CN103383242A - Freeze soil area oil and gas pipeline monitoring method - Google Patents

Abstract

The invention discloses a freeze soil area oil and gas pipeline monitoring method. The freeze soil area oil and gas pipeline monitoring method includes the steps of conducting monitoring on the temperatures and the moisture around pipelines and the displacement of a tube bodies through temperature sensor sets, moisture sensor sets and fiber bragg grating displacement sensor sets respectively, sending signals obtained through monitoring to a photoswitch (13) through optical cables (12), sending the signals to a lower computer (15) after the signals are demodulated by an interrogator (14), enabling the lower computer (15) to call self-programmed programs, control the photoswitch (13) and the interrogator (14), collect data and preprocess the data, transmitting the preprocessed data to a low-orbit satellite (17) through a satellite communication module (16), receiving the data through the low-orbit satellite (17) and forwarding the data to a satellite communication module (18), transmitting the received data to an upper computer (19) through the satellite communication module (18), analyzing and processing the data through the upper computer (19), and judging the safety condition of the pipelines to conduct damage forecasting. The freeze soil area oil and gas pipeline monitoring method is high in precision, high in stability and low in cost.

Description

A kind of permafrost region oil and gas pipes monitoring method

Technical field

The present invention is a kind of permafrost region oil and gas pipes monitoring method based on fiber grating sensing technology, and measurement, other class that relates to measurement of length, temperature do not comprise measurement, general control system and piping system technical field.

Background technology

Frozen soil is a kind of special great soil group, and temperature is subzero temperature or zero temperature, and contains the soil of ice, is called frozen soil.By the length of native frozen state retention time, frozen soil generally can be divided into again frozen soil (a few hours are to first quarter moon), seasonal frozen ground (first quarter moon is to the several months) and ever frost (more than 2 years) in short-term.China's frozen soil is grown very much, and the ever frost area is about 2,110,000 square kilometres, accounts for 23% of China's territory total area, accounts for the 3rd in the world, mainly is distributed in Qinghai-Tibet Platean, western high mountain and northeast Xing'anling mountains; The frost zone area is about 5,140,000 square kilometres, accounts for 53.5% of territory total area.Wherein, middle degree of depth seasonal frozen ground (＞1m) account for 1/3 of area, mainly be distributed in the ground such as three provinces in the northeast of China, the Inner Mongol, Gansu, Ningxia, In The North of Xinjiang, Qinghai and Chuan Xi.

Developed country's oil pipeline construction has more than 100 year history, and a lot of Frozen Ground Areas are contained huge hydrocarbon resources, and correspondingly the oil and gas pipes engineering design and construction becomes the up-to-date challenge of these regional petroleum industries.Since the sixties in 20th century, large diameter pipeline begins leading northern North america and Siberia Permafrost Area oil gas field transports market.During the Second World War, gram is exerted (Canol) pipeline and is transported crude oil to the Fairbanks city, Alaska State (Fairbanks) of the U.S. from Canadian Luo Man well; The oil pipe that caliber in 1956 is 203mm is built successfully from this city of Alaska State glycolylurea (Haines) to the Fei Bankesi city; 20 century 70s are early stage, and the USSR (Union of Soviet Socialist Republics) Permafrost Area has oil pipeline; 1977, long 1280km, diameter are that the oil pipeline of 1220mm is transported to the crude oil of U.S.'s Alaska State north slope low temperature Permafrost Area the natural warm water port Wa Erdisi (Valdez) in south, Alaska continuously, and then oil tanker arrives the California with crude oil transportation.20th century the mid-80, economize the environment temperature pipeline of northern our horse (Zama) lake, long 869km, bore 30.5cm from Canadian Luo Man well to Canadian Ahlport (Alberta) and complete laying on time, the Luo Man well conduit is the oil pipeline that Canadian Permafrost Area article one is buried underground fully.These pipelines are during runing, and the threat that all is subject to permafrost region frozen swell and melt settlement disaster even destroys.Wherein, gram is exerted (Canol) pipeline after bringing into operation front 9 months, and pipeline approximately has 700x10 along the line ⁴The L crude oil leakage.12700m on the Mackenzie riverbank ³Storage tank farm break, most of oil storage flows in the river.After Japan surrenders in 1945, this pipeline is removed soon; The Luo Man well conduit is along the line by way of discontinuous ever frost, construction and frost heave and the thaw collapse problem of meeting in service, by reaching the monitoring of 17 years, find that pipeline ever frost along the line continues to melt and sedimentation causes thaw depth to reach 3-5m (gyittja) or 5-7m (coarse particle mineral soil), and significant land subsidence.

