RU2791271C1 - Method for indication of local corrosion level in pipelines of oil gathering systems and device for its implementation - Google Patents

Abstract

FIELD: oil pipelines.

SUBSTANCE: invention relates to the field of ensuring trouble-free operation of field oil pipelines and can be used to evaluate the parameters of corrosion processes in them. The effect is achieved by the fact that a multichannel corrosion sensor is proposed that implements the electrical resistance method, including a reference current source, differential amplifiers, a processor capable of transmitting data to a computer network, a multichannel analog-to-digital converter, low-pass filters, switch blocks, a source bias voltage, characterized in that the reference part of the measuring probe is either connected to the free inputs of the switch block of each measuring channel, or is distributed so that each share of the reference part is located on the corresponding part of the surface of the measuring probe, and is connected to the free inputs of the switch block of the corresponding measuring channel, while the sensitive part of the measuring probe is immersed in a layer of bottom mineralized water.

EFFECT: providing operational multi-channel monitoring of the corrosion rate in the bottom mineralized water of pipelines of oil gathering systems.

6 cl, 7 dwg

Description

The present invention relates to the field of ensuring trouble-free operation of field oil pipelines and can be used to assess the parameters of corrosion processes in them.

According to literary sources (Markin A.N., Nizamov R.E. CO2-corrosion of oilfield equipment. - M .: JSC "VNIIOENG". - 2003. - 188 p.; Markin A.N., Nizamov R.E., Sukhoverkhoye S.V. Petroleum chemistry: A practical guide. - Vladivostok: Dalnauka, 2011. - 288 p.), internal corrosion of oilfield equipment, including pipelines of oil gathering systems (TSSN) and downhole equipment (VSO) of production wells in the fields of Western Siberia, proceeds by the carbon dioxide mechanism. The main type of corrosion damage during carbon dioxide corrosion is local corrosion in the form of ulcers and fistulas (Markin A.N. On the prediction of carbon dioxide corrosion of steel under the conditions of salt precipitation. // Protection of metals. - 1995. - T. 31. - No. 4. - 394-400.; Markin A.N., Sukhoverkhov S.V., Brikov A.V. Local carbon dioxide corrosion of pipelines of oil gathering systems of Western Siberia fields. // Oilfield business. 2017. No. 1. P. 46-48 .). It is local corrosion of the inner surface of TSSN that leads to violations of their tightness, to premature underground workovers and the need to replace equipment that has failed due to corrosion, and temporary losses in oil production. Therefore, the estimation of the local corrosion rate is an important practical task. It should also be noted that in any oil and gas field system where there is a mineralized water phase, and the partial pressure of CO ₂ exceeds 0.001 ... 0.005 MPa, serious corrosion damage is possible in a short time. In such a system, a set of measures should be implemented to control and economically justify prevent corrosion. Without the implementation of protective measures, the rate of local corrosion in any such system will exceed the value of 0.1 mm / year (taken as the maximum allowable threshold) by tens and hundreds of times, which has been proven by more than 50 years of studying carbon dioxide corrosion (Markin A.N., Nizamov R.E., Sukhoverkhoe S.V. Oilfield Chemistry: A Practical Guide. - Vladivostok: Dalnauka, 2011. - 288 p.).

In view of the foregoing, the main task of monitoring carbon dioxide corrosion here is not to measure absolutely exactly the values of local corrosion in any object of observation, but to monitor the technical effectiveness of the applied anticorrosion measures.

A known method for assessing the tendency of a metal to local corrosion (Markin A.N., Nizamov R.E. CO2-corrosion of oilfield equipment. M .: OAO VNIIOENG. 2003. - 188 p.) by obtaining the form of the distribution function of specific mass loss over metal surface. It is believed that it is sufficient to place a metal sample in a corrosive environment and, after an appropriate exposure, measure the corrosion rates in each section of it. Next, build a histogram "corrosion rate - relative frequency of occurrence of corrosion rate". To control TSSN corrosion, it is proposed to use gravimetric sensors in the form of a cassette of 10 cylindrical carbon steel corrosion witness samples. There is a reliable electrical contact between the samples in the cassette, and the cassette is in contact with the lower generatrix of the pipeline. When water is separated into a separate phase in the pipeline, and the cassette is completely in the water sublayer, then all samples in the cassette have the same stationary electrode potential. Therefore, with certain assumptions, such a cassette assembly from an electrochemical point of view can be considered one "piece" of metal. Assuming that the cassette assembly models a "piece" of metal, and knowing the corrosion rate for each sample, it is possible to construct a histogram of the distribution of corrosion rates.

