A method for sealing external leakage pipes in oil and water wells

Abstract

The present invention discloses a method for plugging an external annulus of an oil and water well, wherein the method comprises: milling the outer annulus of the casing of the oil and water well to be plugged; inserting a double row of conduits into the outer annulus of the casing, including a shallow conduit and a deep conduit; plugging the top of the outer annulus of the casing of the oil and water well to be plugged; injecting a plugging agent into the outer annulus of the casing through the shallow conduit, and after the injection is completed, waiting for solidification under pressure; injecting a plugging agent into the outer annulus of the casing through the deep conduit, and after the injection is completed, waiting for solidification under pressure, thereby completing the external plugging of the oil and water well. The method solves the problem that external plugging of oil and water wells in the past was plugged by injecting cement from the inside of the casing to the outside of the casing, which was difficult to diffuse in the formation due to insufficient flow rate and pressure when injecting cement, resulting in a small cement plugging coverage area, loose plugging, incomplete plugging, and the possibility of external plugging of the oil and water well again after plugging for a period of time.

Description

Technical Field

[0001] The invention relates to the field of oilfield operations, in particular to a method for externally plugging an external pipe breakout in an oil or water well. Background Art

[0002] With the development of oil fields, underground well conditions are becoming increasingly complex, and more and more wells are bubbling outside the pipe. Once bubbling occurs in oil and water wells, it will cause resource waste and environmental pollution. For some wells located in shallow gas areas, circulation channels are formed after bubbling, that is, the pressure of the production layer escapes through the channel outside the pipe, which is prone to blowouts and poses serious safety hazards. There are great risks in the construction of well bubbling outside the pipe, especially for the plugging of deep wells bubbling outside the pipe. The construction is difficult and the plugging is difficult. In addition, since some wells cannot accurately determine the source of the bubbling pressure, the bubbling wells cannot be treated in time.

[0003] Existing plugging methods involve drilling holes in the casing of oil and water wells and then injecting plugging cement from inside the casing to the outside of the wells. However, this method has drawbacks: because cement is injected from inside the wells, factors such as flow rate and hole size can lead to insufficient injection pressure, making it difficult for the cement to diffuse into the formation outside the wells. This results in a small cement coverage area, resulting in a poor plugging. Furthermore, this method can cause recurrence of well bubbling after one to two years of plugging. Bubbling wells not only disrupt oilfield development and production safety, but also cause environmental pollution, ecological damage, and economic losses. Summary of the Invention

[0004] In view of this, the present invention provides a method for sealing oil and water well bulging outside the pipe to solve the problem that oil and water well bulging is usually sealed by injecting cement from the inside of the casing to the outside of the pipe. Due to insufficient flow rate and pressure when injecting cement, it is difficult for cement to diffuse in the formation, resulting in a small cement sealing coverage area, loose sealing, incomplete sealing, and the possibility of oil and water well bulging again after a period of sealing.

[0005] The present invention provides a method for externally plugging an external pipe in an oil and water well, comprising the steps of:

[0006] Milling the outer annulus of the oil and water well casing to be sealed;

[0007] Running a double row of conduits into the outer annulus of the casing, including a shallow-level conduit and a deep-level conduit;

[0008] To seal the top of the outer annulus of the oil and water well casing to be blocked;

[0009] injecting the plugging agent into the outer annulus of the casing through a shallow-level guide tube, and then solidifying the plugging agent under pressure after the injection is completed;

[0010] The plugging agent is squeezed into the outer annulus of the casing through a deep-level pipe. After the squeezing is completed, the plugging agent is solidified under pressure to complete the outer plugging of the oil and water well.

[0011] Preferably, the method for plugging the top of the outer annulus of the oil and water well casing comprises:

[0012] Determine whether the oil and water well is a surface cased well or an unsurface cased well;

[0013] If it is a well with surface casing, then at the top of the outer annulus of the casing, the casing and the surface casing are welded with an iron ring to seal the top of the outer annulus of the oil and water well casing through the iron ring;

[0014] If it is a well without surface casing, a first packer is installed at the top of the outer annulus of the casing to seal the top of the outer annulus of the oil and water well casing. The first packer is connected to the shallow-level conduit, and a high-pressure switch is installed at the outlet of the shallow-level conduit.

[0015] Preferably, it also includes:

[0016] If the well is uncased, a second packer is installed in the outer annulus of the casing, near the bottom of the shallow-stage casing, so that the outer annulus of the casing of the uncased well is separated into upper and lower spaces by the second packer;

[0017] The second packer is connected to the shallow-stage conductor.

