A monitoring string for abnormal casing pressure of an injection well with separate layers and its monitoring method

Abstract

The present invention provides a layered water injection well casing pressure abnormal monitoring string and a monitoring method thereof. The wellhead cross is installed at the wellhead. A casing is arranged in the wellhead and is connected to the wellhead cross. The tubing extends into the casing from the wellhead. A casing pressure abnormal monitoring device is arranged in the middle of the tubing. A sealing cylinder is installed outside the casing pressure abnormal monitoring device. The packer is connected to the sealing cylinder, thereby achieving the purpose of sealing the annulus between the tubing and the casing. The tail end of the tubing is sequentially provided with a perforated insert seal and a plug from top to bottom. A screen pipe is installed at the tail end of the sealing cylinder. The annulus between the tubing and the casing is divided into two parts by the screen pipe, namely, the annulus between the tubing and the screen pipe and the annulus between the screen pipe and the casing. By different water injection methods, the change law of the casing pressure is monitored by using the built-in pressure gauge, and factors such as the damage of the casing and the tubing that may cause abnormal casing pressure, and the sealing performance of the packer and the sealing module are judged.

Description

Technical Field

[0001] The present invention relates to the technical field of abnormal monitoring of the casing pressure of stratified water injection wells in oil fields, and more specifically to a pipe string for abnormal monitoring of the casing pressure of stratified water injection wells and a monitoring method therefor. Background Art

[0002] At present, there are 722 water injection wells in the Bohai Oilfield. According to incomplete statistics, there are more than 100 well times with different degrees of casing pressure problems at the wellhead, and the number of well times that need to be solved urgently is on the rise. The wellhead with pressure is likely to cause hidden danger valves at the wellhead of the Christmas tree, valve failures, and there are certain hidden dangers to the safe operation of production operators and downhole operation personnel at the wellhead. The traditional method to solve the casing pressure is to carry out major repairs and then completion operations, which have a long construction period and high operation costs. The understanding of the causes of the annulus pressure problem in water injection wells is relatively general. Generally, it is considered that the annulus pressure is caused by the deformation of the water injection pipe string, resulting in the failure of the sealing equipment, or the annulus pressure problem caused by water quality, pipe string material, or the scaling and corrosion damage of the water injection pipe string.

[0003] At present, the casing pressure control technology mainly adopts the method of optimizing the pipe string structure and the sealing performance of production enhancement sealing tools, which cannot achieve effective sealing under complex downhole conditions such as long pipe strings and corrosive liquids. Therefore, it is necessary to explore the variation law of the casing pressure of water injection wells for abnormal casing pressure conditions. Improve the safety factor of the casing and wellhead equipment, reduce the operation cost of high casing pressure wells, and improve the workover efficiency. Summary of the Invention

[0004] The present invention overcomes the deficiencies in the prior art. The existing control technology has the problem of low safety factor, and provides a pipe string for abnormal monitoring of the casing pressure of stratified water injection wells and a monitoring method therefor. By different water injection methods, the variation law of the casing pressure is monitored by using the built-in pressure gauge, and factors such as damage to the casing and tubing that may cause abnormal casing pressure, and the sealing performance of the packer and the sealing module are judged, which is beneficial to improving the workover efficiency and increasing the safety factor of the casing and wellhead equipment.

[0005] The object of the present invention is achieved by the following technical solutions.

[0006] A layered water injection well casing pressure abnormal monitoring string, comprising a tubing string, a wellhead cross, a casing, a casing pressure abnormal monitoring device, a screen pipe and a plug. The wellhead cross is installed at the wellhead, the casing is arranged in the wellhead, the casing is connected to the wellhead cross, the tubing string extends into the casing from the wellhead, the casing pressure abnormal monitoring device is arranged in the middle of the tubing string, a sealing cylinder is installed outside the casing pressure abnormal monitoring device, and a packer is connected to the sealing cylinder, so as to achieve the purpose of sealing the annulus between the tubing string and the casing. The tail end of the tubing string is successively provided with a perforated insert seal and the plug from top to bottom, and the screen pipe is installed at the tail end of the sealing cylinder. The annulus between the tubing string and the casing is divided into two parts by the screen pipe, namely the annulus between the tubing string and the screen pipe and the annulus between the screen pipe and the casing;

