Sidetracking small casing reverse circulation well cementation tubular column

Abstract

The utility model discloses a sidetrack small casing reverse circulation well cementation pipe column which comprises a small casing, a bridge type injection reverse discharge mechanism and a lifting closed flow-back valve. The upper end of the small casing pipe is connected with the lower end of the bridge type injection reverse discharge mechanism through a releasing mechanism, and the lower end of the small casing pipe is provided with a lifting closing flow-back valve. The pipe column is provided with the bridge type channel, redundant liquid can be effectively discharged, air can be discharged and squeezed out, it can be guaranteed that cement flows to the bottom to fill the small casing pipe ring for well sections with serious leakage, and the well cementation depth of the cement is judged through ground pressure changes and the reverse liquid outlet amount. The well cementation quality can be improved, the operation time is shortened, and the operation safety is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to downhole tool technical field, concretely is a kind of lateral drilling small casing reverse circulation well cementation pipe column. BACKGROUND

[0002] With oilfield entering later period, the number of casing damage well increases year by year, casing damage degree is increasingly intensified, and the main casing damage well type is mainly four categories such as casing shrinkage, bending, leakage, breakage etc.For these casing damage well conditions, when unable to realize taking and replacing casing construction, the most effective method is to lower small casing after the original well is modified, and form new complete wellbore.

[0003] The conventional well cementation process method process is to lower small casing to predetermined depth, and the upper end of small casing is hung in the original well casing through hydraulic hanger;During well cementation, cement slurry is injected into the pipe column, and the cement slurry is displaced to the space between the wellbore and the casing using a rubber plug;Reverse sealing is used by float collar and float shoe ball seat, so that the cement slurry displaced to the annulus cannot flow back, and after a certain period of time, the cement slurry solidifies to form a cement sheath, which separates oil, gas and water layers;This positive circulation cementation cannot guarantee the quality of casing cementation above the leakage point or oil layer, and circulation cannot be established;Circulation cementation does not have sealing elements in the hanger, and the amount of cement extrusion must be accurately calculated, otherwise, if the amount of cement extrusion is excessive, the small diameter oil in the small casing may cause the pipe string to be stuck, and the ground cannot accurately determine whether the cement is in place, which affects the quality of well cementation;The bottom of the positive rotation cementation adopts a support collar and a float shoe, and the liquid outside the casing cannot enter the oil pipe during the lowering process, and when the ground injects liquid, the gas in the oil pipe will partially extrude the annulus of the small casing, which affects the quality of well cementation.

[0004] Announcement No. CN115247545B discloses a kind of pressure transmission tools and methods for cementing well without drilling plug, tool includes center tube, outer sleeve assembly, upper skin bowl assembly, lower skin bowl assembly;The outer sleeve assembly is assembled outside the center tube, the upper end of the outer sleeve assembly is installed with the upper skin bowl assembly, and the lower end of the outer sleeve assembly is installed with the lower skin bowl assembly;The center tube and the outer sleeve assembly are simultaneously provided with radial pressure transmission holes, and the radial pressure transmission holes can be communicated with the liquid inlet hole of open hole packer;The center tube and the outer sleeve assembly have axial passage, the upper end of the axial passage can be communicated with the space above the upper skin bowl assembly, the lower end of the axial passage can be communicated with the space below the lower skin bowl assembly, and the axial passage can also be communicated with the radial pressure transmission hole simultaneously.It can realize that after casing is lowered into open hole packer cementing, the pressure transmission tool is lowered into the casing through oil pipe, the intermediate skin bowl cavity seals open hole packer liquid inlet hole, and on the basis of ensuring that open hole packer is effectively seated, residual cement slurry in casing is cleaned.

[0005] The disclosure No. CN118223820A discloses a small hole screen pipe completion string and construction method, the circulation assembly structure adopts a double-opening piston design, the opening sleeve moves by the pressure generated by the piston area difference, and in cooperation with the pin control, a higher setting pressure difference can be provided for the string packer; the throttle sliding sleeve opening seal commonly uses a rubber ring soft material seal, the lower end of the throttle sliding sleeve is provided with a 30-degree chamfer and a spherical surface on the upper part of the lower joint to form a steel sealing cooperation, which can effectively avoid the problem of rubber ring falling off in the cementing process caused by the piston, which affects the whole cementing operation, needs rework, causes significant economic loss.