However, the statistics for one cassette of 10 samples will not be representative. To obtain statistics on a large data array, it is necessary either to install several cassettes simultaneously in a small section of the pipeline, where corrosion conditions are close, or to expose the cassettes several times at the same point in the pipeline.

Disadvantages of the method: a large inertia and the complexity of obtaining evaluation results.

Of the known, the closest in technical essence, i.e. the prototype is a method for indicating the level of local corrosion in pipelines of an oil gathering system (Markin A.N., Markin I.A. Calculation of the maximum rate of local corrosion of pipelines of oil gathering systems according to weight measurements obtained using corrosion control samples. // Oilfield business 2020. No. 12. S. 70-73.), including the placement of multi-channel corrosion sensors (MDK - which can be understood as a cassette of corrosion witness samples) with a sensor part that allows profiling, on the pipelines of the system, which provide information on the corrosion activity of the transported environment in its entire range, the implementation of the required exposure for each MDS, profiling the sensor part of the measuring channels of each MDS after exposure, processing profiling data containing an estimate of the maximum depth of local corrosion damage and, on its basis, the maximum local corrosion rate, processing the data of the measurement results of each M DC with an estimate of the standard deviation for all channels, the formation of an array of data from the obtained estimates and the results of profiling to calculate the coefficients of the regression line using the least squares method, the subsequent assessment, by means of the MDC, of the level of local corrosion, taking into account the calculated coefficients.

The disadvantage of the prototype method is the inertia in obtaining the evaluation result.

A device for controlling uneven corrosion of the inner surface of pipelines is known from the patent literature (RF patent No. 2715474, IPC G01N 17/02, G01N 27/20, publ. 28.02.2020, Bull. No. 7). The device contains a primary measuring transducer, a reference current source, a switch block, an analog-to-digital converter and a processor, wherein the reference current source, the switch block, an analog-to-digital converter and the processor form an electronic unit of the device. The primary measuring transducer is a metal tape made of the same material as the pipeline, located along the inner generatrix of the pipeline, and having taps evenly spaced over the surface, which are in electrical contact with the tape, but isolated from the corrosive environment, while at least , one of the sections of the tape - a reference section located between adjacent taps, is protected from the effects of a corrosive environment by an anti-corrosion coating, but has temperature contact with it, the primary measuring transducer is electrically isolated from the pipeline, while its outermost taps are connected to a reference current source, outputs the switch block is connected through an analog-to-digital converter to the processor input, which is configured to transfer data to a computer network, the processor output is connected to the control input of the switch block.

The disadvantage of the device is the high complexity in the implementation of profiling of the primary transducer in pipelines of large diameter.

The closest in terms of features to the claimed device, i.e. The prototype is a multichannel corrosion and erosion sensor that implements the electrical resistance method (RF patent No. 2744351 IPC G01N 17/02, G01N 27/20, publ. 03/05/2021, Bull. No. 7), including a reference current source, differential amplifiers , a processor capable of transmitting data to a computer network, a multichannel analog-to-digital converter, low-pass filters, switch blocks, a bias voltage source, wherein the output of the reference current source and the output of the bias voltage source are connected to the inputs of the first switch block, the outputs of which are connected to measuring probe inputs, and the outputs of each section of the sensitive part of the measuring probe are connected to an individual measuring channel formed by a series-connected switch block, a low-pass filter and a differential amplifier, while the outputs of each measuring channel are connected to the analog inputs of a multichannel analog-to-digital converter a measuring probe, the digital output of which is connected to the processor, and the control outputs of the processor are connected to the control circuits of the switch blocks, the measuring probe containing the reference part protected from the influence of the controlled environment, and the multi-section sensitive part, made of the same material as the in-line process equipment, moreover the reference part of the measuring probe is either connected to the free inputs of the switch block of each measuring channel, or is distributed so that each share of the reference part is located on the corresponding part of the measuring probe surface, and is connected to the free inputs of the switch block of the corresponding measuring channel.

The disadvantage of the prototype device is the omission of information about the corrosion rate, which is due to the design of the measuring probe, namely, the different inclination of its sensor areas relative to the controlled flow of bottom mineralized water, as well as the incomplete immersion of the measuring probe in the bottom layer of the environment.

