Pumpdown wiper, downhole tool, and method for using pumpdown wiper

Abstract

[Problem] To provide a pumpdown wiper capable of suppressing breakage during transport, a downhole tool including the same, and a method for using the pumpdown wiper. [Solution] In this pumpdown wiper constituting a downhole tool, the downhole tool comprises: a cylindrical mandrel; a sealing member provided around the mandrel; and a fixing member provided around the mandrel for fixing the downhole tool to an inner wall of a casing. The pumpdown wiper is arranged around the mandrel of the downhole tool, and is arranged on at least one of the upstream side and the downstream side, in a transport direction, of the position where the sealing member and the fixing member are provided. The pumpdown wiper contains an elastomer material, and has a surface hardness of A70 or more and A96 or less as measured by a type A durometer at a temperature of 23°C and a humidity of 50 RH%, and a ten-point mean roughness Rzjis of 30 μm or less as measured in accordance with JIS B 0601:2001.

Description

How to use a pump-down wiper, downhole tool, and pump-down wiper.

[0001] The present invention relates to a pump-down wiper used to improve the transportability of a downhole tool, a downhole tool equipped with the same, and a method for using the pump-down wiper.

[0002] Hydrocarbon resources such as petroleum or natural gas are extracted and produced through wells (oil wells or gas wells are collectively referred to as "wells") that have porous and permeable subsurface layers. Equipment used inside wells for well treatment and wellhead sealing is called downhole tools, and examples include flak plugs and bridge plugs.

[0003] The downhole tool is pumped and positioned in the well to the desired depth using a fluid. To improve transportability during the pumping process, downhole tools equipped with a pump-down wiper are used. The pump-down wiper is a component positioned around the mandrel of the downhole tool and is typically made of a flexible rubber material.

[0004] U.S. Patent Application Publication No. 2025 / 0012158

[0005] However, pump-down wipers can rupture when transported through the well by the fluid being pumped, due to insufficient strength against water pressure and contact with the well wall or foreign objects. The rupture of pump-down wipers presents a challenge, as it reduces the transport capacity of the downhole tool.

[0006] This disclosure aims to provide a pump-down wiper capable of suppressing breakage during transport, a downhole tool equipped with the same, and a method of using the pump-down wiper.

[0007] The present disclosure provides: (1) a pump-down wiper constituting a downhole tool, the downhole tool comprising a cylindrical mandrel, a sealing member provided around the mandrel, and a fixing member provided around the mandrel for fixing the downhole tool to the inner wall of a casing, the pump-down wiper being positioned around the mandrel of the downhole tool, and positioned at least one of the upstream or downstream sides in the transport direction from the position where the sealing member and the fixing member are provided, comprising an elastomer material, having a surface hardness of A70 or higher and A96 or lower when measured with a Type A durometer at a temperature of 23°C and a humidity of 50 RH, and having a ten-point average roughness Rz measured according to JIS B 0601:2001. ｊｉｓA pump-down wiper having a diameter of 30 μm or less. (2) The pump-down wiper according to (1), wherein the elastomer material is biodegradable. (3) The pump-down wiper according to (1) or (2), wherein the biodegradable elastomer material has a weight retention rate of 95% or more after being immersed in deionized water at 66°C for 2 hours and dried at 100°C for 2 hours, and a weight retention rate of less than 95% after being immersed in deionized water at 66°C for 96 hours and dried at 100°C for 2 hours. (4) The pump-down wiper according to any one of (1) to (3), wherein the tear strength of the elastomer material is 20 N / mm or more. (5) A pump down wiper according to any one of (1) to (4), wherein, when the transport direction of the downhole tool is defined as the first direction and the radial direction perpendicular to the first direction is defined as the second direction, the maximum outer diameter OW of the pump down wiper in the second direction is 2.0% to 10.0% larger than the maximum outer diameter OT of the downhole tool in the second direction. (6) A downhole tool comprising the pump down wiper according to any one of (1) to (5). (7) A downhole tool comprising the steps of transporting a downhole tool comprising a pump down wiper containing a degradable elastomer material into a well, and decomposing the pump down wiper by bringing it into contact with a fluid present in the well, wherein the surface hardness of the pump down wiper when measured with a Type A durometer at a temperature of 23°C and a humidity of 50 RH is A70 or higher and A96 or lower, and the ten-point average roughness Rz measured according to JIS B 0601:2001 ｊｉｓ How to use a pump-down wiper with a particle size of 30 μm or less.

[0008] This disclosure provides a pump-down wiper capable of suppressing breakage during transport, a downhole tool equipped with the same, and a method for using the pump-down wiper.

[0009] Figure 1 is a schematic diagram showing the pump-down wiper according to this embodiment. Figure 2 is a cross-sectional view taken along line II-II in Figure 1. Figure 3 is a schematic diagram showing the down-hole tool according to this embodiment. Figure 4 is a schematic diagram showing the sealing member in an expanded state. Figure 5 is a perspective cross-sectional view illustrating the ring on which the pump-down wiper is mounted. Figure 6 is a partial cross-sectional view of the pump-down wiper.

[0010] The following describes in detail the pump-down wiper, downhole tool, and method of using the pump-down wiper as described herein.

[0011] (Pump-down wiper) The pump-down wiper 10 is a component of the plug 20, which is a down-hole tool, and is a component for improving the transportability of the plug 20.

[0012] The pump-down wiper 10 can be attached to the bottom 25 or ring 24 of the plug (flak plug or bridge plug, etc.) 20, which is a downhole tool shown in Figure 3, as will be described in detail later.