[0006] The publication No. CN114320218B discloses a drill plug-free well cementing device, when the opening sleeve drives the closing sleeve to overcome the bearing force of the first pin through tubing pressurization, the closing sleeve can slide downward along the central pipe until the first circulation hole, the second circulation hole and the third circulation hole are coaxial, so that the well cementing fluid in the tubing can flow into the three circulation holes, since the central pipe is provided with a setting sleeve, there is a setting flow channel between the central pipe and the setting sleeve, the setting flow channel communicates with the first circulation hole, so that the well cementing fluid passing through the circulation hole can be introduced thereinto, and finally flows into the gap between the inner liner pipe and the setting rubber sleeve, to complete the setting and further perform the well cementing operation. At the same time, the well cementing fluid can also enter the annulus between the tubing and the casing through the circulation hole, and is discharged back to the wellhead through the annulus, to flush the sandstone in the wellbore, facilitating subsequent well cementing.

[0007] The above-mentioned prior art is all positive injection, and the well cementing quality cannot be guaranteed, which is not as good as the utility model.

[0008] In summary, the technical solutions of the above-mentioned disclosed technologies, the technical problems to be solved and the beneficial effects produced are all different from those of the utility model, and the above-mentioned disclosed technology documents do not have technical inspiration for more technical features and technical problems to be solved and beneficial effects of the utility model. Utility model content

[0009] In view of the above-mentioned defects of the prior art, the purpose of the utility model is to provide a sidetracking small casing reverse circulation well cementing string.

[0010] In order to achieve the above-mentioned purpose, the utility model adopts the following technical solutions:

[0011] A sidetracking small casing reverse circulation well cementing string, comprising a small casing, further comprising a bridge type injection and back flushing mechanism, and an up-drawing closed back flushing valve; the upper end of the small casing is connected with the lower end of the bridge type injection and back flushing mechanism through a drop-off mechanism, and the lower end of the small casing is provided with the up-drawing closed back flushing valve.

[0012] Further, the bridge type injection reverse displacement mechanism comprises a setting mechanism, the setting mechanism comprises an upper joint, a rubber cylinder shaft, a rubber cylinder, a cylinder barrel, the outer wall of the upper end of the rubber cylinder shaft is threadedly connected with the inner wall of the upper joint, the outer wall of the lower end of the rubber cylinder shaft is connected with the upper end of the small casing through a setting shear pin, and the rubber cylinder is sleeved on the outer wall of the rubber cylinder shaft.

[0013] Further, the bridge type injection reverse displacement mechanism further comprises an upper central pipe, a lower central pipe and a bridge pipe.

[0014] Specifically, the inner wall of the upper joint is provided with an inner convex ring, the upper end of the upper central pipe is connected with the inner wall of the inner convex ring, and the upper joint is provided with a top discharge hole.

[0015] Specifically, the inner wall of the bridge pipe is provided with a bridge type flow ring, the bridge type flow ring is provided with a radial through inner injection hole and an axial through bridge type through hole, the outer wall of the lower end of the upper central pipe is sealingly connected with the inner wall of the upper end of the bridge type flow ring, the outer wall of the upper end of the lower central pipe is sealingly connected with the inner wall of the lower end of the bridge type flow ring, and the bottom of the lower central pipe is closed.

[0016] Specifically, the bridge pipe is provided with an upper discharge channel between the upper central pipe above the bridge type flow ring and the bridge pipe, and is provided with a lower discharge channel between the lower central pipe below the bridge type flow ring.

[0017] Specifically, a sealing element is arranged between the cylinder barrel and the bridge pipe below the inner injection hole, the cylinder barrel is provided with an outer injection hole between the rubber cylinder shaft and the sealing element, and the inner injection hole and the outer injection hole communicate the space in the central pipe with the outside of the pipe string.

[0018] Further, the dropping mechanism comprises a piston and a split connection pipe.

[0019] Specifically, the sealing element is the piston, the inner wall of the piston is in contact with and seals the outer wall of the bridge pipe, the outer wall of the piston is in contact with and seals the cylinder barrel, and the lower end of the piston is provided with an anti-falling ring.

[0020] Specifically, the split connection pipe is sleeved on the outer wall of the anti-falling ring, the outer wall of the upper end of the split connection pipe is connected with the inner wall of the lower end of the cylinder barrel, the lower end of the split connection pipe is in a split structure, the outer wall of the split section of the split connection pipe is provided with a locking block, and the locking block is embedded with the inner wall of the lower end of the small casing.

[0021] Specifically, the outer wall of the anti-falling ring is provided with a pressure ring, the outer diameter of the pressure ring is the same as the normal inner diameter of the split section, which is used to prevent the split section from shrinking, and the outer wall of the anti-falling ring is provided with an unlocking groove above the pressure ring, which is used to restore the shrinking ability of the split section.

[0022] Further, the up-closing backflow valve comprises a valve body, an elastic sealing sleeve, a spigot, and a guide head;

[0023] Specifically, the upper end of the valve body is connected with the lower end of the small sleeve, and the inner wall of the valve body is provided with an upper sealing ring and a lower sealing ring.