The purpose of the proposed invention-method is the operational monitoring of the level of local corrosion in pipelines of oil gathering systems.

This goal is achieved by the fact that in the method of indicating the level of local corrosion in the TSSN, including the placement of the MDK with a sensor part that allows profiling, on the pipelines of the system, which provide information on the corrosive activity of the transported medium in its entire range, the implementation of the required exposure for each MDK, profilography of the sensor part of the measuring channels of each MDS after exposure, processing of profiling data containing an estimate of the maximum depth of local corrosion damage and, on its basis, the maximum local corrosion rate, processing of measurement data by each MDS with an estimate of the root mean square deviation of the corrosion rate for all channels, formation array of data from the estimates obtained and the results of profiling to calculate the coefficients of the regression line using the least squares method, the subsequent assessment, by means of MDC, of the level of local corrosion, taking into account the calculated coefficients According to the invention, as the MDC, the MDC is used, which implements the method of electrical resistance, while the processing and evaluation of the measurement results, as well as the calculation of the coefficients of the regression line, is carried out in an automated mode by means of a computer.

For the purpose of profiling, the MDM can be combined with flaw detectors: an ultrasonic flaw detector or a flaw detector that implements the Field Signature Method (FSM™).

The claimed method is based on the proposed device, the essence of which is disclosed below.

The purpose of the proposed invention-device is operational multi-channel monitoring of the corrosion rate in the bottom mineralized water of pipelines of oil gathering systems.

This goal is achieved by the fact that in a multichannel corrosion sensor that implements the electrical resistance method, including a reference current source, differential amplifiers, a processor capable of transmitting data to a computer network, a multichannel analog-to-digital converter, low-pass filters, switch blocks, bias voltage source, moreover, the output of the reference current source and the output of the bias voltage source are connected to the inputs of the first switch block, the outputs of which are connected to the inputs of the measuring probe, and the outputs of each section of the sensitive part of the measuring probe are connected to an individual measuring channel formed by the series-connected switch block, filter low frequencies and a differential amplifier, while the outputs of each measuring channel are connected to the analog inputs of a multichannel analog-to-digital converter, the digital output of which is connected to the processor, and the control the outputs of the processor are connected to the control circuits of the switch blocks, the measuring probe containing the reference part protected from the influence of the controlled environment, and the multi-section sensitive part, made of the same material as the inline process equipment, and the reference part of the measuring probe is either connected to the free inputs of the unit switches of each measuring channel, or is made distributed so that each share of the reference part is located on the corresponding part of the surface of the measuring probe, and is connected to the free inputs of the switch block of the corresponding measuring channel, according to the invention, the sensitive part of the measuring probe is immersed in a layer of bottom mineralized water.

In this case, all sensitive sections of the measuring probe are located in the same plane and are oriented parallel to the flow of the controlled medium.

The measuring probe can be made in the form of a metal tape located along the inner generatrix of the pipeline.

The claimed invention-device is illustrated by drawings.

In FIG. Figure 1 shows a block diagram of a multi-channel corrosion sensor that implements the electrical resistance method with a probe containing a multi-section sensitive part and a common reference part.

In FIG. 2a shows an example of the design of a measuring probe with a common support part.

In FIG. 2b shows the position of the probe when monitoring the transported medium.

In FIG. 3 shows an example of the design of a measuring probe with a common support part, made in the form of a metal tape located along the inner generatrix of the pipeline.

In FIG. Figure 4 shows a block diagram of a multi-channel corrosion sensor that implements the electrical resistance method with a probe containing a multi-section sensitive part with a distributed reference part.

In FIG. 5 shows an example of the design of a measuring probe with a distributed support part.

In FIG. 6 shows an example of the design of a measuring probe with a distributed support part, made in the form of a metal tape, located along the inner generatrix of the pipeline.

In FIG. 7 and FIG. Figure 8 shows variants of a multichannel corrosion sensor structurally combined with flaw detectors.

