Method for plugging and strengthening casing in annulus B of oil and gas wells

Abstract

The invention discloses a method for plugging and reinforcing the B annulus casing of an oil, gas and water well, comprising the following steps: oil layer casing pressure test; casing integrity detection; pressure drilling; annulus cleaning and detection; flushing and cementing; pressurization and solidification; recovery and completion. Compared with the prior art, the advantages of the invention are: first, low risk, no need for hot work, and effectively eliminating the risks of fire, explosion, and personal injury; second, it is guaranteed, through the inspection and detection technology and the annulus flushing process technology, the accumulated liquid and debris in the B annulus are thoroughly cleaned, and the corrosion situation in the annulus is checked, thereby reducing the risk factors to the greatest extent and improving the construction quality; third, the rectification is thorough, and the new sealing material displacement process technology is through the special pipeline into the B annulus, and the configured new sealing material is displaced into the annular space by using special integrated equipment, so as to fill the missing cement ring in the B annular space, thereby achieving the goal of controlling hidden dangers; fourth, the material performance is good.

Description

Technical Field

[0001] The present invention relates to the technical field of oil casing reinforcement, and specifically refers to a method for plugging and reinforcing the casing in annulus B of oil and gas wells. Background Technique

[0002] When completing wells in heavy oil blocks, although the cement return height in the casing is designed to reach the ground during cementing, due to the following reasons, there are differences in the cement return height in the wellhead oil-casing annulus: First, due to the formation pressure difference (objective), there is shallow leakage and subsidence during the setting of the cement slurry; second, the water molecules that fail to react with calcium silicate during the setting of the cement slurry produce a free phenomenon, forming a free water layer at the top of the cement sheath; third, in the middle and late stages of development, the casing is affected by the alternating thermal stress load caused by high temperature and high pressure. When injecting steam, the high temperature causes the casing to thermally expand and elongate, resulting in local thermal stress deformation; when the injection stops, the contraction of the casing causes structural damage to the thermally stressed deformation part, and gaps appear between the oil casing and the cement sheath during the repeated expansion and contraction process.

[0003] Due to the differences in the cement return height, the following situations occur at the wellhead during steam injection and production: First, the oil casing rises during steam injection; second, flashing and spraying occur when the annulus at the wellhead accumulates liquid during steam injection; third, the production tree at the wellhead shakes.

[0004] Hazard analysis: First, it causes damage to the casing. During steam injection, the oil casing is affected by the alternating thermal stress load and is repeatedly stretched, making it extremely prone to metal fatigue, gradually weakening the compressive strength of the oil casing, and seriously shortening its service life; the absence of the cement sheath in annulus B causes the casing body to be exposed to the air, and the exposed casing body reacts electrochemically with water and air, resulting in rust pits, oxides, etc. on the casing body, and the mechanical properties such as the strength, plasticity, and toughness of the casing steel also significantly decrease.

[0005] Second, it causes damage to the wellhead equipment. The shaking of the oil casing easily damages the pumping unit and the production tree during the production process, causing abnormal wear and tear and resulting in leakage. The time consumed for repairing or replacing the production tree seriously affects the progress of production and development.

[0006] Third, there are safety hazards. Since the wellhead is in a high-temperature and high-pressure state during steam injection. In this case, the rise of the oil casing will cause abnormal stress in the steam injection pipeline, easily leading to the bursting of the high-temperature and high-pressure steam injection pipeline and causing personal injuries; the casing body is exposed in annulus B and is in a high-temperature environment, accelerating oxidation and corrosion, and easily causing safety accidents.

[0007] Fourth, there are environmental risks. The liquid accumulated in the B annulus flashes and sprays due to high temperature, which causes the wellhead Christmas tree and pumping unit to be contaminated. The subsequent cleaning of oil pollution is difficult and the cost is high. If the splashing is serious, it will cause serious environmental pollution in the waters, farmlands, and reed fields around the well site.

