A comprehensive diagnosis method for tubing corrosion perforation

Abstract

The present application relates to the technical field of oil and gas well production, and particularly relates to a comprehensive diagnosis method for tubing corrosion perforation, which comprises the following steps: step one: differential pressure monitoring, judging whether perforation or fracture of the tubing is possible; step two: gas lift verification: injecting gas source from the pump into the annulus between the oil casing to determine whether perforation or fracture of the tubing occurs; step three: lowering a gamma magnetic positioning instrument into the wellbore to detect the coupling signal of the tubing string, judging whether perforation or fracture of the tubing occurs; step four: measuring the inner diameter of the tubing, obtaining the number and distribution position of the perforations by an electromagnetic flaw detector; and step five: formulating a fishing treatment scheme. The advantages of various detection schemes are integrated, the rapid and accurate acquisition of diagnosis results is realized, the decision basis for tubing treatment is provided, compared with single experience judgment, the diagnosis process avoids the defects of low judgment efficiency and inaccurate judgment results caused by experience errors, also avoids the resource waste caused by directly using instrument flaw detection, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well production technology, and in particular to a comprehensive diagnostic method for corrosion perforation of shale gas well tubing. Background Technology

[0002] During the tubing production stage of shale gas wells, bacteria growing in the backflushing fluid will continuously corrode the tubing, and fracturing sand will also continuously erode the tubing, causing some shale gas well tubing to be corroded and perforated, or even ruptured. If the corrosion and perforation are not detected and treated in time, it will seriously harm the gas well production and affect the normal production of the gas well.

[0003] Currently, corrosion perforation of shale gas well tubing is generally determined through long-term monitoring of wellhead pressure changes, using experience or data calculations. However, this method cannot directly assess the degree of corrosion, the number of perforations, and the distribution of holes, leading to an inability to quickly and accurately diagnose the corrosion perforation of shale gas tubing. This hinders the timely implementation of remedial measures and impacts the normal production of the gas well.

[0004] Therefore, there is an urgent need for a technical solution to address the problem that the specific circumstances of corrosion and perforation in existing shale gas and oil pipelines cannot be diagnosed and known in a timely manner, thus affecting the normal production of gas wells. Summary of the Invention

[0005] The purpose of this invention is to provide a comprehensive diagnostic method for shale gas pipeline corrosion perforation, addressing the technical problem that the specific details of corrosion perforation in existing shale gas pipelines cannot be diagnosed in a timely manner, thus affecting the normal production of gas wells.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A comprehensive diagnostic method for tubing corrosion and perforation includes the following steps: Step 1: Differential pressure monitoring: Real-time monitoring of the oil pressure and casing pressure difference. If the difference decreases instantaneously, it is determined that the tubing may have perforated or broken, proceeding to Step 2; Step 2: Gas lift verification: Gas is injected from the annulus of the tubing and casing using a pump. The pump pressure, tubing pressure, and annulus fluid level are monitored in real time. The theoretical pump pressure is calculated based on the annulus fluid level when the tubing is pressurized. If the pump pressure when the tubing is pressurized is lower than the theoretical pump pressure, it is determined that the tubing has perforated or broken, proceeding to Step 3; Step 3: Magnetic positioning verification: A gamma magnetic positioning instrument is inserted into the wellbore to detect the joint signal of the tubing string. The change in the joint signal determines whether the tubing has broken or perforated. If it is broken, proceed to Step 5; if it is perforated, proceed to Step 4; Step 4: Perforation distribution determination: The inner diameter of the tubing is measured, and the wall thickness loss of the tubing is determined using an electromagnetic flaw detector to obtain the number and distribution of perforations; Step 5: Develop a salvage and remediation plan.

[0008] This invention provides a comprehensive diagnostic method for oil pipe corrosion perforation. After initial judgment through differential pressure monitoring, it integrates the results of various detection schemes, including air lift verification, magnetic positioning verification, and electromagnetic flaw detection, to achieve rapid and accurate acquisition of diagnostic results. This provides a more scientific and reasonable decision-making basis for oil pipe management. Compared with judgment based on single experience, the diagnostic process avoids the defects of low judgment efficiency and inaccurate judgment results caused by experience errors, and also avoids the waste of resources caused by directly using instrument flaw detection. It has broad application prospects.

