A method for treating casing damage in an ultra-deep well

Abstract

The application discloses a kind of ultra-deep well casing damage treatment methods, belong to well repair operation technical field.Collecting repair, temporary plugging, back connection three technologies in one, using large size high rigidity drilling tool combination optimizes existing mill casing process, improves the safety and operation success rate during mill casing;Using the combination temporary plugging process of plugging layer+machine bridge, increases the pressure-bearing capacity of wellbore temporary plugging, guarantees the smooth construction of later cementing, simultaneously with plugging layer as barrier, effectively avoids cement slurry into machine bridge, eliminates the risk that cement in machine bridge cannot be recycled;Using the technology of removing deformed casing+back connection casing to wellhead, realizes the process of rebuilding wellbore.Therefore, the treatment method proposed by the application can realize effective and safe treatment, and can solve the problem that ultra-deep oil and gas well cannot produce after casing damage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of well repair operation, and relates to a method for treating casing damage in an ultra-deep well. BACKGROUND

[0002] Casing damage in an oil well will cause the following harm to oilfield development: the production string cannot be normally lowered into the well; when the casing damage position is in a water layer or a sand layer, the oil well will produce a large amount of water or sand; the oil well cannot be stimulated; casing damage can easily cause blowout; and the oil well can be scrapped. Casing repair and restoration: for a broken casing, there are the following methods for repairing a hole or a crack:

[0003] The first method: squeezing cement slurry

[0004] When the oil layer pressure is not high and the breakage and leakage are not serious, the casing can be repaired by squeezing cement slurry. The process method is as follows: first, a through hole gauge is used to pass through the casing with a diameter of 8-10 mm smaller than the inner diameter of the casing, then a suspended bridge plug (tool name: bridge plug) is lowered at a proper position of the breakage, the wellbore below the breakage is temporarily sealed, a certain amount of cement slurry is injected above the bridge plug, and the cement slurry is solidified into a cement plug. After the cement plug is solidified, the cement plug in the casing is drilled, and the breakage quality of the cement sealing is checked by pressure test. After confirming that the sealing quality is qualified, the suspended bridge plug is drilled, and sand is flushed to the bottom of the well. The casing repaired by this method can generally withstand a pressure of 40-80 MPa. In the future, the well should be protected by a packer during high-pressure operation to avoid the section from bearing high pressure.

[0005] The second method: replacing the casing

[0006] When the breakage position is in the upper part of the oil well, and the casing above the breakage can be taken out by reverse threading, the casing above the accident section can be taken out by reverse threading, and a new casing can be lowered into the well and tightly screwed. The advantage of this method is that the consistency of the casing inner diameter is ensured, and the downhole tool can pass through smoothly during future operation. The disadvantage is that the screwing tightness of the casing at the downhole is not as tight as that at the wellhead.

[0007] The third method: patching method

[0008] That is, a thin-walled pipe is attached to the inner wall of the damaged casing to achieve the purpose of repair. The process principle is as follows: a specially designed high-pressure-resistant rubber cylinder is sleeved with a corrugated pipe (thin-walled pipe) and lowered to the casing damage position in the well. The rubber cylinder is inflated to expand the corrugated pipe, so that the corrugated pipe tightly adheres to the inner wall of the casing damage position, and the casing and the corrugated pipe are bonded into one body by an adhesive. After the adhesive is solidified, the high-pressure-resistant rubber cylinder is removed by the running tool. This patching process is simple and safe to operate.