[0018] Preferably, the method of milling the outer annulus of the oil and water well casing to be plugged comprises:

[0019] Obtain the pressure value of the crossflow layer of the oil and water well to be plugged;

[0020] Adjusting the density and viscosity of the workover fluid according to the crossflow layer pressure value;

[0021] Use the prepared workover fluid to mill the outer annulus of the casing.

[0022] Preferably, the method of injecting the plugging agent into the outer annulus of the casing through a shallow-level conduit comprises:

[0023] Obtain the squeeze pressure and squeeze volume of one shot;

[0024] According to the primary squeezing pressure and squeezing volume, squeezing the plugging agent into the outer annulus of the casing through the shallow-level guide tube;

[0025] The method of squeezing a plugging agent into the outer annulus of the casing through a deep-level conduit comprises:

[0026] Obtain secondary extrusion pressure and extrusion volume;

[0027] According to the secondary squeezing pressure and squeezing volume, the plugging agent is squeezed into the outer annulus of the casing through the deep-stage conduit.

[0028] Preferably, the method for obtaining the primary extrusion pressure and extrusion volume comprises:

[0029] Obtaining a primary squeezing radius, a primary squeezing thickness, and a formation porosity, and determining a primary squeezing volume based on the primary squeezing radius, the primary squeezing thickness, and the formation porosity;

[0030] The formation fracture pressure value and the crossflow layer pressure value are obtained, and the primary squeeze pressure is determined according to the formation fracture pressure and the crossflow layer pressure value.

[0031] The method for obtaining the secondary extrusion pressure and extrusion volume includes:

[0032] Obtaining a secondary squeezing radius and a secondary squeezing thickness, and determining a secondary squeezing amount according to the secondary squeezing radius, the secondary squeezing thickness, and the formation porosity;

[0033] The crossflow layer pressure value and the shielding layer pressure value are obtained, and the secondary extrusion pressure is determined according to the crossflow layer pressure value and the shielding layer pressure value.

[0034] Preferably, before milling the outer annulus of the oil and water well casing to be plugged, the method further comprises:

[0035] Carry out pressure reduction treatment on oil and water wells to be plugged;

[0036] The pressure reduction process is as follows:

[0037] Shut down the oil and water wells to be sealed and the surrounding injection wells.

[0038] Preferably, the shallow-level conduit is lowered to a depth that reaches the bottom of the topsoil layer;

[0039] The deep-stage conduit is lowered to a depth above the crossflow layer;

[0040] Preferably, the waiting time is 24 to 72 hours.

[0041] The present invention has the following beneficial effects:

[0042] The present invention provides a method for plugging bulges outside the casing of an oil and water well. By arranging double rows of guide tubes, upper and lower double-layer plugging is performed in the formation outside the casing, thereby solving the problem that bulges outside the oil and water well are plugged by injecting cement from the inside of the casing to the outside of the pipe. Due to insufficient flow rate and pressure when injecting cement, it is difficult for cement to diffuse in the formation, resulting in a small cement plugging coverage area, loose plugging, incomplete plugging, and the possibility of bulging outside the well again after plugging for a period of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0044] Figure 1 The present invention is a flowchart of a method for externally plugging an external pipe rupture in an oil and water well according to an embodiment of the present invention.

[0045] Figure 2 Schematic diagram of plugging a surface cased well in an embodiment of the present invention.

[0046] Figure 3 Schematic diagram of plugging a well without surface casing in an embodiment of the present invention.

[0047] In the figure, 1-casing, 2-surface casing, 3-shallow guide tube, 4-deep guide tube, 5-first packer, 6-second packer, 7-high-voltage switch, 8-iron ring. DETAILED DESCRIPTION

[0048] The present invention will be described below based on the embodiments, but it is worth noting that the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. However, for the part that is not described in detail, those skilled in the art can also fully understand the present invention.

[0049] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present invention, and are not actually drawn to scale.

[0050] At the same time, unless the context clearly requires otherwise, words such as "include", "comprising" and the like throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, as "including but not limited to".

[0051] Figure 1 The present invention is a flowchart of a method for externally plugging an external pipe rupture in an oil and water well according to an embodiment of the present invention.

