pressure transmission means including such a role.

[Other parts]
In addition to the above-described members, the downhole plug 20 may have a bottom 9 or the like as shown in FIG. The bottom 9 is attached so as to surround the outer peripheral surface of the mandrel 1, but the arrangement of the bottom 9 may be appropriately determined as necessary. The material of the bottom 9 is not particularly limited as long as each function can be exhibited, and materials described as materials for forming the mandrel 1 described above can be used. Among these, for the same reason as the mandrel 1, it is preferably formed of a degradable resin or a degradable metal.

2. Second Form of Downhole Plug The second form of the downhole plug is a form in which the downhole plug 20 is operated and fixed to the well.

After the downhole plug 20 is disposed at a predetermined position in the well, by operating the downhole plug 20, the center element 2 is expanded in diameter and brought into contact with the well wall, and the mandrel 1 and the well wall The

slips

6a and 6b are expanded in diameter. When the downhole plug 20 contacts the well wall, the downhole plug 20 is fixed at a predetermined position in the well. Hereinafter, a change from the first form to the second form will be described with reference to FIG. 1 in which the first form is shown.

When the downhole plug 20 is operated in the well, at least one of the pair of pressure transmission means moves in the axial direction of the mandrel 1 toward the center element 2, thereby compressing the center element 2 in the axial direction. The outer diameter of the center element 2 is enlarged. As a result, the outer peripheral surface of the center element 2 is in contact with the well wall 12 and closes the gap between the mandrel 1 and the well wall. As a result, the downhole plug 20 is fixed to the well.

Specifically, when the downhole plug 20 is operated, the

slips

6a and 6b slide on the inclined surfaces of the

cones

5a and 5b, respectively, and the

slips

6a and 6b contact the well wall 12. At the same time, pressure is transmitted to the center element 2 indirectly from the cone 5b and directly from the cone 5a and the

sockets

4a and 5b, and the center element 2 is compressed and deformed.

When the center element 2 is compressed, the center element 2 expands in a direction perpendicular to the axial direction of the mandrel 1 and comes into contact with the well wall 12 so that the downhole plug 20 is fixed to the well. When the center element 2 is deformed by receiving pressure and the center element 2 is pressed against the

sockets

4a and 4b, the socket 4a slides on the inclined surface of the socket 4b due to its diameter expanding. It contacts the wall 12. Thus, the downhole plug 20 becomes a 2nd form.

3. 3rd form of a downhole plug The 3rd form of a downhole plug is a form when the downhole plug 20 is receiving the hydraulic pressure. Hereinafter, a third embodiment of the downhole plug 20 will be described with reference to FIG.

After the downhole plug 20 is fixed at a predetermined position in the well, the flack ball 10 is fed into the well and seated on the ball seat 13 of the downhole plug 20 to close the hollow portion of the mandrel 1. Complete the closure of the hole. Then, water is injected from the wellhead, and water pressure is applied from the wellhead side toward the backside of the wellbore. The downhole plug 20 becomes the 3rd form which the mandrel 1 moved toward the back | inner side of a well hole by receiving a pressure toward the back | inner side of a well hole from the well-hole side.

When water pressure is applied to the downhole plug 20 of the second form from the wellhead side, the mandrel 1 moves according to the water pressure. At this time, the center element 2 may be further compressed by moving the one on the wellhead side of the pair of pressure transmission means toward the back side of the wellhole by the water pressure from the wellhead side. In this way, the downhole plug 20 is in the third form.

In the third embodiment, the cone 5a sandwiching the center element and the socket 4 are closer to each other than in the first embodiment. That is, in the third embodiment, there are fewer portions where the mandrel 1 and the center element 2 are in contact with each other than in the first embodiment. The part where the center element 2 and the mandrel 1 are in contact will be described later.

4). Contact portion between center element and mandrel As described above, the center element 2 is in contact with the mandrel 1, and contact is prevented by the lip 3 at a part thereof. In the third embodiment, the center element 2 is compressed by applying pressure in the axial direction of the downhole plug 20 and reducing the distance between the cone 5a having the lip 3 and the

sockets

4a and 4b. Thereby, in the 3rd form, the field where center element 2 and mandrel 1 contact has changed from the above-mentioned 1st form. The contact portion between the center element 2 and the mandrel 1 in the third embodiment will be described in detail. In the third embodiment of the downhole plug 20, the downhole plug is about the cross section along the axial direction of the downhole plug 20. 20, the total length (b) of the portion where the mandrel 1 and the center element 2 are in contact with the maximum axial length (a) of the center element 2 when a pressure of 50 MPa is applied in the axial direction. ) Ratio (b / a) is less than 0.5.

