CN111006849B - Method and system for judging laying state of oil-gas pipeline accompanying optical cable - Google Patents
Method and system for judging laying state of oil-gas pipeline accompanying optical cable Download PDFInfo
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Abstract
The invention discloses a method and a system for judging the laying state of an oil-gas pipeline accompanying optical cable, wherein the method comprises the following steps: laying an accompanying optical cable along the oil and gas pipeline, wherein optical fibers are arranged in the optical cable, and detection units are arranged in an optical fiber link at certain intervals; monitoring negative pressure vibration generated by starting and stopping a pump or adjusting a valve in an oil and gas pipeline through a detection unit, wherein the monitoring data comprises a negative pressure wave vibration signal acquired by the detection unit and corresponding propagation time; splicing data acquired by a plurality of detection units to obtain a vibration intensity signal matrix of the whole optical fiber link; processing the vibration intensity signal matrix to draw a waterfall graph; and performing morphological analysis on the waterfall graph, and if the position with the sudden change of the slope appears in the waterfall graph, judging that the optical fiber corresponding to the position is coiled or deviates from the pipeline. The invention does not need to manually search point by point on site, is simple and efficient, has no influence on measurement precision by manual sampling distance intervals, and can measure the area which cannot be reached by people by walking.
Description
Technical Field
The invention relates to the technical field of laying of oil and gas pipelines and optical cables, in particular to a method and a system for judging laying states of oil and gas pipelines and optical cables.
Background
At present, optical fiber communication becomes the main mode of the current oil and gas pipeline communication construction, and at present, two methods for positioning the optical cable are mainly used, one method is to position the optical cable by using an optical cable routing detector, the principle is that a transmitter in a detecting instrument generates electromagnetic waves with specific frequency, a transmitting signal is transmitted to a metal component (aluminum foil or reinforced core) of an underground optical cable in different transmitting connection modes, after the underground metal component senses the electromagnetic waves, induced current is generated on the surface of the metal part, the induced current can be propagated to the far away along the metal part, during the current propagation, electromagnetic waves are radiated to the ground through the underground metal part, therefore, when the pipeline positioning instrument receiver detects on the ground, the electromagnetic wave signals can be received on the ground right above the optical cable, and the underground pipeline positioning instrument can judge the position and the trend of the optical cable through the strength change of the received signals. However, the disadvantage is that the cable jacket (or strength member) needs to be connected to the detector transmitter and, as the cable detection signal decays, the transmitter needs to be re-installed at a selected point when the effective detection distance of the receiver is exceeded. When the transmitter cannot be installed at the optical cable test pile, a pit needs to be excavated at the break of the optical cable test signal, the optical cable is pulled out, the armor is exposed, the transmitter is installed, and the test is continued. The implementation workload is large and the time consumption is long. For the optical cable test section which cannot be passed by the detection personnel by walking due to geographic environmental factors, only the optical cable data at two ends of the optical cable test section can be measured, and the measurement precision is influenced by the sampling distance interval. And the optical cable winding point cannot be judged and positioned.
The other type is that an optical fiber vibration monitoring system is utilized, and the positioning of an oil-gas pipeline accompanying optical cable can also be realized. The optical fiber vibration monitoring system is used for calibration, although the optical fiber vibration monitoring system is not limited by effective detection distance, the investment of manpower and material resources can be reduced, but only optical cable data at two ends of sections (such as crossing channels, rivers, ponds, crossing roads and the like) which cannot be reached by people by walking can be measured; when the directional drill and the like are buried too deeply, the situation that the vibration signal cannot be received and the positioning cannot be carried out can occur, and the measurement accuracy is also influenced by the sampling distance interval. Through the judgment of the length range of the optical cable influenced by the vibration waves, the repaired optical cable winding point can be positioned, but due to the limitation of distance sampling precision and geographic environment, omission possibility exists.
