A downhole polymer viscosity measurement method and a viscometer

Abstract

The present disclosure relates to a method for measuring the viscosity of downhole polymers and a viscometer. The viscosity measurement method includes: placing a motor, a magnetically coupled inner rotor, and a first Hall sensor in a first space; driving the magnetically coupled inner rotor to rotate by the motor; using the first Hall sensor to receive the phase signal of the magnetically coupled inner rotor; placing a magnetically coupled outer rotor and a second Hall sensor in a second space; using the second Hall sensor to receive the phase signal of the magnetically coupled outer rotor; the second space is not in communication with the first space but only integrally connected; the magnetically coupled outer rotor rotates with the magnetically coupled inner rotor; several openings leading to the inner cavity are provided in the second space as sampling ports for the polymer to be measured; after injecting a polymer solution into the second space, the change in the rotational resistance in the fluid causes a phase difference to occur in the phase signals of the magnetically coupled inner and outer rotors; establishing a mapping mathematical model of viscosity and phase difference through a standard liquid calibration experiment for the phase difference signals of the coupled magnetic poles received by the first and second Hall sensors; substituting the phase difference signals of the coupled magnetic poles into the mapping mathematical model of viscosity and phase difference to determine the viscosity of the downhole polymer solution. Using the solution provided by the present disclosure can directly measure the viscosity of the polymer solution at the bottom of the well, effectively reducing the production cost in the actual oil production process.

Description

Technical Field

[0001] The present disclosure relates to the field of solution viscosity measurement, and more specifically, to a method and device for directly measuring the viscosity of polymers in an oilfield polymer injection well downhole. Background Art

[0002] With the decreasing oil reserves in high water cut oilfields year by year, ensuring the stable and increased production of oil production is crucial for meeting China's crude oil consumption. After decades of development in old oilfields, the water content in the formation is getting higher and higher. The compound flooding technology has also experienced many years of development, especially the polymer flooding technology is the most prominent. Existing numerical simulation technologies and on-site test technologies have shown that most blocks in high water cut oilfields are very conducive to the development of polymer flooding. In the development process of polymer flooding technology, in order to further master the dynamic and static data of polymer injection wells and improve the polymer flooding technology, it is necessary to carry out research on the downhole stratified viscosity measurement technology of polymer injection wells. However, existing measurement technologies can only measure the static viscosity on the ground. As shown in Chinese Patent CN202211083956.3, a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer and Chinese Patent CN202220557370.5, a detachable polymer online viscometer, neither can break through the limitation of leaving the ground and cannot directly measure the viscosity of the polymer solution at the bottom of the well. Summary of the Invention

[0003] To solve the technical problems in the background art, the present disclosure proposes a downhole polymer viscosity measurement method and a viscometer. In this technical solution, a magnetic coupling inner rotor is used to drive an outer rotor. Under the condition of a constant rotational speed, torque balance is achieved. As the dynamic viscosity of the polymer solution is different, the rotational resistance in the fluid changes, resulting in a change in the phase difference of the coupling magnetic poles. A Hall sensor is used to receive the phase difference of the coupling magnetic poles, and through a standard liquid calibration experiment, a mapping mathematical model between viscosity and phase difference is established. Then, through experiments, the relationship curve between the polymer solution concentration and viscosity at different temperatures is obtained, and finally, the viscosity model is corrected. The viscometer obtained by applying this solution can be directly placed into an oilfield polymer injection well, which can not only directly measure the viscosity of the polymer solution in the high-pressure environment in the polymer injection well, but also eliminate the mechanical rotary seal and avoid the risk of polymer leakage.

[0004] The present disclosure first provides a downhole polymer viscosity measurement method, including:

[0005] Placing a motor, an inner magnetic pole, an inner rotor, and a first Hall sensor in a first space, where the inner magnetic pole and the inner rotor form a magnetic coupling inner rotor; the first Hall sensor is fixed at the middle position corresponding to the inner magnetic pole; the motor drives the magnetic coupling inner rotor to rotate; the first Hall sensor is used to receive the phase signal of the magnetic coupling inner rotor;

[0006] Place the outer magnetic pole, the outer rotor, and the second Hall sensor in the second space. The outer magnetic pole and the outer rotor form a magnetically coupled outer rotor. The second Hall sensor is fixed at the middle position corresponding to the outer magnetic pole. The second Hall sensor is used to receive the phase signal of the magnetically coupled outer rotor.

[0007] The second space is not connected to the first space but only integrally connected. The magnetically coupled outer rotor can be coupled with the magnetically coupled inner rotor and rotate with the magnetically coupled inner rotor.

[0008] Several openings leading to the inner cavity are provided in the second space as sampling ports for the polymer to be measured.

[0009] Drive the outer rotor with the magnetically coupled inner rotor to achieve torque balance at a constant speed.

[0010] After injecting the polymer solution into the second space, the change in the rotational resistance in the fluid causes a phase difference to occur in the phase signals of the magnetically coupled inner and outer rotors.

