A real-time monitoring device and method for gas well liquid accumulation based on modular digital oil pipe

Abstract

The present invention relates to the technical field of natural gas extraction, drainage and gas production, and specifically to a real-time monitoring device and method for gas well liquid accumulation based on modular digital oil pipes, comprising 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; all components are installed on the oil pipe, and the digital oil pipe is docked to complete the transmission of electricity and signals, and the operation is simple. The device does not change the structure of the traditional oil pipe string. The transmission of signals and electricity does not require the additional installation of special transmission joints between the pipe strings. The overall pipe string strength remains unchanged. When two digital oil pipes are docked, it is only necessary to axially and circumferentially position the fixed connection device and the movable connection device.

Description

Technical Field

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

[0002] Liquid accumulation in gas wells typically occurs due to decreased formation pressure and reduced well productivity, which increases the wellbore temperature gradient. This causes some components of the natural gas to condense within the wellbore, forming condensate. Simultaneously, insufficient reservoir energy prevents the well's gas production from discharging this condensate, causing it to fall back to the wellbore and accumulate. Furthermore, the generation of edge and bottom water during natural gas development allows formation water to enter the wellbore along with the natural gas and accumulate at the bottom. These factors combine to cause liquid accumulation within the wellbore, impacting normal production and efficiency. This not only reduces well production but can also lead to waterlogging. Consequently, various drainage recovery strategies have been developed, such as gas lift, plunger, foam drainage, and optimized string drainage. In recent years, the amount of downhole liquid accumulation has become crucial for drainage recovery. This is particularly true for shale gas wells in the Sichuan and Chongqing regions, where drainage recovery is a common problem in the late stages of production. However, direct measurement methods remain limited, compromising the integrity and accuracy of production data.

[0003] Currently, there are numerous methods for determining liquid loading in gas wells. Aside from the pressure gradient method and echo sounder monitoring, other methods, such as determining wellhead casing pressure and empirical production estimates, are indirect measurement methods and their calculated results cannot guarantee accuracy. The pressure gradient method utilizes a slickline and a sensor-separated lowering device. This method is suitable for short-term wireline downhole monitoring but is not suitable for downhole tools (such as plunger drainage and gas recovery) within the tubing string, as it disrupts normal production and is unsuitable for long-term downhole monitoring. The echo sounder monitoring method has lower measurement accuracy than the pressure gradient method and is affected by downhole cleanliness and ambient noise. Furthermore, signal analysis and processing are required, which presents a high technical challenge. Accurately calculating the amount of liquid loading at the bottom of a liquid-loaded gas well is an unavoidable and imperative issue. Therefore, a new direct method for real-time monitoring of bottomhole liquid loading is needed.

[0004] Traditional electronic downhole pressure gauges have problems such as electromagnetic interference and insufficient tolerance to high temperature and high pressure in the well, and a pressure gauge often has multiple wires. Fiber optic sensors are resistant to electromagnetic interference, can withstand high temperature and high pressure, do not require electricity, and especially can multiplex multiple channels, allowing multiple signal transmissions to be achieved via a single fiber optic line. 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 gas wells based on modular digital oil pipes includes 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 includes 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 first locker, a second locker, 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. The movable connection device, the sealing gasket, the cable protective shell, the first locker, and the second locker are tied to the lower side of the traditional oil pipe by 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.

[0010] The fixed connection device is located on the upper side of the traditional oil pipe, and the movable connection device, sealing gasket, cable protective shell, locker 1, and locker 2 are located on the lower side of the traditional oil pipe. The armored optical cable and armored electrical cable are fixed to the outside of the traditional oil pipe through the annular groove on the inner side of the cable protector. The cable protector is provided with a pair of bosses with holes on opposite sides of the annular groove. There is a gap between the pair of bosses. Bolts are tightened to reduce the gap distance so that the cable protector can fit on the traditional oil pipe. The cable protector prevents the armored optical cable and armored electrical cable from collision and twisting.