[0052] Figure 2 Schematic diagram of plugging a surface cased well in an embodiment of the present invention. Figure 3 FIG. 1 is a schematic diagram of plugging a well without surface casing in an embodiment of the present invention. Figure 1 、 Figure 2 、 Figure 3As shown, a method for plugging external bubbling of oil and water wells outside the casing comprises the following steps: step 1: milling the outer annulus of the oil and water well casing to be plugged; step 2: inserting a double row of pipes into the outer annulus of the casing, including a shallow pipe 3 and a deep pipe 4; step 3: plugging the top of the outer annulus of the oil and water well casing to be plugged; step 4: injecting a plugging agent into the outer annulus of the casing through the shallow pipe 3, and after injection, waiting for solidification under pressure; step 5: injecting a plugging agent into the outer annulus of the casing through the deep pipe 4, and after injection, waiting for solidification under pressure, thereby completing the external plugging of the oil and water well. This method solves the problem that external bubbling of oil and water wells is plugged by injecting cement from the inside of the casing 1 to the outside of the casing. Due to insufficient flow rate and pressure during cement injection, cement diffusion in the formation is difficult, resulting in a small cement plugging coverage area, loose plugging, incomplete plugging, and the possibility of recurrence of external bubbling of the oil and water well after plugging for a period of time.

[0053] Step 1: Mill the outer annulus of the oil and water well casing to be plugged.

[0054] In the present invention, the method for milling the outer annulus of the casing of the oil and water well to be plugged includes: obtaining the pressure value of the crossflow layer of the oil and water well to be plugged; adjusting the density and viscosity of the well repair fluid according to the crossflow layer pressure value; and using the adjusted well repair fluid to mill the outer annulus of the casing.

[0055] In the embodiment of the present invention, casing milling is to remove various dirt in the annulus outside the casing 1 and to remove the cement cap in the annulus outside the casing. When casing milling, it is first necessary to determine the crossflow layer of the oil and water well and its layer pressure, wherein the crossflow layer and layer pressure can be provided by well logging or geological data or by reference to the layer pressure of adjacent wells. The density and viscosity of the workover fluid are adjusted according to the crossflow layer pressure value. The greater the density and viscosity of the workover fluid, the greater the pressure during casing milling. Therefore, when the workover fluid is casing milled underground, its pressure reaches a balance with the formation pressure, preventing the workover fluid from leaking into the formation or the underground crossflow layer fluid from flowing upward or causing well wall collapse.

[0056] During casing milling, a wellbore capping device must be installed on top of the surface casing at the wellhead to prevent blowouts. The pressure rating of the selected wellbore capping device should be determined based on the pressure of the crossflow zone. A 290mm or 246mm milling head and a 219mm or 194mm milling barrel are then used to form a casing string to mill the outer annulus of the casing. The prepared workover fluid is then used to mill the outer annulus of the casing. Specific parameters for casing milling are: pump pressure 0.3-1.0 MPa, displacement 1.5-1.8 m³ / min, bit pressure 10-50 kN, rotation speed 80-150 rpm, and the casing is milled to a depth of 150 meters, which is defined as reaching above the crossflow zone.

[0057] Step 2: inserting a double row of conduits into the outer annulus of the casing, including a shallow-level conduit 3 and a deep-level conduit 4.

[0058] In the present invention, the shallow-level conduit 3 is lowered to a depth that reaches the bottom of the topsoil layer; and the deep-level conduit 4 is lowered to a depth that reaches above the crossflow layer.

[0059] In this embodiment of the present invention, after the casing milling is completed, the shallow and deep guide pipes 3 and 4 are lowered into the outer annulus of the casing. The bottom of the shallow guide pipe 3 is lowered to 110 meters below the surface, at the bottom of the topsoil layer. The bottom of the deep guide pipe 4 is lowered to 150 meters below the surface, at the top of the crossflow layer. Slanted guide shoes are installed at the bottom of each of the shallow and deep guide pipes 3 and 4 to prevent obstructions and facilitate lowering of the pipe string. The tops of the shallow and deep guide pipes 3 and 4 are connected to the wellbore with sealing fluid.

[0060] Step 3: Seal the top of the outer annulus of the oil and water well casing to be blocked.

[0061] In the present invention and Figure 2 、 Figure 3 In the method for sealing the top of the outer annulus of the oil and water well casing, the method includes: judging whether the oil and water well is a well with surface casing or a well without surface casing; if it is a well with surface casing, welding a ring iron 8 on the casing 1 and the surface casing 2 at the top of the outer annulus of the casing, and sealing the top of the outer annulus of the oil and water well casing by the ring iron 8; if it is a well without surface casing, installing a first packer 5 at the top of the outer annulus of the casing, and sealing the top of the outer annulus of the oil and water well casing by the first packer 5, the first packer 5 is connected to the shallow-level conduit 3, and a high-voltage switch 7 is installed at the outlet of the shallow-level conduit 3.

[0062] In the embodiment of the present invention, when squeezing the plugging agent into the outer annulus of the casing through the shallow-level conduit 3, the top opening of the outer annulus of the casing needs to be sealed first to prevent the plugging agent from flowing back from the top of the outer annulus during squeezing.

