A device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method

Abstract

The invention discloses a device for realizing scale monitoring of oilfield gathering and transportation pipeline based on differential thermal resistance method, which relates to the technical field of oilfield pipeline corrosion and protection, and comprises a differential thermal resistance probe and a differential signal acquisition circuit. The differential thermal resistance probe is inserted into the pipe wall of the oilfield gathering and transportation pipeline, and two temperature sensors are embedded in the differential thermal resistance probe; the first temperature sensor protrudes from the bottom plane of the differential thermal resistance probe, and the second temperature sensor is lower than the bottom plane of the probe, forming a concave cavity for depositing scale; the voltage drops VA and VB formed by the first temperature sensor and the second temperature sensor are amplified by a two-stage amplifier, and then converted into digital by a converter, and finally read, stored and converted into temperature by a single chip microcomputer; the device can measure the scale deposition state on the surface of the oilfield gathering and transportation pipeline, and adopts the differential thermal resistance probe to have good sensitivity to the temperature difference change caused by the scale coverage.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield pipeline corrosion and protection, and in particular to a device for realizing scaling monitoring of oilfield gathering and transportation pipelines based on a differential thermal resistance method. Background Art

[0002] As my country's oilfield exploitation gradually enters the late stage, crude oil exploitation in major oilfields has entered a high water content period, and the comprehensive water content of produced fluids has increased year by year, even exceeding 90%. Due to the high mineralization (>10000mg / L), high Cl- content and high water temperature (>60℃) of the reinjected wastewater, coupled with the synergistic effects of H2S, CO2, SRB, etc., scaling and corrosion of surface pipelines and downhole pipes are often caused. Pipeline scaling not only increases water injection pressure and energy consumption, but also provides favorable conditions for microbial corrosion or concentration corrosion under scale. Unlike corrosion monitoring, scaling monitoring, especially online monitoring, is very difficult, and there are few related literature reports.

[0003] At present, there are many patents on how to prevent scaling, but there are few reports on on-site scaling monitoring. Moreover, since there is no hot and cold water heat exchange circuit in the oil field surface pipeline network, the fluid in the pipe can only dissipate heat to the atmosphere through the pipe wall, so the temperature difference measurement through the hot and cold circuit is not suitable. Chinese patent CN105659075 proposes a method for monitoring sediments, which uses electrodes to measure the complex impedance of the fluid to determine the components that may be contained in the fluid, and obtains the influence relationship of each component in the solution on the impedance based on a series of experiments, determines the specific components of the fluid, and thus monitors the formation of sediments and the content of chemical inhibitors. However, this technology cannot directly monitor the scaling trend of the fluid on the surface of the pipeline, but can only measure the conductivity of the fluid. Chinese patent CN201740749U provides a circulating cooling water scaling condition detection device, which obtains the corrosion scaling condition at different times by monitoring the relationship between the temperature rise value and time of the temperature in the distilled water storage tank under scaling and non-scaling conditions of the probe fouling monitoring device. The device can realize online monitoring of the structural state of the circulating water system without stopping production. However, there are some uncertain factors based on heat transfer efficiency. When the scale layer is relatively loose, the local heat transfer area increases, and an error occurs between the temperature rise value and the actual value, resulting in judgment failure. In addition, the device is too complicated and difficult to apply on site. Chinese patent CN2017111926939 provides an online scaling monitoring device for oilfield water injection pipelines, including a scaling monitoring controller and an online scaling monitoring sensor. The scaling monitoring controller includes a current amplifier, a power amplifier, a main polarization circuit, two sine wave generators, two potential current signal data collectors, a communication interface, a power module, and an MCU controller. The online scaling sensor is connected to the power amplifier and the current amplifier through two cables; the online scaling monitoring sensor is mainly composed of two metal wire electrodes, a stainless steel support column, a bisque ceramic tube, a heating wire, a polytetrafluoroethylene oil-proof cover, a polytetrafluoroethylene oil-proof shell and a 6-core aviation plug-in assembly. The device has a complex structure and a high failure rate. It can be seen that there is no method in the prior art that can effectively realize scaling monitoring of oilfield water injection pipelines.