[0013] Figure 1 shows a perspective view of the pump-down wiper 10. Figure 2 shows a cross-sectional view of the pump-down wiper 10. Figure 2 corresponds to the cross-sectional view taken along line II-II in Figure 1.

[0014] As shown in Figures 1 and 2, the pump-down wiper 10 comprises a ring portion 10a and a fin 10b provided on the outer circumference of the ring portion 10a, which protrudes outward in the circumferential direction from the outer surface of the ring portion 10a. Three spaced-apart notches 10d are formed on the outer edge of the fin 10b. The notches 10d divide the tip of the fin 10b into three wing portions 10c. The wing portions 10c are inclined toward the upstream side (upward in Figure 2) in the conveying direction of the plug 20. As a result, the pump-down wiper 10 can effectively receive the fluid and improve the conveyance of the plug 20. The fin 10b can also be described as an annular plate-shaped member provided on the outer circumference of the ring portion 10a, and as a member whose outer circumference or the entire plate-shaped member is inclined toward the upstream side (upward in Figure 2) in the conveying direction. The pump-down wiper 10 of this disclosure can have such an inclined shape by having a specific breaking strength and a specific ten-point average roughness, thereby improving the propulsion force when transporting the plug 20.

[0015] Figure 6 shows a partial cross-sectional view of the fin 10b in the pump-down wiper 10. Figure 6 corresponds to the cross-sectional view taken along line II-II in Figure 1, and shows only a portion of it. Although not limited to this, the tip length Lt of the blade portion 10b shown in Figure 6 is preferably 5 mm or less. The upstream angle θu of the fin 10b is preferably 130° or more. The downstream angle θd of the fin 10b is preferably 130° or more. In this case, it is preferable that θu is the same as θd, or that θu is greater than θd (θu ≥ θd).

[0016] (Elastomer material) The pump-down wiper 10 includes an elastomer material. The pump-down wiper 10 may further include materials other than the elastomer material.

[0017] Preferably, the pump-down wiper 10 contains an elastomer material as its main component. Containing an elastomer material as its main component means that the elastomer material accounts for 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the total mass of the pump-down wiper 10. As the elastomer material constituting the pump-down wiper 10, known elastomer materials can be used, and it is preferable that it be one or more selected from the group consisting of silicone rubber, fluororubber, urethane rubber, natural rubber, isoprene rubber, ethylene propylene rubber, butyl rubber, styrene rubber, acrylic rubber, aliphatic polyester rubber, chloroprene rubber, polyester-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers. Of these, it is preferable to use a biodegradable elastomer material.

[0018] The content of elastomer material relative to the total mass of the pump-down wiper 10 can be analyzed by known methods, for example, by extraction of low molecular weight monomers and ashing of the elastomer material. Specifically, a sample is cut from the pump-down wiper at any position, and the cut sample is freeze-pulverized to obtain particles of 500 μm or less. Next, 5.0 g of the pulverized material and 100 ml of toluene are placed in a round-bottom flask and heated at 80°C for 3 hours to extract the low molecular weight monomers contained in the pulverized material. Next, the extract is filtered using a suction filter equipped with a suitable filter, and the filtration residue and filter are vacuum-dried to remove the toluene. The amount of low molecular weight monomers is calculated by weighing the dried material. Next, the main component elastomer is gasified by firing at 500°C in an air atmosphere using an electric furnace. The weight of the residue remaining after firing is measured. The elastomer material content can be calculated by subtracting the amount of low molecular weight monomers and the amount of firing residue from the weight of the pulverized material used during extraction.

[0019] (Degradable Elastomer Materials) First, in this specification, "degradable" means biodegradability, where the material is broken down by microorganisms in the soil; hydrolysis, where the material is broken down by a solvent such as a fracturing fluid (e.g., water); or degradability, where the material can be chemically broken down by any other method. Water may optionally contain acids or alkalis. In this specification, "decomposition" includes, for example, a decrease in the degree of polymerization, which reduces the strength the material originally possessed, making it brittle and allowing it to easily collapse and lose its shape under external force (disintegration).

[0020] The biodegradable elastomer material of this embodiment includes at least one selected from the group consisting of urethane rubber, natural rubber, isoprene rubber, ethylene propylene rubber, butyl rubber, styrene rubber, acrylic rubber, aliphatic polyester rubber, chloroprene rubber, polyester thermoplastic elastomer, and polyamide thermoplastic elastomer. It is more preferable that the biodegradable elastomer material includes at least one selected from the group consisting of styrene rubber, aliphatic polyester rubber, urethane rubber, polyester thermoplastic elastomer, and polyamide thermoplastic elastomer.

[0021] Since the pump-down wiper 10 of this embodiment is preferably hydrolyzed at a specific temperature or higher, the biodegradable elastomer material is preferably made of hydrolyzable functional groups. Examples of hydrolyzable functional groups include urethane groups, ester groups, amide groups, carboxyl groups, hydroxyl groups, silyl groups, acid anhydrides, and acid halides. In this specification, "having hydrolyzable functional groups" means having the above-mentioned functional groups as bonds that form the main chain of the rubber molecule, or having them as side chains of rubber molecules that serve as crosslinking points, for example.