The device contains (Fig. 1) a reference current source (IOT) 1, a bias voltage source (INS) 2, a switch block (BP1) 3, a measuring probe 4, including a reference part protected from the influence of a controlled environment (with electrical resistance Ro) and a multisection sensitive part (with electrical resistances of sections - R1, R2, ... RN), measuring channels 6 ¹ , 6 ² , ..., 6 ⁿ , each of which is formed by series-connected switch blocks (BP2) 5, low-pass filters (LPF) 7 and differential amplifiers (DU) 8, a multichannel analog-to-digital converter (MADC) 9 and a processor 10 configured to transmit data to a computer network. The outputs of IOT 1 and ANN 2 are connected to the inputs of BP1 3, which in turn is connected to the measuring probe 4. The outputs of the reference part Ro and the multi-section sensitive part R1, R2, ..., RN of the measuring probe 4 are connected to the inputs of BP2 5 of each measuring channel 6 ¹ , 6 ² , …, 6 ⁿ . The corresponding inputs of the MATsP 9 are connected to the outputs of the corresponding measuring channels 6 ¹ , 6 ² , ..., 6 ⁿ , and the digital output of the MATsP 9 is connected to the input of the processor 10, from the control outputs of which the control signals are fed to the switch blocks BP1 3 and BP2 5.

The multi-section sensitive part of the probe (Fig. 2a), including the actual sensitive sections 11 and the support section 12, is made in the form of a tape, one side of which faces the controlled environment, the others are recessed in the electrically insulating holder 13. The support section 12 has a coating that protects it from aggressive impact of a controlled environment, but maintaining thermal contact with it. Since the support section 12 and the sensing sections 11 are made of the same material, a good thermal connection is provided between them, which is also enhanced by contact through a controlled environment.

The input of the probe into the pipeline 14 is carried out through a standard input-output unit 15. For correct control of the environment, the sensor part of the probe must always be immersed in a layer of bottom mineralized water 16 (Fig. 2b).

In small diameter pipelines, where the mineralized water will not completely cover the sensing part of the probe, the probe shown in FIG. 3. Sensing sections 11 and its supporting section 12 are built into the lower generatrix of the pipeline 14, more precisely, a segment of the pipeline framed by flanges 18. An electronic unit 17 is located on the upper surface of the pipeline, including IOT 1, INS 2, BP1 3, measuring channels 6 ¹ , 6 ² , ..., 6 ⁿ , MATsP 9 and processor 10 (Fig. 1, Fig. 4) and representing a measuring transducer of a multichannel corrosion sensor that implements the electrical resistance method, which serves this probe.

For the purposes of using MDC in pipelines of large cross section, when the temperature non-uniformity of the controlled medium becomes significant, the best probe design will be a measuring probe (Fig. 4), made with a distributed support part, while behind each measuring channel 6 ¹ , 6 ² , ..., 6 ^n, its share of the reference part is fixed (with electrical resistances Ro1, Ro2, ..., RoN), to which the inputs of the switch blocks BP2 5 are connected, free from the corresponding sensitive sections of the probe 4, The design of the measuring probe with a distributed reference part 12 (similar to the probe in Fig. .2a) is shown in Fig. 5.

A version of the probe with a distributed support part 12, which is built into the lower generatrix of the pipeline (similar to the probe in Fig. 3), is shown in Fig. 6.

For the purposes of profiling, the MDK can be combined with flaw detectors (Fig. 7 and Fig. 8). When using an ultrasonic flaw detector (Fig. 7) on the outer surface of the pipeline, on the one hand, the primary sensors 19 of the ultrasonic flaw detector are placed, and on the other side, the electronic unit 20 of the ultrasonic flaw detector. When using a flaw detector that implements the field signature method (Field Signature Method, FSM™), on the outer side of the pipeline, on the one hand, the electrodes of the primary sensors 21 of the FSM flaw detector are placed, and on the other hand, the electronic unit 22 of the FSM flaw detector.

Device operation.

During the measurement process, the corrosion rate estimate is formed on the basis of data taken from the sensitive sections 11 of the probe, which are oriented parallel to the controlled flow of bottom mineralized water 16, thereby reproducing its corrosive effect on the inner surface of the pipeline 14.

All measurements in the device are carried out exclusively on direct current, which makes it possible to exclude the influence of the ferromagnetic properties of the sensor assembly of the probe on the measurement accuracy.

