Gas well effusion real-time monitoring device and method based on modular digital oil pipe

Abstract

The invention relates to the technical field of natural gas extraction drainage gas production, in particular to a gas well accumulated liquid real-time monitoring device and method based on a modular digital oil pipe, which comprises a digital oil pipe docking mechanism, a single-point pressure monitoring pipe column, a bottom hole pressure monitoring pipe column, a wellhead gas production tree cable penetrating device and a ground data center, the digital oil pipe butt joint mechanism, the single-point pressure monitoring pipe column, the bottom hole pressure monitoring pipe column and the wellhead gas production tree cable penetrating device are connected through pipe threads. All components are installed on the oil pipes, the digital oil pipes are in butt joint, transmission of electric power and signals can be completed, operation is easy, a traditional oil pipe column structure is not changed, a special transmission connector does not need to be additionally installed between pipe columns for signal and electric power transmission, the strength of the whole pipe column is not changed, and when the two digital oil pipes are in butt joint, operation is convenient. Only the fixed connecting device and the movable connecting device need to be axially and circumferentially positioned.

Description

Technical Field

[0001] The invention relates to the technical field of natural gas exploitation, drainage and gas production, and in particular to a gas well liquid accumulation real-time monitoring device and method based on modular digital oil pipes. Background Art

[0002] Liquid accumulation in gas wells is usually caused by the decrease in formation pressure and the decrease in gas well productivity, which leads to an increase in the wellbore temperature gradient, causing some components of natural gas to condense in the wellbore to form condensate. At the same time, the insufficient gas reservoir energy makes the gas production of the gas well insufficient to carry out these condensates, causing them to fall back to the bottom of the well and accumulate. In addition, during the development of natural gas, edge water and bottom water are produced, causing formation water to enter the wellbore with natural gas and accumulate at the bottom of the well. These factors work together to cause liquid accumulation in the wellbore of the gas well, affecting the normal production and efficiency of the gas well. Not only will it reduce the production of the gas well, it may also cause gas well flooding in serious cases. Therefore, various drainage gas production measures have been born, such as gas lift, plunger, foam drainage gas production, and optimal pipe column drainage gas production. In recent years, the amount of downhole liquid accumulation has been of key significance for drainage gas production, especially in the Sichuan and Chongqing regions, where drainage gas production is a common problem in the late stage of production of shale gas wells, but there is still a lack of direct measurement methods, which affects the integrity and accuracy of production data.

[0003] At present, there are many methods for judging liquid accumulation in gas wells. Except for the pressure gradient method and the echo sounder monitoring method, other methods such as the wellhead casing pressure judgment method and the production experience judgment method are not direct measurement methods, and the accuracy of the calculated results cannot be guaranteed. The pressure gradient method uses the steel wire and the sensor spacing lowering device for measurement. It is suitable for short-term steel wire rope downhole monitoring, but not suitable for situations where there are downhole tools in the pipe column (such as plunger drainage gas production), and it affects normal production and is not suitable for long-term downhole monitoring. The echo sounder monitoring method has a lower measurement accuracy than the pressure gradient method and is affected by downhole cleaning conditions, environmental noise, etc. At the same time, the signal needs to be analyzed and processed, which is technically difficult. Accurately calculating the amount of liquid accumulated at the bottom of a liquid-accumulated gas well is an unavoidable problem that must be solved. Therefore, a new direct method is needed to monitor the height of the liquid accumulated at the bottom of the well in real time.

[0004] Traditional electronic downhole pressure gauges have problems such as electromagnetic interference and insufficient tolerance to high temperature and high pressure underground, and a pressure gauge often has multiple wires. Fiber optic sensors are resistant to electromagnetic interference, high temperature and high pressure, and do not require electricity. In particular, they can multiplex multiple channels, so that multiple signal transmissions can be achieved with just one optical fiber. They are very suitable for the use of multi-sensor series pressure monitoring in oil wells. To this end, we have introduced a real-time monitoring device and method for gas well liquid accumulation based on modular digital oil pipes. Summary of the invention

[0005] The object of the present invention is to provide a device and method for real-time monitoring of liquid accumulation in gas wells based on modular digital oil pipes, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A real-time monitoring device for liquid accumulation in a gas well based on modular digital oil pipes comprises a digital oil pipe docking mechanism, a single-point pressure monitoring pipe string, a bottom hole pressure monitoring pipe string, a wellhead gas tree cable crossing device, and a ground data center. The digital oil pipe docking mechanism, the single-point pressure monitoring pipe string, the bottom hole pressure monitoring pipe string, and the wellhead gas tree cable crossing device are connected by pipe threads.

[0008] Preferably, the digital oil pipe docking mechanism comprises two groups of digital oil pipes arranged vertically, and the two groups of digital oil pipes are movably connected to each other.

[0009] Preferably, the digital oil pipe includes a traditional oil pipe, a fixed connection device, a movable connection device, a sealing gasket, a cable protective shell, a locker 1, a locker 2, an armored cable, an armored optical cable, and a cable protector. The traditional oil pipe is connected to the fixed connection device through a pipe thread, and the movable connection device, the sealing gasket, the cable protective shell, the locker 1, and the locker 2 are bound to the lower side of the traditional oil pipe through a large rope. After the two groups of traditional oil pipes are spliced, they are untied to complete the docking of the fixed connection device and the movable connection device;

[0010] The fixed connection device is located on the upper side of the traditional oil pipe, the movable connection device, the sealing gasket, the cable protection shell, the first locker, and the second locker are located on the lower side of the traditional oil pipe, the armored optical cable and the armored electrical cable are fixed to the outer side of the traditional oil pipe through the annular groove on the inner side of the cable protector, and the cable protector is provided with a pair of bosses with holes on the opposite side of the annular groove, and there is a gap between the pair of bosses, and the cable protector can be attached to the traditional oil pipe by tightening the bolts to reduce the gap distance, and the cable protector can prevent the armored optical cable and the armored electrical cable from collision and twisting;

[0011] The transmission of power and signals is achieved through the cooperation of the fixed connection device of the digital oil pipe on the lower side and the sealing gasket, movable connection device, cable protective shell, locker 1 and locker 2 of the digital oil pipe on the upper side. The fixed connection device cooperates with the sealing gasket, movable connection device and cable protective shell through circumferential arc grooves and arc bosses to achieve circumferential positioning. The upper side of the fixed connection device is provided with an external thread, and the locker 1 and locker 2 are provided with internal threads. The axial positioning of the fixed connection device and the sealing gasket, movable connection device and cable protective shell is achieved through threaded connection.

[0012] Preferably, the fixed connection device includes, in addition to the armored cable and the armored optical cable, a connecting collar, a power transmission female head, an annular sealing body, a second hollow stud, and an optical fiber collimator. The connecting collar is provided with a cylindrical boss and has three holes. The large holes on the left and right sides are used for installing power transmission components, and the small hole in the middle is used for installing optical fiber signal transmission components. The large holes on the left and right sides are provided with a power transmission female head, an annular sealing body, a second hollow stud, and an armored cable. The power transmission female head is connected to the armored cable as a whole by welding, and is bonded to the upper end face of the corresponding large hole of the connecting collar by glue. The annular sealing body The second hollow stud is sequentially installed into the hole from the lower side of the large hole of the connecting coupling, and is connected to the internal thread of the large hole through the thread of the second hollow stud. The second hollow stud produces an extrusion effect on the annular sealing body, so that the annular sealing body fills the inner cavity of the large hole of the connecting coupling to achieve a sealing effect. The middle small hole is provided with a fiber optic collimator, an annular sealing body, a second hollow stud, and an armored optical cable. The fiber optic collimator is bonded to the upper end face of the middle small hole of the connecting coupling by glue and is welded to the armored optical cable as a whole. The connection and sealing method of the annular sealing body and the second hollow stud is the same as that of the device in the large hole of the connecting coupling.