The long oil and gas pipeline of article one that China builds in Permafrost Area, i.e. Golmud-Lhasa oil pipeline (be called for short lattice bracing wire), the lattice bracing wire was constructed by the Chinese People's Liberation Army in 1972, substantially built up in 1977, and reached 1076km, caliber 159mm, thickness of pipe 6mm, investment 2.3x108 is first.Lattice bracing wire engineering is built and is safeguarded very difficultly, and completely the spanning of river is 108, road crossing 123 places, and more than 900 kilometer pipeline (highest point height above sea level 5200m) more than height above sea level 4000m, 560km is positioned at Permafrost Area, and freezing period, reach 8 months.The lattice bracing wire is since operation in 1977, and frost heave, thaw collapse problem have caused repeatedly " revealing pipe " phenomenon.

China-Russia Crude Oil Pipeline reaches the grand celebration terminal in the south North gets boundary line, Sino-Russian Heilungkiang, Mo River initial station, and more than 960 kilometer of total length by way of two province 12, five city counties and districts, passed through 440 kilometers virgin forests, 11 big-and-middle-sized rivers, 5 wilderness areas.High south, pipeline physical features along the line north is low, and northern topographic relief is larger, is Daxing'an Mountainrange low mountain, hills and river valley geomorgy along the line, and the south is song-Nen plain, and landform is smooth open; Mo River-Jagdaqi section approximately 460km is mountain area, forest zone, Permafrost Area, and the ever frost total length is 314km approximately, wherein ices less, ices more ever frost 209km, full ice, rich ice ever frost 62km, frozen soil marsh 43km.Pipeline is faced with serious frozen swell and melt settlement disaster and threatens.

For the frozen swell and melt settlement problem that pipeline faces, unit of operation has taked positive counter-measure both at home and abroad.After the Luo Man well conduit was gone into operation in 1985, the daily monitoring plan of pipeline is being implemented as the important component part of project operation always, except weekly aircraft aerial surveillance, also a large amount of measuring instruments has been installed to record service data along the line at pipeline, and in annual September, carry out an on-site land survey when namely pipe sedimentation is maximum with the record of completing pipeline on-site inspection along the line, instrument data and the work such as site assessment of coming down the location.After 1989, the Luo Man well conduit adopts in-pipeline detector to carry out annual interior detection, to assess the motion of the unstable soil body and otherness thaw collapse to the influence degree of pipeline, along with continuous accumulation and the expansion of detection data, for the assessment of pipe technology performance provides good basis.Norman wells pipeline is the oil and gas pipes that article one is embedded in Canadian northern Permafrost Area, be in charge of and run by adding by Enbridge company, under the requirement of various regulations rules, set up one and planned monitoring system careful, strong operability, comprising the content of seven aspects such as the monitoring of frozen soil thaw collapse, pipeline detection, warpage arch detection, wrinkle detection, slope test, the detection of wood chip stratiform condition and temperature monitoring.The variation of frozen soil is also monitored in lattice trombone slide road by regular line walking, setting pressure, temperature sensor etc.

Although both at home and abroad pipeline unit of operation has taked the frozen swell and melt settlement disaster of positive measure reply permafrost region, but because the formation mechanism of frozen swell and melt settlement disaster is very complicated, and the frozen soil characteristic of different regions is different, at present both at home and abroad and there are no the monitoring technology of maturation, can monitor the frozen swell and melt settlement disaster to the impact of pipeline.For above-mentioned situation, the present invention proposes monitoring method and system based on the permafrost region pipeline of fiber grating sensing technology.

