A casing and tubing soluble ball switch full bore circulating valve and method of use

Abstract

The present application relates to the technical field of oil exploitation, and specifically provides an oil casing soluble temporary plugging ball switch full-gauge circulating valve and a use method thereof, which comprises a valve body connected to a pipe string at its upper and lower ends, a main circulating hole is formed in the valve body, a sliding sleeve is axially slidably arranged in the valve body, a switch circulating hole is formed in the sliding sleeve, an intermediate abutting piece is further arranged in the valve body, the intermediate abutting piece can guide a soluble temporary plugging ball to block the switch circulating hole, a plurality of arc-shaped plates are uniformly arranged on a conical top cover of the intermediate abutting piece in a circumferential direction, arc-shaped grooves are formed between adjacent arc-shaped plates, the arc-shaped grooves can disturb liquid in a circumferential direction, so that the soluble temporary plugging ball can gradually approach the switch circulating hole, only the same number of soluble temporary plugging balls as the switch circulating hole needs to be put in to block the switch circulating hole, the number of soluble temporary plugging balls used is reduced, and the success rate of blocking is relatively high.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology, and in particular to a soluble temporary plugging ball switch full-bore circulation valve for oil casing and its usage method. Background Technology

[0002] In downhole operations such as pre-fracturing well washing in oil and gas wells, layered sand flushing in multi-layer old wells, and layered circulation well killing, it is usually necessary to connect multiple circulation valves in series at different depths of the tubing string to establish fluid circulation channels between the tubing and casing annulus in layers. After the flushing operation of a single layer is completed, the corresponding oil and casing channels are reliably isolated to avoid interlayer fluid crosstalk, and the whole well layered construction is completed layer by layer.

[0003] Currently, the mainstream method used in the field is to use differential pressure shear-type circulation valves with soluble plugging balls to complete the stratified opening and closing operations. However, when closing the circulation valve, the plugging balls deployed in a single batch cannot accurately seal all circulation holes in the corresponding stratum. This necessitates the deployment of excessive balls to ensure sealing effectiveness, resulting in a significant waste of soluble material and increased construction costs. Unsuccessful plugging balls from the upper circulation holes continue to migrate downwards to the lower-level circulation valves, prematurely sealing deeper circulation holes and disrupting the step-by-step opening sequence from shallow to deep. This prevents the lower-level valves from pressurizing and conducting properly, forcing the interruption of stratified construction. Furthermore, the existing process requires that all upper-level plugging balls be completely dissolved before proceeding to the next stratum. Multi-layer construction in a single well requires prolonged soaking and waiting, significantly extending the operation cycle and reducing construction efficiency. Summary of the Invention

[0004] Therefore, it is necessary to address the current problem that a large number of plugging balls are required when closing the circulation valve, and the plugging success rate of the plugging balls is low, by providing a full-bore circulation valve with soluble temporary plugging ball for oil casing and its usage method.

[0005] The above objectives are achieved through the following technical solutions:

[0006] A soluble temporary plugging ball-operated full-bore circulation valve for oil casing includes:

[0007] The valve body is hollow inside and connected to the tubing at both ends. Multiple main circulation holes are evenly opened circumferentially on the circumferential wall of the valve body. A sliding sleeve is axially slidably arranged inside the valve body. The inner diameter of the sliding sleeve is the same as the inner diameter of the tubing. Multiple switching circulation holes are evenly opened circumferentially on the circumferential wall of the sliding sleeve. The sliding sleeve is configured to move downward step by step as the internal pressure of the tubing increases, so that the main circulation holes and the switching circulation holes are staggered, overlapped, and staggered again.

[0008] A soluble temporary plugging ball is located inside the sliding sleeve. The soluble temporary plugging ball is configured to be inserted into the sliding sleeve when it is necessary to close the main circulation hole, and the number of inserted balls is the same as the number of switching circulation holes.

[0009] An intermediate abutment is axially slidably disposed within the valve body, and the intermediate abutment is configured to guide the soluble temporary plugging ball to block the switch circulation hole when the ball enters the valve body.

[0010] Furthermore, an opening shear pin and a closing shear pin are provided on the inner periphery of the valve body, with the opening shear pin located above the closing shear pin;

[0011] The upper outer peripheral wall of the sliding sleeve is provided with an opening pin groove, the outer periphery of the sliding sleeve is provided with a first annular limiting step, and the inner wall of the valve body is provided with a second annular limiting step. When the opening shear pin is located in the opening pin groove, the switch circulation hole is located above the main circulation hole. When the first annular limiting step abuts against the closing shear pin, the switch circulation hole coincides with the main circulation hole. When the first annular limiting step abuts against the second annular limiting step, the switch circulation hole is located below the main circulation hole.

[0012] Furthermore, the intermediate abutment includes a sealing column and a conical top cover. The sealing column is axially slidably sealed within the sliding sleeve. The conical top cover is fixedly connected to the upper end of the sealing column, with the small end of the conical top cover facing upwards and the large end of the conical top cover abutting against the inner circumferential wall of the sliding sleeve or the inner wall of the valve body. The conical surface of the conical top cover is uniformly provided with arc-shaped plates in the circumferential direction, and an arc-shaped groove is formed between adjacent arc-shaped plates. The arc-shaped groove is used to guide the soluble temporary plugging ball to seal the switch circulation hole.