Disclosure of Invention
The invention aims to solve the technical problems that in the prior art, coiled optical cables cannot be found out, positioning cannot be carried out on complex conditions such as directional drilling and the like, cost is high and the like, and provides a method and a system for judging the laying state of an oil-gas pipeline accompanying optical cable.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a method for judging the laying state of an oil-gas pipeline accompanying optical cable, which comprises the following steps:
s1, laying an accompanying optical cable along the oil and gas pipeline, wherein optical fibers are arranged in the optical cable, and detection units are arranged in an optical fiber link at intervals;
s2, monitoring the negative pressure vibration generated by starting and stopping a pump or adjusting a valve in an oil-gas pipeline through the detection units, wherein the monitoring data comprise negative pressure wave vibration signals acquired by the detection units and corresponding propagation time;
s3, performing data splicing on the negative pressure wave vibration signals acquired by the plurality of detection units and the corresponding propagation time to obtain a vibration intensity signal matrix of the whole optical fiber link;
s4, processing the vibration intensity signal matrix, arranging by taking the distance as a horizontal axis and the time as a vertical axis, mapping each vibration intensity value in the vibration intensity signal matrix into an interval of a certain value range, and drawing a waterfall graph;
s5, performing morphological analysis on the waterfall graph, if the position with a sudden change of slope appears in the waterfall graph, judging that the optical fiber corresponding to the position is coiled or deviated from the pipeline, and searching the actual position of the optical fiber coiled or deviated from the pipeline in the optical fiber link according to the detection unit corresponding to the position.
Further, the method for acquiring the negative pressure wave vibration signal by the detection unit in step S2 of the present invention specifically includes:
in a period of time, carrying out continuous space and time signal sampling on the vibration signals detected by each detection unit in the optical fiber link; recording the sampling frequency as FHz, and the number of the detection units as N, so that an array of FHz rows by N columns can be acquired every second; the horizontal axis of the array records continuous space information, and the vertical axis records continuous time information, so that the array contains all continuous space and time information of negative pressure wave vibration signals generated by starting and stopping a pump or adjusting a valve;
for the vibration signal collected by each detection unit, the actual detection signal is x (t), and is composed of a real signal f (t) and system noise n (t), that is: x (t) ═ f (t) + n (t); the system noise n (t) is optical noise and is concentrated in a low frequency band; therefore, the signal sequence is subjected to high-pass filtering in the time domain by a difference calculation method, and low-frequency optical noise n (t) is eliminated.
Further, the method for processing the actual detection signal in step S2 of the present invention is as follows:
for the actual detection signal, i.e. the continuous vibration signal x (t), x (t) is the acquired amplitude value sequence; the detector output electrical signal is represented as:
wherein, Ps(t)PL(t) are respectively a signal light and an intrinsic light amplitude signal, and Δ ω represents a frequency difference between the rayleigh backscattered light and the local oscillator light; phi (t) represents the phase of the Rayleigh backscattered light, which includes phase changes caused by intrusion, and phase changes caused by noise; extracting amplitude by mixing the electric signal with sine and cosine signals with frequency delta omega
And the phase phi (t) to obtain a sequence of amplitude values x (t).
Further, the method for obtaining the vibration intensity signal matrix in step S3 of the present invention specifically includes:
continuously acquiring a vibration intensity signal of a period of time T seconds, namely a negative pressure wave vibration signal, by using detection units according to a certain frequency FHz, wherein each detection unit obtains an array of FT multiplied by 1;
dividing the data into a section according to m data points, and calculating the difference between the maximum value and the minimum value of each section of data to obtain an array of FT/m multiplied by 1;
and recording the number of the detection units as N, splicing the arrays obtained by all the detection units according to the position sequence to obtain an array of FT/m multiplied by N, namely a vibration intensity signal matrix of the whole optical fiber link within a period of time.
