Arrayed detector based controlled source neutron porosity while drilling apparatus

Abstract

The present application belongs to the field of oil and gas drilling technology, and discloses a controllable source neutron porosity logging-while-drilling device based on an array detector, which comprises a drill collar body and a neutron generator. A water eye structure is arranged in the drill collar body, and the neutron generator is arranged in the water eye structure. 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 sequentially connected. The modulation and demodulation circuit is also in communication connection with the main control processing circuit. The main control processing circuit is connected with the neutron generator and the plurality of neutron detector assemblies. The plurality of neutron detector assemblies are arranged in a circumferential array along the drill collar body. The present application effectively utilizes the drill collar space, shortens the overall length of the device, improves the flexible matching adaptability of the device in the operation site, and improves the maintenance convenience of the independent device parts.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas drilling, and particularly relates to a controllable source neutron porosity logging-while-drilling device based on an arrayed detector. BACKGROUND

[0002] Compared with wireline logging, logging-while-drilling can obtain more original formation information in the process of actually drilling a high-deviation and long-horizontal well, make a decision on drilling direction, enhance oil and gas identification capability, and improve oil drainage area, thereby improving the economic benefits of oil and gas exploration and development, and has become a main engineering technology for increasing reserves and production of unconventional oil and gas. Logging-while-drilling controllable source neutron porosity logging can obtain formation porosity data in real time, and is an important component of formation evaluation logging while drilling. In addition, the device uses a neutron generator to replace a traditional Am-Be neutron source, avoids the risk of chemical source falling into a well, and is safe and controllable for neutron rays, friendly to construction personnel and the surrounding environment, is a future development direction of "green" and environmentally-friendly logging, and has become an important logging method for realizing "source-free" and safely obtaining formation porosity data in high-deviation wells, long-horizontal wells and complex working condition wells.

[0003] Patent document CN103527181A discloses a logging-while-drilling controllable source neutron logging method and instrument, uses two He-3 tubes as long and short source distance He-3 tubes 31, respectively, and sequentially assembles a detector, a neutron generator and an acquisition unit into an electronic instrument structure in a side wall slotting manner, and installs the electronic instrument structure in a drill collar in a radial eccentric manner, so as to realize logging-while-drilling neutron porosity measurement. The implementation manner has the following disadvantages: the eccentric installation manner makes the measurement precision of the device easily affected by the up-and-down borehole clearance in a logging-while-drilling environment; only one group of He-3 tubes is used as a neutron probe, the counting efficiency is low, and there is no anti-vibration protection measure, so the He-3 tubes are easily affected by vibration as gas detectors; and the radial installation of all parts leads to a long drill collar size, inconvenient field connection operation, in addition, once the instrument fails, the electronic instrument needs to be completely disassembled, and maintenance is complicated. SUMMARY

[0004] In view of the above problems, the present application provides a logging-while-drilling controllable source neutron porosity logging device based on an arrayed detector, which adopts the following technical scheme:

[0005] The logging-while-drilling controllable source neutron porosity logging device based on an arrayed detector comprises a drill collar body and a neutron generator, the drill collar body is provided with a water eye structure, and the neutron generator is arranged in the water eye structure.

[0006] The drill collar body is provided with 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; the communication interface, the modulation and demodulation circuit, the power supply circuit, the filter circuit and the main control processing circuit are sequentially connected, the modulation and 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 plurality of neutron detector assemblies, and the plurality of neutron detector assemblies are arranged in a circumferential array along the drill collar body.

[0007] Further, the lower mud flow guide sleeve and the upper mud flow guide sleeve are respectively connected with both ends of the drill collar body, and the neutron generator is fixed in the water eye structure through the lower mud flow guide sleeve and the upper mud flow guide sleeve.