[0008] The conventional treatment methods are as follows: cutting the annular steel plate; vacuuming the oil in the B annulus; pouring mortar; and re-welding the annular steel plate.

[0009] Conventional treatment methods have the following risks: First, safety risks. During construction, multiple teams such as electric welding teams, pumping trucks, pollution cleaning personnel, and work teams need to cooperate with each other. During on-site construction, the work site is difficult to manage, and cross-operation is very likely to cause personal injury, and there are great safety risks; the wellhead B annulus is a semi-enclosed space, which may contain flammable, explosive, toxic and harmful media such as oil, gas, and hydrogen sulfide. If the annular steel plate is cut rashly, there will be risks of fire, explosion, and poisoning; there is a lack of cement ring in the well, and the stress of the oil layer casing is all concentrated on the annular steel plate. If the annular steel plate is cut rashly, it will cause the annular steel plate to collapse and cause personal injury. The second is the quality problem. Since the maximum working depth of the suction equipment is 5-7 meters, sewage and oil beyond this depth cannot be pumped out, resulting in only 5-7 meters of ash columns when pouring mortar in the later stage. There is still a missing cement ring under the ash column, and the requirements for thorough rectification of hidden dangers cannot be met; a layer appears between the ash column and the original cement hard surface. When the sewage and dirty oil in the layer boil and volatilize under the high temperature state of the later steam injection, a high-pressure air cavity is formed in the layer, which increases the safety hazard. Summary of the invention

[0010] In order to solve the above-mentioned various problems, the present invention provides a method for plugging and reinforcing annulus casing of oil, gas and water well B.

[0011] In order to solve the above technical problems, the technical solution of the present invention is: a method for plugging and reinforcing annulus casing of oil, gas and water well B, comprising the following steps:

[0012] S1. Oil layer casing pressure test: First, conduct leak detection construction on the oil layer casing above the oil layer to ensure that there is no physical damage to the oil layer casing. Use the combination of the Y521 plug and the oil pipe string to test the casing above the oil layer. The pressure is 15Mpa, and the pressure is maintained for 30 minutes. The pressure drop is less than or equal to 0.5Mpa before continuing to the next step of construction. If the pressure test fails, the casing leak point needs to be found, the casing above the leak point needs to be removed, the buckle is back to the well, and then the next step of operation is carried out;

[0013] S2. Casing integrity inspection: Use electromagnetic flaw detector to inspect the oil layer casing above the cement return height, and evaluate the current quality status of the casing. If the casing is severely corroded, replace the casing first, and then carry out plugging and reinforcement operations after replacing the casing;

[0014] S3. Under-pressure hole opening: Install a hole-opening clamp, a connecting valve, and a hole-opening device 200 mm below the annular steel plate sealing iron; connect a nitrogen cylinder or a water pressure pump through a vent valve, and inject a protective gas or liquid into the inside of the hole-opening nipple to ensure that no sparks or static electricity are generated during the cutting of the hole-opening tool; start the hole-opening device to perform hole-opening operations at the predetermined position of the ring sleeve body. There are two hole-opening channels, which are counterpoint holes, and the hole-opening diameter is 125 mm.

[0015] S4. Annular space cleaning and detection: Lower a 25-mm-diameter liquid suction pipe through one of the holes and fix it at 0.3 m inside the wellbore. Lower a 25-mm-diameter high-pressure cleaning pipe through the other hole. Lower a special pipeline with a flushing tool connected to the bottom to the original cement top surface of the oil-casing annulus, and flush the accumulated liquid and impurities out of the annular space; after cleaning, lower a detection device through the established channel. Lower an endoscope into the annular space, re-verify the depth of the annular space cement top surface, and observe whether the corrosion conditions of the outer wall of the oil layer casing and the surface casing meet the cementing operation conditions.