Further, the specific form of the vibration intensity signal matrix obtained in step S3 of the present invention is:
for each detection unit, the acquired negative pressure wave vibration signal generated by starting and stopping the pump or regulating the valve is expressed as: x (t), namely, recording the intensity value of the vibration signal at each time point; for all the detection units on the whole optical fiber link, corresponding to the serial numbers 1 to N, the vibration intensity signal matrix is expressed as: | x1(t),x2(t),...,xN(t)|。
Further, in step S4 of the present invention, the specific method for processing the vibration intensity signal matrix to obtain the waterfall graph is as follows:
arranging the acquired vibration intensity signal matrix of each group of negative pressure waves by taking the distance as a horizontal axis and the time as a vertical axis; each scale of the horizontal axis represents a detection unit, and the coordinate value of the detection unit represents the serial number of the arrangement position of the detection unit in the optical fiber link; each scale of the longitudinal axis represents the duration of m/F seconds, and the longitudinal axis is the time flowing direction from top to bottom; and mapping each value in the matrix, namely the intensity of the vibration signal, into an interval from 0 to 255 to draw a waterfall graph.
Further, in the waterfall graph of step S5 of the present invention, the vibration intensity signal matrix forms a straight line with a certain slope, and the expression form is:
note that the actual fiber link length between 2 detection units is L, unit: m, the length of the optical fiber link corresponding to one detection unit is LoThe unit: m, the speed of negative pressure wave propagating along the pipeline is V, unit: m/s, the slope of the line
Expressed as:
further, the specific method for determining the abrupt change of the slope in step S5 of the present invention is as follows:
for each detection unit, calculating the slope of the position of the detection unit to obtain a sequence | k1,k2,...,kNDifferential calculation is performed on this sequence, i.e.: diff (diff)k(i)＝ki+1-kiWherein the value range of i is from 1 to N-1 to obtain a sequence
Traverse the sequence to find all diffskThe corresponding serial numbers with the numerical values smaller than a certain threshold value are divided to find each diffkThe starting sequence number and the ending sequence number of the continuous section with the numerical value smaller than a certain threshold value correspond to the monitoring unit sequence numbers of the starting position and the ending position of a section of coiled optical fiber; diff (diff)kAnd judging the point with the numerical value larger than a certain threshold value as a slope catastrophe point.
The invention provides a system for judging the laying state of an oil-gas pipeline accompanying optical cable, which comprises:
the accompanying optical cable is laid along the oil and gas pipeline, and optical fibers are arranged in the optical cable;
the detection units are arranged in the optical fiber link at intervals, the detection units are used for monitoring the negative pressure vibration generated by starting and stopping a pump or adjusting a valve in an oil and gas pipeline, and monitoring data comprise negative pressure wave vibration signals acquired by each detection unit and corresponding propagation time; sending the monitoring data to a remote vibration signal processing unit;
the vibration signal processing unit is used for carrying out data splicing on the negative pressure wave vibration signals acquired by the plurality of detection units and the corresponding propagation time to obtain a vibration intensity signal matrix of the whole optical fiber link; processing the vibration intensity signal matrix, arranging by taking the distance as a horizontal axis and the time as a vertical axis, mapping each vibration intensity value in the vibration intensity signal matrix into an interval of a certain value range, and drawing into a waterfall graph;
and the display unit is used for carrying out morphological analysis on the waterfall graph, judging that the optical fiber corresponding to the position is coiled or deviated from the pipeline if the position with the sudden change of the slope appears in the waterfall graph, and searching the actual position of the optical fiber coiled or deviated from the pipeline in the optical fiber link according to the detection unit corresponding to the position.
The invention has the following beneficial effects: the method and the system for judging the laying state of the oil-gas pipeline accompanying optical cable can utilize the characteristic of continuous measurement of the distributed optical fiber sensing technology, do not need to manually search point by point on site, and are simple and efficient. The measurement precision is not influenced by artificial sampling distance intervals, and the area which cannot be reached by people can be measured without missing positions.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a block diagram of a method flow of an embodiment of the present invention.