[0013] Furthermore, a third annular limiting step is provided on the inner circumference of the bottom of the valve body, and the conical top cover is elastic, with the outer diameter of the conical top cover after the large end is retracted being equal to the inner diameter of the third annular limiting step.

[0014] Furthermore, a vulcanized rubber sleeve is provided on the outer periphery of the sealing column.

[0015] Furthermore, a balance hole is provided on the valve body, and the balance hole is located above the main circulation hole.

[0016] Furthermore, a filter screen is provided on the balance hole.

[0017] Furthermore, the valve body is made of 42CrMo alloy steel, is hollow as a whole, and has standard pipe threaded connections at both ends.

[0018] Furthermore, the main circulation holes of the valve body are uniformly distributed around the circumference with a single hole diameter of 12mm, and the switch circulation holes of the sliding sleeve also have a single hole diameter of 12mm. The minimum inner diameter of the valve body is the same as the inner diameter of the sliding sleeve.

[0019] This invention also provides a method for using a soluble temporary plugging ball switch full-bore circulation valve for oil casing, comprising the following steps:

[0020] Step S1: According to the number of reservoir sections, connect the valve body with progressively increasing opening pressure from top to bottom in series with the connecting pipes. After assembly, ensure that the valve's initial orifice is misaligned and closed.

[0021] Step S2: After the tubing string is in place, pump in the working fluid and gradually increase the pressure. After the valve body reaches the opening pressure, the sliding sleeve moves down to open the circulation hole, establishes the circulation channel, and completes the single-layer sand flushing, well washing and fracturing pretreatment operations.

[0022] Step S3: After the single-layer operation is completed, the same number of soluble temporary plugging balls as the switch circulation holes are added. The switch circulation holes are blocked by the intermediate abutment. The pressure is increased to push the sliding sleeve down to block the main circulation holes. The intermediate abutment is moved down and reused in the next stage valve body.

[0023] The beneficial effects of this invention are:

[0024] This invention features an intermediate abutment inside the valve body. This intermediate abutment guides soluble plugging balls to seal the switch circulation hole. The conical top cover of the intermediate abutment has multiple arc-shaped plates evenly arranged circumferentially, forming arc-shaped grooves between adjacent arc-shaped plates. These arc-shaped grooves can circumferentially agitate the liquid, allowing the soluble plugging balls to gradually approach the switch circulation hole. Only the same number of soluble plugging balls as the number of switch circulation holes needs to be added to seal the switch circulation hole, reducing the number of soluble plugging balls used and achieving a high sealing success rate.

[0025] This invention uses a multi-stage valve body with the number of circulation holes increasing from top to bottom. The residual soluble plugging balls that are not completely dissolved in the upper layer cannot block more channels in the lower layer. After closing the valve in a single layer, construction can be carried out directly in the next layer without having to wait for the balls to dissolve for a long time. One trip of tubing can realize multi-layer continuous operation, which greatly shortens the downhole construction cycle.

[0026] This invention balances the pressure difference between the upper and lower parts of the sliding sleeve in real time by opening a balance hole and matching a filter screen on the upper part of the valve body, thereby offsetting the additional load of the wellbore hydrostatic column on the shear pin. When the tubing is lowered, it will not prematurely shear open the shear, causing the valve to open abnormally. The filter screen blocks solid phase impurities in the formation, avoids clogging of the balance hole, and ensures the stability of the tool during lowering.

[0027] This invention sets the inner diameter of the sliding sleeve to be the same as the minimum inner diameter of the tubing string, ensuring that the valve maintains a completely unobstructed flow throughout the opening and closing process. After the soluble temporary plugging ball dissolves, there are no narrowing or jamming points, allowing downhole tools such as logging, fracturing, and workover to pass smoothly without any flow obstruction. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a full-bore circulation valve for a soluble temporary plugging ball switch in an oil casing according to an embodiment of the present invention;

[0029] Figure 2 for Figure 1A left view of a full-bore circulation valve with a soluble temporary plugging ball switch for oil casing provided in one embodiment;

[0030] Figure 3 for Figure 2 A cross-sectional view along AA of a full-bore circulation valve for a soluble temporary plugging ball switch in a casing provided in one embodiment;

[0031] Figure 4 This is a schematic diagram of the structure of two oil casing soluble temporary plugging ball switch full-bore circulation valves connected in series on the tubing string according to an embodiment of the present invention;

[0032] Figure 5 for Figure 4 A cross-sectional view along BB on a tubing string showing two soluble temporary plugging ball switches and full-bore circulation valves connected in series in one embodiment.

[0033] Figure 6 A cross-sectional view of the main circulation hole when two soluble temporary plugging ball valves for oil casing are connected in series on the tubing string, according to an embodiment of the present invention;

[0034] Figure 7 This is a cross-sectional view of the main circulation hole being re-sealed when two soluble temporary plugging ball switches for oil casing are connected in series on the tubing string, according to an embodiment of the present invention.

[0035] Figure 8 This is a cross-sectional view of the sliding sleeve of the next valve body when two oil casing soluble temporary plugging ball switch full-bore circulation valves are connected in series on the tubing string, according to an embodiment of the present invention.

[0036] Figure 9 This is a schematic diagram of the intermediate abutment component of a full-bore circulation valve for a soluble temporary plugging ball switch in an oil casing according to an embodiment of the present invention.