[0016] S5. Flushing and cementing: Lower a liquid suction pipe through one of the holes. The liquid suction pipe is lowered to a depth of 0.3 m and fixed. Lower a 25-mm-diameter high-pressure special pipeline through the other hole on the opposite side. The front end of the pipeline is connected to a spraying device and lowered to the design depth; prepare a plugging and reinforcement material according to the formula and design requirements, start a special integrated device to inject the material for reinforcement operations, and at the same time start the liquid suction pipe to suck out the replacement liquid. Observe the return flow at the outlet of the liquid suction pipe. Stop the pump after the cementing material returns to the outlet, lift out the pipeline, and remove the liquid suction pipe.

[0017] S6. Pressurized waiting for setting: Quickly install the sealing clamps on both sides of the hole, connect the high-pressure pipeline to the clamps, start the equipment, squeeze in the cementing material, stop the pump after the pump pressure rises to 2 MPa or leakage starts from the upper part of the annular steel plate, close the gate of the sealing clamp, remove the high-pressure pipeline, and wait for setting.

[0018] S7. Completing the well restoration: After waiting for setting is completed, remove the sealing clamp, clean the cementing material at the hole-opening position, and use the electric welding process to repair and weld the hole-opening position.

[0019] The advantages of the present invention compared with the prior art are as follows:

[0020] First, the risk is low: In the early stage, an injection channel is established through the non-fire under-pressure hole-opening process, without the need for fire operations, effectively eliminating risks such as fire, explosion, and personal injury.

[0021] Second, there is guarantee: Through the inspection and detection technology and the annular space flushing process technology, the accumulated liquid and impurities in the B annular space are thoroughly cleaned, and the corrosion conditions in the annular space are checked, minimizing the risk factors and improving the construction quality.

[0022] Third, the rectification is thorough: The new plugging material displacement process technology injects the configured new plugging material into the annular space by lowering a special pipeline into the B annulus and using a dedicated integrated device, filling the missing cement sheath in the B annular space, thus achieving the goal of treating potential hazards.

[0023] Fourth, the material has good performance: After being formulated, the cementing material has good permeability and compatibility; there are cracks and gaps in the original cement hard surface. During the injection process, the cementing material can fully contact the original cement hard surface and penetrate downward through the cracks and gaps, achieving a perfect bonding effect. Specific implementation mode

[0024] The present invention will be further described in detail below in conjunction with embodiments.

[0025] Embodiment

[0026] A method for plugging and strengthening the B annulus casing of oil and gas wells includes the following steps:

[0027] S1. Pressure test of the production casing: First, conduct a leak detection construction on the production casing above the oil layer to ensure that the production casing is not damaged. Use a pipe string combination of a plug Y521 packer and tubing to conduct a pressure test on the casing above the oil layer. The pressure is 15 Mpa, and it is kept stable for 30 minutes. If the pressure drop is less than or equal to 0.5 Mpa, the next step of construction can be continued. If the pressure test is unqualified, the casing leak point needs to be found, the casing above the leak point position is removed, the casing is connected back by threading, and then the next operation is carried out;

[0028] S2. Detection of casing integrity: Use an electromagnetic flaw detector to detect the production casing above the cement return height and evaluate the current quality status of the casing interior. If the casing is severely corroded, first perform casing replacement, and then carry out plugging and strengthening operations after replacing the casing;

[0029] S3. Pressure - assisted hole opening: Install a hole - opening clamp, connecting valve, and hole - opening equipment 200 mm below the annular steel plate seal iron; connect a nitrogen cylinder or a water pressure pump through a vent valve, inject a protective gas or liquid into the hole - opening nipple to ensure that no sparks and static electricity are generated during the cutting of the hole - opening tool; start the hole - opening equipment to perform hole - opening operations on the predetermined position of the casing body. There are two hole - opening channels, which are counter - positioned holes, and the hole - opening diameter is 125 mm;

[0030] S4. Annulus cleaning and detection: Lower a 25-mm diameter liquid suction pipe through one of the side holes and fix it at 0.3 m inside the wellbore. Lower a 25-mm diameter high-pressure cleaning pipe through the other side hole. Lower a special pipeline with a washing tool connected to the bottom to the original cement top surface in the casing annulus, and displace the accumulated liquid and impurities out of the annular space. After cleaning, lower the detection equipment through the established channel. Lower an endoscope into the annulus, re-verify the depth of the annulus cement top surface, and observe whether the corrosion conditions of the outer wall of the production casing and the surface casing meet the requirements for cementing operations.

