A method and system for locating and detecting a wellbore cement ring leakage channel

Abstract

The present application relates to a method and system for locating and detecting a wellbore cement ring leakage channel, the method comprising the following steps: preliminarily judging whether the casing annulus and the oil-casing annulus are connected according to the pressure states of the casing annulus and the oil-casing annulus; the casing annulus is the area between the casing and the formation, which is filled with cement ring; the oil-casing annulus is the area between the oil pipe string and the casing, which is filled with annulus liquid and annulus gas; if so, collecting the blowout fluids of the oil-casing annulus and the casing annulus, and continuing to locate and identify the leakage channel at a specific starting position of the oil-casing annulus according to the components of the blowout fluids of the casing annulus and the blowout fluids of the oil-casing annulus; if not, it means that the source of the leakage is not the oil-casing annulus, and locating and identifying the starting position of the leakage channel according to the components of the blowout fluids of the casing annulus. The method of the present application can reduce the operation time and workload as much as possible in the detection and identification of cement ring leakage channels, and improve the reliability of detection.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas wellbore detection, and in particular to a method and system for locating and detecting a wellbore cement ring leakage channel. Background Art

[0002] Underground oil and gas resources are an important part of energy supply. At the same time, underground storage of hydrogen, compressed air, natural gas, and carbon dioxide has become one of the best ways to efficiently utilize clean energy and greenhouse gas resources. Among them, the development of oil and gas wells requires cementing, which is to pour cement into the gap between the steel casing and the formation to form a cement ring, which plays a role in fixing the casing, preventing casing corrosion, and preventing fluids from different layers from interpenetrating.

[0003] However, as a channel for oil and gas extraction and carbon energy injection / extraction, the wellbore faces common challenges of harsh service environment, alternating loads and long service period, which makes it easy for the cement ring to form leakage channels, resulting in annular space pressure and fluid leakage, and then the hidden dangers of major safety and environmental accidents such as wellhead fire and explosion, shallow groundwater or surface soil pollution. Therefore, it is very important to quickly and accurately identify and detect the leakage channels of the wellbore cement ring.

[0004] However, due to the limitation of wellbore structure and the barrier between production string and casing, it is very difficult to detect and identify cement sheath leakage channel. Generally, noise logging and other methods can be used to detect cement sheath leakage channel, but the operation is difficult, the cost is high, the detection reliability is poor, and the work efficiency is reduced. Summary of the invention

[0005] The present application provides a method and system for locating and detecting a leakage channel of a wellbore cement ring, which optimizes the detection process, thereby reducing the operation time and workload as much as possible, improving the reliability of detection, and improving work efficiency.

[0006] In the first aspect, the present application provides a method for locating and detecting a leakage channel of a wellbore cement ring, comprising the following steps: preliminarily determining whether the casing annulus and the oil-casing annulus are connected based on the pressure states of the casing annulus and the oil-casing annulus; wherein the casing annulus is the area between the casing and the formation, which is filled with a cement ring; the oil-casing annulus is the area between the oil pipe and the casing, which is filled with annulus liquid and annulus gas; if so, collecting the blowdown fluids of the oil-casing annulus and the casing annulus, and continuing to locate and identify the leakage channel at a specific starting position of the oil-casing annulus based on detecting the components of the blowdown fluid of the casing annulus and the blowdown fluid of the oil-casing annulus; if not, it means that the source of the leakage is not the oil-casing annulus, and the starting position of the leakage channel is located and identified based on detecting the components of the blowdown fluid of the casing annulus.

[0007] Optionally, the method of preliminarily judging whether the casing annulus and the oil casing annulus are connected based on detecting the pressure states of the casing annulus and the oil casing annulus includes: detecting whether there are pressures in the oil casing annulus and the casing annulus at the same time, and if there is a connecting point between the oil casing annulus and the casing annulus, the oil casing annulus and the casing annulus form a U-shaped tube; according to the U-shaped tube principle, operating the oil casing annulus to relieve pressure, and if the pressure of the casing annulus is synchronously reduced, it is preliminarily determined that the casing annulus and the oil casing annulus are connected; otherwise, it is determined that the casing annulus and the oil casing annulus are not connected.

[0008] Optionally, based on the components of the blowout fluid in the casing annulus and the blowout fluid in the oil casing annulus, continue to locate and identify that the leakage channel is at a specific starting position in the oil casing annulus, including: blowing out the blowout fluid in the casing annulus until the color and gas-liquid state of the blowout fluid no longer change, and then collecting the blowout fluid in the casing annulus; if the blowout fluid in the casing annulus is detected to have the same components as the blowout fluid in the oil casing annulus, it means that the starting position of the leakage channel is above the liquid level in the oil casing annulus, and locate and identify that the leakage channel is at a specific starting position in the oil casing annulus based on the noise logging method; if the blowout fluid in the casing annulus is detected to have the same components as the annulus liquid, it means that the starting position of the leakage channel is below the liquid level in the oil casing annulus, and continue to determine that the leakage channel is at a specific starting position in the oil casing annulus; wherein, in the oil casing annulus, the annulus liquid is below the annulus gas, and the boundary between the annulus gas and the annulus liquid is the liquid level in the oil casing annulus.

[0009] Optionally, the method of locating and identifying the leakage channel at a specific starting position of the casing annulus according to the noise logging method includes: if it is detected that the blowout fluid of the casing annulus is the same as the component of the blowout fluid of the casing annulus, ending the blowout, observing and recording the casing annulus pressure and the casing annulus pressure; when the casing annulus pressure and the casing annulus pressure are in a stable state, recording the values ​​of the casing annulus pressure, the casing annulus pressure and the casing annulus wellhead temperature in the stable state, and measuring the liquid level of the casing annulus; inserting a noise well logging device into the tubing string; The monitoring instrument is lowered from the liquid surface of the casing annulus to the wellhead. During the lowering process, the casing annulus pressure is kept in a stable state, and the noise profile one at this time is recorded; after being lowered to the liquid surface depth of the casing annulus, the casing annulus is blown out to release the pressure, so that the blown-out fluid flows in the cement ring, thereby generating noise; from the liquid surface of the casing annulus to the wellhead, the noise monitoring instrument is lifted up at the same time, and the noise profile two during the lifting process is recorded; the noise profile one is compared with the noise profile two, and the leakage channel is analyzed to determine that the specific starting position of the casing annulus is located.