[0009] However, the casing of some production wells in Tarim Oilfield is deformed by high-pressure salt water, causing salt water to channel into the wellbore, to flow back to the reservoir, and even to break the casing and lose the oil and gas production channel, which seriously affects oil and gas production. The current treatment technology uses an expansion device to be lowered to the deformed casing depth, and the deformed casing is expanded by the radial force generated by the internal pressure and the hydraulic mechanism. This technology is affected by the strength of the expansion device and the supporting force, and by the higher pressure and temperature in ultra-deep wells, so the expansion device cannot expand the thick-walled high-steel-grade casing in ultra-deep wells. The small milling cone channeling process has the risk of deviating from the wellbore during the drilling and milling process, and has poor adaptability in the casing damage treatment operation in Tarim ultra-deep wells. SUMMARY

[0010] The purpose of the present application is to solve the problem that the expansion device cannot expand the thick-walled high-steel-grade casing in ultra-deep wells in the prior art, and to provide an ultra-deep well casing damage treatment method.

[0011] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0012] The ultra-deep well casing damage treatment method provided by the present application comprises the following steps:

[0013] The milling shoes and the centralizers are selected according to the deformation state of the downhole casing, and the outer diameters of the milling shoes and the centralizers are greater than the outer diameter of the drill collar;

[0014] The through-well gauge is lowered into the tail pipe, the hydraulic retrievable bridge is blocked in the tail pipe, the blocking layer is filled on the hydraulic retrievable bridge, and the production layer of the wellbore is blocked;

[0015] The casing is set and cemented after the ground breaking test is performed on the casing by applying pressure at the wellhead, and the back-connection casing is not configured with a casing centralizer at a position below the damaged point;

[0016] After the milling shoes drill through the blocking layer and flush to the depth of the hydraulic retrievable bridge, the casing above the depth of the hydraulic retrievable bridge is scraped and the well is passed, the hydraulic retrievable bridge is fished out, and the oil and gas production channel is restored.

[0017] Preferably, the outer diameter of the back-connection casing is less than or equal to the outer diameter of the milling shoes, and the outer diameter of the milling shoes is less than or equal to the standard inner diameter of the deformed casing.

[0018] Preferably, the outer diameter of the centralizer is equal to the outer diameter of the milling shoes minus 2 mm.

[0019] Preferably, the hydraulic retrievable bridge is set and sealed at a position 80-100 m below the tail pipe hanger.

[0020] Preferably, the filled blocking layer comprises two parts of sand filling and cement injection, and the sand is filled first and then the cement is injected on the hydraulic retrievable bridge.

[0021] Preferably, the ceramic sand and coarse sand are mixed in a ratio of 1:2 and filled in the hydraulic retrievable bridge.

[0022] Preferably, 50-60 m of ash is injected above the sand surface to form a cement plug.

[0023] Preferably, the grinding shoe is a convex bottom grinding shoe or a concave bottom grinding shoe.

[0024] Preferably, the deformation amount of the grinding depth position casing does not exceed the casing central axis, and the convex bottom grinding shoe is used; and the deformation amount of the grinding depth position casing exceeds the casing central axis, and the concave bottom grinding shoe is used.

[0025] Preferably, during the grinding process, the pipe string is always subjected to the thrust provided by the deformed casing, and the drilling tool is downward drilled on the side of the undeformed casing.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The super-deep well casing damage treatment method provided by the present application integrates the three technologies of casing repair, temporary plugging and back connection, optimizes the existing grinding casing process by using a large-size high-rigidity drilling tool combination, improves the safety and operation success rate during drilling and grinding casing, increases the pressure-bearing capacity of wellbore temporary plugging by using the combination of plugging layer and bridge, ensures the smooth construction of later cementing, and effectively avoids the entry of cement slurry into the bridge by using the plugging layer as a barrier, thereby eliminating the risk of cement entering the bridge and being unable to be recovered. The technology of removing the deformed casing and back connecting the suspended casing to the wellhead is realized, and the safe wellbore reconstruction process is realized. Therefore, the treatment method provided by the present application can realize effective and safe treatment, and can solve the problems of the expansion pipe expander being unable to expand the thick-walled high-steel-grade casing in the super-deep well and the oil and gas well being unable to produce after casing damage in the super-deep oil and gas field.