[0037] in:

[0038] 100. Tubing column;

[0039] 200, Valve body; 210, Main circulation hole; 220, Balance hole; 230, Open shear pin; 240, Close shear pin; 250, Sliding sleeve; 260, Switch circulation hole; 270, First annular limit step; 280, Second annular limit step; 290, Third annular limit step;

[0040] 300, Sealing column; 310, Vulcanized rubber sleeve; 320, Conical top cover; 330, Arc plate; 340, Small end; 350, Large end. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0042] The component designations used in this document, such as "first" and "second," are merely for distinguishing the described objects and do not have any sequential or technical meaning. The terms "connection" and "linkage" used in this invention, unless otherwise specified, include both direct and indirect connections (linkages). It should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] The following reference Figures 1-9 This invention describes a soluble temporary plugging ball switch full-bore circulation valve for oil casing.

[0045] A soluble temporary plugging ball switch full-bore circulation valve for oil casing includes a valve body 200, which is hollow inside and connected to a tubing string 100 at both ends. Multiple main circulation holes 210 are evenly opened circumferentially on the circumferential wall of the valve body 200. A sliding sleeve 250 is axially slidably disposed inside the valve body 200. The inner diameter of the sliding sleeve 250 is the same as the inner diameter of the tubing string 100, allowing various downhole tools and logging instruments to pass smoothly without restricting subsequent fracturing, fishing, logging and other construction operations. Furthermore, the sliding sleeve 250 has multiple switching circulation holes 260 evenly distributed circumferentially on its circumferential wall. The number of switching circulation holes 260 is the same as the number of main circulation holes 210. During initial assembly, the switching circulation holes 260 on the sliding sleeve 250 are misaligned with the main circulation holes 210, thus blocking the main circulation holes 210. As the internal pressure of the tubing string 100 increases sequentially, it can move downwards step by step, causing the main circulation holes 210 and the switching circulation holes 260 to overlap and then misalign again, thereby allowing the fluid to open and close the main circulation holes 210. Since oil and gas wells often have multiple independent reservoirs in the vertical direction, each layer has sand burial and pollution blockage problems, requiring separate sand flushing, well washing, and pre-circulation pretreatment. Therefore, multiple valve bodies 200 are generally connected in series on the tubing string 100. One run can cover the entire target layer, realizing multi-layer segmented construction with one run of tubing string 100, saving the need for multiple trips of tubing string 100. Moreover, the pressure required for the sliding sleeve 250 inside the multiple valve bodies 200 to move downwards increases sequentially from top to bottom.

[0046] The liquid in the tubing 100 can be discharged from the main circulation hole 210. When it is necessary to close the main circulation hole 210 again, the operator needs to put a certain number of soluble temporary plugging balls into the tubing 100. Since the liquid continuously circulates from the main circulation hole 210 and the switch circulation hole 260, it can drive the soluble temporary plugging balls to block the switch circulation hole 260. At this time, the pressure in the tubing 100 continues to increase, thereby continuing to push the sliding sleeve 250 downward. When the sliding sleeve 250 moves downward, it causes the switch circulation hole 260 and the main circulation hole 210 to be misaligned, thereby blocking the main circulation hole 210.

[0047] The valve body 200 of the present invention has an axially sliding intermediate abutment. The intermediate abutment is configured to guide the soluble temporary blocking ball to block the switch circulation hole 260 when the soluble temporary blocking ball enters the valve body 200, thereby allowing the pressure in the tubing 100 to gradually increase, and then pushing the sliding sleeve 250 to continue to move downward so that the switch circulation hole 260 on the sliding sleeve 250 is misaligned with the main circulation hole 210.

[0048] It should be noted that setting an intermediate abutment can reduce the number of soluble temporary plugging balls required in traditional construction processes. Furthermore, the efficiency of sealing the switch circulation holes 260 is low when a large number of soluble temporary plugging balls are used in traditional construction processes. However, this invention guides a single soluble temporary plugging ball to align with a single set of switch circulation holes 260 through the intermediate abutment to complete the setting and sealing. Only the same number of soluble temporary plugging balls as the number of switch circulation holes 260 need to be used, eliminating the need for excessive ball use and reducing the cost of soluble temporary plugging ball consumables.

[0049] It should also be noted that the intermediate abutment in this embodiment can be removed by a retrieval tool (not shown in the figure) after construction is completed, or the material of the intermediate abutment can also be set to be soluble, and the dissolution time is required to be longer than the dissolution time of the soluble temporary plugging ball.