[0010] Optionally, the noise profile 1 is compared with the noise profile 2 to analyze and determine that the leakage channel is located at a specific starting position of the casing annulus, including: due to the existence of flow noise in the pressure relief cement ring, the noise profile 2 has a spectrum different from the noise profile 1, which is recorded as abnormal spectrum 1; wherein the abnormal spectrum 1 is composed of many spectrum segments of different lengths, and there are breakpoints between adjacent spectrum segments, and the abnormal spectrum 1 is analyzed based on the abnormal spectrum breakpoint degree; when the abnormal spectrum breakpoint degree is greater than the preset breakpoint value, it is considered that the noise spectrum below this breakpoint is not generated by the fluid flow in the cement ring, and the noise spectrum above this breakpoint is taken. The abnormal spectrum is recorded as abnormal spectrum 2; based on the abnormal spectrum 2, the quality of the abnormal spectrum 2 is evaluated according to the abnormal spectrum continuity; when the abnormal spectrum continuity is lower than the preset continuity value, it is considered that the noise profile quality is unqualified, and the noise instrument needs to be re-inserted, and the pressure relief amplitude of the casing annulus is increased to obtain a new abnormal spectrum 2, and the abnormal spectrum continuity is continued to be analyzed until the abnormal spectrum continuity meets the preset continuity value; when the abnormal spectrum continuity is higher than the preset continuity value, the maximum depth of the abnormal spectrum 2 is recorded, which is the starting point of the cement sheath leakage, and the leakage channel is from this depth to the wellhead.

[0011] Optionally, if the blowdown fluid detected in the casing annulus is the same as the annulus liquid component, it means that the starting position of the leakage channel is below the liquid level of the casing annulus, and the leakage channel is further determined to be at a specific starting position of the casing annulus, including: when it is determined that the starting position of the leakage channel is below the liquid level of the casing annulus, the casing annulus pressure is released, and under the action of the pressure difference, the annulus liquid in the casing annulus will enter the casing annulus and be released out of the wellbore; as the annulus liquid is released to a certain extent, the liquid level of the casing annulus increases. When the depth reaches the connecting point of the oil-casing annulus and the casing annulus, the annular gas begins to enter the casing annulus; when the blowdown fluid of the casing annulus shows gas components, the components of the blowdown fluid of the casing annulus and the blowdown fluid of the oil-casing annulus are detected at this time. If the components are the same, the liquid level of the oil-casing annulus at this time is the starting point of the cement ring leakage channel; otherwise, continue to blowdown until it is detected that the blowdown fluid of the casing annulus is the same as the blowdown fluid of the oil-casing annulus, so as to determine the starting point of the leakage channel.

[0012] Optionally, if it is preliminarily determined that the oil-casing annulus and the casing annulus are not connected, it means that the source of the leakage is not the oil-casing annulus, and the starting position of the leakage channel is located and identified based on the detection of the fluid components blown out of the casing annulus, specifically including: if it is detected that the components of the blown fluid in the casing annulus are the same as the components of the produced fluid from the wellhead oil pipe, it is preliminarily indicated that the source of the leakage is the reservoir, and the leakage channel is the entire cement ring from the bottom of the well to the wellhead; wherein, the reservoir refers to a rock formation with connected pores that allows oil and gas to be stored and infiltrated therein, which is located at the bottom of the wellbore and connected to the wellhead through the cement ring; then, according to the tracer marking method, it is verified whether the starting position of the leakage channel is the reservoir to further determine the starting position of the leakage channel; if it is detected that the components of the blown fluid in the casing annulus are different from the components of the produced fluid from the wellhead oil pipe, then logging operations are performed to determine the leakage channel.

[0013] Optionally, verifying whether the starting position of the leakage channel is a reservoir according to the tracer marking method to further determine the starting position of the leakage channel includes: plugging the tubing string to divide the tubing string into an upper half and a lower half; after the plugging is completed, injecting the tracer from the lower half of the tubing string using a continuous pipe, and the injection pressure needs to be higher than the bottom hole pressure by a certain value. At this time, the lower half of the tubing string and the bottom hole are filled with gas containing the tracer. After the tracer is injected, the injection pressure is stabilized and the injection is stopped; the pressure recovery period of the casing annulus is obtained according to historical records, and the casing annulus is depressurized to zero and at regular intervals Collect and detect the components of the blowout fluid at intervals; if the leakage channel is the entire cement ring from the bottom of the well to the wellhead, tracers will appear in the components of the blowout fluid at the wellhead within a pressure recovery cycle. If tracers are found in the components of the blowout fluid at the wellhead according to the detection, it means that the preliminary determined source of the leakage is the reservoir, and the leakage channel is the entire cement ring from the bottom of the well to the wellhead. At this time, stop the pressure relief and blowout; if the tracer is still not detected within a pressure cycle, then extend the pressure relief time to twice the pressure recovery cycle and continue testing; if the tracer is still not detected, it means that the preliminary determined source of the leakage and channel are wrong, and well logging operations are carried out to determine the leakage channel.

[0014] Optionally, a logging operation is used to determine the leakage channel, including: lowering a noise monitoring instrument into the tubing string, the lowering range is from the wellhead to the tubing string packer, during the lowering process, the casing annulus pressure is kept in a stable state, and the noise profile three at this time is recorded; after the noise monitoring instrument is lowered to the packer depth, the casing annulus is blown out to release pressure, so that the fluid flows in the cement ring, thereby generating noise; lifting the noise monitoring instrument, and recording the noise profile four during the lifting process, during which the casing annulus needs to be continuously depressurized; comparing the noise profile three with the noise profile four, and analyzing and determining the specific starting position of the leakage channel;

[0015] Due to the existence of flow noise in the pressure relief cement ring, the noise profile 4 has a spectrum different from the noise profile 3, which is recorded as abnormal spectrum 3; wherein, the abnormal spectrum 3 is composed of many spectrum segments of different lengths, and there are breakpoints between adjacent spectrum segments. The abnormal spectrum 3 is analyzed based on the abnormal spectrum breakpoint degree; when the abnormal spectrum breakpoint degree is greater than the preset breakpoint value, it is considered that the noise spectrum below this breakpoint is not generated by the fluid flow in the cement ring, and the abnormal spectrum above this breakpoint is taken for analysis and recorded as abnormal spectrum 4; based on the abnormal spectrum 4, the abnormal spectrum continuity is evaluated. The quality of spectrum four; if the abnormal spectrum continuity is lower than the preset continuity value, the noise profile quality is considered unqualified, and the noise instrument is re-lowered. The lowering range is from the wellhead to the maximum depth where the abnormal spectrum three is located, and the pressure relief amplitude of the casing annulus is increased. After obtaining the new abnormal spectrum three, the abnormal spectrum continuity is continued to be analyzed until the abnormal spectrum continuity meets the preset continuity value; when the abnormal spectrum continuity is higher than the preset continuity value, the maximum depth of the abnormal spectrum three is recorded, which is the starting point of the cement ring leakage, and the leakage channel is from this depth to the wellhead.

