A probe structure of a nuclear magnetic resonance logging tool while drilling

Abstract

The present invention belongs to the technical field of logging equipment, and relates to a probe structure of a nuclear magnetic resonance logging instrument while drilling, including a core shaft 1 and a core shaft 2 which are sealed and connected; the core shaft 1 and the core shaft 2 are symmetrically installed with a soft magnetic skeleton, a magnet fixing shaft, a core shaft centering block, a spring washer, a fixing nut, a locking nut 1, a threading terminal fixing plate and a locking nut 2 with the connection point as the center; two soft magnetic skeletons are symmetrically sleeved on the core shaft 1 and the core shaft 2, and a short radio frequency shielding layer and a radio frequency shielding layer are installed on the soft magnetic skeleton; two magnet shells are symmetrically installed, one end is connected to the anti-wear sleeve, and the other end is connected to the pressure balance device and the tuning device respectively. The present invention has a reasonable sealing structure and wiring structure, and the overall structure has the advantages of high temperature resistance, high pressure resistance, corrosion resistance, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of well logging equipment and relates to a probe structure of a while-drilling nuclear magnetic resonance logging instrument. Background Art

[0002] Compared with cable logging, NMR logging while drilling can detect formation parameters when mud has not penetrated the formation or has penetrated very shallowly, which can provide more accurate data for formation evaluation; it can realize total porosity measurement independent of lithology and accurately analyze formation physical properties; the design of low-gradient magnetic field makes the identification of light fluids simpler; real-time data transmission and processing are conducive to making adjustments at any time; real-time porosity distribution can accurately analyze whether the low-resistivity reservoir is caused by mud, bound water or capillary bound water; when drilling into gas layers or condensate gas layers with low porosity, hydrogen index correction is required, and the distribution of T2 spectrum can be used to determine the approximate lithology and pore structure of the formation; when logging while drilling, the porosity distribution and T2 spectrum measured in real time can be used for horizontal well guidance, etc.

[0003] At present, the technologies of nuclear magnetic resonance logging while drilling turbine generator, magnet, algorithm, electronic circuit and related software are relatively mature, and the probe is the main part of polarizing the formation, transmitting radio frequency pulses and receiving signals, so the main goal is to solve the probe structure of nuclear magnetic resonance logging while drilling instruments. The existing technology only provides a general layout method, and does not propose a specific achievable structure for the complex downhole environment and the actual implementation of nuclear magnetic resonance logging while drilling. It also does not consider that the large buckling torque before going down the well should not damage the internal structure such as the magnet. The high temperature and high pressure environment, corrosion, bending moment, torque, drill pipe column pressure and vibration in the downhole will cause the probe to fail, and no reasonable wiring method and sealing structure are proposed. Summary of the invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the present invention proposes a probe structure of a while-drilling nuclear magnetic resonance logging instrument, which has a reasonable mechanical structure and protects the internal structure at the same time. While realizing the target magnetic field measurement, it has a reasonable sealing and wiring structure, can adapt to the complex while-drilling nuclear magnetic resonance logging environment, and finally realizes while-drilling nuclear magnetic resonance logging.

[0005] The technical solution of the present invention to solve the above problem is: a probe structure of a nuclear magnetic resonance logging while drilling, which is special in that:

[0006] It includes a mandrel 1 and a mandrel 2,

[0007] The mandrel 1 and the mandrel 2 are locked together by mandrel bolts and are sealed;

[0008] The core shaft 1 and the core shaft 2 are symmetrically installed with a soft magnetic skeleton, a magnet fixing shaft, a core shaft centering block, a spring washer, a fixing nut, a locking nut 1, a threading terminal fixing plate and a locking nut 2 with the connection point as the center;

[0009] Two soft magnetic skeletons are symmetrically sleeved on the core shaft 1 and the core shaft 2, one end of the two soft magnetic skeletons are connected, and the other end is respectively connected to the main magnet, the large hole inside the soft magnetic skeleton is connected to the core shaft 1 through the transition cabin, the small hole is connected to the core shaft 1 and the core shaft 2, the step hole at the large end face is connected to the magnet fixed shaft, the large outer diameter step of the soft magnetic skeleton is connected to the magnet shell and is connected to the anti-wear sleeve by the key three guide, and a short radio frequency shielding layer and a radio frequency shielding layer are installed on the small outer diameter step of the soft magnetic skeleton; soft magnets and a soft magnetic buffer block 1 are installed outside the radio frequency shielding layer; the short radio frequency A soft magnetic buffer block assembly is installed outside the shielding layer; the soft magnetic sleeve is mounted on the outside of the radio frequency shielding layer; the antenna part is mounted on the outside of the soft magnetic, and both ends are sealed and connected to the anti-wear sleeve respectively; the anti-wear shell is mounted on the outside of the antenna part and fixedly connected to the anti-wear sleeve; the magnet fixing axis is symmetrically installed and respectively mounted on the core shaft one and the core shaft two, the main magnet is fixed on the outside, one end is connected to the soft magnetic skeleton, and the other end is mounted with a main magnet buffer block; the main magnet buffer block is fixed to the magnet fixing axis by a magnet fixing axis nut; the relay fixing frame is mounted on the core shaft one.