[0024] Specifically, the elastic sealing sleeve is slidably inserted into the valve body, the outer wall of the elastic sealing sleeve is sealed with the upper sealing ring and the lower sealing ring, and the elastic sealing sleeve is provided with an inner discharge hole.

[0025] Specifically, the elastic sealing sleeve is provided with a downward clamping split block and an upward clamping split block, the inner wall of the valve body is provided with a lower stop groove corresponding to the downward clamping split block, and the inner wall of the valve body is provided with an upper stop groove corresponding to the upward clamping split block.

[0026] Specifically, the upper end of the spigot is connected with the lower end of the bridge pipe, the lower end of the spigot is provided with a guide head, the outer diameter of the spigot is smaller than the inner diameter of the elastic sealing sleeve, the side wall of the spigot is provided with a flow hole, and the guide head can contact the inwardly retracted downward clamping split block and the upward clamping split block; when the downward clamping split block is clamped with the lower stop groove, the inner discharge hole is located between the upper sealing ring and the lower sealing ring; when the upward clamping split block is clamped with the upper stop groove, the inner discharge hole is located above the upper sealing ring, and the up-closing backflow valve is closed.

[0027] Further, the lower end of the up-closing backflow valve is connected with a filter pressure control mechanism.

[0028] Specifically, the filter pressure control mechanism comprises a slotted screen pipe, a lower connector, and a one-way valve.

[0029] Specifically, the outer wall of the valve body is provided with an outer connecting ring above the lower discharge hole, the inner wall of the upper end of the slotted screen pipe is connected with the outer wall of the outer connecting ring, the lower end of the slotted screen pipe is connected with the lower connector, the lower connector is provided with a bottom discharge hole, and the one-way valve is arranged at the upper end of the bottom discharge hole.

[0030] Further, the outer wall of the upper central pipe is provided with a variable diameter step to form a large diameter part and a small diameter part, the outer diameter of the lower central pipe is the same as the small diameter part of the upper central pipe, the inner diameter of the bridge flow ring is smaller than the inner diameter of the bridge pipe, the upper end of the bridge pipe is connected with the large diameter part of the upper central pipe, the bridge pipe is provided with an upper discharge hole between the outer convex ring and the large diameter part of the upper central pipe, the space between the upper discharge hole, the small diameter part of the upper central pipe, and the bridge pipe is an upper discharge channel, and the space between the lower central pipe and the bridge pipe is a lower discharge channel.

[0031] Further, the bridge pipe is provided with an expanding groove above and below the bridge flow ring, and the sum of all bridge pipe through hole areas is greater than or equal to the area of the lower central pipe and the bridge pipe annulus; the sum of all upper discharge hole areas is greater than the area of the upper central pipe small diameter part and the bridge pipe annulus.

[0032] Further, the rubber tube is provided with at least two, and a spacer ring is arranged between each two rubber tubes.

[0033] Further, the one-way valve comprises a sheath, a spring and a sealing rod.

[0034] The lower end of the sheath is connected with the upper end of the inner wall of the lower joint, the spring and the sealing rod are arranged in the sheath, the spring pushes the sealing rod on the bottom discharge hole, and the sheath is provided with a liquid passing through hole.

[0035] Compared with the prior art, the utility model has the following beneficial effects:

[0036] 1. The utility model changes the current positive circulation well cementing technology, adopts the reverse circulation well cementing technology, makes the cement enter the small casing annulus below the pipe string sealing point, the cement liquid flows downward under the gravity and pressure, and the reverse liquid is filtered through the bottom slotting screen pipe and discharged to the ground.

[0037] 2. The pipe string is provided with a bridge channel, can effectively remove excess liquid, can discharge and extrude air, and can also ensure the cement to flow to the bottom and fill the small casing annulus for the well section with serious leakage.

[0038] 3. The utility model can improve the well cementing quality, reduce the operation time and improve the operation safety. DRAWINGS

[0039] Fig. 1 It is a structure schematic view of the utility model of the side drilling small casing reverse circulation well cementing pipe string.

[0040] Fig. 2 It is a structure schematic view of the bridge flow ring in the utility model.