[0013] Preferably, the power transmission female head comprises a spring, a spring metal shell, a first insulating shell, and a female head. The spring, the spring metal shell, and the female head are all installed in the first insulating shell. The spring metal shell is bonded to the first insulating shell as a whole. One side end face of the spring is bonded to the end face of the spring metal shell as a whole. The spring and the female head are connected as a whole by bonding. The spring and the female head are sequentially installed in the spring metal shell.

[0014] Preferably, the movable connection device includes, in addition to the armored cable, the armored optical cable, the annular sealing body, the second hollow stud, and the optical fiber collimator, an upper connector, a power transmission male head, and the power transmission male head is fixed in the same way as the power transmission female head.

[0015] Preferably, the power transmission male connector comprises a male connector and a second insulating shell, the male connector and the second insulating shell are bonded as a whole, and the lower end surface of the second insulating shell is bonded to the lower end surface of the upper connector to fix the male connector in the upper connector, and the upper end of the female connector has a conical surface so that the female connector fits with the male connector after being inserted, and when the spring is not subjected to force, the female connector contacts the spring metal shell, and the female connector has a step surface for limiting the compression distance of the spring, and the male connector has a conical surface with the same inclination as the female connector, so that the female connector fits with the male connector after being inserted into the male connector.

[0016] Preferably, the double locking of the locker 1 and the locker 2 achieves an anti-loosening effect of the threaded connection, and can simultaneously compress the sealing gasket to achieve an end face sealing effect, thereby achieving complete sealing of the power transmission male head, the power transmission female head and the optical fiber collimator. The power transmission male head and the power transmission female head achieve complete contact when the locker 1 is locked, and the spring in the power transmission female head is in a compressed position, so that the female head fits tightly with the male head in the power transmission male head, thereby achieving stable and reliable power transmission. The optical fiber collimator in the fixed connection device and the movable connection device reaches an effective optical signal coupling distance when the locker 1 is locked, thereby achieving optical signal transmission. The cable protective shell is used to protect the cable and avoid direct contact between the cable and the casing wall.

[0017] Preferably, the single-point pressure monitoring column includes, in addition to all components of the digital oil pipe, a fiber optic Bragg grating sensor, a pressure gauge holder, and a pressing piece. The fixed connection device, the pressure gauge holder, and the traditional oil pipe are connected by pipe threads. The fiber optic Bragg grating sensor is located in a circular groove on the pressure gauge holder, and the upper and lower sides of the fiber optic Bragg grating sensor are blocked by the pressing piece. Threaded holes are provided on the pressing piece and the pressure gauge holder, and the pressing piece is fixed by screws to fix the fiber optic Bragg grating sensor.

[0018] Preferably, the bottom hole pressure monitoring string includes, in addition to conventional oil pipes, fixed connection devices, armored cables, armored optical cables, and cable protectors, three groups of fiber optic Bragg grating sensors, bottom hole pressure gauge holders, tubing shoes, and pressing plates. The fixed connection device, conventional oil pipes, bottom hole pressure gauge holders, and tubing shoes are connected via pipe threads, and the armored cables, armored optical cables, and conventional oil pipes are fixed to the outer wall of conventional oil pipes via cable protectors. The three groups of fiber optic Bragg grating sensors are located in the oblong grooves on the bottom hole pressure gauge holders, and the upper and lower sides of the fiber optic Bragg grating sensors are blocked by pressing plates. Threaded holes are provided on the pressing plates and the bottom hole pressure gauge holders, and the pressing plates are completely fixed by screws to achieve complete fixation of the fiber optic Bragg grating sensors.

[0019] Preferably, the cable crossing device of the wellhead gas production tree includes, in addition to the traditional oil pipe, an oil pipe spool, an upper flange, a manual gate, an electric gate, a T-flange, a crossing flange, and a gas leakage detection device. The oil pipe hanger has a conical surface, and the oil pipe spool also has a conical surface. The traditional oil pipe is connected to the oil pipe hanger by a pipe thread. The oil pipe hanger cooperates with the conical surface of the oil pipe spool through its conical surface to suspend the traditional oil pipe and bear the weight of the traditional oil pipe. The oil pipe spool, manual gate, electric gate, T-flange and crossing flange are connected by flanges. The crossing flange is connected to the gas leakage detection device by threads. The crossing flange is used for armored cables and armored optical cables to pass from the well to the ground.

[0020] Preferably, the crossing flange includes a crossing flange body, a sealing body, a V-shaped ring, and a first hollow stud. The crossing flange body has a first hole, a second hole, and a third hole, which are respectively allocated to the wellhead crossings of two groups of armored cables and armored optical cables. The armored optical cable passes through the sealing body, the V-shaped ring, and the inner hole of the first hollow stud in turn, and the sealing body, the V-shaped ring, and the first hollow stud are sequentially installed in the third hole of the crossing flange body. The first hollow stud is connected to the third hole of the crossing flange body by threads. A small hole with a reduced diameter is provided in the third hole of the crossing flange body. Under the tightening action of the generated end face and the first hollow stud, the sealing body in the hole expands and seals, and clamps the armored optical cable to achieve the crossing of the armored optical cable. The crossing method of the armored cable is the same as that of the armored optical cable.

[0021] Preferably, the gas leakage detection device includes a gas detection device body, a gas detection device shell, and a top cover. The gas detection device body is used to detect natural gas leakage. The gas detection device shell is a five-sided cube, wherein two side surfaces have long openings for the cables to pass through. The top cover directly covers the upper end of the gas detection device shell and can be fixed by relying on gravity and the cooperation of multiple faces. The top cover has long openings for the cables to pass through. The gas detection device shell and the top cover form a relatively sealed space for the gas detection device body. The gas detection device body is installed on the upper side of the gas detection device shell. The density of natural gas is higher than that of air and is gathered on the upper side of the gas detection device shell. When natural gas leaks, the gas detection device body will alarm and upload data to the control center and the cloud to notify users of the situation. When gas leaks, the gas detection device body will be linked with the electric gate to control the electric gate to close and block gas leakage.

[0022] Preferably, the ground data center includes a fiber grating demodulator, a light detector, a light source, an armored optical cable, a power supply, an armored cable, and a computer. The fiber grating demodulator, the light detector, and the light source are connected via an armored optical cable, and the light source, the power supply, and the computer are connected via an armored cable. The light detector is used to detect the reflected light signal and convert it into an electrical signal. The fiber grating demodulator is used to analyze the wavelength change of the reflected light and convert it into a physical signal. The computer calculates the depth of the liquid accumulation in the well through a built-in program algorithm.

[0023] In addition, in order to achieve the above-mentioned purpose, the present invention also provides a method for real-time monitoring of liquid accumulation in gas wells based on modular digital oil pipes, which is used in the above-mentioned real-time monitoring device for liquid accumulation in gas wells, including a downhole signal transmission method and a gas well liquid accumulation calculation method;

[0024] The downhole signal transmission method is:

[0025] The light source is emitted by the wellhead laser, and the optical signal is connected between digital oil pipes through the optical fiber collimator of the digital oil pipe. N fiber Bragg grating sensors use n Bragg gratings with different reflection wavelengths to be arranged along a single optical fiber and are placed at n different monitoring positions of the traditional oil pipe. When the physical quantity to be measured at these positions changes, the wavelength coded signal reflected back by each Bragg grating carries the change information of the physical quantity to be measured at the corresponding position. The change of the physical quantity to be measured can be obtained by decoding through the fiber Bragg grating modulator at the receiving end and analyzing the Bragg wavelength displacement, thereby realizing real-time and online monitoring of multiple monitoring positions by one optical fiber line.