[0028] Further, according to the principle of grinding shoe selection, during the drilling and grinding process, the pipe string is always subjected to the thrust provided by the deformed casing, and the drilling tool is downward drilled on the side of the undeformed casing, thereby reducing the risk of the drilling and grinding being deviated from the wellbore on the casing damage side.

[0029] Further, the large size and high rigidity of the grinding shoe and the centralizer are more conducive to the centralization of the drilling tool, avoiding deviation from the wellbore, and the drilling and grinding process is overall cutting of the deformed casing, avoiding the deviation of the existing process milling cone from the wellbore under the action of the inclined surface support force of the deformed casing.

[0030] Further, considering the space left for the cement and sand bridge, the hydraulic retrievable bridge is set and sealed at a position 80-100 m below the liner hanger.

[0031] Further, after setting and sealing, ceramic sand and coarse sand are mixed in a ratio of 1:2 and filled in the bridge about 20 m above, to prevent the cement slurry from penetrating the sand bridge into the bridge.

[0032] Further, a 50-60m cement plug is made above the sand face to increase the sealing quality and avoid leakage and reservoir pollution in the later casing cementing process. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0034] Figure 1 The flow chart of the method for treating casing damage in ultra-deep well of the present application.

[0035] Figure 2 The structure diagram of the grinding shoe of the present application ((a) is a convex bottom grinding shoe, and (b) is a concave bottom grinding shoe).

[0036] Figure 3 The structure diagram of the temporary plugging of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application, and obviously, the described embodiments are some of the embodiments of the present application, but not all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art on the basis of the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0039] It should be noted that: similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0040] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicate the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0041] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0042] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or indirectly connected through an intermediate medium; can be connected inside two elements. 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.

[0043] The present application will be described in further detail below in conjunction with the accompanying drawings:

[0044] The present application proposes a method for treating casing damage in an ultra-deep well, as shown in the figure, comprising the following steps: Figure 1

[0045] Step 1, select the shoe and centralizer to mill the deformed casing according to the deformation state of the downhole casing, the outer diameter of the shoe and the centralizer is greater than the outer diameter of the drill collar;

[0046] The shoe is a blade wing convex bottom shoe or a concave bottom shoe.

[0047] If the deformation amount of the casing at the milling depth position does not exceed the casing central axis, a blade wing convex bottom shoe is used; if the deformation amount of the casing at the milling depth position exceeds the casing central axis, a concave bottom shoe is used.

[0048] The outer diameter of the back-connection casing is ≤ the outer diameter of the shoe ≤ the standard inner diameter of the deformed casing.

[0049] The outer diameter of the centralizer = the outer diameter of the shoe - 2mm.

[0050] During the milling process, the pipe string is always subjected to the thrust provided by the deformed casing, and the drilling tool is attached to the side of the undeformed casing and drilled downward. ​

[0051] Step 2, run the well gauge into the tail pipe, block the hydraulic retrievable bridge in the tail pipe, fill the blocking layer on the hydraulic retrievable bridge, and realize the blocking of the wellbore production layer;

[0052] The hydraulic retrievable bridge is set and sealed at a position 80-100 m below the tail pipe hanger.

[0053] The filled blocking layer includes sand filling and cement injection, and the sand is filled first and then the cement is injected on the hydraulic retrievable bridge.

[0054] The ceramic sand and coarse sand are mixed in a ratio of 1:2 and then filled on the hydraulic retrievable bridge.

[0055] Cement plug is formed by injecting 50-60 m of cement above the sand surface.

[0056] Step 3, perform the ground breaking test on the casing at the wellhead, and after the ground breaking test pressure is passed, cement the casing, and do not configure the casing centralizer for the tie-back casing lowered to the position below the damage point.

[0057] Step 4, after drilling through the blocking layer with the grinding shoe, flush to the depth of the hydraulic retrievable bridge, scrape the wall of the casing above the hydraulic retrievable bridge depth, run the well, and then fish out the hydraulic retrievable bridge to restore the oil and gas well production channel.