Fig. 2 is a waterfall graph of a fiber link vibration intensity signal matrix of about 23.23 km in 30 seconds.
FIG. 3 is a waterfall plot of a vibration intensity signal matrix for a fiber optic cable coiling position.
FIG. 4 is a waterfall plot of a vibration intensity signal matrix for fiber optic cables offset from the location of the conduit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the method for judging the laying state of the optical cable accompanied by the oil and gas pipeline in the embodiment of the present invention includes the following steps:
s1, laying an accompanying optical cable along the oil and gas pipeline, wherein optical fibers are arranged in the optical cable, and detection units are arranged in an optical fiber link at intervals;
s2, monitoring the negative pressure vibration generated by starting and stopping a pump or adjusting a valve in an oil-gas pipeline through the detection units, wherein the monitoring data comprise negative pressure wave vibration signals acquired by the detection units and corresponding propagation time;
the method for acquiring the negative pressure wave vibration signal by the detection unit in the step S2 specifically comprises the following steps:
in a period of time, carrying out continuous space and time signal sampling on the vibration signals detected by each detection unit in the optical fiber link; recording the sampling frequency as FHz, and the number of the detection units as N, so that an array of FHz rows by N columns can be acquired every second; the horizontal axis of the array records continuous space information, and the vertical axis records continuous time information, so that the array contains all continuous space and time information of negative pressure wave vibration signals generated by starting and stopping a pump or adjusting a valve; the existing method cannot realize continuous data sampling in space and time.
For the vibration signal collected by each detection unit, the actual detection signal is x (t), and is composed of a real signal f (t) and system noise n (t), that is: x (t) ═ f (t) + n (t); the system noise n (t) is optical noise and is concentrated in a low frequency band; therefore, the signal sequence is subjected to high-pass filtering in the time domain by a difference calculation method, and low-frequency optical noise n (t) is eliminated.
The method for processing the actual detection signal comprises the following steps:
for the actual detection signal, i.e. the continuous vibration signal x (t), x (t) is the acquired amplitude value sequence; the detector output electrical signal is represented as:
wherein, Ps(t)PL(t) are respectively a signal light and an intrinsic light amplitude signal, and Δ ω represents a frequency difference between the rayleigh backscattered light and the local oscillator light; phi (t) represents the phase of the Rayleigh backscattered light, which includes phase changes caused by intrusion, and phase changes caused by noise; extracting amplitude by mixing the electric signal with sine and cosine signals with frequency delta omega
And the phase phi (t) to obtain a sequence of amplitude values x (t).
S3, performing data splicing on the negative pressure wave vibration signals acquired by the plurality of detection units and the corresponding propagation time to obtain a vibration intensity signal matrix of the whole optical fiber link;
the method for obtaining the vibration intensity signal matrix in step S3 specifically includes:
continuously acquiring a vibration intensity signal of a period of time T seconds, namely a negative pressure wave vibration signal, by using detection units according to a certain frequency FHz, wherein each detection unit obtains an array of FT multiplied by 1;
dividing the data into a section according to m data points, and calculating the difference between the maximum value and the minimum value of each section of data to obtain an array of FT/m multiplied by 1;
and recording the number of the detection units as N, splicing the arrays obtained by all the detection units according to the position sequence to obtain an array of FT/m multiplied by N, namely a vibration intensity signal matrix of the whole optical fiber link within a period of time.
