Controllable source neutron porosity logging-while-drilling device based on array detector

Abstract

The invention belongs to the technical field of petroleum and natural gas drilling, and discloses a controllable source neutron porosity logging-while-drilling device based on an array detector, the controllable source neutron porosity logging-while-drilling device comprises a drill collar body and a neutron generator, a water hole structure is arranged in the drill collar body, and the neutron generator is arranged in the water hole structure; a plurality of neutron detector assemblies, a main control processing circuit, a modulation-demodulation circuit, a filter circuit, a power supply circuit, a pressure switch and a communication interface are arranged on the drill collar body; the communication interface, the modulation-demodulation circuit, the power circuit, the filter circuit and the main control processing circuit are sequentially connected, the modulation-demodulation circuit is further in communication connection with the main control processing circuit, the main control processing circuit is connected with the neutron generator and the neutron detector assemblies, and the neutron detector assemblies are arranged in an array mode in the circumferential direction of the drill collar body. The space of the drill collar is effectively utilized, the overall length of the device is shortened, the flexible matching adaptability of the device on an operation site is improved, the parts of the device are mutually independent, and the maintenance convenience is also improved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas drilling, and in particular relates to a controllable source neutron porosity logging while drilling device based on an array detector. Background Art

[0002] Compared with cable logging, logging while drilling can obtain more original formation information during the actual drilling of high-angle and long horizontal wells, decide the drilling direction, enhance the ability to identify oil and gas, and increase the oil leakage area, thereby improving the economic benefits of oil and gas exploration and development. It has become the main engineering technology for increasing reserves and production of unconventional oil and gas. Controllable source neutron porosity logging while drilling can obtain formation porosity data in real time, and is an important part of formation evaluation logging while drilling. In addition, this type of device uses a neutron generator to replace the traditional Am-Be neutron source, avoiding the risk of chemical sources falling into the well, and the neutron rays are safe and controllable, friendly to construction personnel and the surrounding environment. It is the future development direction of "green" environmentally friendly logging. At present, it has become an important logging method to achieve "passive" and safe acquisition of formation porosity data in high-angle wells, long horizontal wells and wells with complex working conditions.

[0003] Patent document CN103527181A discloses "a method and instrument for controlled source neutron logging while drilling". Two He-3 tubes are used as long and short source distance He-3 tubes 31 respectively. The detector, neutron generator and acquisition unit are assembled into an electronic instrument structure in sequence by slotting the side wall. The drill collar is radially eccentrically installed inside the drill collar to achieve neutron porosity measurement while drilling. The disadvantages of this implementation method are: the eccentric installation method makes the measurement accuracy of the device susceptible to the influence of the fluctuating borehole clearance in the drilling environment; there is only one set of He-3 tubes as neutron probes, and its counting efficiency is low, and there are no anti-vibration protection measures. As a gas detector, it is susceptible to vibration; the radial installation of all parts leads to a longer drill collar size, which is inconvenient for on-site matching operation. In addition, once the instrument fails, the electronic instrument needs to be completely disassembled, which is complicated to repair. Summary of the invention

[0004] In view of the above problems, the present invention provides a controlled source neutron porosity logging while drilling device based on an array detector, which adopts the following technical solutions:

[0005] A controlled source neutron porosity logging while drilling device based on an array detector comprises a drill collar body and a neutron generator, wherein a water hole structure is arranged in the drill collar body, and the neutron generator is arranged in the water hole structure;

[0006] Among them, a plurality of neutron detector assemblies, a main control processing circuit, a modulation and demodulation circuit, a filter circuit, a power supply circuit, a pressure switch and a communication interface are arranged on the drill collar body; the communication interface, the modulation and demodulation circuit, the power supply circuit, the filter circuit and the main control processing circuit are connected in sequence, the modulation and demodulation circuit is also communicatively connected with the main control processing circuit, the main control processing circuit is connected with the neutron generator and the plurality of neutron detector assemblies, and the plurality of neutron detector assemblies are arranged in a circumferential array along the drill collar body.

[0007] Furthermore, it also includes a lower mud guide sleeve and an upper mud guide sleeve, the lower mud guide sleeve and the upper mud guide sleeve are respectively connected to the two ends of the drill collar body, and the neutron generator is fixed in the water hole structure through the lower mud guide sleeve and the upper mud guide sleeve.

[0008] Furthermore, the neutron generator includes a generator pressure-bearing tube, a generator control circuit short section, a generator voltage-doubling short section, a neutron tube and a generator ion source short section which are sequentially connected from bottom to top, wherein a high-voltage control circuit is arranged in the generator control circuit short section, a voltage-doubling circuit is arranged in the generator voltage-doubling short section, and an ion source circuit is arranged in the generator ion source short section.

