Well-adjacent casing current injection magnetic distance measurement system

Abstract

According to the system, current is injected from the ground to an underground electrode, a current loop is generated in the adjacent well sleeve, a disc-shaped magnetic field is generated in the adjacent well sleeve body, and the collected disc-shaped magnetic field is filtered and uploaded to a ground data processing instrument through unique three-axis fluxgate sensor layout and algorithm in an underground magnetic measurement short circuit. And then the data processing instrument transmits data acquired by the underground gyroscope and the magnetic measurement short circuit to the computer for resolving, and the direction and the distance of the adjacent well casing relative to the magnetic measurement short circuit are calculated.

Description

Technical Field

[0001] The present invention relates to the detection and positioning of downhole casing in the fields of oil, coalbed methane, geothermal energy, soluble minerals, etc., and is widely used in the fields of staggered casing re-entry and blowout rescue wells. Background Art

[0002] During drilling operations, casing is the pipe that isolates the formation from the internal drainage and production channels. As production progresses, the casing's structural properties change in some areas due to factors such as mudstone creep, water absorption expansion, rock sliding, fault activity, and an imbalance in the injection-production relationship during production. This reduces the strength of the casing, leading to deformation and breakage. This prevents access below the damaged area, and makes it impossible to dispose of debris trapped within the lower casing. Furthermore, earthquake-induced formation dislocation or increased local pressure in the surrounding formations can cause casing deformation and rupture, making it impossible to continue production. Under the influence of ground pressure, oil or gas leaks from the damaged casing, causing oil and gas to enter the formation through the damaged area, resulting in formation pollution and waste. In order to solve this problem, it is necessary to develop an instrument device that can detect the wellbore casing below the staggered section. It can accurately measure the direction and distance of the temporary wellbore casing relative to the rescue drill bit of the new borehole, guide the drill bit to drill into the casing as close to the casing as possible, and then use directional perforation to form an effective communication channel between the temporary wellbore casing and the temporary wellbore casing, and then inject the plugging agent from the new wellbore to finally achieve effective sealing of the new and old wellbores.

[0003] Among the currently available technical solutions, the solutions used for the detection of adjacent well casings mainly include acoustic logging and current injection logging. Both methods use different means to transmit signals to the casing, and then receive the signals returned by the casing for solution. Due to the small diameter of the casing and the weak signal reflected by the formation, the detection and receiving instrument is not accurate in solving the weak signal. In addition, it is not able to verify the received signal by itself, resulting in a large solution error. Therefore, how to develop a new magnetic measurement structure and a new algorithm to improve the reception and solution of weak signals reflected by adjacent well casings, as well as to be able to perform secondary verification of the self-solution results is a problem that needs to be solved urgently. In view of this, the present application is specially proposed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention proposes a current-injected magnetic ranging system for adjacent well casing, along with a corresponding fluxgate sensor layout and measurement algorithm. This system addresses the issue of receiving and calculating the weak, disc-shaped signals generated by a magnetic measurement short circuit. In this system, the magnetic measurement short circuit can collect magnetic signals from adjacent well casing at different tool faces while the electric device rotates. Using the system's calculation formula and combining it with the magnetic signals collected at different tool faces, the system's solution can be repeatedly verified. This shortens measurement time and improves the accuracy and reliability of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0006] Figure 1 A schematic diagram of the entire measurement system according to an embodiment of the present invention is shown;

[0007] Figure 2 A schematic diagram of the internal structure of a measurement short circuit according to an embodiment of the present invention is depicted;

[0008] Figure 3 An embodiment of the present invention is shown Figure 2 Schematic diagram of the derivation of the algorithm formula for the magnetic fluxgate structure layout; DETAILED DESCRIPTION

[0009] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described 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 work are within the scope of protection of the present invention. Figure 1 As shown, the entire current injection ranging system mainly consists of the following parts: 1 bridle, 2 signal receiving electrode, 3 long insulation short circuit, 4 signal emitter A, 5 short insulation short circuit A, 6 signal emitter B, 7 short insulation short circuit B, 8 signal emitter C, 9 short insulation short circuit C, 10 electric rotation device, 11 gyroscope short circuit, 12 magnetic measurement short circuit, 13 weighting rod, 14 ground data processing instrument, 15 current injector, 16 computer, 17 armored cable, 18 well casing, 19 current.

