Cement plug injection device and cement plug injection method based on double-wall drill pipe system

Abstract

The invention provides a cement plug injection device and method based on a double-wall drill pipe system. The cement plug injection device comprises a slurry pump for supplying power to drive slurry; the top drive is connected with the slurry pump; the gas-liquid double-injection adapter is connected with the top drive; the double-wall drill rod, the underground mixer and the conventional single-arm drill rod are arranged at the lower end of the gas-liquid double-injection adapter; the gas generating device is connected with the gas-liquid double-injection adapter; the blowout preventer group is arranged at the wellhead position; and the rotary blowout prevention flow guide device is arranged at the top end of the blowout preventer group. The method is flexible in application, the wellbore annulus profile pressure can be adjusted through the double-wall drill rod depth or the gas injection amount, and the cement plug injection success rate is increased; the device is simple in structure and high in control precision, can accurately control the bottom hole pressure, reduces the probability of well leakage or well kick, and guarantees the drilling well control and drilling safety requirements in the field of oil drilling.

Description

Technical Field

[0001] The invention relates to the technical field of drilling, and in particular to a cementing plug device and a cementing plug method based on a double-wall drill pipe system. Background Art

[0002] Cement plugging refers to the operation of injecting cement slurry at appropriate positions in the well to form a cement plug. The cement plug finally formed by cement plugging must meet the requirements of the owner (such as cement plug surface depth, cement plug length, cement plug strength, etc.). In recent years, many wells have been affected by vicious loss of return during the drilling process in fields such as geothermal drilling and oil drilling, which seriously restricts the drilling progress and the drilling rate of the formation. If there are serious leakage, fish that cannot be fished out, formation collapse, well deviation exceeding the standard, and the purpose of drilling is changed during the drilling process, it is necessary to inject cement plugs to plug the leakage or backfill the lower formation and then side-drill. In the case of serious formation leakage, it is common for cement plugging operations to easily cause poor quality of cement plugs or failure to form cement plugs. The success rate of cement plugging is low, and the accuracy of bottom hole pressure control is not high, which makes it difficult to guarantee the drilling well control and drilling safety requirements in the field of oil drilling. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a cement plugging device and method based on a double-wall drill pipe system which is flexible in application and improves the success rate of cement plugging.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0005] A cementing plug device based on a double-wall drill pipe system, comprising:

[0006] a mud pump that provides power to drive the mud;

[0007] a top drive connected to the mud pump;

[0008] A gas-liquid dual injection adapter connected to the top drive;

[0009] A double-wall drill pipe, a downhole mixer, and a conventional single-arm drill pipe are arranged at the lower end of the gas-liquid dual injection adapter and are connected in sequence;

[0010] A gas generating device connected to the gas-liquid dual injection adapter;

[0011] A blowout preventer group installed at the wellhead;

[0012] And a rotating blowout prevention and flow guiding device is arranged at the top of the blowout preventer group, and the rotating blowout prevention and flow guiding device is connected to the mud pump.

[0013] As a further improvement of the above technical solution:

[0014] It also includes a mud gas separator and a vibrating screen. The input end of the mud gas separator is connected to the rotating blowout prevention and diversion device, and the output end of the mud gas separator includes an exhaust port and a drain port. The drain port of the mud gas separator is connected to the vibrating screen, and the vibrating screen is connected to a mud pump.

[0015] It also includes a cementing pump, and the cementing pump is connected to the top drive.

[0016] The gas-liquid dual injection adapter is provided with a gas channel A and a liquid channel A, the double-wall drill pipe is provided with a gas channel B and a liquid channel B, and the downhole mixer is provided with a gas channel C and a liquid channel C; the mud pump output end is connected to the top drive input end, the top drive output end is connected to the liquid channel A input end, the liquid channel A output end is connected to the liquid channel B, the liquid channel B output end is connected to the liquid channel C input end, and the liquid channel C output end is connected to a conventional single-arm drill pipe.

[0017] The output end of the gas generating device is connected to the input end of the gas channel A, the output end of the gas channel A is connected to the input end of the gas channel B, and the output end of the gas channel B is connected to the input end of the gas channel C.