[0009] In a preferred embodiment of the present invention, nitrogen is injected into the annulus of the oil jacket by means of an air lift vehicle in step two.

[0010] As a preferred embodiment of the present invention, in step two, the difference between the pump pressure value of the pump when the tubing is pressurized and the theoretical pump pressure value is inversely correlated with the distance between the perforation or fracture location and the wellhead.

[0011] As a preferred embodiment of the present invention, in step two, the interval between pump start-up and tubing pressurization is monitored synchronously, and the length of the interval is positively correlated with the distance between the perforation or fracture location and the wellhead.

[0012] As a preferred embodiment of the present invention, in step three, if the clamp signal weakens and the interval distance of the clamp signal matches the length of a single casing, it is determined that the tubing has broken; if the clamp signal is regular and consistent, it is determined that the tubing has perforated.

[0013] As a preferred embodiment of the present invention, in step one, monitoring curves of oil pressure, casing pressure and oil-casing pressure difference are obtained respectively. In step two, monitoring curves of pump pressure value, gas pressure value in oil pipe and annular liquid level position are obtained respectively, and timing is performed simultaneously. Based on the fluctuation of the monitoring curves, the computer prompts the judgment result.

[0014] As a preferred embodiment of the present invention, in step five, if the oil pipe is broken, the salvage and treatment plan includes the fish top shape acquisition step and the salvage step; if the oil pipe is perforated, the salvage and treatment plan includes the hole sealing step and the oil pipe lifting step.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0016] This invention provides a comprehensive diagnostic method for oil pipe corrosion perforation. After initial judgment through differential pressure monitoring, it combines the detection processes of air lift verification, magnetic positioning verification, and electromagnetic flaw detection. By integrating the advantages of each detection scheme, it achieves rapid and accurate acquisition of diagnostic results, providing a basis for decision-making in oil pipe management. Compared with judgment based on single experience, the diagnostic process avoids the defects of low judgment efficiency and inaccurate judgment results caused by experience errors, and also avoids the waste of resources caused by directly using instrument flaw detection. It has broad application prospects. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a comprehensive diagnostic method for oil pipe corrosion perforation according to the present invention.

[0018] Figure 2 This is a monitoring curve of oil pressure, casing pressure, and daily gas and water production of a well in Example 2. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings.

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Example 1

[0022] like Figure 1 As shown, a comprehensive diagnostic method for oil pipe corrosion perforation includes the following steps: Step 1: Differential pressure monitoring: Real-time monitoring of the oil pressure and casing pressure difference. If the difference decreases instantaneously, it is determined that the oil pipe may have perforated or broken, and then proceed to Step 2.

[0023] Specifically, in step one, the monitoring curves of oil pressure, casing pressure, and oil-casing pressure difference are obtained respectively. If the oil pressure and casing pressure difference values ​​decrease instantaneously and then level off, it can be preliminarily judged that there is an abnormality in the gas well tubing. However, it cannot be clearly determined whether a perforation or rupture has actually occurred.

[0024] Step 2: Air Lift Verification: Inject air into the annulus of the oil casing using a pump, and monitor the pump pressure, the air pressure in the tubing, and the annulus liquid level in real time. Calculate the theoretical pump pressure based on the annulus liquid level when the tubing is pressurized. If the pump pressure when the tubing is pressurized is lower than the theoretical pump pressure, it is determined that the tubing has perforated or broken, and proceed to Step 3.

[0025] Specifically, based on step one, the air lift operation is used to verify whether the tubing has indeed been perforated or broken, in order to rule out pressure differential changes caused by other factors. During the operation, monitoring curves of pump pressure, tubing pressure, and annular fluid level are acquired. Based on the fluctuation of the monitoring curves, the computer provides the judgment result. In particular, after real-time measurement and monitoring of the annular fluid level, nitrogen is injected from the annulus of the casing and output from the tubing through the air lift vehicle, and timing is performed simultaneously. The pump pressure and tubing pressure are monitored in real time by the monitoring instruments of the computer. The pump pressure when the tubing is pressurized and the time interval from pump start to tubing pressurization are acquired. The theoretical pump pressure is calculated based on the annular fluid level when the tubing is pressurized. The theoretical pump pressure is compared with the actual pump pressure. If the actual pump pressure is lower than the theoretical pump pressure, it is determined that the tubing has been perforated or broken. However, whether the tubing has been perforated or broken cannot be clearly determined, and step three is required.