Each measuring channel 6 ¹ , 6 ² , ..., 6 ⁿ periodically measures two voltages - the voltage U _i on the sensitive section 11 and the corresponding voltage U _oi on the reference section 12 (for the version of the device shown in Fig. 1, instead of U _oi U _o is measured on a common bearing part). To get rid of additive errors due to bias voltages (contact potential difference, bias in differential amplifiers, etc.) in the elements of the measuring channel, the measurement of the mentioned voltages is carried out twice: with the forward direction of the reference current and the reverse one (due to the operation of BP1 3). The constant presence of the measured voltages in the range of operation of the measuring channels 6 ¹ , 6 ² , …, 6 ⁿ is provided by ANN 2. The measured voltage is supplied to the DU 8, free from high-frequency interference due to the LPF 7. It is assumed that such measurements are carried out for negligible time intervals.

Further, the following values are taken as the measurement result:

- напряжение, измеренное на i-ой чувствительной секции при прямом направлении опорного тока;Where

- voltage measured on the i-th sensitive section with the forward direction of the reference current;

- напряжение, измеренное на i-ой чувствительной секции при обратном направлении опорного тока;

- voltage measured on the i-th sensitive section with the reverse direction of the reference current;

U _ad - the total value of all components of the additive error of the measuring channel;

- напряжение, измеренное на i-ой опорной секции при прямом направлении опорного тока;

- voltage measured on the i-th reference section with the forward direction of the reference current;

- напряжение, измеренное на i-ой опорной секции при обратном направлении опорного тока.

- voltage measured on the i-th reference section with the reverse direction of the reference current.

The considered computational procedures are performed in the processor 10.

Each measuring channel 6 ¹ , 6 ² , …, 6 ⁿ together with the processor 10 implements the following transformation function (FC):

where h is the depth of penetration of corrosion at the time of measurement;

k - setting parameter programmed in the processor 10;

U _i - voltage on the i-th sensitive section 11 at the time of measurement;

ому каналу измерения (в тот же момент времени).U _oi - voltage on the support section 12 of the probe, corresponding

th measurement channel (at the same time).

Given that the same reference current flows through sensitive 11 and reference 12 sections, relation (1) can be reduced to the form:

where I _o - current IOT 1.

Note that for the variant of the device shown in Fig. 1, it is true:

U _oi =U _o and R _oi =R _o .

For the tape geometry of the measuring probe, the following applies:

R _oi =pl/S _o and R _i =pl/S _i ,

where p is the resistivity of the tape material;

l is the length of the sensitive 11 or reference 12 sections (assumed to be equal);

S _o - section of the support section 12 of the tape;

S _i - section of the sensitive section 11 of the tape.

Let the equivalent tape of the measuring probe have a cross section with parameters:

S _o =a⋅b and S _i =a⋅b _i ,

where a is the width of the tape;

b is the thickness of the support section 12 of the tape;

b _i - thickness of the sensitive section 11 of the tape.

Considering that only one side of the tape is made accessible to the controlled environment, we can write:

As you can see, if you program k=b, then the result of the calculation by formula (3) will be directly the penetration depth h of corrosion, expressed in units of b.

Having the values of the value of h with reference to the corresponding moments of measurements, it is easy to obtain (using the processor 10) an estimate of the corrosion rate at the locations of the sensitive sections 11. If the temperature fluctuations of the controlled environment are insignificant, then the calculation of the corrosion rate _Vcor can be performed using the formula:

where t _exp - duration of exposure of the probe in a controlled environment;

h ₁ - depth of penetration of corrosion at the beginning of the exposure interval;

h ₂ - depth of penetration of corrosion at the end of the exposure interval.

With significant temperature fluctuations of the controlled environment, it is advisable to use the least squares method (or in other words: linear regression) to obtain V _cor for a number of measured values: h ₁ , h ₂ , …, h _n . The formula for calculations is as follows:

Where

m is the number of measurements of h _j values in the probe exposure interval.

Thus, in the proposed device, the "binding" of the measurement result in the measurement channel to a very small fragment (section) of the measuring probe is implemented. Its minimum size is determined by the number of channels: the more channels, the smaller the size can be. Due to these circumstances, the possibility of multichannel monitoring of the corrosion rate in the bottom mineralized water of the pipelines of the oil gathering system is provided. The dynamic capabilities due to the use of a modern element base (when implemented) are several decimal orders higher than the MDC based on gravimetry.

From the foregoing, it follows that the purpose of the proposed invention-device - operational multi-channel monitoring of the corrosion rate in the flow of bottom mineralized water of the pipelines of the oil collection system - is achieved.