[0010] The two magnet shells are installed symmetrically, one end of which is connected to the anti-wear sleeve, and the other end is respectively connected to the pressure balance device and the tuning device; the tuning device includes a tuning drill collar, and the pressure balance device includes a pressure balance cabin; a threading terminal is installed inside the magnet shell; the pressure balance cabin is sealed and connected to the magnet shell, one end of the core shaft is installed in the tuning drill collar, and the other end of the core shaft is installed in the pressure balance cabin.

[0011] Furthermore, the core shaft one and the core shaft two are provided with mud channels, and the mud channels are respectively connected with the mud channels inside the tuning drill collar and the mud channels in the pressure balance chamber. There is a transition chamber at the connection between the core shaft one and the core shaft two, and there is a pin seal on the transition chamber to realize the later installation of components. There is a wire groove on the outside of the transition chamber. The core shaft one and the core shaft two are respectively processed with a sealing platform stage and a threaded platform stage, and the sealing platform stage is installed with a seal seven.

[0012] Furthermore, the tuning drill collar is provided with an oil injection sealing nozzle, and a tuning cavity is symmetrically arranged, a tuning circuit board is installed inside the tuning cavity, and a tuning cabin cover is installed on the tuning cavity.

[0013] Furthermore, the pressure balancing housing is processed with an oil filling hole for installing an oil outlet sealing nozzle, the pressure balancing housing has a piston hole and a mud channel inside, and the piston hole is provided with a pressure balancing piston, a spring, a pressure balancing spring seat 1 and a pressure balancing spring seat 2.

[0014] The pressure balance spring seat 2 is fixed in the piston hole, the pressure balance piston is fixedly connected to the pressure balance spring seat 1, the spring sleeve is arranged on the pressure balance spring seat 1 and the pressure balance spring seat 2, and the spring is fixed on the steps of the pressure balance spring seat 1 and the pressure balance spring seat 2 by pins, the pressure balance spring seat 1 is provided with a sealing groove, the sealing groove is provided with a sealing member 3, and the pressure balance spring seat 2 is fixed to the pressure balance housing by a fixing screw 1;

[0015] The sealing plug is used to seal the piston hole. A mud channel is provided on the sealing plug and is connected to the mud channel of the pressure balance housing.

[0016] Furthermore, the relay fixing frame is provided with relay mounting grooves, and the relay mounting grooves are evenly distributed along the circumference.

[0017] Furthermore, the anti-wear sleeve is provided with a threaded hole for fixing the anti-wear shell, and the anti-wear sleeve is provided with a sealing groove for installing a sealing member 8.

[0018] Furthermore, the magnet housing has a conical step inside for limiting the position with the core shaft centering block; and an overflow valve is installed on the piston hole of the magnet housing.

[0019] Furthermore, the threading terminal and the threading terminal fixing plate are both provided with corresponding threading holes, and the threading terminal is provided with a key slot for installing key seven.

[0020] Furthermore, a groove and a sealing groove are provided on the outer wall surface of the pressure balancing piston, the groove is filled with grease, and a sealing member 4 is installed in the sealing groove.

[0021] Furthermore, the soft magnetic buffer block assembly is composed of three soft magnetic buffer blocks, which are connected in the middle by ordinary non-magnetic pins. The soft magnetic buffer block assembly has threading holes, which are connected to the threading holes on the soft magnetic skeleton.

[0022] Advantages of the present invention:

[0023] 1) The probe structure of the nuclear magnetic resonance logging instrument while drilling provided by the present invention can be used in conjunction with existing power generation devices, electronic circuits and corresponding software to achieve polarization, pulse emission and nuclear magnetic signal collection of the target layer under a predetermined magnetic field while drilling. The magnetic field design, structural design and material selection mainly rely on finite element calculations, and the magnetic field strength and uniformity are continuously adjusted to achieve the design purpose; the design of the antenna part mainly refers to parameters such as magnetic field gradient and voltage, and is buried in fiberglass, and is matched with anti-wear sleeves and anti-wear shells to meet the requirements of logging while drilling; it is proposed to give the wiring design of electronic components such as tuning capacitors and relays based on the designed pulse frequency and other parameters; the downhole working environment is analyzed and designed to have a reasonable mechanical structure, wiring method and a pressure regulating device to ensure the normal operation of magnets, electronic components, etc. while drilling.

[0024] 2) The probe structure of the nuclear magnetic resonance logging instrument while drilling provided by the present invention can realize the detection of formation information while drilling at sea and on land, and feedback the downhole nuclear magnetic resonance signal.

[0025] 3) The probe structure of the NMR logging instrument while drilling provided by the present invention realizes logging while drilling in deep wells, ultra-deep wells, high temperature and high pressure, vibration and other environments. The present invention systematically designs the overall layout, sealing and bearing components, and proposes a reasonable structural layout from the aspects of material selection and force analysis.

[0026] 4) The probe structure of the nuclear magnetic resonance logging instrument while drilling provided by the present invention can shield the interference noise in the harsh working environment where the signal is weak and the background noise is relatively large during logging while drilling.

[0027] 5) The probe structure of the NMR logging instrument while drilling provided by the present invention has an external thread of the probe that is consistent with the existing drill pipe thread, ensuring accurate docking of the universal drill tool tapered thread; the internal mud channel has a reasonable transition in size to ensure smooth flow of drilling mud.