[0009] Furthermore, a plurality of the neutron detector assemblies are arranged close to the neutron tube.

[0010] Furthermore, a main control acquisition circuit compartment, a first detector compartment, a second detector compartment, a modulation and demodulation compartment, a pressure switch compartment, a filter compartment, a power supply compartment and a wire passing compartment are arranged outside the drill collar body;

[0011] Among them, the main control acquisition circuit compartment, the first detector compartment, the second detector compartment and the pressure switch compartment are arranged in the middle of the drill collar body, and the modem compartment, the filter compartment, the power supply compartment and the wire passing compartment are arranged in the upper part of the drill collar body.

[0012] Furthermore, the upper portion of the drill collar body is also connected to a protective short drill collar.

[0013] Furthermore, the outer diameter of the middle part of the drill shank body is larger than the diameters of the lower part and the upper part, and the first detector compartment and the second detector compartment are arranged opposite to each other; a neutron detector assembly is arranged in each of the first detector compartment and the second detector compartment, the main control acquisition circuit compartment and the pressure switch compartment are arranged between the first detector compartment and the second detector compartment, and the communication interface is located below the first detector compartment and the second detector compartment.

[0014] Furthermore, the main control processing circuit is arranged in the main control acquisition circuit compartment, the modulation and demodulation circuit is arranged in the modulation and demodulation compartment, the filtering circuit is arranged in the filtering compartment, the power supply circuit is arranged in the power supply compartment, and the pressure switch is arranged in the pressure switch compartment.

[0015] Furthermore, the outer side of the main control acquisition circuit compartment is sealed and connected to the acquisition circuit compartment cover, the outer sides of the first detector compartment and the second detector compartment are respectively sealed and connected to the detector assembly cover plate, the outer side of the modem compartment is sealed and connected to the modem compartment cover, the outer side of the filter compartment is sealed and connected to the filter cover plate, the outer side of the power supply compartment is sealed and connected to the power supply cover plate, and the outer side of the wire passing compartment is sealed and connected to the wire passing cover plate.

[0016] Furthermore, the neutron detector assembly includes a shell, wherein two long-source-distance detector compartments are arranged at the first end of the shell, one short-source-distance detector compartment is arranged at the second end of the shell, three preamplifier circuit compartments are arranged in the middle of the shell, and a shaping identification circuit compartment is also arranged on one side of the short-source-distance detector compartment at the second end of the shell;

[0017] Each of the long source distance detector compartments is provided with a long source distance He-3 tube, the short source distance detector compartment is provided with a short source distance He-3 tube, the shaping and identification circuit compartment is provided with a high voltage power supply module, a low voltage power supply module and a shaping and identification circuit, and each of the preamplifier circuit compartments is provided with a preamplifier circuit.

[0018] Furthermore, each of the long source distance detector compartments is provided with a long source distance disc spring at the end of the long source distance He-3 tube, and the end of each of the long source distance detector compartments is connected to the end face plug; the short source distance detector compartment is provided with a short source distance disc spring at the end of the short source distance He-3 tube, and the end of the short source distance detector compartment is connected to the eight-core connector.

[0019] Furthermore, the outer side of the shaping and identification circuit compartment is sealed and connected to the identification and shaping circuit cover plate, and the outer side of each preamplifier circuit compartment is sealed and connected to an amplifier circuit cover plate.

[0020] Furthermore, the shell, the identification and shaping circuit cover plate and the amplifier circuit cover plate are all made of electrical pure iron.

[0021] Furthermore, in each neutron detector assembly, the low voltage power supply module is connected to one end of the high voltage power supply module, two long source distance He-3 tubes and one short source distance He-3 tube are connected to the other end of the high voltage power supply module, the two long source distance He-3 tubes and one short source distance He-3 tube are respectively connected to the shaping and identification circuit through a preamplifier circuit, and the main control processing circuit is connected to the shaping and identification circuit of each neutron detector assembly.

[0022] Furthermore, the high-voltage control circuit, the voltage multiplier circuit, the neutron tube and the ion source circuit are connected in sequence, and the main control processing circuit is connected to the high-voltage control circuit.

[0023] The present invention also provides a formation porosity measurement method, which is implemented by using the controllable source neutron porosity logging while drilling device based on an array detector, and includes the following steps:

[0024] The main control processing circuit collects 4 long-source-distance counting rates of the long-source-distance He-3 tube and 2 short-source-distance counting rates of the short-source-distance He-3 tube as a set of counting rate data;

[0025] Continuously collect multiple groups of count rate data, and based on the average values ​​of the long source distance count rates and the average values ​​of the short source distance count rates in the multiple groups of count rate data, perform abnormal data screening on the current 4 long source distance count rates and 2 short source distance count rates to obtain the screened long source distance count rates and short source distance count rates;

[0026] The average values ​​of the long source distance counting rate and the short source distance counting rate after screening are calculated respectively, and the formation porosity is determined according to the ratio between the average value of the long source distance counting rate after screening and the average value of the short source distance counting rate after screening.