[0022] The biodegradable elastomer material having hydrolyzable functional groups preferably includes urethane rubber, polyester thermoplastic elastomer, or polyamide thermoplastic elastomer. Of these, urethane rubber is particularly preferred because its physical properties, such as the structure, hardness, and degree of crosslinking, can be easily adjusted. The hardness of the urethane rubber can be controlled by the amount of crosslinking agent or filler added. For example, the crosslinking agent content can be 0.1 to 20 parts by mass per 100 parts by mass of urethane rubber. By setting it within this range, the crosslinking reaction can be sufficiently advanced, increasing the surface hardness while suppressing the reduction in elongation and embrittlement due to excessive crosslinking, and preventing unreacted crosslinking agent from precipitation (blooming) on ​​the surface, thus maintaining a good surface condition. Furthermore, the filler content (e.g., silica) can be greater than 0 parts by mass and 500 parts by mass or less per 100 parts by mass of urethane rubber. By setting it within this range, the increase in viscosity of the unvulcanized rubber composition can be suppressed, and good fluidity and mold transferability during molding can be maintained, so that molded products with high dimensional accuracy can be obtained. It is also possible to omit the addition of fillers.

[0023] (Urethane Rubber) Urethane rubber, also known as urethane elastomer, is a type of rubber material having urethane bonds (-NH-CO-O-) in its molecule. Urethane rubber is usually obtained by a condensation reaction between an isocyanate compound and a compound having a hydroxyl group. Examples of isocyanate compounds used in this condensation reaction include aromatic, aliphatic, alicyclic di, tri, or tetra polyisocyanates, or mixtures thereof. Aromatic isocyanate compounds may have multiple aromatic rings. Examples of compounds having a hydroxyl group used in this condensation reaction include polyols. Examples of urethane rubber include polyester-based urethane rubber having ester bonds in its main chain and polyether-based urethane rubber having ether bonds in its main chain. In this embodiment, polyester-based urethane rubber is preferred because it is easier to control the decomposition and disintegration properties of the downhole tool composition.

[0024] Urethane rubber can be classified into three types based on the molding method: i) millable type, which can be molded using the same processing method as general rubber; ii) thermoplastic type, which can be molded using the same processing method as thermoplastic resin; and iii) casting type, which can be molded using a processing method that involves heat curing with liquid raw materials. The urethane rubber used in this embodiment may be of any of these types.

[0025] (Polyester-based thermoplastic elastomers) Polyester-based thermoplastic elastomers are elastomers whose main component is a polyester-based block copolymer. Specifically, examples of polyester-based thermoplastic elastomers include block copolymers of a hard segment made of polyester and a soft segment made of polyether. Examples of hard segments include aromatic polyesters and aliphatic polyesters, such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polyhydroxyalkanoic acid. Examples of soft segments include polyethylene glycol, polypropylene glycol, and polyethers such as polytetramethylene ether glycol.

[0026] Polyester thermoplastic elastomers may be block copolymers in which both the hard segment and the soft segment are made of polyester. In this case, aromatic polyesters can be used as the hard segment. Aromatic polyesters include, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. The soft segment includes aliphatic polyesters with a lower modulus of elasticity than the hard segment. Such aliphatic polyesters include, for example, polyhydroxyalkanoates with an alkyl chain length of 2 or more. Because polyester thermoplastic elastomers have ester bonds, they are prone to decomposition and disintegration.

[0027] (Polyamide-based thermoplastic elastomers) Polyamide-based thermoplastic elastomers are block copolymers of a hard segment made of polyamide and a soft segment made of polyether and / or polyester. The hard segment includes aliphatic polyamides. Aliphatic polyamides include, for example, nylon 6, nylon 11, and nylon 12. The soft segment includes, for example, polyethers such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol. Because polyamide-based thermoplastic elastomers have amide bonds, they are prone to hydrolysis and decomposition under high temperature and high pressure, and are easily disintegrated.

[0028] Polyester-based thermoplastic elastomers and polyamide-based thermoplastic elastomers can have their hard and soft segments, or their ratios, adjusted to suit desired degradation and mechanical properties.

[0029] (Degradability) When using a degradable elastomer material as the elastomer material, it is required that the strength of the pump-down wiper 10 does not decrease during the transport of the downhole tool. For this reason, it is preferable that the degradable elastomer material has a weight retention rate of 95% or more after immersion in ion-exchanged water at 66°C for 2 hours and drying at 100°C for 2 hours, and a weight retention rate of less than 95% after immersion in ion-exchanged water at 66°C for 96 hours and drying at 100°C for 2 hours. The time it takes for the downhole tool to be transported through the well casing and reach the set position is a maximum of about 2 hours. Therefore, by having such a weight retention rate in the degradable elastomer material, it is possible to suppress the decrease in hardness due to decomposition during transport. Furthermore, it becomes possible to decompose quickly after transport.

[0030] From a similar viewpoint, it is more preferable that the weight retention rate after immersion in ion-exchanged water at 66°C for 2 hours and drying at 100°C for 2 hours is 95% or more, and that the weight retention rate after immersion in ion-exchanged water at 66°C for 96 hours and drying at 100°C for 2 hours is 90% or less, and it is even more preferable that the weight retention rate after immersion in ion-exchanged water at 66°C for 2 hours and drying at 100°C for 2 hours is 95% or more, and that the weight retention rate after immersion in ion-exchanged water at 66°C for 96 hours and drying at 100°C for 2 hours is 70% or less.

[0031] The weight retention rate after immersion in ion-exchanged water at 66°C for 2 hours and drying at 100°C for 2 hours is measured by the following procedure. Specifically, one or more 5g samples are cut from any point on the pump-down wiper to prepare the samples. The weight of each prepared sample is measured under conditions of 23°C and 50% RH, and the average of the measured values ​​is used to determine the weight (W) before immersion in ion-exchanged water (before decomposition). １ Next, each sample is immersed in deionized water at 66°C for 2 hours, and then each sample is dried in a constant temperature dryer at 100°C for 2 hours. The weight of each dried sample is measured under conditions of 23°C and 50% humidity, and the average of the measured values ​​is used to determine the weight (W) after immersion (after decomposition). ２ ) The weight retention rate (%) is calculated from the above measurements using the following formula (1): Weight retention rate (%) = W ２ / W １ ×100 (1) The weight retention rate after immersion in ion-exchanged water at 66°C for 96 hours and drying at 100°C for 2 hours can also be determined by the same procedure.