[0063] For oil and water wells with surface casing 2, the surface casing 2 is outside the casing 1, and the outer annulus of the casing is the annular space between the outside of the casing 1 and the inside of the surface casing 2. When sealing the top of the outer annulus of the casing, the inner and outer ring irons 8 can be directly placed on the outside of the surface casing 2 and the annular space between the casing 1 and the surface casing 2. Finally, the ring irons 8 are welded to the outer wall of the casing 1, the inner wall of the surface casing 2 and the outer wall of the surface casing 2 respectively, thereby completing the sealing of the top of the outer annulus of the casing of the oil and water well with the surface casing 2.

[0064] For oil and water wells without surface casing 2, an annular space is formed between the casing 1 and the formation. Since there is no surface casing 2, it is impossible to seal the top of the annular space outside the casing by installing the ring iron 8. Therefore, it is necessary to install a first packer 5 at the top of the annular space outside the casing. The first packer 5 is cylindrical, with a diameter the same as the diameter of the annular space outside the casing. The first packer 5 has a casing 1 hole for passing the casing 1. During installation, the shallow-level pipe 3 and the deep-level pipe 4 can be passed through the first packer 5 and connected to the first packer 5. When the shallow-level pipe 3 and the deep-level pipe 4 are lowered, the first packer 5 is lowered into the annular space outside the casing together with the shallow-level pipe 3 and the deep-level pipe 4. When the shallow-level pipe 3 and the deep-level pipe 4 reach the designated position, the position of the first packer 5 is at the top of the annular space outside the casing.

[0065] The first packer 5 has a rubber bladder on its outer circumference, the interior of which is connected to the interior of the shallow conduit 3. Specifically, the portion of the shallow conduit 3 inserted into the first packer 5 has a first opening in its wall, connecting it to the interior of the bladder surrounding the first packer 5. A high-voltage switch 7 is installed at the outlet of the shallow conduit 3, the point used for injecting the plugging agent.

[0066] To seal the top of the casing annulus, water is first injected through the first opening of the shallow conduit 3 to pressurize the rubber bladder of the first packer 5. This causes the rubber bladder of the first packer 5 to expand outward, gradually bringing the outer wall of the rubber bladder of the first packer 5 into close contact with the inner wall of the casing annulus, thereby sealing the top of the casing annulus. Because a high-pressure switch 7 is installed at the outlet of the shallow conduit 3, it is closed during water injection, preventing the water injected into the rubber bladder from escaping through the outlet of the shallow conduit 3.

[0067] In the present invention and Figure 3 It also includes: if it is a well without surface casing, then a second packer 6 is installed in the outer annulus of the casing, near the bottom of the shallow-level catheter 3, and the outer annulus of the casing of the well without surface casing is separated into upper and lower spaces by the second packer 6; the second packer 6 is connected to the shallow-level catheter 3.

[0068] In an embodiment of the present invention, for a well without a surface casing, before squeezing the plugging agent, a second packer 6 can be installed at the bottom of the shallow-level conduit 3 in the outer annulus of the casing, thereby separating the outer annulus of the casing into upper and lower spaces. When the plugging agent is squeezed through the shallow-level conduit 3, the plugging agent diffuses to the surrounding areas in the upper space of the outer annulus of the casing to prevent it from diffusing downward excessively, and at the same time, when the plugging agent is squeezed through the deep-level conduit 4, the plugging agent is prevented from diffusing to the upper space.

[0069] The structure of the second packer 6 is identical to that of the first packer 5. The shallow and deep conduits 3 and 4 pass through the second packer 6 and are connected to the shallow conduit 3 near its bottom. As the shallow and deep conduits 3 and 4 are lowered, the second packer 6 is lowered into the outer annulus of the casing along with the shallow and deep conduits 3 and 4. When the shallow and deep conduits 3 and 4 reach their designated positions, the second packer 6 is located in the outer annulus of the casing near the bottom of the shallow conduit 3.

[0070] The outer circumference of the second packer 6 is provided with a rubber airbag, the interior of which is connected to the interior of the shallow-level catheter 3 , that is, the shallow-level catheter 3 has a second opening on the wall of the part inserted into the second packer 6 , which is connected to the interior of the airbag on the circumference of the second packer 6 .

[0071] While water is injected into the rubber airbag of the first packer 5 through the shallow catheter 3 to seal the top of the outer annulus of the casing, the water in the shallow catheter 3 is pressurized and injected into the rubber airbag of the second packer 6 through the second opening of the shallow catheter 3, so that the rubber airbag of the second packer 6 expands outward, and the outer wall of the rubber airbag of the second packer 6 gradually fits tightly against the inner wall of the outer annulus of the casing, thereby sealing the outer annulus of the casing near the bottom of the shallow catheter 3, so that the outer annulus of the casing separates the upper and lower spaces.