[0026] The gas well liquid accumulation monitoring method mainly comprises the following steps:

[0027] Step 1: Data acquisition, using digital tubing to transmit power and signals, a pressure gauge holder is arranged every 300m, and a bottom hole pressure gauge holder with three fiber grating sensors is arranged at the bottom hole tubing shoe to measure the density of the liquid over a short distance, so as to increase the number of pressure measurement points, obtain the pressure data arranged along the well depth, and obtain the depth of each pressure gauge holder, casing diameter, tubing diameter, liquid density, gas density, wellhead tubing pressure and other data;

[0028] Step 2: According to the relationship between the depth of liquid accumulation and the position of the bottom hole sensor group, the liquid accumulation situation is divided into three situations according to the judgment conditions: above the bottom hole pressure gauge support tube, between the bottom hole pressure gauge support tube, and below the bottom hole pressure gauge support tube;

[0029] Step 3: Combined with the pressure monitoring data value, when the pressure gradient monitored by the three fiber Bragg grating pressure sensors on the bottom hole pressure gauge holder is greater than 0.2MPa / 100m, and the pressure gradients between adjacent fiber Bragg grating sensors are equal (ΔP1 / 100=ΔP2 / 100) and the data value is relatively stable, it is determined that the liquid accumulation depth is above the bottom hole pressure gauge holder. According to the multi-point pressure data tested, the pressure trend lines of the gas phase and the liquid phase are fitted, and the intersection of the two trend lines is the liquid accumulation depth in the casing annulus;

[0030] Step 4: Combined with the pressure monitoring data value, when the pressure gradient monitored by the fiber Bragg grating pressure sensor on the bottom hole pressure gauge holder is greater than 0.2MPa / 100m, but the pressure gradients between adjacent fiber Bragg grating sensors are unequal and unstable, it is determined that the liquid accumulation depth is located between the bottom hole pressure gauge holders. Since the length of this section of the bottom hole pressure gauge holder is short, the amount of liquid accumulation is small, and the middle depth of the bottom hole pressure gauge holder is considered to be the liquid accumulation depth;

[0031] Step 5: Combined with the pressure monitoring data value, when the pressure gradient monitored by the two fiber Bragg grating pressure sensors at the bottom of the bottom hole pressure gauge holder is less than 0.2MPa / 100m, it is determined that the depth of the liquid accumulation is below the bottom hole pressure gauge holder, and the depth of the liquid accumulation is calculated according to the pressure change of the fiber Bragg grating sensor at the bottom and the liquid density described in step 1;

[0032] Step 6: Calculate the depth of liquid accumulation in the tubing based on the depth of liquid accumulation in the casing annulus and the real-time measured density of liquid accumulation.

[0033] A real-time monitoring method for liquid accumulation in gas wells based on modular digital oil pipes, wherein the detailed calculation steps of liquid accumulation in step 3 are as follows:

[0034] The pressure gradient inflection point was determined by using ΔP / 100>0.2MPa / 100m as the judgment condition, and the pressure data were divided into two groups according to the inflection point;

[0035] The depth of each sensor from the wellhead to the well is set to x1, x2....x n , m, pressure data is set to y1, y2...y n , MPa;

[0036] The gas-liquid two-phase pressure trend lines are set as:

[0037] y=a1x+b1

[0038] y=a2x+b2

[0039] Where a1 and b1 are the parameters of the gas phase trend line equation, and a2 and b2 are the parameters of the liquid phase trend line equation;

[0040] The parameter calculation formula is:

[0041]

[0042] The depth of the effusion is:

[0043]

[0044] Where x0 is the depth of effusion, m.

[0045] The calculation of the liquid accumulation depth in step 5 includes: the liquid accumulation depth changes from above the lowermost fiber Bragg grating sensor to below the lowermost fiber Bragg grating sensor, and the liquid accumulation depth is below the lowermost fiber Bragg grating sensor;

[0046] When the depth of the accumulated liquid changes from above the lowest fiber grating sensor to below the lowest fiber grating sensor, the calculation method is:

[0047]

[0048] Where h 液Indicates the depth of liquid accumulation in the casing, m; H0 indicates the depth of the lowest fiber Bragg grating sensor, m; P2 indicates the latest pressure value measured by the lowest fiber Bragg grating sensor, MPa; P1 indicates the last pressure value measured by the lowest fiber Bragg grating sensor, MPa; ρ 气 Indicates the measured gas density, kg / m 3 ; g represents the acceleration due to gravity, m / s 2 ; A represents the amplification factor, which is ρ 液 / ρ 气 ;

[0049] When the liquid accumulation depth is below the lowest fiber grating sensor, the calculation method is:

[0050]

[0051] Where h0 represents the depth of effusion at the last measurement;

[0052] The calculation method in step six is:

[0053]

[0054] Where h 液 Indicates the depth of liquid accumulation in the oil pipe, m; P 井底 Indicates the actual pressure measured by the fiber grating sensor at the bottom, MPa; P 井口 Indicates the measured pressure in the wellhead tubing, MPa; ρ 气 Indicates the gas density in the oil pipe measured at the wellhead, kg / m 3 ρ 液 Indicates the measured liquid density underground, kg / m 3 ; g represents the acceleration due to gravity, m / s 2 ; H represents the depth of the bottom fiber Bragg grating sensor, m.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. Install all components on the oil pipe, and complete the docking of the digital oil pipe to complete the transmission of power and signals, which is easy to operate.

[0057] 2. This device does not change the structure of the traditional oil pipe string. The transmission of signals and power does not require the installation of additional special transmission joints between the pipe strings, and the overall strength of the pipe string remains unchanged.

[0058] 3. When two digital oil pipes are butt-jointed, it is only necessary to position the fixed connection device and the movable connection device axially and circumferentially to achieve the butt-jointing of the power transmission female connector, the power transmission male connector, and the optical fiber collimator in the digital oil pipe, thereby realizing the transmission of power and signals. The operation is simple and does not require other connector plug-in operations.

[0059] 4. There is a spring inside the power transmission female head, and the contact surfaces of the male and female heads have the same taper. After the power is connected, the spring is in a compressed state, making the male and female heads fit tightly.

[0060] 5. Use fiber optic collimator to transmit optical signals and realize contactless optical signal transmission.

[0061] 6. Thanks to the modular design, armored optical cables and armored electrical cables bear less cable tension and reduce the chance of cable twisting and entanglement, increasing the service life and reliability of underground cables at vertical distances of up to several thousand meters and high temperatures and pressures.

[0062] 7. The wellhead crossing flange is installed on the side pipe of the tubing spool. When in use, there is no need to change the original gas tree structure. It is easy to install and can be installed vertically or horizontally. The crossing flange can be connected through the flange connection.

[0063] 8. The wellhead sealing flange has good safety. A gas leakage monitoring device is installed on the upper side of the flange and is equipped with a corresponding gas monitoring box. When the wellhead sealing flange fails, monitoring and alarm are carried out. At the same time, an electric valve is equipped to prevent gas leakage. At the same time, the electric valve is behind the manual gate to facilitate the inspection and maintenance of the leakage point of the device at the wellhead.

[0064] 9. Use optical fiber for signal transmission, with higher transmission rate and more stable.

[0065] 10. Using fiber grating sensors, multi-sensor signal transmission only requires one fiber channel, reducing the number of signal lines used.

[0066] 11. The device does not occupy the space inside the oil pipe and is suitable for almost all drainage and gas production processes.

[0067] 12. The system monitors the pressure at multiple points in the well in real time, without using theoretical models to calculate the depth of liquid accumulation, making the calculation result more accurate.