[0007] The casing pressure abnormal monitoring device includes a ball injection nipple, an upper pressure gauge nipple, a seal test joint and a lower pressure gauge nipple. The head end of the ball injection nipple is connected to the tubing string. A shear pin hole is formed in the middle of the ball injection nipple, and a ball seat is fixed in the ball injection nipple by a shear pin arranged in the shear pin hole. The tail end of the ball injection nipple is connected to the head end of the upper pressure gauge nipple. An upper pressure gauge mounting platform is formed on the inner wall of the upper pressure gauge nipple. The upper pressure gauge mounting platform divides the upper pressure gauge nipple into a structure with both ends open and the middle non-connected. An upper pressure gauge measuring hole is formed on the side of the upper pressure gauge mounting platform. The upper pressure gauge is installed on the upper pressure gauge mounting platform and is connected to the upper pressure gauge measuring hole. The tail end of the upper pressure gauge nipple is connected to the head end of the seal test joint. A seal test pressure gauge mounting platform is formed on the inner wall of the seal test joint. The seal test pressure gauge mounting platform divides the seal test joint into a structure with both ends open and the middle non-connected. A seal test pressure gauge measuring hole is formed on the side of the seal test pressure gauge mounting platform. The seal test pressure gauge is installed on the seal test pressure gauge mounting platform and is connected to the seal test pressure gauge measuring hole. The tail end of the seal test joint is connected to the head end of the lower pressure gauge nipple. A lower pressure gauge mounting platform is formed on the inner wall of the lower pressure gauge nipple. The lower pressure gauge mounting platform divides the lower pressure gauge nipple into a structure with both ends open and the middle non-connected. A lower pressure gauge measuring hole is formed on the side of the lower pressure gauge mounting platform. The lower pressure gauge is installed on the lower pressure gauge mounting platform and is connected to the lower pressure gauge measuring hole. The tail end of the lower pressure gauge nipple is connected to the tubing string, and bridge channels are formed on the side walls of the upper pressure gauge nipple, the seal test joint and the lower pressure gauge nipple, so as to achieve the purpose that when the fluid in the tubing string passes through the upper pressure gauge nipple, the seal test joint and the lower pressure gauge nipple successively from top to bottom, the fluid can flow normally.

[0008] Sealing grooves are uniformly formed on the outer wall of the tail end of the upper pressure gauge nipple and the outer wall of the middle part of the sealing test joint. A sealing module is arranged in the sealing groove. An annular sealing cavity is formed among the sealing module of the upper pressure gauge nipple, the sealing test nipple, the sealing cylinder and the sealing module of the sealing test nipple. The pressure in the above annular sealing cavity can be measured by using a sealing test pressure gauge.

[0009] A pressure relief hole is also provided on the side wall of the ball injection nipple, and the pressure relief hole is located above or below the pin hole.

[0010] A blowout preventer is also provided on the wellhead four-way.

[0011] Packers are sequentially arranged from top to bottom in the annulus between the screen pipe and the casing to achieve the purpose of dividing the annulus between the screen pipe and the casing into non-connected water injection layers.

[0012] A monitoring method for the abnormal casing pressure of a stratified water injection well string is carried out according to the following steps:

[0013] Step 1, overall investigation: If the casing pressure remains stable and unchanged during reverse injection, it indicates that the casing and the tubing are not damaged, and the sealing rubber cylinders of the packer and the monitoring string are in good condition, indicating that the casing pressure of this well is normal, and the detection is ended;

[0014] On the contrary, if the casing pressure cannot be stabilized during reverse injection, it indicates that the tubing and the casing may be damaged, or the sealing rubber cylinders of the packer and the monitoring string are damaged, resulting in sealing failure, and enter Step 2;

[0015] Step 2, check the tubing. After throwing a ball into the abnormal casing pressure monitoring device and injecting water forward, if the playback tubing pressure data is stable, it indicates that the tubing is in good condition, and enter Step 3;

[0016] If the playback tubing pressure data is unstable, it indicates that the tubing is damaged, resulting in abnormal casing pressure, and the detection is ended;

