A circuit system for conditioning small signals of logging while drilling

Abstract

The present invention relates to the field of logging while drilling, and discloses a logging while drilling micro-signal conditioning circuit system, comprising: a strain bridge module, comprising a strain bridge composed of a resistance strain gauge pasted on a drill string, the strain bridge being able to convert the change in the resistance value of the resistance strain gauge into a voltage signal; an amplification module, comprising a two-stage amplification circuit, for amplifying the voltage signal output by the strain bridge module; a filtering module, for filtering out the noise signal in the output signal of the amplification module; an A / D conversion module, for converting the filtered voltage analog signal into a digital signal; a microcontroller unit MCU, for performing data processing on the digital signal processed by the A / D conversion module to obtain the measured engineering parameters. The present invention can measure the real drilling pressure and torque in the well, and provide a real-time basis for drilling engineers to accurately and quickly adjust drilling parameters, change drilling methods, and drill safely.

Description

Technical Field

[0001] The invention relates to the field of logging while drilling, and in particular to a logging while drilling tiny signal conditioning circuit system. Background Art

[0002] Logging while drilling generally refers to measuring the physical parameters of the formation rock during the drilling process, and using the data telemetry system to send the measurement results to the ground for processing in real time. Logging while drilling technology is a key technology for geo-steering drilling guidance, and is very important for completing large-angle wells, on-site decision-making, interpretation, real-time well site data collection, and horizontal well drilling design.

[0003] Logging while drilling is a logging method that installs logging instruments near the drill bit to measure various formation information just after the bottom layer is drilled. It performs directional drilling control by measuring the formation inclination and azimuth, drill bit direction, drilling pressure, torque, etc., and measures the formation's resistivity, natural potential, natural gamma, density / neutron, nuclear magnetic resonance, acoustic wave time difference, etc. Its measurement results overcome the influence of a series of environmental conditions such as wellbore expansion and mud invasion. Logging while drilling can provide formation and wellbore information in real time, make rapid evaluation of the formation, optimize the wellbore trajectory and geological targets, and guide drilling. It is especially more important than cable logging in difficult wells, high-angle wells, and horizontal wells.

[0004] During the drilling process, accurate measurement of drilling parameters such as drilling pressure and torque near the drill bit is very important for safe and efficient drilling. By analyzing and processing the real-time measurement values ​​of the near-bit engineering parameters, we can summarize the influence of each measurement parameter on the drilling process and efficiency, timely discover and control certain drilling accidents, achieve the purpose of safe and efficient drilling, and truly realize risk-free drilling. However, in the measurement of drilling pressure and torque near the drill bit in the well, due to the complex downhole environment, the detected signal is weak and accompanied by strong noise signals, which will cause signal processing difficulties.

[0005] The invention provides a logging while drilling micro-signal conditioning circuit system, which can accurately measure the drilling pressure and torque of a drill string and provide a real-time basis for safe drilling. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a logging while drilling micro-signal conditioning circuit system, which can detect the drilling pressure and torque in the well in real time by measuring the resistance change of the strain gauge.

[0007] The specific technical solutions of the present invention are as follows:

[0008] A small signal conditioning circuit system for logging while drilling, comprising:

[0009] The strain bridge module comprises a strain bridge composed of a resistance strain gauge attached to a drill string, wherein the strain bridge can convert the change of the resistance value of the resistance strain gauge into a voltage signal;

[0010] an amplification module, comprising a two-stage amplification circuit, for amplifying the voltage signal output by the strain bridge module;

[0011] A filtering module, used to filter out noise signals in the output signal of the amplifying module;

[0012] A / D conversion module, converting the filtered voltage analog signal into a digital signal;

[0013] The microcontroller unit MCU is used to process the digital signal processed by the A / D conversion module and obtain the measured engineering parameters.

[0014] Furthermore, the strain bridge includes a bit pressure measurement strain bridge and a torque measurement strain bridge.