[0041] In the drawing: 1, upper joint; 1.1, top discharge hole;

[0042] 2, upper central pipe; 3, rubber tube shaft; 4, rubber tube; 5, spacer ring;

[0043] 6, bridge pipe; 6.1, upper discharge hole; 6.2, expanding groove;

[0044] 7, cylinder; 7.1, outer injection hole;

[0045] 8, seat seal shear pin; 9, rubber ring; 10, lower central tube; 11, piston; 12, split connecting tube; 13, small casing; 14, connecting sleeve;

[0046] 15, cannula; 15.1, flow hole;

[0047] 16, valve body; 16.1, lower discharge hole;

[0048] 17, elastic sealing sleeve; 17.1, inner discharge hole;

[0049] 18, sealing sleeve; 19, slotted screen pipe; 20, lead-in head; 21, sheath; 22, spring; 23, sealing rod; 24, lower joint;

[0050] 25, bridge type flow ring; 25.1, inner injection hole; 25.2, bridge type through hole. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0052] Embodiment 1:

[0053] Please refer to Figs. 1-2 The utility model provides a kind of side tracking small casing reverse circulation well cementation string, including small casing 13, bridge type injection reverse mechanism, the upper end of small casing 13 is connected with the lower end of bridge type injection reverse mechanism by releasing mechanism, and the lower end of small casing 13 is provided with upper lifting closed back flushing valve.

[0054] The bridge type injection reverse mechanism includes setting mechanism, and the setting mechanism includes upper joint 1, rubber cylinder shaft 3, rubber cylinder 4 and cylinder 7, the outer wall of the upper end of rubber cylinder shaft 3 is connected with the inner wall of upper joint 1 by screw thread, the outer wall of the lower end of rubber cylinder shaft 3 is connected with the upper end of small casing 13 by seat seal shear pin 8, and rubber cylinder 4 is sleeved on the outer wall of rubber cylinder shaft 3.

[0055] The bridge type injection backflow mechanism further comprises an upper central pipe 2, a lower central pipe 10, a bridge type pipe 6, an inner convex ring is arranged on the inner wall of the upper joint 1, the upper end of the upper central pipe 2 is threadedly connected with the inner wall of the inner convex ring, the upper joint 1 is provided with a top discharge hole 1.1, the top discharge hole 1.1 communicates the space between the upper central pipe 2 and the rubber sleeve shaft 3 with the outside of the pipe string; the bridge type pipe 6 is provided with a bridge type flow ring 25, the bridge type flow ring 25 is provided with a radial through inner injection hole 25.1 and an axial through bridge type through hole 25.2, the outer wall of the lower end of the upper central pipe 2 is sealingly connected with the inner wall of the upper end of the bridge type flow ring 25, the outer wall of the upper end of the lower central pipe 10 is sealingly connected with the inner wall of the lower end of the bridge type flow ring 25, the bottom of the lower central pipe 10 is closed, the bridge type pipe 6 is provided with an upper discharge channel between the part above the bridge type flow ring 25 and the upper central pipe 2, and is provided with a lower discharge channel between the part below the bridge type flow ring 25 and the lower central pipe 10; the outer wall of the bridge type pipe 6 is provided with an outer convex ring, the outer wall of the outer convex ring is in contact with and sealed with the inner wall of the rubber sleeve shaft 3, a sealing element is arranged between the cylinder 7 and the bridge type pipe 6 below the inner injection hole 25.1, the cylinder 7 is provided with an outer injection hole 7.1 between the rubber sleeve shaft 3 and the sealing element, and the inner injection hole 25.1 and the outer injection hole 7.1 communicate the space in the central pipe with the outside of the pipe string.

[0056] The clear water or cement is injected into the space below the rubber sleeve 4 of the pipe string through the inner injection hole 25.1 and the outer injection hole 7.1, and the displacement fluid is discharged to the space above the rubber sleeve 4 of the pipe string through the upper lifting closed backflow valve, the lower end port of the bridge type pipe 6, the lower discharge channel, the bridge type through hole 25.2, the upper discharge channel and the top discharge hole 1.1.

[0057] Specifically, the outer wall of the lower end of the rubber sleeve shaft 3 is provided with a stepped hanging connection with the inner wall of the upper end of the small sleeve pipe 13, so that the positioning assembly is facilitated.

[0058] Specifically, when the rubber sleeve 4 is provided with at least two, one spacer ring 5 is arranged between every two rubber sleeves 4.

[0059] Specifically, the bridge type pipe 6 is provided with a diameter expansion groove 6.2 above and below the bridge type flow ring 25, so that the hole diameter of the bridge type through hole 25.2 is increased, the sum of the areas of all the bridge type through holes 25.2 is greater than or equal to the area of the annulus between the lower central pipe 10 and the bridge type pipe 6, the sum of the areas of all the upper discharge holes 6.1 is greater than the area of the annulus between the small diameter part of the upper central pipe 2 and the bridge type pipe 6, and the resistance of the displacement fluid is reduced.

[0060] More specifically, the pipe section of the bridge type flow ring 25 of the bridge type pipe 6 is manufactured by precision casting, and is connected with the upper and lower inner diameter flat pipe sections by welding.