[0018] A cement plugging method based on a double-wall drill pipe system, using the cement plugging device based on the double-wall drill pipe system, comprises the following steps:

[0019] a: Calculate the target bottom hole pressure that needs to be maintained for double-wall drill pipe aerated drilling based on the formation pressure-related parameters, annular mud level and formation stability data. The target bottom hole pressure is greater than the higher value of the formation pore pressure and collapse pressure and less than the formation loss pressure value;

[0020] b: Design the mud displacement, gas displacement, double-wall drill pipe lowering depth, and throttling casing pressure adjustment range required for mud lifting according to the actual wellbore structure, drilling tool parameters, mud properties and target bottom hole pressure;

[0021] c: According to the measured well diameter and the formation conditions that need to be plugged, determine the well section that needs to be plugged with cement plugs, and calculate the required cement slurry properties and volume;

[0022] d. Make a cement plug skeleton and send the cement plug skeleton to the predetermined cement plug injection position;

[0023] e: Place the double-wall drill pipe to the required depth in the well, ensure that there is no square excess in the square drill pipe, and the position of the lower joint in the drill bit assembly does not exceed the position of the predetermined cement plug. Connect the corresponding pipelines and drainage pipelines of the cementing pump, connect the double-wall drill pipe to the gas-liquid dual injection adapter, and measure and record the static water level; the static water level refers to the stable liquid level of the drilling fluid in the annulus, which can be measured by observing the water mark when pulling out the drill.

[0024] f: Turn on the gas generator and inject the designed displacement of gas. The gas passes through gas channel A, gas channel B and gas channel C in turn to reach the wellbore annulus, lift the mud and return upward. When mud is seen returning from the vibrating screen outlet, turn on the mud pump to inject the designed displacement of mud. The mud passes through the top drive, liquid channel A, liquid channel B, liquid channel C, and conventional single-wall drill pipe in turn to enter the wellbore annulus and return upward. When it reaches the position of the downhole mixer, the gas lifts the mud and continues to return upward. The gas generator is turned off after the designed displacement of gas is injected, and the mud pump is turned off after the designed displacement of mud is injected;

[0025] g: Start the mud pump at a low displacement and the gas generator at the same time, measure the changes in the liquid level of each mud tank, measure the displacement under no leakage and slight leakage respectively, and then determine the displacement of the injected cement slurry, the displacement of the replacement slurry and the displacement and gas injection of the subsequent circulation and waiting period, to ensure that the formation leaks slightly during injection and replacement, and that there is no leakage and no water in the formation during the circulation gas lift;

[0026] h: Adjust the displacement to a displacement that does not leak or produce water in the wellbore, turn off the mud pump, turn on the gas generator to keep injecting gas, and use the cementing pump to pump in cement slurry at the same time, ensuring that the cement slurry is pumped in continuously without stopping, and the cement slurry injection process is in a state of slight leakage;

[0027] i: After pumping in cement slurry, immediately reverse the gate, and the slurry pump replaces the mud drilling fluid that is larger than the volume of the drilling tool according to the determined displacement. After the slurry is replaced, stop the mud pump, turn on the gas generator to keep injecting gas, and reduce the gas injection volume until there is leakage. At this time, the cement slurry should come out of the casing shoe, and then the drilling tool is lifted up to the first drill pipe male joint to get the square bushing without stopping the gas;

[0028] j: Keep the gas generator injecting gas, start the mud pump, adjust the displacement and gas injection volume to the displacement and gas injection volume of the previously measured no-leakage state, start the gas generator and mud pump and circulate for 6 to 8 hours before stopping;

[0029] k: After the cement plug solidifies, measure the position of the cement plug. If the upper surface of the cement plug is below the desired sealing position, perform a second cement plug injection and repeat steps h to k until the cement plug surface is above the desired sealing well section.

[0030] As a further improvement of the above technical solution:

[0031] In step d, the cement plug skeleton includes cotton wool and wool, and the cotton wool and wool are made into a strip-shaped cement plug skeleton with an outer diameter suitable for the size of the well and a length of 0.3-0.8 meters;

[0032] In step i, turn on the gas generating device to maintain gas injection, and reduce the gas injection volume until the leakage volume reaches 2 cubic meters.