[0010] 1. Figure 1 The middle bridle 1 is connected to the armored cable 17 in the downhole part, and plays the role of transfer and bearing in this measurement system. The lower part of the bridle 1 is connected to the signal receiving pole 2 through a thread.

[0011] 2. Figure 1 The middle signal receiving electrode 2 mainly receives the current signal emitted by the signal emitter A 4, the signal emitter B 6, and the signal emitter C 8 in the system loop. The lower part of the signal receiving electrode 2 is connected to the long insulating short-circuit 3 through a threaded buckle.

[0012] 3. Figure 1The medium-length insulating shorting link 3 increases the insulation distance between the signal emitter A4 and the signal receiver 2, providing sufficient insulation resistance between the two electrodes to prevent short circuits caused by insufficient resistance between the emitter A4 and the signal receiver 2. The lower portion of the long insulating shorting link 3 is connected to the signal emitter A4 via a threaded fastener.

[0013] 4. Figure 1 When the middle signal emitter A4 is energized, an equipotential electric field is generated, and the electric field flows in the stratum to generate a magnetic field. The signal emitter A4 is connected to the short insulating short circuit A5 at the bottom through a threaded buckle.

[0014] 5. Figure 1 The medium-short insulating short circuit A5 provides an equipotential insulating path for the signal emitter A4 and the signal emitter B6, so that the signal emitter A4 and the signal emitter B6 can repel each other in the magnetic field when the potential is equal after power is turned on, forming a nearly flat current shape near the short insulating short circuit A5. This current is forced into the formation and flows to the nearby well casing 18. The lower part of the short insulating short circuit A5 is connected to the signal emitter B6 by a threaded connection.

[0015] 6. Figure 1 When the middle signal emitter B6 is energized, an equipotential electric field is generated. The electric field flows in the stratum to generate a magnetic field. The signal emitter B6 is connected to the short insulating short circuit B7 at the bottom through a threaded buckle.

[0016] 7. Figure 1 The medium-short insulating short circuit B7 provides an equipotential insulating path for the signal emitter B9 and the signal emitter C8, so that the magnetic fields of the signal emitter B6 and the signal emitter C8 repel each other when they are equipotential after power is applied, forming a nearly flat current shape near the short insulating short circuit B6. This current is forced into the formation and flows to the adjacent casing 18. The lower part of the short insulating short circuit B6 is connected to the emitter C8 by a threaded connection.

[0017] 8. Figure 1 When the middle signal emitter C8 is energized, an equipotential electric field is generated. The electric field flows in the stratum to generate a magnetic field. The signal emitter C8 is connected to the short insulating short-circuit C9 at the bottom through a threaded buckle.

[0018] 9. Figure 1 The purpose of the medium-short insulating short circuit C9 is to isolate the signal emitter C8 from the lower electric rotating device 10 to prevent the current on the signal emitter C9 from flowing to the electric rotating device 10. The short insulating short circuit C9 is connected to the lower electric rotating device 10 through a threaded connection.

[0019] 10. Figure 1The central electric rotating device 10 houses a DC motor, which, controlled from the ground, drives the lower measuring instrument in circular rotation. Adjusting the axial position of the magnetic measurement short circuit 12 allows the system to receive magnetic signals from different locations, maintaining the maximum magnetic measurement signal. The lower portion of the electric rotating device 10 is connected to the gyro short circuit 11 via a threaded connection.

[0020] 11. Figure 1 The middle gyro short circuit 11 is used to measure the parameters such as the well inclination, azimuth, tool face, etc. of the current borehole where the system is located, and provide accurate attitude data for subsequent position calculation. The lower part of the gyro short circuit 11 is connected to the magnetic measurement short circuit 12 through a threaded buckle.

[0021] 12. Figure 1 In this system, the medium magnetic measurement short circuit 12 receives magnetic signals emitted by the casing through its internal high-sensitivity fluxgate sensor, which is then processed and transmitted to the surface. The lower portion of the magnetic measurement short circuit 12 is connected to the weight rod 13 via a threaded buckle.