[0015] Preferably, the drilling pressure measurement strain bridge and the torque measurement strain bridge respectively form independent data acquisition channels with the amplification module, the filtering module, the A / D conversion module and the microcontroller unit MCU.

[0016] Furthermore, the resistance strain gauge of the bit pressure measurement strain bridge is pasted in a direction of 90 degrees to the axis, and the resistance strain gauge of the torque measurement strain bridge is pasted in a direction of 45 degrees to the axis.

[0017] Preferably, the strain bridge is an equal-arm bridge.

[0018] Furthermore, the two-stage amplifier circuit includes a first-stage amplifier circuit and a second-stage amplifier circuit, the gain of the first-stage amplifier circuit is 100, and the gain of the second-stage amplifier circuit is 10.

[0019] Preferably, the filtering module comprises a second-order active bandpass filtering circuit for filtering out high-frequency signals and low-frequency signals in the signal.

[0020] Furthermore, the circuit system also includes a high-temperature power supply module circuit for supplying power to various modules of the system, and the supply voltage of the high-temperature power supply module circuit is ±5V.

[0021] Furthermore, the circuit system also includes a storage module for storing various engineering parameters obtained during the measurement process.

[0022] Preferably, the circuit system further comprises a polarity adjustment circuit and a balancing addition circuit for eliminating the unbalance of the AC strain bridge.

[0023] Implementing the embodiments of the present invention has the following beneficial effects:

[0024] The present invention can measure the real drilling pressure and torque in the well, and provide a real-time basis for drilling engineers to accurately and quickly adjust drilling parameters, change drilling methods, and drill safely. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a circuit diagram of a strain gauge bridge provided by an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of a logging while drilling tiny signal conditioning circuit system provided by an embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the sticking position of the strain gauge under pressure provided by an embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the sticking position of the strain gauge when subjected to torsion provided by an embodiment of the present invention;

[0029] Figure 5 This is a circuit diagram of a high temperature power supply module provided by an embodiment of the present invention;

[0030] Figure 6 is a circuit diagram of a signal amplification circuit provided by an embodiment of the present invention;

[0031] Figure 7 is a circuit diagram of a polarity adjustment circuit provided by an embodiment of the present invention;

[0032] Figure 8 is a circuit diagram of a balancing and adding circuit provided by an embodiment of the present invention;

[0033] Fig. 9 is a circuit diagram of a filter circuit provided by an embodiment of the present invention;

[0034] Fig.10 It is an AC simulation waveform diagram of a bandpass filter provided by an embodiment of the present invention;

[0035] Fig.11 It is a transient simulation waveform diagram of a bandpass filter provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only embodiments of a part of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0038] The strain bridge can convert the slight change of the resistance of the strain gauge into the change of the output voltage. Its advantage is that it can measure the real drilling pressure and torque at the bottom of the well, providing real-time basis for drilling engineers to accurately and quickly adjust drilling parameters, change drilling methods, and drill safely. During the drilling process, the accurate measurement of drilling engineering parameters such as drilling pressure and torque of the drill string is very important for safe and efficient drilling.

[0039] The method for measuring drilling pressure and torque is to arrange the resistance strain gauges in a certain way to form a bridge circuit, stick them on the measured object, use the deformation of the measured object during the force process to produce changes in the resistance strain gauge bridge circuit, and output the voltage signal corresponding to the drilling pressure and torque. By detecting this signal, the dynamically changing torque and drilling pressure in the well can be accurately measured.