Summary of the invention

The objective of the invention is to invent a kind of high precision, high stability, cheaply based on the monitoring method of the permafrost region oil and gas pipes of fiber grating sensing technology.

The present invention proposes a kind of monitoring method of the permafrost region oil and gas pipes based on fiber grating sensing technology.It is to adopt fiber grating sensing technology, and the oil and gas pipes under frozen soil and impact thereof is carried out combined monitoring.Real-time automatic collecting, remote transmission and the automatic analysis of data have been realized.

The permafrost region oil and gas pipes monitoring method based on fiber grating sensing technology that the present invention proposes, its Contents for Monitoring comprises three parts: body displacement monitoring, permafrost region temperature monitoring, the monitoring of permafrost region water cut.Wherein, the body displacement monitoring adopts the fiber grating displacement sensor real time on-line monitoring, and the permafrost region temperature monitoring adopts the fiber-optical grating temperature sensor real time on-line monitoring, and fiber grating water content sensor real time on-line monitoring is adopted in the monitoring of permafrost region water cut.

Based on the permafrost region oil and gas pipes monitoring method monitoring method principle flow chart of fiber grating sensing technology as shown in Figure 1, monitoring method as shown in Figure 2.on the oil and gas pipes a2 of permafrost region 1 surface and a plurality of fiber-optical grating temperature sensor a3 are installed on every side, fiber-optical grating temperature sensor b4, the sets of temperature sensors that fiber-optical grating temperature sensor c5 forms, a plurality of fiber grating water content sensor a6 are installed around oil and gas pipes a2, fiber grating water content sensor b7, fiber grating water content sensor c8, the water content sensor group that fiber grating water content sensor d9 forms, in oil and gas pipes 2 one sides, a plurality of fiber grating displacement sensor a10 are installed, fiber grating displacement sensor b11, the all the sensors series welding, then guide in the monitoring station by optical cable 12, optical cable 12 is connected with photoswitch 13, photoswitch 13 is connected with fiber Bragg grating (FBG) demodulator 14, (FBG) demodulator 14 is connected with slave computer 15, the pretreated data of slave computer 15 communication module 16 via satellite transfer to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 after receiving data, satellite communication module 18 is analyzed to host computer 19 data transmission that receives and process, thereby realize the safety monitoring to the permafrost region oil and gas pipes.

the monitoring flow process of permafrost region oil and gas pipes: by a plurality of fiber-optical grating temperature sensor a3, fiber-optical grating temperature sensor b4, the sets of temperature sensors that fiber-optical grating temperature sensor c5 forms, a plurality of fiber grating water content sensor a6, fiber grating water content sensor b7, fiber grating water content sensor c8, water content sensor group and a plurality of fiber grating displacement sensor a10 that fiber grating water content sensor d9 forms, the fiber grating displacement sensor group that fiber grating displacement sensor b11 forms is respectively to the temperature of pipeline, moisture and body displacement are monitored, the signal that this monitoring obtains is gathered and pre-service by slave computer 15, pretreated data are through teletransmission and reception, to host computer 19, analyze and process by host computer 19, the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows, the hazard forecasting of permafrost region frozen swell and melt settlement, the safe early warning of oil and gas pipes.

a plurality of fiber-optical grating temperature sensor a3, fiber-optical grating temperature sensor b4, the sets of temperature sensors that fiber-optical grating temperature sensor c5 forms, a plurality of fiber grating water content sensor a6, fiber grating water content sensor b7, fiber grating water content sensor c8, water content sensor group and a plurality of fiber grating displacement sensor a10 that fiber grating water content sensor d9 forms, fiber grating displacement sensor b11 is respectively to the temperature of pipeline, moisture and body displacement are monitored, the signal that this monitoring obtains passes to photoswitch 13 through optical cable 12, reaches slave computer 15 through (FBG) demodulator 14 demodulation, and slave computer 15 calls self-editing program, controls photoswitch 13 and (FBG) demodulator 14, realizes the collection of data and data are carried out pre-service, pretreated data communication module 16 via satellite transfer to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 after receiving data, satellite communication module 18 is analyzed to host computer 19 data transmission that receives and process, the safe condition of judgement permafrost region pipeline.