[0011] Through a standard liquid calibration experiment, establish a mapping mathematical model between viscosity and phase difference for the phase difference signals of the coupled magnetic poles received by the first and second Hall sensors.

[0012] Substitute the phase difference signals of the coupled magnetic poles received by the first and second Hall sensors into the mapping mathematical model between viscosity and phase difference to determine the viscosity of the downhole polymer solution.

[0013] Further, the establishment of the mapping mathematical model between viscosity and phase difference through the standard liquid calibration experiment is carried out according to the following procedure:

[0014] Set the rotational speed of the motor driving the magnetically coupled inner rotor to be controlled at n (revolutions per minute). The first Hall sensor detects the position of the N pole of the magnetic pole of the magnetically coupled inner rotor, and the second Hall sensor detects the position of the N pole of the magnetic pole of the magnetically coupled outer rotor. When the inner and outer rotors are in phase, the phase difference detected by the Hall sensor is zero.

[0015] Let the polymer solution enter the second space. After torque balance, the phase difference between the outer magnetic pole and the inner magnetic pole changes. Convert the phase difference between the inner and outer magnetic poles into a time signal t1 (microseconds), and establish a corresponding mathematical relationship. That is, through the calibration of the standard liquid, convert the physical quantity of dynamic viscosity with a measurement range of (0 - 100, mPa·s) into a phase difference, and further convert it into a time signal with a range of (0 - T, s). Use m to perform an nth-degree polynomial curve fitting on the data points.

[0016] The polynomial curve fitting uses the least squares curve fitting viscosity model coefficients, that is,

[0017] m for the given points (x i , yi )(i = 1, 2, …, m), (x is time, y is viscosity), find an approximate curve, and require the function and the data y i , the error of the sum of squares is the smallest, as shown in Equation 1;

[0018]

[0019] Furthermore, select N standard solutions, use time as the abscissa and viscosity as the ordinate, and perform fitting on N pairs of data to obtain the nth-degree polynomial fitting formula for time-converted viscosity:

[0020]

[0021] where t is the time detected by the Hall sensor; A0 is the intercept at time zero, and its function is to adjust the zero migration of viscosity; A1…A n are the model weight coefficients;

[0022] Using the matrix solution method, for m samples, each sample has n-dimensional features, substitute all sample points into the model:

[0023]

[0024] Let t 0 = 1, the above equation can be represented by a matrix as:

[0025]

[0026] where, is an m×1 vector, representing the theoretical value of the model, A is an n×1 vector, X is an m×n-dimensional matrix, m represents the number of samples, and n represents the number of features of the samples. Thus, the objective loss function can be represented by a matrix as:

[0027]

[0028] where Y is the output vector of the sample, with a dimension of m×1

[0029] Substitute all N groups of data into the nth-degree polynomial fitting formula and fit it using the least squares formula; make converge to 10 -6 and then use it as the output result to obtain the value of n.

[0030] Furthermore, correct the mathematical model of the viscosity-phase difference mapping using the relationship curve between the polymer solution concentration and viscosity at different temperatures.

[0031] Furthermore, obtain the relationship curve between the polymer solution concentration and viscosity at different temperatures according to the following path:

[0032] (1) using polyacrylamide to prepare a mother solution, stirring the mixture with a stirrer at a ratio of 1000:1 of water to polyacrylamide to prepare polymer solutions of different concentrations, and controlling the concentration range to be between 50-1500 mg / L;

[0033] (2) Use a thermostat to control the temperature between 20-50°C and keep it constant. Select a suitable constant temperature water bath to ensure that the temperature control accuracy reaches ±0.1°C.

[0034] (3) Ensure that the maximum flow rate does not exceed 1.5 m / s, and use a viscometer to measure the viscosity of polymer solutions of different concentrations under constant temperature conditions;

[0035] (4) Record the temperature and viscosity of each measurement;

[0036] (5) changing the concentration and temperature of the polymer and repeating the above steps to obtain multiple sets of data on the relationship between the concentration and viscosity of the polymer solution at different temperatures;

[0037] (6) Process the collected data and plot the coordinate points of the viscosity relationship of polymer solutions at different temperatures at the same concentration.

[0038] Furthermore, when the relationship curve between the concentration and viscosity of the polymer solution at different temperatures is obtained, a secondary calibration correction is performed for the viscosity corresponding to different temperatures at the same concentration.

[0039] For the temperature correction coefficient, we first experimentally verified that the temperature range was between 20°C and 50°C. Data was recorded every time the temperature increased by 1°C from 20°C to 50°C, and all the data were fitted using Origin software. After fitting, the temperature formula was obtained:

[0040]

[0041] in The viscosity is at 20°C. When the temperature is higher than 20°C, the viscosity is corrected by adding the coefficient B multiplied by the temperature (z-20). When the temperature increases, the viscosity of the polymer decreases. Generally, the temperature coefficient is a negative number.