[0008] Further, the neutron generator comprises, from bottom to top, a generator pressure-bearing cylinder, a generator control circuit short section, a generator voltage-doubling short section, a neutron tube and a generator ion source short section, the generator control circuit short section is provided with a high-voltage control circuit, the generator voltage-doubling short section is provided with a voltage-doubling circuit, and the generator ion source short section is provided with an ion source circuit.

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

[0010] Further, the outer side of the drill collar body is provided with a main control acquisition circuit bin, a first detector bin, a second detector bin, a modulation and demodulation bin, a pressure switch bin, a filter bin, a power supply bin and a wire passing bin.

[0011] The main control acquisition circuit bin, the first detector bin, the second detector bin and the pressure switch bin are arranged in the middle part of the drill collar body, and the modulation and demodulation bin, the filter bin, the power supply bin and the wire passing bin are arranged in the upper part of the drill collar body.

[0012] Further, the upper part of the drill collar body is further connected with a protective short drill collar.

[0013] Further, the outer diameter of the middle part of the drill collar body is greater than the diameters of the lower part and the upper part, and the first detector bin and the second detector bin are arranged oppositely; one neutron detector assembly is arranged in each of the first detector bin and the second detector bin, the main control acquisition circuit bin and the pressure switch bin are arranged between the first detector bin and the second detector bin, and the communication interface is located below the first detector bin and the second detector bin.

[0014] Further, 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.

[0015] Further, the outer side of the main control acquisition circuit compartment is sealingly connected with the acquisition circuit compartment cover, the outer sides of the first detector compartment and the second detector compartment are respectively sealingly connected with the detector assembly cover plate, the outer side of the modulation and demodulation compartment is sealingly connected with the modulation and demodulation compartment cover, the outer side of the filter compartment is sealingly connected with the filter cover plate, the outer side of the power supply compartment is sealingly connected with the power supply cover plate, and the outer side of the wire passing compartment is sealingly connected with the wire passing cover plate.

[0016] Further, the neutron detector assembly comprises a shell, the shell is provided with two long source distance detector compartments at the first end, the shell is provided with one short source distance detector compartment at the second end, the shell is provided with three preamplifier circuit compartments in the middle, and the shell is further provided with a shaping and discriminating circuit compartment on one side of the short source distance detector compartment at the second end.

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

[0018] Further, 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 with an 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 with an eight-core connector.

[0019] Further, the outer side of the shaping and discriminating circuit compartment is sealingly connected with a discriminating and shaping circuit cover plate, and the outer side of each of the preamplifier circuit compartments is sealingly connected with one amplification circuit cover plate.

[0020] Further, the shell, the discriminating and shaping circuit cover plate and the amplification circuit cover plate are all made of pure electrical iron material.

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

[0022] Further, the high-voltage control circuit, the voltage doubling circuit, the neutron tube and the ion source circuit are connected in sequence, and the main control processing circuit is connected with the high-voltage control circuit.

[0023] The application further provides a formation porosity measurement method, which is realized by using the arrayed detector-based controllable source neutron porosity logging-while-drilling device and includes the following steps:

[0024] The main control processing circuit collects four long-source-distance He-3 tube count rates and two short-source-distance He-3 tube count rates as a group of count rate data;

[0025] A plurality of groups of count rate data are continuously collected, the current four long-source-distance count rates and two short-source-distance count rates are subjected to abnormal data screening based on the average value of the long-source-distance count rates and the average value of the short-source-distance count rates in the plurality of groups of count rate data, and screened long-source-distance count rates and short-source-distance count rates are obtained;

[0026] The average value of the screened long-source-distance count rates and the average value of the screened short-source-distance count rates are respectively calculated, and the formation porosity is determined according to the ratio between the average value of the screened long-source-distance count rates and the average value of the screened short-source-distance count rates.