[0011] The transmission of power and signals is achieved through the fixed connection device of the digital oil pipe on the lower side, and the cooperation with 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 and the sealing gasket, movable connection device and cable protective shell cooperate with each other through circumferential arc grooves and arc-shaped 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, 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 left and right large holes are used for installing power transmission components, and the middle small hole is used for installing optical fiber signal transmission components. The left and right large holes 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 and the armored cable are connected as a whole by welding, and are bonded to the upper end face of the corresponding large hole of the connecting collar by glue. The annular sealing body and 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 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 hole of the connecting coupling by glue and welded to the armored optical cable. The connection and sealing method of the annular sealing body and the second hollow stud is the same as the connection method in the large hole of the connecting coupling.

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

[0014] Preferably, the movable connection device includes not only the armored cable, the armored optical cable, the annular sealing body, the second hollow stud, and the optical fiber collimator, but also an upper connector, a power transmission male head, and the power transmission male head and the power transmission female head are fixed in the same way.

[0015] Preferably, the power transmission male connector includes a male connector and a second insulating shell. The male connector and the second insulating shell are bonded together, and the lower end face of the second insulating shell is bonded to the lower end face of the upper connector to fix the male connector in the upper connector. The upper end of the female connector has a tapered surface so that it fits with the male connector after being inserted. When the spring is not under 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 tapered 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 at the same time can compress the sealing gasket to achieve an end face sealing effect, thereby realizing 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. 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 realizing 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 realizing the transmission of optical signals. 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 string includes not only all the components of the digital oil pipe, but also 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 opened 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 the traditional oil pipe, fixed connection device, armored cable, armored optical cable, and cable protector, 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, the traditional oil pipe, the bottom hole pressure gauge holder and the tubing shoe are connected by pipe threads, and the armored cable, armored optical cable and the traditional oil pipe are fixed to the outer wall of the traditional oil pipe through the cable protector. The three groups of fiber optic Bragg grating sensors are located in the long circular groove on the bottom hole pressure gauge holder, and the upper and lower sides of the fiber optic Bragg grating sensors are blocked by the pressing piece. Threaded holes are opened on the pressing piece and the bottom hole pressure gauge holder, and the pressing piece is completely fixed by screws to achieve complete fixation of the fiber optic Bragg grating sensor.

[0019] Preferably, the cable crossing device of the wellhead gas production tree includes, in addition to the traditional oil pipe, an oil pipe four-way, an oil pipe hanger, 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 four-way 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 four-way through its conical surface to suspend the traditional oil pipe and bear the weight of the traditional oil pipe. The oil pipe four-way, manual gate, electric gate, T-flange and crossing flange are connected through flanges. The crossing flange is connected to the gas leakage detection device through 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 distributed 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 diameter reduction hole 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 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.

[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 leaks. The gas detection device shell is a five-sided cube, two side surfaces of which have long openings for 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. It has long openings for 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 it gathers 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 a wellhead laser, and the optical signal passes through the digital oil pipeline's fiber collimator to achieve optical signal docking between digital oil pipelines. N fiber Bragg grating sensors use n Bragg gratings with different reflection wavelengths arranged along a single optical fiber and placed at n different monitoring locations on the traditional oil pipeline. When the physical quantity to be measured at these locations 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 location. The fiber Bragg grating demodulator at the receiving end decodes the signal and analyzes the Bragg wavelength shift to obtain the change information of the physical quantity to be measured, thus realizing real-time, online monitoring of multiple monitoring locations through a single 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 placed every 300 meters. A bottomhole pressure gauge holder equipped with three fiber grating sensors is placed at the bottomhole tubing shoe to measure liquid density over short distances. This increases the number of pressure measurement points and allows for pressure data along the depth of the well. Data such as the depth of each pressure gauge holder, casing diameter, tubing diameter, liquid density, gas density, and pressure within the wellhead tubing are acquired.

[0028] Step 2: Based on 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, when the pressure gradient monitored by the three fiber Bragg grating pressure sensors on the bottomhole pressure gauge holder is greater than 0.2 MPa / 100 m, the pressure gradients between adjacent fiber Bragg grating sensors are equal (ΔP1 / 100 = ΔP2 / 100), and the data values are relatively stable, it is determined that the liquid accumulation depth is above the bottomhole pressure gauge holder. Based on the multi-point pressure data tested, the pressure trend lines of the gas and liquid phases are fitted. The intersection of the two trend lines is the liquid accumulation depth in the casing annulus.