[0004] Therefore, it is necessary to develop an efficient and easy-to-implement online scale layer monitoring sensor and data acquisition and analysis device for rapid evaluation of the effectiveness of scale prevention and removal measures. Summary of the invention

[0005] The present invention provides a device for monitoring the scaling of oilfield gathering and transportation pipelines based on the differential thermal resistance method, which can measure the scale deposition state on the surface of the oilfield gathering and transportation pipelines online. The differential thermal resistance probe has good sensitivity to the temperature difference change caused by the dirt coverage, and is suitable for monitoring the scaling of oilfield gathering and transportation pipelines with the characteristic of heat dissipation to the environment.

[0006] The technical solution of the present invention is: a device for monitoring the scaling of oilfield gathering and transportation pipelines based on the differential thermal resistance method, comprising a differential thermal resistance probe and a differential signal acquisition circuit, wherein the differential thermal resistance probe is inserted into the pipe wall of the oilfield gathering and transportation pipeline and fixed, and the bottom plane of the differential thermal resistance probe is flush with the inner wall of the pipeline; two temperature sensors are embedded in the differential thermal resistance probe, namely a first temperature sensor and a second temperature sensor; the first temperature sensor protrudes from the bottom plane of the differential thermal resistance probe and extends into the pipeline, while the second temperature sensor is lower than the bottom surface of the probe, and forms a concave cavity for depositing scaling with the bottom plane of the differential thermal resistance probe;

[0007] The differential signal acquisition circuit includes a constant current source, a first amplifier, a second amplifier, a third amplifier, a converter and a single-chip microcomputer. The first temperature sensor and the second temperature sensor both adopt a four-wire measurement method. The input end of the second temperature sensor is electrically connected to the Vcc power supply end of the constant current source. The first temperature sensor and the second temperature sensor are connected in series, and the output end of the first temperature sensor is electrically connected to the ground end of the constant current source; the positive input end and the negative input end of the first amplifier are respectively connected to the two signal output ends of the first temperature sensor, the positive input end and the negative input end of the second amplifier are respectively connected to the two signal output ends of the second temperature sensor, the positive input end and the negative input end of the third amplifier are respectively connected to the signal output ends of the first amplifier and the second amplifier; the converter is electrically connected to the two signal output ends of the third amplifier, and the single-chip microcomputer is electrically connected to the converter.

[0008] Preferably, the first temperature sensor protrudes from the bottom plane of the differential thermal resistance probe by 1 mm to 5 mm, and the second temperature sensor is lower than the bottom plane of the probe by 1 mm to 5 mm.

[0009] Preferably, the output current I of the constant current source is 0.1-10 mA.

[0010] Preferably, the first amplifier and the second amplifier are instrumentation amplifiers.

[0011] Preferably, the third amplifier is a PGA programmable instrumentation amplifier.

[0012] Preferably, the converter is a 16-24 bit Σ-Δ ADC converter.

[0013] Preferably, the single chip microcomputer is STM32.

[0014] Preferably, in order to effectively filter out power frequency interference, a 50Hz / 60Hz power frequency notch filter is embedded in the converter.

[0015] Preferably, the first temperature sensor and the second temperature sensor are made of thermal resistors or thermocouples.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) This device can measure the dirt deposition state on the surface of oil field gathering and transportation pipelines. The differential thermal resistance probe has good sensitivity to the temperature difference caused by dirt coverage.

[0018] (2) This device uses a four-wire differential thermal resistor to compensate for the thermal potential between the temperature sensor wire resistance and the dissimilar metal wires.

[0019] (3) The temperature sensors in the temperature difference measuring probe of the device are asymmetrically designed. The second temperature sensor has a cavity at the bottom, which can induce scale deposition and is used to sense the temperature of the scale layer. The first temperature sensor protrudes into the fluid and is not prone to scale formation on the surface, so it is used to sense the fluid temperature.

[0020] (4) Due to the different thermal conductivity of the scale layer and the metal body of the probe, when the fluid in the pipe transfers heat to the environment along the radial direction of the pipe, there is a slight difference in the thermal resistance of the two sensors, and a slight temperature difference occurs between the first and second temperature sensors. Using a four-wire system and a two-stage differential amplifier circuit, the thermal resistance resolution can reach 300μΩ and the temperature difference resolution can reach 0.001℃.