Here, “when a pressure of 50 MPa is applied in the axial direction” is intended to apply pressure from one side of the downhole plug 20 in the axial direction toward the other side. This assumes that when water is injected from the wellhead, pressure is applied from the wellhole side of the downhole plug 20 toward the backside of the well.

Here, the “maximum length (a) in the axial direction of the center element 2” is the width in the axial direction of the center element 2 in the cross section along the axial direction of the downhole plug 20, as shown in FIG. is there. That is, the axial length of the downhole plug 20 in the orthogonal projection of the center element 2 onto the mandrel 1 or the well wall 12. In addition, although a specific example is demonstrated in below-mentioned Embodiment 4, when there are multiple center elements 2, let the sum total of the length of each axial direction of these several parts be (a).

Further, “the length (b) of the shaft portion where the mandrel 1 and the center element 2 are in contact with each other” refers to the mandrel 1 and the center in the cross section along the axial direction of the downhole plug 20 as shown in FIG. This is the length in the axial direction of the portion in contact with the element 2. When the length of the portion where the center element 2 is in contact with the outer periphery of the mandrel 1 is not constant, the average value is used as (b). Although a specific example will be described in Embodiment 3 described later, when there are a plurality of portions where the mandrel 1 and the center element 2 are in contact with each other in a certain cross section, the axial directions of these portions are respectively Let the total length be (b).

As described above, the ratio of (b) to (a) is less than 0.5, but this ratio is preferably as small as possible. For example, it is preferably less than 0.25, more preferably less than 0.1. , 0 is most preferred. The ratio of (b) to (a) is 0, that is, (b) = 0.

The smaller the ratio of (b) to (a), that is, the smaller the portion where the mandrel 1 and the center element 2 are in contact with each other in the third embodiment, the force applied to the mandrel 1 from the center element 2, that is, the mandrel 1 The force which tightens can be reduced, and breakage of the mandrel 1 can be prevented more effectively. Further, when the center element 2 is compressed and deformed, it is presumed that the deformation becomes the largest and the force applied to the mandrel 1 becomes the strongest in the vicinity of the axial center portion of the center element 2. If the ratio (b / a) is less than 0.5, the lip 3 is present at the central portion of the axial length of the center element 2. Therefore, the contact between the center element 2 and the mandrel 1 can be prevented at the portion where the force applied to the mandrel 1 is largest, and the mandrel 1 can be more reliably prevented from being damaged.

The pressure applied to the downhole plug in the well when performing hydraulic crushing is usually about 30 to 70 MPa. Therefore, if the ratio (b / a) when a pressure of 50 MPa is applied to the downhole plug 20 is less than 0.5, the ratio (b / a) will be less than 0.5 even in the actual use environment. Can be realized. Therefore, the excellent pressure resistance of the downhole plug 20 according to the first embodiment is exhibited in an actual use environment.

(Modification)
A modification of the first embodiment will be described. In the downhole plug 20 described above, also in the third embodiment, the center element 2 and the mandrel 1 are in contact with each other with a predetermined length (that is, b> 0). However, by making the axial length of the lip 3 longer, in the third embodiment, the contact of the center element 2 with the mandrel 1 is completely blocked by the lip 3, that is, (b) = 0. It may be a configuration. FIG. 3 shows a configuration when (b) = 0. FIG. 3 is an enlarged schematic view of a part of the cross-section of the downhole plug 20, which is in a state where the water pressure is received in the wellbore, according to a modification of the first embodiment. . As shown in FIG. 3, in the third embodiment of the downhole plug 20 as a modification, the tip of the lip 3 extending from the cone 5 a reaches the socket 4 and is in contact with the socket 4. As a result, the lip 3 enters the entire inner peripheral surface of the center element 2 that has been in contact with the mandrel 1 in the first embodiment. Therefore, the contact of the center element 2 with the mandrel 1 is completely blocked by the lip 3, and there is no shaft portion where the mandrel 1 and the center element 2 are in contact (that is, (b) = 0). Thereby, the force applied from the center element 2 to the mandrel 1 is further reduced, and the breakage of the mandrel 1 can be prevented more reliably.

Furthermore, when (b) = 0, since the tip of the lip 3 has reached the socket 4, the lip 3 also functions as a stiff stick. Therefore, the center element 2 can be prevented from being deformed excessively, and the pressure resistance in the axial direction is improved.