[0050] Specifically, to enable the sliding sleeve 250 to move downwards step by step within the valve body 200, in this embodiment, the valve body 200 is provided with an opening shear pin 230 and a closing shear pin 240 on its inner circumference, with the opening shear pin 230 positioned above the closing shear pin 240. An opening pin groove is provided on the upper outer circumferential wall of the sliding sleeve 250, and a first annular limiting step 270 is provided on the outer circumference of the sliding sleeve 250. A second annular limiting step 280 is provided on the inner wall of the valve body 200. When the initial tubing string 100 is not lowered into the well, one end of the opening shear pin 230 is located in the opening pin groove of the sliding sleeve 250. At this time, the switch circulation hole 260 on the sliding sleeve 250 is located above the main circulation hole 210 of the valve body 200, and the two are misaligned. When sand flushing, well washing, or pre-circulation is required... During the annular pretreatment operation, the operator applies pressure to the tubing string 100. The pressure acts on the upper end face of the sliding sleeve 250. When the pressure exceeds the preset shear load of the opening shear pin 230, the opening shear pin 230 breaks, and the sliding sleeve 250 loses its radial locking constraint. Under the downward pressure thrust of the liquid in the tubing string 100, it slides axially downward along the inner wall of the valve body 200 until the first limiting step on the outer periphery of the sliding sleeve 250 abuts against the closing shear pin 240 to achieve temporary limiting. At this time, the switching circulation hole 260 of the sliding sleeve 250 is completely overlapped with the main circulation hole 210 of the valve body 200. The inner cavity of the tubing string 100 is connected to the inner cavity of the casing of the oil well (not shown in the figure) to form a fluid circulation channel, which can carry out sand flushing, well washing, and pre-circulation pretreatment operations in the corresponding section.

[0051] After the single-layer circulation construction is completed, a matching number of soluble temporary plugging balls are inserted into the tubing string 100. The number of soluble temporary plugging balls is the same as the number of switching circulation holes 260. Relying on the flow-guiding and limiting action of the intermediate abutment and the liquid flow, the soluble temporary plugging balls seal all the switching circulation holes 260. After the internal space of the tubing string 100 is sealed, the pressure continues to rise. When the pressure inside the tubing string 100 exceeds the set shear pressure of the closing shear pin 240, the closing shear pin 240 breaks under force, and the sliding sleeve 250 loses its limiting and blocking action again and continues to move downwards. The valve body 200 moves until the first annular limiting step 270 abuts against the second annular limiting step 280 at the bottom of the valve body 200. At this time, the switch circulation hole 260 on the sliding sleeve 250 slides to the bottom of the main circulation hole 210 of the valve body 200. The switch circulation hole 260 and the main circulation hole 210 are completely misaligned again. The fluid circulation channel formed by the connection between the inner cavity of the tubing string 100 and the inner cavity of the casing (not shown in the figure) of the oil well is permanently isolated. The valve body 200 no longer has the ability to conduct circulation, thus completing the single-layer isolation operation.

[0052] It should be noted that in this embodiment, the number of main circulation holes 210 on the valve body 200 and the number of switch circulation holes 260 on the sliding sleeve 250 of the multiple soluble temporary plugging ball switching full-bore circulation valves for oil casing are different, specifically increasing from top to bottom. For example, the uppermost valve body 200 has three main circulation holes 210 and the sliding sleeve 250 has three switch circulation holes 260, while the adjacent lower valve body 200 has four main circulation holes 210 and the sliding sleeve 250 has four switch circulation holes 260, with the number increasing sequentially. During the sand flushing, well washing, and pre-circulation pretreatment of the uppermost well wall, three soluble temporary plugging balls need to be deployed. After the construction of this layer is completed, when the next layer needs to be constructed, four soluble temporary plugging balls need to be deployed, and the number of soluble temporary plugging balls deployed subsequently increases sequentially.

[0053] It is understandable that by setting an increasing number of main circulation holes 210 and switch circulation holes 260, the soluble plugging balls can be used for sand flushing, well washing, and pre-circulation pretreatment operations on the next layer of well wall even when they are not completely dissolved. Since the number of soluble plugging balls required for each layer increases sequentially, the switch circulation holes 260 on the next layer's sliding sleeve 250 will not be completely blocked when the soluble plugging balls in the previous layer are not completely dissolved, thereby reducing waiting time and eliminating the traditional process of having to wait for all the soluble plugging balls to dissolve before the next layer can be constructed, thus shortening the overall operation cycle.

[0054] Specifically, in this embodiment, the intermediate abutment includes a sealing post 300 and a conical top cover 320. The sealing post 300 is axially slidably sealed within the sliding sleeve 250. The conical top cover 320 is fixedly connected to the upper end of the sealing post 300, with the small end 340 of the conical top cover 320 facing upwards and the large end 350 of the conical top cover 320 able to abut against the interior of the sliding sleeve 250 or the inner wall of the valve body 200. Furthermore, arc-shaped plates 330 are evenly arranged circumferentially on the conical surface of the conical top cover 320, with adjacent arc-shaped plates 330... An arc-shaped groove is formed between 30. The arc-shaped groove is used to guide the soluble temporary plugging ball to seal the switch circulation hole 260. When the soluble temporary plugging ball enters the tubing 100, it will fall on the arc-shaped groove on the surface of the conical top cover 320. At the same time, when the liquid flows through the switch circulation hole 260 and the main circulation hole 210, it will form a local fluid disturbance at the arc plate 330, which will drive the soluble temporary plugging ball to slide circumferentially along the conical surface, so that the soluble temporary plugging ball can quickly correspond to the orifice position of each switch circulation hole 260, thereby improving the sealing success rate.

[0055] It should be noted that, compared to traditional soluble temporary plugging balls that rely solely on the guiding effect of liquid flowing through the switch circulation hole 260, which is prone to plugging failure and requires the use of a large number of plugging balls, the arc-shaped groove in this embodiment can circumferentially disturb the liquid, and together with the bottoming effect of the conical top cover 320, the soluble temporary plugging balls gradually approach the switch circulation hole 260. Only the same number of soluble temporary plugging balls as the number of switch circulation holes 260 are needed to successfully plug the hole, thus saving the number of soluble temporary plugging balls used and achieving a higher plugging success rate.