[0072] As the rubber bladders of the first and second packers 5, 6 are continuously filled with water, the pressure inside the rubber bladders and the shallow conduit 3 continues to rise until it reaches the maximum pressure that the high-pressure switch 7 at the outlet of the shallow conduit 3 can withstand. This opens the high-pressure switch 7, allowing plugging agent to be injected into the annulus outside the casing through the shallow conduit 3. The outlet of the shallow conduit 3 is located on the sidewall of the shallow conduit 3, near the top of the second packer 6.

[0073] Step 4: inject the plugging agent into the outer annulus of the casing through the shallow-level guide tube 3. After the injection is completed, wait for solidification under pressure.

[0074] In the present invention, the method of squeezing plugging agent into the outer annulus of the casing through the shallow-level catheter 3 includes: obtaining a primary squeezing pressure and squeezing volume; and squeezing plugging agent into the outer annulus of the casing through the shallow-level catheter 3 according to the primary squeezing pressure and squeezing volume.

[0075] In the present invention, the method for obtaining the primary squeezing pressure and squeezing volume includes: obtaining the primary squeezing radius, the primary squeezing thickness and the formation porosity; determining the primary squeezing volume according to the primary squeezing radius, the primary squeezing thickness and the formation porosity; obtaining the formation fracture pressure value and the crossflow layer pressure value; and determining the primary squeezing pressure according to the formation fracture pressure and the crossflow layer pressure value.

[0076] In the present invention, the waiting time is 24 to 72 hours.

[0077] In the embodiment of the present invention, when performing a primary injection, the operator should pre-set the area and depth to be injected, including the injection radius and injection thickness. The specific calculation formula for the primary injection volume is: primary injection volume = primary injection radius × primary injection thickness × formation porosity.

[0078] The primary squeeze pressure should be less than the formation fracture pressure and greater than the crossflow zone pressure. A value greater than the crossflow zone pressure is used to seal the crossflow zone and prevent fluid from flowing upward, while a value less than the formation fracture pressure is used to prevent excessive squeeze pressure from leaking out of the formation. The formation fracture pressure, crossflow zone pressure, and formation porosity can be provided by well logging or geological data.

[0079] In this embodiment of the present invention, for example, if the calculated injection volume is 20-30 m³ and the injection pressure is 3-8 MPa, a high-anti-channeling plugging agent is first injected through the shallow conduit 3 at an injection pressure of 3-8 MPa, a displacement rate of 0.3-0.4 m³ / min, and a volume of 20-30 m³ of plugging agent liquid. 1 m³ of fresh water is displaced, the displacement rate is controlled at 0.6-0.8 m³ / min, and the displacement pressure is controlled at 5-8 MPa. After injection is completed, the associated valve is pressurized and allowed to solidify for 24 hours. After the plugging agent is injected into the outer annulus of the casing through the shallow conduit 3, the plugging agent diffuses in the surface soil layer and forms a shielding layer in the surface soil layer after solidification. The plugging agent can be cement.

[0080] Step 5: inject the plugging agent into the outer annulus of the casing through the deep-level pipe 4. After the injection is completed, the plugging agent is solidified under pressure to complete the outer plugging of the oil and water well.

[0081] In the present invention, the method of squeezing plugging agent into the outer annulus of the casing through the deep-level conduit 4 includes: obtaining secondary squeezing pressure and squeezing volume; and squeezing plugging agent into the outer annulus of the casing through the deep-level conduit 4 according to the secondary squeezing pressure and squeezing volume.

[0082] In the present invention, the method for obtaining the secondary squeezing pressure and squeezing volume includes: obtaining the secondary squeezing radius and the secondary squeezing thickness, and determining the secondary squeezing volume based on the secondary squeezing radius, the secondary squeezing thickness and the formation porosity; obtaining the crossflow layer pressure value and the shielding layer pressure value, and determining the secondary squeezing pressure based on the crossflow layer pressure value and the shielding layer pressure value.

[0083] In the embodiment of the present invention, when performing secondary injection, the operator should pre-determine the required injection area and depth, including the injection radius and injection thickness. The specific formula for calculating the secondary injection volume is: secondary injection volume = secondary injection radius × secondary injection thickness × formation porosity. The formation porosity can be provided by well logging or geological data.