[0028] 6) The probe structure of the NMR logging instrument while drilling provided by the present invention has a pressure balancing part which can ensure that the electronic components and magnets arranged in the probe are adjusted to a suitable internal temperature and pressure environment according to temperature, pressure, etc.; the pressure balancing part can also change the stroke, shape and size according to actual needs, combined with mechanical parameters such as strength and stiffness, so as to balance and adjust the internal and external pressures.

[0029] 7) The probe structure of the NMR logging instrument while drilling provided by the present invention adopts a magnet layout in which the main magnet is symmetrical and the soft magnet is in the middle. The main magnet is matched with a non-magnetic buffer device, and the soft magnet is matched with a non-magnetic pad. The special high-temperature preparation glue ensures the rigidity while also having the buffering property. The finite element calculation is performed on the design of the intensity, uniformity and gradient of the magnetic field, and then the magnet part is optimized, which not only meets the magnetic field requirements, but also meets the rationality of the overall structure.

[0030] 8) The probe structure of the NMR logging instrument while drilling provided by the present invention, the antenna selection embedding method, the wear-resistant shell, and the symmetrical wear-resistant sleeve design ensure that the antenna part has sufficient wear resistance and bending resistance, which can meet the requirements of transmitting radio frequency pulses and receiving signals during rotary drilling.

[0031] 9) The probe structure of the NMR logging instrument while drilling provided by the present invention has erosion resistance inside the core shaft, and the symmetrical arrangement of the core shaft and the ingenious combination of the centering block, spring washer, fixing nut and anti-slip nut have buffering, centering and tensile and compressive resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is an assembly schematic diagram of the present invention;

[0033] Figure 2 It is a schematic diagram of assembly and disassembly 1 of the present invention;

[0034] Figure 3 It is a schematic diagram of assembly and disassembly 2 of the present invention;

[0035] Figure 4 It is a schematic diagram of assembly and disassembly 3 of the present invention;

[0036] Figure 5 It is a schematic diagram of assembly and disassembly 4 of the present invention;

[0037] Figure 6 It is a schematic diagram of the simulation analysis of the magnet strength and uniformity of the present invention;

[0038] Figure 7 It is an overall three-dimensional exploded schematic diagram of the present invention;

[0039] Figure 8 It is a schematic diagram of the explosion of the pressure balance part of the present invention;

[0040] Fig. 9 It is a schematic diagram of the position of the overflow valve of the present invention.

[0041] Tuning drill collar 1, seal six 2, tuning hatch 3, oil injection seal 4, magnet housing 5, key one 6, seal one 7, threading terminal fixing plate 8, seal two 9, locking nut two 10, locking nut one 11, key two 12, fixing nut 13, mandrel centering block 14, mandrel one 15, threading terminal 16, magnet fixing shaft 17, magnet fixing shaft nut 18, main magnet buffer block 19, main magnet 20, screw 21, anti-wear sleeve 22, soft magnetic buffer block assembly 23, soft magnetic buffer block one 24, short RF shielding layer 25, soft magnet 26, antenna part 27, anti-wear housing 28, key three 2 9. Seal eight 30. Soft magnetic skeleton 31. Key four 32. Relay fixing frame 33. Key six 34. RF shielding layer 35. Pin seal 36. Seal seven 37. Mandrel bolt 38. High temperature tape 39. Mandrel two 40. Key five 41. Anti-wear housing screw 42. Oil outlet sealing nozzle 43. Seal 44. Pressure balance spring seat two 45. Seal three 46. Spring 47. Pressure balance spring seat one 48. Pressure balance piston 49. Seal five 50. Sealing plug 51. Pressure balance housing 52. Fixing screw one 53. Spring washer 54. Fixing screw two 55. Overflow valve 56. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0043] Since the working conditions of LWD in deep wells, ultra-deep wells and offshore oil fields are relatively complex, the shortcomings of the current LWD NMR LWD probe structure design have hindered the development of this technology. Therefore, the present invention proposes a reasonable NMR LWD probe structure that is consistent with the current supporting technology.

[0044] See also Figures 1 to 9 A probe structure of a nuclear magnetic resonance logging instrument while drilling, comprising a tuning drill collar 1, an oil injection sealing nozzle 4, a tuning hatch 3, a main magnet 20, a soft magnet 26, an antenna part 27, a magnet fixing shaft 17, a relay fixing frame 33, an anti-wear sleeve 22, an anti-wear shell 28, a pin seal 36, a mandrel 15, a key 16, a key 2 12, a key 3 29, a key 4 32, a key 5 41, a key 6 34, a key 7 12, a relief valve 56, a mandrel 2 40, a seal 1 7, a seal 2 9, and a seal. Six 2, seal seven 37, seal eight 30, core shaft bolt 38, magnet fixing shaft nut 18, pressure balance part, oil outlet sealing nozzle 43, magnet housing 5, core shaft centering block 14, fixing nut 13, locking nut one 11, locking nut two 10, spring washer 54, threading terminal 16, threading terminal fixing plate 8, soft magnetic skeleton 31, soft magnetic buffer block one 24, soft magnetic buffer block assembly 23, main magnet buffer block 19, short RF shielding layer 25, RF shielding layer 35.