The processing of data is mainly completed by software, and software flow (as shown in Figure 3) is: after beginning, and the slave computer data acquisition; The photoswitch conducting; The fiber Bragg grating (FBG) demodulator image data; The pre-service of slave computer data; Satellite communication; Does host computer judge whether data complete? if not, return to the pre-service of slave computer data, if process and judge that data exceed threshold values? if exceed, report to the police.

The pre-service of slave computer data is mainly with data based temperature, moisture and the displacement data of being converted into of the optical wavelength of fiber Bragg grating (FBG) demodulator collection, host computer is after receive data, at first with Data classification, draw out the trend map of pipeline temperature and water cut and piping displacement thereof, and three Monitoring Data merge the most at last, the steady state (SS) of judgement permafrost region and the safety case of pipeline.

Wherein:

The piping displacement monitoring method: the piping displacement monitoring method is to adopt fiber grating displacement sensor, and its structure as shown in Figure 4.Near pipeline b20, fixed bar 21 is installed, fixed bar 21 is deep into permafrost soil layer certain depth, can not be moved with assurance.Slide block 22 is installed on fixed bar 21, and slide block 22 is welding with thin expansion link 23 connected modes, and thin expansion link 23 stretches in thick expansion link 24, and the thick interior filling butter of expansion link 24 can move flexibly to guarantee thin expansion link 23.Thick expansion link 24 links together by pipe clamp 25 with pipeline b 20, and thick expansion link 24 is welding with pipe clamp 25 connected modes.Like this, when pipeline b20 is moved, the displacement meeting is passed to thick expansion link 24 by pipe clamp 25, thick expansion link 24 passes to thin expansion link 23 with displacement, thin expansion link 23 passes to slide block 22 with displacement, slide block 22 is connected with fiber grating displacement sensor c26, and wherein fiber grating displacement sensor c26 is large displacement sensor, needs when mounted to impose certain pretension.Fiber grating displacement sensor c26 is connected with data collector by cable junction box 27, realizes the monitoring of body displacement.

The piping displacement monitoring method is: fiber grating displacement sensor a10, fiber grating displacement sensor b11 to body displacement monitor; The signal that this monitoring obtains is gathered and pre-service by slave computer 15, pretreated data are through teletransmission and reception, to host computer 19, analyze and process by host computer 19, the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows; The hazard forecasting of permafrost region frozen swell and melt settlement; The safe early warning of oil and gas pipes.

Permafrost hazards causes pipeline to be subjected to displacement, and then causes the stress of pipeline to change, and is mainly the variation of axial stress, therefore, judge whether safety of pipeline, only need axis stress and the body yield stress of pipeline are compared, if exceed yield stress, report to the police.Computing formula between the displacement y of pipeline and conduit axis stress σ is as follows:

When calculating, pipeline is regarded as the beam of the semi-infinite space, according to the STRESS VARIATION of ground beam theory qualitative analysis pipeline.

According to theory of mechanics of materials, piping displacement y curve is:

$y=-\frac{2\mathrm{\Δ}}{I^3}{x}^3+\frac{3\mathrm{\Δ}}{I^2}{x}^2---\left(1\right)$

And the computing formula of moment M:

$M=-E{I}_z\frac{d^{2}y}{d{x}^2}---\left(2\right)$

Formula (1) substitution formula (2) is got:

$M=E{I}_z(\frac{6\mathrm{\Δ}}{I^2}-\frac{12\mathrm{\Δ}}{I^3}x)---\left(3\right)$

I _zBe beam section moment of inertia, I _zComputing formula be:

$I_z=\mathrm{\&pi;}{R}^3\mathrm{\&delta;}+\frac{3}{2}\mathrm{\&pi;}{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA00001602442300021.png"\; state="\{\{state\}\}">R</figure-callout>}}^2{\mathrm{\&delta;}}^2+\mathrm{\&pi;R}{\mathrm{\&delta;}}^3+\frac{1}{4}\mathrm{\&pi;}{\mathrm{\&delta;}}^4---\left(4\right)$

The axis stress σ of pipeline section:

$\mathrm{\&sigma;}=\frac{\mathrm{My}}{I_z}---\left(5\right)$

In formula: E is the tubing elastic modulus; R is internal diameter of the pipeline, and δ is pipeline wall thickness.

As mentioned above, according to the displacement y that pipeline occurs, calculate the axis stress σ of pipeline, with σ and the contrast of pipeline yield stress, the safe condition of judgement pipeline.

The permafrost region temperature monitoring method: monitoring by the temperature field, can grasp pipeline freeze thawing circle and variable condition thereof, is to judge whether pipeline exists the important evidence of freeze thawing harm and potential danger.What the permafrost region temperature monitoring adopted is fiber-optical grating temperature sensor, and its structure as shown in Figure 5.At pipeline c28 up and down, difference installing optical fibres grating temperature sensor group a29, fiber-optical grating temperature sensor group b30, fiber-optical grating temperature sensor group c31, fiber-optical grating temperature sensor group d32.Fiber-optical grating temperature sensor group a29 is comprised of several fiber-optical grating temperature sensors d33, and the quantity of fiber-optical grating temperature sensor d33 and interval can arrange according to demand.Connect by single core armored optical cable 34 between fiber-optical grating temperature sensor group b30 and fiber-optical grating temperature sensor group d32.Fiber-optical grating temperature sensor group a29, fiber-optical grating temperature sensor group b30, fiber-optical grating temperature sensor group c31, fiber-optical grating temperature sensor group d32 are connected with data collector by cable junction box 35, realize the monitoring of pipeline temperature.

The permafrost region temperature monitoring method is: by the sets of temperature sensors that fiber-optical grating temperature sensor a3, fiber-optical grating temperature sensor b4, fiber-optical grating temperature sensor c5 form, the temperature of pipeline is monitored; The signal that this monitoring obtains is gathered and pre-service by slave computer 15, pretreated data are through teletransmission and reception, to host computer 19, analyze and process by host computer 19, the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows; The hazard forecasting of permafrost region frozen swell and melt settlement; The safe early warning of oil and gas pipes.

The temperature of frozen soil layer is decided by the combined action of nature palegeology factor, and exchange heat condition between its reflection earth's crust and air sphere is one of frozen soil layer key character.We adopt the year-round average temperature bottom soil temperature year change layer to represent and contrast the frozen soil layer temperature.At first the temperature value with each position measurement is depicted as curve according to the degree of depth, order is got a little on temperature curve, with numerical value (degree of depth and temperature) the substitution formula (6) of each point, until till equation two ends equated, the temperature that draws thus was year-round average temperature T _C, the depth value that draws adds that the frost zone layer depth is the year variation depth D of soil temperature.

$\ln \frac{t_{\mathrm{cp}}}{0.1}=Z\sqrt{\frac{\mathrm{\&pi;}}{\mathrm{KT}}}---\left(6\right)$

In formula: t _cpFor annual ground temperature (℃); Z changes the degree of depth (m) in the year of soil temperature; K is soil layer thermal diffusivity (cm2s-1); T is annual period (s).

Calculate soil layer year variation depth D according to radical (6), just know pipeline to the coverage of Temperature Field of Permafrost, and then further calculate the contingent thaw collapse situation of pipeline under this impact by finite element method.