[0033] In step i, the mud pump replaces the mud drilling fluid with a determined displacement volume that is greater than the inner volume of the drilling tool, and the displacement volume is 0.5 to 1 cubic meter greater than the inner volume of the drilling tool.

[0034] In step k, the position of the cement plug is measured 12 hours after the cement plug is injected.

[0035] Compared with the prior art, the advantages of the present invention are:

[0036] (1) Flexible application, the annular profile pressure of the wellbore can be adjusted by the depth of the double-wall drill pipe or the amount of gas injection; (2) Reduce leakage and improve the success rate of cementing plugs; (3) High control accuracy, can accurately control the bottom hole pressure, reduce the probability of leakage or well kick, and ensure the drilling well control and drilling safety requirements in the oil drilling field. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0038] Figure 1 It is a schematic diagram of the structure and installation position of the cement plug device of the present invention.

[0039] The symbols in the figure represent:

[0040] 1. Mud pump; 2. Top drive; 3. Gas-liquid dual injection adapter; 4. Gas generator; 5. Double-wall drill pipe; 6. Rotary blowout prevention and diversion device; 7. BOP group; 8. Casing; 9. Downhole mixer; 10. Open hole formation; 11 Required cementing section; 12. Conventional single-wall drill pipe; 13. Mud gas separator; 14. Vibrating screen B; 15. Cementing pump; 30. Liquid channel A; 31. Gas channel A; 50. Gas channel B; 51. Liquid channel B; 90. Gas channel C; 91. Liquid channel C; DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereby.

[0042] like Figure 1 As shown, the cementing plug device based on the double-wall drill pipe system of this embodiment includes:

[0043] A mud pump 1 that provides power to drive mud; a top drive 2 connected to the mud pump 1; a gas-liquid dual injection adapter 3 connected to the top drive 2; a double-wall drill pipe 5, a downhole mixer 9, and a conventional single-arm drill pipe 12 that are arranged at the lower end of the gas-liquid dual injection adapter 3 and are connected in sequence; a gas generator 4 connected to the gas-liquid dual injection adapter 3; a blowout preventer group 7 arranged at the wellhead position; and a rotating blowout preventer guide device 6 arranged at the top of the blowout preventer group 7, and the rotating blowout preventer guide device 6 is connected to the mud pump 1. The device is flexible in application and can adjust the wellbore annulus profile pressure by the depth of the double-wall drill pipe or the amount of gas injection.

[0044] In this embodiment, a mud gas separator 13 and a vibrating screen 14 are also included. The input end of the mud gas separator 13 is connected to the rotating blowout prevention and diversion device 6, and the output end of the mud gas separator 13 includes an exhaust port and a drain port. The drain port of the mud gas separator 13 is connected to the vibrating screen 14, and the vibrating screen 14 is connected to the mud pump 1.

[0045] In this embodiment, a cementing pump 15 is also included, and the cementing pump 15 is connected to the top drive 2 .

[0046] In this embodiment, the gas-liquid dual injection adapter 3 is provided with a gas channel A31 and a liquid channel A30, the double-wall drill pipe 5 is provided with a gas channel B50 and a liquid channel B51, and the downhole mixer 9 is provided with a gas channel C90 and a liquid channel C91; the output end of the mud pump 1 is connected to the input end of the top drive 2, the output end of the top drive 2 is connected to the input end of the liquid channel A30, the output end of the liquid channel A30 is connected to the liquid channel B51, the output end of the liquid channel B51 is connected to the input end of the liquid channel C91, and the output end of the liquid channel C91 is connected to the conventional single-arm drill pipe 12.

[0047] In this embodiment, the output end of the gas generating device 4 is connected to the input end of the gas channel A31, the output end of the gas channel A31 is connected to the input end of the gas channel B50, and the output end of the gas channel B50 is connected to the input end of the gas channel C90.