[0017] Step 3, check the sealing module. If the playback data of the sealing test pressure gauge does not change during forward and reverse water injection, it indicates that the sealing rubber cylinder performance of the monitoring string is good, and enter Step 4;

[0018] If the playback data of the sealing test pressure gauge is unstable, it indicates that the sealing rubber cylinder of the monitoring string is damaged, resulting in abnormal casing pressure, and the detection is ended;

[0019] Step 4, check the packer. If the pressure is stable when injecting water forward after throwing a ball into the abnormal casing pressure monitoring device, while the casing pressure increases when injecting water forward before throwing a ball into the abnormal casing pressure monitoring device, and at the same time, the sealing rubber cylinder performance of the monitoring string is good, it indicates that the sealing rubber cylinder of the packer is damaged, resulting in abnormal casing pressure, and the detection is ended;

[0020] Conversely, if the pressure is stable during forward water injection after a ball is dropped into the casing pressure abnormal monitoring device, and the casing pressure remains unchanged during forward water injection before the ball is dropped into the casing pressure abnormal monitoring device, and at the same time, the sealing rubber cylinder of the monitoring string has good performance, it indicates that the sealing rubber cylinder of the packer is intact, and proceed to step 5;

[0021] Step 5, check the casing. If the casing pressure decreases during reverse water injection, and at the same time, it has been determined that the tubing is not damaged, and the sealing rubber cylinders of the packer and the monitoring string are both intact, it indicates that the casing is damaged, resulting in abnormal casing pressure.

[0022] The beneficial effects of the present invention are as follows: By using different water injection methods, the present invention uses the built-in pressure gauge to monitor the change law of the casing pressure, and judges factors such as the damage of the casing and tubing that may cause abnormal casing pressure, and the sealing performance of the packer and the sealing module, which is beneficial to improving the workover efficiency and increasing the safety factor of the casing and wellhead equipment. Description of the Drawings

[0023] Figure 1 is the process diagram of the casing pressure monitoring string during normal stratified water injection;

[0024] Figure 2 is the process diagram of the casing pressure monitoring string during reverse water injection;

[0025] Figure 3 is the structure diagram of the casing pressure monitoring device;

[0026] Figure 4 is the cross-sectional view of the sealing test joint;

[0027] In the figure: 1 is the tubing, 2 is the blowout preventer, 3 is the wellhead cross, 4 is the casing, 5 is the casing pressure abnormal monitoring device, 6 is the sealing cylinder, 7 is the packer, 8 is the screen pipe, 9 is the perforated insert seal, 10 is the plug,

[0028] 5-1 is the ball dropping nipple, 5-2 is the steel ball, 5-3 is the shear pin, 5-4 is the ball seat, 5-5 is the upper pressure gauge nipple, 5-6 is the upper pressure gauge, 5-7 is the sealing test pressure gauge, 5-8 is the sealing test joint, 5-9 is the sealing module, 5-10 is the lower pressure gauge, 5-11 is the lower pressure gauge nipple.

[0029] For those of ordinary skill in the art, without creative efforts, other relevant drawings can be obtained based on the above drawings. Detailed Embodiments

[0030] The technical solutions of the present invention will be further described below through specific embodiments.

[0031] Such as Figure 1 And 2As shown in the figure, a string for monitoring abnormal casing pressure in a stratified water injection well includes a tubing 1, a wellhead cross 3, a casing 4, an abnormal casing pressure monitoring device 5, a screen pipe 8 and a plug 10. The wellhead cross 3 is installed at the wellhead. The casing 4 is arranged in the wellhead and is connected to the wellhead cross 3. The tubing 1 extends into the casing 4 from the wellhead. The abnormal casing pressure monitoring device 5 is arranged in the middle of the tubing 1. A sealing cylinder 6 is installed outside the abnormal casing pressure monitoring device 5. The packer 7 is connected to the sealing cylinder 6, thereby achieving the purpose of sealing the annulus between the tubing 1 and the casing 4. The tail end of the tubing 1 is successively provided with a perforated insert seal 9 and a plug 10 from top to bottom. The screen pipe 8 is installed at the tail end of the sealing cylinder 6. The annulus between the tubing 1 and the casing 4 is divided into two parts by the screen pipe 8, namely the annulus between the tubing 1 and the screen pipe 8 and the annulus between the screen pipe 8 and the casing 4;