[0042] Another aspect of the present disclosure provides a downhole polymer viscometer for use in any of the aforementioned measurement methods, comprising an upper cylinder, a lower cylinder, and an intermediate separator, wherein:

[0043] The upper cylinder, the lower cylinder and the middle separator are connected into one body; the middle separator is used to separate the upper cylinder and the lower cylinder so that the two are not connected;

[0044] The upper cylinder is equipped with a control unit, a data communication module, a motor, and a magnetically coupled inner rotor;

[0045] A first Hall sensor and a second Hall sensor are arranged inside the intermediate separator; the first Hall sensor is used to detect the square wave state of the high and low levels of the magnetically coupled inner rotor and transmit the phase value of the magnetically coupled inner rotor back to the control unit; the second Hall sensor is used to detect the square wave state of the high and low levels of the magnetically coupled outer rotor and transmit the phase value of the magnetically coupled outer rotor back to the control unit;

[0046] The lower cylinder body is internally provided with a magnetically coupled outer rotor, and a plurality of openings leading to the inner cavity are formed in the cylinder wall as sampling ports for the polymer to be measured;

[0047] The magnetically coupled inner rotor is coaxially connected with the motor; the magnetically coupled outer rotor can rotate with the magnetically coupled inner rotor under the action of magnetic coupling;

[0048] Rotor coupling magnetic pole fixing grooves with the same central axis are respectively arranged on the upper and lower end faces of the intermediate separator for placing the magnetically coupled inner rotor and the magnetically coupled outer rotor respectively; the intermediate separator is made of a material with good magnetic conductivity;

[0049] The control unit is internally provided with a program, which can substitute the phase difference between the magnetically coupled inner and outer rotors received into the viscosity-phase difference mapping mathematical model for calculation to obtain the viscosity value.

[0050] Further, the data communication module communicates with the ground data processing device by means of Manchester code, and transmits the viscosity data measured in real time to the ground for display and recording.

[0051] Further, a temperature sensor and a pressure sensor are arranged inside the upper cylinder body, and the obtained temperature signal and pressure signal are sent to the control unit; under the control of the internal program of the control unit, the viscosity-phase difference mapping mathematical model is corrected according to the temperature parameter.

[0052] One or more of the above technical solutions adopted in the embodiments of this specification can achieve the following beneficial effects:

[0053] First, in the technical solution given in this disclosure, the mechanical seal bearing of the traditional rotational viscometer is replaced with magnetic coupling drive, and the magnetic pole of the inner rotor drives the magnetic pole of the outer rotor, so that the spaces where the inner rotor and the outer rotor are located are independent of each other. The space where the outer rotor is located can be used as a sampler for downhole solutions, avoiding the direct contact between the downhole solution and the measuring unit. The viscometer can be directly placed into the polymer injection well in the oil field, and can directly measure the viscosity of the polymer solution in the high-pressure environment in the injection well, and also saves the mechanical rotary seal, avoiding the risk of polymer leakage. The combination of the sensor unit, the STM32 control unit, the magnetically coupled inner and outer rotors, the Hall sensor and the data communication module provides a solution for high-precision and real-time polymer measurement

[0054] Secondly, during optimization implementation, a sensor unit is configured on the downhole rotary viscometer to sense the motion characteristics of the polymer; an STM32 control unit integrates a processor and a memory to receive, process, and store the data obtained by the sensor unit; a data communication module communicates with the ground data processing device using Manchester code to achieve real-time data transmission and remote monitoring.

[0055] Thirdly, the STM32 control unit runs a preset viscosity calculation algorithm, and based on the phase difference data measured by the magneto-coupled Hall sensor, calculates the phase difference of the polymer in real time. The data communication module communicates with the ground data processing device in the Manchester code manner, and transmits the viscosity data obtained by real-time measurement to the ground for display and recording. The communication between the downhole rotary viscometer and the upper computer adopts Manchester coding communication. Manchester coding is a linear code that represents data bits through changes in signal levels. Since it relies on level changes rather than absolute levels, Manchester coding has strong resistance to noise and interference, and is very suitable for the communication requirements of the complex downhole environment.

[0056] In addition, it is possible to supply power to the downhole rotary viscometer and achieve signal coding communication transmission through a single-core steel pipe cable. Further, during specific implementation, it is possible to adaptively adjust the delay time parameter according to the change in the capacitance effect of the cable due to the change in the depth of the cable going down the well. Different cables correspond to different capacitance delay parameters. When the communication is interfered with after the length of the cable going down the well changes, the capacitance effect of the cable changes at this time, and the parameters of the communication delay time are correspondingly adjusted. For this reason, the upper computer makes an adaptive adjustment, and there is no need to manually adjust the parameter setting anymore.

[0057] In addition, the present disclosure proposes a two-stage modeling method. The first stage is to calibrate the standard liquid to obtain a basic model. The second stage is to obtain the relationship curve between the concentration and viscosity of the polymer solution at different temperatures through experiments, and finally correct the viscosity model, thereby improving the measurement accuracy of the viscosity of the downhole polymer fluid at a certain flow rate.