[0040] The resistance change ΔR of the resistance strain gauge due to the deformation of the structure is usually measured using a four-arm bridge (Wheatstone bridge), such as Figure 1 As shown in the figure, the resistances of the four bridge arms AB, BC, CD and DA are R1, R2, R3 and R4 respectively. If they are all resistance strain gauges, it is called full bridge connection. When the bridge is in full bridge connection, according to the electrical principle, the voltage output by the bridge is:

[0041]

[0042] If R1R3=R2R4, then U=0, and the bridge is in a balanced state. Before strain measurement, the bridge should be pre-adjusted to balance so that the bridge has no output. Therefore, when the specimen is deformed by force, the strain gauges R1, R2, R3 and R4 attached to it feel the strains ε1, ε2, ε3 and ε4, and the resistance value of each gauge changes accordingly, and the changes are ΔR1, ΔR2, ΔR3 and ΔR4 respectively. The output voltage of the bridge at this time can be obtained from formula (1):

[0043]

[0044] For the resistance strain gauge Ri (i=1,2,3,4)

[0045]

[0046] Among them, K i is the sensitivity coefficient of the strain gauge, ε i is the longitudinal and axial strain value of the strain gauge. If the sensitivity coefficients of the strain gauges constituting the unified bridge are all K, then equation (2) can be rewritten as:

[0047]

[0048] Equation (4) shows that the (ε1-ε2+ε3-ε4) sensed by the strain gauge can be linearly converted into a voltage change U through the bridge. BD .

[0049] Example 1

[0050] This embodiment provides a small signal conditioning circuit system for logging while drilling, such as Figure 2 As shown, it includes a strain bridge module, an amplification module, a filtering module, an A / D conversion module and a microcontroller unit MCU.

[0051] The strain bridge module includes a strain bridge composed of resistance strain gauges attached to the drill string, and the strain bridge includes a drilling pressure measurement strain bridge and a torque measurement strain bridge. The drilling pressure measurement strain bridge and the torque measurement strain bridge respectively form independent data acquisition channels with the amplification module, the filtering module, the A / D conversion module and the microcontroller unit MCU.

[0052] In this embodiment, the strain bridge adopts an equal-arm bridge.

[0053] During the drilling, lowering and pulling out of the drill collar, the stress and movement of different parts of the drill collar / drill string vary greatly. They mainly include: axial tension and pressure, torque, bending moment, centrifugal force, internal and external squeeze of the drill collar, longitudinal vibration, torsional vibration, lateral oscillation, etc. Due to the complex movement of the drill string and drill collar, the drill bit has vortex motion at the bottom of the well, the drilling pressure at the bottom of the well fluctuates greatly, and even the drill bit jumps off the bottom of the well.

[0054] Theoretically, the forces and moments on the drill collar can be simplified as: the drilling pressure applied to the drill bit, the torque transmitted by the drill string, the bending moment caused by the movement of the drill string and the reaction force at the bottom of the hole, and the vibration of the drill bit during drilling. From the perspective of measurement technology, the forces on the drill collar can be simplified as the axial tension, compression and vibration of the thick-walled circular tube, a pair of torques around the axial direction, and the radial bending moment of the drill collar.

[0055] The measurement of tensile, compressive and torsional stress in material mechanics is based on the strain effect of the stressed object and is achieved using the strain principle. Strain gauges are attached at 0 and 90 degrees along the axial direction of the drill collar cylinder, and the magnitude of the tensile and compressive forces on the drill collar is obtained by measuring the resistance change of the strain gauges; strain gauges are attached along the axial direction of the drill collar cylinder at ±45 degrees, and the magnitude of the torsional torque on the drill collar is obtained by measuring the resistance change of the strain gauges.

[0056] Correctly pasting the strain gauge is a key step to ensure accurate measurement. Improper pasting will cause zero drift, creep and other problems. In this embodiment, when subjected to pressure, such as Figure 3 As shown in the figure, when measuring, the strain gauge is pasted in the direction of 90 degrees to the axis, and the total indicated strain is ε'=2(1+ν)ε=2.56ε. When subjected to torque, such as Figure 4 As shown, when measuring, the strain gauge is pasted in a direction of 45 degrees to the axis, and the total indicated strain is ε'=4ε.

[0057] like Figure 3 and Figure 4 As shown, in this embodiment, the resistance strain gauge of the drilling pressure measurement strain bridge is pasted in a direction of 90 degrees to the axis, and the resistance strain gauge of the torque measurement strain bridge is pasted in a direction of 45 degrees to the axis.

