Method for preventing corrosion in whole-well-section casing pipe of producing well

Abstract

The invention discloses an anti-corrosion method in a full-well-section casing pipe of a producing well, and belongs to the technical field of oil exploitation anti-corrosion. According to the method, the perforation section serves as the boundary, the whole shaft is divided into the first section from a well mouth to a floral tube and the second section from the floral tube to an artificial well bottom, the pump depth is not changed, the floral tube is deepened to the position 50 m above the perforation section, a liquid inlet of output liquid moves downwards, the output liquid directly enters the floral tube after coming out of the perforation section and is conveyed to the ground through an oil pipe, and meanwhile the output liquid is conveyed to the ground through the oil pipe. Fluid from a floral tube to a wellhead oil sleeve annulus is relatively static, and oil-water separation occurs under the action of gravity, so that oil above the floral tube is pure oil, and corrosion of the sleeve is slowed down; then, solid slow-release particles are fed through an oil sleeve annulus, and corrosion from the artificial well bottom to a floral tube is slowed down; the method is simple and feasible in construction process and high in operability, and has a certain promotion effect on popularization and application of the technology.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production anti-corrosion, and in particular relates to an anti-corrosion method for the entire casing of an oil production well. Background Art

[0002] With the continuous development of oil fields, casing damage in oil and water wells has become a technical bottleneck problem, especially in western oil fields, where internal and external corrosion perforation of casing is the main problem. Casing damage affects the perfection of oil and water well networks and causes safety and environmental protection problems. With the new requirements for safety and environmental protection in recent years and the dual pressure of stable production in old oil fields, it is urgent to explore an effective anti-corrosion process. At present, the commonly used anti-corrosion methods for old wells mainly include cathodic protection technology of sacrificial anodes and corrosion protection by adding corrosion inhibitors. However, sacrificial anode technology is easily affected by the wall contact structure brought into the anode, which can easily cause downhole tools to get stuck, causing inconvenience to later operations. The main problems of adding corrosion inhibitors are high filling frequency and high labor intensity of on-site filling. In addition, as the oil pump works, some agents are pumped out of the wellbore, resulting in poor anti-corrosion effect. Existing anti-corrosion technologies also have the following problems: 1) The protection distance of the anode short section is short, the consumption is fast, and it is easy to cause drilling jams and overhauls; 2) The conventional dosing cycle is short and the labor intensity of personnel is high.

[0003] like Figure 1 As shown in the figure, the traditional oil well pump needs to be lowered to a depth of 1300 to 1500 m, the flower pipe is 20 to 50 m below the oil well pump, and the flower pipe is between 400 and 600 m away from the perforation section. The wellbore from the flower pipe to the perforation section is the produced fluid. The water content of the produced fluid continues to increase with the development of the oil field. In the water environment, carbon dioxide is easily corroded by the casing after dissolving in water, causing great damage to the casing. In severe cases, the casing is corroded and perforated. There is currently no effective anti-corrosion measure. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for corrosion protection inside the casing of an oil well in the entire well section, so as to solve the technical problems that the existing corrosion protection means are difficult to achieve corrosion protection in the entire well section, the construction process is complicated and the corrosion protection effect is poor.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The invention discloses a method for preventing corrosion in casing of a whole well section of an oil production well, comprising the following steps:

[0007] S1: The entire wellbore is divided into Section I and Section II from the wellhead (1) to the artificial well bottom (3) with the perforation section as the boundary; Section I is from the wellhead (1) to the flower pipe (2), and Section II is from the flower pipe (2) to the artificial well bottom (3); the length of the flower pipe (2) in Section I is extended to 50m above the perforation section (4), so that the fluid in the annulus of the oil pipe (5) and the casing (6) from the flower pipe (2) to the wellhead (1) is relatively static, and at the same time, the fluid is separated from oil and water under the action of gravity;

[0008] S2: Solid slow-release particles are added through the oil casing annulus through airdrop, and the solid slow-release particles settle into the second section to achieve corrosion protection.