[0045] The core shaft 15 is connected to the core shaft 2 40, guided by the key 5 41 and locked together by the core shaft bolt 38, and is a sealed connection, on which the pin seal 36 is installed. The soft magnetic skeleton 31, the magnet fixing shaft 17, the core shaft centering block 14, the spring washer 54, the fixing nut 13, the locking nut 11, the wire terminal fixing plate 8 and the locking nut 2 10 are symmetrically installed on the core shaft 15 and the core shaft 2 40.

[0046] The end of the mandrel 15 is loaded with a tuning drill collar 1, and the end of the mandrel 2 40 is loaded with a pressure balance cabin 52, which is guided by a key 4 32 and installed on the soft magnetic skeleton 31, and a key 6 34 is installed on the mandrel 15; the two soft magnetic skeletons 31 are symmetrically sleeved on the mandrel 15 and the mandrel 2 40, one end of the two soft magnetic skeletons 31 is connected, and the other end is connected to the main magnet 20, the large hole inside the soft magnetic skeleton 31 is connected to the mandrel 15 through the transition cabin, the small hole is connected to the mandrel 15 and the mandrel 2 40, and the step hole at the large end surface is connected to the magnet The fixed shaft 17 is connected, the soft magnetic skeleton 31 is connected to the magnet housing 5 at the large outer diameter step and is connected to the anti-wear sleeve 22 by the key three 29, and the short RF shielding layer 25 and the RF shielding layer 35 are installed on the small outer diameter step of the soft magnetic skeleton 31; the soft magnetic 26 and the soft magnetic buffer block 24 are installed outside the RF shielding layer 35; the soft magnetic buffer block assembly 23 is installed outside the short RF shielding layer 25; the soft magnetic 26 is sleeved on the outside of the RF shielding layer 35; the antenna part 27 is sleeved on the outside of the soft magnetic 26 , and the two ends are respectively sealed and connected with the anti-wear sleeve 22; the anti-wear shell 28 is installed on the outside of the antenna part 27 and is fixedly connected with the anti-wear sleeve 22; the magnet fixing shaft 17 is symmetrically installed, and is respectively mounted on the core shaft 15 and the core shaft 2 40, and the main magnet 20 is fixed on the outside, one end is connected to the soft magnetic skeleton 31, and the main magnet buffer block 19 is installed on the other end; the main magnet buffer block 19 is fixed to the magnet fixing shaft 17 by the magnet fixing shaft nut 18; the relay fixing frame 33 is installed on the core shaft A key 6 34 is provided on the upper surface of the magnet housing 5; the magnet housing 5 is symmetrically installed, one end of which is connected to the anti-wear sleeve 22, and the other end is respectively connected to the pressure balancing device and the tuning device; one end of the tuning drill collar 1 is guided by a key 6 and is respectively sealed and connected to the core shaft 1 and the magnet housing 5, and a tuning cabin cover 3 is installed thereon; the threading terminal 16 is guided by a key 2 12 and installed inside the magnet housing 5; one end of the pressure balancing part is guided by a key 6 and installed on the magnet housing 5 and is sealed, and the inner hole is sealed and connected to the core shaft 2 40.

[0047] Furthermore, mud channels are provided inside the core shaft 15 and the core shaft 2 40, and the mud channels are respectively connected with the mud channel inside the tuning drill collar 1 and the mud channel of the pressure balance part. A transition chamber is provided at the connection between the core shaft 15 and the core shaft 2 40, and a pin seal 36 is provided on the transition chamber, so that components can be installed later. A wire groove is provided outside the transition chamber, and a sealing platform stage and a threaded platform stage are respectively processed on the core shaft 15 and the core shaft 2 40, and a seal 7 37 is installed on the sealing platform stage.

[0048] Furthermore, the tuning drill collar 1 is provided with an oil filling sealing nozzle 4, and a tuning cavity is symmetrically arranged on it, a tuning circuit board is installed inside the tuning cavity, a step is provided at the tuning cavity, a fixed threaded hole is processed on the step, the cavity has a threading hole and an oil hole to the end face position, a centering keyway is processed on the outside, and there are symmetrical keyways and sealing grooves at the sealing step, where a seal 7 is installed, and there is also a sealing groove at the internal sealing step, where a seal 2 9 is installed, and an external tapered thread is processed at the other end.

[0049] Furthermore, the pressure balancing device includes a pressure balancing housing 52, a seal 1 7, a seal 2 9, a seal 3 46, a seal 4, a seal 50, an oil filling sealing nozzle 4, a sealing plug 51, a fixing screw 1 53, a fixing screw 2 55, a fixing screw 3 56, a pin, a pressure balancing piston 49, a spring 47, a pressure balancing spring seat 1 48 and a pressure balancing spring seat 2 45, and the pressure balancing spring seat 2 45 is connected to the pressure balancing housing 52.

[0050] The pressure balancing piston 49 has a threaded hole, and the pressure balancing piston 49 is connected to the pressure balancing spring seat 48 by a fixing screw 55. The pressure balancing piston 49 is provided with a groove filled with grease. The pressure balancing piston 49 is provided with a sealing groove, and a sealing member 46 is installed in the sealing groove.