[0030] Step 4: Based on the pressure monitoring data, when the pressure gradient monitored by the fiber Bragg grating pressure sensor on the bottom hole pressure gauge holder is greater than 0.2 MPa / 100 m, but the pressure gradients between adjacent fiber Bragg grating sensors are unequal and unstable, it is determined that the liquid accumulation depth is 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 depth in the middle of the bottom hole pressure gauge holders is considered to be the liquid accumulation depth;

[0031] Step 5: When the pressure gradient monitored by the two fiber Bragg grating pressure sensors on the bottom of the bottom hole pressure gauge holder is less than 0.2 MPa / 100 m, the depth of the liquid accumulation is determined to be below the bottom hole pressure gauge holder. The depth of the liquid accumulation is calculated based on the pressure change of the bottom of the fiber Bragg grating sensor 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. The detailed calculation steps for 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 bottom of the well is set as 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]

[0038] 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;

[0039] The parameter calculation formula is:

[0040]

[0041] The depth of the effusion is:

[0042]

[0043] Where x0 is the depth of effusion, m.

[0044] 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;

[0045] When the depth of the accumulated liquid changes from above the lowest fiber Bragg grating sensor to below it, the calculation method is:

[0046]

[0047] 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 ;

[0048] When the depth of the accumulated liquid is below the lowest fiber Bragg grating sensor, the calculation method is:

[0049]

[0050] Where h0 represents the depth of effusion at the last measurement;

[0051] The calculation method in step six is:

[0052]

[0053] Where h 液 Indicates the depth of liquid accumulation in the oil pipe, m; P 井底 Indicates the actual pressure measured by the bottom fiber Bragg grating sensor, 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.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 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. The operation is simple.

[0056] 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 pipe string strength remains unchanged.

[0057] 3. When two digital oil pipes are connected, it is only necessary to axially and circumferentially position the fixed connection device and the movable connection device to achieve the connection 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 plugging operations.

[0058] 4. There is a spring inside the power transmission female connector, and the contact surfaces of the male and female connectors have the same taper. After the power is connected, the spring is in a compressed state, making the male and female connectors fit tightly together.

[0059] 5. Use fiber optic collimators to transmit optical signals and realize non-contact optical signal transmission.

[0060] 6. Under the conditions of up to several thousand meters vertical distance, high temperature and high pressure underground, 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, thereby increasing the service life and reliability of underground cables.

[0061] 7. The wellhead crossing flange is installed on the side pipe of the oil pipe four-way. 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.

[0062] 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. It will monitor and alarm when the wellhead sealing flange fails. It is also equipped with an electric valve 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.

[0063] 9. Use optical fiber for signal transmission, which has higher transmission rate and more stable.

[0064] 10. Using fiber grating sensors, multi-sensor signal transmission only requires one fiber channel, reducing the number of signal lines used.

[0065] 11. The device does not occupy the space inside the oil pipe and is suitable for almost all drainage and gas production processes.

[0066] 12. The system monitors the pressure at multiple points in the well in real time, and uses non-theoretical models to calculate the depth of liquid accumulation more accurately.

[0067] 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

[0068] Figure 1 Schematic diagram of the overall structure of the device of the present invention;

[0069] Figure 2 Schematic diagram of the cable crossing device for the wellhead gas tree of the present invention;

[0070] Figure 3 Schematic diagram of the inner through flange of the cable through device of the wellhead gas tree of the present invention;

[0071] Figure 4Schematic diagram of a gas leakage detection device in a cable crossing device for a wellhead gas tree according to the present invention;

[0072] Figure 5 This is a schematic diagram of the digital oil pipe structure of the present invention;

[0073] Figure 6 This is a schematic diagram of the installation of the digital oil pipe collimator of the present invention;

[0074] 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;

[0075] Figure 8 This is a schematic diagram of the structure and installation of the digital oil pipe power transmission male connector of the present invention;