[0032] As Figure 3 and 4As shown in the figure, the casing pressure abnormal monitoring device 5 includes a ball throwing nipple 5-1, an upper pressure gauge nipple 5-5, a seal test joint 5-8, and a lower pressure gauge nipple 5-11. The head end of the ball throwing nipple 5-1 is connected to the tubing 1. A shear pin hole is formed in the middle of the ball throwing nipple 5-1. The ball seat 5-4 is fixed in the ball throwing nipple 5-1 by a shear pin 5-3 arranged in the shear pin hole. The tail end of the ball throwing nipple 5-1 is connected to the head end of the upper pressure gauge nipple 5-5. An upper pressure gauge mounting platform is formed on the inner wall of the upper pressure gauge nipple 5-5. The upper pressure gauge mounting platform divides the upper pressure gauge nipple 5-5 into a structure with both ends open and non-connected in the middle. An upper pressure gauge measuring hole is formed on the side of the upper pressure gauge mounting platform. The upper pressure gauge 5-6 is mounted on the upper pressure gauge mounting platform and is connected to the upper pressure gauge measuring hole. The tail end of the upper pressure gauge nipple 5-5 is connected to the head end of the seal test joint 5-8. A seal test pressure gauge mounting platform is formed on the inner wall of the seal test joint 5-8. The seal test pressure gauge mounting platform divides the seal test joint 5-8 into a structure with both ends open and non-connected in the middle. A seal test pressure gauge measuring hole is formed on the side of the seal test pressure gauge mounting platform. The seal test pressure gauge 5-7 is mounted on the seal test pressure gauge mounting platform and is connected to the seal test pressure gauge measuring hole. The tail end of the seal test joint 5-8 is connected to the head end of the lower pressure gauge nipple 5-11. A lower pressure gauge mounting platform is formed on the inner wall of the lower pressure gauge nipple 5-11. The lower pressure gauge mounting platform divides the lower pressure gauge nipple 5-11 into a structure with both ends open and non-connected in the middle. A lower pressure gauge measuring hole is formed on the side of the lower pressure gauge mounting platform. The lower pressure gauge 5-10 is mounted on the lower pressure gauge mounting platform and is connected to the lower pressure gauge measuring hole. The tail end of the lower pressure gauge nipple 5-11 is connected to the tubing 1. And bridge channels are formed on the side walls of the upper pressure gauge nipple 5-5, the seal test joint 5-8, and the lower pressure gauge nipple 5-11, so as to achieve the purpose that when the fluid in the tubing 1 passes through the upper pressure gauge nipple 5-5, the seal test joint 5-8, and the lower pressure gauge nipple 5-11 in sequence from top to bottom, the fluid can flow normally.

[0033] Seal grooves are uniformly formed on the outer wall of the tail end of the upper pressure gauge nipple 5-5 and the middle outer wall of the seal test joint 5-8. A seal module 5-9 is arranged in the seal grooves. An annular seal cavity is formed among the seal module 5-9 of the upper pressure short nipple 5-5, the seal test short joint 5-8, the seal cylinder 6, and the seal module 5-9 of the seal test short joint 5-8. The pressure in the above annular seal cavity can be measured by the seal test pressure gauge 5-7.

[0034] A pressure relief hole is also formed on the side wall of the ball throwing nipple 5-1. The pressure relief hole is located above or below the shear pin hole.

[0035] A blowout preventer 2 is also arranged on the wellhead cross 3.

[0036] A packer is successively arranged from top to bottom in the annulus between the screen pipe 8 and the casing 4, so as to achieve the purpose of dividing the annulus between the screen pipe 8 and the casing 4 into non-connected water injection layers.