[0048] The cement plugging method based on the double-wall drill pipe system of this embodiment adopts a cement plugging device based on the double-wall drill pipe system, and includes the following steps:

[0049] a: Calculate the target bottom hole pressure that needs to be maintained for double-wall drill pipe aerated drilling based on the formation pressure-related parameters, annular mud level and formation stability data. The target bottom hole pressure is greater than the higher value of the formation pore pressure and collapse pressure and less than the formation loss pressure value;

[0050] Conduct electrical logging of the wellbore to record the borehole diameter and water layer distribution of the open hole section. According to the borehole diameter and water layer position, determine the well section for cement plugging, such as Hm~Hn. The electrical logging borehole diameter data of this well section is (hi, Di), where Di is the borehole diameter at the depth of hi.

[0051] Calculate the volume of cement slurry injected. The volume of cement slurry injected is calculated according to the following formula:

[0052]

[0053] Calculate the depth H of the double-wall drill pipe by using two-phase flow calculation software;

[0054] b: Design the mud displacement, gas displacement, double-wall drill pipe lowering depth, and throttling casing pressure adjustment range required for mud lift based on the actual wellbore structure, drilling tool parameters, mud properties, and target bottom hole pressure; the above parameters can be calculated by Drillbench software.

[0055] c: According to the measured well diameter and the formation conditions that need to be plugged, determine the well section that needs to be plugged with cement plugs, and calculate the required cement slurry properties and volume;

[0056] d. Make a cement plug skeleton and send the cement plug skeleton to the predetermined cement plug injection position;

[0057] e: Place the double-wall drill pipe 5 to the required depth in the well, ensure that the square drill pipe has no square excess, and the position of the lower joint in the drilling tool assembly does not exceed the position of the predetermined cementing plug, connect the corresponding pipelines and drainage pipelines of the cementing pump 15, connect the double-wall drill pipe 5 and the gas-liquid dual injection adapter 3, and measure and record the static water level;

[0058] f: Turn on the gas generating device 4, inject the gas of designed displacement, the gas passes through the gas channel A31, the gas channel B50 and the gas channel C90 in turn to reach the borehole annulus, lift the mud and return upward, when the mud is seen returning out of the vibrating screen 14 outlet, turn on the mud pump 1 to inject the mud of designed displacement, the mud passes through the top drive 2, the liquid channel A30, the liquid channel B51, the liquid channel C91, the conventional single-wall drill pipe 12 in turn to enter the borehole annulus and return upward, reaching the position of the downhole mixer 9, the gas lifts the mud to continue to return upward; the gas generating device is closed after completing the injection of the designed displacement of gas, and the mud pump is closed after completing the injection of the designed displacement of mud; as shown in the attached figure, the arrow indicates the movement direction of the gas or liquid.

[0059] g: Start the mud pump 1 at a low displacement, start the gas generating device 4 at the same time, measure the change of the liquid level of each mud tank, measure the displacement under the state of no leakage and slight leakage respectively, and then determine the displacement of the injected cement slurry, the displacement of the replacement slurry and the displacement and gas injection of the subsequent circulation and waiting for solidification, to ensure that there is slight leakage in the formation during injection and replacement, and no leakage and water discharge from the formation during the circulation gas lift; mud tank refers to the container of the reservoir mud on site.

[0060] h: Adjust the displacement to a displacement that does not leak or discharge water from the wellbore, turn off the mud pump 1, turn on the gas generator 4 to keep injecting gas, and use the cementing pump 15 to pump in cement slurry at the same time, ensuring that the cement slurry is pumped in continuously without stopping, and the cement slurry injection process is in a state of slight leakage;

[0061] i: After the cement slurry is pumped in, the gate is immediately reversed. The slurry pump 1 replaces the mud drilling fluid that is larger than the volume of the drilling tool according to the determined displacement. After the slurry is replaced, the mud pump 1 is stopped, and the gas generator 4 is turned on to keep injecting gas. The gas injection volume is reduced until there is leakage. At this time, the cement slurry should come out of the casing shoe. Then, without stopping the gas, the drilling tool is lifted up to the first drill pipe male joint to get the square bushing out.

[0062] j: Keep the gas generator 4 injecting gas, start the mud pump 1, adjust the displacement and gas injection volume to the displacement and gas injection volume of the previously measured no-leakage state, start the gas generator 4 and the mud pump 1 and circulate for 6 to 8 hours before stopping;

[0063] k: After the cement plug solidifies, measure the position of the cement plug. If the upper surface of the cement plug is below the desired sealing position, perform a second cement plug injection and repeat steps h to k until the cement plug surface is above the desired sealing well section.