[0058] The amplification module includes a two-stage amplification circuit for amplifying the weak voltage signal output by the strain bridge module. The weak voltage signal is a voltage signal output by the strain bridge module caused by the change in resistance of the resistance strain gauge caused by the deformation of the resistance strain gauge during the force application process. The two-stage amplification circuit includes a first-stage amplification circuit and a second-stage amplification circuit, the gain of the first-stage amplification circuit is 100, and the gain of the second-stage amplification circuit is 10.

[0059] The filtering module is used to filter out the noise signal in the output signal of the amplifying module. The filtering module includes a second-order active bandpass filtering circuit, which is used to filter out the high-frequency signal and the low-frequency signal in the signal.

[0060] The A / D conversion module converts the filtered voltage analog signal into a digital signal.

[0061] The microcontroller unit MCU is used to perform data processing on the digital signal processed by the A / D conversion module to obtain measured engineering parameters.

[0062] The logging while drilling tiny signal conditioning circuit system also includes a high-temperature power module circuit, a storage module and a balancing circuit.

[0063] The high temperature power module circuit is used to supply power to each module of the system; the storage module is used to store various parameters obtained during the measurement process; the balancing circuit includes a polarity adjustment circuit and a balancing addition circuit, which are used to eliminate the zero point offset in the initial state.

[0064] Example 2

[0065] This embodiment provides a high-temperature power module circuit that can be used to power downhole instruments, such as Figure 5 As shown, the power supply of the measurement circuit is converted by P5V and N5V high temperature power modules into power for the signal channel and the reference channel.

[0066] The high temperature power module circuit includes an input module, a conversion module and an output module. The input module includes a voltage input terminal for inputting the voltage to be converted; the conversion module is connected to the input module, and the conversion module includes a positive voltage conversion module and a negative voltage conversion module. The negative voltage conversion module uses the output voltage of the positive voltage conversion module as the input voltage; the output module is connected to the conversion module, and the output module includes a voltage output terminal for outputting the converted positive and negative voltages. The input voltage of the input module is 12V to 46V, and the output voltage of the output module is +5V and -5V, which supplies power to the signal channel and the reference channel.

[0067] The positive voltage conversion module includes a converter U1, which includes a VIN pin, a RUN pin, an ISET pin, a SW pin, a VFB pin, a VPRG1 pin, a VPRG2 pin and a SS pin. The converter U1 is a synchronous step-down DC / DC converter, model LTC3630A.

[0068] The negative voltage conversion module includes a negative output regulator U2, and the negative output regulator U2 includes a SW pin, a Vin pin, a D pin, a FB pin, and a SDREF pin.

[0069] The working temperature of the converter U1 of the positive voltage conversion module is -40°C to 150°C, and the working temperature of the negative output regulator U2 of the negative voltage conversion module is -40°C to 85°C. The circuit board size of the high temperature power module circuit is: 33mm×22mm, and it is sealed with metal potting.

[0070] The high-temperature module power circuit provided in this embodiment is resistant to high temperatures, stamping, and moisture, and is particularly suitable for use in the construction of power supply systems for oil exploration downhole instruments, geophysical detection instruments, vehicles and transportation vehicles, telecommunications and network infrastructure, enterprises and high-performance computing, etc.

[0071] The maximum operating temperature of the high-temperature power module circuit is not less than 160℃. The designed output voltages are 3.3V, 5V, 7V, 9V, 12V, 15V, 18V, 24V, 36V, and 48V, that is, it can output any one of them, or any combination of two or three of them. When in use, they can be connected as needed to form various forms of output combinations for easy use.

[0072] Example 3

[0073] This embodiment provides a signal amplification circuit, such as Figure 6 As shown, since the output voltage of the strain gauge bridge is a very weak signal, in order to detect this signal, it is amplified by a signal amplifier circuit. Since the output signal is accompanied by strong noise, it is necessary to improve the common mode rejection ratio of the entire circuit, and the gain of the amplifier circuit cannot be too large, otherwise it will cause saturation. For this reason, a two-stage amplifier circuit method is adopted, including a first-stage amplifier circuit and a second-stage amplifier circuit.