[0051] The pressure balancing shell 52 has a centering keyway and a fixing threaded hole on the outside, the fixing threaded hole is used to install a fixing screw 53, and has a piston hole, a mud channel, an inner step and a threaded hole for fixing a sealing plug 51 on the inside. The pressure balancing shell 52 is processed with a sealing step, and a sealing groove on the sealing step is used to install a seal 7. The sealing step has a keyway, and the inner step has a sealing groove for installing a seal 9. The pressure balancing shell 52 is processed with an oil filling hole for installing an oil outlet sealing nozzle. The pressure balancing shell 52 has a mud hole, and external mud flows in during drilling to adjust the internal and external pressures to adjust the piston stroke. One end of the pressure balancing shell 52 is processed with an internal tapered thread.

[0052] Further, the spring 47 is sleeved on the pressure balance spring seat 1 48 and the pressure balance spring seat 2 45, and the spring 47 is fixed on the steps of the pressure balance spring seat 1 48 and the pressure balance spring seat 2 45 by pins, and the pressure balance spring seat 1 48 has a sealing groove, and the sealing groove is installed with a sealing member 3 46, see Figure 3 The pressure balance spring seat 2 45 is fixed to the pressure balance housing 52 by a fixing screw 1 53 .

[0053] Furthermore, the sealing plug 51 is used to seal the piston hole. The sealing plug 51 has a mud channel connected to the mud channel of the pressure balance housing 52. The sealing plug 51 has a sealing groove for installing a sealing member 50. The sealing plug 51 has a through hole, which is opposite to the threaded hole of the pressure balance housing 52 and is fixed to the pressure balance housing 52 with a fixing screw 56.

[0054] Furthermore, the tuning hatch cover 3 has a countersunk hole corresponding to the upper threaded hole, which is fixed by ordinary bolts, and the tuning hatch cover 3 has a sealing groove for installing the sealing member 6 2.

[0055] Furthermore, the inner hole of the magnet fixing shaft 17 has a semicircular hole for wiring, the magnet fixing shaft 17 has a threaded hole corresponding to the hole on the soft magnetic skeleton 31 for positioning the screws 21, and the magnet fixing shaft 17 has a threaded section for installing the magnet fixing shaft nut 18.

[0056] Furthermore, the magnet fixing shaft nut 18 is provided with a step hole for positioning with the cylindrical step on the core shaft centering block 14 .

[0057] Furthermore, the mandrel centering block 14 has a threading hole for wiring, and the mandrel centering block 14 has a cylindrical step for positioning with the magnet fixing shaft nut 18 .

[0058] Furthermore, the relay fixing frame 33 is provided with relay mounting grooves, and the relay mounting grooves are evenly distributed along the circumference.

[0059] Furthermore, the soft magnetic buffer block assembly is composed of three blocks, which are connected in the middle by ordinary non-magnetic pins. The soft magnetic buffer block assembly has threading holes that communicate with the threading holes on the soft magnetic skeleton 31.

[0060] Furthermore, the anti-wear sleeve 22 has a threaded hole for fixing the anti-wear shell 28, and the anti-wear sleeve 22 has a sealing groove for installing a sealing member 8 30.

[0061] Furthermore, the magnet housing 5 has a centering keyway for assembly and alignment, and the magnet housing 5 has a conical step inside for limiting the position with the core shaft centering block 14; the magnet housing 5 has a threaded hole for installing the overflow valve 56.

[0062] Furthermore, the threading terminal 16 and the threading terminal fixing plate 8 are both provided with threading holes corresponding to each other, and the threading terminal 16 is provided with a keyway for installing the key 12 .

[0063] The assembly process of the while-drilling nuclear magnetic resonance logging probe structure proposed by the present invention is as follows:

[0064] Use high-temperature special prepared glue to magnetize the main magnet block and cooperate with tooling to bond it into a magnetic ring. After the magnetic ring is cured, it is assembled into a hollow magnetic rod with a columnar structure to complete the preparation of the main magnet 20. The main magnet can choose aluminum nickel cobalt as the permanent magnet material, and then install the main magnet 20 and the main magnet buffer block 19 on the magnet fixing shaft 17 for standby use, and lay high-temperature enameled wire inside the magnet fixing shaft 17. Finally, the above parts are matched with the soft magnetic skeleton 31. The laid high-temperature enameled wire goes through the threading holes inside the soft magnetic skeleton 31 and is fixed with screws 21. Here, the main magnet buffer block 19 can choose non-magnetic material or magnetic conductive material according to the magnetic field requirements. Since we are positioning the gradient field centralized measurement method in this embodiment, the magnetic field strength we mainly use is a gradient field of 100-150 Gauss, and cost saving is also taken into consideration. Therefore, the main magnet buffer block 19 selects micromagnetic material, and the bonding material of the main magnet 20 selects acrylate, high-temperature resin and curing agent.

[0065] The soft magnetic blocks are bonded into a ring shape with a special high-temperature glue, and the ring-shaped soft magnetic is bonded into a column to complete the preparation of the soft magnetic 26. A soft magnetic structure is added between the two main magnets 20 so that the magnetic fields on both sides are pulled to the middle to meet the use range and uniformity of the magnetic field. The soft magnetic acts as a magnetic conductor. In this embodiment, the material selected is neodymium iron boron, and the bonding material of the soft magnetic 26 is selected from acrylate, high-temperature resin and curing agent.