Permafrost region water cut monitoring method: the pipeline soil moisture content is one of key parameter that determines the soil physical property, directly has influence on frost heave and the thaw collapse feature of soil; Due to the water translocation effect of soil in frozen-thaw process, make the pipeline soil moisture content be in change procedure; By the monitoring of moisture field, the long term monitoring that especially changes for total water percentage of freezing soil is determined water percentage variable condition and trend, is used for the judgement of pipe and soil interaction analysis-by-synthesis and pipeline potential risk.The fiber grating water content sensor is adopted in the monitoring of permafrost region water cut, and its structure as shown in Figure 6.In the left side of pipeline d36 installing optical fibres grating water content sensor group 37, in the right side of pipeline d36 installing optical fibres grating water content sensor group 38, in the downside installing optical fibres grating water content sensor group 39 of pipeline d36.Water content sensor group 37 is comprised of several fiber grating water content sensors 40, and the quantity of fiber grating water content sensor 40 and interval can arrange according to demand.Connect by single core armored optical cable 41 between water content sensor group 38 and water content sensor group 39.Sets of temperature sensors 37,38,39 is connected with data collector by cable junction box 42, realizes the monitoring of pipeline water cut.

Permafrost region water cut monitoring method is: by the water content sensor group that fiber grating water content sensor b7, fiber grating water content sensor c8, fiber grating water content sensor d9 form, the moisture of pipeline is monitored; The signal that this monitoring obtains is gathered and pre-service by slave computer 15, pretreated data are through teletransmission and reception, to host computer 19, analyze and process by host computer 19, the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows; The hazard forecasting of permafrost region frozen swell and melt settlement; The safe early warning of oil and gas pipes.

When the frost heave disaster occured, the water cut in frozen soil changed.Be not that all soil bodys all can produce frost heave, only have when the foundation soil water cut surpasses the certain limit value to produce frost heave.Usually this Atterberg limits is called initial frost heaving amount W ₀, the plastic limit water cut of soil is W _p, the natural aqueous value of soil that water content sensor is measured is W, when W satisfies following formula, strong frost heave will occur in the soil body.

W _p+5＜W≤W _p+15 (7)

In formula: W _pBe the plastic limit of soil water cut, can obtain by experiment.

With the measured value W substitution following formula of water content sensor, when satisfying condition, system becomes can automatic alarm.

This permafrost region oil and gas pipes monitoring method system for use in carrying

The permafrost region oil and gas pipes monitoring system of design as shown in Figure 7 according to the method described above.This system is divided into on-site data gathering transmission subsystem and data analysis display subsystem, specifically comprises fiber grating displacement sensor group, fiber-optical grating temperature sensor group, fiber grating water content sensor group, field monitoring station, remote monitoring center.

The overall formation of permafrost region oil and gas pipes monitoring system as shown in Figure 2.installing optical fibres grating temperature sensor a3 on oil and gas pipes 2 surface of permafrost region 1 and on every side, fiber-optical grating temperature sensor b4, the sets of temperature sensors that fiber-optical grating temperature sensor c5 forms, installing optical fibres grating water content sensor a6 around oil and gas pipes 2, fiber grating water content sensor b7, fiber grating water content sensor c8, the water content sensor group that fiber grating water content sensor d9 forms, in oil and gas pipes 2 one sides, installing optical fibres grating displacement sensor a10, fiber grating displacement sensor b11, the all the sensors series welding, then guide in the monitoring station by optical cable 12, optical cable 12 is connected with photoswitch 13, photoswitch 13 is connected with fiber Bragg grating (FBG) demodulator 14, fiber Bragg grating (FBG) demodulator 14 is connected with slave computer 15, the pretreated data of slave computer 15 communication module 16 via satellite transfer to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 after receiving data, satellite communication module 18 is analyzed to host computer 19 data transmission that receives and process, thereby realize the safety monitoring to the permafrost region oil and gas pipes.