[0016] In a second aspect, the present application provides a wellbore cement ring leakage channel positioning detection system, the system comprising: a preliminary judgment module, used to preliminarily judge whether the casing annulus and the oil-casing annulus are connected based on the pressure states of the casing annulus and the oil-casing annulus; wherein the casing annulus is the area between the casing and the formation, which is filled with cement ring; the oil-casing annulus is the area between the oil pipe and the casing, which is filled with annulus liquid and annulus gas; a first positioning detection module, used to judge if the casing annulus is connected to the oil-casing annulus, collect the blowout fluid of the oil-casing annulus and the casing annulus, and continue to locate and identify the leakage channel at a specific starting position of the oil-casing annulus based on the components of the blowout fluid of the casing annulus and the blowout fluid of the oil-casing annulus; a second positioning detection module, used to judge if the casing annulus and the oil-casing annulus are not connected, it means that the source of the leakage is not the oil-casing annulus, and locate and identify the starting position of the leakage channel based on the components of the blowout fluid of the casing annulus.

[0017] This application has at least the following advantages:

[0018] Based on the detection of the pressure status of the casing annulus and the oil-casing annulus, determine whether the casing annulus and the oil-casing annulus are connected, depressurize the oil-casing annulus, and collect the blowdown fluid. If the casing annulus pressure decreases synchronously, it is preliminarily determined that the casing annulus and the oil-casing annulus are connected, and the leakage channel is likely to be the oil-casing annulus, which is regarded as situation one. For situation one, the starting position of the leakage channel of the oil-casing annulus is repeatedly located and identified; if the casing annulus and the oil-casing annulus are not connected, the source of the leakage is not the oil-casing annulus, and the casing annulus pressure is blown out and the blowdown fluid is collected. Fluid, use a chromatograph to detect the components of the blown fluid. If the components are the same as the components of the fluid produced by the wellhead oil pipe, it means that the source of the leakage may be the reservoir, which is regarded as Case 2. For Case 2, the starting position of the leakage channel is verified again. If the components are different from the components of the fluid produced by the wellhead oil pipe, it is regarded as Case 3. For Case 3, the starting position of the leakage channel in the casing annulus is located and identified. Through the above reasonable steps and situation analysis, the detection process is optimized to reduce the operation time and workload as much as possible, improve the reliability of detection, and improve work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram showing a wellbore structure in one embodiment;

[0020] Figure 2 A schematic diagram of a process flow showing a method for locating and detecting a wellbore cement sheath leakage channel in one embodiment;

[0021] Figure 3 A schematic flow chart showing the steps of locating and detecting a leakage channel according to the components of the blowdown fluid in the casing annulus and the blowdown fluid in the oil casing annulus in one embodiment;

[0022] Figure 4 The present invention is a structural block diagram showing a wellbore cement ring leakage channel positioning and detection system in one embodiment.

[0023] Figure numerals: 1, formation; 2, cement ring; 3, casing; 4, tubing string; 5, packer; 6, reservoir; 7, wellhead; 8, annulus liquid; 9, annulus gas; 10, casing annulus liquid level. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when "including" and / or "comprising" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in the embodiments of the present application, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can also be implemented. The markings of the following embodiments are for convenience of description and should not constitute any limitation to the specific implementation of the present application. The various embodiments can be combined with each other and quoted from each other without contradiction.

[0027] Please refer to Figure 1 As shown, the wellbore serves as a channel for oil and gas production and carbon energy injection / production. The wellbore structure generally includes a casing 3 arranged in a wellhead 7. The lower end of the casing 3 is inserted into the reservoir 6. A space is formed between the casing 3 and the formation 1 (the side wall of the wellhead 7). The space is filled with a cement ring 2. The cement ring 2 plays a role in fixing the casing 3, preventing the casing 3 from corrosion, and preventing the fluids of different layers from communicating with each other to achieve a cementing effect. A tubing string 4 is arranged in the middle position of the casing 3. The area enclosed by the tubing string 4 and the casing 3 is filled with annulus liquid 8 and annulus gas 9. The interface between the annulus liquid 8 and the annulus gas 9 is the casing annulus liquid level 10. A packer 5 is arranged at the bottom of the casing 3, and the lower end of the tubing string 4 passes through the packer 5.

[0028] Please refer to Figure 1 , Figure 2 As shown, the embodiment of the present application provides a method for locating and detecting a wellbore cement ring leakage channel, which may include the following steps:

[0029] S201. Preliminarily determine whether the casing annulus and the oil-casing annulus are connected based on the pressure states of the casing annulus and the oil-casing annulus; wherein the casing annulus is the area between the casing 3 and the formation 1, and the area is filled with the cement annulus 2; the oil-casing annulus is the area between the oil tubing string 4 and the casing 3, and the area is filled with the annulus liquid 8 and the annulus gas 9.

[0030] S202, if yes, collect the blowout fluids in the oil-casing annulus and the casing annulus, and continue to locate and identify the specific starting position of the leakage channel in the oil-casing annulus according to the components of the blowout fluids in the casing annulus and the blowout fluids in the oil-casing annulus.

[0031] S203. If not, it means that the source of the leakage is not the casing annulus. According to the components of the blowdown fluid detected in the casing annulus, the starting position of the leakage channel is located and identified.

[0032] By detecting the pressure state of the casing annulus and the oil-casing annulus, it is preliminarily determined whether the casing annulus and the oil-casing annulus are connected. If so, the leakage channel is further located and identified at the specific starting position of the oil-casing annulus based on whether the components of the blowdown fluid in the oil-casing annulus and the casing annulus are the same. If not, it can be determined that the source of the leakage is not the oil-casing annulus, and the components of the blowdown fluid in the casing annulus are further detected and analyzed to re-locate and identify the starting position of the leakage channel.