[0064] In this embodiment, in step d, the cement plug skeleton includes cotton wool and wool, which are made into a strip-shaped cement plug skeleton with an outer diameter suitable for the size of the well and a length of 0.3-0.8 meters. The cement plug skeleton can also be made of chemical fiber materials.

[0065] In this embodiment, in step i, the gas generating device 4 is turned on to maintain gas injection, and the gas injection volume is reduced until the leakage volume reaches 2 cubic meters.

[0066] In this embodiment, in step i, the mud pump 1 replaces the mud drilling fluid with a displacement volume greater than the inner volume of the drilling tool, and the displacement volume is 0.5 to 1 cubic meter greater than the inner volume of the drilling tool.

[0067] In this embodiment, in step k, the position of the cement plug is measured 12 hours after the cement plug is injected.

[0068] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cementing plug device based on a double-wall drill pipe system, It is characterized in that include: A mud pump (1) for providing power to drive the mud; A top drive (2) connected to the mud pump (1); A gas-liquid dual injection adapter (3) connected to the top drive (2); A double-wall drill pipe (5), a downhole mixer (9), and a conventional single-arm drill pipe (12) are arranged at the lower end of the gas-liquid dual injection adapter (3) and are connected in sequence; A gas generating device (4) connected to the gas-liquid dual injection adapter (3); A blowout preventer group (7) arranged at the wellhead; And a rotating blowout prevention flow guide device (6) arranged at the top of the blowout preventer group (7), wherein the rotating blowout prevention flow guide device (6) is connected to the mud pump (1).

2. The cementing plug device based on the double-wall drill pipe system according to claim 1, It is characterized in that It also comprises a mud gas separator (13) and a vibrating screen (14); the input end of the mud gas separator (13) is connected to the rotating blowout prevention and diversion device (6); the output end of the mud gas separator (13) comprises an exhaust port and a liquid discharge port; the liquid discharge port of the mud gas separator (13) is connected to the vibrating screen (14); and the vibrating screen (14) is connected to the mud pump (1).

3. The cementing plug device based on the double-wall drill pipe system according to claim 2, It is characterized in that It also comprises a cementing pump (15), wherein the cementing pump (15) is connected to the top drive (2).

4. The cementing plug device based on the double-wall drill pipe system according to claim 3, It is characterized in that The gas-liquid dual injection adapter (3) is provided with a gas channel A (31) and a liquid channel A (30), the double-wall drill pipe (5) is provided with a gas channel B (50) and a liquid channel B (51), and the downhole mixer (9) is provided with a gas channel C (90) and a liquid channel C (91); the output end of the mud pump (1) is connected to the input end of the top drive (2), the output end of the top drive (2) is connected to the input end of the liquid channel A (30), the output end of the liquid channel A (30) is connected to the liquid channel B (51), the output end of the liquid channel B (51) is connected to the input end of the liquid channel C (91), and the output end of the liquid channel C (91) is connected to a conventional single-arm drill pipe (12).

5. The cementing plug device based on the double-wall drill pipe system according to claim 3, It is characterized in that The output end of the gas generating device (4) is connected to the input end of the gas channel A (31), the output end of the gas channel A (31) is connected to the input end of the gas channel B (50), and the output end of the gas channel B (50) is connected to the input end of the gas channel C (90).