[0031] S5. Displacement cementing: Lower a liquid suction pipe through one side hole. The liquid suction pipe is lowered to a depth of 0.3 m and fixed. Lower a 25-mm diameter high-pressure special pipeline through the other opposite side hole. The front end of the pipeline is connected to a jetting device and lowered to the designed depth. Prepare the plugging and reinforcement material according to the formula and design requirements, start the special integrated equipment to inject the material for reinforcement operations, and at the same time start the liquid suction pipe to suck out the replacement liquid. Observe the return flow at the outlet of the liquid suction pipe. Stop the pump after the cementing material returns to the outlet, lift out the pipeline, and remove the liquid suction pipe.

[0032] S6. Pressurized waiting for setting: Quickly install the sealing clamps on both side holes, connect the high-pressure pipeline to the clamps, start the equipment, squeeze in the cementing material, stop the pump after the pump pressure rises to 2 MPa or leakage starts above the annular steel plate, close the gate of the sealing clamp, remove the high-pressure pipeline, and wait for setting.

[0033] S7. Completing the well restoration: After waiting for setting is completed, remove the sealing clamp, clean the cementing material at the position of the wrench hole, and use the electric welding process to repair and weld the wrench hole position.

[0034] Experimental case 1: During the steam injection process in Well 1, the casing rose (≈0.4 m), and flash evaporation and spraying occurred in the accumulated liquid in the annulus at Wellhead B. After on-site surveying and mapping, the outer diameter of the surface casing of this well is 273 mm (casing wall thickness is 10 mm, inner diameter is 253 mm), the outer diameter of the production casing is 177.8 mm, and the outer diameter of the production casing collar is 195 mm. During the missing depth measurement, it was found that the missing depth of the cement sheath of this well is 41 m, including 15 m of sewage and dirty oil depth. According to the missing depth calculation, the cementing material consumption for this well = 3.14 × {[(253 / 2) 2 -(177.8 / 2) 2} × 41 / 1000000 = 1.043 m 3 . During on-site construction, the actual consumption of the cementing material was approximately 1.3 m 3 . It is inferred that this is caused by the downward penetration of the cementing material through the cracks and gaps in the original cement hard surface, proving that the cementing material is in full contact with the original cement sheath. After rectification and treatment, the hidden danger of this well was successfully solved. Currently, this well has resumed steam injection. After about 3 days of steam injection observation, the current steam injection volume is approximately 470 m 3The plugging and reinforcement effect of the annulus B at the wellhead is good, and phenomena such as flash evaporation and eruption of the liquid accumulation in annulus B and casing elevation do not occur again. After subsequent follow-up investigations, two rounds of gas injection measures have been carried out on this well, and the plugging and reinforcement effect is still intact.

[0035] Experimental Case 2: During the steam injection process of Well 2, flash evaporation and eruption of the liquid accumulation in annulus B occurred, causing pollution to the well site and surrounding waters. Through on-site measurement, the outer diameter of the surface casing of this well is 273 mm (casing wall thickness is 10 mm, inner diameter is 253 mm), the outer diameter of the production casing is 177.8 mm, and the outer diameter of the production casing collar is 200 mm. During the missing depth measurement, it was found that the missing depth of the cement sheath of this well is 35 m, including 30 m of sewage and dirty oil depth. According to the missing depth calculation, the amount of cementing material used in this well = 3.14 × {[(253 / 2) 2 -(177.8 / 2) 2} × 35 / 1000000 = 0.7 m 3 , during on-site construction, the usage of cementing material was approximately 1 m 3 . From this, it is inferred that the cementing material penetrated downward through the cracks and gaps in the original cement hard surface, proving that the cementing material is in full contact with the original cement sheath. After rectification and treatment, the hidden danger of this well was successfully solved. Currently, this well has resumed steam injection, and the steam injection volume is approximately 2500 m 3 . After observation, the plugging and reinforcement effect is good, and phenomena such as flash evaporation and eruption and casing elevation do not occur again.