[0022] Figure 2 This short-circuit magnetic measurement system includes an X-axis fluxgate sensor 1, a Y-axis fluxgate sensor 2, a Z-axis fluxgate sensor 3, a filter board 4, a power board 5, an MCU board 6, a modulation circuit board 7, and a metal frame 8. When powered on, the three fluxgate sensors transmit the collected signals through the filter board 4 to the MCU board 6, and then through the modulation circuit 7 to the ground. Figure 2 When the fluxgate is installed, the X-axis fluxgate sensor 1 is spaced a mm (a>0 mm) from the axis, the Y-axis fluxgate sensor 2 is spaced a mm (a>0 mm) from the axis, and the Z-axis fluxgate sensor (3) is on the axis. The design layout of the fluxgate offset axis provides the necessary physical structure for the magnetic measurement model and algorithm, increases the sensitivity and accuracy of the magnetic measurement, and the accuracy of the calculation result can be reversely verified by the fluxgate offset axis distance.

[0023] Figure 3 The top view of the algorithm derivation for X-axis fluxgate sensor 1 and Y-axis fluxgate sensor 2 is shown. Figure 3 In the figure, P is the point on the axis of the well casing 18 to be measured, O is the intersection of the positive drilling axis and the plane connecting the midpoints of the X-axis fluxgate sensor 1 and the Y-axis fluxgate sensor 2, the X-axis fluxgate sensor 1 and the Y-axis fluxgate sensor 2 are arranged symmetrically, the distance between the X-axis fluxgate sensor 1 and the center is a (designed to be a>0 mm), the lateral component of the X-axis fluxgate sensor 1 is H1, the lateral component of the Y-axis fluxgate sensor 2 is H3, the radial component of the X-axis fluxgate sensor 1 is H2, and the radial component of the Y-axis fluxgate sensor 2 is H4. The angle between the line connecting the X-axis fluxgate sensor 1 and the Y-axis fluxgate sensor 2 and PO is A, and the distance between PO and PO is R.

[0024] Assuming a<<R, the angles formed by P on the X-axis fluxgate sensor 1 and the Y-axis fluxgate sensor 2 are equal, denoted as α. The lateral components of the magnetic field generated by the current in the X-axis fluxgate sensor 1 and the Y-axis fluxgate sensor 2 are respectively:

[0025]

[0026] According to the law of sine, we have

[0027]

[0028] Therefore,

[0029]

[0030] Similarly,

[0031]

[0032]

[0033] After finishing, we can get:

[0034]

[0035] A=arctan4((H2+H4),(H1+H3))

[0036] In actual measurement, multiple measurements can be performed, and then the least squares method can be used to fit the measurement to improve the measurement accuracy. Suppose there are n measurements, and the result of the i-th measurement is:

[0037] A i =arctan4((H 2i +H 4i ),(H 1i +H 3i ))

[0038]

[0039] but

[0040]

[0041] Combining the azimuth A and distance R calculated above with the well inclination, azimuth, tool face and other attitude data measured by the gyroscope, the exact position of the casing relative to the adjacent well casing can be accurately located.

[0042] 13. Figure 1 The middle weight rod 13 is used to increase the weight of the system itself to prevent the mud from being too heavy and encountering resistance when the system is lowered by gravity.

[0043] 14. Figure 1The ground data processor 14 communicates with the underground measuring instrument through an armored cable 17, and the data collected by the underground magnetic measuring instrument 12 and the gyroscope 11 are decoded and re-encoded and uploaded to the computer 16 for solution.

[0044] 15. Figure 1 The medium current injector 15 is a unit that provides current injection from the ground to the underground. It is connected to the underground signal transmitter and signal receiver through the armored cable 17 and can adjust the current injection size in real time according to the formation resistivity.

[0045] 16. Figure 1 The computer 16 calculates the data sent by the data processing instrument through a specific model algorithm to obtain the data required for the project.

[0046] 17. Figure 1 The medium armored cable 17 is a key bridge for information exchange between ground equipment and underground measuring instruments, and plays the role of carrying and transmitting signals and current.