[0027] The application has the following beneficial effects:

[0028] 1、The neutron generator is fixed in the drill collar body, and the neutron detector assembly, the main control processing circuit, the modulation and demodulation circuit, the power supply circuit and the pressure switch are arranged on the drill collar body, so that the drill collar is optimized and arranged, the space of the drill collar is effectively utilized, the overall length of the device is shortened, the flexible matching adaptability of the logging device in the operation site is improved, the parts of the logging device are independent of each other, and the maintenance convenience is improved.

[0029] 2、The integrated structure of the neutron detector assembly has high independence and is easy to maintain.

[0030] 3、The logging device 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 mounting position of the neutron detector assembly on the drill collar body is subjected to variable-diameter thickening treatment, the diameter of the device is expanded, the neutron detector is allowed to adhere to the well wall as much as possible in the logging process, and the influence of the wellbore gap on the neutron porosity measurement is reduced.

[0031] 4、The logging device uses a neutron generator to replace an Am-Be chemical source, avoids the risk of chemical source falling into the well, and eliminates the harm of radiation to the operator and the environment.

[0032] 5、The logging device of the present application adopts pressure switch device, only when the logging device is lowered to a certain depth of stratum, under the action of stratum pressure, the pressure switch opens, the neutron generator can supply power to emit neutron, which improves the safety performance of the device.

[0033] Additional features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the present application. The objectives and other advantages of the present application will be realized and attained by the structure particularly pointed out in the description and appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

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

[0036] Figure 2 A lower structure schematic diagram of a drill collar body in a sectional view schematic diagram of an A-A section according to the present application is shown; Figure 1

[0037] A middle structure schematic diagram of a drill collar body in a sectional view schematic diagram of an A-A section according to the present application is shown; Figure 3 Figure 1 An upper structure schematic diagram of a drill collar body in a sectional view schematic diagram of an A-A section according to the present application is shown;

[0038] Figure 4 Figure 1 A sectional view schematic diagram of a B-B section according to the present application is shown;

[0039] Figure 5 A sectional view schematic diagram of a C-C section according to the present application is shown; Figure 3

[0040] Figure 6 A sectional view schematic diagram of a C-C section according to the present application is shown; Figure 4

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

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

[0043] A structure schematic diagram of a high-voltage power supply module according to an embodiment of the present application is shown;​​​Figure 9 Fig. 1 shows a schematic diagram of a low-voltage power module structure according to an embodiment of the present application;

[0044] Figure 10 Fig. 2 shows a schematic diagram of a discrimination shaping circuit cover structure according to an embodiment of the present application;

[0045] Figure 11 Fig. 3 shows a schematic diagram of an amplification circuit cover structure according to an embodiment of the present application;

[0046] Figure 12 Fig. 4 shows a schematic diagram of an 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 application;

[0047] Figure 13 Fig. 5 shows a neutron porosity calibration curve of a logging device according to an embodiment of the present application;

[0048] Figure 14 Fig. 6 shows a neutron porosity calculation flow of a logging device according to an embodiment of the present application;

[0049] Figure 15 Fig. 7 shows a logging effect diagram of a logging device according to an embodiment of the present application.

[0050] In the figure: 1, drill collar body; 2, lower mud flow guide sleeve; 3, upper mud flow guide sleeve; 4, generator pressure-bearing cylinder; 5, generator control circuit short section; 6, generator voltage doubler 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, flow guide bin cover; 17, acquisition circuit bin cover; 18, detector assembly cover plate; 19, modulation and demodulation bin cover; 20, filter cover plate; 21, power supply cover plate; 22, wire passing circuit; 23, wire passing cover plate; 24, protective short drill collar; 25, shell; 26, long source distance detector bin; 27, short source distance detector bin; 28, preamplification circuit bin; 29, shaping and discrimination circuit bin; 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 module; 37, low-voltage power module; 38, discrimination shaping circuit cover plate; 39, amplification circuit cover plate. DETAILED DESCRIPTION

[0051] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0052] It should be noted that the terms "first", "second", and the like in the present application are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein. In the present application, the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", and the like are based on the orientations or positional relationships shown in the drawings.