[0033] The following is a detailed description of each step:

[0034] Please refer to Figure 1 , Figure 2 As shown, step S201, based on the pressure state of the casing annulus and the oil casing annulus, preliminarily determine whether the casing annulus and the oil casing annulus are connected;

[0035] In this embodiment, it should be noted that by detecting whether there is pressure in the oil-casing annulus and the casing annulus at the same time, if there is a connection point between the oil-casing annulus and the casing annulus, the oil-casing annulus and the casing annulus form a U-shaped tube; according to the U-shaped tube principle, the oil-casing annulus is operated to release pressure, and if the casing annulus pressure is reduced synchronously, it is preliminarily determined that the casing annulus is connected to the oil-casing annulus. Among them, the U-shaped tube is measured using the pressure difference between the two pipes. The U-shaped tube is filled with liquids such as water and mercury. When the pressure at both ends is equal, the liquid level heights of the two pipes are equal. Here, by releasing pressure on the oil-casing annulus and the casing annulus, check whether their pressure drops are consistent. If they are consistent, it means that there is a connection point between the oil-casing annulus and the casing annulus, and the leakage channel is likely to be the oil-casing annulus. This is case one, and step S202 is executed. On this basis, the specific location of the leakage can be further analyzed. Otherwise, the source of the leakage is not the oil-casing annulus, and step S203 is executed.

[0036] Please refer to Figure 2 , Figure 3 As shown, step S202, if the casing annulus is connected to the oil casing annulus, the blowout fluids of the oil casing annulus and the casing annulus are collected, and according to the components of the blowout fluids of the casing annulus and the blowout fluids of the oil casing annulus, the leakage channel is further located and identified at a specific starting position of the oil casing annulus, which specifically includes:

[0037] Step S2021, blow out the fluid in the casing annulus until the color and gas-liquid state of the blown fluid no longer change, then collect the blown fluid in the casing annulus, and detect the blown fluid in the casing annulus by collecting the blown fluid in the casing annulus, and detect the components of the blown fluid in the casing annulus and the blown fluid in the oil casing annulus.

[0038] Step S2022: If the composition of the blowdown fluid detected in the casing annulus is the same as that of the blowdown fluid in the oil-casing annulus, it means that the starting position of the leakage channel is above the liquid level in the oil-casing annulus, and the specific starting position of the leakage channel in the oil-casing annulus is located and identified based on the noise logging method; in the oil-casing annulus, the annulus liquid is below the annulus gas, and the boundary between the annulus gas and the annulus liquid is the liquid level in the oil-casing annulus.

[0039] In one example, if the components of the blowdown fluid in the casing annulus are the same as those of the blowdown fluid in the casing annulus, the blowdown is terminated, and the pressure of the casing annulus and the pressure of the casing annulus are observed and recorded; when the pressure of the casing annulus and the pressure of the casing annulus are in a stable state, the values ​​of the pressure of the casing annulus, the pressure of the casing annulus and the wellhead temperature in the stable state are recorded, and the liquid level of the casing annulus is measured; wherein, the stable state means that when the pressure of the casing annulus and the pressure of the casing annulus do not fluctuate by more than 1% within two hours, it is considered that the pressure of the casing annulus and the pressure of the casing annulus are in a stable state.

[0040] Afterwards, a noise monitoring instrument is lowered into the tubing string, and the lowering range is from the liquid surface of the casing annulus to the wellhead. During the lowering process, the pressure of the casing annulus is kept in a stable state, and the noise profile one at this time is recorded; after being lowered to the liquid surface depth of the casing annulus, the casing annulus is blown out to release pressure, so that the fluid flows in the cement ring, thereby generating noise, and the pressure relief amplitude is not less than 10% of the casing annulus pressure in the stable state; from the liquid surface of the casing annulus to the wellhead, the noise monitoring instrument is lifted up at the same time, and the noise profile two during the lifting process is recorded. During the lifting process of the noise monitoring instrument, the casing annulus needs to be continuously depressurized; by comparing the noise profile one with the noise profile two, the specific starting position of the leakage channel in the casing annulus is analyzed and determined.

[0041] Specifically, the leakage channel is determined to be located at the specific starting position of the casing annulus. According to the existence of flow noise in the pressure relief cement annulus, the noise profile 2 has a spectrum different from the noise profile 1, which is recorded as abnormal spectrum 1. Among them, the abnormal spectrum 1 is composed of many spectrum segments of different lengths, and there are breakpoints between adjacent spectrum segments. The abnormal spectrum breakpoint degree is defined to analyze the abnormal spectrum 1, as shown in formula (1):

[0042] LD=LD i+1 ÷LY

[0043] Where LD is the abnormal spectrum breakpoint degree, dimensionless, LD i-1is the distance between the i-th abnormal spectrum and the i+1-th abnormal spectrum, m; LY is the distance from the deepest point where the abnormal spectrum appears to the wellhead, m.

[0044] Abnormal spectrum one is analyzed based on the abnormal spectrum breakpoint degree; when the abnormal spectrum breakpoint degree is greater than the preset breakpoint value, which can be 0.2, it is considered that the noise spectrum below this breakpoint is not generated by the fluid flow in the cement sheath, and the abnormal spectrum above this breakpoint is recorded as abnormal spectrum two; if it is less than 0.2, it is considered that they are two adjacent segments, and the i-th and i+1-th abnormal spectra are both generated by the fluid flow in the cement sheath, indicating that the leakage is continuous.

[0045] Based on the abnormal spectrum 2, the quality of the abnormal spectrum 2 is evaluated according to the abnormal spectrum continuity; wherein the abnormal spectrum continuity is defined as shown in formula (2):

[0046]

[0047] Where LX is the abnormal spectrum continuity, dimensionless, j is the number of the abnormal spectrum segment on the abnormal spectrum 2, dimensionless, N is the total number of abnormal spectrum segments on the abnormal spectrum 2, dimensionless, LF j is the length of the jth abnormal spectrum, m.

[0048] When the abnormal spectrum continuity is lower than the preset continuity value, which can be 0.8, the noise profile quality is considered unqualified, which will weaken the reliability of the leakage channel positioning and identification results. The noise instrument needs to be re-inserted. The range of the lowering is from the wellhead to the maximum depth of the abnormal spectrum 2. In order to improve the quality of the abnormal spectrum 2, the noise instrument needs to be lowered this time. The pressure relief amplitude of the casing annulus needs to be increased to obtain a new abnormal spectrum 2, and the abnormal spectrum continuity is continuously analyzed until the abnormal spectrum continuity meets the preset continuity value; specifically, the pressure relief amplitude of the casing annulus is increased by no less than 30% of the previous pressure relief amplitude. For example, if the last leakage amplitude is 5MPa, the pressure relief amplitude this time is no less than 6.5MPa to obtain a new abnormal spectrum 2. When the abnormal spectrum continuity is higher than the preset continuity value, the maximum depth of the abnormal spectrum 2 is recorded, which is the starting point of the cement ring leakage, and the leakage channel is from this depth to the wellhead.