[0047] 18. Figure 1 The adjacent well casing 18 is the ferromagnetic object to be measured in this measurement system. Current 19 flows through the casing after current injection. According to the Biot-Saffar law, the adjacent well casing 18 generates a disc-shaped magnetic field. The magnetic measurement short circuit 12 receives the magnetic field generated by the adjacent well casing 18 and calculates the distance R and relative orientation A between the adjacent well casing 18 and the magnetic measurement short circuit 12.

[0048] 19. Figure 1 The medium current 19 is an indication of the current flowing through the casing 18 of the adjacent well. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following Figure 1 The implementation method of the present invention is further described in detail. Figure 1The downhole measuring instrument string shown is lowered to the location to be measured via an armored cable. After the instrument is stationary, a dedicated data processing instrument 16 is started to first measure the attitude data of the measuring instrument in the downhole borehole via a gyro inclinometer 11. Then, a current injector 15 is started to inject current into signal emitter A4, signal emitter B6, and signal emitter C8 via an armored cable 17. Based on the principle of equipotential magnetic field repulsion, the current is squeezed into the formation via short-insulated short-circuits 5, 7, and 9, and tangent to the casing in the formation, causing the current to flow into the casing. The current 19 then flows back to the signal receiving electrode 2 through the casing. According to Biot-Savart's law, when current flows through the casing, it generates a magnetic field. This magnetic field is captured by the measurement system's magnetic receiving short circuit 12. The magnetic measurement short circuit then filters and modulates the received magnetic signal and transmits it to the surface data processor 14. The data processor 14 transmits the processed data to the computer 16, which then calculates the distance R and orientation A of the casing relative to the measurement point based on a magnetic measurement model algorithm. After a set of data measurements are completed, the electric rotation device 10 is activated at the same well depth, rotating the measuring instrument radially along the borehole by one tool face, changing the angle A between the line connecting the X-axis fluxgate sensor 1 and the Y-axis fluxgate sensor 2 and the PO. Magnetic signal measurement and calculation are then continued. By repeatedly changing the angle A through the electric rotation device 10, magnetic signals from adjacent wells 18 at different locations are received. The acquired magnetic signals are then fitted using the least squares method to improve the final measurement accuracy.

[0050] After the measurement is completed, the current injector 15 and the dedicated data processor 16 are turned off, and the downhole instrument string is lifted to the surface through the armored cable 17. According to the measured relative position and distance of the adjacent well casing 18 relative to the magnetic measurement short circuit 12, the construction personnel arrange the next drilling construction plan.

Claims

1. A magnetic ranging system for casing current injection near a well, the system comprising a surface device and an underground device, wherein the surface device mainly comprises a special data processor connected to an armored cable, a current injector connected to the armored cable, and a computer connected to the data processor. The underground measuring device mainly comprises a bridle, a current receiving electrode connected to the bridle, a long insulation short circuit connected to the current receiving electrode, a current emitter A connected to the long insulation short circuit, a short insulation short circuit A connected to the current emitter A, a current emitter B connected to the short insulation short circuit A, a short insulation short circuit B connected to the current emitter B, a current emitter C connected to the short insulation short circuit B, a short insulation short circuit C connected to the current emitter C, an electric rotating device connected to the short insulation short circuit C, a gyroscope connected to the electric rotating device, a magnetic measurement short circuit connected to the gyroscope, and a weighting rod connected to the magnetic measurement short circuit. The armored cable in the system is a connecting component that provides load bearing and signal transmission for ground and underground devices. The well casing in the system is the underground ferromagnetic object to be measured and located.

2. The system according to claim 1, characterized in that The magnetic measurement short circuit includes two X-axis fluxgate sensors and a Y-axis magnetic measurement sensor installed in a radially symmetrical layout, and a centrally installed Z-axis fluxgate sensor. The magnetic measurement short circuit also includes a signal filter board, a power supply board, an MCU board, a signal modulation board and a metal frame.

3. The system according to claim 2, wherein the calculation algorithm is derived based on the layout of the three fluxgate sensors in the magnetic measurement short circuit, and the direction A and distance R of the magnetic measurement short circuit relative to the adjacent well casing are calculated based on the algorithm.

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