[0076] Figure 9 This is a schematic diagram of the fiber optic collimator docking when the digital oil pipes of the present invention are docked;

[0077] Figure 10 This is a schematic diagram of the conductive device docking when the digital oil pipes of the present invention are docked;

[0078] Figure 11 This is a schematic diagram of circumferential positioning when the digital oil pipes of the present invention are connected;

[0079] Figure 12 This is a schematic diagram of the structure of a single-point pressure monitoring column of the present invention;

[0080] Figure 13 This is a schematic diagram of the bottom hole pressure monitoring string structure of the present invention;

[0081] Figure 14 This is a classification diagram of effusion conditions according to the method of the present invention;

[0082] Figure 15 This is the logic diagram for calculating the effusion depth according to the method of the present invention.

[0083] Figure: 1. Wellhead gas tree cable crossing device; 101. Upper flange; 102. Tubing hanger; 103. Tubing spool; 104. Manual gate; 105. Electric gate; 106. T-flange; 107. Crossing flange; 1071. Crossing flange body; 1072. Seal; 1073. V-ring; 1074. First hollow stud; 108. Gas leak 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 protective 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 connector; 3016, first insulating shell; 3017, spring metal shell; 3018, spring; 3081, upper connector; 3082, first insulating shell; 3083, male connector; 4, bottom hole pressure monitoring string; 401, bottom hole pressure gauge holder; 402, oil pipe shoe. DETAILED DESCRIPTION

[0084] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0085] See also Figure 1-15 , the present invention provides a technical solution:

[0086] Example:

[0087] A real-time monitoring device for liquid accumulation in gas wells based on modular digital tubing includes a digital tubing docking mechanism, a single-point pressure monitoring string 2, a bottomhole pressure monitoring string 4, a wellhead gas tree cable crossing device 1, and a ground data center. The digital tubing docking mechanism, the single-point pressure monitoring string 2, the bottomhole pressure monitoring string 4, and the wellhead gas tree cable crossing device 1 are connected by pipe threads.

[0088] The digital oil pipe docking mechanism includes two sets of digital oil pipes 3 arranged vertically, and the two sets of digital oil pipes 3 are movably connected to each other;

[0089] like Figure 5The digital oil pipe 3 shown includes a conventional oil pipe 302, a fixed connection device 301, a movable connection device 308, a sealing gasket 309, a cable protective shell 307, a first locker 306, a second locker, an armored cable 304, an armored optical cable 305, and a cable protector 303. The conventional oil pipe 302 is connected to the fixed connection device 301 via pipe threads. The movable connection device 308, the sealing gasket 309, the cable protective shell 307, the first locker 306, and the second locker are tied to the lower side of the conventional oil pipe 302 using a large rope. After the two sets of conventional oil pipes 302 are spliced, the rope is untied to complete the docking of the fixed connection device 301 and the movable connection device 308.

[0090] 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 protective shell 307, the locker 1 306, and the locker 2 are located on the lower side of the traditional oil pipe 302. 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 opposite sides of the annular groove. There is a gap between the pair of bosses. The gap is reduced by tightening with bolts so that the cable protector 303 can fit on the traditional oil pipe 302. The cable protector 303 prevents the armored optical cable 305 and the armored electrical cable 304 from being bumped and twisted.

[0091] 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 on the upper side of the digital oil pipe 3. 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 and the sealing gasket 309, the movable connection device 308, and the cable protective shell 307 are connected by threads. 7 axial positioning, the movable connection device 308 is fastened 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 connector, and the power transmission male connector and the power transmission female connector are fixed in the same manner. The double locking of the locker 1 306 and the locker 2 can achieve the anti-loosening effect of the threaded connection and can also compress the sealing gasket to achieve a good end face sealing effect, thereby achieving a complete seal between the power transmission male connector, the power transmission female connector and the optical fiber collimator;

[0092] 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 provided 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 end face of the large hole corresponding to the connecting collar 3011 by glue. The annular sealing body 3013 and the second hollow stud 3014 are connected to the armored cable 304 by welding. The column 3014 is sequentially installed into the hole from the lower side of the large hole of the connecting coupling 3011, and is 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 hole. The optical fiber collimator 3012 is bonded to the upper end face of the middle hole of the connecting coupling 3011 by glue and 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 the connection method in the large hole of the connecting coupling 3011.