[0058] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and do not limit the present disclosure.

[0059] According to the following detailed description of the exemplary embodiments with reference to the accompanying drawings, other features and aspects of the present disclosure will become clear. Description of the Drawings

[0060] The accompanying drawings here are incorporated into the specification and constitute a part of this specification. These drawings show embodiments that conform to the present disclosure and are used together with the specification to explain the technical solutions of the present disclosure.

[0061] Figure 1Schematic diagram of the component units of the downhole polymer viscometer described in the present disclosure.

[0062] Figure 2 Overall system structure diagram of the downhole polymer viscometer described in the present disclosure.

[0063] Figure 3 Schematic diagram of the mechanical structure of the probe of the downhole polymer viscometer described in the present disclosure.

[0064] Figure 4 Curve diagram of the relationship between the concentration and viscosity of the polymer solution obtained in a specific implementation given in the present disclosure.

[0065] In the figure: 1 - temperature sensor; 2 - pressure sensor; 3 - sealing groove; 4 - sampling hole for pressure sensor; 5 - motor; 6 - inner rotor; 7 - inner coupling magnetic pole; 8 - first Hall sensor; 9 - second Hall sensor; 10 - outer coupling magnetic pole; 11 - sampling hole; 12 - outer rotor; 13 - sampler. Detailed implementation manners

[0066] Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the drawings denote elements having the same or similar functions. Although various aspects of the embodiments are shown in the drawings, the drawings do not have to be drawn to scale unless otherwise specified.

[0067] In addition, for a better illustration of the present disclosure, numerous specific details are given in the following detailed implementation manners. Those skilled in the art should understand that the present disclosure can be implemented without some of these specific details. In some instances, methods and means well known to those skilled in the art are not described in detail so as to highlight the gist of the present disclosure.

[0068] First, the present disclosure provides a method for measuring the viscosity of downhole polymers, including:

[0069] Placing the motor, the magnetically coupled inner rotor, and the first Hall sensor in the first space; the motor drives the magnetically coupled inner rotor to rotate; the first Hall sensor is used to receive the phase signal of the magnetically coupled inner rotor;

[0070] Placing the magnetically coupled outer rotor and the second Hall sensor in the second space; the second Hall sensor is used to receive the phase signal of the magnetically coupled outer rotor;

[0071] The second space is not connected to the first space and is only integrally connected; the magnetically coupled outer rotor can be coupled with the magnetically coupled inner rotor and rotate with the magnetically coupled inner rotor;

[0072] Several openings leading to the inner cavity are provided in the second space as sampling ports for the polymer to be measured;

[0073] Drive the outer rotor with the magnetic coupling inner rotor to achieve torque balance under the condition of constant rotational speed;

[0074] After injecting the polymer solution into the second space, the rotational resistance in the fluid changes, resulting in a phase difference in the phase signals of the magnetic coupling inner and outer rotors;

[0075] For the phase difference signals of the coupled magnetic poles received by the first and second Hall sensors, establish a mapping mathematical model of viscosity and phase difference through a standard liquid calibration experiment;

[0076] Substitute the phase difference signals of the coupled magnetic poles received by the first and second Hall sensors into the mapping mathematical model of viscosity and phase difference to determine the viscosity of the downhole polymer solution.

[0077] The conceptual principle of this method is as follows:

[0078] Magnetic coupling realizes the driving of the outer rotor by the inner rotor of the motor to transfer kinetic energy. The outer rotor contacts the polymer solution and rotates at a constant speed. The phase difference signal is fed back through the Hall sensor, converted into a time difference, and used for viscosity calibration.

[0079] When the voltage is stable, under the action of magnetic coupling, the inner rotor drives the outer rotor to rotate at the same speed to transfer kinetic energy. Since there is liquid frictional resistance when the outer rotor contacts the polymer solution,

[0080]

[0081] In the formula, M is the shear force received by the rotor; h is the height of the rotor; ω is the angular velocity; R is the radius of the rotor.

[0082] At this time, a phase difference θ is generated between the outer rotor and the inner rotor. Install two Hall sensors at the connection of the inner rotor and the outer rotor. One detects the square wave state of the high and low levels of the inner rotor, and the other detects the square wave state of the high and low levels of the outer rotor. The time difference reflected by the two square waves can be indirectly converted into a viscosity formula.

[0083] The calculation formula is:

[0084] θ = ωt

[0085] In the formula, θ - phase difference; ω - angular velocity; t - time

[0086] Among them:

[0087]

[0088] In the formula, n - motor speed

[0089] Since the voltage is stable, the set values of the rotational speeds of the inner rotor and the outer rotor remain the same and unchanged, so the angular velocity ω is fixed. Therefore, when the phase difference and the angular velocity are known, the time t can be recorded. After the time t is converted into viscosity through a function, the viscosity value can be read.