[0058] The specific contents of the treatment method include the following:

[0059] 1) Lower the lead mold to determine the deformation of the casing

[0060] Lower the lead mold to the casing deformation depth, apply pressure of 3-8 tons, and then drill up, check the lead mold shape, and determine the degree and shape of casing deformation to provide a basis for selecting the grinding shoe later.

[0061] 2) Select the appropriate grinding shoe according to the deformation state of the downhole casing

[0062] According to the downhole state reflected by the downhole television and the lead mold, if the deformation amount of the casing at the milling depth position does not exceed the central axis of the casing, a convex bottom grinding shoe with wings is used. If the deformation amount of the casing at the milling depth position exceeds the central axis of the casing, a concave bottom grinding shoe is used. According to the above principles for selecting the grinding shoe, during the drilling and milling process, the pipe string is always subjected to the thrust provided by the deformed casing, and the drilling tool is attached to the side of the undeformed casing and drilled downward, reducing the risk of deviating from the wellbore on the side of the casing damage, as shown in FIGS. Figure 2 (a) is a convex bottom grinding shoe with wings, and (b) is a concave bottom grinding shoe.

[0063] 3) Optimize the drilling assembly according to the safety range requirements: grinding shoe + centralizer + drill collar + fishing cup + drill pipe

[0064] The main idea of the drill tool combination of the application is to use the largest size of the grinding shoe and the centralizer within the safety range, and the large size and high rigidity of the grinding shoe and the centralizer are more conducive to the centralization of the drill tool, avoiding the deviation of the wellbore, and the whole cutting of the deformed casing is carried out during the drilling and grinding process, which avoids the deviation of the existing process milling cone under the action of the support force of the inclined surface of the deformed casing. The drill is prevented from being stuck during the drilling and grinding process. According to the standard requirements, the outer diameter of the grinding shoe meets the requirement of not less than the inner diameter of the casing-6mm, and after the deformed casing is removed by grinding and milling, a casing with a size smaller by one needs to be connected back. Considering that the connected back casing needs to be at least 6mm smaller than the wellbore.

[0065] Among them, the outer diameter of the connected back casing +6mm≤the outer diameter of the grinding shoe≤the standard inner diameter of the deformed casing-6mm.

[0066] The outer diameter of the centralizer=the outer diameter of the grinding shoe-2mm, and the length of the centralizer is 9m per root.

[0067] 5) Temporary plugging of the producing layer

[0068] Considering the space left for the cement and sand bridge, the hydraulic retrievable machine bridge is set in the position 80-100m below the tail pipe hanger. After setting, the ceramic sand and coarse sand are mixed in a ratio of 1:2 and filled in the machine bridge about 20m, to prevent the cement slurry from penetrating into the machine bridge through the sand bridge. A 50-60m cement plug is drilled above the sand surface to increase the plugging quality and avoid leakage during the later casing cementing process, which pollutes the reservoir, as shown in Figure 3

[0069] The cement ash+sand bridge+retrievable machine bridge combination temporary plugging process increases the pressure bearing capacity of the wellbore temporary plugging, ensures the smooth construction of the later cementing, and effectively avoids the cement slurry entering the machine bridge by using the sand bridge as a barrier, eliminating the risk of the cement entering the machine bridge and being unable to be retrieved.

[0070] 6) Connection and cementing

[0071] According to the pressure value that the damaged casing will bear during the cementing construction period, the pressure is applied at the wellhead to do the breakdown test. If leakage occurs, plugging operation is carried out until the breakdown test pressure passes, and then the casing is cemented. The connection casing below the damaged point is not configured with a centralizer.

[0072] 7) Restoration of the wellbore passage

[0073] The drill is plugged to the middle position of the sand filling in the first step, and the rotary table is washed to the depth of the retrievable machine bridge. After the wall scraping and well passage of the casing above the machine bridge depth, the special fishing tool is used to take out the retrievable machine bridge, and the oil and gas well production passage is rebuilt and restored.