[0021] (5) The scale layer thermal resistance monitoring probe and data acquisition device in the device have a simple and compact structure, strong repeatability and operability, and are suitable for scaling monitoring of oil field gathering and transportation pipelines with the characteristic of heat dissipation to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the installation of a differential thermal resistance probe for pipeline scaling monitoring;

[0023] Figure 2 It is a structural schematic diagram of a differential thermal resistance probe;

[0024] Figure 3 This is a schematic diagram of a differential signal acquisition circuit;

[0025] Figure 4 It is an overall schematic diagram of the present invention;

[0026] Figure 5 It is a schematic diagram of embodiment 1;

[0027] Figure 6 This is the scale layer temperature difference standard curve of Example 3.

[0028] In the figure: 1. first temperature sensor, 2. second temperature sensor, 3. differential thermal resistance probe, 4. recessed cavity, 5. pipeline, 6. scale layer, 10. single chip microcomputer, 11. converter, 12. third amplifier, 13. constant current source, 14. first amplifier, 15. second amplifier. DETAILED DESCRIPTION

[0029] The present invention is further described below with reference to the accompanying drawings and embodiments.

[0030] Embodiment 1

[0031] Reference Figure 1-5 As shown in the figure, the fouling thermal resistance monitoring method requires measuring the temperature difference between the fluid inlet and outlet of a section of pipe 5. When the heat transfer efficiency of the inner wall of pipe 5 decreases due to scaling, the temperature difference between the fluid outlet and inlet of pipe 5 will decrease. According to the definition of the thermal resistance of the scale layer 6, the thermal resistance R f

[0032]

[0033] In formula (1), T ws T is the interface temperature between the pipe wall and the scale layer 6, which can be accurately measured. In this embodiment, the second temperature sensor 2 in the differential thermal resistance probe 3 is used for measurement. s is the interface temperature between the scale layer 6 and the fluid, also known as the surface temperature of the scale layer 6, which can be obtained by measuring the temperature of the fluid in the pipe. In this embodiment, the first temperature sensor 1 is used for measurement. q is the heat flux density of the scale layer 6, m is the mass of the fluid per unit time, c p is the fluid density, T fo ,T fi are the outlet and inlet temperatures of the fluid, d is the pipe diameter, and l is the pipe length.

[0034] As the thickness of the scale layer 6 on the inner wall of the pipe 5 increases, q decreases accordingly, and R f Increase, so that the temperature difference between the upper and lower surfaces of the scale layer 6 increases. Therefore, by accurately measuring the difference between the two temperature sensors built into the differential thermal resistance probe 3, the density or thickness of the scale layer 6 can be indicated.

[0035] Embodiment 2

[0036] In view of the environmental parameters of the oil field oil pipeline, where the fluid temperature can vary from 40°C to 95°C, the fluid heat flow dissipates heat to the environment through the pipe 5 wall and the insulation layer, remove part of the insulation layer on the outer wall of the pipe 5, open a hole at the bottom of the pipe 5 or in any other clock direction, and install the differential thermal resistance probe 3, so that the heat of the pipe 5 fluid can be dissipated outward through the metal-based probe. Since the installation positions of the two temperature sensors in the probe have a high height difference, and there is a concave space at the bottom of the second temperature sensor 2, scale deposition is easy to occur. The first temperature sensor 1 protrudes from the bottom of the probe to avoid scaling.

[0037] The first temperature sensor 1 and the second temperature sensor 2 are made of Pt100 thermal resistors. The output current of the constant current source 13 is adjusted to 1mA. Considering that the sensitivity of Pt100 between -20℃ and 100℃ is 0.004Ω / 0.01℃,

[0038]

[0039] R 0 is the resistance of Pt100 at 0℃, the nominal value is 100Ω, RT is the resistance of Pt100 at T℃, α=0.003916Ω / (Ω·℃). Taking the Pt100 temperature sensor as an example, the voltage difference V A +-V A -=4μV / 0.01℃, the magnification of the first amplifier 14 and the second amplifier 15 is set to 100 times, and the magnification of the third amplifier 12 is set to 10 times, then the final gain can reach 4mV / 0.01℃. The converter 11 is a Σ-ΔADC converter 11 for digital-to-analog conversion. The converter 11 adopts ADS1210 in this embodiment, which can achieve 24bit resolution and can distinguish 0.1mV voltage change within the analog voltage measurement range of ±5V. Therefore, the circuit in this patent can distinguish 0.1mV / 4mV×0.01=0.00025℃ temperature difference change. It can be seen that the converter 11 has good sensitivity to the temperature difference between temperature sensors.