[0032] (Structure of pump-down wiper) The maximum outer diameter OW of the pump-down wiper 10 is not greater than the inner diameter H of the casing DH (OW ≤ H). It is preferably not greater than 95% of the inner diameter H of the casing DH, more preferably not greater than 97%, and even more preferably not greater than 99%. When the maximum outer diameter OW is not greater than 95% of the inner diameter H of the casing DH, contact between the pump-down wiper 10 and the inner diameter H of the casing can be suppressed, so fracture is less likely to occur. Without being limited thereto, for the pump-down wiper 10, the difference between the maximum outer diameter OW and the inner diameter IW (maximum outer diameter OW - inner diameter IW) is preferably not greater than 80 mm, more preferably not greater than 50 mm, and even more preferably not greater than 30 mm. When the difference between the maximum outer diameter OW and the inner diameter IW is not greater than 80 mm, the area receiving fluid during conveyance of the plug 20, which is a downhole tool, increases, thus improving conveyability. Furthermore, since the wall thickness of the member of the plug 20 disposed adjacent to or in the vicinity of the pump-down wiper 10 can be increased, the load-bearing capacity of the plug 20 can be improved. In addition, the thickness T is preferably not greater than 25 mm, more preferably not greater than 20 mm, and even more preferably not greater than 15 mm. When the thickness T is not greater than 25 mm, even if the pump-down wiper 10 remains in the wellbore after use, the risk of clogging during mill out can be reduced. If the pump-down wiper comprises a degradable elastomer material, it can be degraded within a suitable period of time.

[0033] The maximum outer diameter OW of the pump-down wiper 10 is preferably 1.0% or more larger than the maximum outer diameter OT of the plug (downhole tool) 20, more preferably 2.0% or more larger, even more preferably 5.0% or more larger, and particularly preferably 7.0% or more larger. It is even more preferably 10.0% or less larger, more preferably 9.0% or less larger, and even more preferably 8.0% or less larger. Here, the maximum outer diameters of the pump-down wiper 10 and the plug 20 refer to the maximum outer diameter in the second direction (Y direction shown in Figure 3), when the transport direction of the plug 20 is the first direction (X direction shown in Figure 3), and the radial direction perpendicular to the first direction is the second direction (Y direction shown in Figure 3). In this specification, the maximum outer diameter OT of the plug 20 excludes the pump-down wiper 10. Because the maximum outer diameter OW of the pump-down wiper 10 and the maximum outer diameter OT of the plug 20 satisfy this relationship, when the plug 20 is viewed from the X-axis direction as shown in Figure 3, the pump-down wiper 10 protrudes from the outer edge of the plug 20, thereby increasing the area that receives fluid. Therefore, the plug 20 can be transported more efficiently compared to when the pump-down wiper 10 is not provided.

[0034] Depending on the design of the pump-down wiper 10, when it is not receiving fluid, the maximum outer diameter OW of the pump-down wiper 10 can be set to be approximately the same as the maximum outer diameter OT of the plug 20, and when it receives fluid, the fins can expand to increase the maximum outer diameter OW of the pump-down wiper 10. In such cases where the outer diameter changes depending on whether or not it is receiving fluid, the comparison of the maximum outer diameters of the pump-down wiper 10 and the plug 20 should be performed when the pump-down wiper 10 is receiving fluid.

[0035] The maximum outer diameter OW, inner diameter IW, and thickness T of the pump-down wiper 10 can be measured using calipers or a micrometer.

[0036] (Physical Properties of Pump-Down Wiper) The pump-down wiper 10 of the present disclosure has a surface hardness of A70 or more and A96 or less when measured with a type A durometer at 23°C and 50 RH% humidity. When the pump-down wiper 10 has such hardness, breakage can be effectively suppressed, and the conveyance performance of a plug 20 can be improved.

[0037] From the same viewpoint, the surface hardness is more preferably A75 or more and A96 or less, and still more preferably A80 or more and A96 or less. A desired surface hardness can be obtained by adjusting the heating temperature and heating time in the vulcanization step and controlling the crosslink density. For example, increasing the vulcanization temperature or extending the vulcanization time can promote the crosslinking reaction and increase the surface hardness.

[0038] The surface hardness measured by a type A durometer can be measured in accordance with JIS K 6253. Specifically, the measurement is performed using a type A durometer (manufactured by Kansai Instruments Manufacturing Co., Ltd.) under the conditions of 23°C and 50% RH. Place the measurement sample on a stage, press the indenter against the measurement sample, and measure the hardness after 5 seconds. The hardness is measured at any 5 points on the measurement sample, and the average value is taken as the surface hardness A. When the pump-down wiper is directly used as the measurement sample, the measurement is performed at 5 points, with any position having the largest thickness of the pump-down wiper taken as the measurement position. A sample cut out from any position having the largest thickness of the pump-down wiper may also be used as the measurement sample.