[0090] Applying this method, the motor, the magnetic coupling rotor, the magnetic poles and the Hall sensors can measure the viscosity in the high-pressure environment of the polymer injection wellbore, eliminating the mechanical rotating seal and avoiding the risk of leakage failure. Using the magnetic coupling inner rotor to drive the outer rotor, under the condition of constant rotational speed, torque balance is achieved. As the dynamic viscosity of the polymer solution varies, the rotational resistance in the fluid changes, resulting in a change in the phase difference of the coupling magnetic poles. The Hall sensors receive the phase difference of the coupling magnetic poles, and through the calibration experiment with standard liquid, a mapping mathematical model between viscosity and phase difference is established. Then, through experiments, the relationship curve between the concentration and viscosity of the polymer solution at different temperatures is obtained. Finally, the viscosity model is corrected to improve the accuracy of measuring the viscosity of the downhole polymer fluid at a certain flow rate.

[0091] The aforementioned mapping mathematical model between viscosity and phase difference is established through the calibration experiment with standard liquid according to the following procedure:

[0092] The rotational speed of the motor driving the inner rotor is controlled at n (revolutions per minute). Hall sensor 1 detects the position of the N pole of the inner rotor magnetic pole, and Hall sensor 2 detects the position of the N pole of the outer rotor magnetic pole. When the inner and outer rotors are in phase, the phase difference detected by Hall sensors 1 and 2 is zero. When the polymer solution enters the sampler, the outer rotor is subject to the viscosity resistance of the polymer. After torque balance, the phase difference between the outer magnetic pole and the inner magnetic pole changes. The phase difference between the inner and outer magnetic poles is converted into a time signal t1 (microseconds), and a corresponding mathematical relationship is established. Therefore, through the calibration of the standard liquid, the physical quantity of dynamic viscosity in the measurement range (0 - 100, mPa·s) is converted into a phase difference, and further into a time signal in the range (0 - T, s). Then, an nth-degree polynomial curve fitting can be performed on m data points.

[0093] The least squares curve fitting method is used for the viscosity model coefficients. Curve fitting is a commonly used smoothing method. Its prominent feature is that it can reduce the prior information of the model or measurement, and reduce the sensitivity problem of the initial value. However, for strongly maneuvering targets, when the order is selected to be relatively low, the fitting accuracy and effect are not ideal. When the order is selected to be relatively large, the fitting accuracy and effect are relatively ideal, but it is easy to cause complex solution of the normal equation, poor robustness of the fitting curve, and greater influence of random fluctuations.

[0094] The curve fitting method is to find an approximate curve for m given points (x i , y i )(i = 1, 2,..., m), where x is the time and y is the viscosity), that is, to find a best function according to a certain determined function class ​to fit the given data (t i , y i ). The least squares fitting curve requires the function and the data y i , with the error of the sum of squares (see the following formula) being minimized.

[0095]

[0096] We selected 5 standard solutions. The first standard solution is numbered GBW(E)130201, with a kinematic viscosity of 4.087 mPa·s, and the calibration time of this viscometer is 443 μs; the second standard solution is numbered GBW(E)130202, with a kinematic viscosity of 8.459 mPa·s, and the calibration time of this viscometer is 497 μs; the third standard solution is numbered GBW(E)130203, with a kinematic viscosity of 16.83 mPa·s, and the calibration time of this viscometer is 573 μs; the fourth standard solution is numbered GBW(E)130204, with a kinematic viscosity of 43.17 mPa·s, and the calibration time of this viscometer is 757 μs; the fifth standard solution is numbered GBW(E)130205, with a kinematic viscosity of 105.82 mPa·s, and the calibration time of this viscometer is 967 μs. Taking time as the abscissa and viscosity as the ordinate, the nth-degree polynomial fitting formula for converting time to viscosity is obtained by fitting these 5 pairs of data:

[0097]

[0098] where t is the time detected by the Hall sensor;

[0099] where A0 is the intercept at time zero, and its function is to adjust the zero migration of viscosity;

[0100] where A1…A n are the model weight coefficients calculated by the algorithm;

[0101] Using the matrix solution method, assuming there are m samples now, and each sample has n-dimensional features, substituting all sample points into the model:

[0102]

[0103] For convenient matrix representation, let t 0 = 1, and the above equation can be represented by a matrix as:

[0104]

[0105] where, is a vector of m×1, representing the theoretical value of the model, A is a vector of n×1, X is a matrix of m×n dimensions, m represents the number of samples, and n represents the number of features of the samples. Thus, the objective loss function is represented by a matrix as follows:

[0106]

[0107] where Y is the output vector of the sample, with a dimension of m×1

[0108] Substitute all five groups of data into the fitting formula:

[0109] 4.087 = A0 + A1 * 443 1 + A2 * 443 2 + A3 * 443 3 +…+ A n * 443 n

[0110] 8.459 = A0 + A1 * 497 1 + A2 * 497 2 + A3 * 497 3 +...+ A n * 497 n

[0111] 16.83 = A0 + A1 * 573 1 + A2 * 573 2 + A3 * 573 3 +...+ A n * 573 n

[0112] 43.17 = A0 + A1 * 757 1 + A2 * 757 2 + A3 * 757 3 +...+ A n * 757 n

[0113] 105.82 = A0 + A1 * 967 1 + A2 * 967 2 + A3 * 967 3 +...+ A n * 967 n

[0114] After fitting with the least squares formula, the result is as Figure 4 shown below.