[0040] Embodiment 3

[0041] According to the environmental parameters of the oil field pipeline, a DN200 20# carbon steel pipeline 5 was used, and the pipe was filled with oil field sewage with scaling tendency, including Ca 2+ The concentration is 200 mg / L, HCO 3 - The ion concentration is 1000 mg / L, pH = 6.5, the temperature is maintained at 60°C, the outer wall temperature of the tube is 50°C, and the differential thermal resistance probe 3 is set according to the attached Figure 1The differential thermal resistance probe 3 is inserted into the pipe 5. As the sewage gradually concentrates, 0.5 mm thick CaCO can be deposited on the surface of the second temperature sensor 2 after 10 days. 3 Scale layer 6, during this period of time, the temperature difference ΔT between the two temperature sensors gradually increased from 0.2℃ to 0.6℃. The entire temperature difference change curve is shown in the attached figure. Figure 6 As shown. At this time, the thermal resistance of the scale layer 6 calculated based on this probe = (0.6-0.2) / 0.5 = 0.8°C / mm. If the measured temperature difference increases, the surface scale layer 6 will further thicken. Based on the temperature difference standard curve of scale layer 6 with different chemical composition and thickness, the thermal resistance, thickness or density of the scale layer 6 on the inner wall of the pipeline 5 can be calculated according to the measured temperature difference value.

[0042] Embodiment 4

[0043] Reference Figure 4 As shown, a device for monitoring scaling of an oilfield gathering and transportation pipeline 5 based on a differential thermal resistance method comprises a differential thermal resistance probe 3 and a differential signal acquisition circuit. The differential thermal resistance probe 3 is inserted into the pipe wall of the oilfield gathering and transportation pipeline 5, and the bottom plane of the differential thermal resistance probe 3 is flush with the inner wall of the pipeline 5, ensuring that the fluid shear force on the bottom surface of the differential thermal resistance probe 3 is consistent with the inner wall of the pipeline 5, thereby more truly reflecting the scaling state in the pipeline 5; two temperature sensors are embedded in the differential thermal resistance probe 3, namely a first temperature sensor 1 and a second temperature sensor 2; the first temperature sensor 1 protrudes from the bottom plane of the differential thermal resistance probe 3 and extends into the pipeline by 3 mm, while the second temperature sensor 2 is 3 mm lower than the bottom surface of the probe, and forms a concave cavity 4 for depositing scaling with the bottom plane of the differential thermal resistance probe 3;

[0044] Reference Figure 3 As shown, the differential signal acquisition circuit includes a constant current source 13, a first amplifier 14, a second amplifier 15, a third amplifier 12, a converter 11 and a single-chip computer 10. The first amplifier 14 and the second amplifier 15 are instrument amplifiers, and the third amplifier 12 is a PGA programmable instrument amplifier. The first temperature sensor 1 and the second temperature sensor 2 both adopt a four-wire measurement method. The input end of the second temperature sensor 2 is electrically connected to the Vcc power supply end of the constant current source 13. The first temperature sensor 1 and the second temperature sensor 2 are connected in series, and the output end of the first temperature sensor 1 is electrically connected to the ground end of the constant current source 13; the positive input end and the negative input end of the first amplifier 14 are respectively connected to the two signal output ends of the first temperature sensor 1, the positive input end and the negative input end of the second amplifier 15 are respectively connected to the two signal output ends of the second temperature sensor 2, and the positive input end and the negative input end of the third amplifier 12 are respectively connected to the output ends of the first amplifier 14 and the second amplifier 15; the converter is electrically connected to the two output ends of the third amplifier 12, and the single-chip computer 10 is electrically connected to the converter 11.

[0045] The temperature sensor in the temperature difference measuring probe of the device adopts an asymmetric design. The second temperature sensor 2 has a recessed cavity 4 at the bottom, which can induce the deposition of the scale layer 6 and is used to sense the temperature of the scale layer 6. The first temperature sensor 1 protrudes into the fluid and is not prone to scaling on the surface, so it is used to sense the fluid temperature.

[0046] Due to the different thermal conductivity of the scale layer 6 and the metal body of the probe, when the fluid in the pipe transfers heat to the environment radially along the pipe 5, there is a slight difference in the thermal resistance of the two sensors, and a slight temperature difference occurs between the first temperature sensor 1 and the second temperature sensor 2. Using a four-wire system and a two-stage differential amplifier circuit, the thermal resistance resolution can reach 300μΩ and the temperature difference resolution can reach 0.001℃.