[0039] The pump-down wiper 10 of the present disclosure has a ten-point average roughness Rz measured in accordance with JIS B 0601:2001 ｊｉｓ of 30 µm or less. When the ten-point average roughness Rz ｊｉｓ exceeds 30 µm, the rough surface acts as an initiation point, and the pump-down wiper tends to be prone to breakage. However, since the ten-point average roughness Rz ｊｉｓ of the pump-down wiper of the present disclosure is 30 µm or less, breakage can be suppressed. From the same viewpoint, the ten-point average roughness Rz ｊｉｓThe roughness is more preferably 25 μm or less, and even more preferably 20 μm or less. Also, the ten-point average roughness Rz ｊｉｓ It is preferable that the thickness is 0.01 μm or greater. Ten-point average roughness Rz ｊｉｓ This can be controlled by controlling the surface roughness of the mold, or by adjusting the mold temperature and molding pressure during molding. For example, by increasing the molding pressure and molding in a temperature range where the viscosity of the rubber composition at the lowest torque (ML) is sufficiently reduced, the ability of the rubber to conform to the fine irregularities on the mold surface is improved, thus reducing the ten-point average roughness Rz ｊｉｓ This can reduce the roughness. Furthermore, by polishing the molded rubber product after molding, the final ten-point average roughness Rz can be reduced. ｊｉｓ The process may be adjusted. For example, to obtain a smoother surface, it is preferable to use high-grit (fine-grained) abrasive grains in the finish polishing.

[0040] Ten-point average roughness Rz ｊｉｓ The measurement is performed using the following procedure. First, prepare a 10 mm x 10 mm sample by cutting it from the pump-down wiper. Alternatively, the pump-down wiper can be used as the measurement sample as is. Next, set the magnification of the laser microscope (manufactured by Keyence Corporation) to 10x and scan an arbitrary 5 mm x 5 mm area on the surface of the measurement sample to take the measurement. Multiple lines are used to measure 9 points, and the average roughness of 10 points is measured.

[0041] As described above, the ten-point average roughness can be measured at any position on the surface of the pump-down wiper 10. In particular, when the pump-down wiper 10 is attached to the plug 20, it is preferable to measure it at any position on the surface corresponding to the outer surface, in other words, at any position on the part that may come into contact with fluid. The outer circumferential surface of the pump-down wiper 10 may receive fluid or come into contact with foreign matter, and is prone to fracture. Therefore, in such a part, a specific ten-point average roughness Rz ｊｉｓ Having this feature helps to suppress breakage. Furthermore, the upstream surface of the pump-down wiper in the conveying direction is particularly prone to breakage because it receives fluid, so it is more preferable to measure on the upstream surface.

[0042] As an example, the average roughness of ten points Rz of the pump-down wiper 10 ｊｉｓ As shown in Figure 2, it is preferable to measure on a surface located a length L inward from the outermost edge. The length L is preferably 1 mm to 5 mm, and more preferably 1 mm. Furthermore, it is preferable that the surface to be measured is the surface located on the upstream side in the conveying direction (the top surface shown in Figure 2).

[0043] It is more preferable that the pump-down wiper 10 has a tear strength of 20 N / mm or more, as measured according to JIS K 6252-1:2015. Having such a tear strength allows for better suppression of fracture, thereby increasing the shape stability of the pump-down wiper 10 and maintaining conveying performance. From a similar viewpoint, it is more preferable that the tear strength is 30 N / mm or more, even more preferable that it is 40 N / mm or more, and particularly preferable that it is 50 N / mm or more.

[0044] The tear strength test is measured according to JIS K 6252-1:2015 as described above. Specifically, an angle test specimen is cut from the pump-down wiper to prepare a measurement sample. Next, using a universal material testing machine (INSTRON), the tear breaking load (test force) is measured when an uncut angle test specimen is pulled under the conditions of 23°C, 50% RH, and a travel speed of 500 mm / min. The test forces of three measurement samples are measured, and the average value is taken as the tear strength test. If it is difficult to cut the angle test specimen from the pump-down wiper, the measurement may be performed using a smaller test specimen that is a scaled-down version of the angle test specimen. In that case, the tear strength test conditions are measured using the travel speed multiplied by the scale factor.

[0045] Figures 1 and 2 show an example configuration in which the fin 10b is divided into three blade sections 10c, but the shape of the pump-down wiper 10 is not limited to this and can be any shape that functions as a pump-down wiper 10. For example, the number of blade sections 10c is not limited to three, but can be any number of two or more. The shape of the blade sections 10c is also arbitrary. A single fin may be provided so as to surround the outer circumference of the ring without forming a notch 10d, or multiple fins may be arranged in the circumferential and / or thickness directions on the outer circumference of the ring. When fluid is received, the fins can expand to expand the maximum outer diameter OW of the pump-down wiper 10. The pump-down wiper 10 may also be without fins. For example, the outer surface of the ring may protrude from the outer edge of the plug 20, like an O-ring. The above-described features can be combined in any way.

[0046] By providing a notch 10d in the pump-down wiper 10, the load on the pump-down wiper 10 due to water pressure can be reduced, and the breakage of the pump-down wiper 10 can be prevented. When providing a notch 10d in the pump-down wiper 10, it is preferable to provide the notch 10d symmetrically or evenly with respect to the central axis of the pump-down wiper 10. By providing the notch 10d as described above, the effect of preventing breakage can be obtained.

[0047] According to the pump-down wiper 10 of this embodiment, by setting the hardness to a specific value and reducing the ten-point average roughness of the pump-down wiper 10, the occurrence of breakage can be suppressed, and breakage during transport can be suppressed. As a result, it is possible to increase the transport speed and reduce the amount of fluid used when transporting downhole tools. If the pump-down wiper 10 is formed from a biodegradable elastomer material, the mill-out process can be eliminated or reduced, which can also reduce time and costs.