[0037] A monitoring method for the abnormal casing pressure of a stratified water injection well string is carried out according to the following steps:

[0038] Step 1, overall investigation: If the casing pressure remains stable and unchanged during reverse water injection, it indicates that the casing and the tubing are not damaged, and the sealing rubber cylinders of the packer and the monitoring string are in good condition, indicating that the casing pressure of this well is normal, and the detection is ended;

[0039] On the contrary, if the casing pressure cannot be stabilized during reverse water injection, it means that the tubing and the casing may be damaged, or the sealing rubber cylinders of the packer and the monitoring string are damaged, resulting in sealing failure, and enter Step 2;

[0040] Step 2, investigate the tubing. After throwing a ball into the abnormal casing pressure monitoring device and injecting water forward, if the playback tubing pressure data is stable, it indicates that the tubing is in good condition, and enter Step 3;

[0041] If the playback tubing pressure data is unstable, it indicates that the tubing is damaged, resulting in abnormal casing pressure, and the detection is ended;

[0042] Step 3, investigate the sealing module. If the playback data of the seal test pressure gauge does not change during forward water injection and reverse water injection, it indicates that the sealing rubber cylinder of the monitoring string has good performance, and enter Step 4;

[0043] If the playback data of the seal test pressure gauge is unstable, it indicates that the sealing rubber cylinder of the monitoring string is damaged, resulting in abnormal casing pressure, and the detection is ended;

[0044] Step 4, investigate the packer. If the pressure is stable when injecting water forward after throwing a ball into the abnormal casing pressure monitoring device, and the casing pressure increases when injecting water forward before throwing a ball into the abnormal casing pressure monitoring device, and at the same time, the sealing rubber cylinder of the monitoring string has good performance, it indicates that the sealing rubber cylinder of the packer is damaged, resulting in abnormal casing pressure, and the detection is ended;

[0045] On the contrary, if the pressure is stable when injecting water forward after throwing a ball into the abnormal casing pressure monitoring device, and the casing pressure remains unchanged when injecting water forward before throwing a ball into the abnormal casing pressure monitoring device, and at the same time, the sealing rubber cylinder of the monitoring string has good performance, it indicates that the sealing rubber cylinder of the packer is in good condition, and enter Step 5;

[0046] Step 5, investigate the casing. If the casing pressure decreases during reverse water injection, and at the same time, it has been determined that the tubing is not damaged, and the sealing rubber cylinders of the packer and the monitoring string are in good condition, it indicates that the casing is damaged, resulting in abnormal casing pressure.

[0047] The principle of this detection method is as follows:

[0048] At a certain temperature, the property that the volume of a fluid decreases as the pressure increases is called the compressibility of the fluid. The magnitude of compressibility is represented by the coefficient of volume compressibility k, and its physical meaning is the relative change rate of volume caused by a unit change in pressure, that is

[0049]

[0050] where k is the coefficient of volume compressibility of the fluid, 1 / Pa;

[0051] V is the volume of the fluid, m 3 ;

[0052] ΔV is the change in the volume of the fluid, m 3 ;

[0053] Δp is the change in the fluid pressure, Pa.

[0054] Since the pressure increases and the volume decreases, the changes in ΔV and Δp are in opposite trends. And it can be seen from the expression of k that when the pressure changes are the same, the larger the relative change rate of volume ΔV / V, the larger the value of k, that is, the easier the fluid is to be compressed, while the fluid with a small k value is not easily compressed. Therefore, the value of k marks the magnitude of the compressibility of the fluid.

[0055] The volume compressibility is very small. When the pressure is in the range of 0.1 - 50 MPa and the temperature is in the range of 0 - 200 °C, the volume compressibility of water is about one in twenty thousand. However, if gas is mixed into the oil, the compressibility will increase significantly. Usually, when there is no air mixed into the oil, K = (1.4 - 2.0)×10 9 Pa. When 1% of gas is mixed into the oil, the value of K drops to about 5% of the original; when 5% of gas is mixed into the oil, the value of K drops to about 1% of the original. Therefore, for the relatively large volume of the oil casing in petroleum engineering and when seepage occurs during oil well production, the influence of the compressibility of the fluid must be considered.

[0056] It can be seen from the above formula that during normal water injection, when the formation fluid passes through the damaged tubing and the packer and seal module fail, resulting in micro-seepage, the formation fluid will slowly seep into the casing, causing the casing pressure to rise slowly. Therefore, it is necessary to monitor the slow change of the casing pressure for a period of time, and based on the monitored pressure and time data, initially judge the seepage flow rate.