[0093] The power transmission female connector includes a spring 3018, a spring metal shell 3017, a first insulating shell 3016, and a female connector 3015. The spring 3018, the spring metal shell 3017, and the female connector 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 connector 3015 are connected as a whole by bonding. The spring 3018 and the female connector 3015 are sequentially installed in the spring metal shell 3017. The female connector 3018 has a tapered surface that facilitates insertion and better fit with the male connector 3083. Therefore, the power transmission female connector is encapsulated. When the spring 3018 is not subjected to force, only a small portion of the female connector 3015 is in contact with the spring metal shell 3017, leaving a certain compressible distance. The female connector also has a stepped surface for limiting the maximum compression distance of the spring 3018.

[0094] 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 tapered surface so that it fits with the male connector 3083 after being inserted. When the spring 3018 is not under force, the female connector 3015 contacts the spring metal shell 3017. The female connector 3015 has a stepped surface for limiting the compression distance of the spring 3018. The male connector 3083 has a tapered 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.

[0095] The double locking of the locker 1 306 and the locker 2 realizes the anti-loosening effect of the threaded connection, and at the same time can compress the sealing gasket 309 to achieve the end face sealing effect, thereby realizing 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 1 306 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, realizing stable and reliable power transmission. The fixed connection device 301 and the optical fiber collimator 3012 in the movable connection device 308 reach an effective optical signal coupling distance when the locker 1 306 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.

[0096] like Figure 2 As shown, the single-point pressure monitoring string 2 includes, in addition to the traditional oil pipe 302, fixed connection device 301, movable connection device 308, sealing gasket 309, cable protective shell 307, locker 1 306, locker 2, armored cable 304, armored optical cable 305, and cable protector 303 in the digital oil pipe 3, a fiber Bragg grating sensor 203, a pressure gauge holder 201, and a pressing piece 202. The fixed connection device 301, the pressure gauge holder 201, and the traditional oil pipe 302 are connected by pipe threads. The fiber Bragg grating sensor 203 is located in the circular groove on the pressure gauge holder 201. The upper and lower sides of the fiber Bragg 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. The pressing piece 202 is fixed by screws to fix the fiber Bragg grating sensor 203.

[0097] like Figure 13As shown, the bottom hole pressure monitoring string 4 includes, in addition to the traditional oil pipe 302, the fixed connection device 301, the armored cable 304, the armored optical cable 305, and the cable protector 303, three sets of fiber grating sensors 203, the bottom hole pressure gauge holder 401, the tubing shoe 402, and the pressing piece 202. The fixed connection device 301, the traditional oil pipe 302, the bottom hole pressure gauge holder 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 oblong 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 piece 202, and threaded holes are opened on the pressing piece 202 and the bottom hole pressure gauge holder 401. The pressing piece 202 is completely fixed by screws to achieve complete fixation of the fiber grating sensor 203.

[0098] like Figure 2 、 Figure 3 、 Figure 4 As shown, the wellhead gas tree cable crossing device 1 includes, in addition to the 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-flange 106, a crossing flange 107, and a gas leak 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 via pipe threads.

[0099] The tubing hanger 102 cooperates with the conical surface of the tubing spool 103 to suspend the conventional tubing 302 and bear the weight of the conventional tubing 302. The tubing spool 103, the manual gate 104, the electric gate 105, the T-flange 106, and the through flange 107 are connected via flanges. The through flange 107 is threadedly connected to the gas leak detection device 108. The through flange 107 is used to pass the armored cable 304 and the armored optical cable 305 from the well to the surface.

[0100] 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 passage of two groups of armored cables 304 and armored optical cables 305. The armored optical cables 305 pass through the sealing body 1072, the V-shaped ring 1073, and the inner holes of 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 threaded connection, and a small hole with a reduced diameter is provided in the third hole of the through flange body 1071. Under the action of tightening 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 passage 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.