[0048] (Downhole Tool) A downhole tool comprising the pump-down wiper 10 of the present disclosure is described. The plug 20, which is a downhole tool, comprises a mandrel 21 extending in the direction in which the downhole extends, and an annular sealing member 22, a fixing member 23, a ring 24, a bottom 25, and a cone 26 arranged on the outer circumferential surface of the mandrel 21 in the axial direction of the mandrel 21, as shown in Figure 3. The pump-down wiper 10 is provided on the bottom 25. The fixing member 23 is, for example, a slip 30.

[0049] The mandrel 21 is a hollow cylindrical body, but is not limited to this, with an outer diameter of 30 to 200 mm and a length of 250 to 1000 mm.

[0050] The annular sealing member 22 is formed from an elastic material and is provided around the mandrel 21. When the sealing member 22 is compressed in the axial direction of the mandrel 21 (the direction in which the plug 20 is transported), the outer diameter of the sealing member 22 expands in a direction perpendicular to the axial direction of the mandrel 21 (radial direction). As a result, the outer surface of the sealing member 22 abuts against the inner wall IH of the casing DH, and the inner surface of the sealing member 22 abuts against the outer circumferential surface of the mandrel 21, thereby closing the space between the plug 20 and the casing DH.

[0051] The fixing member 23 refers to a member provided around the mandrel 21 that has the function of fixing the plug 20 to the inner wall IH of the casing DH, and for example, a slip 30 is known. The slip 30 is made of metal, inorganic material, etc. When an axial force is applied to the mandrel 21, the slip 30 slides along the inclined surface of the cone 26, moves radially perpendicular to the axial direction of the mandrel 21, and comes into contact with the inner wall IH of the casing DH, thereby fixing the plug 20 to the inner wall IH of the casing DH. As a result, the sealing member 22 is pressed by the cone 26, which is the pressing member, and expands in diameter, and the sealing member 22 can also be fixed to the inner wall IH of the casing DH. In order to make the sealing of the space between the plug 20 and the casing DH even more reliable, the slip 30 may be provided with one or more grooves, protrusions, rough surfaces, etc. in the part that comes into contact with the inner wall IH of the casing DH.

[0052] The slip 30 may be divided into a predetermined number of pieces in the circumferential direction perpendicular to the axial direction of the mandrel 21, or, as shown in Figures 3 and 4, it may not be divided into a predetermined number of pieces in advance, but may have a cut that ends midway from one end to the other along the axial direction. In this case, when an axial force of the mandrel 21 is applied to the cone 26, the cone 26 enters the lower surface of the slip 30, causing the slip 30 to split and divide along the cut and its extension, and then each divided piece moves outward perpendicular to the axial direction of the mandrel 21.

[0053] The fixing member 23 (slip 30 in Figure 3) and the cone 26 can be positioned between the ring 24 and the bottom 25 so that axial force can be applied to the mandrel 21. The fixing member 23 can be positioned adjacent to the expandable annular sealing member 22 via the cone 26. A portion of the fixing member 23 can be positioned to overlap with the cone 26, and at least a portion of the cone 26 can be positioned between the sealing member 22 and the fixing member 23.

[0054] As shown in Figures 3 and 4, the plug 20 may have two fixing members 23 that sandwich the sealing member 22. At least one fixing member 23 is required, and three or more can be provided. The same applies to the cone 26. The number of sealing members 22 is also not limited to one; multiple sealing members can be provided.

[0055] The ring 24 and the bottom 25 are provided on the outer circumferential surface of the mandrel 21. Between the ring 24 and the bottom 25, as shown in Figure 3, a sealing member 22, a fixing member 23, and a cone 26 are arranged. At least one of the ring 24 and the bottom 25 is configured to be slidable along the axial direction of the mandrel 21 on the outer circumferential surface of the mandrel 21, and the distance between them can be changed. As a result, the ring 24 and the bottom 25 can apply axial force to the sealing member 22, the fixing member 23, and the cone 26.

[0056] As shown in Figure 5, the bottom 25 has an annular body 25a. An inclined surface 25b is formed on the downstream end of the annular body 25a in the conveying direction. A groove 25c is formed on the outer circumferential surface of the body 25a so as to surround the outer circumference. A protrusion 25d is provided at the end of the groove 25c. The ring portion 10a of the pump-down wiper 10 is fitted into the space formed by the groove 25c and the protrusion 25d, and the protrusion 25d prevents the pump-down wiper 10 from detaching from the bottom 25.

[0057] In the plug 20, as shown in Figure 4, the fixing member 23 slides along the surface of the cone 26 to fix the plug 20 inside the casing DH, and the cone 26 presses against the sealing member 22, causing the sealing member 22 to expand in diameter. Therefore, it is preferable that the pump-down wiper 10 is not positioned between the fixing member 23 and the sealing member 22 so as not to obstruct these movements. For this reason, it is preferable that the pump-down wiper 10 be provided at least one of the upstream or downstream sides in the conveying direction from the position where the sealing member 22 and the fixing member 23 are provided. Figure 3 shows an example configuration in which one pump-down wiper 10 is provided on the downstream side in the conveying direction, but it is not limited to this. The pump-down wiper 10 may also be provided on the upstream side in the conveying direction. For example, the pump-down wiper 10 can be installed on the ring 24. It is also possible to provide it on both the ring 24 and the bottom 25. Furthermore, it is possible to provide three or more pump-down wipers 10.

[0058] The configuration of the plug 20 shown in Figures 3 and 4 is an example, and the structure of the mandrel 21, sealing member 22, fixing member 23, ring 24, bottom 25, and cone 26 can be arbitrarily changed. The plug 20 may further include parts not shown.

[0059] In this embodiment, the materials used to form the mandrel 21, sealing member 22, fixing member 23, ring 24, bottom 25, and cone 26 include, for example, metal materials such as aluminum, steel, or stainless steel, fibers, wood, composite materials, and resins.