[0057] A construction method for a monitoring string of abnormal casing pressure in a stratified water injection well is carried out according to the following steps:

[0058] Step 1, after the monitoring string is lowered in place, after the mud pump is connected to the casing cross, pressure test the blowout preventer that seals the annulus between the oil and casing on the ground to ensure good sealing performance;

[0059] Step 2: Inject water in the annulus between the casing and the tubing in the reverse direction. After pressurizing to a certain pressure, stop the pump and hold the pressure for a period of time. Observe the change in pump pressure and check whether there is any liquid flowing back from the tubing.

[0060] Step 3: Reverse the process flow. Inject water in the tubing in the forward direction. After pressurizing to a certain pressure, stop the pump and hold the pressure for a period of time. Observe the change in pump pressure and check the change in casing pressure.

[0061] Step 4: After putting the ball in, inject water in the tubing in the forward direction again. After pressurizing to a certain pressure, stop the pump and hold the pressure for a period of time. Observe the change in pump pressure.

[0062] Step 5: Pull out the monitoring string, playback the pressure gauge data, analyze the pressure change, infer the leakage point and the leakage volume, and finally predict the change trend of the casing pressure.

[0063] For ease of explanation, in the embodiments, spatial relative terms such as "upper", "lower", "left", "right", etc. are used to describe the relationship of one element or feature shown in the figure relative to another element or feature. It should be understood that, in addition to the orientations shown in the figure, the spatial terms are intended to include different orientations during the use or operation of the device. For example, if the device in the figure is inverted, the element described as being "below" other elements or features will be positioned "above" the other elements or features. Therefore, the exemplary term "lower" can include both the upper and lower orientations. The device can be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here can be interpreted accordingly.

[0064] Moreover, relational terms such as "first" and "second" are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components.

[0065] The above has described the present invention in detail, but the content described is only the preferred embodiment of the present invention and cannot be considered as defining the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. Casing pressure abnormal monitoring device, Characterized in that: It includes a ball injection nipple, an upper pressure gauge nipple, a seal test joint and a lower pressure gauge nipple. The head end of the ball injection nipple is connected to the tubing. A shear pin hole is formed in the middle of the ball injection nipple, and a ball seat is fixed in the ball injection nipple by using a shear pin arranged in the shear pin hole; The tail end of the ball injection nipple is connected to the head end of the upper pressure gauge nipple. An upper pressure gauge mounting platform is formed on the inner wall of the upper pressure gauge nipple. The upper pressure gauge mounting platform divides the upper pressure gauge nipple into a structure with both ends open and non-connected in the middle. An upper pressure gauge measuring hole is formed on the side of the upper pressure gauge mounting platform. The upper pressure gauge is mounted on the upper pressure gauge mounting platform and is connected to the upper pressure gauge measuring hole; The tail end of the upper pressure gauge nipple is connected to the head end of the seal test joint. A seal test pressure gauge mounting platform is formed on the inner wall of the seal test joint. The seal test pressure gauge mounting platform divides the seal test joint into a structure with both ends open and non-connected in the middle. A seal test pressure gauge measuring hole is formed on the side of the seal test pressure gauge mounting platform. The seal test pressure gauge is mounted on the seal test pressure gauge mounting platform and is connected to the seal test pressure gauge measuring hole; The tail end of the seal test joint is connected to the head end of the lower pressure gauge nipple. A lower pressure gauge mounting platform is formed on the inner wall of the lower pressure gauge nipple. The lower pressure gauge mounting platform divides the lower pressure gauge nipple into a structure with both ends open and non-connected in the middle. A lower pressure gauge measuring hole is formed on the side of the lower pressure gauge mounting platform. The lower pressure gauge is mounted on the lower pressure gauge mounting platform and is connected to the lower pressure gauge measuring hole; The tail end of the lower pressure gauge nipple is connected to the tubing, and bridge channels are formed on the side walls of the upper pressure gauge nipple, the seal test joint and the lower pressure gauge nipple.

2. The casing pressure abnormal monitoring device according to claim 1, Characterized in that: Seal grooves are evenly formed on the outer wall of the tail end of the upper pressure gauge nipple and the middle outer wall of the seal test joint. A seal module is arranged in the seal grooves. An annular seal cavity is formed among the seal modules of the upper pressure gauge short section, the seal test short section, the seal cylinder and the seal test short section. The pressure in the above annular seal cavity can be measured by using the seal test pressure gauge.