[0027] Beneficial effects of the present invention:

[0028] 1. The present invention fixes the neutron generator inside the drill collar body, and arranges a neutron detector assembly, a main control processing circuit, a modulation and demodulation circuit, a power supply circuit and a pressure switch on the drill collar body. This optimized layout of the drill collar effectively utilizes the drill collar space, shortens the overall length of the device, improves the flexible connection adaptability of the logging device at the operation site, and the components of the logging device are independent of each other, which also improves the convenience of maintenance.

[0029] 2. The integrated structural design of the neutron detector assembly of the present invention has strong independence and is easy to repair and maintain.

[0030] 3. The logging device of the present invention is provided with a plurality of neutron detector assemblies arranged in an array. The increase in the number of detectors improves the thermal neutron counting efficiency and the porosity measurement accuracy. The neutron detector assembly is subjected to a diameter-reducing and thickening treatment at the installation position of the drill collar body, thereby enlarging the diameter of the device. During the logging process, the neutron detector is allowed to be as close to the well wall as possible, thereby reducing the influence of the wellbore gap on the neutron porosity measurement.

[0031] 4. The logging device of the present invention adopts a neutron generator to replace the Am-Be chemical source, thereby avoiding the risk of the chemical source falling into the well and eliminating the harm of radiation to operators and the environment.

[0032] 5. The logging device of the present invention adopts a pressure switch device. Only when the logging device is lowered to a certain depth in the formation, the pressure switch is opened under the action of the formation pressure, and the neutron generator can be powered to emit neutrons, thereby improving the safety performance of the device.

[0033] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 A schematic structural diagram of a controllable source neutron porosity logging while drilling device based on an arrayed detector according to an embodiment of the present invention is shown;

[0036] Figure 2 Shown according to Figure 1 A schematic diagram of the lower structure of the drill collar body in the schematic cross-sectional view of the AA section;

[0037] Figure 3 Shown according to Figure 1 A schematic diagram of the middle structure of the drill collar body in the schematic cross-sectional view of the AA section;

[0038] Figure 4 Shown according to Figure 1 A schematic diagram of the upper structure of the drill collar body in the schematic cross-sectional view of the AA section;

[0039] Figure 5 Shown according to Figure 3 A schematic cross-sectional view of the BB section;

[0040] Figure 6 Shown according to Figure 4 A schematic cross-sectional view of the CC section;

[0041] Figure 7 A schematic structural diagram of a neutron detector assembly according to an embodiment of the present invention is shown;

[0042] Figure 8 A schematic diagram of the structure of a high-voltage power supply module according to an embodiment of the present invention is shown;

[0043] Fig. 9 A schematic diagram of the structure of a low-voltage power supply module according to an embodiment of the present invention is shown;

[0044] Fig.10 It shows a schematic diagram of the structure of the identification and shaping circuit cover according to an embodiment of the present invention;

[0045] Fig.11 A schematic diagram of the structure of an amplifier circuit cover according to an embodiment of the present invention is shown;

[0046] Fig.12 A schematic diagram of the electrical connection structure of a controllable source neutron porosity logging while drilling device based on an arrayed detector according to an embodiment of the present invention is shown;

[0047] Fig.13 The neutron porosity calibration curve of the well logging device according to the embodiment of the present invention is shown;

[0048] Fig.14 The neutron porosity calculation process of the well logging device according to the embodiment of the present invention is shown;

[0049] Fig.15 A diagram showing the well logging effect of a well logging device according to an embodiment of the present invention is shown.

[0050] In the figure: 1. Drill collar body; 2. Lower mud guide sleeve; 3. Upper mud guide sleeve; 4. Generator pressure tube; 5. Generator control circuit short section; 6. Generator voltage multiplier short section; 7. Neutron tube; 8. Generator ion source short section; 9. Neutron detector assembly; 10. Main control processing circuit; 11. Modulation and demodulation circuit; 12. Filter circuit; 13. Power supply circuit; 14. Pressure switch; 15. Communication interface; 16. Guide chamber cover; 17. Collection circuit chamber cover; 18. Detector assembly cover; 19. Modulation and demodulation chamber cover; 20. Filter cover ; 21. Power cover; 22. Over-line circuit; 23. Over-line cover; 24. Protective short drill collar; 25. Shell; 26. Long source distance detector compartment; 27. Short source distance detector compartment; 28. Preamplifier circuit compartment; 29. ​​Shaping and identification circuit compartment; 30. Long source distance He-3 tube; 31. Short source distance He-3 tube; 32. Long source distance disc spring; 33. End face plug; 34. Short source distance disc spring; 35. Eight-core connector; 36. High voltage power supply module; 37. Low voltage power supply module; 38. Identification and shaping circuit cover; 39. Amplifier circuit cover. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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.