[0068] 13. It can monitor the accumulated liquid in the gas well in real time for a long time, making the depth of the accumulated liquid in the well transparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0070] Figure 2 This is a schematic diagram of a cable crossing device for a wellhead gas tree of the present invention;

[0071] Figure 3 It is a schematic diagram of a through flange in a cable through device for a wellhead gas tree of the present invention;

[0072] Figure 4It is a schematic diagram of a gas leakage detection device in a cable crossing device of a wellhead gas tree of the present invention;

[0073] Figure 5 This is a schematic diagram of the digital oil pipe structure of the present invention;

[0074] Figure 6 This is a schematic diagram of the installation of the digital oil pipe collimator of the present invention;

[0075] Figure 7 This is a schematic diagram of the structure and installation of the female power transmission connector in the digital oil pipe of the present invention;

[0076] Figure 8 This is a schematic diagram of the structure and installation of the male connector for power transmission in the digital oil pipe of the present invention;

[0077] Fig. 9 This is a schematic diagram of the fiber optic collimator docking when the digital oil pipes of the present invention are docked;

[0078] Fig.10 It is a schematic diagram of the connection of the conductive device when the digital oil pipes of the present invention are connected;

[0079] Fig.11 It is a schematic diagram of circumferential positioning when the digital oil pipes of the present invention are connected;

[0080] Fig.12 This is a schematic diagram of the structure of a single-point pressure monitoring column of the present invention;

[0081] Fig.13 This is a schematic diagram of the structure of the bottom hole pressure monitoring string of the present invention;

[0082] Fig.14 It is a classification diagram of effusion situation of the method of the present invention;

[0083] Fig.15 This is a logic diagram for calculating the depth of fluid accumulation in the method of the present invention.

[0084] In the figure: 1. Cable crossing device for wellhead gas tree; 101. Upper flange; 102. Tubing hanger; 103. Tubing spool; 104. Manual gate; 105. Electric gate; 106. T-shaped flange; 107. Crossing flange; 1071. Crossing flange body; 1072. Sealing body; 1073. V-shaped ring; 1074. First hollow stud; 108. Gas leakage detection device; 1081. Gas detection device housing; 1082. Gas detection device body; 1083. Top cover; 2. Single-point pressure monitoring string; 201. Pressure gauge holder; 202. Pressing piece; 203. Fiber Bragg grating sensor; 3. Digital tubing; 301. Fixed Connecting device; 302, conventional oil pipe; 303, cable protector; 304, armored cable; 305, armored optical cable; 306, locker 1; 307, cable protection shell; 308, movable connecting device; 309, sealing gasket; 3011, connecting coupling; 3012, optical fiber collimator; 3013, annular sealing body; 3014, second hollow stud; 3015, female head; 3016, first insulating shell; 3017, spring metal shell; 3018, spring; 3081, upper connector; 3082, first insulating shell; 3083, male head; 4, bottom hole pressure monitoring pipe string; 401, bottom hole pressure gauge support; 402, oil pipe shoe. DETAILED DESCRIPTION

[0085] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0086] See also Figure 1 -15. The present invention provides a technical solution:

[0087] Example:

[0088] A real-time monitoring device for liquid accumulation in a gas well based on modular digital tubing, comprising a digital tubing docking mechanism, a single-point pressure monitoring string 2, a bottom hole pressure monitoring string 4, a wellhead gas tree cable crossing device 1, and a ground data center, wherein the digital tubing docking mechanism, the single-point pressure monitoring string 2, the bottom hole pressure monitoring string 4, and the wellhead gas tree cable crossing device 1 are connected by pipe threads;

[0089] The digital oil pipe docking mechanism comprises two groups of digital oil pipes 3 arranged vertically, and the two groups of digital oil pipes 3 are movably connected to each other;

[0090] like Figure 5The digital oil pipe 3 shown includes a traditional oil pipe 302, a fixed connection device 301, a movable connection device 308, a sealing gasket 309, a cable protection shell 307, a locker 1 306, a locker 2, an armored cable 304, an armored optical cable 305, and a cable protector 303. The traditional oil pipe 302 is connected to the fixed connection device 301 through a pipe thread, and the movable connection device 308, the sealing gasket 309, the cable protection shell 307, the locker 1 306, and the locker 2 are bound to the lower side of the traditional oil pipe 302 through a large rope. After the two groups of traditional oil pipes 302 are spliced, they are untied to complete the docking of the fixed connection device 301 and the movable connection device 308;

[0091] The fixed connection device 301 is located on the upper side of the traditional oil pipe 302, the movable connection device 308, the sealing gasket 309, the cable protection shell 307, the locker 1 306, and the locker 2 are located on the lower side of the traditional oil pipe 302, and the armored optical cable 305 and the armored electrical cable 304 are fixed to the outer side of the traditional oil pipe 302 through the annular groove on the inner side of the cable protector 303. The cable protector 303 is provided with a pair of bosses with holes on the opposite side of the annular groove. There is a gap between the pair of bosses. The cable protector 303 can be attached to the traditional oil pipe 302 by tightening the bolts to reduce the gap distance. The cable protector 303 plays a role in preventing the armored optical cable 305 and the armored electrical cable 304 from collision and twisting;

[0092] The transmission of power and signals is achieved through the cooperation of the fixed connection device 301 of the digital oil pipe 3 on the lower side and the sealing gasket 309, the movable connection device 308, the cable protective shell 307, the locker 1 306 and the locker 2 of the digital oil pipe 3 on the upper side. The fixed connection device 301 cooperates with the sealing gasket 309, the movable connection device 308 and the cable protective shell 307 through the circumferential arc groove and the arc boss to achieve circumferential positioning. The upper side of the fixed connection device 301 is provided with an external thread, and the locker 1 306 and the locker 2 are provided with an internal thread. The fixed connection device 301 is connected with the sealing gasket 309, the movable connection device 308 and the cable protective shell 307 through threaded connection. 7, the movable connection device 308 is tied to the lower side of the digital oil pipe 3 by a large rope before the digital oil pipe 3 is not connected. In addition to the armored cable 304, the armored optical cable 305, the annular sealing body 3013, the second hollow stud 3014, and the optical fiber collimator 3012, the movable connection device 308 also includes an upper connector 3081, a power transmission male head, and the power transmission male head is fixed in the same way as the power transmission female head. The double locking of the locker 1 306 and the locker 2 can achieve the anti-loosening effect of the threaded connection, and at the same time can compress the sealing gasket to achieve a better end face sealing effect, so as to achieve complete sealing of the power transmission male head, the power transmission female head and the optical fiber collimator;

[0093] like Figure 6 , Figure 7 , Figure 8 As shown, the fixed connection device 301 includes, in addition to the armored cable 304 and the armored optical cable 305, a connecting collar 3011, a power transmission female head, an annular sealing body 3013, a second hollow stud 3014, and an optical fiber collimator 3012. The connecting collar 3011 is provided with a cylindrical boss and has three holes. The large holes on the left and right sides are used for installing power transmission components, and the small hole in the middle is used for installing optical fiber signal transmission components. The power transmission female head, an annular sealing body 3013, a second hollow stud 3014, and the armored cable 304 are arranged in the large holes on the left and right sides. The power transmission female head and the armored cable 304 are connected as a whole by welding, and are bonded to the upper side end face of the corresponding large hole of the connecting collar 3011 by glue. The annular sealing body 3013 and the second hollow stud 3014 are connected to the armored cable 304. The studs 3014 are sequentially installed into the hole from the lower side of the large hole of the connecting coupling 3011, and are connected to the internal thread of the large hole through the thread of the second hollow stud 3014. The second hollow stud 3014 produces an extrusion effect on the annular sealing body 3013, so that the annular sealing body 3013 fills the inner cavity of the large hole of the connecting coupling 3011 to achieve a sealing effect. The optical fiber collimator 3012, the annular sealing body 3013, the second hollow stud 3014, and the armored optical cable 305 are arranged in the middle small hole. The optical fiber collimator 3012 is bonded to the upper end face of the middle small hole of the connecting coupling 3011 by glue and is welded to the armored optical cable 305 as a whole. The connection and sealing method of the annular sealing body 3013 and the second hollow stud 3014 is the same as that of the device in the large hole of the connecting coupling 3011.