[0036] The above describes the present invention and its implementation manners. Such description is not restrictive. What is shown in the embodiments is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments without creative efforts without departing from the purpose of the present invention's creation, they shall fall within the protection scope of the present invention.

Claims

1. Method for plugging and strengthening the B annulus casing of oil and gas wells, Characterized in that, It includes the following steps: S1. Pressure test of production casing: First, conduct a leak detection construction on the production casing above the oil layer to ensure that the production casing has no physical damage. Use a pipe string combination of a plug Y521 packer and tubing to conduct a pressure test on the casing above the oil layer. The pressure is 15 Mpa, and it is kept stable for 30 minutes. If the pressure drop is less than or equal to 0.5 Mpa, the next step of construction can be continued. If the pressure test is unqualified, the casing leak point needs to be found, the casing above the leak point position is removed, the well is connected back by threading, and then the next operation is carried out; S2. Detection of casing integrity: Use an electromagnetic flaw detector to detect the production casing above the cement return height, and evaluate the current quality status of the casing interior. If the casing is severely corroded, first implement casing replacement, and then carry out plugging and strengthening operations after replacing the casing; S3. Pressure - assisted hole opening: Install a hole - opening clamp, a connecting valve, and a hole - opening device 200 mm below the annular steel plate seal iron; connect a nitrogen cylinder or a water pressure pump through a vent valve, and inject a protective gas or liquid into the hole - opening nipple to ensure that no sparks and static electricity are generated when the hole - opening tool cuts; Start the hole - opening device to carry out hole - opening operations at the predetermined position of the casing body. There are two hole - opening channels, which are counter - positioned holes, and the hole - opening diameter is 125 mm; S4. Annulus cleaning and detection: Lower a 25 - mm diameter liquid - suction pipe through one of the holes and fix it at 0.3 m inside the wellbore. Lower a 25 - mm diameter high - pressure cleaning pipe through the other hole. Lower a special pipeline with a washing tool connected to the bottom to the original cement top surface of the oil - casing annulus, and flush out the accumulated liquid and impurities from the annular space; after cleaning, lower a detection device through the established channel. Lower an endoscope into the annulus, re - verify the depth of the annulus cement top surface, and observe whether the corrosion conditions of the outer wall of the production casing and the surface casing meet the conditions for cementing operations; S5. Displacement cementing: Lower a liquid - suction pipe through one of the holes, and the liquid - suction pipe is lowered to a depth of 0.3 m and fixed. Lower a 25 - mm diameter high - pressure special pipeline through the other opposite hole. The front end of the pipeline is connected to a spraying device and lowered to the designed depth; prepare the plugging and strengthening material according to the formula and design requirements, start the special integrated equipment to inject the material for strengthening operations, and at the same time start the liquid - suction pipe to suck out the replacement liquid. Observe the return material at the outlet of the liquid - suction pipe. Stop the pump after the cementing material returns to the outlet, pull out the pipeline, and remove the liquid - suction pipe; S6. Pressurized waiting for setting: Quickly install the sealing clamps on both sides of the holes, connect the high - pressure pipeline to the clamps, start the equipment, squeeze in the cementing material, stop the pump after the pump pressure rises to 2 MPa or the upper part of the annular steel plate starts to leak, close the gate of the sealing clamp, remove the high - pressure pipeline, and wait for setting; S7. Well completion restoration: After waiting for setting, remove the sealing clamp, clean the cementing material at the hole - opening position, and use the electric welding process to repair and weld the hole - opening position.