[0115] After the value converges to 10 -6 the resulting output is:

[0116]

[0117] The coefficients above the third power are 0, so the conclusion is drawn that n = 3.

[0118] Furthermore, the mapping mathematical model of the viscosity and the phase difference is corrected by using the relationship curve between the concentration and the viscosity of the polymer solution at different temperatures.

[0119] The specific process of obtaining the relationship curve between the concentration and the viscosity of the polymer solution at different temperatures is as follows:

[0120] (1) Prepare the mother liquor with polyacrylamide, and use a stirrer to fully stir under the preparation condition that the ratio of water to polyacrylamide is 1000:1 to prepare polymer solutions with different concentrations, and control the concentration range to be between 50 - 1500 mg / L; (2) Use an incubator to control the temperature range between 20 - 50 °C and keep it constant, select a suitable constant temperature water bath device to ensure that the temperature control accuracy reaches ±0.1 °C; (3) Ensure that the maximum flow rate is controlled not to exceed 1.5 m / s, and use a viscometer to measure the viscosities of polymer solutions with different concentrations at a constant temperature; (5) Use a data acquisition system to record the temperature and viscosity measured each time; (6) By changing the concentration and temperature of the polymer, repeat the above steps for experiments to obtain multiple sets of data on the relationship between the concentration and the viscosity of the polymer solution at different temperatures.

[0121] Data analysis: Process the collected data, plot the coordinate points of the viscosity relationship of the polymer solution at different temperatures under the same concentration, and perform a secondary calibration correction on the corresponding viscosities at different temperatures under the same concentration.

[0122] For the temperature correction coefficient, first, experimentally verify that the temperature range is between 20 °C and 50 °C, record the data every time the temperature is increased by 1 °C from 20 °C to 50 °C, and use Origin software to fit all the data. Its fitting effect is: When measuring the viscosity of the polymer at a certain temperature in the future, the system will directly give the specific viscosity through the algorithm. After fitting, the temperature formula is obtained:

[0123]

[0124] T(z) = -40.924 + 10.523t - 0.175t 2 + 0.00098t 3 - 0.49*(z - 20)

[0125] where is the viscosity at 20 °C. When the temperature is higher than 20 °C, the viscosity is corrected by adding the coefficient B multiplied by the temperature (z - 20). When the temperature increases, the polymer viscosity decreases, so the coefficient of the general temperature is negative.

[0126] The following table shows the comparison results of the data obtained by using this method and the data obtained by a Brookfield viscometer.

[0127]

[0128] This data is the result of ground measurements by two different viscometers. When the concentration value is not high, the Brookfield viscometer can maintain stable data measurement. When the concentration increases, the measurement value of the Brookfield viscometer is not stable. At this time, the stable measurement of the downhole rotary viscometer demonstrates its advantages. Moreover, the Brookfield viscometer is only suitable for ground measurements and is not sufficient to withstand the pressure to enter the well.

[0129] To implement the foregoing method, a downhole polymer viscometer was constructed, which includes an upper cylinder, a lower cylinder, and an intermediate separator. The schematic diagram of its constituent units is as Figure 1 shown, including: a lower single-chip microcomputer, a power management module, a magnetic coupling rotor, a Hall sensor, a temperature and pressure sensor, and a sampler. The power management module adopts an efficient and stable power management system to ensure continuous power supply in high-temperature and high-pressure environments. The lower single-chip microcomputer is responsible for data acquisition, processing, transmission, and storage. The temperature and pressure sensors monitor the downhole environment in real time and provide accurate downhole temperature data.

[0130] The upper cylinder, the lower cylinder, and the intermediate separator are connected into one body; the intermediate separator is used to separate the upper cylinder and the lower cylinder so that they are not connected to each other.

[0131] A control unit, a data communication module, a motor 5, a magnetic coupling inner rotor composed of an inner rotor 6 and an inner coupling magnetic pole 7, and a first Hall sensor 8 are placed in the upper cylinder;

[0132] The first Hall sensor 8 and the second Hall sensor 9 are arranged in the intermediate separator. The first Hall sensor is used to detect the square wave state of the high and low levels of the magnetic coupling inner rotor and transmit the phase value of the magnetic coupling inner rotor back to the control unit; the second Hall sensor is used to detect the square wave state of the high and low levels of the magnetic coupling outer rotor and transmit the phase value of the magnetic coupling outer rotor back to the control unit.