[0101] The gas leakage detection device 108 includes a gas detection device body 1082, a gas detection device housing 1081, and a top cover 1083. The gas detection device body 1082 is used to detect natural gas leaks. The gas detection device housing 1081 is a five-sided cube, two sides of which have long openings for cables to pass through. The top cover 1083 is directly covered on the upper end of the gas detection device housing 1081 and can be fixed by gravity and multi-faceted cooperation. The gas detection device housing 1081 and the top cover 1083 form a relatively close connection for the gas detection device body 1082. The gas detection device body 1082 is installed on the upper side of the gas detection device housing 1081. The density of natural gas is higher than that of air, and it gathers on the upper side of the gas detection device housing 1081. When a natural gas leak occurs, the gas detection device body 1082 will alarm and upload the data to the control center and the cloud to notify the user of the situation. When the gas leaks, the gas detection device body 1082 will be linked 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, and then repair and replace the leaking parts.

[0102] 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.

[0103] 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;

[0104] The downhole signal transmission method is:

[0105] The light source is emitted by a wellhead laser, and the optical signal passes through the digital oil pipeline's fiber collimator to achieve optical signal docking between digital oil pipelines. N fiber Bragg grating sensors use n Bragg gratings with different reflection wavelengths arranged along a single optical fiber and placed at n different monitoring locations on the traditional oil pipeline. When the physical quantity to be measured at these locations 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 location. The fiber Bragg grating demodulator at the receiving end decodes the signal and analyzes the Bragg wavelength shift to obtain the change information of the physical quantity to be measured, thus realizing real-time, online monitoring of multiple monitoring locations through a single optical fiber line.

[0106] The gas well liquid accumulation monitoring method mainly includes the following steps:

[0107] Step 1: Data acquisition: Using digital tubing to transmit power and signals, a pressure gauge holder is placed every 300 meters. A bottomhole pressure gauge holder equipped with three fiber grating sensors is placed at the bottomhole tubing shoe to measure liquid density over short distances. This increases the number of pressure measurement points and allows for pressure data along the depth of the well. Data such as the depth of each pressure gauge holder, casing diameter, tubing diameter, liquid density, gas density, and pressure within the wellhead tubing are acquired.

[0108] Step 2: Based on 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;

[0109] Step 3: Based on the pressure monitoring data, when the pressure gradient monitored by the three fiber Bragg grating pressure sensors on the bottomhole pressure gauge holder is greater than 0.2 MPa / 100 m, and the pressure gradients between adjacent fiber Bragg grating sensors are equal (ΔP1 / 100=ΔP2 / 100) and the data values are relatively stable, the liquid accumulation depth is determined to be above the bottomhole pressure gauge holder. Based on the multi-point pressure data tested, the pressure trend lines of the gas and liquid phases are fitted. The intersection of the two trend lines is the liquid accumulation depth in the casing annulus.

[0110] Step 4: Based on the pressure monitoring data, when the pressure gradient monitored by the fiber Bragg grating pressure sensor on the bottom hole pressure gauge holder is greater than 0.2 MPa / 100 m, but the pressure gradients between adjacent fiber Bragg grating sensors are unequal and unstable, it is determined that the liquid accumulation depth is 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 depth in the middle of the bottom hole pressure gauge holders is considered to be the liquid accumulation depth;

[0111] Step 5: Based on the pressure monitoring data, when the pressure gradient monitored by the two fiber Bragg grating pressure sensors on the bottom of the bottom hole pressure gauge holder is less than 0.2 MPa / 100 m, the depth of the liquid accumulation is determined to be below the bottom hole pressure gauge holder. The depth of the liquid accumulation is calculated based on the pressure change of the bottom fiber Bragg grating sensor and the liquid density in step 1.

[0112] 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.

[0113] A real-time monitoring method for liquid accumulation in gas wells based on modular digital oil pipes. The detailed calculation steps for liquid accumulation in step 3 are as follows:

[0114] 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;

[0115] The depth of each sensor from the wellhead to the bottom of the well is set as x1, x2...x n , m; pressure data is set to y1, y2...y n , MPa;

[0116] The gas-liquid two-phase pressure trend lines are set as:

[0117]

[0118] 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;

[0119] The parameter calculation formula is:

[0120]

[0121] The depth of the effusion is:

[0122]

[0123] Where x0 is the depth of effusion, m.