[0052] It should be noted that the terms "first", "second" etc. in the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described here. In the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" etc. are based on the orientation or positional relationship shown in the accompanying drawings.

[0053] The present invention provides a controllable source neutron porosity logging while drilling device based on an arrayed detector, which adopts technologies such as central placement of a neutron generator in a drill collar water hole, array arrangement of multiple thermal neutron detectors, vibration-resistant design and drill collar diameter variation to shorten the length of the device to improve operational convenience, reduce the influence of wellbore size and device eccentricity, improve thermal neutron counting efficiency, and improve measurement accuracy, so that the device can better meet the application needs at the exploration and development site.

[0054] like Figure 1 , Figure 2 and Figure 4 As shown, a controlled source neutron porosity logging while drilling device based on an array detector includes a drill collar body 1, a neutron generator, a lower mud guide sleeve 2 and an upper mud guide sleeve 3. A water hole structure is arranged in the drill collar body 1, and the neutron generator is arranged in the water hole structure; the lower mud guide sleeve 2 and the upper mud guide sleeve 3 are respectively connected to two ends of the drill collar body 1, and the neutron generator is fixed in the water hole structure through the lower mud guide sleeve 2 and the upper mud guide sleeve 3.

[0055] For example, the drill collar body 1 is made of P550 material, with an overall length of 2.9 m, a water hole structure with a diameter of φ72 mm, and a neutron generator with a diameter of φ48 mm.

[0056] For example, Figure 2-Figure 4 As shown, the neutron generator includes a generator pressure-bearing tube 4, a generator control circuit short section 5, a generator voltage-doubling short section 6, a neutron tube 7 and a generator ion source short section 8 which are sequentially connected from bottom to top. The generator control circuit short section 5 is provided with a high-voltage control circuit, the generator voltage-doubling short section 6 is provided with a voltage-doubling circuit, and the generator ion source short section 8 is provided with an ion source circuit.

[0057] The present invention adopts a neutron generator to replace the Am-Be chemical source, thereby avoiding the risk of the chemical source falling into the well and eliminating the harm of radiation to operators and the environment.

[0058] like Figure 3-Figure 6 As shown, a plurality of neutron detector assemblies 9, a main control processing circuit 10, a modulation and demodulation circuit 11, a filter circuit 12, a power supply circuit 13, a pressure switch 14 and a communication interface 15 are arranged on the drill collar body 1, wherein the plurality of neutron detector assemblies 9 are arranged in a circumferential array along the drill collar body 1, and the plurality of neutron detector assemblies 9 are arranged close to the neutron tube 7 of the neutron generator.

[0059] like Fig.12 As shown, the communication interface 15, the modulation and demodulation circuit 11, the power supply circuit 13, the filter circuit 12 and the main control processing circuit 10 are connected in sequence, the modulation and demodulation circuit 11 is also communicatively connected with the main control processing circuit 10, the main control processing circuit 10 is connected with the neutron generator, and the main control processing circuit 10 is connected with multiple neutron detector components 9.

[0060] For example, the outer side of the drill collar body 1 is provided with a lower guide sleeve compartment, a main control acquisition circuit compartment, a first detector compartment, a second detector compartment, a modem compartment, a pressure switch 14 compartment, a filter compartment, a power supply compartment and a wire passing compartment.

[0061] Among them, the lower guide sleeve compartment is arranged at the lower part of the drill collar body 1, the main control acquisition circuit compartment, the first detector compartment, the second detector compartment and the pressure switch 14 compartment are arranged in the middle part of the drill collar body 1, the modem compartment, the filter compartment, the power supply compartment and the wire passing compartment are arranged at the upper part of the drill collar body 1, and the upper part of the drill collar body 1 is also connected to the protective short drill collar 24.

[0062] For example, the outer diameter of the middle part of the drill collar body 1 is larger than the diameter of the lower and upper parts, the first detector compartment and the second detector compartment are arranged opposite to each other and are arranged close to the neutron tube 7 of the neutron generator; a neutron detector assembly 9 is arranged in the first detector compartment and the second detector compartment, the main control acquisition circuit compartment and the pressure switch 14 compartment are arranged between the first detector compartment and the second detector compartment, and the communication interface 15 is located below the first detector compartment and the second detector compartment.

[0063] The middle part of the drill collar body 1 where the neutron detector assembly 9 is installed is reduced in diameter and thickened to reduce the impact of the wellbore gap; and two neutron detector assemblies 9 are installed, and the two neutron detector assemblies 9 are relatively arranged at 180° to reduce the impact of device eccentricity during drilling.