[0074] The first-stage amplifier circuit includes a first amplifier, which is a general instrumentation amplifier and can obtain a sufficiently high common-mode rejection ratio. The gain is determined by the equivalent resistance Rg between pin 1 and pin 8 of the first amplifier. In this embodiment, Rg is the twenty-second resistor R22. The gain calculation formula is as follows:

[0075] G=1+49.4K / Rg=100 (5)

[0076] The 49.4KΩ in equation (5) is the sum of two internal feedback resistors. These on-chip metal film resistors are laser trimmed to absolute accuracy. The accuracy and temperature coefficient of these internal resistors are included in the amplifier gain accuracy and temperature drift specifications. It should be noted that the first amplifier has a higher accuracy. In order to ensure accuracy and minimize the conversion of differential mode signals to common mode signals, the resistors must achieve a one percent accuracy. The first amplifier has very low offset voltage, temperature drift and high common mode rejection. Its supply voltage is as low as ±2.25V and the quiescent current is only 700uA, which is ideal for battery-powered systems. The internal input protection can withstand ±40V voltage without damage.

[0077] The output voltage after the first stage amplifier circuit is

[0078] Uo1=(Vb-Vd)*G (6)

[0079] The second stage amplifier circuit includes a second amplifier that amplifies the signal by a factor of 10. The second amplifier is a single supply, 4MHz bandwidth amplifier with rail-to-rail input and output characteristics. This amplifier is suitable for single supply applications that require AC performance and precision DC performance. The combination of bandwidth, low noise and precision makes it suitable for a variety of applications such as filters and instrumentation.

[0080] Example 4

[0081] This embodiment provides a balancing circuit. Figure 7 and Figure 8 As shown, it includes a polarity adjustment circuit and a balancing addition circuit, and the output end of the polarity adjustment circuit is connected to the input end of the addition circuit.

[0082] Figure 7 In the circuit, if R10 is disconnected and R4 is connected, it is a common-phase proportional amplifier. If R10 is connected and R4 is disconnected, it is an inverting proportional amplifier. By adjusting the values ​​of R9 and R16, the size of the reference signal is changed, and the output signal is Uo3.

[0083] like Figure 8 The signal channel and reference channel addition circuit shown in the figure is a two-input positive phase addition circuit, where the input signals are Uo2 and Uo3, which are connected to the non-inverting input terminal of the operational amplifier through the twelfth resistor R12 and the fifteenth resistor R15 respectively. The reverse input terminal is grounded through the balancing resistor R8. The output voltage of the addition circuit is equal to the sum of the input voltages of each branch, and the addition operation of multiple input signals can be realized.

[0084] In the specific implementation process, the reference signal is input from the input end of the balancing circuit, that is, from the input end of the polarity adjustment circuit, and the amplifier is selected according to the polarity of the signal. When the tenth resistor R10 is disconnected and the fourth resistor R4 is connected, the polarity adjustment circuit is a common-phase proportional amplifier; when the tenth resistor R10 is connected and the fourth resistor R4 is disconnected, the polarity adjustment circuit is an inverting proportional amplifier, and the processed signal Uo3 is output from the output end of the polarity adjustment circuit. The size of the reference signal can be changed by adjusting the resistance values ​​of the ninth resistor R9 and the sixteenth resistor R16.

[0085] The adding circuit includes two input terminals, which are used to input the bridge signal and the reference signal respectively. One of the input terminals is connected to the output terminal of the polarity adjustment circuit, and the other input terminal is connected to the output terminal of the amplifier circuit. The amplifier circuit is used to amplify the output signal of the collected strain bridge. The reference signal adjusted by the polarity adjustment circuit and the bridge signal amplified by the amplifier circuit are opposite. After passing through the adding circuit, the unbalance in the bridge circuit can be eliminated.