[0053] The present application provides a controllable source neutron porosity logging-while-drilling device based on an arrayed detector, which adopts a neutron generator centrally arranged in a water eye of a drill collar, a plurality of thermal neutron detector arrays arranged, an anti-vibration design, and a drill collar variable diameter technology, shortens the device length, improves the operation convenience, reduces the influence of the borehole size and the device eccentricity, improves the thermal neutron counting efficiency, improves the measurement accuracy, and better meets the application requirements in the exploration and development field.

[0054] As shown in Figure 1 , Figure 2 and Figure 4 , a controllable source neutron porosity logging-while-drilling device based on an arrayed detector includes a drill collar body 1, a neutron generator, a lower mud flow guide sleeve 2, and an upper mud flow guide sleeve 3. The drill collar body 1 is provided with a water eye structure, and the neutron generator is arranged in the water eye structure. The lower mud flow guide sleeve 2 and the upper mud flow guide sleeve 3 are respectively connected with both ends of the drill collar body 1, and the neutron generator is fixed in the water eye structure through the lower mud flow guide sleeve 2 and the upper mud flow guide sleeve 3.

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

[0056] For example, as shown in Figures 2-4 , the neutron generator includes a generator pressure-bearing cylinder 4, a generator control circuit short section 5, a generator voltage doubler short section 6, a neutron tube 7, and a generator ion source short section 8 connected in sequence from bottom to top. The generator control circuit short section 5 is provided with a high-voltage control circuit, the generator voltage doubler short section 6 is provided with a voltage doubler circuit, and the generator ion source short section 8 is provided with an ion source circuit.

[0057] The application uses a neutron generator to replace an Am-Be chemical source, avoids the risk of falling well of the chemical source, and eliminates the harm of the rays to the operators and the environment.

[0058] As shown in Figures 3-6 The drill collar body 1 is provided with 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, 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] As shown in Figure 12 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 in communication connection 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 the plurality of neutron detector assemblies 9.

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

[0061] The lower flow 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 at the middle part of the drill collar body 1, the modulation and demodulation 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 with the protection short drill collar 24.

[0062] For example, the middle part of the drill collar body 1 has a larger outer diameter than the lower part and the upper part, the first detector compartment and the second detector compartment are oppositely arranged and close to the neutron tube 7 of the neutron generator; one neutron detector assembly 9 is arranged in each of 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 assemblies 9 are installed, is subjected to diameter increasing treatment, so as to reduce the influence of the wellbore clearance; and two neutron detector assemblies 9 are installed, which are oppositely arranged and distributed at 180°, so as to reduce the influence of the device eccentricity in the drilling process.

[0064] For example, the diameter of the drill collar body 1 is φ172mm, the diameter of the middle part of the drill collar body 1 is φ197mm, and the diameter increasing treatment of the middle part of the drill collar body 1 is mainly used to make the neutron detector assemblies 9 as close as possible to the well wall, so as to reduce the influence of the wellbore clearance mud.

[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 wire-passing circuit 22 is also arranged in the wire-passing compartment.

[0066] For example, the pressure switch 14 consists of a pressure cap, a disc spring, and a microswitch. The cap has two grooves, each containing an O-ring to ensure a tight seal. During well logging, the cap, under pressure from the formation, pushes against the disc spring, triggering the microswitch. This power is then supplied to the neutron generator within the borehole structure via 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 action 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 with the guide compartment cover 16, the outer side of the main control acquisition circuit compartment is sealed with the acquisition circuit compartment cover 17, the outer sides of the first detector compartment and the second detector compartment are respectively sealed with the detector assembly cover 18, the outer side of the modem compartment is sealed with the modem compartment cover 19, the outer side of the filter compartment is sealed with the filter cover 20, the outer side of the power supply compartment is sealed with the power supply cover 21, and the outer side of the wire passing compartment is sealed with the wire passing cover 23. For example, each compartment can use screws to fasten the cover to the drill collar body 1 to ensure that it is sealed and pressure-bearing, and wire passing holes are opened between adjacent compartments to ensure that power supply and signals are interconnected.