[0061] Specifically, the outer wall of the upper central pipe 2 is provided with a variable-diameter step, forming a large-diameter part and a small-diameter part, the outer diameter of the lower central pipe 10 is the same as the small-diameter part of the upper central pipe 2, the inner diameter of the bridge-type flow ring 25 is smaller than the inner diameter of the bridge-type pipe 6, the upper end of the bridge-type pipe 6 is threadedly connected with the large-diameter part of the upper central pipe 2, the bridge-type pipe 6 is provided with an upper discharge hole 6.1 between the outer convex ring and the large-diameter part of the upper central pipe 2, and the space between the upper discharge hole 6.1, the small-diameter part of the upper central pipe 2 and the bridge-type pipe 6 is an upper discharge channel, and the space between the lower central pipe 10 and the bridge-type pipe 6 is a lower discharge channel.

[0062] Specifically, the outer wall of the lower end of the upper central pipe 2 is sealingly inserted with the inner wall of the upper end of the bridge-type flow ring 25, and the outer wall of the upper end of the lower central pipe 10 is threadedly connected with the inner wall of the lower end of the bridge-type flow ring 25.

[0063] The drop hand mechanism includes a piston 11 and a split connecting pipe 12, the sealing member is the piston 11, the inner wall of the piston 11 is in contact with and sealed with the outer wall of the bridge-type pipe 6, the outer wall of the piston 11 is in contact with and sealed with the cylinder barrel 7, the lower end of the piston 11 is provided with an anti-falling ring, the split connecting pipe 12 is sleeved on the outer wall of the anti-falling ring, the outer wall of the upper end of the split connecting pipe 12 is threadedly connected with the inner wall of the lower end of the cylinder barrel 7, the lower end of the split connecting pipe 12 is in a split structure, the outer wall of the split section 13.1 of the split connecting pipe 12 is provided with a locking block, the locking block is embedded with the inner wall of the lower end of the small sleeve pipe 13, the outer wall of the anti-falling ring is provided with a pressure ring 12.1, the outer diameter of the pressure ring 12.1 is the same as the normal inner diameter of the split section 13.1, which is used to prevent the split section 13.1 from being retracted, and the outer wall of the anti-falling ring is provided with an unlocking groove 12.2 above the pressure ring 12.1, the unlocking groove 12.2 is used to restore the retraction ability of the split section 13.1; when the piston 11 moves downward under the action of pressure, the unlocking groove 12.2 coincides with the split section 13.1, the split connecting pipe 12 can be separated from the small sleeve pipe 13, and the drop hand is realized.

[0064] The up-closing backflow valve comprises a valve body 16, an elastic sealing sleeve 17, a cannula 15 and a guide head 20, the upper end of the valve body 16 is threadedly connected with the lower end of the small sleeve 13, the inner wall of the valve body 16 is provided with an upper sealing ring and a lower sealing ring, the valve body 16 is provided with a lower discharge hole 18.1 between the upper sealing ring and the lower sealing ring, the lower end of the valve body 16 is closed, the elastic sealing sleeve 17 is slidably inserted into the valve body 16, the outer wall of the elastic sealing sleeve 17 is sealed with the upper sealing ring and the lower sealing ring, the elastic sealing sleeve 17 is provided with an inner discharge hole 17.1, the elastic sealing sleeve 17 is provided with a downward clamping split block and an upward clamping split block, the inner wall of the valve body 16 is provided with a lower stop groove corresponding to the downward clamping split block, and the inner wall of the valve body 16 is provided with an upper stop groove corresponding to the upward clamping split block; the upper end of the cannula 15 is connected with the lower end of the bridge pipe 16, the lower end of the cannula 15 is provided with the guide head 20, the outer diameter of the cannula 15 is smaller than the inner diameter of the elastic sealing sleeve 17, the side wall of the cannula 15 is provided with a flow hole 15.1, and the guide head 20 can be in contact with the inwardly retracted downward clamping split block and the upward clamping split block; when the downward clamping split block is clamped with the lower stop groove, the inner discharge hole 17.1 is located between the upper sealing ring and the lower sealing ring, when the upward clamping split block is clamped with the upper stop groove, the inner discharge hole 17.1 is located above the upper sealing ring, and the up-closing backflow valve is closed.

[0065] Specifically, the inner wall of the upper sealing ring and the lower sealing ring is provided with a sealing sleeve 18.

[0066] Specifically, the upper end of the cannula 15 is connected with the bridge pipe 6 through a connecting sleeve 14, the inner wall of the upper end of the connecting sleeve 14 is threadedly connected with the outer wall of the lower end of the bridge pipe 6, the lower end of the outer convex ring in the bridge pipe 6 is below the inner injection hole 25.1, and the upper end surface of the connecting sleeve 14 and the lower end surface of the outer convex ring jointly limit the position of the piston 11.