[0084] The shielding layer formed after the primary squeeze plugging agent solidifies under pressure will have a pressure greater than the formation fracture pressure and the pressure of the crossflow layer. The secondary squeeze pressure should be greater than the crossflow layer pressure but less than the shielding layer pressure. This ensures that the secondary squeeze can both seal the crossflow layer below and prevent the shielding layer above from breaking through. The formation fracture pressure and crossflow layer pressure can be provided by well logging or geological data.

[0085] In this embodiment of the present invention, for example, if the calculated injection volume is 40-50 m³ and the injection pressure is 8-15 MPa, a high-anti-channeling plugging agent is injected through the deep-stage conduit 4 at an injection pressure of 8-15 MPa, a displacement rate of 0.2-0.5 m³ / min, a volume of 40-50 m³ of plugging agent, 0.5 m³ of fresh water, a displacement rate controlled at 0.5-0.8 m³ / min, and a displacement pressure controlled at 8-13 MPa. After injection is completed, the associated valve is pressurized and allowed to solidify for 24 hours. After the plugging agent is injected into the casing annulus through the deep-stage conduit 4, it diffuses above the channeling layer and forms a plugging layer after solidification, completely blocking the lower channeling layer.

[0086] The purpose of the primary injection through the shallow conduit 3 to form a shielding layer is to prevent excessive pressure during the secondary injection through the deep conduit 4, which could cause the secondary injected plugging agent to diffuse upward and return to the surface. The plugging agent injected through the shallow conduit 3 into the topsoil layer solidifies to form a shielding layer, making the topsoil more pressure-bearing and preventing the plugging agent injected through the deep conduit 4 from diffusing upward and returning to the surface. The plugging agent injected through the deep conduit 4 above the channeling layer solidifies to completely block the underground channeling layer.

[0087] In the present invention, before milling the outer annulus of the casing of the oil and water well to be plugged, the method further includes: performing a pressure reduction treatment on the oil and water well to be plugged; the pressure reduction treatment is: shutting down the oil and water well to be plugged and the surrounding injection wells.

[0088] In an embodiment of the present invention, when plugging an oil and water well with a surface casing 2, it is necessary to first perform a pressure reduction treatment on the oil and water well to be plugged. After the pressure reduction treatment is completed, the crossflow layer and the layer pressure are determined based on the drilling pressure data, combined with the noise logging and temperature logging methods or based on geological data. According to the crossflow layer pressure, a suitable density and viscosity of the well repair fluid are prepared so that it reaches a balance with the formation pressure when milling the outer annulus of the casing. After the well repair fluid is prepared, a milling head and a milling barrel are used to use the prepared well repair fluid to mill the outer annulus of the casing between the casing 1 and the surface casing 2 to 150 meters underground. After the milling of the outer annulus of the casing is completed, a deep-level conduit 4 and a shallow-level conduit 3 are lowered into the outer annulus of the casing, wherein the shallow-level conduit 3 is lowered to a depth of 110 meters, that is, reaching the bottom of the topsoil layer, and the deep-level conduit 4 is lowered to a depth of 150 meters, that is, reaching above the crossflow layer. After the guide tube is lowered, the top of the casing annulus is sealed by welding an iron ring 8 to the casing 1 and the surface casing 2, thereby sealing the top of the casing annulus to prevent the injected plugging agent from flowing back out of the top. The primary injection volume is determined based on the primary injection radius, primary injection thickness, and formation porosity; the primary injection pressure is determined based on the formation fracture pressure and the crossflow layer pressure. Based on the primary injection pressure and injection volume, the plugging agent is squeezed into the casing annulus through the shallow guide tube 3. During injection, the plugging agent diffuses from the casing annulus into the surrounding formation. After the injection is completed and the pressure is set for 24 hours, the plugging agent forms a shielding layer in the surface soil layer. The secondary squeezing volume is determined according to the secondary squeezing radius, the secondary squeezing thickness and the porosity of the formation; the secondary squeezing pressure is determined according to the pressure value of the crossflow layer and the pressure bearing value of the shielding layer, and the plugging agent is squeezed into the outer annulus of the casing through the deep-level guide tube 4 according to the secondary squeezing pressure and the squeezing volume; during the squeezing, the plugging agent diffuses from the outer annulus of the casing to the surrounding formations, and after the squeezing is completed and the pressure is set for 24 hours, the plugging agent forms a plugging layer above the crossflow layer, completely blocking the underground crossflow layer and preventing the fluid in the crossflow layer from flowing back.