[0060] The mandrel 21, sealing member 22, fixing member 23, ring 24, bottom 25, and cone 26 are preferably each made of a biodegradable resin or biodegradable metal. In other words, it is preferable that all components constituting the plug 20 are made of biodegradable materials. This makes it easier to remove the plug 20 after well treatment using the plug 20.

[0061] In this specification, "degradable resin or degradable metal" means a resin or metal that can be easily broken down by biodegradation or hydrolysis, dissolution in water or hydrocarbons in a well, or by some chemical method. Examples of degradable resins, in addition to the degradable elastomer material, include hydroxycarboxylic acid aliphatic polyesters such as polylactic acid (PLA) and polyglycolic acid (PGA), lactone aliphatic polyesters such as polycaprolactone (PCL), diol / dicarboxylic acid aliphatic polyesters such as polyethylene succinate and polybutylene succinate, copolymers thereof, such as glycolic acid / lactic acid copolymers, and mixtures thereof, as well as aliphatic polyesters that use aromatic components such as polyethylene adipate / terephthalate in combination.

[0062] Examples of water-soluble resins include polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, polyacrylamide (N,N substituted), polyacrylic acid, and polymethacrylic acid. Copolymers of the monomers that form these resins include, for example, ethylene-vinyl alcohol copolymer (EVOH) and acrylamide-acrylic acid-methacrylic acid interpolymer.

[0063] Examples of biodegradable metals include alloys whose main components are magnesium, aluminum, calcium, etc.

[0064] (How to use the pump-down wiper) Next, the pump-down wiper of this embodiment is used as follows.

[0065] A plug 20 is prepared, which is fitted with a pump-down wiper 10 made of a biodegradable elastomer material.

[0066] The plug (downhole tool) 20 comprises a cylindrical mandrel 21, a sealing member 22 provided around the mandrel 21, and a fixing member 23 provided around the mandrel 21 for fixing the downhole tool 20 to the inner wall of the casing DH. The pump-down wiper 10 is positioned around the mandrel 21 and is used so as to be positioned at least one of the upstream or downstream sides in the conveying direction of the position where the sealing member 22 and the fixing member 22 are provided. Such a method of using the pump-down wiper 10 is also included in one aspect of the present disclosure.

[0067] Next, the plug 20 is inserted into the casing DH, and fluid is introduced from the upstream direction of transport to transport the plug 20 to the desired position in the casing DH. At this time, the pump-down wiper 10 receives the supplied fluid.

[0068] Next, the ring 24 and the bottom 25 are slid to bring the fixing member 23 into contact with the inner wall IH of the casing DH, and the sealing member 22 is expanded in diameter to close the space between the casing DH and the plug 20.

[0069] Next, a ball or the like (not shown) is placed in the hollow part of the mandrel 21, the mandrel 21 is closed, and hydraulic fracturing is performed by injecting a fracturing fluid at high pressure.

[0070] The pump-down wiper 10 is exposed to fluids present in the well, such as the fluid used to transport the plug 20 and fracturing fluid, thereby causing the pump-down wiper to disintegrate from the part that comes into contact with the fluid.

[0071] The pump-down wiper 10 of this embodiment has a specific hardness and a low ten-point average roughness, which suppresses the occurrence of fracture and prevents fracture during the transport of the plug 20. As a result, it is possible to increase the run speed and reduce the amount of fluid used when transporting the downhole tool. Furthermore, since the pump-down wiper 10 contains a biodegradable elastomer material, it can be decomposed by exposure to the fluid in the well, eliminating or reducing the need for the mill-out process, and thus reducing time and costs.

[0072] The present invention will be specifically described based on the following examples, but the present invention is not limited to these examples.

[0073] In Example 1 and Comparative Examples 1 and 2, a pump-down wiper was formed by cutting a processing material made from polyester polyurethane (polyester urethane rubber) using millable molding. In Examples 2 to 6, a pump-down wiper was formed by cutting a processing material made from polyester polyurethane using casting. In the examples and comparative examples, as described above, the hardness and ten-point average roughness were changed by adjusting the heating temperature or heating time in the vulcanization process, controlling the surface roughness of the mold, adjusting the mold temperature or molding pressure during molding, and polishing the surface. For these pump-down wipers, A hardness, ten-point average roughness, tear strength, and actual tests were performed using the following methods. The results are shown in Table 1.

[0074] [Hardness A] Measured according to JIS K 6253-3:2023. Specifically, measurements were taken using a Type A durometer (manufactured by Kansai Kiki Seisakusho Co., Ltd.) under 23°C and 50% RH conditions. The pump-down wiper, which was the sample to be measured, was placed on a table, and the measurement point was chosen as the point with the greatest wall thickness on the pump-down wiper. The indenter was pressed against the point, and the hardness was measured after 5 seconds. Hardness was measured at five measurement points, and the average value was defined as surface hardness A.

[0075] [Ten-point average roughness] Measurement was performed according to JIS B 0601:2001. Specifically, a sample was prepared by cutting a 10 mm x 10 mm sample from a pump-down wiper. Next, a laser microscope (manufactured by Keyence Corporation) was set to 10x magnification, and measurements were taken by scanning an arbitrary 5 mm x 5 mm area on the sample surface. Ten-point average roughness was measured at nine locations along multiple lines.