[0067] Embodiment 2:

[0068] On the basis of embodiment 1, in the present embodiment, the up-closing backflow valve is connected with a filtering pressure control mechanism at the lower end.

[0069] The filtering pressure control mechanism comprises a slotted screen pipe 19, a lower joint 24 and a one-way valve, the outer wall of the valve body 16 is provided with an outer connecting ring above the lower discharge hole 18.1, the inner wall of the upper end of the slotted screen pipe 19 is threadedly connected with the outer wall of the outer connecting ring, the lower end of the slotted screen pipe 19 is connected with the lower joint 24, the lower joint 24 is provided with a bottom discharge hole, and the one-way valve is arranged at the upper end of the bottom discharge hole; the produced liquid is filtered through the slotted screen pipe 19, enters the filtering pressure control mechanism, and then enters the up-closing backflow valve, when the downhole pressure is too large, the one-way valve is opened, the flow capacity is increased, and the downhole pressure is reduced.

[0070] Specifically, the one-way valve comprises a sheath 21, a spring 22 and a sealing rod 23, the lower end of the sheath 21 is connected with the upper end of the inner wall of the lower joint, the spring 22 and the sealing rod 23 are arranged in the sheath 21, the spring 22 pushes the sealing rod 23 against the bottom discharge hole, and the sheath 21 is provided with a liquid passing hole.

[0071] Embodiment 3

[0072] Based on the embodiment 2, the embodiment provides a use method of the side tracking small casing reverse circulation well cementation pipe column:

[0073] S1, assembly process:

[0074] The length of the small casing 13 is matched with the length of the well cementation section, the small casing 13 is connected with the valve body 16, the elastic sealing sleeve 17, the sealing sleeve 18, the slotted screen pipe 19, the sheath 21, the spring 22, the sealing rod 23 and the lower joint 24, and the small casing 13 is hung by the elevator at the well mouth;

[0075] The first oil pipe is connected with the insertion pipe 15 and the lead-in head 20 at the lower end and is lowered into the inner cavity of the small casing 13, the length of the oil pipe is slightly shorter than the length of the small casing, the lead-in head 20 and the insertion pipe 15 are inserted into the inner cavity of the elastic sealing sleeve 17, the lead-in head 20 pushes the elastic sealing sleeve 17 to move downward, the inner discharge hole 17.1 on the elastic sealing sleeve 17 is aligned with the lower discharge hole 16.1 on the valve body 16, the circulation channel is opened, and the first oil pipe is hung by the oil pipe elevator and sat on the small casing 13;

[0076] The second oil pipe is connected with the upper joint 1, the upper central pipe 2, the rubber cylinder shaft 3, the rubber cylinder 4, the spacer ring 5, the bridge pipe 6, the cylinder 7, the seat seal shear pin 8, the rubber ring 9, the lower central pipe 10, the piston 11, the split connecting pipe 12 and the connecting sleeve 14 at the lower end and is hung up;

[0077] The first oil pipe hung at the well mouth is connected with the connecting sleeve 14, the connection is completed, the oil pipe elevator is removed and is lowered, the split connecting pipe 12 is connected with the small casing 13, the connection is completed, and the small casing 13 elevator is removed;

[0078] S2, lowering process:

[0079] The oil pipe is connected with the whole pipe column and is lowered to the designed position, the lower joint 24 is supported to the artificial well bottom, the oil pipe is gradually pressurized and stabilized, when the pressure reaches 12-15 MPa, the piston 11 moves downward, the split connecting pipe 12 loses the inner support at the lower end, the oil pipe is lifted, the split connecting pipe 12 can be separated from the small casing 13, the oil pipe is lowered again, the suspended weight is reduced by 80-120 kN, the upper joint 1, the upper central pipe 2, the rubber cylinder shaft 3, the bridge pipe 6, the lower central pipe 10, the piston 11, the connecting sleeve 14, the insertion pipe 15 and the lead-in head 20 move downward, the seat seal shear pin 8 is cut off, the rubber cylinder 3 is compressed to seal the sleeve pipe, the outer injection hole 7.1 on the side wall of the cylinder 7 is aligned with the inner injection hole 25.1 on the side wall of the bridge pipe 6, the extrusion injection channel is opened;

[0080] S3, test formation absorption:

[0081] From the second tubing upper end inject clean water, clean water through the second tubing inner diameter, the upper central tube 2 inner diameter, the inner injection hole 25.1, the outer injection hole 7.1 into the small casing 13 outer ring cavity, the liquid is blocked by the rubber tube 3 upwards, the liquid flows downward under the pressure and gravity;