[0049] Step S2023: If the blowdown fluid detected in the casing annulus is the same as the annulus liquid component, it means that the starting position of the leakage channel is below the liquid level of the casing annulus, and the leakage channel is further determined to be at a specific starting position of the casing annulus;

[0050] In this embodiment, it should be noted that when the starting position of the leakage channel is determined to be below the liquid level of the oil-casing annulus, the pressure py on the oil-casing annulus side at the starting position is composed of the oil-casing annulus pressure, the liquid column pressure and the gas column pressure, and the pressure pt on the casing annulus side is composed of the casing annulus pressure and the liquid column pressure. At this time, the casing annulus pressure is released, and under the action of the pressure difference, the annular space liquid in the oil-casing annulus will enter the casing annulus and be released out of the wellbore; as the annular space liquid is released to a certain extent, the depth of the oil-casing annulus liquid level reaches the connection point between the oil-casing annulus and the casing annulus, and the annular space gas begins to enter the casing annulus; when the blowout fluid of the casing annulus shows gas components, the components of the blowout fluid of the casing annulus and the blowout fluid of the oil-casing annulus are detected at this time. If the components are the same, the oil-casing annulus liquid level at this time is the starting point of the cement ring leakage channel; otherwise, continue to blowout until it is detected that the blowout fluid of the casing annulus and the blowout fluid of the oil-casing annulus are the same, so as to determine the starting point of the leakage channel.

[0051] Please refer to Figure 2 As shown, in step S203, if it is preliminarily determined that the oil-casing annulus is not connected to the casing annulus, it means that the source of the leakage is not the oil-casing annulus. According to the components of the blowdown fluid detected in the casing annulus, the starting position of the leakage channel is located and identified, which specifically includes:

[0052] The casing annulus pressure is released and the released fluid is collected. The components of the released fluid are detected by chromatograph. If the components are the same as the components of the fluid produced by the wellhead oil pipe, it means that the source of the leakage may be the reservoir, and it is recorded as situation 2, and steps 2.1-2.4 are executed. Otherwise, it is recorded as situation 3 and steps 3.1-3.6 are executed.

[0053] Steps 2.1-2.4: Verify the starting position of the leakage channel for situation 2.

[0054] In case 2, it has been preliminarily determined that the source of the leakage is the reservoir. The reservoir refers to a rock layer with interconnected pores that allows oil and gas to be stored and infiltrated. It is located at the bottom of the wellbore. The cement ring connects the reservoir and the wellhead. Therefore, if the components of the blowdown fluid in the casing annulus are detected to be the same as the components of the output fluid of the wellhead oil pipe, it means that the leakage channel is the entire cement ring from the bottom of the well to the wellhead. However, it is still necessary to conduct further verification to avoid misjudgment. The verification method uses tracer marking. The specific method is as follows:

[0055] Step 2.1, plugging the tubing string so that the tubing string is divided into an upper half and a lower half. In one example, the isolation method is to use a coiled tubing to run into an internal packer, wherein the outlet of the coiled tubing should be deep into the bottom of the well, and the isolation position should be about 5 to 10 meters below the packer of the tubing string.

[0056] Step 2.2: After plugging is completed, use coiled tubing to inject tracers such as helium from the lower half of the tubing string. The injection pressure needs to be higher than the bottom hole pressure by a certain value, such as 5-10MPa. At this time, the lower half of the tubing string and the bottom hole are filled with gas containing tracers. After the tracer is injected, stabilize the injection pressure and stop the injection.

[0057] Step 2.3, obtain the pressure recovery cycle of the casing annulus pressure according to historical records. Perform pressure relief operation on the casing annulus to reduce the pressure to zero; if the pressure cannot be reduced to zero, open the pressure relief valve to the maximum extent. Collect and detect the components of the blowout fluid at regular intervals. If the leakage channel is the entire cement ring from the bottom of the well to the wellhead, then tracers will appear in the components of the blowout fluid at the wellhead within a pressure recovery cycle. If tracers are detected, it means that the leak source and channel initially determined are correct, and the pressure relief blowout should be stopped.

[0058] Step 2.4: If the tracer is still not detected within one pressure cycle, extend the pressure relief time to twice the pressure recovery cycle. If the tracer is still not detected, it means that the initial leak source and channel are wrong. At this time, it is necessary to perform steps 3.1-3.6 and perform well logging operations to determine the leak channel.

[0059] Steps 3.1-3.6: Identify and locate the starting point of the leakage channel for situation 3

[0060] If the composition of the blowdown fluid in the casing annulus is different from that of the produced fluid in the wellhead tubing, or if the tracer cannot be detected, logging operations are required to determine the leakage path. The specific methods are as follows:

[0061] Step 3.1. Lower the noise monitoring instrument into the tubing string. The lowering range is from the wellhead to the packer of the tubing string. During the lowering process, keep the casing annulus pressure in a stable state and record the noise profile at this time.

[0062] Step 3.2: After the noise monitoring instrument is lowered to the packer depth, the casing annulus is blown out to release pressure, so that the fluid flows in the cement annulus, thereby generating noise, wherein the pressure relief amplitude is not less than 10% of the annulus pressure in a stable state.

[0063] Step 3.3: Lift up the noise monitoring instrument and record the noise profile during the lifting process. During the lifting of the noise monitoring instrument, the casing annulus needs to be continuously depressurized.

[0064] Step 3.4: Compare noise profile 3 with noise profile 4 to analyze and determine the specific starting position of the leakage channel.

[0065] In one example, noise profile 3 is compared with noise profile 4, and the specific starting position of the leakage channel is analyzed and determined based on the existence of flow noise in the pressure relief cement ring. Noise profile 3 has a spectrum different from noise profile 4, which is recorded as abnormal spectrum 3; wherein, abnormal spectrum 3 is composed of many spectrum segments of different lengths, and there are breakpoints between adjacent spectrum segments. Abnormal spectrum 3 is analyzed based on the abnormal spectrum breakpoint degree; if the abnormal spectrum breakpoint degree is defined to analyze abnormal spectrum 3, it is shown in the following formula:

[0066] LD=LD i+1 ÷LY

[0067] Where, LD is the abnormal spectrum breakpoint degree, dimensionless; LD i-1 is the distance between the i-th abnormal spectrum and the i+1-th abnormal spectrum, m; LY is the distance from the deepest point where the abnormal spectrum appears to the wellhead, m.

[0068] When the abnormal spectrum breakpoint degree is greater than the preset breakpoint value, such as 0.2, it is considered that the noise spectrum below this breakpoint is not generated by the fluid flow in the cement sheath. The abnormal spectrum above this breakpoint is analyzed and recorded as abnormal spectrum four.