[0069] The present invention secures the neutron generator to the drill collar body 1 via a lower mud guide sleeve 2 and an upper mud guide sleeve 3. Various compartments are provided around the outer periphery of the drill collar body 1 to accommodate the neutron detector assembly 9, main control processing circuit 10, modulation and demodulation circuit 11, filter circuit 12, power supply circuit 13, pressure switch 14, and other components. These compartments are sealed with a cover plate. This optimized drill collar layout effectively utilizes the drill collar space, shortens the overall length of the device, and improves its adaptability and flexibility at the worksite. The independence of the device components also enhances ease of maintenance and servicing.

[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 provided at the first end of the shell 25, and one short-source-distance detector compartment 27 is provided at the second end of the shell 25. Three preamplifier circuit compartments 28 are provided in the middle of the shell 25, and a shaping identification circuit compartment 29 is also provided on the side of the short-source-distance detector compartment 27 at the second end of the shell 25.

[0071] Wherein, 1 long source distance He-3 tube 30 is arranged in each long source distance detector bin 26, a long source distance disc spring 32 is arranged at the end of the long source distance He-3 tube 30 of each long source distance detector bin 26, and the end of each long source distance detector bin 26 is connected with an end face plug 33; 1 short source distance He-3 tube 31 is arranged in the short source distance detector bin 27, a short source distance disc spring 34 is arranged at the end of the short source distance He-3 tube 31 of the short source distance detector bin 27, and the end of the short source distance detector bin 27 is connected with an eight-core connector 35, and external power supply and signal transmission of the two long source distance He-3 tubes 30 and the short source distance He-3 tube 31 are realized through the eight-core connector 35, and a disc spring structure is arranged behind each He-3 tube to improve the anti-vibration capability of the neutron detector.

[0072] As shown in Figure 8 and Figure 9 A high-voltage power module 36, a low-voltage power module 37 and a shaping and discriminating circuit are arranged in the shaping and discriminating circuit bin 29, and 1 preamplifier circuit is arranged in each preamplifier circuit bin 28.

[0073] For example, the long source distance He-3 tube 30 and the short source distance He-3 tube 31 adopt an RS-P4-0804-201 type He-3 tube, and a thin film flexible material is wound around the periphery of the He-3 tube.

[0074] As shown in Figure 10 For example, a discriminating and shaping circuit cover plate 38 is arranged on the outside of the shaping and discriminating circuit bin 29, the discriminating and shaping circuit cover plate 38 is sealingly connected with the shaping and discriminating circuit bin 29 through bolts, and as shown in Figure 11 A preamplifier circuit cover plate 39 is arranged on the outside of each preamplifier circuit bin 28, and the preamplifier circuit cover plate 39 is sealingly connected with the preamplifier circuit bin 28 through bolts.

[0075] The discriminating and shaping circuit cover plate 38 and the preamplifier circuit cover plate 39 are both made of pure electrical iron and fixed on the shell 25, so as to shield electromagnetic interference and improve the electromagnetic interference resistance of the circuit.

[0076] As shown in Figure 12 As shown in the figure, the electrical signal connection relationship of the controllable source neutron porosity logging while drilling device based on the arrayed detector of the application is that the MWD (Measure While Drilling) system, the modulation and demodulation circuit 11, the power circuit 13, the filter circuit 12 and the main control processing circuit 10 are sequentially connected in the acquisition and processing unit, the modulation and demodulation circuit 11 is also connected with the main control processing circuit 10 through Rs485 communication connection. The main control processing circuit 10 is connected with the high-voltage control circuit of the neutron generator through the eight-core connector 35, and the high-voltage control circuit, the voltage doubling circuit, the neutron tube 7 and the ion source circuit of the neutron generator are sequentially connected.