The specific form of the obtained vibration intensity signal matrix is as follows:
for each detection unit, the acquired negative pressure wave vibration signal generated by starting and stopping the pump or regulating the valve is expressed as: x (t), namely, recording the intensity value of the vibration signal at each time point; for all the detection units on the whole optical fiber link, corresponding to the serial numbers 1 to N, the vibration intensity signal matrix is expressed as: | x1(t),x2(t),...,xN(t)|。
S4, processing the vibration intensity signal matrix, arranging by taking the distance as a horizontal axis and the time as a vertical axis, mapping each vibration intensity value in the vibration intensity signal matrix into an interval of a certain value range, and drawing a waterfall graph;
in step S4, the specific method for processing the vibration intensity signal matrix to obtain the waterfall graph is as follows:
arranging the acquired vibration intensity signal matrix of each group of negative pressure waves by taking the distance as a horizontal axis and the time as a vertical axis; each scale of the horizontal axis represents a detection unit, and the coordinate value of the detection unit represents the serial number of the arrangement position of the detection unit in the optical fiber link; each scale of the longitudinal axis represents the duration of m/F seconds, and the longitudinal axis is the time flowing direction from top to bottom; and mapping each value in the matrix, namely the intensity of the vibration signal, into an interval from 0 to 255 to draw a waterfall graph.
S5, performing morphological analysis on the waterfall graph, if the position with a sudden change of slope appears in the waterfall graph, judging that the optical fiber corresponding to the position is coiled or deviated from the pipeline, and searching the actual position of the optical fiber coiled or deviated from the pipeline in the optical fiber link according to the detection unit corresponding to the position.
In the waterfall graph of step S5, the vibration intensity signal matrix forms a straight line with a certain slope, and the expression form is:
note that the actual fiber link length between 2 detection units is L, unit: m, the length of the optical fiber link corresponding to one detection unit is LoThe unit: m, the speed of negative pressure wave propagating along the pipeline is V, unit: m/s, the slope of the line
Expressed as:
the specific method for judging the slope mutation is as follows:
for each detection unit, calculating the slope of the position of the detection unit to obtain a sequence | k1,k2,...,kNDifferential calculation is performed on this sequence, i.e.: diff (diff)k(i)＝ki+1-kiWherein the value range of i is from 1 to N-1 to obtain a sequence
Traverse the sequence to find all diffskThe corresponding serial numbers with the numerical values smaller than a certain threshold value are divided to find each diffkThe starting sequence number and the ending sequence number of the continuous section with the numerical value smaller than a certain threshold value correspond to the monitoring unit sequence numbers of the starting position and the ending position of a section of coiled optical fiber; diff (diff)kAnd judging the point with the numerical value larger than a certain threshold value as a slope catastrophe point.
In another embodiment of the invention, as shown in fig. 2:
the vibration intensity signals received by all the detection units in the range of the detection length of the optical fiber are collected, and each time, a period of time is continuously collected, such as: for 30 seconds. When the sampling rate is 400Hz, 12000 x 1 data can be obtained for each detection unit, the data is divided into a section according to each 0.02 second (namely 8 data points), and the difference between the maximum value and the minimum value of each section is calculated, so that a series of 1500 x 1 arrays can be obtained. Recording the number of the detection units as N, splicing the arrays obtained by all the detection units according to the position sequence to obtain a 1500 multiplied by N matrix, namely obtaining a vibration intensity signal matrix of the whole optical fiber link in a period of time (30 seconds), and arranging the collected vibration intensity signal matrix (a 1500 multiplied by N matrix) of each group of negative pressure waves by taking the distance as a horizontal axis and the time as a vertical axis. Each scale of the horizontal axis represents a detection unit, and the coordinate value of the scale represents the serial number of the arrangement position of the detection unit in the optical fiber link. Each scale on the vertical axis represents a time period of 0.02 seconds, with the vertical axis from top to bottom being the direction of time flow. And mapping each value in the matrix, namely the intensity of the vibration signal, into an interval from 0 to 255 to draw a waterfall graph. From the waterfall chart of the vibration intensity signal matrix of fig. 2, it can be roughly estimated that the vibration generated by the negative pressure wave of the pipeline has a propagation speed of about 860m/s (10 meters of optical fiber for each detection unit) along the pipeline. In the waterfall chart, a line with a gentle slope can be seen, and the position of coiling or deviation from a pipeline in the optical cable link can be found through analyzing the line with the slope.