[0089] In an embodiment of the present invention, when plugging an oil and water well without a surface casing 2, it is necessary to first perform a pressure reduction treatment on the oil and water well to be plugged. After the pressure reduction treatment is completed, the crossflow layer and the layer pressure are determined based on the drilling pressure data, combined with the noise logging and temperature logging methods or geological data. According to the crossflow layer pressure, a suitable density and viscosity of the well repair fluid are prepared so that it reaches a balance with the formation pressure when milling the outer annulus of the casing. After the well repair fluid is prepared, the milling head and the milling barrel are used to use the prepared well repair fluid to mill the outer annulus of the casing 1 to 150 meters underground. After the milling of the outer annulus of the casing is completed, prepare to lower the deep-level conduit 4 and the shallow-level conduit 3 into the outer annulus of the casing; before lowering the deep-level conduit 4 and the shallow-level conduit 3, the deep-level conduit 4 and the shallow-level conduit 3 are passed through the second packer 6 and the first packer 5 respectively, and the shallow-level conduit 3 is connected to the second packer 6 and the first packer 5 respectively. After connecting the first and second packers 5, 6, the shallow conduit 3 is lowered to a depth of 110 meters, i.e., to the bottom of the topsoil layer, and the deep conduit 4 is lowered to a depth of 150 meters, i.e., to the top of the crossflow layer. At this point, the first packer 5 is located at the top opening of the annulus outside the casing, and the second packer 6 is located in the annulus outside the casing near the bottom of the shallow conduit 3. After the conduits are lowered, water is injected into the first and second packers 5, 6 through the shallow conduit 3 to increase pressure, causing the outer airbags of the first and second packers 5, 6 to expand simultaneously. After the outer airbag of the first packer 5 expands, it blocks the top of the annulus outside the casing to prevent the injected plugging agent from flowing back from the top. After the outer airbag of the second packer 6 expands, it separates the annulus outside the casing into two layers, upper and lower. As water is continuously injected, the pressure inside the first and second packers 5 and the shallow conduit 3 increases continuously. When the pressure reaches the maximum tolerance of the high-pressure switch 7, the high-pressure switch 7 at the outlet of the side wall of the shallow conduit 3 is opened. The primary squeezing volume is determined according to the primary squeezing radius, the primary squeezing thickness and the formation porosity; the primary squeezing pressure is determined according to the formation fracture pressure and the crossflow layer pressure value, and the plugging agent is squeezed into the outer annulus of the casing through the shallow conduit 3 according to the primary squeezing pressure and the squeezing volume; during squeezing, the plugging agent flows out of the outlet of the shallow conduit 3, in the outer annulus of the casing above the second packer 6, and diffuses into the surrounding formations. After the squeezing is completed and the pressure is set for 24 hours, the plugging agent forms a shielding layer in the topsoil layer. The secondary squeezing volume is determined according to the secondary squeezing radius, the secondary squeezing thickness and the porosity of the formation; the secondary squeezing pressure is determined according to the pressure value of the crossflow layer and the pressure bearing value of the shielding layer, and the plugging agent is squeezed into the outer annulus of the casing through the deep-level guide tube 4 according to the secondary squeezing pressure and the squeezing volume; during the squeezing, the plugging agent diffuses from the outer annulus of the casing to the surrounding formations, and after the squeezing is completed and the pressure is set for 24 hours, the plugging agent forms a plugging layer above the crossflow layer, completely blocking the underground crossflow layer and preventing the fluid in the crossflow layer from flowing back.

[0090] The present invention squeezes out the plugging agent once through the shallow conduit 3, forming a shielding layer on the upper part of the stratum to prevent the plugging agent from flowing back when squeezed out for the second time by the deep conduit 4; then squeezes out a large-volume, high-pressure plugging agent through the deep conduit 4, so that it forms a counter-current with the fluid in the lower crossflow layer, preventing it from flowing back, and forms a plugging layer above the crossflow layer after solidification, thereby blocking the crossflow layer and effectively blocking and controlling the wellbore outside the pipe. The top of the annulus outside the casing is blocked by using annular iron 8 or a first packer 5 for wells with surface casing and wells without surface casing, respectively, to prevent the plugging agent from flowing back upward. The annulus outside the casing is separated into upper and lower spaces by the second packer 6, so that the plugging agent injected by the shallow conduit 3 can diffuse to the surroundings in the upper space, preventing it from diffusing too much downward from the annulus outside the casing.

[0091] The present invention optimizes the design for the construction of sealing and controlling leaks in oil and water well repair operations, thereby resolving the problems of resource waste and environmental pollution caused by leaks in oil and water wells, as well as the potential safety hazards caused by leaking wells. It reduces construction risks, speeds up construction, ensures the safety of oil and water wells, and achieves effective sealing and controlling of leaks in oil and water well pipes.