[0064] For example, the diameter of the drill collar body 1 is φ172 mm, and the middle diameter of the drill collar body 1 is φ197 mm. The middle diameter of the drill collar body 1 is reduced in diameter and thickened mainly to allow the neutron detector assembly 9 to be as close to the well wall as possible to reduce the influence of mud in the wellbore gap.

[0065] The lower mud guide sleeve 2 is arranged in the lower guide sleeve compartment, the main control processing circuit 10 is arranged in the main control acquisition circuit compartment, the modulation and demodulation circuit 11 is arranged in the modulation and demodulation compartment, the filter circuit 12 is arranged in the filter compartment, the power supply circuit 13 is arranged in the power supply compartment, the pressure switch 14 is arranged in the pressure switch 14 compartment, and a line circuit 22 is also arranged in the line compartment.

[0066] For example, the pressure switch 14 includes a pressure cap, a disc spring and a micro switch. Two grooves are arranged on the pressure cap, and an O-ring is arranged in each groove to ensure sealing and pressure bearing. When the device is logging, the pressure cap pushes the disc spring after being subjected to the formation pressure, triggering the micro switch, and the power supply is supplied to the neutron generator in the water hole structure through the upper mud guide sleeve 3.

[0067] The present invention adopts a pressure switch 14. Only when the logging device is lowered to a certain depth in the formation, the pressure switch 14 is opened under the effect of the formation pressure, and the neutron generator can be powered to emit neutrons, thereby improving the safety performance of the device.

[0068] For example, the outer side of the lower guide sleeve compartment is sealed connected to the guide compartment cover 16, the outer side of the main control acquisition circuit compartment is sealed connected to the acquisition circuit compartment cover 17, the outer sides of the first detector compartment and the second detector compartment are respectively sealed connected to the detector assembly cover 18, the outer side of the modem compartment is sealed connected to the modem compartment cover 19, the outer side of the filter compartment is sealed connected to the filter cover 20, the outer side of the power supply compartment is sealed connected to the power supply cover 21, and the outer side of the wire passing compartment is sealed connected to the wire passing cover 23. For example, each compartment can use screws to fasten the cover to the drill collar body 1 to ensure its sealing and pressure resistance, and wire passing holes are opened between adjacent compartments to ensure that power supply and signals are interconnected.

[0069] The present invention fixes the neutron generator on the drill collar body 1 through the lower mud guide sleeve 2 and the upper mud guide sleeve 3, and opens various chambers on the periphery of the drill collar body 1 to install the neutron detector assembly 9, the main control processing circuit 10, the modulation and demodulation circuit 11, the filter circuit 12, the power supply circuit 13, the pressure switch 14, etc., and seals with a cover plate. This drill collar optimized layout effectively utilizes the drill collar space, shortens the overall length of the device, and improves the flexible matching adaptability of the device at the work site. The parts of the device are independent of each other, which also improves the convenience of maintenance and maintenance.

[0070] like Figure 7 As shown, for example, the neutron detector assembly 9 includes a shell 25, which is made of pure iron. Two long source distance detector compartments 26 are arranged at the first end of the shell 25, and one short source distance detector compartment 27 is arranged at the second end of the shell 25. Three preamplifier circuit compartments 28 are arranged in the middle of the shell 25, and a shaping identification circuit compartment 29 is also arranged on one side of the short source distance detector compartment 27 at the second end of the shell 25.

[0071] Among them, each long source distance detector compartment 26 is provided with a long source distance He-3 tube 30, and each long source distance detector compartment 26 is provided with a long source distance disc spring 32 at the end of the long source distance He-3 tube 30, and the end of each long source distance detector compartment 26 is connected to the end face plug 33; a short source distance He-3 tube 31 is arranged in the short source distance detector compartment 27, and the short source distance detector compartment 27 is provided with a short source distance disc spring 34 at the end of the short source distance He-3 tube 31, and the end of the short source distance detector compartment 27 is connected to an eight-core connector 35, and the signal transmission between the external power supply and the two long source distance He-3 tubes 30 and the one short source distance He-3 tube 31 is realized through the eight-core connector 35, and a disc spring structure is installed at the rear of each He-3 tube to improve the vibration resistance of the neutron detector.

[0072] like Figure 8 and Fig. 9 As shown, a high voltage power module 36, a low voltage power module 37 and a shaping identification circuit are arranged in the shaping identification circuit compartment 29, and a preamplifier circuit is arranged in each preamplifier circuit compartment 28.

[0073] For example, the long source distance He-3 tube 30 and the short source distance He-3 tube 31 use RS-P4-0804-201 model He-3 tubes, and a thin film flexible material is wrapped around the outer periphery of the He-3 tubes.