For the following embodiments, members having the same functions as those described in [Embodiment 1] are described with the same reference numerals for convenience of description, and the description thereof will not be repeated.

[Embodiment 2]
A downhole plug according to Embodiment 2 of the present invention will be described with reference to FIGS. The first form of the downhole plug corresponds to FIG. 4, and the third form corresponds to FIG. FIG. 4 is a schematic view of a cross-section of the downhole plug when in a predetermined position in the well according to the second embodiment. FIG. 5 is a schematic view of a cross-section of a downhole plug when subjected to water pressure at a wellbore according to Embodiment 2 of the present invention. 4 and 5, only one of the cross-sections of the downhole plug 21 that is symmetrical with respect to the axis (one-dot chain line in the figure) is shown.

In the downhole plug 21 according to the second embodiment, as shown in FIGS. 4 and 5, the lip 3 is not an integral part of the cone 5a, but is an annular member that exists separately from the cone 5a. Although the lip 3 and the cone 5a are separate bodies, they are provided on the outer peripheral surface of the mandrel 1 so that they are in contact with each other. Specifically, the lip 3 is located on the side in contact with the center element 2 of the cone 5a, and is in contact with the inner peripheral edge of the cone 5a. The inner diameter of the lip 3a is the same as the inner diameter of the cone 5a, and the outer diameter of the lip 3 is smaller than the outer diameter of the cone 5a. Accordingly, in the second embodiment, as in the first embodiment, the contact between the center element 2 and the mandrel 1 is prevented by the lip 3 in the cone 5a of the center element 2. Since the lip 3 is in contact with the cone 5a, when the cone 5a moves in the direction of the center element 2, the lip 3 is also pushed and moved.

It is sufficient that the lip 3 and the cone 5a are in contact with each other, and they may not be fixed with each other or may be fixed.

The boundary between the lip 3 and the cone 5a is not particularly limited. For example, as shown in FIGS. 4 and 5, in the cross-section of the downhole plug 21, a perpendicular line extending from the end of the center element 2 in contact with the cone 5a to the mandrel 1 is used. It may be.

[Embodiment 3]
A downhole plug according to Embodiment 3 of the present invention will be described with reference to FIGS. 6 and 7. The first form of the downhole plug corresponds to FIG. 6, and the third form corresponds to FIG.

FIG. 6 is an enlarged schematic view of a part of the cross-section of the downhole plug when in a predetermined position in the well according to the third embodiment. In the description using FIG. 6 and FIG. 7, it is not necessary to distinguish between the socket 4 a and the socket 4 b, so that they are collectively illustrated as the socket 4, and are also referred to as the socket 4 hereinafter.

When the pressure of 50 MPa is applied to the downhole plug, the lip 3 may be (b / a) less than 0.5, and its position is not particularly limited.

Specifically, as shown in FIG. 6A, the lip 3 may be integrated with the socket 4 instead of being integrated with the cone 5a.

Further, the lip 3 may be divided into two as shown in FIGS. 6B and 6B, and may be integrally formed with the socket 4 and the cone 5a. As for the lip 3 divided into two, the lip 3 integrated with the socket 4 may be longer, the lip 3 integrated with the cone 5a may be longer, or the same length There may be.

As shown in FIG. 6C, the lip 3 may be independent from both the socket 4 and the cone 5a and may not be in contact with either the socket 4 or the cone 5a. At this time, the lip 3 may be one or plural.

Furthermore, the lip 3 may be a combination of any of the forms described above.

FIG. 7 is an enlarged schematic view of a part of the cross-section of the downhole plug when the water pressure is received in the wellbore according to the third embodiment of the present invention.

As described above, when the pressure of 50 MPa is applied to the downhole plug, if the ratio of (b) to (a) shown in FIG. Not limited. In FIG. 7, (b / a) is larger than 0 in any case, but preferably (b) = 0 shown in FIG. 3.

As shown in FIG. 7 (c), when there are a plurality of portions where the mandrel 1 and the center element 2 are in contact, the axial lengths (b1) and (b2) of the plurality of portions respectively. Let the total be (b).

When at least one of the lips 3 described in [Embodiment 3] is integrated with the socket 4 or the cone 5a, as described in [Embodiment 2], the lip 3 is connected to the socket 4 or the cone 5a. The aspect which is contacting, independently from may be sufficient.

[Embodiment 4]
A downhole plug according to Embodiment 4 of the present invention will be described with reference to FIGS. The first form of the downhole plug corresponds to FIG. 8, and the third form corresponds to FIG.