3. The casing pressure abnormal monitoring device according to claim 1, Characterized in that: A pressure relief hole is also opened on the side wall of the ball injection nipple, and the pressure relief hole is located above or below the shear pin hole.

4. A layered injection well casing pressure abnormal monitoring string using the casing pressure abnormal monitoring device according to any one of claims 1-3, Characterized in that: It includes a tubing string, a wellhead four-way, a casing, an annulus pressure abnormal monitoring device, a screen pipe and a plug. The wellhead four-way is installed at the wellhead. The casing is arranged in the wellhead and is connected to the wellhead four-way. The tubing string extends into the casing from the wellhead. The annulus pressure abnormal monitoring device is arranged in the middle of the tubing string. A sealing cylinder is installed outside the annulus pressure abnormal monitoring device. A packer is connected to the sealing cylinder, thereby achieving the purpose of sealing the annulus between the tubing string and the casing. The tail end of the tubing string is sequentially provided with a perforated insert seal and the plug from top to bottom. The screen pipe is installed at the tail end of the sealing cylinder. The annulus between the tubing string and the casing is divided into two parts by the screen pipe, namely, the annulus between the tubing string and the screen pipe and the annulus between the screen pipe and the casing.

5. The tubing string for monitoring annulus pressure abnormal in a layered water injection well according to claim 4, characterized in that: a blowout preventer is further arranged on the wellhead four-way.

6. The tubing string for monitoring annulus pressure abnormal in a layered water injection well according to claim 4, characterized in that: packers are sequentially arranged from top to bottom in the annulus between the screen pipe and the casing to achieve the purpose of dividing the annulus between the screen pipe and the casing into non-connected water injection layers.

7. The detection method of the tubing string for monitoring annulus pressure abnormal in a layered water injection well according to any one of claims 4-6, characterized in that: it is carried out according to the following steps: Step 1, overall investigation: If the annulus pressure remains stable and unchanged during reverse injection, it indicates that the casing and the tubing string are not damaged, and the rubber seals of the packer and the monitoring tubing string are intact, indicating that the annulus pressure of this well is normal, and the detection is ended; On the contrary, if the annulus pressure cannot be stabilized during reverse injection, it means that the tubing string and the casing may be damaged, or the rubber seals of the packer and the monitoring tubing string are damaged, resulting in seal failure, and enter Step 2; Step 2, investigate the tubing string. After throwing a ball into the annulus pressure abnormal monitoring device and injecting water forward, if the playback tubing pressure data is stable, it indicates that the tubing string is intact, and enter Step 3; If the playback tubing pressure data is unstable, it indicates that the tubing string is damaged, resulting in abnormal annulus pressure, and the detection is ended; Step 3, investigate the sealing module. If the playback data of the seal test pressure gauge does not change during forward injection and reverse injection, it indicates that the rubber seal of the monitoring tubing string has good performance, and enter Step 4; If the playback data of the seal test pressure gauge is unstable, it indicates that the rubber seal of the monitoring tubing string is damaged, resulting in abnormal annulus pressure, and the detection is ended; Step 4, investigate the packer. If the pressure is stable when injecting water forward after throwing a ball into the annulus pressure abnormal monitoring device, and the casing pressure increases when injecting water forward before throwing a ball into the annulus pressure abnormal monitoring device, and at the same time, the rubber seal of the monitoring tubing string has good performance, it means that the rubber seal of the packer is damaged, resulting in abnormal annulus pressure, and the detection is ended; On the contrary, if the pressure is stable when injecting water forward after throwing a ball into the annulus pressure abnormal monitoring device, and the casing pressure remains unchanged when injecting water forward before throwing a ball into the annulus pressure abnormal monitoring device, and at the same time, the rubber seal of the monitoring tubing string has good performance, it means that the rubber seal of the packer is intact, and enter Step 5; Step 5, check the casing. If the casing pressure decreases during reverse water injection, and at the same time, it has been determined that the tubing is not damaged and the rubber seals of the packer and the monitoring string are intact, it indicates that the abnormal casing pressure is caused by damaged casing.

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