[0066] The antenna designed according to this embodiment has a use range of 60 cm. The coil responsible for signal reception and radio frequency transmission is mainly designed in the form of copper skin and buried inside the fiberglass. Only the connection points are exposed to complete the assembly preparation of the antenna part 27.

[0067] Install the key six 34, key four 32 and pin seal 36 on the core shaft 15, then install the relay fixing frame 33 and the relay, arrange the required high-temperature enameled wire, and finally install this structure into the soft magnetic skeleton 31, and pass the arranged wires through the threading holes of the soft magnetic skeleton 31. The number of relays is related to the number of transmission frequencies. In this embodiment, five transmission frequencies are used, and four relays are used to control the number of connected capacitors. The relays are controlled by the program of the control circuit. During logging, a DC power supply is used as the power source. The DC power supply uses 580 volts, generates a square wave through a power amplifier, and then generates a sine wave through a filter.

[0068] The key five 41, key four 32 and seal seven 37 are installed into the core shaft two 40, and the core shaft two 40 is connected with the core shaft one 15 and fixed with the core shaft bolt 38.

[0069] Furthermore, the soft magnetic buffer block 24, the soft magnetic buffer block assembly 23, the key three 29, the short RF shielding layer 25, the seal eight 30, the RF shielding layer 35 and the anti-wear sleeve 22 are installed on the soft magnetic skeleton 31, and the soft magnetic 26 and the antenna part 27 are installed on the soft magnetic skeleton 31 that has been docked with the core shaft 15; finally, another part of the soft magnetic skeleton 31 is docked with the core shaft 2 40, and while performing the above steps, the wiring of the antenna part, etc. is connected together according to the function.

[0070] Tighten the magnet fixing shaft nut 18, and then install the core shaft centering block 14, spring washer 54, fixing nut 13 and locking nut 11 in sequence, and at the same time install key 7 12 into the threading terminal 16, install the threading terminal fixing plate 8 and install the locking nut 2 10, and at the same time lead the high-temperature enameled wire from the magnet fixing shaft 17 to the core shaft centering block 14 to the threading terminal 16 and finally to the threading terminal fixing plate 8 and install the magnet housing 5.

[0071] Install the seal 1 7, seal 2 9 and key 1 6 into the tuning drill collar 1, and install the seal 6 2 into the tuning hatch 3 at the same time, then fix the tuning hatch 3 to the tuning drill collar 1 with screws, and connect the above parts with the magnet housing 5. The function of tuning is to adjust the resonant frequency. A sine wave will occur when the inductor is added to the capacitor. The inductor is fixed, so changing the capacitor will change the frequency of the sine wave and make the antenna emit. Different capacitors are connected to the LC resonant circuit through relays to generate sine waves of different frequencies. The tuning capacitor and the circuit board are installed in the tuning drill collar 1, and a high-temperature enameled wire is connected to the relay on the relay frame.

[0072] Assemble the pressure balance part, specifically, fix the spring 47 to the pressure balance spring seat 1 48 and the pressure balance spring seat 2 45 with a pin according to the design requirements of the required spring stiffness. At this time, the fixing screw 2 55 has been installed in the pressure balance spring seat 1 48, and then the pressure balance piston 49 with the seal 3 46 installed is connected to the pressure balance spring seat 1 48 with the fixing screw 2 55, and finally fill the groove of the pressure balance piston 49 with high-temperature lubricating silicone grease. At this time, the pressure balance piston part is assembled; the seal 1 7, the seal 2 9 and the key 1 6 are installed into the pressure balance housing 52, and the seal 1 7, the seal 2 9 and the key 1 6 are installed in the pressure balance housing 52. The completed pressure balancing piston part is assembled into the pressure balancing housing 52 and fixed with a fixing screw 53; finally, the pressure balancing part is docked with the magnet housing 5 for installation; it is worth noting that in this embodiment, the pressure balancing housing 52 is made of TC11 for mechanical properties and non-magnetic principles, and the stress concentration position is chamfered during processing; the pressure balancing spring seat 1 48, the pressure balancing piston 49 and the pressure balancing spring seat 2 45 are made of beryllium bronze QBe2 for mechanical properties, non-magneticity and avoiding excessive force with the pressure balancing housing 52; the material of the spring 47 is 50CrVA.

[0073] The above components are installed together, only the oil filling sealing nozzle 4, the oil outlet sealing nozzle 43 and the relief valve 56 are left, and then the opening pressure of the relief valve is adjusted to 5Mpa before being installed on the magnet housing 5. Next, the oil filling sealing nozzle mounting hole and the oil outlet sealing nozzle mounting hole are connected to the circulating oil filling machine, and the vacuum is drawn to test the overall sealing performance of the instrument. After the sealing performance is good, dimethyl silicone oil is injected until the pressure balance piston 49 reaches the predetermined position and stops the oil injection. The oil filling sealing nozzle 4 and the oil outlet sealing nozzle 43 are installed to complete the overall installation. It is worth noting that the seal selected in this embodiment is a fluororubber seal ring with a hardness of 80. The specific sealing size is selected according to the standard. Silicone grease needs to be applied when installing the seal ring, and all threaded structures are coated with thread anti-seizure paste.