[0047] When in use, after a period of transport and deposition, a 3 mm thick scale layer 6 is deposited on the surface of the second temperature sensor 2; the first temperature sensor 1, the second temperature sensor 2 and the constant current source 13 form a current loop, and the constant current outputs current, forming voltage drops VA and VB on the potential lines of the first temperature sensor 1 and the second temperature sensor 2, VA and VB are amplified by ×G1 times by the first amplifier 14 and the second amplifier 15, and the voltage signals output by the first amplifier 14 and the second amplifier 15 are sampled and amplified by the third amplifier 12 for differential signal sampling, and the amplification factor is set to ×G2, then the third amplifier 12 outputs an analog signal with a voltage of (VA-VB)×G1×G2, the analog signal is converted into digital by the converter 11, and finally read, stored and temperature converted by the single-chip microcomputer 10. The voltage signal collected by the single chip microcomputer 10 is linearly correlated with the temperature difference at the bottom of the first temperature sensor 1 and the second temperature sensor 2, and the temperature difference between the two is proportional to the amount of scale layer 6 deposited in the cavity at the bottom of the second sensor. Based on the change of the temperature difference between the first temperature sensor 1 and the second temperature sensor 2 over time, it can be used to estimate the amount of scale layer 6 deposited on the probe surface.

[0048] Embodiment 5

[0049] Reference Figure 4 As shown, a device for realizing scaling monitoring of oilfield gathering and transportation pipeline 5 based on differential thermal resistance method comprises differential thermal resistance probe 3 and differential signal acquisition circuit, the differential thermal resistance probe 3 is inserted into the pipe wall of oilfield gathering and transportation pipeline 5, and the bottom plane of differential thermal resistance probe 3 is flush with the inner wall of pipeline 5, so as to ensure that the fluid shear force on the bottom surface of differential thermal resistance probe 3 is consistent with the inner wall of pipeline 5, thereby more truly reflecting the scaling state in pipeline 5; two temperature sensors are embedded in differential thermal resistance probe 3, namely, first temperature sensor 1 and second temperature sensor 2, and are encapsulated and cured by thermal conductive resin; the first temperature sensor 1 protrudes from the bottom plane of differential thermal resistance probe 3 and extends into the pipeline by 5mm, while the second temperature sensor 2 is 5mm lower than the bottom surface of the probe, and forms a concave cavity 4 for depositing scaling with the bottom plane of differential thermal resistance probe 3;

[0050] Reference Figure 3 As shown, the differential signal acquisition circuit includes a constant current source 13, a first amplifier 14, a second amplifier 15, a third amplifier 12, a converter 11 and a single-chip computer 10. The first amplifier 14 and the second amplifier 15 are instrumentation amplifiers, the third amplifier 12 is a PGA programmable instrumentation amplifier, and the converter 11 is a 16-24 bit Σ-Δ ADC converter 11. The first temperature sensor 1 and the second temperature sensor 2 both adopt a four-wire measurement method. The input end of the second temperature sensor 2 is electrically connected to the Vcc power supply end of the constant current source 13. The first temperature sensor 1 and the second temperature sensor 2 are connected in series, and the output end of the first temperature sensor 1 is electrically connected to the ground end of the constant current source 13; the positive input end and the negative input end of the first amplifier 14 are respectively connected to the two signal output ends of the first temperature sensor 1, the positive input end and the negative input end of the second amplifier 15 are respectively connected to the two signal output ends of the second temperature sensor 2, and the positive input end and the negative input end of the third amplifier 12 are respectively connected to the output ends of the first amplifier 14 and the second amplifier 15; the converter is electrically connected to the two output ends of the third amplifier 12, and the single-chip computer 10 is electrically connected to the converter 11.