fiber-optical grating temperature sensor a3, fiber-optical grating temperature sensor b4, fiber-optical grating temperature sensor c5, fiber grating water content sensor a6, fiber grating water content sensor b7, fiber grating water content sensor c8, fiber grating water content sensor d9, fiber grating displacement sensor a10, fiber grating displacement sensor b11 is respectively with the temperature of pipeline, moisture and body displacement signal pass to photoswitch 13 through optical cable 12, reach slave computer 15 through fiber Bragg grating (FBG) demodulator 14 demodulation, slave computer 15 calls self-editing program, control photoswitch 13 and fiber Bragg grating (FBG) demodulator 14, realize the collection of data and data are carried out pre-service, pretreated data communication module 16 via satellite transfer to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 after receiving data, satellite communication module 18 is analyzed to host computer 19 data transmission that receives and process, the safe condition of judgement permafrost region pipeline.The processing of data is mainly completed by software, and software flow as shown in Figure 3.The pre-service of slave computer data is mainly with data based temperature, moisture and the displacement data of being converted into of the optical wavelength of fiber Bragg grating (FBG) demodulator collection, host computer is after receive data, at first with Data classification, draw out the trend map of pipeline temperature and water cut and piping displacement thereof, and three Monitoring Data merge the most at last, the steady state (SS) of judgement permafrost region and the safety case of pipeline.

The theory diagram of permafrost region oil and gas pipes monitoring system as shown in Figure 7, it is divided into on-site data gathering transmission subsystem and data analysis display subsystem.Corresponding to the monitoring method of permafrost region oil and gas pipes, system comprises again displacement monitor, device for detecting temperature and water cut monitoring device three parts.The composition of on-site data gathering transmission subsystem is: the output of fiber grating displacement sensor, fiber-optical grating temperature sensor and fiber grating water content sensor connects the input of photoswitch, the output of photoswitch connects the input of fiber Bragg grating (FBG) demodulator, fiber Bragg grating (FBG) demodulator output connects the input of slave computer, and slave computer output connects satellite communication module.The on-site data gathering transmission subsystem is communicated by letter with the data analysis display subsystem by low-orbit satellite.The composition of data analysis display subsystem is: satellite communication module output connects the input of host computer, and host computer output has the permafrost region temperature field dynamically to show, the permafrost region piping displacement dynamically shows, permafrost region moisture field dynamically shows.

the electric principle of this system as shown in Figure 8, the fiber-optical grating temperature sensor group, the FC joint of fiber grating water content sensor group and fiber grating displacement sensor group respectively with the FC input port 1 of photoswitch, FC input port 2, FC input port 3 connects, the R232 port of photoswitch connects the R232 port one of slave computer, the FC output port of photoswitch connects the FC input port of fiber Bragg grating (FBG) demodulator, the LAN port of fiber Bragg grating (FBG) demodulator connects the LAN port of slave computer, the VGA of slave computer is connected with the VGA of display, the R232 port 2 of slave computer connects the R232 port of satellite communication module, satellite communication module transfers data to low-orbit satellite, low-orbit satellite forwards the data to another satellite communication module in real time, this satellite communication module with receive data by the R232 port of R232 port transmission to host computer, host computer exports display to by the VGA port after data analysis is processed.

The fiber-optic grating sensor signal of three types through photoswitch 13 one by one conducting transfer to fiber Bragg grating (FBG) demodulator 14, the centre wavelength that fiber Bragg grating (FBG) demodulator 14 demodulates each fiber-optic grating sensor transfers to slave computer 15, and the cycle of photoswitch 13 Continuity signals is controlled by slave computer 15.15 pairs of data of slave computer are carried out pre-service, and the data after processing are defeated by satellite communication module 16, satellite communication module 16 transfers data to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 in real time, satellite communication module 18 transfers to host computer with receive data, host computer carries out analyzing and processing by self-programmed software to data, is shown by display.