[0076] [Tear Test Force] The tear test force was measured according to JIS K 6252-1:2015. Specifically, angle test specimens were cut from a pump-down wiper to prepare the measurement samples. Next, using a universal material testing machine (INSTRON), the tear breaking load (test force) was measured when an uncut angle-shaped test specimen was pulled under the conditions of 23°C, 50% RH, and a travel speed of 500 mm / min. The test forces of three samples were measured, and the average value was taken as the tear test force. Table 1 shows the value obtained by dividing the maximum force required to tear the angle-shaped test specimen by the thickness of the test specimen. However, if it is not possible to cut the angle test specimen from the pump-down wiper as described above, the measurement may be taken using a smaller test specimen that is a scaled-down version of the angle test specimen. In that case, the tear test conditions should be measured using the travel speed multiplied by the scale factor.

[0077] [Weight Retention Rate] The weight retention rate after immersion in deionized water at 66°C for 2 hours and drying at 100°C for 2 hours was measured using the following procedure. Specifically, one or more 5g samples were cut from any point on the pump-down wiper to prepare the samples. The weight of each prepared sample was measured under conditions of 23°C and 50% RH, and the average of the measured values ​​was used to determine the weight (W) before immersion in deionized water. １ Next, each sample was immersed in deionized water at 66°C for 2 hours, and then dried in a constant temperature dryer at 100°C for 2 hours. The weight of each dried sample was measured under conditions of 23°C and 50% humidity, and the average of the measured values ​​was used to determine the weight (W) after immersion (after decomposition). ２ ) was used. From the above measurements, the weight retention rate (%) was calculated using the following formula (1): Weight retention rate (%) = (W ２ / W １) × 100 (1) The weight retention rate after immersion in ion-exchanged water at 66°C for 96 hours and drying at 100°C for 2 hours was also determined using the same procedure. The weight retention rates for each example are shown in Table 1.

[0078] [Product Testing] A pump-down wiper was attached to the downhole tool, and fluid was pumped from the upstream side of the downhole tool. The test was conducted to confirm whether there was any pressure drop on the upstream side until the target flow rate was reached, and evaluated according to the following criteria. The occurrence of a pressure drop in the actual test meant that the pump-down wiper had broken. A: No pressure drop occurred C: A pressure drop occurred

[0079]

[0080] As shown in Table 1, the A hardness is 70 or higher, and the ten-point mean roughness (Rz ｊｉｓ In Examples 1 to 6, where the A hardness was 30 μm or less, no breakage occurred in the pump-down wiper in the actual test, and no pressure drop occurred. On the other hand, in Examples 1 to 6, where the A hardness was less than 70, the ten-point average roughness (Rz ｊｉｓ Comparative Example 1, where the A hardness exceeds 30 μm, even if the A hardness is 70 or higher, the ten-point average roughness (Rz ｊｉｓ In comparative examples 2 and 3, where the diameter exceeded 30 μm, the pump-down wiper fractured and a pressure drop occurred in the actual tests.

[0081] The pump-down wipers of Examples 1 to 6 retain 95% or more of their weight after being immersed in ion-exchanged water at 66°C for 2 hours and dried at 100°C for 2 hours, and retain less than 95% of their weight after being immersed in ion-exchanged water at 66°C for 96 hours and dried at 100°C for 2 hours. Therefore, they suppress hardness reduction due to decomposition during transport and can decompose quickly after transport.

[0082] 10 Pump-down wiper, 10a Ring section, 10b Fin, 10c Blade section, 10d Notch, 20 Plug, 21 Mandrel, 22 Seal member, 23 Fixing member, 24 Ring, 25 Bottom, 25a Body, 25b Inclined surface, 25c Groove, 25d Protrusion, 26 Cone, 30 Slip, DH Casing, IH Inner wall, H Inner diameter of casing

Claims

1. A pump-down wiper constituting a downhole tool, wherein the downhole tool comprises a cylindrical mandrel, a sealing member provided around the mandrel, and a fixing member provided around the mandrel for fixing the downhole tool to the inner wall of the casing, the pump-down wiper is positioned around the mandrel of the downhole tool, and is positioned at least one of the upstream or downstream sides in the transport direction from the position where the sealing member and the fixing member are provided, and contains an elastomer material, having a surface hardness of A70 or higher and A96 or lower when measured with a Type A durometer at a temperature of 23°C and a humidity of 50 RH, and having a ten-point average roughness Rz measured according to JIS B 0601:2001. ｊｉｓ A pump-down wiper with a diameter of 30 μm or less.

2. The pump-down wiper according to claim 1, wherein the elastomer material is biodegradable.

3. The pump-down wiper according to claim 2, wherein the biodegradable elastomer material has a weight retention rate of 95% or more after being immersed in deionized water at 66°C for 2 hours and dried at 100°C for 2 hours, and has a weight retention rate of less than 95% after being immersed in deionized water at 66°C for 96 hours and dried at 100°C for 2 hours.

4. The pump-down wiper according to claim 1, wherein the tear strength of the elastomer material is 20 N / mm or more.

5. The pump-down wiper according to claim 1, wherein, when the transport direction of the downhole tool is defined as the first direction and the radial direction perpendicular to the first direction is defined as the second direction, the maximum outer diameter OW of the pump-down wiper in the second direction is 2.0% to 10.0% larger than the maximum outer diameter OT of the downhole tool in the second direction.

6. A downhole tool comprising the pump-down wiper described in claim 1.

7. A downhole tool comprising the steps of transporting a pump-down wiper containing a degradable elastomer material into a well, and disintegrating the pump-down wiper by bringing it into contact with the fluid present in the well, wherein the pump-down wiper has a surface hardness of A70 or higher and A96 or lower when measured with a Type A durometer at a temperature of 23°C and a humidity of 50 RH, and a ten-point average roughness Rz measured according to JIS B 0601:2001. ｊｉｓ How to use a pump-down wiper with a particle size of 30 μm or less.

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