[0009] Furthermore, in S1, the first section of the tubular column assembly from bottom to top comprises a mother plug (7), a plurality of tail pipes, a flower pipe (2) and an oil pipe (5) arranged in sequence; and an oil pump (8) is connected between the flower pipe (2) and the oil pipe (5).

[0010] Furthermore, in S2, the components of the solid slow-release particles include, by mass percentage, 40% of imidazoline corrosion inhibitor, 5% of inorganic skeleton material, 35% of surfactant mixture, 2% of weighting agent and 18% of polymer wrapping material.

[0011] Furthermore, in S2, the density of the solid sustained-release particles is 1.05 to 1.10 g / cm 3 .

[0012] Furthermore, in S2, the solid slow-release particles are added once every quarter.

[0013] Furthermore, the weight of the solid slow-release particles added each time is 150-200 kg.

[0014] Further, in S2, the step of air dropping solid slow-release particles through the oil casing annulus is:

[0015] Step 1: Use wellbore preparation: Check the casing annulus valve to confirm that the switch is normal and the annulus is unobstructed, open the casing valve, confirm that the annulus pressure drops to zero, and prepare to add solid corrosion inhibition particles from the annulus;

[0016] Step 2: Adding chemicals: Pour 10kg of solid corrosion-inhibiting particles, then add 100kg of water to flush the solid corrosion-inhibiting particles into the annulus of the oil casing, and repeat this operation until all the solid corrosion-inhibiting particles that need to be added each time are injected into the annulus of the oil casing; after all the solid corrosion-inhibiting particles are injected, inject 100kg of aqueous solution;

[0017] Step 3: Well shutdown requirements: After completing step 2, shut down the well to ensure that the solid corrosion inhibition particles settle to section II.

[0018] Furthermore, in step 2, the aqueous solution contains a scale inhibitor, and the concentration of the scale inhibitor in the aqueous solution is 100 ppm.

[0019] Furthermore, in step 3, the well is shut down for at least 4 to 6 hours.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention discloses an anti-corrosion method for the casing of an oil production well in the whole well section. The whole wellbore is divided into two sections, namely, section I and section II, with the perforation section as the boundary. Section I is from the wellhead to the flower pipe, and section II is from the flower pipe to the bottom of an artificial well. By adopting the method of keeping the pump depth unchanged and deepening the flower pipe to 50m above the perforation section, the liquid inlet of the produced fluid is moved downward, and the produced fluid directly enters the flower pipe after coming out of the perforation section and is transmitted to the ground through the oil pipe. At the same time, the fluid in the oil casing annulus from the flower pipe to the wellhead is relatively still, and oil and water are separated under the action of gravity, so that the area above the flower pipe is pure oil, thereby slowing down the corrosion of the casing. Subsequently, solid slow-release particles are dropped into the oil casing annulus to slow down the flow from the bottom of the artificial well to the bottom of the artificial well. The invention discloses a method for preventing corrosion of the flower pipe; the method utilizes the elongation of the flower pipe to change the oil-water differentiation in the wellbore, thereby protecting the wellhead to the flower pipe; solid slow-release particles are added through the oil casing annulus, and the solid slow-release particles slowly settle to the bottom of the artificial well, and the corrosion inhibitor slowly dissolves and releases after contacting the wellbore fluid, thereby protecting the flower pipe to the bottom of the artificial well and realizing corrosion protection of the entire well section; the method reduces the labor intensity of manual labor compared with the conventional corrosion protection by adding corrosion inhibitors, especially reduces the risk of adding corrosion inhibitors to wells with high hydrogen sulfide content; compared with the sacrificial anode corrosion protection, the consumption cost of anode tools and the supporting process of drilling and lowering are reduced, the construction process is simple and easy, and the operability is strong, which has a certain promoting effect on the popularization and application of the technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram before the flower tube is deepened;

[0023] Figure 2 This is a schematic diagram of the flower tube after deepening;

[0024] Among them: 1-wellhead; 2-flowered pipe; 3-artificial well bottom; 4-perforation section; 5-oil pipe; 6-casing; 7-mother plug; 8-oil pump;

[0025] Figure 3 To deepen the water content profile of the wellbore before the flower pipe;

[0026] Figure 4 This is the water content profile of the wellbore after deepening the flower pipe. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0029] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0031] The invention discloses a method for anti-corrosion in casing of the whole well section of an oil production well. The whole wellbore is divided into two sections, the first section is from a wellhead 1 to a flower pipe 2, and the second section is from the flower pipe 2 to an artificial well bottom 3.