[0069] Step 3.5: Based on abnormal spectrum 4, define abnormal spectrum continuity to evaluate the quality of abnormal spectrum 4. The abnormal spectrum continuity is defined as shown in the formula.

[0070]

[0071] Where, LX is the abnormal spectrum continuity, dimensionless; j is the number of the abnormal spectrum segment on the abnormal spectrum 3, dimensionless; N is the total number of abnormal spectrum segments on the abnormal spectrum 3, dimensionless. LF j is the length of the jth abnormal spectrum, m.

[0072] If the abnormal spectrum continuity is lower than the preset continuity value, such as 0.8, the noise profile quality is considered unqualified, and step 3.6 is executed. When the abnormal spectrum continuity is higher than the preset continuity value, that is, it meets the requirements, the maximum depth of abnormal spectrum 3 is recorded at this time, which is the starting point of cement sheath leakage, and the leakage channel is from this depth to the wellhead.

[0073] Step 3.6, re-insert the noise instrument, the insertion range is from the wellhead to the maximum depth of the abnormal spectrum 3. In order to improve the quality of the abnormal spectrum 3, the pressure relief amplitude of the casing annulus needs to be increased by not less than 30% of the previous pressure relief amplitude. For example, if the last leakage amplitude is 5MPa, the pressure relief amplitude this time is not less than 6.5MPa. After obtaining the new abnormal spectrum 3, return to step 3.4.

[0074] The implementation principle of this embodiment: The above steps are mainly based on the U-tube principle, based on the pressure state of the casing annulus and the oil casing annulus to determine whether the casing annulus and the oil casing annulus are connected, so as to preliminarily determine the source of the leakage, which is specifically divided into situation 1 and situation 2. If they are connected, it meets situation 1, that is, according to the same components of the blowdown fluid in the casing annulus and the blowdown fluid in the oil casing annulus, it is determined that the starting position of the leakage channel is above the oil casing annulus liquid level, and the specific starting point and leakage channel of the cement ring leakage are finally determined according to the monitoring and analysis of the noise of the tubing string; if it is found that the components of the blowdown fluid in the casing annulus are the same as those of the annular liquid, it is determined that the starting position of the leakage channel is below the oil casing annulus liquid level, and when the blowdown fluid in the casing annulus is detected to have a gas component, and the blowdown fluid in the casing annulus and the blowdown fluid in the oil casing annulus are detected to have the same components, it is determined that the annular liquid level at this time is the starting point of the cement ring leakage channel.

[0075] If the casing annulus and the oil casing annulus are not connected, it meets the second situation. According to the detection of the components of the blowout fluid in the casing annulus and the components of the wellhead production fluid, it is possible that the source of the leakage is the reservoir. Tracer marking is used for further verification, the oil pipe is blocked, and the tracer is injected. If the tracer is detected in the components of the wellhead blowout fluid within a pressure recovery cycle, it is determined that the source and channel of the leakage is the reservoir, and the leakage channel is the entire cement ring from the bottom of the well to the wellhead. If the pressure relief continues and the tracer is not detected, then the logging operation is carried out to determine the leakage channel, that is, the analysis and judgment of the third situation is carried out.

[0076] In case 3, a noise monitor is placed inside the oil pipe string to determine the source and channel of the leak based on the noise profile formed by monitoring and analysis.

[0077] Based on the preliminary identification of the leakage source, the leakage source is further divided into situation one, situation two and situation three according to the analysis to detect and identify the starting position of the leakage channel. Through reasonable steps and situation analysis, the limitations of the wellbore structure and the barrier between the tubing string and the casing are overcome, the detection process is optimized, and the workload of detecting cement sheath leakage channels through downhole operations such as noise logging is reduced, the difficulty and cost of the operation are reduced, the reliability of detection is improved, and the work efficiency is improved.

[0078] Reference Figure 4 As shown, the present application also provides a wellbore cement ring leakage channel positioning detection system, which can include: a preliminary judgment module 301, a first positioning detection module 302, and a second positioning detection module 303. The main functions of each component module are as follows:

[0079] The preliminary judgment module 301 is used to preliminarily judge whether the casing annulus and the oil-casing annulus are connected according to the pressure states of the casing annulus and the oil-casing annulus; wherein the casing annulus is the area between the casing and the formation, which is filled with cement sheath; the oil-casing annulus is the area between the oil tubing string and the casing, which is filled with annulus liquid and annulus gas;

[0080] The first positioning detection module 302 is used to determine if the casing annulus is connected to the oil-casing annulus, collect the blowout fluids of the oil-casing annulus and the casing annulus, and continue to locate and identify the leakage channel at a specific starting position of the oil-casing annulus according to the components of the blowout fluids of the casing annulus and the blowout fluids of the oil-casing annulus;

[0081] The second positioning detection module 302 is used to determine that if the casing annulus is not connected to the oil-casing annulus, it means that the source of the leakage is not the oil-casing annulus, and locate and identify the starting position of the leakage channel according to the components of the blowdown fluid detected in the casing annulus.