[0133] A magnetic coupling outer rotor composed of an outer rotor 12 and an outer coupling magnetic pole 10 is arranged in the lower cylinder. The lower cylinder is a sampler 13. After being lowered into the well, the polymer solution flows into it.

[0134] The magnetic coupling inner rotor is coaxially connected to the motor; the magnetic coupling outer rotor can rotate with the magnetic coupling inner rotor under the action of magnetic coupling.

[0135] On the upper and lower end faces of the intermediate separator, rotor coupling magnetic pole fixing grooves with the same central axis are respectively arranged for placing the magnetic coupling inner rotor and the magnetic coupling outer rotor; the intermediate separator is made of a material with good magnetic conductivity.

[0136] The control unit has a built-in program that can substitute the phase difference between the magnetic coupling inner and outer rotors received into the viscosity-phase difference mapping mathematical model for calculation to obtain the viscosity value.

[0137] The data communication module communicates with the ground data processing equipment through a single-core steel pipe cable, communicates with the ground data processing equipment in the Manchester code mode, and transmits the viscosity data measured in real time to the ground for display and recording. Through the built-in program, according to the change of the cable downhole depth, the cable capacitance effect changes, and the delay time parameter can be adaptively adjusted to adaptively adjust the communication parameters of the long-distance single-core steel pipe cable. The ground upper computer maintains a data connection with the downhole viscometer through the Manchester coding communication technology to ensure efficient and reliable data transmission. The upper computer is equipped with data processing and display functions, can receive and analyze the data sent by the downhole viscometer in real time, and provide detailed fluid viscosity, temperature and pressure information for the operator. These data are clearly displayed through the human-machine interface for easy monitoring and decision-making.

[0138] Manchester coding is a linear code that represents data bits through changes in signal levels. Since it depends on level changes rather than absolute levels, Manchester coding has strong resistance to noise and interference and is very suitable for the communication requirements of the complex downhole environment.

[0139] The steps for upward communication of downhole signals are as follows:

[0140] (1) The integrated single-chip microcomputer based on STM32 built in the rotary viscometer is responsible for collecting the fluid pressure stabilization and viscosity data fed back by the sensor and the motor part and performing preliminary processing.

[0141] (2) Manchester code the collected data and convert it into a signal format suitable for transmission.

[0142] (3) Send the coded data to the ground through the downhole communication cable.

[0143] The steps for the ground part to receive and display the viscosity data are as follows:

[0144] (1) Receive: Receive the Manchester coded signal transmitted from the downhole.

[0145] (2) Decode: Decode the Manchester coded signal into the original viscosity data.

[0146] (3) Processing and display: Transmit the decoded data to the host computer for further analysis and processing, and finally display the downhole fluid viscosity on the monitoring interface.

[0147] A temperature sensor 1 and a pressure sensor 2 are arranged in the upper cylinder body, and the obtained temperature signal and pressure signal are sent to the control unit; under the control of the built-in program, the control unit corrects the viscosity-phase difference mapping mathematical model according to the temperature parameter. The temperature sensor 1 and the pressure sensor 2 are arranged on the downhole rotational viscometer. The pressure parameter of the polymer solution is obtained through the pressure sensor sampling hole 4, and the temperature sensor is used to collect the polymer temperature parameter of the downhole environment to dynamically correct the viscosity measurement. The control unit adopts an STM32 control unit, which integrates a processor and a memory, and is used to receive, process, and store the data obtained by the sensor unit.

[0148] Preferably, an O-ring is sleeved in the sealing groove 3 to achieve high-pressure resistance and be able to enter the downhole target layer for direct measurement.

[0149] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Those of ordinary skill in the art can understand that various modifications can be made in form and detail without departing from the spirit and scope of the present invention defined by the appended claims.