[0082] The liquid outside the small casing 13 is pushed downward, through the slotted screen pipe 19 side wall upper slit into the slotted screen pipe 19 inner cavity, the liquid upwardly passes through the slotted screen pipe 19 and the valve body 16 ring cavity and the lower discharge hole 16.1, the inner discharge hole 17.1, the flow hole 15.1 into the cannula 15 inner cavity, continues to go upward, through the first tubing inner cavity, the lower discharge passage, the bridge type through hole 25.2, the upper discharge passage, into the ring cavity between the upper central tube 2 and the rubber tube shaft 3, and then from the top discharge hole 1.1 into the second tubing and the casing annulus back to the ground, test formation absorption;

[0083] S4, cement injection:

[0084] After the test is completed, cement injection is carried out, and the injection pressure and casing backflow volume are recorded. When the cement reaches the position of the slotted screen pipe 19, the resistance of the cement at the slotted screen pipe 19 increases, the ground injection pressure rises, and it is proved that the cement injection is in place;

[0085] S5, pipe column is put forward:

[0086] The second tubing is lifted, the upper joint 1, the upper central tube 2, the rubber tube shaft 3, the rubber tube 4, the spacer ring 5, the bridge pipe 6, the cylinder 7, the seat seal shear pin 8, the rubber ring 9, the lower central tube 10, the piston 11, the split connecting pipe 12, the connecting sleeve 14, the cannula 15, and the lead-in head 20 are put forward. In the upward process, the lead-in head 20 drives the elastic sealing sleeve 17 to go upward and close the passage on the side wall of the valve body 16;

[0087] S6, completion:

[0088] After waiting for the cement to solidify, the tubing is lowered to the position of the small casing 13 to form a new artificial well bottom, and the small casing 13 forms a new production casing.

[0089] In the present application, the parts themselves that are not discussed, the connection methods of the parts in the present application all belong to the known technology in the technical field. Direct application can be used, and no further description is given.

[0090] In the present application, the term "a plurality of" refers to two or more, unless otherwise expressly specified. The terms "mounting", "connected", "connecting", "fixed", and the like should be understood broadly, for example, "connected" can be fixed connection, can also be detachable connection, or integrally connected; "connected" can be directly connected, can also be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0091] In the description of the present application, it should be understood that the terms "upper", "lower", "left", "right", "front", "back" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or units referred to must have a particular direction, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation of the present application.

[0092] In the description of the present application, the terms "one embodiment", "some embodiments", "a specific embodiment" and the like mean that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0093] The above is only the preferred embodiment of the present application, and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A side-drilling small-casing reverse circulation cementing string, comprising a small casing, characterized in that, It also includes a bridge-type injection backflow mechanism that lifts up to close the backflow valve; The upper end of the small sleeve is connected to the lower end of the bridge-type injection and backflow mechanism through a release mechanism, and the lower end of the small sleeve is provided with an upward-closing backflow valve; The bridge-type injection reverse discharge mechanism includes a setting and sealing mechanism, which includes an upper connector, a rubber tube shaft, a rubber tube, and a cylinder. The outer wall of the upper end of the rubber tube shaft is threadedly connected to the inner wall of the upper connector. The outer wall of the lower end of the rubber tube shaft is connected to the upper end of the small sleeve through a setting and sealing shear pin. The rubber tube is sleeved on the outer wall of the rubber tube shaft. The bridge-type injection and reverse discharge mechanism also includes an upper central tube, a lower central tube, and a bridge tube; The upper connector has an inner convex ring on its inner wall, and the upper end of the upper central tube is connected to the inner wall of the inner convex ring. The upper connector has a top discharge hole, which connects the space between the upper central tube and the rubber cylinder shaft to the outside of the tube column. The inner wall of the bridge-type tube is provided with a bridge-type flow ring. The bridge-type flow ring is provided with a radially penetrating inner injection hole and an axially penetrating bridge-type through hole. The lower outer wall of the upper central tube is sealed to the upper end of the inner wall of the bridge-type flow ring. The upper outer wall of the lower central tube is sealed to the lower end of the inner wall of the bridge-type flow ring. The bottom of the lower central tube is closed. The bridge tube has an upper discharge channel between the upper part of the bridge flow ring and the upper central tube, and a lower discharge channel between the lower part of the bridge tube and the lower central tube. The outer wall of the bridge tube is provided with an outer convex ring, and the outer wall of the outer convex ring contacts and seals the inner wall of the rubber sleeve shaft. A sealing element is provided between the cylinder and the bridge tube below the inner injection hole. An outer injection hole is provided between the cylinder shaft and the sealing element. The inner and outer injection holes connect the space inside the central tube with the outside of the tube column.