[0056] In a further embodiment, the conical top cover 320 of this embodiment is elastic and can undergo elastic deformation. A third annular limiting step 290 is provided within the sliding sleeve 250. When the conical top cover 320 is not deformed, the large end 350 of the conical top cover 320 is located on the third annular limiting step 290, and the outer diameter of the large end 350 of the conical top cover 320 is larger than the inner diameter of the third annular limiting step 290. When the sliding sleeve 250 moves downwards to shear off the closing shear pin 240, it continues to move downwards and abuts against the third annular limiting step 290. At this time, the inner circumference of the sliding sleeve 250 pushes against the large end 350 of the conical top cover 320, causing the conical top cover 320 to elastically contract. Since the inner diameter of the sliding sleeve 250 is the same as the inner diameter of the third annular limiting step 290, this allows the conical top cover 320 to elastically contract. The outer diameter of the large end 350 of the conical top cover 320 is the same as the inner diameter of the third annular limiting step 290. As the pressure inside the tubing string 100 gradually increases, it can push the conical top cover 320 and the sealing column 300 to move downwards synchronously. When it moves to the bottom of the sliding sleeve 250 of the next valve body 200, the large end 350 of the conical top cover 320 disengages from the sliding sleeve 250. At this time, the conical top cover 320 elastically resets. The outer diameter of the large end 350 of the conical top cover 320 is larger than the inner diameter of the third annular limiting step 290 inside the next valve body 200. The large end 350 of the conical top cover 320 is repositioned on the third annular limiting step 290 inside the next valve body 200. This provides a guide for the soluble temporary plugging ball to seal the switch circulation hole 260 on the next sliding sleeve 250 during the construction of the next layer of the well wall.

[0057] In a further embodiment, to improve the sealing performance of the intermediate abutment, a vulcanized rubber sleeve 310 is provided on the outer periphery of the sealing post 300 of the intermediate abutment in this embodiment. The outer edge of the vulcanized rubber sleeve 310 is tightly fitted with the inner peripheral wall of the sliding sleeve 250, realizing a dynamic sealing fit between the sealing post 300 and the inner wall of the sliding sleeve 250. The vulcanized rubber sleeve 310 can block the high-pressure working fluid inside the tubing 100, preventing fluid from leaking downwards through the annular gap between the sealing post 300 and the sliding sleeve 250, ensuring that the pressure inside the tube can be effectively established during the ball-throwing and pressure-building stage, ensuring that the closing shear pin 240 can be smoothly sheared under the preset pressure, and ensuring that the downward closing action of the sliding sleeve 250 is reliably executed.

[0058] In a further embodiment, the valve body 200 of the present invention is provided with a balance hole 220. The balance hole 220 is located above the main circulation hole 210. The balance hole 220 is a through hole that obliquely penetrates the side wall of the valve body 200. Its inner opening connects to the annular gap between the valve body 200 and the inner cavity of the sliding sleeve 250 (the annular gap is formed by the cavity between the first annular limiting adjustment and the second annular limiting step 280). Its outer opening directly connects to the space between the outer periphery of the outer valve body 200 and the inner cavity of the sleeve. During the lowering of the tubing string 100, the balance hole 220 helps to keep the pressure at the upper end of the sliding sleeve 250 basically consistent with the annular pressure on the outside of the sliding sleeve 250 (the annular pressure refers to the pressure between the outer periphery of the valve body 200 and the inner cavity of the casing). This counteracts the axial pressure difference generated by the hydrostatic column in the wellbore, eliminates the additional load of the hydrostatic column on the opening shear pin 230, avoids the sliding sleeve 250 from being malfunctioning due to the pressure difference of the hydrostatic column during the lowering of the tubing string 100, and prevents the opening shear pin 230 from shearing prematurely, causing abnormal valve opening.

[0059] Specifically, in this embodiment, a filter screen is also installed at the opening of the balance hole 220. The filter screen is fixedly embedded on the outside of the channel of the valve body 200, which can prevent formation sand and solid impurities in the wellbore from entering the interior of the balance hole 220, prevent the balance hole 220 from being blocked by solid particles and losing its pressure balance function, and ensure that the pressure balance channel is unobstructed during the entire well section operation.

[0060] It should be noted that the valve body 200 in this embodiment is made of 42CrMo alloy steel, is hollow, and has standard tubing 100 connecting threads at both ends. The inclined balance hole 220 on the side wall of the valve body 200 has a diameter of 6mm, and a stainless steel filter screen is installed inside the hole. The main circulation holes 210 evenly distributed around the circumference of the valve body 200 have a single hole diameter of 12mm, and the switch circulation hole 260 of the sliding sleeve 250 also has a single hole diameter of 12mm. The minimum inner diameter of the valve body 200 is the same as the inner diameter of the sliding sleeve 250. The valve maintains a complete and unobstructed flow throughout the opening and closing process. After the soluble temporary plugging ball dissolves, there is no narrowing or jamming point. Downhole tools such as logging, fracturing, and workover can pass smoothly without throttling obstruction. The opening shear pin 230 and closing shear pin 240 use H62 shear pins, and the pin cross-sectional size can be adjusted as needed; the opening shear pressure of a single valve body 200 can be customized in the range of 10-16MPa, and the closing shear pressure range is 13-19MPa; when multiple valve bodies 200 are used in series, taking three valve bodies 200 in series as an example, the opening pressure of the uppermost valve body 200 is 10MPa, the opening pressure of the middle valve body 200 is 13MPa, and the opening pressure of the deepest valve body 200 is 16MPa, with the pressure increasing step by step.