[0026] Specifically, the difference between the pump pressure value during tubing pressurization and the theoretical pump pressure value is inversely correlated with the distance between the perforation or fracture location and the wellhead. That is, the greater the difference between the pump pressure value during tubing pressurization and the theoretical pump pressure value, the closer the perforation or fracture location is to the wellhead.

[0027] Specifically, the interval between pump start-up and tubing pressurization is positively correlated with the distance between the perforation or fracture location and the wellhead. That is, the shorter the time interval, the closer the perforation or fracture location is to the wellhead.

[0028] Specifically, if 3.44*(H-Ha) < H, then the theoretical pump pressure is: 3.44*(H-Ha)ρg*0.01; if 3.44*(H-Ha) ≥ H, then the theoretical pump pressure is: ρgH*0.01, where H is the bottom depth of the tubing in meters; Ha is the annular fluid level depth in meters; ρ is the well fluid density in cubic meters per gram (m³ / g); and g is the acceleration due to gravity.

[0029] Specifically, taking a certain well as an example, the well depth is 3900m and the measured annular fluid level is 2500m. Under the condition that the tubing is not perforated or broken, it is necessary to lift the well through with an pressure of 28MPa and an interval of at least 5 hours. However, when the second step of the operation was actually carried out, the well was lifted through at 12MPa in less than 1 minute, and it was determined that the tubing was perforated or broken.

[0030] Step 3: Magnetic positioning verification: By inserting a gamma magnetic positioning instrument into the wellbore, the joint signal of the tubing string is detected. The change in the joint signal determines whether the tubing has broken or perforated. If it is broken, proceed to step 5; if it is perforated, proceed to step 4.

[0031] Specifically, based on step two, the magnetic positioning instrument is used to determine whether the tubing has been perforated or broken, providing a basis for subsequent treatment plans. During operation, the gamma magnetic positioning instrument is lowered into the wellbore through wireline work to obtain the tubing string clamp signal. By observing the clamp signal of the tubing string, if the clamp signal weakens and the interval distance of the clamp signal matches the length of a single casing, it is determined that the tubing has broken; if the clamp signal is regular and consistent, it is determined that the tubing has been perforated. However, the location and number of tubing perforations cannot be determined clearly yet, and step four is required.

[0032] Step 4: Determine the distribution of the perforations: Measure the inner diameter of the oil pipe, determine the wall thickness loss of the oil pipe using an electromagnetic flaw detector, and obtain the number and distribution of the perforations.

[0033] Specifically, based on step three, after determining that the tubing has been perforated, a multi-arm caliper electromagnetic flaw detector is lowered into the wellbore via cable to measure the inner diameter of the tubing and determine the amount of tubing wall thickness loss. By combining the two measurements, the distribution and number of perforations are determined, and the degree of corrosion on the inner wall of the tubing is obtained, providing a basis for the formulation of a remediation plan.

[0034] Step 5: Develop a salvage and remediation plan.

[0035] Specifically, in step five, if the oil pipe breaks, the salvage and treatment plan includes obtaining the fish-top shape and salvage; if the oil pipe is perforated, the salvage and treatment plan includes sealing the hole and pulling up the oil pipe.

[0036] This embodiment presents a comprehensive diagnostic method for oil pipe corrosion perforation. After initial judgment through differential pressure monitoring, it combines the detection processes of air lift verification, magnetic positioning verification, and electromagnetic flaw detection. By integrating the advantages of each detection scheme, it achieves rapid and accurate acquisition of diagnostic results, providing a basis for decision-making in oil pipe management. Compared with judgment based on single experience, the diagnostic process avoids the defects of low judgment efficiency and inaccurate judgment results caused by experience errors, and also avoids the waste of resources caused by directly using instrument flaw detection. It has broad application prospects.

[0037] Example 2

[0038] To further clarify this solution, this embodiment uses the diagnostic process of a specific gas well as an example for illustration. Figure 2 The figure shown is a monitoring curve of oil pressure, casing pressure, and daily gas and water production of a certain well. Figure 2 It can be seen that the production of a certain well dropped abnormally in May 2021. In less than a month, the oil-casing pressure difference dropped from 5.5 MPa to 0.7 MPa. At the same time, the gas production and water production also decreased. If it was caused by fluid accumulation in the wellbore, the oil-casing pressure difference should have been increasing. Therefore, it can be preliminarily judged that the gas well tubing has perforated or broken.