[0032] In the first section: keep the pumping depth of the oil pump 8 unchanged, deepen the flower pipe 2 to 50m above the perforation section, move the liquid inlet downward, and the produced liquid directly enters the flower pipe 2 after coming out of the perforation section, and is transmitted to the ground through the oil pipe 5; make the fluid in the annulus between the flower pipe 2 and the wellhead relatively static, and under the action of gravity, oil and water are separated, so that the area above the flower pipe 2 is pure oil, which slows down the corrosion of the casing.

[0033] In the second stage: solid slow-release particles are added through the oil casing annulus. The density of solid slow-release particles is 1.05-1.10 g / cm 3 After being added from the casing, it slowly sinks to the bottom of the artificial well (reaching the second section). After contacting with the wellbore fluid, the corrosion-inhibiting particles slowly dissolve and release, slowing down the corrosion from the bottom of the artificial well to the flower pipe.

[0034] Compared with conventional anti-corrosion technology, this anti-corrosion process has the advantages of full-well section anti-corrosion, long anti-corrosion cycle and low maintenance cost.

[0035] Preferably, the present invention also discloses a standard combination of deepening the tubing column, a standard for daily addition of solid slow-release particles, and a maintenance plan:

[0036] 1) Deepen parameters:

[0037] The tubing string combination from bottom to top in Section I is: mother plug + 3 tail pipes + flower pipe (down to 50m above the perforation section) + oil pipe + oil pump + oil pipe to the wellhead; deepen the flower pipe 2 to 50m above the perforation section.

[0038] 2) Daily dosing requirements for solid slow-release particles:

[0039] Dosage cycle: once every quarter, dosage 150-200kg, adjusted appropriately according to the volume of the wellbore pocket.

[0040] Dosing method:

[0041] Wellbore preparation: Before filling the normal production well, check the casing annulus valve to confirm that the switch is normal and the annulus is unobstructed; open the casing valve and wait for more than 10 minutes to confirm that the annulus pressure drops to zero and that the conditions for personnel to operate safely are met; use a funnel to add solid corrosion-inhibiting particles from the annulus (prepare the annulus gate removal tool);

[0042] Adding chemicals: Pour about 10kg of solid corrosion inhibition particles manually, and then add 0.1m 3 (100kg) of clean water will flush the reagent into the annulus of the casing and oil well. Repeat this operation until all the reagents that need to be added each time are injected into the annulus of the casing and oil well. After filling a single well, continue to pump for 1m 3 Clean water; add antiscalant (concentration 100ppm) to the clean water; if there is gas capping, suspend the operation and continue adding the agent after the gas escapes;

[0043] Well shutdown requirements: After filling is completed, the well should be shut down for at least 4 to 6 hours without human intervention during this period to ensure that the solid corrosion-inhibiting particles can freely settle to the pocket at the bottom of the well.

[0044] Wherein, according to mass percentage, the components of the solid slow-release particles include 40% of imidazoline corrosion inhibitor, 5% of inorganic skeleton material, 35% of surfactant mixture, 2% of weighting agent and 18% of polymer wrapping material.

[0045] 3) Maintenance plan:

[0046] Wellbore matching: Wells with slight scaling can be completed with double flower pipes, and wells with severe scaling can be completed with large-aperture low-density flower pipes to prevent scaling from clogging the flower pipes and ensure smooth liquid flow into the wellbore.

[0047] Maintenance requirements: During the later maintenance work of deepening the well, all tail pipes must be pulled out (it is strictly forbidden to only pull them up to the pump depth position), and the tail pipe scaling wells must be strictly cleaned and flushed to monitor the corrosion of the tail pipe; the sand settling pipe at the lower end of the flower pipe 2 must be cleaned to reduce the blockage of the tail pipe; when going down the well again, the deepened tail pipe under the oil pump 8 must be pressure tested, and it is strictly forbidden to deepen the tail pipe with perforation.