An example of the implementation of the proposed method

First, we note that the method adopted as a prototype (described in the work of Markin A.N., Markin I.A. Calculation of the maximum rate of local corrosion of pipelines of oil gathering systems according to weight measurements obtained using corrosion control samples. // Oilfield business. 2020. No. 12. P. 70-73.), experimentally confirmed only for gravimetric sensors.

However, in the work of Blokhin, V.A. Features of measuring the parameters of carbon dioxide corrosion in gas environments / V.A. Blokhin, A.K. Manzhosov, A.N. Markin // Corrosion 2018 No. 1 (39), 54-62 an analysis of similarities and differences in the functioning of sensors that implement the electrical resistance method and gravimetric ones has already been carried out. An ER meter has been proven to be similar to a gravimetric sensor when the following conditions are met:

- the duration of exposure of the sensor probe that implements the electrical resistance method (for taking a single measurement) should be such that the depth of corrosion penetration into its sensitive element does not go beyond 0.4% ... 1.0% of half the thickness of the sensitive element;

- during the stay of the sensor probe, which implements the electrical resistance method, in a controlled environment, the measured series of corrosion rate values (obtained for the correct, in terms of duration, exposure intervals) are accumulated, and at the end of it, the arithmetic mean of these values is calculated, which is taken as the final estimate corrosion rates.

When implementing the proposed method based on MDK, which implements the method of electrical resistance, the sensors are installed in places controlled by TSSN, which give an idea of the entire range of corrosiveness of the transported medium. All MDCs that implement the electrical resistance method must be networked for prompt presentation of measurement results and their subsequent processing.

The measuring probe of each MDK that implements the electrical resistance method is exposed at its monitoring point for a period of time sufficient for subsequent correct profiling of its sensitive part.

After the expiration of the exposure time, each probe is profiled, data is processed with a mandatory assessment of the maximum depth of corrosion damage, and the measurement results of the corrosion rate are read for each measuring channel of the MDK, which implements the electrical resistance method.

After exposure, the measuring probe is removed from the pipeline, cleaned of dirt, and profiling is performed by starting the program for scanning the surface of the measuring probe with the probe of the profilometer. It should be noted that at present, the precision of contact profilometers is still higher than that of flaw detectors implementing the Field Signature Method (FSM™) or ultrasonic flaw detectors (although their characteristics are rapidly improving).

To implement the method, stationary profilometers similar to the Proton 130 model are most suitable for implementing the method, since their resident computers also allow, in addition to controlling the drive, to easily integrate into a computer network and transfer profiling results to it.

The data taken from the MDM, which implements the electrical resistance method, and devices that perform profiling (contact profilometer, ultrasonic flaw detector, FSM), before being transferred to the system (more precisely, the operator's computer), are subjected to primary filtering.

From the mentioned devices, the following are transmitted to the system:

- data on the maximum depth of corrosion in each measuring probe;

- values of the corrosion rate obtained in each measuring channel of the MDK, which implements the method of electrical resistance.

In turn, the system (operator's computer) calculates:

- maximum local corrosion rate V _maxi for each probe;

- standard deviation (RMS), or, in other words - sample standard deviation V _skoi ;

- according to the accumulated data: V _{max 1} , V _{max 2} , … V _{max m} ; V _{sko 1} , V _{sko 2} , … V _{sko m} , calculations are made (by the method of least squares) of the coefficients A, B of the regression line.

Upon completion of these computational procedures and obtaining the desired coefficients of the regression line, the operator's computer receives only the measurement results from the MDK, which implements the electrical resistance method, to calculate the current estimate of the maximum corrosion rate V _max . The need for subsequent calculations of the values of the coefficients A, B may arise only when the composition of the transported medium changes significantly.

The operator's computer also performs the final processing of the results and their display.

The considered system allows another redistribution in data processing. Thus, it is possible to transfer to the system from the MDK, which implements the electrical resistance method, instead of the corrosion rate values in each measuring channel, only the corrosion penetration depth values, according to which, then, the corrosion rate values are calculated in the operator’s computer. This approach makes it possible to apply much more efficient algorithms for calculating the corrosion rate under conditions of strong interference, since the computing power of the operator's computer is incomparable with the capabilities of microcontrollers in the MDC that implements the electrical resistance method.

Below are the formulas for the considered computational procedures and the order in which they follow.