[0061] It should also be noted that the soluble plugging ball in this embodiment is made of a polymer composite soluble material with an outer diameter of 18 mm. The outer diameter of the ball is larger than that of the switch circulation hole 260, which can stably seal the switch circulation hole 260. The density of the ball is adjusted to be close to that of water and guar gum fracturing fluid.

[0062] The specific working process of the oil casing soluble temporary plugging ball switch full-bore circulation valve provided by the present invention will be described in conjunction with the above embodiments:

[0063] Before construction, multiple sets of the circulation valves of this invention are connected in series on the working tubing string 100 in a manner that increases the opening pressure and the number of circulation holes in a stepwise manner. Each valve body 200 corresponds to a different reservoir well section, and works with interlayer packers to ensure that the annular space of each layer is independent of each other, thus avoiding interlayer interference.

[0064] The valve body 200 is lowered into the wellbore along with the tubing string 100. During the entire lowering process, the balance hole 220 on the side wall of the valve body 200 is connected in real time to the annular gap on the outer side of the sliding sleeve 250 and the casing annulus, so that the pressure in the tubing at the upper end of the sliding sleeve 250 is balanced with the pressure in the outer annulus in real time. This avoids malfunctions such as accidental movement of the sliding sleeve 250, premature shearing of the shear pin, and abnormal opening of the valve during the lowering of the tubing string 100. At the same time, the stainless steel filter screen installed on the outer side of the balance hole 220 can continuously block formation sand and solid impurities, prevent the balance hole 220 from becoming blocked, and ensure the stability and effectiveness of the pressure balance structure throughout the process.

[0065] After the tubing string 100 is lowered into place, the sliding sleeves 250 inside each valve body 200 are kept in the upper initial position under the radial locking action of the open shear pin 230. The switch circulation hole 260 of the sliding sleeve 250 is completely misaligned with the main circulation hole 210 of the valve body 200, and each reservoir section remains in a closed and isolated state.

[0066] When the layered operation is officially carried out, according to the graded pressure design of shallow low pressure and deep high pressure, the surface pump set pumps sand flushing fluid, well washing fluid or fracturing pre-fracturing fluid into the tubing string in stages, and the independent construction of each layer is achieved through step-by-step pressure increase. First, the tubing string 100 is pressurized. When the pump pressure reaches the preset opening pressure of the uppermost valve body 200, the opening shear pin 230 of this valve body 200 breaks under shear, and the sliding sleeve 250 loses its radial locking constraint. Under the thrust of the fluid pressure difference in the pipe, it moves axially downward along the inner wall of the valve body 200 until the first annular limiting step 270 on the outer wall of the sliding sleeve 250 abuts against the closing shear pin 240 to complete temporary limiting. At this time, the switching circulation hole 260 of the sliding sleeve 250 and the main circulation hole 210 of the valve body 200 are completely aligned, and the inner cavity of the tubing string 100 is connected to the casing annulus, establishing a stable circulation channel. The working fluid pumped in from the surface can flow into the casing annulus through the inner cavity of the tubing string 100, the switching circulation hole 260, and the main circulation hole 210, and then be discharged upwards, completing the sand flushing, well washing, and pre-circulation pretreatment operations for this section. During this process, the lower valve body 200, due to its higher opening pressure, does not reach the shear threshold and remains closed, thus not interfering with the upper construction.

[0067] After a single-layer circulation operation is completed, an equal amount of polymer soluble temporary plugging balls are added into the tubing 100 according to the number of circulation holes in the valve body 200 of that layer. The soluble temporary plugging balls fall down with the fluid in the tubing 100 and land on the intermediate abutment in the inner cavity of the valve body 200. Relying on the conical guide structure of the conical top cover 320 and the circumferentially arranged arc plate 330, the fluid flows through the arc plate 330 and forms a local disturbance, guiding the soluble temporary plugging balls to accurately align and seal all the switch circulation holes 260. Compared with the traditional disordered ball throwing method, this invention can significantly reduce the number of balls thrown and improve the sealing efficiency.

[0068] After the soluble temporary plugging ball completely seals the switch circulation hole 260, the fluid inside the tubing 100 cannot flow outward, and the pressure inside the tubing 100 continues to rise. When the pressure reaches the preset shear load of the closing shear pin 240, the closing shear pin 240 breaks, the sliding sleeve 250 releases the secondary limit, and continues to descend axially under the action of fluid pressure difference until the first annular limit step 270 abuts against the second annular limit step 280 at the bottom of the valve body 200. At this time, the switch circulation hole 260 slides to the bottom of the main circulation hole 210, and the two are completely misaligned again. The circulation channel is permanently sealed, completing the isolation and sealing of this reservoir layer.