[0082] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A method for locating and detecting a wellbore cement ring leakage channel, characterized in that: The following steps are involved: Preliminarily judging whether the casing annulus and the oil casing annulus are connected according to the pressure states of the casing annulus and the oil casing annulus, including: Detecting whether the oil-casing annulus and the casing annulus are under pressure at the same time; if there is a connection point between the oil-casing annulus and the casing annulus, the oil-casing annulus and the casing annulus form a U-shaped tube; According to the U-tube principle, the oil-casing annulus is operated to release pressure. If the pressure of the casing annulus is reduced synchronously, it is preliminarily determined that the casing annulus is connected with the oil-casing annulus; Otherwise, it is determined that the casing annulus is not connected to the oil casing annulus; The casing annulus is the area between the casing and the formation, which is filled with cement sheath; the oil casing annulus is the area between the oil tubing string and the casing, which is filled with annulus liquid and annulus gas; If yes, then collecting the blowout fluids in the oil-casing annulus and the casing annulus, and continuing to locate and identify the leakage channel at a specific starting position of the oil-casing annulus according to the components of the blowout fluids in the casing annulus and the blowout fluids in the oil-casing annulus, including: Spraying the blowdown fluid in the casing annulus until the color and gas-liquid state of the blowdown fluid no longer change, and collecting the blowdown fluid in the casing annulus; If the blowout fluid detected in the casing annulus is the same as the blowout fluid in the oil casing annulus, it means that the starting position of the leakage channel is above the liquid level in the oil casing annulus, and the leakage channel is located and identified at the specific starting position of the oil casing annulus according to the noise logging method; If the blowdown fluid detected in the casing annulus is the same as the annulus liquid component, it means that the starting position of the leakage channel is below the oil-casing annulus liquid level, and the leakage channel is further determined to be at a specific starting position in the oil-casing annulus; wherein, in the oil-casing annulus, the annulus liquid is below the annulus gas, and the boundary between the annulus gas and the annulus liquid is the oil-casing annulus liquid level; If not, it means that the source of the leakage is not the oil casing annulus. According to the components of the blowdown fluid detected in the casing annulus, the starting position of the leakage channel is located and identified, including: If it is detected that the composition of the blowout fluid in the casing annulus is the same as the composition of the output fluid from the wellhead oil pipe, it is preliminarily indicated that the source of the leakage is the reservoir, and the leakage channel is the entire cement ring from the bottom of the well to the wellhead; wherein the reservoir refers to a rock formation with interconnected pores that allows oil and gas to be stored and permeated therein, located at the bottom of the wellbore, and connected to the wellhead through the cement ring; Then, the starting position of the leakage channel is verified to be the reservoir according to the tracer marking method, so as to further determine the starting position of the leakage channel, including: Blocking the oil pipe string so that the oil pipe string is divided into an upper half and a lower half; After plugging is completed, a tracer is injected from the lower half of the tubing string using a coiled tube. The injection pressure needs to be higher than the bottom hole pressure by a certain value. At this time, the lower half of the tubing string and the bottom hole are filled with gas containing the tracer. After the tracer is injected, the injection pressure is stabilized and the injection is stopped. Obtain the pressure recovery period of the casing annulus according to historical records, perform pressure relief operation on the casing annulus, relieve the pressure to zero, and collect and detect the components of the blowdown fluid at regular time intervals; If the leakage channel is the entire cement ring from the bottom of the well to the wellhead, then tracers will appear in the components of the wellhead blowout fluid during a pressure recovery cycle. If tracers are found in the components of the wellhead blowout fluid according to the test, it means that the preliminary confirmed source of the leakage is the reservoir, and the leakage channel is the entire cement ring from the bottom of the well to the wellhead. At this time, the pressure relief blowout should be stopped; If the tracer is still not detected within one pressure cycle, extend the pressure relief time to twice the pressure recovery cycle and continue testing; If the tracer still cannot be detected, it means that the leak source and channel initially determined are wrong, and logging operations should be carried out to determine the leak channel; If it is detected that the composition of the blowdown fluid in the casing annulus is different from the composition of the produced fluid from the wellhead oil pipe, a well logging operation is performed to determine the leakage path.

2. The method for locating and detecting the leakage channel of the wellbore cement ring according to claim 1 is characterized in that: The method of locating and identifying the leakage channel at a specific starting position of the casing annulus according to the noise logging method includes: If it is detected that the blowout fluid in the casing annulus is the same as the blowout fluid in the oil casing annulus, the blowout is terminated, and the pressures of the casing annulus and the oil casing annulus are observed and recorded; When the casing annulus pressure and the oil casing annulus pressure are in a stable state, the values ​​of the casing annulus pressure, the oil casing annulus pressure and the oil casing annulus wellhead temperature in the stable state are recorded, and the liquid level height of the oil casing annulus is measured; A noise monitoring instrument is lowered into the oil pipe string, and the lowering range is from the oil casing annulus liquid level to the wellhead. During the lowering process, the casing annulus pressure is kept in a stable state, and the noise profile at this time is recorded; after lowering to the oil casing annulus liquid level depth, the casing annulus is blown out and pressure is released, so that the blown out fluid flows in the cement ring, thereby generating noise; When the liquid level in the casing annulus reaches the wellhead, the noise monitoring instrument is simultaneously lifted to record the second noise profile during the lifting process; By comparing the noise profile 1 with the noise profile 2, it is analyzed and determined that the leakage channel is located at a specific starting position of the oil casing annulus.

3. The method for locating and detecting the leakage channel of the wellbore cement ring according to claim 2 is characterized in that: The comparing the noise profile 1 with the noise profile 2 and analyzing and determining that the leakage channel is located at a specific starting position of the oil casing annulus includes: Due to the existence of flow noise in the pressure relief cement ring, the noise profile 2 has a spectrum different from the noise profile 1, which is recorded as abnormal spectrum 1; wherein, The abnormal spectrum 1 is composed of many spectrum segments of different lengths, and there are breakpoints between adjacent spectrum segments. The abnormal spectrum 1 is analyzed based on the abnormal spectrum breakpoint degree; When the abnormal spectrum breakpoint degree is greater than the preset breakpoint value, it is considered that the noise spectrum below the breakpoint is not generated by the fluid flow in the cement sheath, and the abnormal spectrum above the breakpoint is recorded as abnormal spectrum 2; based on the abnormal spectrum 2, the quality of abnormal spectrum 2 is evaluated according to the abnormal spectrum continuity; When the abnormal spectrum continuity is lower than the preset continuity value, it is considered that the noise profile quality is unqualified, and the noise instrument needs to be re-inserted, and the pressure relief amplitude of the casing annulus is increased to obtain a new abnormal spectrum 2, and continue to analyze the abnormal spectrum continuity until the abnormal spectrum continuity meets the preset continuity value; When the abnormal spectrum continuity is higher than the preset continuity value, the maximum depth of the abnormal spectrum 2 is recorded, which is the starting point of cement sheath leakage, and the leakage channel is from this depth to the wellhead.

4. The method for locating and detecting a wellbore cement sheath leakage channel according to claim 1, characterized in that: If the blowdown fluid detected in the casing annulus is the same as the annulus liquid component, it means that the starting position of the leakage channel is below the liquid level of the casing annulus, and further determining the specific starting position of the leakage channel in the casing annulus includes: When it is determined that the starting position of the leakage channel is below the liquid level of the oil-casing annulus, the casing annulus pressure is released, and under the action of the pressure difference, the annular space liquid in the oil-casing annulus will enter the casing annulus and be released out of the wellbore; As the annular space liquid is released to a certain extent, the depth of the oil-casing annular space liquid level reaches the connecting point of the oil-casing annular space and the casing annular space, and the annular space gas begins to enter the casing annular space; when the blowdown fluid of the casing annular space shows gas components, the components of the blowdown fluid of the casing annular space and the blowdown fluid of the oil-casing annular space are detected at this time. If the components are the same, the oil-casing annular space liquid level at this time is the starting point of the cement sheath leakage channel; Otherwise, the blowout is continued until it is detected that the blowout fluid in the casing annulus has the same component as the blowout fluid in the oil casing annulus, so as to determine the starting point of the leakage channel.