[0094] The power transmission female head comprises a spring 3018, a spring metal shell 3017, a first insulating shell 3016, and a female head 3015. The spring 3018, the spring metal shell 3017, and the female head 3015 are all installed in the first insulating shell 3016. The spring metal shell 3017 is bonded to the first insulating shell 3016 as a whole. One end face of the spring 3018 is bonded to the end face of the spring metal shell 3017 as a whole. The spring 3018 and the female head 3015 are connected as a whole by bonding. The spring 3018 and the female head 3015 are sequentially installed in the spring metal shell 3017. The female head 3018 has a conical surface that is convenient for insertion and better fit with the male head 3083. Therefore, the power transmission female head is encapsulated. When the spring 3018 is not subjected to force, only a small part of the female head 3015 is in contact with the spring metal shell 3017, and there is a certain compressible distance. The female head has a step surface for limiting the maximum compression distance of the spring 3018.

[0095] The power transmission male connector includes a male connector 3083 and a second insulating shell 3082. The male connector 3083 and the second insulating shell 3082 are bonded together, and the lower end surface of the second insulating shell 3082 is bonded to the lower end surface of the upper connector 3081 to fix the male connector 3083 in the upper connector 3081. The upper end of the female connector 3015 has a conical surface so that the male connector 3083 fits with the male connector 3083 after being inserted. When the spring 3018 is not subjected to force, the female connector 3015 contacts the spring metal shell 3017. The female connector 3015 has a step surface for limiting the compression distance of the spring 3018. The male connector 3083 has a conical surface with the same slope as the female connector 3015, so that the female connector 3015 fits with the male connector 3083 after being inserted into the male connector 3083.

[0096] The double locking of the locker 306 and the locker 2 realizes the anti-loosening effect of the threaded connection, and can compress the sealing gasket 309 to achieve the end face sealing effect, thereby realizing the complete sealing of the power transmission male head, the power transmission female head and the optical fiber collimator 3012. The power transmission male head and the power transmission female head are in full contact when the locker 306 is locked. The spring 3018 in the power transmission female head is in a compressed position, so that the female head 3015 fits tightly with the male head 3083 in the power transmission male head, thereby realizing stable and reliable power transmission. The optical fiber collimator 3012 in the fixed connection device 301 and the movable connection device 308 reaches an effective optical signal coupling distance when the locker 306 is locked, thereby realizing the transmission of optical signals. The cable protective shell 307 is used to protect the cable and avoid direct contact between the cable and the casing wall.

[0097] like Figure 2 As shown, the single-point pressure monitoring column 2 includes, in addition to the traditional oil pipe 302, the fixed connection device 301, the movable connection device 308, the sealing gasket 309, the cable protection shell 307, the locker 1 306, the locker 2, the armored cable 304, the armored optical cable 305, and the cable protector 303 in the digital oil pipe 3, the fiber grating sensor 203, the pressure gauge holder 201, and the pressing piece 202. The fixed connection device 301 and the pressure gauge holder 201 are connected with the traditional oil pipe 302 through pipe threads. The fiber grating sensor 203 is located in the circular groove on the pressure gauge holder 201, and the upper and lower sides of the fiber grating sensor 203 are blocked by the pressing piece 202. Threaded holes are opened on the pressing piece 202 and the pressure gauge holder 201, and the pressing piece 202 is fixed by screws to fix the fiber grating sensor 203.

[0098] like Fig.13As shown, the bottom hole pressure monitoring string 4 includes three sets of fiber grating sensors 203, a bottom hole pressure gauge support tube 401, a tubing shoe 402, and a pressing piece 202 in addition to the traditional tubing 302, the fixed connection device 301, the armored cable 304, the armored optical cable 305, and the cable protector 303. The fixed connection device 301, the traditional tubing 302, the bottom hole pressure gauge support tube 401 and the tubing shoe 402 are connected by pipe threads. The armored cable 304, the armored optical cable 305, and the cable protector 303 are connected by pipe threads. The optical cable 305 and the traditional oil pipe 302 are fixed to the outer wall of the traditional oil pipe 302 through the cable protector 303. The three groups of fiber grating sensors 203 are located in the long circular grooves on the bottom hole pressure gauge holder 401. The upper and lower sides of the fiber grating sensor 203 are blocked by the pressing plate 202, and threaded holes are opened on the pressing plate 202 and the bottom hole pressure gauge holder 401. The pressing plate 202 is completely fixed by screws to achieve complete fixation of the fiber grating sensor 203.

[0099] like Figure 2 , Figure 3 , Figure 4 As shown, the cable crossing device 1 for a wellhead gas tree includes, in addition to a conventional tubing 302, a tubing spool 103, a tubing hanger 102, an upper flange 101, a manual gate 104, an electric gate 105, a T-shaped flange 106, a crossing flange 107, and a gas leakage detection device 108. The tubing hanger 102 has a conical surface, and the tubing spool 103 also has a conical surface. The conventional tubing 302 is connected to the tubing hanger 102 by pipe threads.

[0100] The tubing hanger 102 cooperates with the conical surface of the tubing spool 103 to hang the conventional tubing 302 and bear the weight of the conventional tubing 302 through its conical surface. The tubing spool 103, the manual gate 104, the electric gate 105, the T-flange 106 and the through flange 107 are connected by flanges. The through flange 107 is connected to the gas leakage detection device 108 by threads. The through flange 107 is used for the armored cable 304 and the armored optical cable 305 to pass out of the well to the ground.

[0101] The through flange 107 includes a through flange body 1071, a sealing body 1072, a V-shaped ring 1073, and a first hollow stud 1074. The through flange body 1071 has a first hole, a second hole, and a third hole, which are respectively allocated to the wellhead crossing of two groups of armored cables 304 and armored optical cables 305. The armored optical cables 305 pass through the inner holes of the sealing body 1072, the V-shaped ring 1073, and the first hollow stud 1074 in sequence, and the sealing body 1072, the V-shaped ring 1073, the first hollow stud 1074 are connected to the through flange 1071. The column 1074 is sequentially installed into the third hole of the through flange body 1071, the first hollow stud 1074 is connected to the third hole of the through flange body 1071 through a thread, and a small hole with a reduced diameter is provided in the third hole of the through flange body 1071. Under the tightening action of the generated end face and the first hollow stud 1074, the sealing body 1072 in the hole expands and seals, and clamps the armored optical cable 305, thereby realizing the crossing of the armored optical cable 305. The crossing method of the armored cable 304 is the same as that of the armored optical cable 305.

[0102] The gas leakage detection device 108 includes a gas detection device body 1082, a gas detection device shell 1081, and a top cover 1083. The gas detection device body 1082 is used to detect natural gas leakage. The gas detection device shell 1081 is a five-sided cube, wherein two sides have long openings for cables to pass through. The top cover 1083 is directly covered on the upper end of the gas detection device shell 1081 and can be fixed by gravity and multi-faceted cooperation. The gas detection device shell 1081 and the top cover 1083 form a relatively close gas detection device body 1082. The gas detection device body 1082 is installed on the upper side of the gas detection device shell 1081. The density of natural gas is higher than that of air and gathers on the upper side of the gas detection device shell 1081. When natural gas leaks, the gas detection device body 1082 will alarm and upload data to the control center and the cloud to notify the user of the situation. When gas leaks, the gas detection device body 1082 will interact with the electric gate 105 to control the electric gate 105 to close and block the gas leakage. When the staff arrives at the scene, they need to close the manual gate 104 and check the specific leakage point before repairing and replacing the leaking parts.