The downhole plug according to the present invention, when (b / a) is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug, as shown in FIG. The center element 2 may be divided into a plurality and arranged along the axis of the mandrel 1. In addition, (a) is the sum total of the maximum length of a some center element.

At this time, the thickness, elasticity, inner diameter, outer diameter, or axial width of the plurality of center elements may be the same or different. However, from the viewpoint of preventing the mandrel from being damaged, in each of the plurality of center elements, the length of the portion where the mandrel and the center element are in contact is preferably smaller than the maximum length of each center element.

As shown in FIG. 8B, a partition 11 may be provided between the plurality of center elements. The partition 11 is not particularly limited as long as it is an annular member surrounding the mandrel 1, but may be a part or all of the pressure transmission means described above. Although the material of the partition 11 is not particularly limited, it is preferably formed of a decomposable resin or a decomposable metal from the viewpoint that it is easy to remove the downhole plug 20 after the well treatment.

FIG. 9 is an enlarged schematic view of a part of the cross-section of the downhole plug when receiving water pressure at the wellbore according to Embodiment 4 of the present invention.

As described above, when a pressure of 50 MPa is applied to the downhole plug, if the ratio of (b) to (a) shown in FIG. May or may not have a partition 11. FIG. 9 shows a form in which (b / a) is larger than 0, but preferably (b) = 0 shown in FIG.

Note that (a) when there are a plurality of center elements is the sum of the maximum lengths (a1) and (a2) in the axial direction of these center elements (a) as shown in FIG. ).

[Embodiment 5]
The lip 3 is attached so as to surround the outer peripheral surface of the mandrel 1, but the shape may not be annular. That is, when (b / a) is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug, the lip 3 may be divided into two or more on the outer periphery of the mandrel 1.

This will be described with reference to FIG. (A), (b), and (c) of FIG. 10 represent cross sections when cut in a direction perpendicular to the axis of the lip 3, and (a ′), (b ′), and (c ′) of FIG. ) Represents a side view along the axial direction of the lip.

(A), (a '), (b) and (b') in Fig. 10 show a lip 3 composed of two members, lips 3a and 3b. (C) and (c ′) of FIG. 10 show a lip 3 composed of three members,

lips

3a, 3b and 3c. In FIG. 10C ', the lip 3c has an annular shape, but it may be divided into two or more on the outer periphery of the mandrel 1 like the

lips

3a and 3b.

Moreover, each divided lip may be integrated with the socket or the cone, or may be independent.

Furthermore, as shown in FIG. 10 (b), the angle of the dividing surface of the lip 3 is not limited, and may not necessarily be parallel to the mandrel axis. In addition, since the length of the part which the center element 2 is contacting in the outer periphery of the mandrel 1 is not constant, the downhole plug provided with the lip | rip 3 of Embodiment 5 uses the average value as (b).

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

[Summary]
The plug for closing the well hole includes at least a cylindrical main body, an annular elastic member surrounding the outer peripheral surface of the cylindrical main body, deformed by pressure, and an elastic member surrounding the outer peripheral surface of the cylindrical main body. A pair of pressure transmission means for compressing the elastic member by applying axial pressure to the elastic member by sandwiching the elastic member in the axial direction of the plug and at least one protective member that prevents a part from contacting the cylindrical body And having a cylindrical shape with respect to the maximum axial length (а) of the elastic member in a cross section along the axial direction when the elastic member is deformed by applying a pressure of 50 MPa to the plug in the axial direction. The ratio (b / а) of the length (b) in the axial direction of the portion where the main body and the elastic member are in contact is less than 0.5.

According to this configuration, when pressure is received from one side in the axial direction of the plug, it is also provided on the outer peripheral surface of the cylindrical main body via the pair of pressure transmission means provided on the outer peripheral surface of the cylindrical main body. The elastic member sandwiched between the pair of pressure transmission means is compressed and deformed. At that time, at least a part of the elastic member is prevented from coming into contact with the cylindrical main body by the protective member similarly provided on the outer peripheral surface of the cylindrical main body. Specifically, when the elastic member is deformed by applying a pressure of 50 MPa in the axial direction, the cylindrical main body and the elasticity with respect to the maximum axial length (а) of the elastic member in the cross section along the axial direction. The ratio (b / а) of the length (b) in the axial direction of the portion in contact with the member is less than 0.5. When the elastic member is compressed and deformed, a force is applied from the elastic member to the cylindrical main body, but the force applied to the cylindrical main body when the portion where the elastic member and the cylindrical main body are in contact with each other is within the above range. Less. As a result, damage to the cylindrical main body can be prevented, and the plug has excellent pressure resistance.