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

[0078] Specific working process is as follows: the MWD system introduces the power supply and communication interface 15 into the modem circuit 11 through the mud flow sleeve 3, and the power supply and communication signal are separated from each other. The power supply is sent into the two groups of neutron detector assemblies 9 through the eight-core connector 35, is lifted to 1400V through the low-voltage module and the high-voltage module, and is supplied to the long-source-distance He-3 tube 30 and the short-source-distance He-3 tube 31 of the neutron detector assembly 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, are amplified and shaped, are then sent to the shaping discrimination circuit, and the two groups of six-channel 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 the power supply to the neutron generator through the mud flow sleeve 3 and the eight-core connector 35.

[0079] As shown in Figure 14 The logging working principle of the controllable source neutron porosity logging-while-drilling device based on the arrayed detector of the present application is as follows: after the logging device is powered on and is 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, a group of long-short source distance count rates are collected by the neutron detector assembly 9, if the long-short source distance count rates reach ten groups, the sample library is updated, the average value of the long-short source distance count rates is calculated, if the long-short source distance count rates do not reach ten groups, a group of long-short source distance count rates are collected again; after the average value of the long-short source distance count rates is calculated, the current group of long-short source distance count rates are collected, the abnormal values are removed, the long-short source distance count ratio is calculated, the porosity is calculated according to the long-short source distance count ratio, and is uploaded to the MWD, and the specific process is as follows:

[0080] After the logging device is powered on and is 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 powered, and under the working instruction, the neutron generator generates 14MeV neutrons to bombard the formation. After being moderated by the formation, the thermal neutrons are received by the four long-source-distance He-3 tubes 30 and the two short-source-distance He-3 tubes 31, are converted into electric pulse signals under the action of the high-voltage module, are amplified and shaped by the preamplifier circuit, are sent to the main control processing circuit 10, and 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, specifically as follows;

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

[0084] S2. Continuously collect multiple sets of count rate data. 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 four long source distance count rates and two 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 the error caused by vibration, impact and other factors on 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 counting rate of the i-th 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 Er Ssi If it exceeds δ (usually 25%), 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 and the average value of the short source distance count rate after screening, as follows:

[0091] Calculate the average value of long and short source distance detectors after removing outliers and And the ratio is derived, as follows

[0092]

[0093] The formation porosity size can be calculated by formula (2):

[0094]

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

[0096] The modulating and demodulating 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 transformation, so as to realize the uploading of the formation porosity information.

[0097] For example, the logging device of the present application completes the calibration work in 8 neutron porosity standard wells in a certain area, establishes a calibration response chart, as shown in Figure 13 , and determines the polynomial fitting factor in formula (2),

[0098]

[0099] The logging device of the present application tests the standard well in a certain area, and the test results are compared with the standard value and the patent document CN103527181A, as shown in Figure 15 It can be seen that the measurement accuracy of the device is better.

[0100] Although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements 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 application.

Claims

1. An arrayed-detector based controlled source neutron porosity logging-while-drilling apparatus, characterized by, The drill collar body is provided with a water eye structure, and the neutron generator is arranged in the water eye structure. The drill collar body is provided with 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. The communication interface, the modulation and demodulation circuit, the power supply circuit, the filter circuit and the main control processing circuit are sequentially connected. The modulation and demodulation circuit is also in communication connection with the main control processing circuit. The main control processing circuit is connected with the neutron generator and the plurality of neutron detector assemblies.

2. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 1, wherein, The plurality of neutron detector assemblies are arranged in a circumferential array along the drill collar body.

3. The arrayed-detector based, controlled source neutron porosity LWD-while- drilling apparatus of claim 2, wherein, The drill collar body is provided with a main control acquisition circuit bin, a first detector bin, a second detector bin, a modulation and demodulation bin, a pressure switch bin, a filter bin, a power supply bin and a wire passing bin.

4. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 1, wherein, The main control acquisition circuit bin, the first detector bin, the second detector bin and the pressure switch bin are arranged in the middle part of the drill collar body. The modulation and demodulation bin, the filter bin, the power supply bin and the wire passing bin are arranged in the upper part of the drill collar body.

5. The arrayed-detector based, controlled source neutron porosity LWD-while- drilling apparatus of claim 1, wherein, The upper part of the drill collar body is also connected with a protective short drill collar.

6. The arrayed-detector based, controlled source neutron porosity LWD-while- drilling apparatus of claim 4, wherein, The outer diameter of the middle part of the drill collar body is greater than the diameters of the lower part and the upper part. The first detector bin and the second detector bin are oppositely arranged. Each of the first detector bin and the second detector bin is provided with one neutron detector assembly. The main control acquisition circuit bin and the pressure switch bin are arranged between the first detector bin and the second detector bin. The communication interface is located below the first detector bin and the second detector bin.

7. The arrayed-detector based, controlled source neutron porosity LWD-while- drilling apparatus of claim 6, wherein, The master control processing circuit is arranged in the master 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.

8. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 6, wherein, The outer side of the master control acquisition circuit compartment is sealingly connected with the acquisition circuit compartment cover, the outer sides of the first detector compartment and the second detector compartment are respectively sealingly connected with the detector assembly cover plate, the outer side of the modulation and demodulation compartment is sealingly connected with the modulation and demodulation compartment cover, the outer side of the filter compartment is sealingly connected with the filter cover plate, the outer side of the power supply compartment is sealingly connected with the power supply cover plate, and the outer side of the wire passing compartment is sealingly connected with the wire passing cover plate.

9. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 1, wherein, Each long source distance detector compartment 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 long source distance detector compartment is connected with an 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 with an eight-core connector.

10. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 1, wherein, The outer side of the shaping and discriminating circuit compartment is sealingly connected with the discriminating shaping circuit cover plate, and the outer side of each preamplifier circuit compartment is sealingly connected with one amplification circuit cover plate.

11. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 10, wherein, The shell, the discriminating shaping circuit cover plate and the amplification circuit cover plate are all made of pure electrical iron material.

12. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 1, wherein, One end of the low-voltage power supply module and the high-voltage power supply module in each neutron detector assembly is connected, the other end of the high-voltage power supply module is connected with two long source distance He-3 tubes and one short source distance He-3 tube, the two long source distance He-3 tubes and the short source distance He-3 tube are respectively connected with one preamplifier circuit and the shaping and discriminating circuit, and the master control processing circuit is connected with the shaping and discriminating circuit of each neutron detector assembly.

13. The arrayed-detector based, controlled source neutron porosity logging-while- drilling apparatus of claim 2, wherein, The high-voltage control circuit, the voltage doubling circuit, the neutron tube and the ion source circuit are sequentially connected, and the master control processing circuit is connected with the high-voltage control circuit.

14. A method of formation porosity measurement, characterized by, The controllable source neutron porosity logging while drilling device based on the arrayed detector is realized by using the device according to any one of claims 1-13, and the device comprises the following steps: The master control processing circuit acquires four long source distance count rates of the long source distance He-3 tube and two short source distance count rates of the short source distance He-3 tube as a group of count rate data; A plurality of groups of count rate data are continuously acquired, the average value of the long source distance count rate and the average value of the short source distance count rate in the plurality of groups of count rate data are used to perform abnormal data screening on the current four long source distance count rates and two short source distance count rates, and screened long source distance count rates and short source distance count rates are obtained; The average value of the screened long source distance count rates and the average value of the screened short source distance count rates are respectively calculated, and the formation porosity is determined according to the ratio between the average value of the screened long source distance count rates and the average value of the screened short source distance count rates.

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