2. The reverse circulation cementing string for side-drilling small casing according to claim 1, characterized in that, The release mechanism includes a piston and a split connecting tube; The sealing element is the piston. The inner wall of the piston contacts and seals the outer wall of the bridge tube, and the outer wall of the piston contacts and seals the cylinder. An anti-detachment ring is provided at the lower end of the piston. The segmented connecting tube is sleeved on the outer wall of the anti-detachment ring. The upper outer wall of the segmented connecting tube is connected to the lower inner wall of the cylinder. The lower end of the segmented connecting tube has a segmented structure. A locking block is provided on the outer wall of the segmented section of the segmented connecting tube. The locking block is fitted into the lower inner wall of the small sleeve. The outer wall of the anti-detachment ring is provided with a pressure ring, the outer diameter of which is the same as the normal inner diameter of the segment, which is used to prevent the segment from shrinking inward. The outer wall of the anti-detachment ring is provided with an unlocking groove above the pressure ring, which is used to restore the segment's ability to shrink inward.

3. The reverse circulation cementing string for side-drilling small casing according to claim 1, characterized in that, The upward-closing backflow valve includes a valve body, an elastic sealing sleeve, a tube, and an inlet head; The upper end of the valve body is connected to the lower end of the small sleeve. The inner wall of the valve body is provided with an upper sealing ring and a lower sealing ring. The valve body is provided with a lower discharge hole between the upper sealing ring and the lower sealing ring. The lower end of the valve body is closed. The elastic sealing sleeve is slidably inserted into the valve body, and the outer wall of the elastic sealing sleeve is sealed with the upper sealing ring and the lower sealing ring. The elastic sealing sleeve is provided with an inner discharge hole. The elastic sealing sleeve is provided with a downward engaging split block and an upward engaging split block. The inner wall of the valve body is provided with a lower stop groove corresponding to the downward engaging split block and an upper stop groove corresponding to the upward engaging split block. The upper end of the insertion tube is connected to the lower end of the bridge tube. An inlet head is provided at the lower end of the insertion tube. The outer diameter of the insertion tube is smaller than the inner diameter of the elastic sealing sleeve. A flow hole is provided on the side wall of the insertion tube. The inlet head can contact the retracted downward engaging split block and the upward engaging split block. When the downward engaging split block engages with the lower stop groove, the inner discharge hole is located between the upper sealing ring and the lower sealing ring. When the upward engaging split block engages with the upper stop groove, the inner discharge hole is located above the upper sealing ring. The upward closing return valve is closed.

4. The reverse circulation cementing string for side-drilling small casing according to claim 3, characterized in that, The lower end of the upward-closing backflow valve is connected to a filter pressure control mechanism; The filtration pressure control mechanism includes a slotted screen tube, a lower connector, and a one-way valve; An outer connecting ring is provided on the outer wall of the valve body above the lower discharge hole. The inner wall of the upper end of the slotted screen tube is connected to the outer wall of the outer connecting ring. The lower end of the slotted screen tube is connected to a lower connector. The lower connector is provided with a bottom discharge hole. The one-way valve is provided above the bottom discharge hole.

5. The reverse circulation cementing string for side-drilling small casing according to claim 1, characterized in that, The outer wall of the upper central tube is provided with a diameter-changing step, forming a large-diameter section and a small-diameter section. The outer diameter of the lower central tube is the same as that of the small-diameter section of the upper central tube. The inner diameter of the bridge-type flow ring is smaller than that of the bridge-type tube. The upper end of the bridge-type tube is connected to the large-diameter section of the upper central tube. The bridge-type tube is provided with an upper discharge hole between the outer convex ring and the large-diameter section of the upper central tube. The space between the upper discharge hole, the small-diameter section of the upper central tube and the bridge-type tube is the upper discharge channel. The space between the lower central tube and the bridge-type tube is the lower discharge channel.

6. The reverse circulation cementing string for side-drilling small casing according to claim 5, characterized in that, The bridge-type pipe has expansion grooves above and below the bridge-type flow ring. The sum of the areas of all bridge-type through holes is greater than or equal to the area of ​​the annulus between the lower central pipe and the bridge-type pipe. The sum of the areas of all upper discharge holes is greater than the area of ​​the annulus between the small diameter part of the upper central pipe and the bridge-type pipe.

7. The reverse circulation cementing string for side-drilling small casing according to claim 1, characterized in that, At least two rubber tubes are provided, with a spacer ring between every two rubber tubes.

8. A reverse circulation cementing string for side-drilling small casing according to claim 4, characterized in that, The one-way valve includes a sleeve, a spring, and a sealing rod; The lower end of the sheath is connected to the upper end of the inner wall of the lower connector. The spring and the sealing rod are disposed inside the sheath. The spring pushes the sealing rod against the bottom discharge hole. The sheath is provided with a liquid passage hole.

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