Further, at least one of the protective members may be integrated with one of the pressure transmission elements constituting the pressure transmission means.

Also, at least one of the protection members may be independent from the pressure transmission means.

In addition, a plurality of protection members are provided, and one of the plurality of protection members is integrated with one of the pressure transmission elements constituting one of the pair of pressure transmission means. May be integrated with one of the pressure transmission elements constituting the other of the pair of pressure transmission means.

One of the pressure transmission elements integrated with the protective member is a pair of conical members that are in contact with the end of the elastic member and whose outer diameter increases from the end of the cylindrical main body toward the elastic member side. It may be.

Further, the protective member may be annular. According to this structure, it can prevent more effectively that the cylindrical main body of a plug contacts an elastic member. Therefore, the plug has excellent pressure resistance.

Also, the length (b) may be zero. According to this configuration, since the cylindrical main body of the plug does not contact the elastic member, the plug is further excellent in pressure resistance.

An embodiment of the present invention will be described below. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail.

[Example 1]
When the center element is deformed by applying a pressure of 50 MPa in the axial direction of the downhole plug, the mandrel and the center element are in contact with the maximum length (a) in the axial direction of the center element in the cross section along the axial direction. A water pressure resistance test was performed on a downhole plug in which the ratio (b / a) of the length (b) in the axial direction of the portion in which it is located is zero.

The above-mentioned down hole plug was put in a metal cylinder whose inner diameter was 1.1 times the outer diameter of the down hole plug so that the axes of the down hole plug and the cylinder were parallel. The inside of the cylinder was kept at 90 ° C., and the cylinder was closed by applying a water pressure of 60 to 63 MPa to the axial direction of the downhole plug. Then, the time during which the cylinder was kept closed was measured.

The results are shown in Table 1.

[Comparative Example 1]
Using a downhole tool in which the axial length (a) of the center element in the cross section along the axial direction is equal to the axial length (b) of the portion where the mandrel and the center element are in contact with each other, Was the same as in Example 1 except that the temperature was 90 to 93 ° C. and the water pressure was 50 to 53 MPa.

[Comparative Example 2]
Using a downhole tool in which the axial length (a) of the center element in the cross section along the axial direction is equal to the axial length (b) of the portion where the mandrel and the center element are in contact with each other, The same operation as in Example 1 was performed except that the temperature was 90 to 93 ° C.

1 Mandrel (tubular body)
2 Center element (elastic member)
3, 3a, 3b, 3c Lip (protective member)
4, 4a, 4b Socket (pressure transmission means)
5a, 5b cone (pressure transmission means)
6a, 6b Slip (pressure transmission means)
7a, 7b Ring (pressure transmission means)
8 Load ring (pressure transmission means)
9 Bottom 10 Ball 11 Partition 12 Well wall 13

Ball seat

20, 21 Downhole plug (plug)

Claims

A plug for closing a well hole,
A tubular body;
An annular elastic member that surrounds the outer peripheral surface of the cylindrical body and deforms under pressure;
At least one protective member that surrounds the outer peripheral surface of the cylindrical main body and prevents at least a part of the elastic member from coming into contact with the cylindrical main body;
A pair of pressure transmitting means for sandwiching the elastic member in the axial direction of the plug and compressing the elastic member by applying pressure in the axial direction to the elastic member;
The cylinder with respect to the maximum axial length (а) of the elastic member in a cross section along the axial direction when the elastic member is deformed by applying a pressure of 50 MPa to the plug in the axial direction. A plug characterized in that the ratio (b / а) of the length (b) in the axial direction of the portion where the main body contacts the elastic member is less than 0.5.
2. The plug according to claim 1, wherein at least one of the protective members is integrated with one of the pressure transmission elements constituting the pressure transmission means.
The plug according to claim 1, wherein at least one of the protective members is independent of the pressure transmission means.
A plurality of the protection members are provided, and one of the plurality of protection members is integrated with one of the pressure transmission elements constituting one of the pair of pressure transmission means. 2. The plug according to claim 1, wherein the other one is integrated with one of the pressure transmission elements constituting the other of the pair of pressure transmission means.
One of the pressure transmission elements integrated with the protective member is a conical shape that is in contact with the end of the elastic member and whose outer diameter increases from the end of the cylindrical body toward the elastic member. The plug according to claim 2, wherein the plug is a member.
The plug according to any one of claims 1 to 5, wherein the protective member is annular.
The plug according to any one of claims 1 to 6, wherein the length (b) is zero.