The method for finding the cable winding position in the cable link is shown in fig. 3, and the starting point and the ending point are marked in fig. 3 for each part without slope (i.e. horizontal line shape) appearing in the line. The principle of the method is as follows: when a section of coiling occurs in the optical fiber, the time when the negative pressure wave reaches each detection unit of the coiling section is the same, so the corresponding line form is a horizontal straight line, and for the position of normal laying, the time when the negative pressure wave reaches each detection unit is different, so the corresponding line form is a straight line with a certain slope, therefore, 4 sections of coiling regions can be found in fig. 3, and the starting point and the end point are respectively: 405 and 430, 955 and 980, 1151 and 1173, 1402 and 1560.
Method of finding the position of a cable in a cable link that deviates from the conduit is shown in fig. 4, where the start and end points are marked for each broken (or darker colored) part of the line that appears in fig. 4. The principle of the method is as follows: the vibration generated by the negative pressure wave is transmitted along the pipeline, when the optical cable link deviates far from the pipeline, the soil medium absorbs most of the vibration, so that the vibration signal sensed by the optical cable at the section is greatly weakened, and the corresponding line color is relatively dark. In fig. 4, 2 areas of deviating pipe can be found, the starting point and the end point being respectively: 715 and 970, 1620 and 2323.
In conclusion, a plurality of groups of negative pressure wave signals caused by the starting and stopping of the pump, valve adjustment and the like are collected, and the vibration intensity matrix waterfall graph of each group of signals is respectively searched and positioned for the positions of the coiled and deviated pipelines in the optical cable link. And comparing the multiple groups of positioning results, and averaging to determine the positions of the coiled and deviated pipelines in the optical cable link.
The system for judging the laying state of the oil-gas pipeline accompanying optical cable comprises:
the accompanying optical cable is laid along the oil and gas pipeline, and optical fibers are arranged in the optical cable;
the detection units are arranged in the optical fiber link at intervals, the detection units are used for monitoring the negative pressure vibration generated by starting and stopping a pump or adjusting a valve in an oil and gas pipeline, and monitoring data comprise negative pressure wave vibration signals acquired by each detection unit and corresponding propagation time; sending the monitoring data to a remote vibration signal processing unit;
the vibration signal processing unit is used for carrying out data splicing on the negative pressure wave vibration signals acquired by the plurality of detection units and the corresponding propagation time to obtain a vibration intensity signal matrix of the whole optical fiber link; processing the vibration intensity signal matrix, arranging by taking the distance as a horizontal axis and the time as a vertical axis, mapping each vibration intensity value in the vibration intensity signal matrix into an interval of a certain value range, and drawing into a waterfall graph;
and the display unit is used for carrying out morphological analysis on the waterfall graph, judging that the optical fiber corresponding to the position is coiled or deviated from the pipeline if the position with the sudden change of the slope appears in the waterfall graph, and searching the actual position of the optical fiber coiled or deviated from the pipeline in the optical fiber link according to the detection unit corresponding to the position.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (7)
1. A method for judging the laying state of an oil-gas pipeline accompanying optical cable is characterized by comprising the following steps:
s1, laying an accompanying optical cable along the oil and gas pipeline, wherein optical fibers are arranged in the optical cable, and detection units are arranged in an optical fiber link at intervals;
s2, monitoring the negative pressure vibration generated by starting and stopping a pump or adjusting a valve in an oil-gas pipeline through the detection units, wherein the monitoring data comprise negative pressure wave vibration signals acquired by the detection units and corresponding propagation time;
s3, performing data splicing on the negative pressure wave vibration signals acquired by the plurality of detection units and the corresponding propagation time to obtain a vibration intensity signal matrix of the whole optical fiber link;
s4, processing the vibration intensity signal matrix, arranging by taking the distance as a horizontal axis and the time as a vertical axis, mapping each vibration intensity value in the vibration intensity signal matrix into an interval of a certain value range, and drawing a waterfall graph;