[0124] 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;

[0125] When the depth of the accumulated liquid changes from above the lowest fiber Bragg grating sensor to below it, the calculation method is:

[0126]

[0127] 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 ;

[0128] When the depth of the accumulated liquid is below the lowest fiber Bragg grating sensor, the calculation method is:

[0129]

[0130] Where h0 represents the depth of effusion at the last measurement;

[0131] The calculation method in step six is:

[0132]

[0133] Where h 液 Indicates the depth of liquid accumulation in the oil pipe, m; P 井底 Indicates the actual pressure measured by the bottom fiber Bragg grating sensor, 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.

[0134] While 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 these embodiments without departing from the principles and spirit of the invention, and that the scope of the 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 pipes, characterized by: 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 by pipe threads; The digital oil pipe docking mechanism includes 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 includes a traditional oil pipe, a fixed connection device, a movable connection device, a sealing gasket, a cable protective shell, a first locker, a second locker, an armored cable, an armored optical cable, and a cable protector. The traditional oil pipe is connected to the fixed connection device through pipe threads. The movable connection device, the sealing gasket, the cable protective shell, the first locker, and the second locker are tied to the lower side of the traditional oil pipe by a large rope. After the two sets of traditional oil pipes are spliced, the binding is 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, and the movable connection device, sealing gasket, cable protective shell, locker 1, and locker 2 are located on the lower side of the traditional oil pipe. The armored optical cable and armored electrical cable are fixed to the outside of the traditional oil pipe through the annular groove on the inner side of the cable protector. The cable protector is provided with a pair of bosses with holes on opposite sides of the annular groove. There is a gap between the pair of bosses. Bolts are tightened to reduce the gap distance so that the cable protector can fit on the traditional oil pipe. The cable protector prevents the armored optical cable and armored electrical cable from collision and twisting. The transmission of power and signals is achieved through the fixed connection device of the digital oil pipe on the lower side, and the cooperation with 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 and the sealing gasket, movable connection device and cable protective shell cooperate with each other through circumferential arc grooves and arc-shaped 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.

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: 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 left and right large holes are used for installing power transmission components, and the middle small hole is used for installing optical fiber signal transmission components. The left and right large holes 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 and the armored cable are connected as a whole by welding, and are bonded to the upper end face of the corresponding large hole of the connecting collar by glue. The annular sealing body and the second The hollow studs are sequentially installed into the holes 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 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 hole of the connecting coupling by glue and welded to the armored optical cable. The connection and sealing method of the annular sealing body and the second hollow stud is the same as the connection method in the large hole of the connecting coupling.

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: The movable connection device includes, in addition to the armored cable, armored optical cable, an annular sealing body, a second hollow stud, and an optical fiber collimator, an upper connector, a power transmission male connector, and the power transmission male connector is fixed in the same manner as the power transmission female connector; The double locking of the locker 1 and the locker 2 achieves an anti-loosening effect of the threaded connection, and at the same time can compress the sealing gasket to achieve an end face sealing effect, thereby realizing 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. 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 realizing 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 realizing the transmission of optical signals. The cable protective shell is used to protect the cable and avoid direct contact between the cable and the casing wall.

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 includes a spring, a spring metal shell, a first insulating shell, and a female connector. The spring, spring metal shell, and female connector are all installed in the first insulating shell. The spring metal shell and the first insulating shell are bonded together. One end face of the spring is bonded together with the end face of the spring metal shell. The spring and the female connector are connected together by bonding. 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 together 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 tapered surface so that it fits with the male connector after insertion. When the spring is not under 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 tapered surface with the same slope as the female connector, so that the female connector fits with the male connector after insertion.

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: In addition to all the components of the digital oil pipe, the single-point pressure monitoring string also includes 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 opened on the pressing piece and the pressure gauge holder, and the pressing piece is fixed by screws to fix the fiber grating sensor.

6. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipes according to claim 5, characterized in that: In addition to the traditional oil pipe, fixed connection device, armored cable, armored optical cable, and cable protector, the bottom hole pressure monitoring pipe string also includes 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, traditional oil pipe, bottom hole pressure gauge holder and tubing shoe are connected by pipe threads, and the armored cable, armored optical cable and traditional oil pipe are fixed to the outer wall of the traditional oil pipe through the cable protector. The three groups of fiber optic Bragg grating sensors are located in the long circular groove on the bottom hole pressure gauge holder, and the upper and lower sides of the fiber optic Bragg grating sensors are blocked by the pressing piece. Threaded holes are opened on the pressing piece and the bottom hole pressure gauge holder, and the pressing piece is completely fixed by screws to achieve complete fixation of the fiber optic Bragg grating sensor.

7. The real-time monitoring device for liquid accumulation in gas wells based on modular digital oil pipe according to claim 6, characterized in that: The cable crossing device of the wellhead gas tree includes, in addition to the traditional oil pipe, an oil pipe spool, an oil pipe hanger, 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 a threaded connection. 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-shaped 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 passage 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 sequence, and the sealing body, the V-shaped 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 is tightened with the first hollow stud, the sealing body in the hole expands and seals, and clamps the armored optical cable to realize the passage 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 leaks. 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 it gathers 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 the user 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 prevent gas leakage.

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 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.

9. A method for real-time monitoring of liquid accumulation in a gas well based on modular digital oil pipes, used in the real-time monitoring device for liquid accumulation in a gas well according to any one of claims 1 to 8, 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 a wellhead laser, and the optical signal passes through the digital oil pipeline's fiber collimator to achieve optical signal docking between digital oil pipelines. N fiber Bragg grating sensors use n Bragg gratings with different reflection wavelengths arranged along a single optical fiber and placed at n different monitoring locations on the traditional oil pipeline. When the physical quantity to be measured at these locations 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 location. The fiber Bragg grating demodulator at the receiving end decodes the signal and analyzes the Bragg wavelength shift to obtain the change information of the physical quantity to be measured, thus realizing real-time, online monitoring of multiple monitoring locations through a single 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 placed every 300 meters. A bottomhole pressure gauge holder equipped with three fiber grating sensors is placed at the bottomhole tubing shoe to measure liquid density over short distances. This increases the number of pressure measurement points and allows for pressure data to be obtained along the depth of the well. The depth, casing diameter, tubing diameter, liquid density, gas density, and pressure data within the wellhead tubing are acquired for each pressure gauge holder. Step 2: Based on 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, when the pressure gradient monitored by the three fiber Bragg grating pressure sensors on the bottomhole pressure gauge holder is greater than 0.2 MPa / 100 m, the pressure gradients between adjacent fiber Bragg grating sensors are equal (ΔP1 / 100 = ΔP2 / 100), and the data values are relatively stable, it is determined that the liquid accumulation depth is above the bottomhole pressure gauge holder. Based on the multi-point pressure data tested, the pressure trend lines of the gas and liquid phases are fitted. The intersection of the two trend lines is the liquid accumulation depth in the casing annulus. Step 4: Based on the pressure monitoring data, when the pressure gradient monitored by the fiber Bragg grating pressure sensor on the bottom hole pressure gauge holder is greater than 0.2 MPa / 100 m, but the pressure gradients between adjacent fiber Bragg grating sensors are unequal and unstable, it is determined that the liquid accumulation depth is 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 depth in the middle of the bottom hole pressure gauge holders is considered to be the liquid accumulation depth; Step 5: When the pressure gradient monitored by the two fiber Bragg grating pressure sensors on the bottom of the bottom hole pressure gauge holder is less than 0.2 MPa / 100 m, the depth of the liquid accumulation is determined to be below the bottom hole pressure gauge holder. The depth of the liquid accumulation is calculated based on the pressure change of the bottom of the fiber Bragg grating sensor and the liquid density described in step 1. 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; The detailed calculation steps for 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 bottom of the well is set as 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: 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 Bragg grating sensor to below it, 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 depth of the accumulated liquid is below the lowest fiber Bragg 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 bottom fiber Bragg grating sensor, 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.

Images