[0074] Preferably, in this embodiment, all the keys, main magnet buffer block 19 and screw materials are made of stainless steel 0Cr17Ni4CuNb, which meets the mechanical properties and has no magnetic interference.

[0075] Preferably, the high temperature special prepared glue formula in this embodiment mainly includes metal powder with shielding effect, connected high temperature resin, curing agent and acrylate.

[0076] Preferably, the magnet in this embodiment designed by the finite element electromagnetic simulation method can be calibrated and adjusted by a magnet three-dimensional measuring instrument after preparation.

[0077] Preferably, in this embodiment, the tuning drill collar 1, the oil injection sealing nozzle 4, the tuning hatch 3, the magnet fixing shaft 17, the relay fixing frame 33, the anti-wear sleeve 22, the core shaft 15, the overflow valve 56, the core shaft 40, the core shaft bolt 38, the magnet fixing shaft nut 18, the oil outlet sealing nozzle 43, the magnet housing 5, the core shaft centering block 14, the fixing nut 13, the locking nut 11, the locking nut 2 10, the spring washer 54, the threading terminal 16, the threading terminal fixing plate 8 and the soft magnetic skeleton 31 are all made of TC11; the soft magnetic The material of the buffer block 24 and the soft magnetic buffer block assembly 23 is polytetrafluoroethylene, which is a high-temperature resistant and non-magnetic material; the material of the short RF shielding layer 25 and the RF shielding layer 35 is C12000 with shielding performance; it is worth noting that in this embodiment, welds are left between the tuning drill collar 1 and the magnet housing 5, the magnet housing 5 and the anti-wear sleeve 22, and the magnet housing 5 and the pressure balance housing 52, which are finally welded and fixed; it is worth noting that in this embodiment, the two main magnets are arranged in N levels relative to each other; the material of the anti-wear housing 28 is epoxy resin.

[0078] Preferably, from room temperature 25°C to downhole environment 175°C, the stroke of the pressure balance piston 49 due to thermal expansion of silicone oil can be calculated according to the volume expansion of the liquid from temperature t1 to t2 using the following formula to adjust the size or stroke as needed:

[0079] V t2 =Vt1 [1+β(t2-t1)]

[0080] Where V t1 、V t2 --------—The volume of a single liquid at temperatures t1 and t2;

[0081] β—---------The average volume expansion coefficient of a single liquid from temperature t1 to t2.

[0082] B.2 Calibration process of NMR logging probe while drilling

[0083] Place the assembled probe in the formation simulator in a signal-shielded environment, and then connect it to the existing LWD electronic circuit. The electronic circuit is connected to the console computer, and the logging debugging software is opened. The instrument is powered on to start measuring gain, b1, and also to test noise, ringing, high voltage, DC low voltage, etc. If there are parameters that do not meet the logging requirements, analyze various reasons and debug the probe until all parameters meet the requirements.

[0084] The docking process of the NMR logging probe structure while drilling proposed by the present invention and other downhole instruments is as follows:

[0085] The NMR logging probe while drilling is transported to the destination in a special box. Both ends of the NMR logging probe while drilling have NC tapered threads. The upper end can be connected to the electronic circuit short-section drill collar and the power generation device; the lower part is connected near the drill bit, and the make-up torque is 3KN.m. In case of special downhole situations such as drill stuck, downhole salvage tools can be used, which can withstand the impact load of 250T tension or jar.

[0086] In summary, the probe structure of the NMR logging while drilling proposed in the present invention can be used with the NMR logging while drilling electronic circuit, logging software and the NMR generator while drilling in the complex formation environment of deep wells, ultra-deep wells or offshore drilling. It has the functions of polarizing formation fluids, providing a reasonable gradient magnetic field and adjusting the internal and external pressures of the probe. Compared with the existing NMR logging while drilling scheme, it has the advantages of high temperature resistance, high pressure resistance, corrosion resistance and impact resistance. The overall structure is compatible with the existing downhole drilling tools, reducing the cost of NMR logging; it also lays a solid foundation for further research on advanced algorithms, magnetic field structures and accurate understanding of formation information of NMR logging while drilling.

[0087] The above descriptions are merely embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related system fields, are also included in the protection scope of the present invention.