[0051] When in use, after a period of transport and deposition, a 5mm thick scale layer 6 is deposited on the surface of the second temperature sensor 2; the first temperature sensor 1, the second temperature sensor 2 and the constant current source 13 form a current loop, and the constant current output current I=0.1~10mA forms voltage drops VA and VB on the potential lines of the first temperature sensor 1 and the second temperature sensor 2, VA and VB are amplified by ×G1 times by the first amplifier 14 and the second amplifier 15, and the voltage signals output by the first amplifier 14 and the second amplifier 15 are sampled and amplified by the third amplifier 12 for differential signal, and the amplification factor is set to ×G2, then the output voltage of the third amplifier 12 is an analog signal of (VA-VB)×G1×G2, and the analog signal is converted to digital by the 16~24bitΣ-ΔADC converter 11, and finally read, stored and temperature converted by the single chip 10. The differential voltage acquisition circuit of this embodiment can distinguish voltage signals of 0.1μV~1μV, and a 50Hz / 60Hz power frequency trap is embedded in the ADC converter 11, which can effectively filter out power frequency interference. The voltage signal collected by the single chip microcomputer 10 is linearly correlated with the temperature difference at the bottom of the first temperature sensor 1 and the second temperature sensor 2, and the temperature difference between the two is proportional to the amount of scale layer 6 deposited in the cavity at the bottom of the second sensor. Based on the change of the temperature difference between the first temperature sensor 1 and the second temperature sensor 2 over time, it can be used to estimate the amount of scale layer 6 deposited on the probe surface.

[0052] Example 6

[0053] Reference Figure 4As shown, a device for realizing scaling monitoring of oilfield gathering and transportation pipeline 5 based on differential thermal resistance method comprises differential thermal resistance probe 3 and differential signal acquisition circuit, the differential thermal resistance probe 3 is inserted into the pipe wall of oilfield gathering and transportation pipeline 5, and the bottom plane of differential thermal resistance probe 3 is flush with the inner wall of pipeline 5, so as to ensure that the fluid shear force on the bottom surface of differential thermal resistance probe 3 is consistent with the inner wall of pipeline 5, thereby more truly reflecting the scaling state in pipeline 5; two temperature sensors are embedded in differential thermal resistance probe 3, namely, first temperature sensor 1 and second temperature sensor 2, and are encapsulated and cured by thermal conductive resin; the first temperature sensor 1 and the second temperature sensor 2 are made of thermal resistors or thermocouples, the first temperature sensor 1 protrudes from the bottom plane of differential thermal resistance probe 3 and extends into the pipeline by 1mm, while the second temperature sensor 2 is 1mm lower than the bottom surface of the probe, and forms a concave cavity 4 for depositing scaling with the bottom plane of differential thermal resistance probe 3;

[0054] Reference Figure 3 As shown, the differential signal acquisition circuit includes a constant current source 13, a first amplifier 14, a second amplifier 15, a third amplifier 12, a converter 11 and a single-chip computer 10. The first amplifier 14 and the second amplifier 15 are instrumentation amplifiers, the third amplifier 12 is a PGA programmable instrumentation amplifier, the converter 11 is a 16-24 bit Σ-Δ ADC converter 11, and the single-chip computer 10 is STM32. The first temperature sensor 1 and the second temperature sensor 2 both adopt a four-wire measurement method. The input end of the second temperature sensor 2 is electrically connected to the Vcc power supply end of the constant current source 13. The first temperature sensor 1 and the second temperature sensor 2 are connected in series, and the output end of the first temperature sensor 1 is electrically connected to the ground end of the constant current source 13; the positive input end and the negative input end of the first amplifier 14 are respectively connected to the two signal output ends of the first temperature sensor 1, the positive input end and the negative input end of the second amplifier 15 are respectively connected to the two signal output ends of the second temperature sensor 2, and the positive input end and the negative input end of the third amplifier 12 are respectively connected to the output ends of the first amplifier 14 and the second amplifier 15; the converter is electrically connected to the two output ends of the third amplifier 12, and the single-chip computer 10 is electrically connected to the converter 11.

[0055] This embodiment uses a four-wire differential thermal resistor to compensate for the thermoelectric potential between the temperature sensor wire resistance and the dissimilar metal wire. This device can measure the dirt deposition state on the surface of the oil field gathering pipeline 5, and the differential thermal resistance probe 3 has good sensitivity to the temperature difference caused by dirt coverage.

[0056] Due to the different thermal conductivity of the scale layer 6 and the metal body of the probe, when the fluid in the pipe transfers heat to the environment radially along the pipe 5, there is a slight difference in the thermal resistance of the two sensors, and a slight temperature difference occurs between the first temperature sensor 1 and the second temperature sensor 2. Using a four-wire system and a two-stage differential amplifier circuit, the thermal resistance resolution can reach 300μΩ and the temperature difference resolution can reach 0.001℃.