s5, performing morphological analysis on the waterfall graph, if the position with a sudden change of slope appears in the waterfall graph, judging that the optical fiber corresponding to the position is coiled or deviated from the pipeline, and searching the actual position of the optical fiber coiled or deviated from the pipeline in the optical fiber link according to the detection unit corresponding to the position;
in the waterfall graph of step S5, the vibration intensity signal matrix forms a straight line with a certain slope, and the expression form is:
note that the actual fiber link length between 2 detection units is L, unit: m, the length of the optical fiber link corresponding to one detection unit is LoThe unit: m, the speed of negative pressure wave propagating along the pipeline is V, unit: m/s, the slope of the line
Expressed as:
the specific method for judging the abrupt change of the slope in the step S5 is as follows:
for each detection unit, calculating the slope of the position of the detection unit to obtain a sequence | k1,k2,...,kNDifferential calculation is performed on this sequence, i.e.: diff (diff)k(i)＝ki+1-kiWherein the value range of i is from 1 to N-1 to obtain a sequence
Traverse the sequence to find all diffskThe corresponding serial numbers with the numerical values smaller than a certain threshold value are divided to find each diffkThe number of the beginning and the end of the successive segments having a value less than a certain threshold value, corresponding to the beginning of a segment of coiled optical fiberThe detection unit serial numbers of the starting position and the ending position; diff (diff)kAnd judging the point with the numerical value larger than a certain threshold value as a slope catastrophe point.
2. The method for judging the laying state of the oil and gas pipeline accompanying optical cable according to claim 1, wherein the method for acquiring the negative pressure wave vibration signal by the detection unit in the step S2 is specifically as follows:
in a period of time, carrying out continuous space and time signal sampling on the vibration signals detected by each detection unit in the optical fiber link; recording the sampling frequency as FHz, and the number of the detection units as N, so that an array of F rows by N columns can be acquired every second; the horizontal axis of the array records continuous space information, and the vertical axis records continuous time information, so that the array contains all continuous space and time information of negative pressure wave vibration signals generated by starting and stopping a pump or adjusting a valve;
for the vibration signal collected by each detection unit, the actual detection signal is x (t), and is composed of a real signal f (t) and system noise n (t), that is: x (t) ═ f (t) + n (t); the system noise n (t) is optical noise and is concentrated in a low frequency band; therefore, the signal sequence is subjected to high-pass filtering in the time domain by a difference calculation method, and low-frequency optical noise n (t) is eliminated.
3. The method for judging the laying state of the optical cable accompanied with the oil and gas pipeline according to claim 2, wherein the method for processing the actual detection signal in the step S2 is as follows:
for the actual detection signal, i.e. the continuous vibration signal x (t), x (t) is the acquired amplitude value sequence; the detection unit output electrical signal is represented as:
wherein, Ps(t)PL(t) are the signal light and the intrinsic light amplitude signal, respectively, and Δ ω represents the frequency difference between the rayleigh backscattered light and the intrinsic light; phi (t) denotes Rayleigh backscatteringThe phase of the light, which includes both intrusion induced phase changes and noise induced phase changes; extracting amplitude by mixing the electric signal with sine and cosine signals with frequency delta omega
And the phase phi (t) to obtain a sequence of amplitude values x (t).
4. The method for judging the laying state of the oil and gas pipeline accompanied optical cable according to claim 1, wherein the method for obtaining the vibration intensity signal matrix in the step S3 is specifically as follows:
continuously acquiring a vibration intensity signal of a period of time T seconds, namely a negative pressure wave vibration signal, by using detection units according to a certain frequency FHz, wherein each detection unit obtains an array of FT multiplied by 1;
dividing the data into a section according to m data points, and calculating the difference between the maximum value and the minimum value of each section of data to obtain an array of FT/m multiplied by 1;
and recording the number of the detection units as N, splicing the arrays obtained by all the detection units according to the position sequence to obtain an array of FT/m multiplied by N, namely a vibration intensity signal matrix of the whole optical fiber link within a period of time.