[0074] Therefore, the super deep well casing damage treatment method provided by the application has the following advantages:

[0075] ​1) Adopt large size grinding shoes and centralizer, to ensure the centering problem of drilling and grinding process, after removing the deformed casing, back to a small size of high steel production casing, to implement back to cementing operation, to re-establish the oil and gas production channel.

[0076] 2) Adopt large size high stiffness drilling tool combination to optimize the existing milling casing process, to improve the safety and operation success rate during drilling and milling casing.

[0077] 3) Adopt cement + sand bridge + machine bridge combination temporary plugging process, to increase the pressure bearing capacity of wellbore temporary plugging.

[0078] 4) With sand bridge in the middle, to avoid the risk of cement slurry entering the machine bridge, and the machine bridge cannot be unblocked.

[0079] 5) Adopting the process of removing deformed casing + back to suspended casing to wellhead, to realize the process of rebuilding safe wellbore.

[0080] Therefore, the ultra-deep well casing damage treatment method can realize effective and safe ultra-deep well casing damage treatment, and can solve the problem that the oil and gas well cannot produce after the casing damage of ultra-deep oil and gas field.

[0081] The above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for treating casing damage in ultra-deep wells, characterized in that, Includes the following steps: The grinding shoe and stabilizer are selected to mill the deformed casing according to the deformation state of the downhole casing. The outer diameter of both the grinding shoe and the stabilizer is larger than the outer diameter of the drill collar. The well gauge is lowered into the tailpipe, the hydraulically retrievable bridge is sealed in the tailpipe, and the sealing layer is filled on the hydraulically retrievable bridge to seal the wellbore producing formation. Apply pressure at the wellhead to perform a ground failure test on the casing. After the ground failure pressure test is passed, run the casing down for cementing. Do not equip the casing reconnection below the failure point with a casing centralizer. After the grinding shoe drill penetrates the sealing layer, it is flushed to the depth of the hydraulically retrievable bridge. After scraping the casing wall and cleaning the well above the depth of the hydraulically retrievable bridge, the hydraulically retrievable bridge is retrieved to restore the production channel of the oil and gas well. The grinding shoe is either a blade-wing convex-bottom grinding shoe or a concave-bottom grinding shoe; if the deformation of the sleeve at the milling depth does not exceed the central axis of the sleeve, a blade-wing convex-bottom grinding shoe is used; if the deformation of the sleeve at the milling depth exceeds the central axis of the sleeve, a concave-bottom grinding shoe is used. During the milling process, the tubing is constantly subjected to the thrust provided by the deformed casing, and the drill bit drills downwards while adhering to the side of the undeformed casing.

2. The method for treating casing damage in ultra-deep wells according to claim 1, characterized in that, The outer diameter of the reconnection sleeve ≤ the outer diameter of the grinding shoe ≤ the standard inner diameter of the deformed sleeve.

3. The method for treating casing damage in ultra-deep wells according to claim 1, characterized in that, The outer diameter of the stabilizer = the outer diameter of the grinding shoe - 2mm.

4. The method for treating casing damage in ultra-deep wells according to claim 1, characterized in that, The hydraulically removable axle is seated 80m-100m below the tailpipe hanger.

5. The method for treating casing damage in ultra-deep wells according to claim 1, characterized in that, The filling and sealing layer consists of two parts: sand filling and mortar injection. On the hydraulically removable bridge, sand is filled first and then mortar is injected.

6. The method for treating casing damage in ultra-deep wells according to claim 5, characterized in that, The mixture of ceramsite and coarse sand in a 1:2 ratio is filled onto the hydraulically removable bridge.

7. The method for treating casing damage in ultra-deep wells according to claim 5, characterized in that, A cement plug is formed by injecting 50-60mm of ash into the sand surface.

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