[0086] Example 5

[0087] This embodiment provides a second-order Butterworth bandpass filter, whose circuit diagram is as shown in FIG. Fig. 9 As shown, in this embodiment, the center frequency is 100 Hz, the bandwidth is 10 Hz, and the quality factor Q=10.

[0088] Add an AC signal with an amplitude of 1V to the bandpass filter and perform AC analysis. The simulated waveform is as follows: Fig.10 shown.

[0089] Add a sine wave signal to the bandpass filter with an amplitude of 1V, a frequency of 100Hz, and an offset of 0V. Perform transient analysis and the simulated waveform is as follows: Fig.11 shown.

[0090] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A small signal conditioning circuit system for logging while drilling, characterized in that: include: The strain bridge module comprises a strain bridge composed of a resistance strain gauge pasted on a drill string, wherein the strain bridge can convert the change of the resistance value of the resistance strain gauge into a voltage signal; an amplification module comprises a two-stage amplification circuit for amplifying the voltage signal output by the strain bridge module; a filtering module is used to filter out the noise signal in the output signal of the amplification module, wherein the filtering module comprises a second-order active bandpass filtering circuit for filtering out the high-frequency signal and the low-frequency signal in the signal; an A / D conversion module converts the filtered voltage analog signal into a digital signal; a microcontroller unit MCU is used to perform data processing on the digital signal processed by the A / D conversion module to obtain the measured engineering parameters; the circuit system also comprises a polarity The adjusting circuit and the balancing adding circuit are connected. The output end of the polarity adjusting circuit is connected to the input end of the balancing adding circuit. The circuit system is used to eliminate the unbalance of the AC strain bridge. The reference signal is input from the input end of the polarity adjusting circuit. The reference signal is selected to pass through an in-phase proportional amplifier or an inverse proportional amplifier according to the polarity of the reference signal. The processed output signal of the reference signal is output from the output end of the polarity adjusting circuit. The adding circuit includes two input ends, which are used to input a bridge signal and a reference signal respectively. One of the input ends is connected to the output end of the polarity adjusting circuit, and the other input end is connected to the output end of an amplifier circuit. The amplifier circuit is used to amplify the output signal of the collected strain bridge. The reference signal adjusted by the polarity adjustment circuit is opposite to the bridge signal amplified by the amplifier circuit, and the imbalance in the bridge circuit can be eliminated after passing through the balancing addition circuit.

2. A logging while drilling tiny signal conditioning circuit system according to claim 1, characterized in that: The strain bridge includes a bit pressure measurement strain bridge and a torque measurement strain bridge.

3. A logging while drilling tiny signal conditioning circuit system according to claim 2, characterized in that: The drilling pressure measurement strain bridge and the torque measurement strain bridge respectively form independent data acquisition channels with the amplification module, the filtering module, the A / D conversion module and the microcontroller unit MCU.

4. A logging while drilling tiny signal conditioning circuit system according to claim 3, characterized in that: The resistance strain gauge of the bit pressure measurement strain bridge is pasted in a direction of 90 degrees to the axis, and the resistance strain gauge of the torque measurement strain bridge is pasted in a direction of 45 degrees to the axis.

5. A logging while drilling tiny signal conditioning circuit system according to claim 4, characterized in that: The strain bridge is an equal-arm bridge.

6. The logging while drilling tiny signal conditioning circuit system according to claim 1, characterized in that: The two-stage amplifier circuit includes a first-stage amplifier circuit and a second-stage amplifier circuit. The gain of the first-stage amplifier circuit is 100, and the gain of the second-stage amplifier circuit is 10.

7. The LWD micro-signal conditioning circuit system according to claim 1, characterized in that: The circuit system also includes a high-temperature power module circuit for supplying power to each module of the system, and the supply voltage of the high-temperature power module circuit is ±5V.

8. The LWD micro-signal conditioning circuit system according to claim 7, characterized in that: The circuit system also includes a storage module for storing various engineering parameters obtained during the measurement process.

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