[0074] like Fig.10 As shown, for example, an identification shaping circuit cover plate 38 is provided outside the shaping identification circuit chamber 29, and the identification shaping circuit cover plate 38 is sealed and connected to the shaping identification circuit chamber 29 by bolts, as shown in FIG. Fig.11 As shown, an amplifier circuit cover 39 is disposed on the outside of each preamplifier circuit compartment 28, and the amplifier circuit cover 39 is sealed and connected to the preamplifier circuit compartment 28 by bolts.

[0075] Among them, the identification shaping circuit cover plate 38 and the amplification circuit cover plate 39 are both made of electrical pure iron material and fixed on the housing 25 to shield electromagnetic interference and improve the circuit's ability to resist electromagnetic interference.

[0076] like Fig.12 As shown, the electrical signal connection relationship of the controllable source neutron porosity logging while drilling device based on arrayed detectors of the present invention is as follows: the MWD (Measure While Drilling) system in the acquisition and processing unit is connected in sequence with the modulation and demodulation circuit 11, the power supply circuit 13, the filter circuit 12 and the main control processing circuit 10, and the modulation and demodulation circuit 11 is also connected to the main control processing circuit 10 through RS485 communication. The main control processing circuit 10 is connected to the high-voltage control circuit of the neutron generator through an eight-core connector 35, and the high-voltage control circuit, the voltage multiplier circuit, the neutron tube 7 and the ion source circuit in the neutron generator are connected in sequence.

[0077] The main control processing circuit 10 is connected to the shaping and identification circuit of each neutron detector assembly 9 through an eight-core connector 35. The low-voltage power supply module 37 in each neutron detector assembly 9 is connected to one end of the high-voltage power supply module 36, and two long-source-distance He-3 tubes 30 and one short-source-distance He-3 tube 31 are connected to the other end of the high-voltage power supply module 36. The two long-source-distance He-3 tubes 30 and one short-source-distance He-3 tube 31 are respectively connected to the shaping and identification circuit through a preamplifier circuit.

[0078] The specific working process is as follows: the MWD system introduces the power supply and communication interface 15 into the modulation and demodulation circuit 11 through the upper mud guide sleeve 3, and the power supply and communication signal are separated. The power supply is sent to the two groups of neutron detector components 9 through the eight-core connector 35, and is increased to 1400V by the low-voltage module and the high-voltage module to supply the long-source-distance He-3 tube 30 and the short-source-distance He-3 tube 31 of the neutron detector component 9. The signals generated by the long-source-distance He-3 tube 30 and the short-source-distance He-3 tube 31 are sent to the preamplifier circuit for amplification and shaping, and then sent to the shaping identification circuit for identification, and then the two groups of 6 neutron counting channels are sent to the main control processing circuit 10. At the same time, the main control processing circuit 10 sends the RS485 communication information and power supply to the neutron generator through the upper mud guide sleeve 3 and the eight-core connector 35.

[0079] like Fig.14 As shown, the logging working principle of the controlled source neutron porosity logging while drilling device based on arrayed detectors of the present invention is as follows: after the logging device is powered on and lowered to a certain depth of the formation, the pressure switch 14 is opened under the action of the formation pressure, the neutron generator is fired, and the neutron detector assembly 9 collects a group of long and short source distance count rates. If the long and short source distance count rates reach ten groups, the sample library is updated, and the average value of the long and short source distance count rates is calculated. If the long and short source distance count rates do not reach ten groups, a group of long and short source distance count rates is collected again; after calculating the average value of the long and short source distance count rates, the long and short source distance count rates of the current group are sampled, the abnormal values ​​are eliminated, the long and short source distance count ratio is calculated, the porosity is calculated according to the long and short source distance count ratio, and uploaded to the MWD, as follows:

[0080] After the logging device is powered on and lowered to a certain depth of the formation, the pressure switch 14 is opened under the action of the formation pressure, and the neutron generator is powered. Under the working instruction, the neutron generator generates 14MeV neutrons to bombard the formation. After being slowed down by the formation, the thermal neutrons become thermal neutrons. After being received by the 4 long-source-distance He-3 tubes 30 and the 2 short-source-distance He-3 tubes 31, the thermal neutrons are converted into electrical pulse signals under the action of the high-voltage module, amplified and shaped by the preamplifier circuit, and sent to the main control processing circuit 10. The formation porosity is obtained by using the neutron porosity compensation algorithm.