Claims

1. A downhole polymer viscosity measurement method, comprising: Placing a motor, an inner magnetic pole, an inner rotor, and a first Hall sensor in a first space, where the inner magnetic pole and the inner rotor form a magnetically coupled inner rotor; The first Hall sensor is fixed at the middle position corresponding to the inner magnetic pole; the motor drives the magnetically coupled inner rotor to rotate; the first Hall sensor is used to receive the phase signal of the magnetically coupled inner rotor; Placing an outer magnetic pole, an outer rotor, and a second Hall sensor in a second space, where the outer magnetic pole and the outer rotor form a magnetically coupled outer rotor; the second Hall sensor is fixed at the middle position corresponding to the outer magnetic pole; the second Hall sensor is used to receive the phase signal of the magnetically coupled outer rotor; The second space is not connected to the first space and is only integrally connected; The magnetically coupled outer rotor can be coupled with the magnetically coupled inner rotor and rotate with the magnetically coupled inner rotor; Several openings leading to the inner cavity are provided in the second space as sampling ports for the polymer to be measured; Using the magnetically coupled inner rotor to drive the outer rotor to achieve torque balance under the condition of constant rotational speed; After injecting a polymer solution into the second space, the change in the rotational resistance in the fluid causes a phase difference to occur in the phase signals of the magnetically coupled inner and outer rotors; By performing a calibration experiment with a standard liquid on the phase difference signals of the coupled magnetic poles received by the first and second Hall sensors, a mapping mathematical model between viscosity and phase difference is established; Substituting the phase difference signals of the coupled magnetic poles received by the first and second Hall sensors into the mapping mathematical model between viscosity and phase difference to determine the viscosity of the downhole polymer solution; It is characterized in that: The process of establishing the mapping mathematical model between viscosity and phase difference through the standard liquid calibration experiment is as follows: Set the rotational speed of the motor driving the magnetically coupled inner rotor to be controlled at n revolutions per minute. The first Hall sensor detects the position of the N pole of the magnetic pole of the magnetically coupled inner rotor, and the second Hall sensor detects the position of the N pole of the magnetic pole of the magnetically coupled outer rotor. When the inner and outer rotors are in phase, the phase difference detected by the Hall sensor is zero; Let the polymer solution enter the second space. After torque balance, a phase difference change occurs between the outer magnetic pole and the inner magnetic pole. The phase difference between the inner and outer magnetic poles is converted into a time signal of t1 microseconds, and a corresponding mathematical relationship is established. That is, through the calibration of the standard liquid, the physical quantity of dynamic viscosity with a measurement range of 0 - 100 mPa·s is converted into a phase difference and further into a time signal with a range of 0 - T. s， Use m to perform n - order polynomial curve fitting on the data points; The polynomial curve fitting uses the least squares curve fitting viscosity model coefficients, that is For the given m points (x i , y i )(i = 1, 2,..., m), where x is time and y is viscosity, find an approximate curve such that the function and the data y i , and the sum of the squares of the errors is minimized as in Equation 1; 2. A downhole polymer viscosity measurement method according to claim 1, characterized in that: Select N standard liquids, use time as the abscissa and viscosity as the ordinate, and perform fitting on N pairs of data to obtain an nth-degree polynomial fitting formula for converting time to viscosity: where t is the time detected by the Hall sensor; A0 is the intercept at time zero, which functions to adjust the zero migration of viscosity; A1…A n are the model weight coefficients; Using the matrix solution method, for m samples, each sample has n-dimensional features, and substitute all sample points into the model: Let t 0 = 1, the above equation can be represented in matrix form as: Among them, is an m×1 vector representing the theoretical value of the model, A is an n×1 vector, X is an m×n-dimensional matrix, m represents the number of samples, and n represents the number of features of the samples. Thus, the objective loss function is represented by a matrix as follows: Where Y is the output vector of the sample, with a dimension of m×1 Substitute all N groups of data into the n - degree polynomial fitting formula and fit it using the least - squares formula; when the value of converges to 10 -6 use it as the output result to obtain the value of n.

3. A downhole polymer viscosity measurement method according to claim 2, characterized in that: The mapping mathematical model between viscosity and phase difference is corrected by using the relationship curve between the concentration and viscosity of the polymer solution at different temperatures.

4. A downhole polymer viscosity measurement method according to claim 3, characterized in that: The process of obtaining the relationship curve between the concentration and viscosity of the polymer solution at different temperatures is as follows: (1) Prepare a mother liquor using polyacrylamide, and use a stirrer to fully stir under the preparation condition of a ratio of water to polyacrylamide of 1000:1 to prepare polymer solutions with different concentrations, and control the concentration range to be between 50 - 1500 mg / L; (2) Use an incubator to control the temperature range between 20 - 50 °C and keep it constant. Select a suitable constant temperature water bath device to ensure that the temperature control accuracy reaches ±0.1 °C; (3) Ensure that the maximum flow rate is controlled not to exceed 1.5 m / s. Under the condition of constant temperature, use a viscometer to measure the viscosities of polymer solutions with different concentrations; (4) Record the temperature and viscosity of each measurement; (5) Change the concentration and temperature of the polymer and repeat the above steps to obtain multiple sets of data on the relationship between the concentration and viscosity of the polymer solution at different temperatures; (6) Process the collected data and plot the coordinate points of the viscosity relationship of polymer solutions at different temperatures under the same concentration.

5. The downhole polymer viscosity measurement method according to claim 4, characterized in that: When obtaining the relationship curve between the concentration and viscosity of the polymer solution at different temperatures, perform secondary calibration and correction on the viscosities corresponding to different temperatures under the same concentration; For the temperature correction coefficient, first experimentally verify that the temperature range is between 20 °C and 50 °C. Record the data once for every 1 °C increase from 20 °C to 50 °C, and fit all the data using Origin software; after fitting, obtain the temperature formula: wherein is the viscosity at 20°C. When the temperature is higher than 20°C, the viscosity is corrected by adding the coefficient B multiplied by the temperature (z - 20). When the temperature increases, the polymer viscosity decreases, and the coefficient of temperature is negative.

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