Claims

1. A probe structure of a nuclear magnetic resonance logging while drilling tool, characterized in that: It includes a first mandrel (15) and a second mandrel (40), The core shaft 1 (15) and the core shaft 2 (40) are locked together by a core shaft bolt (38) and are sealed; The core shaft 1 (15) and the core shaft 2 (40) are symmetrically mounted with a soft magnetic skeleton (31), a magnet fixing shaft (17), a core shaft centering block (14), a spring washer (54), a fixing nut (13), a locking nut 1 (11), a threading terminal fixing plate (8) and a locking nut 2 (10) respectively with the connection point as the center; Two soft magnetic skeletons (31) are symmetrically sleeved on the core shaft 1 (15) and the core shaft 2 (40). One end of the two soft magnetic skeletons (31) is connected to each other, and the other end is respectively connected to the main magnet (20). The large hole inside the soft magnetic skeleton (31) is connected to the core shaft 1 (15) through a transition cabin, and the small hole is connected to the core shaft 1 (15) and the core shaft 2 (40). The step hole at the large end surface is connected to the magnet fixing shaft (17). The large outer diameter step of the soft magnetic skeleton (31) is connected to the magnet housing (5) and is connected to the anti-wear sleeve (22) through the key 3 (29). A short radio frequency shielding layer (25) and a radio frequency shielding layer (35) are installed on the small outer diameter step of the soft magnetic skeleton (31); the soft magnet (26) and a soft magnetic buffer block 1 (24) are installed outside the radio frequency shielding layer (35); the short radio frequency shielding A soft magnetic buffer block assembly (23) is installed outside the layer (25); the soft magnetic (26) is sleeved on the outside of the radio frequency shielding layer (35); the antenna part (27) is sleeved on the outside of the soft magnetic (26), and the two ends are respectively sealed and connected to the anti-wear sleeve (22); the anti-wear shell (28) is installed on the outside of the antenna part (27) and is fixedly connected to the anti-wear sleeve (22); the magnet fixing shaft (17) is symmetrically installed, sleeved on the core shaft one (15) and the core shaft two (40), respectively, the main magnet (20) is fixed on the outside, one end is connected to the soft magnetic skeleton (31), and the other end is installed with the main magnet buffer block (19); the main magnet buffer block (19) is fixed to the magnet fixing shaft (17) by the magnet fixing shaft nut (18); the relay fixing frame (33) is installed on the core shaft one (15); The two magnet housings (5) are symmetrically installed, one end of which is connected to the anti-wear sleeve (22), and the other end of which is respectively connected to the pressure balancing device and the tuning device; The tuning device comprises a tuning drill collar (1), and the pressure balancing device comprises a pressure balancing housing (52); A wire terminal (16) is installed inside the magnet housing (5); the pressure balance housing (52) is sealed and connected to the magnet housing (5); the end of the first mandrel (15) is installed in the tuning drill collar (1), and the end of the second mandrel (40) is installed in the pressure balance housing (52).

2. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 1, characterized in that: The core shaft 1 (15) and the core shaft 2 (40) are provided with mud channels inside, and the mud channels are respectively connected with the mud channels inside the tuning drill collar (1) and the mud channels inside the pressure balance housing (52). A transition chamber is provided at the connection between the core shaft 1 (15) and the core shaft 2 (40), and a pin seal (36) is provided on the transition chamber, so that components can be installed later. A wire groove is provided outside the transition chamber. The core shaft 1 (15) and the core shaft 2 (40) are respectively processed with a sealing platform stage and a threaded platform stage, and the sealing platform stage is installed with a sealing component 7 (37).

3. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 2, characterized in that: The tuning drill collar (1) is provided with an oil injection sealing nozzle (4), and has symmetrically arranged tuning cavities, a tuning circuit board is installed inside the tuning cavity, and a tuning cabin cover (3) is installed on the tuning cavity.

4. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 3, characterized in that: The pressure balancing housing (52) is processed with an oil filling hole for installing an oil outlet sealing nozzle (43). The pressure balancing housing (52) has a piston hole and a mud channel inside. The piston hole is provided with a pressure balancing piston (49), a spring (47), a pressure balancing spring seat 1 (48) and a pressure balancing spring seat 2 (45). The second pressure balancing spring seat (45) is fixed in the piston hole, the pressure balancing piston (49) is fixedly connected to the first pressure balancing spring seat (48), the spring (47) is sleeved on the first pressure balancing spring seat (48) and the second pressure balancing spring seat (45), and the spring (47) is fixed on the steps of the first pressure balancing spring seat (48) and the second pressure balancing spring seat (45) by pins, the first pressure balancing spring seat (48) is provided with a sealing groove, the sealing groove is provided with a sealing member (46), and the second pressure balancing spring seat (45) is fixed on the pressure balancing housing (52) by a fixing screw (53); The sealing plug (51) is used to seal the piston hole. The sealing plug (51) is provided with a mud channel which is connected to the mud channel of the pressure balance housing (52).

5. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 4, characterized in that: The relay fixing frame (33) is provided with relay mounting grooves, and the relay mounting grooves are evenly distributed along the circumference.

6. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 5, characterized in that: The anti-wear sleeve (22) is provided with a threaded hole for fixing the anti-wear shell (28), and the anti-wear sleeve (22) is provided with a sealing groove for installing a sealing member 8 (30).

7. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 6, characterized in that: The magnet housing (5) has a conical step inside for limiting the position of the core shaft centering block (14); and an overflow valve (56) is installed on the piston hole of the magnet housing (5).

8. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 7, characterized in that: The threading terminal (16) and the threading terminal fixing plate (8) are both provided with corresponding threading holes, and the threading terminal (16) is provided with a keyway for installing a key seven (12).

9. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 8, characterized in that: The outer wall surface of the pressure balancing piston (49) is provided with a groove and a sealing groove, the groove is filled with grease, and the sealing groove is provided with a sealing member 4.

10. The probe structure of a nuclear magnetic resonance logging while drilling tool according to claim 9, characterized in that: The soft magnetic buffer block assembly (23) is composed of three soft magnetic buffer blocks, which are connected in the middle by ordinary non-magnetic pins. The soft magnetic buffer block assembly has a threading hole, which is connected to the threading hole on the soft magnetic skeleton (31).

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