[0039] Furthermore, a membrane-based nitrogen lift truck was used on-site to pressurize the annulus of the tubing and casing to 12 MPa. After monitoring the pressure and recording the time during the gas lift process, the tubing pressure rose from 8.9 MPa to 12 MPa within 1 minute, indicating that the tubing and casing were connected, and the connection point was close to the wellhead, indicating that the tubing had indeed perforated or broken.

[0040] Furthermore, on-site, a natural gamma and magnetic positioning instrument were lowered using wire rope to measure the entire length of the oil pipe. The oil pipe clamp signal was normal, indicating that the oil pipe was not broken, and it was determined that the oil pipe had been perforated.

[0041] Furthermore, after confirming the tubing perforation, it is necessary to determine the distribution of the perforations. If there are few perforations, a tubing plug can be used to seal them, and the tubing can be pulled out under pressure for replacement. If there are many perforations that are concentrated and long, the well must be killed before the tubing can be replaced. Therefore, the wellbore was inspected on-site using a cable-driven multi-arm caliper and an electromagnetic flaw detector. The results showed that the 0-611m tubing had varying degrees of corrosion and perforation. Due to the long perforation span, it was not possible to use a tubing plug to seal it. Therefore, it was decided to kill the well with clean water and then use a workover rig to replace the tubing. In August 2021, the perforated and corroded tubing from 0 to 1500m was replaced with internally coated anti-corrosion tubing using a workover rig. After the replacement, the gas production increased from 21,000 cubic meters / day to 28,000 cubic meters / day, and the casing pressure increased from 5.9 MPa to 7 MPa, improving the stable production capacity of the gas well.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A comprehensive diagnostic method for oil pipe corrosion perforation, characterized in that, Includes the following steps: Step 1: Differential Pressure Monitoring: Monitor the oil pressure and casing pressure difference in real time. If the difference decreases instantaneously, it is determined that the oil pipe may have perforated or broken, and proceed to Step 2. Step 2: Air lift verification: Inject air from the annulus of the oil jacket using a pump, and monitor the pump pressure, the air pressure in the tubing, and the annulus liquid level in real time. Calculate the theoretical pump pressure based on the annulus liquid level when the tubing is pressurized. If the pump pressure when the tubing is pressurized is lower than the theoretical pump pressure, it is determined that the tubing has perforated or broken, and proceed to Step 3. Step 3: Magnetic positioning verification: By inserting a gamma magnetic positioning instrument into the wellbore, the joint signal of the tubing string is detected. Based on the change of the joint signal, it is determined whether the tubing has broken or perforated. If it is broken, proceed to step 5; if it is perforated, proceed to step 4. Step 4: Determine the distribution of the perforations: Measure the inner diameter of the oil pipe, determine the wall thickness loss of the oil pipe using an electromagnetic flaw detector, and obtain the number and distribution location of the perforations; Step 5: Develop a salvage and remediation plan; In step two, nitrogen is injected into the annulus of the oil jacket using an air lift vehicle; In step two, the difference between the pump pressure value of the pump when the tubing is pressurized and the theoretical pump pressure value is inversely correlated with the distance between the perforation or fracture location and the wellhead; In step two, the interval between pump start-up and tubing pressurization is monitored synchronously. The length of the interval is positively correlated with the distance between the perforation or fracture location and the wellhead. In step three, if the clamp signal weakens and the interval between clamp signals matches the length of a single casing, it is determined that the tubing has broken; if the clamp signal is regular and consistent, it is determined that the tubing has perforated. In step one, the monitoring curves of oil pressure, casing pressure and oil-casing pressure difference are obtained respectively. In step two, the monitoring curves of pump pressure, gas pressure in oil pipe and annular liquid level are obtained respectively, and the timing is synchronized. The computer prompts the judgment result based on the fluctuation of the monitoring curve. In step five, if the oil pipe breaks, the salvage and treatment plan includes obtaining the fish top shape and the salvage step; if the oil pipe is perforated, the salvage and treatment plan includes sealing the hole and pulling up the oil pipe.

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