[0048] After deepening the floral pipe using the method disclosed in the present invention, the test results of the water content profile of the casing annulus are as follows: Figure 4 As shown, Figure 3 From the comparison of the test results of the water content profile of the oil casing annulus without deepening the floral pipe, it can be seen that after deepening the floral pipe using the method disclosed in the present invention, the water content above the floral pipe is less than 10%, forming a low-water environment, which can reduce the corrosion rate of the casing, has excellent anti-corrosion effect, and can effectively achieve corrosion protection for the entire well section.

[0049] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for anti-corrosion of the casing of an oil well in the entire well section, characterized in that: The following steps are involved: S1: The entire wellbore is divided into Section I and Section II from the wellhead (1) to the artificial well bottom (3) with the perforation section as the boundary; Section I is from the wellhead (1) to the flower pipe (2), and Section II is from the flower pipe (2) to the artificial well bottom (3); the length of the flower pipe (2) in Section I is extended to 50m above the perforation section (4), so that the fluid in the annulus of the oil pipe (5) and the casing (6) from the flower pipe (2) to the wellhead (1) is relatively static, and at the same time, the fluid is separated from oil and water under the action of gravity; S2: Solid slow-release particles are added through the oil casing annulus through airdrop, and the solid slow-release particles settle into the second section to achieve corrosion protection.

2. The method for anti-corrosion of the casing of an oil well in the whole well section according to claim 1, characterized in that: In S1, the first section of the tubular column assembly from bottom to top comprises a mother plug (7), a plurality of tail pipes, a flower pipe (2) and an oil pipe (5) which are arranged in sequence; an oil pump (8) is connected between the flower pipe (2) and the oil pipe (5).

3. The method for anti-corrosion of the casing of an oil well in the whole well section according to claim 2, characterized in that: The number of the tail pipes is three.

4. The method for anti-corrosion of the casing of an oil well in the whole well section according to claim 1, characterized in that: In S2, the components of the solid slow-release particles include, by mass percentage, 40% of imidazoline corrosion inhibitor, 5% of inorganic skeleton material, 35% of surfactant mixture, 2% of weighting agent and 18% of polymer wrapping material.

5. The method for anti-corrosion of the casing of an oil well in the whole well section according to claim 1, characterized in that: In S2, the density of the solid sustained-release particles is 1.05-1.10 g / cm 3 .

6. The method for anti-corrosion of the casing of an oil well in the whole well section according to claim 1, characterized in that: In S2, the solid slow-release particles are added once every quarter.

7. The method for anti-corrosion in casing of an oil well according to claim 6, characterized in that: The weight of solid slow-release particles added each time is 150-200 kg.

8. The method for anti-corrosion in casing of an oil well according to claim 1, characterized in that: In S2, the steps of adding solid slow-release particles through the oil casing annulus are: Step 1: Use wellbore preparation: Check the casing annulus valve to confirm that the switch is normal and the annulus is unobstructed, open the casing valve, confirm that the annulus pressure drops to zero, and prepare to add solid corrosion inhibition particles from the annulus; Step 2: Adding chemicals: Pour 10kg of solid corrosion-inhibiting particles, then add 100kg of water to flush the solid corrosion-inhibiting particles into the annulus of the oil casing, and repeat this operation until all the solid corrosion-inhibiting particles that need to be added each time are injected into the annulus of the oil casing; after all the solid corrosion-inhibiting particles are injected, inject 100kg of aqueous solution; Step 3: Well shutdown requirements: After completing step 2, shut down the well to ensure that the solid corrosion inhibition particles settle to section II.

9. The method for anti-corrosion in casing of an oil well according to claim 8, characterized in that: In step 2, the aqueous solution contains a scale inhibitor, and the concentration of the scale inhibitor in the aqueous solution is 100 ppm.

10. The method for anti-corrosion in casing of an oil well according to claim 8, characterized in that: In step 3, the well is shut down for at least 4 to 6 hours.

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