[0103] The ground data center includes a fiber grating demodulator, a light detector, a light source, an armored optical cable 305, a power supply, an armored cable 304, and a computer. The fiber grating demodulator, the light detector, and the light source are connected through the armored optical cable 305, and the light source, the power supply, and the computer are connected through the armored cable 304. The light detector is used to detect the reflected light signal and convert it into an electrical signal. The fiber grating demodulator is used to analyze the wavelength change of the reflected light and convert it into a physical signal. The computer calculates the depth of the liquid accumulation in the well through a built-in program algorithm.

[0104] In addition, in order to achieve the above-mentioned purpose, the present invention also provides a method for real-time monitoring of liquid accumulation in gas wells based on modular digital oil pipes, which is used in the above-mentioned real-time monitoring device for liquid accumulation in gas wells, including a downhole signal transmission method and a gas well liquid accumulation calculation method;

[0105] The downhole signal transmission method is:

[0106] The light source is emitted by the wellhead laser, and the optical signal is connected between digital oil pipes through the optical fiber collimator of the digital oil pipe. N fiber Bragg grating sensors use n Bragg gratings with different reflection wavelengths to be arranged along a single optical fiber and are placed at n different monitoring positions of the traditional oil pipe. When the physical quantity to be measured at these positions changes, the wavelength coded signal reflected back by each Bragg grating carries the change information of the physical quantity to be measured at the corresponding position. The change of the physical quantity to be measured can be obtained by decoding through the fiber Bragg grating modulator at the receiving end and analyzing the Bragg wavelength displacement, thereby realizing real-time and online monitoring of multiple monitoring positions by one optical fiber line.

[0107] The gas well liquid loading monitoring method mainly includes the following steps:

[0108] Step 1: Data acquisition, using digital tubing to transmit power and signals, a pressure gauge holder is arranged every 300m, and a bottom hole pressure gauge holder with three fiber grating sensors is arranged at the bottom hole tubing shoe to measure the density of the liquid over a short distance, so as to increase the number of pressure measurement points, obtain the pressure data arranged along the well depth, and obtain the depth of each pressure gauge holder, casing diameter, tubing diameter, liquid density, gas density, wellhead tubing pressure and other data;

[0109] Step 2: According to the relationship between the depth of liquid accumulation and the position of the bottom hole sensor group, the liquid accumulation situation is divided into three situations according to the judgment conditions: above the bottom hole pressure gauge support tube, between the bottom hole pressure gauge support tube, and below the bottom hole pressure gauge support tube;

[0110] Step 3: Combined with the pressure monitoring data value, when the pressure gradient monitored by the three fiber Bragg grating pressure sensors on the bottom hole pressure gauge holder is greater than 0.2MPa / 100m, and the pressure gradients between adjacent fiber Bragg grating sensors are equal ΔP1 / 100=ΔP2 / 100 and the data value is relatively stable, it is determined that the liquid accumulation depth is above the bottom hole pressure gauge holder. According to the multi-point pressure data tested, the pressure trend lines of the gas phase and the liquid phase are fitted, and the intersection of the two trend lines is the liquid accumulation depth in the casing annulus;

[0111] Step 4: Combined with the pressure monitoring data value, when the pressure gradient monitored by the fiber Bragg grating pressure sensor on the bottom hole pressure gauge holder is greater than 0.2MPa / 100m, but the pressure gradients between adjacent fiber Bragg grating sensors are unequal and unstable, it is determined that the liquid accumulation depth is located between the bottom hole pressure gauge holders. Since the length of this section of the bottom hole pressure gauge holder is short, the amount of liquid accumulation is small, and the middle depth of the bottom hole pressure gauge holder is considered to be the liquid accumulation depth;

[0112] Step 5: Combined with the pressure monitoring data value, when the pressure gradient monitored by the two fiber Bragg grating pressure sensors at the bottom of the bottom hole pressure gauge support is less than 0.2MPa / 100m, it is determined that the depth of the liquid accumulation is below the bottom hole pressure gauge support, and the depth of the liquid accumulation is calculated based on the pressure change of the fiber Bragg grating sensor at the bottom and the liquid density in step 1;

[0113] Step 6: Calculate the depth of liquid accumulation in the tubing based on the depth of liquid accumulation in the casing annulus and the real-time measured density of liquid accumulation.

[0114] A real-time monitoring method for liquid accumulation in gas wells based on modular digital oil pipes, wherein the detailed calculation steps of liquid accumulation in step 3 are as follows:

[0115] The pressure gradient inflection point was determined by using ΔP / 100>0.2MPa / 100m as the judgment condition, and the pressure data were divided into two groups according to the inflection point;

[0116] The depth of each sensor from the wellhead to the well is set to x1, x2....x n , m; pressure data is set to y1, y2...y n , MPa;

[0117] The gas-liquid two-phase pressure trend lines are set as:

[0118] y=a1x+b1

[0119] y=a2x+b2

[0120] Where a1 and b1 are the parameters of the gas phase trend line equation, and a2 and b2 are the parameters of the liquid phase trend line equation;

[0121] The parameter calculation formula is:

[0122]

[0123] The depth of the effusion is:

[0124]

[0125] Where x0 is the depth of effusion, m.

[0126] The calculation of the liquid accumulation depth in step 5 includes: the liquid accumulation depth changes from above the lowermost fiber Bragg grating sensor to below the lowermost fiber Bragg grating sensor, and the liquid accumulation depth is below the lowermost fiber Bragg grating sensor;

[0127] When the depth of the accumulated liquid changes from above the lowest fiber grating sensor to below the lowest fiber grating sensor, the calculation method is:

[0128]

[0129] Where h 液 Indicates the depth of liquid accumulation in the casing, m; H0 indicates the depth of the lowest fiber Bragg grating sensor, m; P2 indicates the latest pressure value measured by the lowest fiber Bragg grating sensor, MPa; P1 indicates the last pressure value measured by the lowest fiber Bragg grating sensor, MPa; ρ 气 Indicates the measured gas density, kg / m 3 ; g represents the acceleration due to gravity, m / s 2 ; A represents the amplification factor, which is ρ 液 / ρ 气 ;

[0130] When the liquid accumulation depth is below the lowest fiber grating sensor, the calculation method is:

[0131]

[0132] Where h0 represents the depth of effusion at the last measurement;

[0133] The calculation method in step six is:

[0134]

[0135] Where h 液 Indicates the depth of liquid accumulation in the oil pipe, m; P 井底 Indicates the actual pressure measured by the fiber grating sensor at the bottom, MPa; P 井口 Indicates the measured pressure in the wellhead tubing, MPa; ρ 气 Indicates the gas density in the oil pipe measured at the wellhead, kg / m 3 ρliquid represents the measured liquid density downhole, kg / m 3 ; g represents the acceleration due to gravity, m / s 2 ; H represents the depth of the bottom fiber Bragg grating sensor, m.

[0136] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe, characterized in that; It includes a digital tubing docking mechanism, a single-point pressure monitoring string, a bottom hole pressure monitoring string, a wellhead gas tree cable crossing device, and a ground data center. The digital tubing docking mechanism, the single-point pressure monitoring string, the bottom hole pressure monitoring string, and the wellhead gas tree cable crossing device are connected through pipe threads.

2. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 1, characterized in that: The digital oil pipe docking mechanism comprises two groups of digital oil pipes arranged vertically, and the two groups of digital oil pipes are movably connected to each other; The digital oil pipe comprises a traditional oil pipe, a fixed connection device, a movable connection device, a sealing gasket, a cable protective shell, a locker 1, a locker 2, an armored cable, an armored optical cable, and a cable protector. The traditional oil pipe is connected to the fixed connection device through a pipe thread, and the movable connection device, the sealing gasket, the cable protective shell, the locker 1, and the locker 2 are bound to the lower side of the traditional oil pipe through a large rope. After the two sets of traditional oil pipes are spliced, they are untied to complete the docking of the fixed connection device and the movable connection device; The fixed connection device is located on the upper side of the traditional oil pipe, the movable connection device, the sealing gasket, the cable protection shell, the first locker, and the second locker are located on the lower side of the traditional oil pipe, the armored optical cable and the armored electrical cable are fixed to the outer side of the traditional oil pipe through the annular groove on the inner side of the cable protector, and the cable protector is provided with a pair of bosses with holes on the opposite side of the annular groove, and there is a gap between the pair of bosses, and the cable protector can be attached to the traditional oil pipe by tightening the bolts to reduce the gap distance, and the cable protector can prevent the armored optical cable and the armored electrical cable from collision and twisting; The transmission of power and signals is achieved through the cooperation of the fixed connection device of the digital oil pipe on the lower side and the sealing gasket, movable connection device, cable protective shell, locker 1 and locker 2 of the digital oil pipe on the upper side. The fixed connection device cooperates with the sealing gasket, movable connection device and cable protective shell through circumferential arc grooves and arc bosses to achieve circumferential positioning. The upper side of the fixed connection device is provided with an external thread, and the locker 1 and locker 2 are provided with internal threads. The axial positioning of the fixed connection device and the sealing gasket, movable connection device and cable protective shell is achieved through threaded connection.

3. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 2, characterized in that: In addition to the armored cable and the armored optical cable, the fixed connection device also includes a connecting collar, a power transmission female head, an annular sealing body, a second hollow stud, and an optical fiber collimator. The connecting collar is provided with a cylindrical boss and has three holes. The large holes on the left and right sides are used for installing power transmission components, and the small hole in the middle is used for installing optical fiber signal transmission components. The large holes on the left and right sides are provided with a power transmission female head, an annular sealing body, a second hollow stud, and an armored cable. The power transmission female head is connected to the armored cable as a whole by welding, and is bonded to the upper end face of the corresponding large hole of the connecting collar by glue. The annular sealing body is connected to the second hollow stud. Two hollow studs are sequentially installed into the hole from the lower side of the large hole of the connecting coupling, and are connected to the internal thread of the large hole through the thread of the second hollow stud. The second hollow stud produces an extrusion effect on the annular sealing body, so that the annular sealing body fills the inner cavity of the large hole of the connecting coupling to achieve a sealing effect. The middle small hole is provided with a fiber optic collimator, an annular sealing body, a second hollow stud, and an armored optical cable. The fiber optic collimator is bonded to the upper end face of the middle small hole of the connecting coupling by glue and is welded to the armored optical cable as a whole. The connection and sealing method of the annular sealing body and the second hollow stud is the same as that of the device in the large hole of the connecting coupling.

4. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 3, characterized in that: The power transmission female connector comprises a spring, a spring metal shell, a first insulating shell, and a female connector. The spring, the spring metal shell, and the female connector are all installed in the first insulating shell. The spring metal shell is bonded to the first insulating shell as a whole. One end face of the spring is bonded to the end face of the spring metal shell as a whole. The spring and the female connector are bonded to each other as a whole. The spring and the female connector are sequentially installed in the spring metal shell. The power transmission male connector includes a male connector and a second insulating shell. The male connector and the second insulating shell are bonded as a whole, and the lower end surface of the second insulating shell is bonded to the lower end surface of the upper connector to fix the male connector in the upper connector. The upper end of the female connector has a conical surface so that the female connector fits with the male connector after being inserted. When the spring is not subjected to force, the female connector contacts the spring metal shell. The female connector has a step surface for limiting the compression distance of the spring. The male connector has a conical surface with the same slope as the female connector, so that the female connector fits with the male connector after being inserted into the male connector.

5. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 4, characterized in that: The movable connection device includes, in addition to the armored cable, the armored optical cable, the annular sealing body, the second hollow stud, and the optical fiber collimator, an upper connector, a power transmission male head, and the power transmission male head is fixed in the same manner as the power transmission female head; The double locking of the locker 1 and the locker 2 achieves the anti-loosening effect of the threaded connection, and can compress the sealing gasket to achieve the end face sealing effect, thereby achieving complete sealing of the power transmission male head, the power transmission female head and the optical fiber collimator. The power transmission male head and the power transmission female head are in full contact when the locker 1 is locked, and the spring in the power transmission female head is in a compressed position, so that the female head fits tightly with the male head in the power transmission male head, thereby achieving stable and reliable power transmission. The optical fiber collimator in the fixed connection device and the movable connection device reaches an effective optical signal coupling distance when the locker 1 is locked, thereby achieving optical signal transmission. The cable protective shell is used to protect the cable and avoid direct contact between the cable and the casing wall.

6. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 5, characterized in that: The single-point pressure monitoring string includes not only all components of the digital oil pipe, but also a fiber grating sensor, a pressure gauge holder, and a pressing piece. The fixed connection device, the pressure gauge holder, and the traditional oil pipe are connected by pipe threads. The fiber grating sensor is located in a circular groove on the pressure gauge holder, and the upper and lower sides of the fiber grating sensor are blocked by the pressing piece. Threaded holes are provided on the pressing piece and the pressure gauge holder, and the pressing piece is fixed by screws to fix the fiber grating sensor.

7. A real-time monitoring device for liquid accumulation in a gas well based on modular digital oil pipe as claimed in claim 6, characterized in that: The bottom hole pressure monitoring string includes, in addition to conventional oil pipes, fixed connection devices, armored cables, armored optical cables, and cable protectors, three groups of fiber optic Bragg grating sensors, a bottom hole pressure gauge holder, a tubing shoe, and a pressing piece. The fixed connection device, conventional oil pipe, bottom hole pressure gauge holder, and tubing shoe are connected via pipe threads. The armored cables, armored optical cables, and conventional oil pipes are fixed to the outer wall of the conventional oil pipes via cable protectors. The three groups of fiber optic Bragg grating sensors are located in the oblong grooves on the bottom hole pressure gauge holder. The upper and lower sides of the fiber optic Bragg grating sensors are blocked by the pressing piece. Threaded holes are provided on the pressing piece and the bottom hole pressure gauge holder. The pressing piece is completely fixed by screws to achieve complete fixation of the fiber optic Bragg grating sensors.

8. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 7, characterized in that: The cable crossing device of the wellhead gas production tree includes, in addition to the traditional oil pipe, an oil pipe spool, an upper flange, a manual gate, an electric gate, a T-flange, a crossing flange, and a gas leakage detection device. The oil pipe hanger has a conical surface, and the oil pipe spool also has a conical surface. The traditional oil pipe is connected to the oil pipe hanger through a pipe thread. The oil pipe hanger cooperates with the conical surface of the oil pipe spool to suspend the traditional oil pipe and bear the weight of the traditional oil pipe through its conical surface. The oil pipe spool, the manual gate, the electric gate, the T-flange and the crossing flange are connected through flanges. The crossing flange is connected to The gas leakage detection device is connected by threads. The through flange is used for armored cables and armored optical cables to pass through the well to the ground. The through flange includes a through flange body, a sealing body, a V-ring, and a first hollow stud. The through flange body has a first hole, a second hole, and a third hole, which are respectively allocated to the wellhead passages of two groups of armored cables and armored optical cables. The armored optical cable passes through the sealing body, the V-ring, and the inner holes of the first hollow stud in turn, and the sealing body, the V-ring, and the first hollow stud are sequentially installed in the third hole of the through flange body. The first hollow stud and the third hole of the through flange body are connected by threads. The third hole of the through flange body is provided with a small hole of reduced diameter. When the generated end face and the first hollow stud are tightened, the sealing body in the hole expands and seals, and clamps the armored optical cable to realize the crossing of the armored optical cable. The crossing method of the armored cable is the same as that of the armored optical cable. The gas leakage detection device includes a gas detection device body, a gas detection device shell, and a top cover. The gas detection device body is used to detect natural gas leakage. The gas detection device shell is a five-sided cube, wherein the two side surfaces have long openings for the cable to pass through, and the top cover is directly covered on the gas detection device shell. The end can be fixed by relying on gravity and multi-faceted cooperation, and it has a long opening for the cable to pass through. The gas detection device shell and the top cover form a relatively sealed space for the gas detection device body. The gas detection device body is installed on the upper side of the gas detection device shell. The density of natural gas is higher than that of air and gathers on the upper side of the gas detection device shell. When a natural gas leaks, the gas detection device body will alarm and upload data to the control center and the cloud to notify the user of the situation. When the gas leaks, the gas detection device body will be linked with the electric gate to control the electric gate to close and prevent the gas leakage.

9. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 8, characterized in that: The ground data center includes a fiber grating demodulator, a light detector, a light source, an armored optical cable, a power supply, an armored cable, and a computer. The fiber grating demodulator, the light detector, and the light source are connected via an armored optical cable, and the light source, the power supply, and the computer are connected via an armored cable. The light detector is used to detect the reflected light signal and convert it into an electrical signal. The fiber grating demodulator is used to analyze the wavelength change of the reflected light and convert it into a physical signal. The computer calculates the depth of the liquid accumulation in the well through a built-in program algorithm.

10. A method for real-time monitoring of liquid accumulation in gas wells based on modular digital oil pipes, used in the real-time monitoring device for liquid accumulation in gas wells as claimed in any one of claims 1 to 9, characterized in that: Including downhole signal transmission method and gas well liquid accumulation calculation method; The downhole signal transmission method is: The light source is emitted by the wellhead laser, and the optical signal is connected between digital oil pipes through the optical fiber collimator of the digital oil pipe. N fiber Bragg grating sensors use n Bragg gratings with different reflection wavelengths to be arranged along a single optical fiber and are placed at n different monitoring positions of the traditional oil pipe. When the physical quantity to be measured at these positions changes, the wavelength coded signal reflected back by each Bragg grating carries the change information of the physical quantity to be measured at the corresponding position. The change of the physical quantity to be measured can be obtained by decoding through the fiber Bragg grating modulator at the receiving end and analyzing the Bragg wavelength displacement, thereby realizing real-time and online monitoring of multiple monitoring positions by one optical fiber line. The gas well liquid accumulation monitoring method mainly comprises the following steps: Step 1: Data acquisition, using digital tubing to transmit power and signals, a pressure gauge holder is arranged every 300m, and a bottom hole pressure gauge holder with three fiber grating sensors is arranged at the bottom hole tubing shoe to measure the density of the liquid over a short distance, so as to increase the number of pressure measurement points, obtain the pressure data arranged along the well depth, and obtain the depth of each pressure gauge holder, casing diameter, tubing diameter, liquid density, gas density, and pressure data in the wellhead tubing; Step 2: According to the relationship between the depth of liquid accumulation and the position of the bottom hole sensor group, the liquid accumulation situation is divided into three situations according to the judgment conditions: above the bottom hole pressure gauge support tube, between the bottom hole pressure gauge support tube, and below the bottom hole pressure gauge support tube; Step 3: Combined with the pressure monitoring data value, when the pressure gradient monitored by the three fiber Bragg grating pressure sensors on the bottom hole pressure gauge holder is greater than 0.2MPa / 100m, and the pressure gradients between adjacent fiber Bragg grating sensors are equal (ΔP1 / 100=ΔP2 / 100) and the data value is relatively stable, it is determined that the liquid accumulation depth is above the bottom hole pressure gauge holder. According to the multi-point pressure data tested, the pressure trend lines of the gas phase and the liquid phase are fitted, and the intersection of the two trend lines is the liquid accumulation depth in the casing annulus; Step 4: Combined with the pressure monitoring data value, when the pressure gradient monitored by the fiber Bragg grating pressure sensor on the bottom hole pressure gauge holder is greater than 0.2MPa / 100m, but the pressure gradients between adjacent fiber Bragg grating sensors are unequal and unstable, it is determined that the liquid accumulation depth is located between the bottom hole pressure gauge holders. Since the length of this section of the bottom hole pressure gauge holder is short, the amount of liquid accumulation is small, and the middle depth of the bottom hole pressure gauge holder is considered to be the liquid accumulation depth; Step 5: Combined with the pressure monitoring data value, when the pressure gradient monitored by the two fiber Bragg grating pressure sensors at the bottom of the bottom hole pressure gauge holder is less than 0.2MPa / 100m, it is determined that the depth of the liquid accumulation is below the bottom hole pressure gauge holder, and the depth of the liquid accumulation is calculated according to the pressure change of the fiber Bragg grating sensor at the bottom and the liquid density described in step 1; Step 6: Calculate the depth of liquid accumulation in the oil pipe according to the depth of liquid accumulation in the casing annulus and the real-time measured density of liquid accumulation; The detailed calculation steps for the effusion in step 3 are as follows: The pressure gradient inflection point was determined by using ΔP / 100>0.2MPa / 100m as the judgment condition, and the pressure data were divided into two groups according to the inflection point; The depth of each sensor from the wellhead to the well is set to x1, x2....x n , m; pressure data is set to y1, y2...y n , MPa; The gas-liquid two-phase pressure trend lines are set as: y=a1x+b1 y=a2x+b2 Where a1 and b1 are the parameters of the gas phase trend line equation, and a2 and b2 are the parameters of the liquid phase trend line equation; The parameter calculation formula is: The depth of the effusion is: Where x0 is the depth of effusion, m; The calculation of the effusion depth in step 5 includes: the effusion depth changes from above the lowermost fiber Bragg grating sensor to below the lowermost fiber Bragg grating sensor, and the effusion depth is below the lowermost fiber Bragg grating sensor; When the depth of the accumulated liquid changes from above the lowest fiber grating sensor to below the lowest fiber grating sensor, the calculation method is: Where h 液 Indicates the depth of liquid accumulation in the casing, m; H0 indicates the depth of the lowest fiber Bragg grating sensor, m; P2 indicates the latest pressure value measured by the lowest fiber Bragg grating sensor, MPa; P1 indicates the last pressure value measured by the lowest fiber Bragg grating sensor, MPa; ρ 气 Indicates the measured gas density, kg / m 3 ; g represents the acceleration due to gravity, m / s 2 ; A represents the amplification factor, which is ρ 液 / ρ 气 ; When the liquid accumulation depth is below the lowest fiber grating sensor, the calculation method is: Where h0 represents the depth of effusion at the last measurement; The calculation method in step six is: Where h 液 Indicates the depth of liquid accumulation in the oil pipe, m; P 井底 Indicates the actual pressure measured by the fiber grating sensor at the bottom, MPa; P 井口 Indicates the measured pressure in the wellhead tubing, MPa; ρ 气 Indicates the gas density in the oil pipe measured at the wellhead, kg / m 3 ; ρ 液 Indicates the measured liquid density underground, kg / m 3 ; g represents the acceleration due to gravity, m / s 2 ; H represents the depth of the bottom fiber Bragg grating sensor, m.

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