6. A cement plugging method based on a double-wall drill pipe system, It is characterized in that The cement plug device based on the double-wall drill pipe system as described in any one of claims 1 to 5 comprises the following steps: a: Calculate the target bottom hole pressure that needs to be maintained for double-wall drill pipe aerated drilling based on the formation pressure-related parameters, annular mud level and formation stability data. The target bottom hole pressure is greater than the higher value of the formation pore pressure and collapse pressure and less than the formation loss pressure value; b: Design the mud displacement, gas displacement, double-wall drill pipe lowering depth, and throttling casing pressure adjustment range required for mud lifting according to the actual wellbore structure, drilling tool parameters, mud properties and target bottom hole pressure; c: According to the measured well diameter and the formation conditions that need to be plugged, determine the well section that needs to be plugged with cement plugs, and calculate the required cement slurry properties and volume; d. Make a cement plug skeleton and send the cement plug skeleton to the predetermined cement plug injection position; e. Place the double-wall drill pipe (5) to the required depth in the well, ensure that the square drill pipe has no excess squareness, and the position of the lower joint in the drilling tool assembly does not exceed the position of the predetermined cementing plug, connect the corresponding pipelines and drainage pipelines of the cementing pump (15), connect the double-wall drill pipe (5) and the gas-liquid dual injection adapter (3), and measure and record the static water level; f: Turn on the gas generator (4) and inject the designed displacement of gas. The gas passes through the gas channel A (31), the gas channel B (50) and the gas channel C (90) in sequence to reach the wellbore annulus, lifts the mud and returns upward. When mud is seen returning from the vibrating screen (14) outlet, turn on the mud pump (1) and inject the designed displacement of mud. The mud passes through the top drive (2), the liquid channel A (30), the liquid channel B (51), the liquid channel C (91) and the conventional single-wall drill pipe (12) in sequence to enter the wellbore annulus and return upward. When it reaches the position of the downhole mixer (9), the gas lifts the mud and continues to return upward. The gas generator (4) is turned off after the designed displacement of gas is injected, and the mud pump (1) is turned off after the designed displacement of mud is injected. g: Start the mud pump (1) at a low displacement and start the gas generating device (4) at the same time, measure the change of the liquid level in each mud tank, measure the displacement in the state of no leakage and slight leakage respectively, and then determine the displacement of the injected cement slurry, the displacement of the replacement slurry and the displacement and gas injection volume of the subsequent circulation and waiting for setting, to ensure that the formation has slight leakage during injection and replacement, and that there is no leakage and no water in the formation during the circulation gas lift; h: Adjust the displacement to a displacement that does not leak or discharge water from the wellbore, turn off the mud pump (1), turn on the gas generator (4) to keep injecting gas, and use the cementing pump (15) to pump in cement slurry at the same time, ensuring that the cement slurry is pumped in continuously without interruption, and that there is a slight leakage during the cement slurry injection process; i: After the cement slurry is pumped in, the gate is immediately closed, and the slurry pump (1) replaces the mud drilling fluid with a volume greater than the volume of the drilling tool at a determined displacement volume. After the slurry is replaced, the slurry pump (1) is stopped, and the gas generator (4) is turned on to keep injecting gas. The gas injection volume is reduced until there is leakage. At this time, the cement slurry should come out of the casing shoe. Then, without stopping the gas, the drilling tool is lifted up until the first drill pipe male joint is provided with a square bushing; j: Keep the gas generating device (4) injecting gas, start the mud pump (1), adjust the displacement and gas injection volume to the displacement and gas injection volume of the previously measured no-leakage state, start the gas generating device (4) and the mud pump (1) and circulate for 6 to 8 hours before stopping; k: After the cement plug solidifies, measure the position of the cement plug. If the upper surface of the cement plug is below the desired sealing position, perform a second cement plug injection and repeat steps h to k until the cement plug surface is above the desired sealing well section.

7. A cement plugging method based on a double-wall drill pipe system according to claim 6, It is characterized in that In step d, the cement plug skeleton includes cotton wool and wool, and the cotton wool and wool are made into a strip-shaped cement plug skeleton with an outer diameter suitable for the size of the well and a length of 0.3-0.8 meters.

8. A cement plugging method based on a double-wall drill pipe system according to claim 6, It is characterized in that In step i, the gas generating device (4) is turned on to maintain gas injection, and the gas injection volume is reduced until the leakage volume reaches 2 cubic meters.

9. A cement plugging method based on a double-wall drill pipe system according to claim 6, It is characterized in that In step i, the mud pump (1) replaces the mud drilling fluid with a determined displacement volume which is greater than the inner volume of the drilling tool, and the displacement volume is 0.5 to 1 cubic meter greater than the inner volume of the drilling tool.

10. A cement plugging method based on a double-wall drill pipe system according to claim 6, It is characterized in that In step k, the position of the cement plug is measured 12 hours after the cement plug is injected.

Images