From the data on the maximum depth of corrosion in each probe and the values of the corrosion rate obtained in each measuring channel, the following values are calculated:

- maximum local corrosion rate V _{max i} according to the formula:

where D _{max i} - maximum depth of local corrosion damage of the i-th probe;

Т _ei - exposure time of the i-th probe,

and also, the standard deviation (RMS), or, in other words, the sample standard deviation V _{RMS i} .

where V _ki is the corrosion rate measured in the k-th measurement channel of the i-th MDC, which implements the electrical resistance method;

n is the number of measuring channels of the MDK that implements the electrical resistance method;

- среднее арифметическое значение скорости коррозии по результатам измерения в n измерительных каналах i-го МДК, реализующего метод электрического сопротивления.

- arithmetic mean value of the corrosion rate based on the results of measurements in n measuring channels of the i-th MDC, which implements the electrical resistance method.

Based on the received data array (V _{max 1} , V _{max 2} , ... V _{max m} ; V _{sko 1} , V _{sko 2} , ... V _{sko m} ) calculate the coefficients of the regression line using the least squares method and, thereby, obtain a functional dependence of the maximum speed local corrosion _Vmax from the results of measurements of the MPC, which implements the method of electrical resistance, namely:

Where

where m is the number of monitoring points.

In the future, the obtained dependence is used for dynamic monitoring of the level of local corrosion in a controlled TSSN.

Thus, the proposed method provides the ability to quickly monitor the level of local corrosion in the pipelines of oil gathering systems due to:

- application of a high-speed (with a short response time) multi-channel corrosion sensor that implements the electrical resistance method;

developed communication capabilities of a modern computer network, which significantly speeds up the removal of measurement information from corrosion monitoring points (probes) of oil gathering system pipelines;

- high computing power of a computer network.

Claims (6)

1. A multichannel corrosion sensor that implements the electrical resistance method, including a reference current source, differential amplifiers, a processor capable of transmitting data to a computer network, a multichannel analog-to-digital converter, low-pass filters, switch blocks, a bias voltage source, and the output of the reference current source and the output of the bias voltage source are connected to the inputs of the first block of switches, the outputs of which are connected to the inputs of the measuring probe, and the outputs of each section of the sensitive part of the measuring probe are connected to an individual measuring channel formed by the series-connected block of switches, a low-pass filter and a differential amplifier , while the outputs of each measuring channel are connected to the analog inputs of a multichannel analog-to-digital converter, the digital output of which is connected to the processor, and the control outputs of the processor are connected to the circuit control lines of the switch blocks, a measuring probe containing a reference part protected from the influence of a controlled environment and a multi-section sensitive part made of the same material as the in-line process equipment, and the reference part of the measuring probe is either connected to the free inputs of the switch block of each measuring channel, or is made distributed so that each share of the reference part is located on the corresponding part of the surface of the measuring probe, and is connected to the free inputs of the switch block of the corresponding measuring channel, characterized in that the sensitive part of the measuring probe is immersed in a layer of bottom mineralized water. 2. The device according to p. 1, characterized in that all sensitive sections of the measuring probe are located in the same plane and oriented parallel to the flow of the controlled medium. 3. The device according to claim 1, characterized in that the measuring probe is made in the form of a metal tape located along the inner generatrix of the pipeline. 4. A method for indicating the level of local corrosion in the pipelines of an oil gathering system, including the placement of multichannel corrosion sensors with a sensor part that allows profiling, on the pipelines of the system, which provide information on the corrosive activity of the transported medium in its entire range, the implementation of the required exposure for each multichannel corrosion sensor , profiling of the sensor part of the measuring channels of each multichannel corrosion sensor after exposure, processing of profiling data containing an estimate of the maximum depth of local corrosion damage and, on its basis, the maximum local corrosion rate, processing of measurement data by each multichannel corrosion sensor with an estimate of the root mean square deviation of the corrosion rate for all channels, the formation of a data array from the obtained estimates and the results of profiling to calculate the coefficients of the regression line using the method of least squares, subsequent assessment, by means of multichannel corrosion sensors, of the level of local corrosion, taking into account the calculated coefficients, characterized in that the device according to any one of paragraphs is used as a multichannel corrosion sensor. 1-3, while the processing and evaluation of the measurement results, as well as the calculation of the coefficients of the regression line is carried out in an automated mode by means of a computer. 5. The method according to claim 4, characterized in that an ultrasonic flaw detector is used as a profiling device. 6. The method according to claim 4, characterized in that a flaw detector is used as a profiling device that implements the Field Signature Method (FSM).

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