[0057] When in use, after a period of transport and deposition, a 1 mm thick scale layer 6 is deposited on the surface of the second temperature sensor 2; the first temperature sensor 1, the second temperature sensor 2 and the constant current source 13 form a current loop, and the constant current output current I=0.1~10mA forms voltage drops VA and VB on the potential lines of the first temperature sensor 1 and the second temperature sensor 2, VA and VB are amplified by ×G1 times by the first amplifier 14 and the second amplifier 15, and the voltage signals output by the first amplifier 14 and the second amplifier 15 are sampled and amplified by the third amplifier 12 for differential signal sampling, and the amplification factor is set to ×G2, then the third amplifier 12 outputs an analog signal with a voltage of (VA-VB)×G1×G2, and the analog signal is converted into digital by a 16~24 bit Σ-ΔADC converter 11, and finally read, stored and temperature converted by the STM32 microcontroller 10. The differential voltage acquisition circuit of this embodiment can distinguish voltage signals of 0.1μV to 1μV, and a 50Hz / 60Hz power frequency notch filter is embedded in the ADC converter 11, which can effectively filter out power frequency interference. The voltage signal collected by the STM32 microcontroller 10 is linearly related to the temperature difference at the bottom of the first temperature sensor 1 and the second temperature sensor 2, and the temperature difference between the two is proportional to the amount of scale layer 6 deposited in the cavity at the bottom of the second sensor. Based on the change of the temperature difference between the first temperature sensor 1 and the second temperature sensor 2 over time, it can be used to estimate the amount of scale layer 6 deposited on the probe surface.

[0058] The present invention is not limited to the above-mentioned embodiments. Various changes can be made within the knowledge scope of those skilled in the art without departing from the spirit of the present invention. The changed contents still fall within the protection scope of the present invention.

Claims

1. A device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method, characterized in that: It comprises a differential thermal resistance probe and a differential signal acquisition circuit. The differential thermal resistance probe is inserted into the pipe wall of the oil field gathering and transportation pipeline and fixed, and the bottom plane of the differential thermal resistance probe is flush with the inner wall of the pipeline. Two temperature sensors are embedded in the differential thermal resistance probe, namely a first temperature sensor and a second temperature sensor. The first temperature sensor protrudes from the bottom plane of the differential thermal resistance probe and extends into the pipeline, while the second temperature sensor is lower than the bottom surface of the probe, and forms a concave cavity for depositing scale with the bottom plane of the differential thermal resistance probe. The differential signal acquisition circuit includes a constant current source, a first amplifier, a second amplifier, a third amplifier, a converter and a single-chip microcomputer. The first temperature sensor and the second temperature sensor both adopt a four-wire measurement method. The input end of the second temperature sensor is electrically connected to the Vcc power supply end of the constant current source. The first temperature sensor and the second temperature sensor are connected in series, and the output end of the first temperature sensor is electrically connected to the ground end of the constant current source; the positive input end and the negative input end of the first amplifier are respectively connected to the two signal output ends of the first temperature sensor, the positive input end and the negative input end of the second amplifier are respectively connected to the two signal output ends of the second temperature sensor, and the positive input end and the negative input end of the third amplifier are respectively connected to the signal output ends of the first amplifier and the second amplifier; the converter is electrically connected to the two signal output ends of the third amplifier, and the single-chip microcomputer is electrically connected to the converter; The first amplifier and the second amplifier are instrumentation amplifiers; The third amplifier is a PGA programmable instrumentation amplifier.

2. The device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method according to claim 1 is characterized in that: The first temperature sensor protrudes from the bottom plane of the differential thermal resistance probe by 1 mm to 5 mm, and the second temperature sensor is lower than the bottom plane of the probe by 1 mm to 5 mm.

3. The device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method according to claim 1 is characterized in that: The output current I of the constant current source is 0.1-10 mA.

4. The device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method according to claim 1 is characterized in that: The converter is a 16-24 bit Σ-Δ ADC converter.

5. The device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method according to claim 1 is characterized in that: The single chip microcomputer is STM32.

6. The device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method according to claim 1 or 4, characterized in that: A 50Hz / 60Hz power frequency trap is embedded in the converter.

7. The device for monitoring scaling of oilfield gathering and transportation pipelines based on differential thermal resistance method according to claim 1 is characterized in that: The first temperature sensor and the second temperature sensor are made of thermal resistors or thermocouples.

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