[0081] The present invention also provides a formation porosity measurement method, which is implemented using the above-mentioned controlled source neutron porosity logging while drilling device based on an array detector, and includes the following steps:

[0082] S1, the main control processing circuit 10 collects 4 long source distance count rates of the long source distance He-3 tube 30 and 2 short source distance count rates of the short source distance He-3 tube 31 as a set of count rate data, which is as follows;

[0083] The main control processing circuit 10 is used to collect 4 long source distance counting rates (Ls1, Ls2, Ls3, Ls4) of the long source distance He-3 tube 30 and 2 short source distance counting rates (Ss1, Ss2) of the short source distance He-3 tube 31. The 6 data are called a set of counting rate data.

[0084] S2. Continuously collect multiple sets of count rate data, and based on the average values ​​of the long source distance count rates and the average values ​​of the short source distance count rates in the multiple sets of count rate data, perform abnormal data screening on the current 4 long source distance count rates and 2 short source distance count rates to obtain the screened long source distance count rates and short source distance count rates, as follows:

[0085] Screen the abnormal data of the current thermal neutron 4-channel long source distance count rate and 2-channel short source distance count rate to prevent vibration, impact and other factors from causing errors in the He-3 tube count. The screening method is to continuously count the first ten groups of count rate data and calculate the average value and Calculate the long and short source distance errors as:

[0086]

[0087]

[0088] Where, Ls i is the long-source-distance count rate of the ith long-source-distance He-3 tube 30, Ss i is the short source distance counting rate of the i-th short source distance He-3 tube 31.

[0089] When Lsi or Ssi Exceed δ (usually 25%), depending on Ls i Outliers should be removed.

[0090] S3. Calculate the average value of the long source distance count rate and the average value of the short source distance count rate after screening, and determine the formation porosity according to the ratio between the average value of the long source distance count rate after screening and the average value of the short source distance count rate after screening, as follows:

[0091] Calculate the average value of the detectors with long and short source distances after removing outliers and And the ratio is obtained as follows

[0092]

[0093] The porosity of the formation can be calculated using formula (2):

[0094]

[0095] In the formula, is the neutron porosity, a0, a1, a n-1 , a n are polynomial fitting factors, a0, a1, a n-1 , a n etc. are polynomial fitting factors, which can be obtained by establishing a calibration curve in the neutron porosity standard well group.

[0096] The modulation and demodulation circuit 11 transmits the porosity information sent by the main control processing circuit 10 through the RS485 communication line to the MWD system after format compression and conversion, thereby realizing the uploading of formation porosity information.

[0097] For example, the well logging device of the present invention completes the calibration work in 8 neutron porosity standard wells in a certain area and establishes a scale response chart, such as Fig.13 As shown, the polynomial fitting factor in formula (2) is determined as follows:

[0098]

[0099] The logging device of the present invention was tested in a standard well in a certain area, and the test results were compared with the standard values ​​and the patent document CN103527181A. Fig.15 As shown, it can be seen that the measurement accuracy of this device is better.

[0100] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A controlled source neutron porosity logging while drilling device based on an array detector, characterized in that: It comprises a drill collar body and a neutron generator, wherein a water hole structure is arranged in the drill collar body, and the neutron generator is arranged in the water hole structure; Among them, a plurality of neutron detector assemblies, a main control processing circuit, a modulation and demodulation circuit, a filter circuit, a power supply circuit, a pressure switch and a communication interface are arranged on the drill collar body; the communication interface, the modulation and demodulation circuit, the power supply circuit, the filter circuit and the main control processing circuit are connected in sequence, the modulation and demodulation circuit is also communicatively connected with the main control processing circuit, the main control processing circuit is connected with the neutron generator and the plurality of neutron detector assemblies, and the plurality of neutron detector assemblies are arranged in a circumferential array along the drill collar body.

2. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 1 is characterized in that: It also includes a lower mud guide sleeve and an upper mud guide sleeve, wherein the lower mud guide sleeve and the upper mud guide sleeve are respectively connected to two ends of the drill collar body, and the neutron generator is fixed in the water hole structure through the lower mud guide sleeve and the upper mud guide sleeve.

3. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 1 is characterized in that: The neutron generator includes a generator pressure-bearing tube, a generator control circuit short section, a generator voltage-doubling short section, a neutron tube and a generator ion source short section which are connected in sequence from bottom to top. A high-voltage control circuit is arranged in the generator control circuit short section, a voltage-doubling circuit is arranged in the generator voltage-doubling short section, and an ion source circuit is arranged in the generator ion source short section.

4. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 3 is characterized in that: A plurality of the neutron detector assemblies are disposed close to the neutron tube.

5. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 1 is characterized in that: The outer side of the drill collar body is provided with a main control acquisition circuit compartment, a first detector compartment, a second detector compartment, a modulation and demodulation compartment, a pressure switch compartment, a filter compartment, a power supply compartment and a wire passing compartment; Among them, the main control acquisition circuit compartment, the first detector compartment, the second detector compartment and the pressure switch compartment are arranged in the middle of the drill collar body, and the modem compartment, the filter compartment, the power supply compartment and the wire passing compartment are arranged in the upper part of the drill collar body.

6. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 1, characterized in that: The upper part of the drill collar body is also connected to a protective short drill collar.

7. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 5 is characterized in that: The outer diameter of the middle part of the drill shank body is larger than the diameters of the lower and upper parts, and the first detector compartment and the second detector compartment are arranged opposite to each other; a neutron detector assembly is arranged in each of the first detector compartment and the second detector compartment, the main control acquisition circuit compartment and the pressure switch compartment are arranged between the first detector compartment and the second detector compartment, and the communication interface is located below the first detector compartment and the second detector compartment.

8. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 7 is characterized in that: The main control processing circuit is arranged in the main control acquisition circuit compartment, the modulation and demodulation circuit is arranged in the modulation and demodulation compartment, the filter circuit is arranged in the filter compartment, the power supply circuit is arranged in the power supply compartment, and the pressure switch is arranged in the pressure switch compartment.

9. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 7, characterized in that: The outer side of the main control acquisition circuit compartment is sealed and connected to the acquisition circuit compartment cover, the outer sides of the first detector compartment and the second detector compartment are respectively sealed and connected to the detector assembly cover plate, the outer side of the modem compartment is sealed and connected to the modem compartment cover, the outer side of the filter compartment is sealed and connected to the filter cover plate, the outer side of the power supply compartment is sealed and connected to the power supply cover plate, and the outer side of the wire passing compartment is sealed and connected to the wire passing cover plate.

10. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to any one of claims 1 to 9, characterized in that: The neutron detector assembly comprises a shell, wherein two long-source-distance detector compartments are arranged at the first end of the shell, one short-source-distance detector compartment is arranged at the second end of the shell, three preamplifier circuit compartments are arranged in the middle of the shell, and a shaping identification circuit compartment is also arranged at one side of the short-source-distance detector compartment at the second end of the shell; Each of the long source distance detector compartments is provided with a long source distance He-3 tube, the short source distance detector compartment is provided with a short source distance He-3 tube, the shaping and identification circuit compartment is provided with a high voltage power supply module, a low voltage power supply module and a shaping and identification circuit, and each of the preamplifier circuit compartments is provided with a preamplifier circuit.

11. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 10, characterized in that: Each of the long source distance detector compartments is provided with a long source distance disc spring at the end of the long source distance He-3 tube, and the end of each of the long source distance detector compartments is connected to the end face plug; the short source distance detector compartment is provided with a short source distance disc spring at the end of the short source distance He-3 tube, and the end of the short source distance detector compartment is connected to the eight-core connector.

12. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 10, characterized in that: The outer side of the shaping and identification circuit bin is sealed and connected to the identification and shaping circuit cover plate, and the outer side of each preamplifier circuit bin is sealed and connected to an amplifier circuit cover plate.

13. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 10, characterized in that: The shell, the identification and shaping circuit cover plate and the amplifier circuit cover plate are all made of electrical pure iron.

14. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 10, characterized in that: In each neutron detector assembly, a low voltage power supply module is connected to one end of a high voltage power supply module, two long source distance He-3 tubes and one short source distance He-3 tube are connected to the other end of the high voltage power supply module, the two long source distance He-3 tubes and one short source distance He-3 tube are respectively connected to a shaping and identification circuit through a preamplifier circuit, and a main control processing circuit is connected to the shaping and identification circuit of each neutron detector assembly.

15. The controlled source neutron porosity logging while drilling device based on arrayed detectors according to claim 3, characterized in that: The high-voltage control circuit, the voltage multiplier circuit, the neutron tube and the ion source circuit are connected in sequence, and the main control processing circuit is connected to the high-voltage control circuit.

16. A formation porosity measurement method, characterized in that: The method is implemented by using the controlled source neutron porosity logging while drilling device based on an arrayed detector as described in any one of claims 10 to 14, comprising the following steps: The main control processing circuit collects 4 long-source-distance counting rates of the long-source-distance He-3 tube and 2 short-source-distance counting rates of the short-source-distance He-3 tube as a set of counting rate data; Continuously collect multiple groups of count rate data, and based on the average values ​​of the long source distance count rates and the average values ​​of the short source distance count rates in the multiple groups of count rate data, perform abnormal data screening on the current 4 long source distance count rates and 2 short source distance count rates to obtain the screened long source distance count rates and short source distance count rates; The average values ​​of the long source distance counting rate and the short source distance counting rate after screening are calculated respectively, and the formation porosity is determined according to the ratio between the average value of the long source distance counting rate after screening and the average value of the short source distance counting rate after screening.

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