5. The method for locating and detecting a wellbore cement sheath leakage channel according to claim 1, characterized in that: Well logging operations are used to identify leakage paths, including: A noise monitoring instrument is lowered into the tubing string, and the lowering range is from the wellhead to the tubing string packer. During the lowering process, the casing annulus pressure is kept in a stable state, and the noise profile three at this time is recorded; After the noise monitoring instrument is lowered to the packer depth, the casing annulus is blown out to release pressure, so that the fluid flows in the cement annulus, thereby generating noise; Lifting the noise monitoring instrument, recording the noise profile during the lifting process; during the lifting process of the noise monitoring instrument, the casing annulus needs to be continuously depressurized; Comparing the noise profile three with the noise profile four, analyzing and determining the specific starting position of the leakage channel; Due to the existence of flow noise in the pressure relief cement ring, the noise profile 4 has a spectrum different from the noise profile 3, which is recorded as abnormal spectrum 3; wherein, the abnormal spectrum 3 is composed of many spectrum segments of different lengths, and there are breakpoints between adjacent spectrum segments. The abnormal spectrum 3 is analyzed based on the abnormal spectrum breakpoint degree; when the abnormal spectrum breakpoint degree is greater than the preset breakpoint value, it is considered that the noise spectrum below this breakpoint is not generated by the fluid flow in the cement ring, and the abnormal spectrum above this breakpoint is taken for analysis and recorded as abnormal spectrum 4; Based on the abnormal spectrum four, evaluating the quality of the abnormal spectrum four according to the abnormal spectrum continuity; If the abnormal spectrum continuity is lower than the preset continuity value, it is considered that the noise profile quality is unqualified, and the noise instrument is re-inserted, and the range of the lowering is from the wellhead to the maximum depth where the abnormal spectrum 3 is located, and the pressure relief amplitude of the casing annulus is increased. After obtaining the new abnormal spectrum 3, the abnormal spectrum continuity is continuously analyzed until the abnormal spectrum continuity meets the preset continuity value; When the abnormal spectrum continuity is higher than the preset continuity value, the maximum depth of the abnormal spectrum 3 is recorded, which is the starting point of cement sheath leakage, and the leakage channel is from this depth to the wellhead.

6. A wellbore cement ring leakage channel positioning detection system, characterized in that: include: A preliminary judgment module, wherein the preliminary judgment module preliminarily judges whether the casing annulus and the oil casing annulus are connected according to the pressure state of the casing annulus and the oil casing annulus, including: Detecting whether the oil-casing annulus and the casing annulus are under pressure at the same time; if there is a connection point between the oil-casing annulus and the casing annulus, the oil-casing annulus and the casing annulus form a U-shaped tube; According to the U-tube principle, the oil-casing annulus is operated to release pressure. If the pressure of the casing annulus is reduced synchronously, it is preliminarily determined that the casing annulus is connected with the oil-casing annulus; Otherwise, it is determined that the casing annulus is not connected to the oil casing annulus; The casing annulus is the area between the casing and the formation, which is filled with cement sheath; the oil casing annulus is the area between the oil tubing string and the casing, which is filled with annulus liquid and annulus gas; The first positioning detection module determines that if the casing annulus is connected to the oil casing annulus, then collects the blowout fluid of the oil casing annulus and the casing annulus. The first positioning detection module continues to locate and identify the leakage channel at a specific starting position of the oil casing annulus according to the components of the blowout fluid of the casing annulus and the blowout fluid of the oil casing annulus, including: Spraying the blowdown fluid in the casing annulus until the color and gas-liquid state of the blowdown fluid no longer change, and collecting the blowdown fluid in the casing annulus; If the blowout fluid detected in the casing annulus is the same as the blowout fluid in the oil casing annulus, it means that the starting position of the leakage channel is above the liquid level in the oil casing annulus, and the leakage channel is located and identified at the specific starting position of the oil casing annulus according to the noise logging method; If the blowdown fluid detected in the casing annulus is the same as the annulus liquid component, it means that the starting position of the leakage channel is below the oil-casing annulus liquid level, and the leakage channel is further determined to be at a specific starting position in the oil-casing annulus; wherein, in the oil-casing annulus, the annulus liquid is below the annulus gas, and the boundary between the annulus gas and the annulus liquid is the oil-casing annulus liquid level; The second positioning detection module determines that if the casing annulus is not connected to the oil casing annulus, it means that the source of the leakage is not the oil casing annulus. The second positioning detection module locates and identifies the starting position of the leakage channel according to the components of the blowdown fluid detected in the casing annulus, including: If it is detected that the composition of the blowout fluid in the casing annulus is the same as the composition of the output fluid from the wellhead oil pipe, it is preliminarily indicated that the source of the leakage is the reservoir, and the leakage channel is the entire cement ring from the bottom of the well to the wellhead; wherein the reservoir refers to a rock formation with interconnected pores that allows oil and gas to be stored and permeated therein, located at the bottom of the wellbore, and connected to the wellhead through the cement ring; Then, the starting position of the leakage channel is verified to be the reservoir according to the tracer marking method, so as to further determine the starting position of the leakage channel, including: Blocking the oil pipe string so that the oil pipe string is divided into an upper half and a lower half; After plugging is completed, a tracer is injected from the lower half of the tubing string using a coiled tube. The injection pressure needs to be higher than the bottom hole pressure by a certain value. At this time, the lower half of the tubing string and the bottom hole are filled with gas containing the tracer. After the tracer is injected, the injection pressure is stabilized and the injection is stopped. Obtain the pressure recovery period of the casing annulus according to historical records, perform pressure relief operation on the casing annulus, relieve the pressure to zero, and collect and detect the components of the blowdown fluid at regular time intervals; If the leakage channel is the entire cement ring from the bottom of the well to the wellhead, then tracers will appear in the components of the wellhead blowout fluid during a pressure recovery cycle. If tracers are found in the components of the wellhead blowout fluid according to the test, it means that the preliminary confirmed source of the leakage is the reservoir, and the leakage channel is the entire cement ring from the bottom of the well to the wellhead. At this time, the pressure relief blowout should be stopped; If the tracer is still not detected within one pressure cycle, extend the pressure relief time to twice the pressure recovery cycle and continue testing; If the tracer still cannot be detected, it means that the leak source and channel initially determined are wrong, and logging operations should be carried out to determine the leak channel; If it is detected that the composition of the blowdown fluid in the casing annulus is different from the composition of the produced fluid from the wellhead oil pipe, a well logging operation is performed to determine the leakage path.

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