[0069] During the downward compression and closing of the shear pin 240 by the sliding sleeve 250, the lower end of the sliding sleeve 250 compresses the elastic conical top cover 320, causing the conical top cover 320 to undergo radial contraction deformation and disengage from the limiting engagement with the third annular limiting step 290 of the sliding sleeve 250. The overall intermediate abutment can move downward with the well fluid and automatically engage with the next stage valve body 200. After the conical top cover 320 elastically resets, it re-supports and limits the position, and can be reused as the flow guide ball structure for the next stage of construction. No additional tools are required, and the components can be reused. Meanwhile, the multi-stage valve body 200 adopts a design that increases the number of circulation holes from top to bottom. A small amount of residual soluble temporary plugging balls that have not completely dissolved after the upper layer construction cannot completely block the more numerous switching circulation holes 260 in the lower layer. Therefore, there is no need to wait for the soluble temporary plugging balls to completely dissolve. The pump pressure can be directly increased to the opening pressure of the next layer valve body 200 to open the lower layer circulation channel and carry out continuous construction operations. This eliminates the long standing waiting process of traditional processes and greatly shortens the construction cycle.

[0070] Throughout the operation, the vulcanized rubber sleeve 310 on the outer wall of the intermediate abutment sealing column 300 forms a sliding seal structure, which can prevent high-pressure fluid from leaking downwards from the gap between the sliding sleeve 250 and the sealing column 300, ensuring stable pressure establishment inside the pipe during the pressure build-up process, and ensuring precise and controllable shearing pressure of the shear pin and stable and reliable opening and closing action of the sliding sleeve 250. By repeating the above-mentioned procedures of pressurizing and opening the valve, circulating operation, and dropping the ball to build up pressure and close the valve, the layered sand flushing, well washing, and pre-treatment operations of all reservoir sections can be completed sequentially from top to bottom. Ultimately, it can achieve precise, continuous, and efficient downhole layered construction with one trip of tubing string 100 and multiple layers. After the operation is completed, the soluble temporary plugging ball completely dissolves in the wellbore fluid, with no hard residue remaining in tubing string 100, ensuring unobstructed flow throughout the tubing string 100, and providing good wellbore conditions for subsequent logging, workover, fracturing, and other operations.

[0071] This invention also provides a method for using a soluble temporary plugging ball switch full-bore circulation valve for oil casing, which requires the aforementioned soluble temporary plugging ball switch full-bore circulation valve for oil casing and includes the following steps:

[0072] Step S1: According to the number of reservoir sections, connect the valve body 200 with the opening pressure increasing step by step to the pipe column 100 from top to bottom, and ensure that the valve is closed due to the initial misalignment of the valve channel after assembly.

[0073] Based on the number of vertical reservoir segments in the oil and gas well, multiple sets of valve bodies 200 with corresponding pressure levels and circulation holes are selected. Following an assembly sequence that increases from top to bottom in terms of opening pressure and the number of main circulation holes 210, these valve bodies 200 are connected in series on the tubing string 100. After assembly, each valve body 200 is checked to ensure that the internal sliding sleeve 250, opening shear pin 230, closing shear pin 240, intermediate abutment, and vulcanized rubber sleeve 310 are properly assembled, and that the balance hole 220 filter is unobstructed. It is ensured that the opening and closing circulation holes 260 and main circulation holes 210 of all valve bodies 200 are completely misaligned in their initial state, and that the valves are in a closed, ready-to-operate state. The tubing string 100 is then smoothly lowered into the designed wellbore position. During this process, the balance holes 220 of the valve bodies 200 continuously balance the pressure inside and outside the sliding sleeve 250, counteracting the hydrostatic pressure difference and preventing premature tool opening.

[0074] Step S2: After the tubing string 100 is in place, the working fluid is pumped in and the pressure is gradually increased. After the valve body 200 reaches the opening pressure, the sliding sleeve 250 moves down to open the circulation hole, establishes the circulation channel, and completes the single-layer sand flushing, well washing and fracturing pretreatment operations.

[0075] After tubing string 100 is lowered into place, the surface pump unit pumps well-washing fluid, sand-flushing fluid, or fracturing pre-fracturing fluid into the tubing string 100. Through a stepped pressurization method, pump pressure is preferentially applied to the uppermost low-pressure valve body 200. When the pressure inside tubing string 100 reaches the preset shear pressure of the upper valve body 200's opening shear pin 230, the opening shear pin 230 breaks, and the sliding sleeve 250 is limited to its downward movement under the pressure differential. The switch circulation hole 260 completely overlaps with the main circulation hole 210, establishing a circulation channel between the tubing and casing annulus. Working fluid is continuously pumped in to perform circulating sand flushing, well-washing, wellbore cleaning, and pre-circulation pretreatment on this reservoir section, thoroughly removing wellbore sediment, oil, and construction residue, completing the single-layer wellbore cleaning operation.

[0076] Step S3: After the single-layer operation is completed, the same number of soluble temporary plugging balls as the switch circulation holes 260 are added. The switch circulation holes 260 are blocked by the intermediate abutment. The pressure continues to increase and push the sliding sleeve 250 down to block the main circulation hole 210. The intermediate abutment moves down and is reused in the lower valve body 200.