5. The method for judging the laying state of the oil and gas pipeline accompanied optical cable according to claim 4, wherein the vibration intensity signal matrix obtained in the step S3 is in the specific form:
for each detection unit, the acquired negative pressure wave vibration signal generated by starting and stopping the pump or regulating the valve is expressed as: x (t), namely, recording the intensity value of the vibration signal at each time point; for all the detection units on the whole optical fiber link, corresponding to the serial numbers 1 to N, the vibration intensity signal matrix is expressed as: | x1(t),x2(t),...,xN(t)|。
6. The method for judging the laying state of the oil and gas pipeline accompanied optical cable according to claim 4, wherein the step S4 is to process the vibration intensity signal matrix, and the specific method for obtaining the waterfall diagram is as follows:
arranging the acquired vibration intensity signal matrix of each group of negative pressure waves by taking the distance as a horizontal axis and the time as a vertical axis; each scale of the horizontal axis represents a detection unit, and the coordinate value of the detection unit represents the serial number of the arrangement position of the detection unit in the optical fiber link; each scale of the longitudinal axis represents the duration of m/F seconds, and the longitudinal axis is the time flowing direction from top to bottom; and mapping each value in the matrix, namely the intensity of the vibration signal, into an interval from 0 to 255 to draw a waterfall graph.
7. The utility model provides a system for judge oil gas pipeline companion's optical cable laying state which characterized in that, this system includes:
the accompanying optical cable is laid along the oil and gas pipeline, and optical fibers are arranged in the optical cable;
the detection units are arranged in the optical fiber link at intervals, the detection units are used for monitoring the negative pressure vibration generated by starting and stopping a pump or adjusting a valve in an oil and gas pipeline, and monitoring data comprise negative pressure wave vibration signals acquired by each detection unit and corresponding propagation time; sending the monitoring data to a remote vibration signal processing unit;
the vibration signal processing unit is used for carrying out data splicing on the negative pressure wave vibration signals acquired by the plurality of detection units and the corresponding propagation time to obtain a vibration intensity signal matrix of the whole optical fiber link; processing the vibration intensity signal matrix, arranging by taking the distance as a horizontal axis and the time as a vertical axis, mapping each vibration intensity value in the vibration intensity signal matrix into an interval of a certain value range, and drawing into a waterfall graph;
the display unit is used for carrying out morphological analysis on the waterfall graph, judging that the optical fiber corresponding to the position is coiled or deviated from the pipeline if the position with the sudden change of the slope appears in the waterfall graph, and searching the actual position of the optical fiber coiled or deviated from the pipeline in the optical fiber link according to the detection unit corresponding to the position;
in the waterfall diagram, the vibration intensity signal matrix forms a straight line with a certain slope, and the expression form is as follows:
note that the actual fiber link length between 2 detection units is L, unit: m, the length of the optical fiber link corresponding to one detection unit is LoThe unit: m, the speed of negative pressure wave propagating along the pipeline is V, unit: m/s, the slope of the line
Expressed as:
the specific method for judging the slope mutation is as follows:
for each detection unit, calculating the slope of the position of the detection unit to obtain a sequence | k1,k2,...,kNDifferential calculation is performed on this sequence, i.e.: diff (diff)k(i)＝ki+1-kiWherein the value range of i is from 1 to N-1 to obtain a sequence
Traverse the sequence to find all diffskThe corresponding serial numbers with the numerical values smaller than a certain threshold value are divided to find each diffkThe starting sequence number and the ending sequence number of the continuous section with the numerical value smaller than a certain threshold value correspond to the sequence numbers of the detection units of the starting position and the ending position of a section of coiled optical fiber; diff (diff)kAnd judging the point with the numerical value larger than a certain threshold value as a slope catastrophe point.
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