[0092] The above-described embodiments are merely embodiments of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications, equivalent substitutions, and improvements without departing from the scope of the present invention, and these modifications fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be based on the appended claims.

Claims

1. A method for plugging an external pipe leak in an oil or water well, characterized in that: Including steps: Milling the outer annulus of the oil and water well casing to be sealed; Running a double row of conduits into the outer annulus of the casing, including a shallow-level conduit and a deep-level conduit; To seal the top of the outer annulus of the oil and water well casing to be blocked; injecting the plugging agent into the outer annulus of the casing through a shallow-level guide tube, and then solidifying the plugging agent under pressure after the injection is completed; The plugging agent is squeezed into the outer annulus of the casing through a deep-level pipe. After the squeezing is completed, the plugging agent is solidified under pressure to complete the outer plugging of the oil and water well.

2. The method for externally plugging an externally vented pipe in an oil and water well according to claim 1, characterized in that: The method for sealing the top of the outer annulus of the oil and water well casing to be blocked comprises: Determine whether the oil and water well is a surface cased well or an unsurface cased well; If it is a well with surface casing, then at the top of the outer annulus of the casing, the casing and the surface casing are welded with an iron ring to seal the top of the outer annulus of the oil and water well casing through the iron ring; If it is a well without surface casing, a first packer is installed at the top of the outer annulus of the casing to seal the top of the outer annulus of the oil and water well casing. The first packer is connected to the shallow-level conduit, and a high-pressure switch is installed at the outlet of the shallow-level conduit.

3. The method for externally plugging an externally vented pipe in an oil or water well according to claim 2, characterized in that: Also includes: If the well is uncased, a second packer is installed in the outer annulus of the casing, near the bottom of the shallow-stage casing, so that the outer annulus of the casing of the uncased well is separated into upper and lower spaces by the second packer; The second packer is connected to the shallow-stage conductor.

4. The method for externally plugging an external pipe in an oil or water well according to any one of claims 1 to 3, characterized in that: The method for milling the outer annulus of the oil and water well casing to be blocked comprises: Obtain the pressure value of the crossflow layer of the oil and water well to be plugged; Adjusting the density and viscosity of the workover fluid according to the crossflow layer pressure value; Use the prepared workover fluid to mill the outer annulus of the casing.

5. The method for externally plugging an externally vented pipe in an oil or water well according to claim 1, characterized in that: The method of injecting a plugging agent into the outer annulus of the casing through a shallow-level conduit comprises: Obtain the squeeze pressure and squeeze volume of one shot; According to the primary squeezing pressure and squeezing volume, squeezing the plugging agent into the outer annulus of the casing through the shallow-level conduit; The method of injecting a plugging agent into the outer annulus of the casing through a deep-level conduit comprises: Obtain secondary extrusion pressure and extrusion volume; According to the secondary squeezing pressure and squeezing volume, the plugging agent is squeezed into the outer annulus of the casing through the deep-stage conduit.

6. The method for externally plugging an externally vented pipe in an oil or water well according to claim 5, characterized in that: The method for obtaining the primary extrusion pressure and extrusion volume includes: Obtaining a primary squeezing radius, a primary squeezing thickness, and a formation porosity, and determining a primary squeezing volume based on the primary squeezing radius, the primary squeezing thickness, and the formation porosity; Obtaining a formation fracture pressure value and a crossflow layer pressure value, and determining the primary squeeze pressure according to the formation fracture pressure and the crossflow layer pressure value; The method for obtaining the secondary extrusion pressure and extrusion volume includes: Obtaining a secondary squeezing radius and a secondary squeezing thickness, and determining a secondary squeezing amount according to the secondary squeezing radius, the secondary squeezing thickness, and the formation porosity; The crossflow layer pressure value and the shielding layer pressure value are obtained, and the secondary extrusion pressure is determined according to the crossflow layer pressure value and the shielding layer pressure value.

7. The method for externally plugging an external pipe in an oil and water well according to claim 1, characterized in that: Before the milling of the outer annulus of the oil and water well casing to be blocked, the method further comprises: Carry out pressure reduction treatment on oil and water wells to be plugged; The pressure reduction process is as follows: Shut down the oil and water wells to be sealed and the surrounding injection wells.

8. The method for externally plugging an externally vented pipe in an oil or water well according to any one of claims 1 to 3 and 5 to 7, characterized in that: The shallow-level conduit is lowered to a depth that reaches the bottom of the topsoil layer; The deep-stage conduit is lowered to a depth above the crossflow layer.

9. The method for externally plugging an externally vented pipe in an oil or water well according to any one of claims 1 to 3 and 5 to 7, characterized in that: The waiting time for solidification is 24 to 72 hours.

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