[0077] After the single-layer circulation operation meets the standard, an equal amount of soluble temporary plugging balls are added according to the number of switching circulation holes 260 in the current layer valve body 200. The soluble temporary plugging balls descend with the fluid and enter the interior of the valve body 200. Under the guiding, limiting, and turbulence effects of the intermediate abutment conical top cover 320 and the circumferential arc plate 330, all switching circulation holes 260 are precisely sealed. After sealing, the fluid in the tubing 100 cannot leak out, and the pump pressure continues to rise. When the pressure reaches the shear threshold of the closing shear pin 240, the closing shear pin 240 breaks, and the sliding sleeve 250 descends again to the second annular limiting step 280 of the valve body 200 for limiting. The switching circulation hole 260 and the main circulation hole 210 are misaligned again, and the circulation channel of this layer is permanently closed. During the descent of the sliding sleeve 250, the conical top cover 320 is squeezed to cause it to elastically contract, and the intermediate abutment moves down with the fluid and is stuck into the interior of the next-stage valve body 200 for reuse. Meanwhile, relying on the multi-stage valve body 200 switch circulation hole 260 with the structure design of increasing from top to bottom, the undissolved spheres in the upper layer cannot block more holes in the lower layer. There is no need to wait for the soluble temporary plugging spheres to completely dissolve, and the next layer of continuous construction can be carried out directly, effectively shortening the operation cycle.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A full-bore circulation valve for oil casing with soluble temporary plugging ball switch, characterized in that, include: The valve body is hollow inside and connected to the tubing at both ends. Multiple main circulation holes are evenly opened circumferentially on the circumferential wall of the valve body. A sliding sleeve is axially slidably arranged inside the valve body. The inner diameter of the sliding sleeve is the same as the inner diameter of the tubing. Multiple switching circulation holes are evenly opened circumferentially on the circumferential wall of the sliding sleeve. The sliding sleeve is configured to move downward step by step as the internal pressure of the tubing increases, so that the main circulation holes and the switching circulation holes are staggered, overlapped, and staggered again. A soluble temporary plugging ball is located inside the sliding sleeve. The soluble temporary plugging ball is configured to be inserted into the sliding sleeve when it is necessary to close the main circulation hole, and the number of inserted balls is the same as the number of switching circulation holes. An intermediate abutment is axially slidably disposed within the valve body, and the intermediate abutment is configured to guide the soluble temporary plugging ball to block the switch circulation hole when the ball enters the valve body.

2. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 1, characterized in that, The valve body is provided with an opening shear pin and a closing shear pin on its inner periphery, with the opening shear pin located above the closing shear pin; The upper outer peripheral wall of the sliding sleeve is provided with an opening pin groove, the outer periphery of the sliding sleeve is provided with a first annular limiting step, and the inner wall of the valve body is provided with a second annular limiting step. When the opening shear pin is located in the opening pin groove, the switch circulation hole is located above the main circulation hole. When the first annular limiting step abuts against the closing shear pin, the switch circulation hole coincides with the main circulation hole. When the first annular limiting step abuts against the second annular limiting step, the switch circulation hole is located below the main circulation hole.

3. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 1, characterized in that, The intermediate abutment includes a sealing column and a conical top cover. The sealing column is axially slidably sealed inside the sliding sleeve. The conical top cover is fixedly connected to the upper end of the sealing column, with the small end of the conical top cover facing upwards and the large end of the conical top cover abutting against the inner circumferential wall of the sliding sleeve or the inner wall of the valve body. The conical surface of the conical top cover is uniformly provided with arc-shaped plates in the circumferential direction, and an arc-shaped groove is formed between adjacent arc-shaped plates. The arc-shaped groove is used to guide the soluble temporary plugging ball to seal the switch circulation hole.

4. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 3, characterized in that, The valve body has a third annular limiting step on its inner circumference at the bottom. The conical top cover is elastic, and the outer diameter of the conical top cover after its large end is recessed is equal to the inner diameter of the third annular limiting step.

5. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 3, characterized in that, A vulcanized rubber sleeve is provided on the outer periphery of the sealing column.

6. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 1, characterized in that, The valve body has a balance hole, which is located above the main circulation hole.

7. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 6, characterized in that, A filter screen is installed on the balance hole.

8. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 1, characterized in that, The valve body is made of 42CrMo alloy steel, is hollow, and has standard pipe thread at both ends.

9. The oil casing soluble temporary plugging ball switch full-bore circulation valve according to claim 1, characterized in that, The valve body has a single-hole diameter of 12mm for the main circulation holes evenly distributed around its circumference, and the single-hole diameter of the switch circulation holes of the sliding sleeve is also 12mm. The minimum inner diameter of the valve body is the same as the inner diameter of the sliding sleeve.

10. A method of using a soluble temporary plugging ball switch full-bore circulation valve for oil casing, requiring the use of the soluble temporary plugging ball switch full-bore circulation valve for oil casing as described in any one of claims 1-9, characterized in that, Includes the following steps: Step S1: According to the number of reservoir sections, connect the valve body with progressively increasing opening pressure from top to bottom in series with the connecting pipes. After assembly, ensure that the valve's initial orifice is misaligned and closed. Step S2: After the tubing string is in place, pump in the working fluid and gradually increase the pressure. After the valve body reaches the opening pressure, the sliding sleeve moves down to open the circulation hole, establishes the circulation channel, and completes the single-layer sand flushing, well washing and fracturing pretreatment operations. Step S3: After the single-layer operation is completed, the same number of soluble temporary plugging balls as the switch circulation holes are added. The switch circulation holes are blocked by the intermediate abutment. The pressure is increased to push the sliding sleeve down to block the main circulation holes. The intermediate abutment is moved down and reused in the next stage valve body.

Images