Fiber-optical grating temperature sensor, fiber grating displacement sensor and fiber grating water content sensor are develops sensor voluntarily.Fiber-optical grating temperature sensor adopts the structure of double-layer pipe, has not only improved the sensitivity of sensor, and has played protective effect.Fiber grating displacement sensor adopts temp. compensation type, has got rid of the impact of temperature on measurement result, has improved the measuring accuracy of displacement transducer.The fiber grating water content sensor utilizes soil water suction and soil moisture content to have the principle of corresponding relation to develop, the fiber grating water content sensor is comprised of vitrified-clay pipe and vacuum box, vitrified-clay pipe is sensitive element, after vitrified-clay pipe is put into soil, the liquid water content of soil can cause the variation of vacuum box pressure, and the variation of vacuum box pressure can cause the variation of optic fiber grating wavelength, and then can go out according to the change calculations of optic fiber grating wavelength the liquid water content of soil.

Except the foregoing circuit part, the construction method of the fiber-optical grating temperature sensor group of permafrost region oil and gas pipes monitoring system, fiber grating water content sensor group and fiber grating displacement sensor group is:

The construction method of pipeline fiber grating displacement sensor group is as shown in Figure 4: near pipeline b20, fixed bar 21 is installed, fixed bar 21 is deep into permafrost soil layer certain depth, can not be moved guaranteeing.Slide block 22 is installed on fixed bar 21, and slide block 22 is welding with thin expansion link 23 connected modes, and thin expansion link 23 stretches in thick expansion link 24, and the thick interior filling butter of expansion link 24 can move flexibly to guarantee thin expansion link 23.Thick expansion link 24 links together by pipe clamp 25 with pipeline b20, and thick expansion link 24 is welding with pipe clamp 25 connected modes.Like this, when pipeline b20 is moved, the displacement meeting is passed to thick expansion link 24 by pipe clamp 25, thick expansion link 24 passes to thin expansion link 23 with displacement, thin expansion link 23 passes to slide block 22 with displacement, slide block 22 is connected with fiber grating displacement sensor 26, and wherein fiber grating displacement sensor 26 is large displacement sensor, needs when mounted to impose certain pretension.Fiber grating displacement sensor 26 is connected with data collector by cable junction box 27, realizes the monitoring of body displacement.

The construction method of permafrost region fiber-optical grating temperature sensor group is as shown in Figure 5: at pipeline c28 up and down, and installing optical fibres grating temperature sensor group a29, fiber-optical grating temperature sensor group b30, fiber-optical grating temperature sensor group c31, fiber-optical grating temperature sensor group d32 respectively.Sets of temperature sensors 29 is comprised of several fiber-optical grating temperature sensors 33, and the quantity of fiber-optical grating temperature sensor 33 and interval can arrange according to demand.Connect by single core armored optical cable 34 between sets of temperature sensors 30 and sets of temperature sensors 32.Fiber-optical grating temperature sensor group a29, fiber-optical grating temperature sensor group b30, fiber-optical grating temperature sensor group c31, fiber-optical grating temperature sensor group d32 are connected with data collector by cable junction box 35, realize the monitoring of pipeline temperature.

The construction method of permafrost region fiber grating water content sensor group is as shown in Figure 6: in the left side of pipeline d36 installing optical fibres grating water content sensor group 37, in the right side of pipeline d36 installing optical fibres grating water content sensor group 38, in the downside installing optical fibres grating water content sensor group 39 of pipeline d36.Water content sensor group 37 is comprised of several fiber grating water content sensors 40, and the quantity of fiber grating water content sensor 40 and interval can arrange according to demand.Connect by single core armored optical cable 41 between water content sensor group 38 and water content sensor group 39.Fiber grating water content sensor group a37, fiber grating water content sensor group b38, fiber grating water content sensor group c39 are connected with data collector by cable junction box 42, realize the monitoring of pipeline water cut.

The advantage of this method shows:

(1) propose oil and gas pipes under permafrost region and impact thereof is carried out the method for combined monitoring, disclosed frozen soil effect lower tube body stress characteristic and body and the interactional feature of frozen soil; Carry out the safe early warning of the lower oil and gas pipes of frozen soil impact with many indexs;

(2) fiber grating sensing technology is applied to permafrost region pipeline monitoring, this technology is anti-interference, corrosion-resistant, it is with the obvious advantage to be easy to networking etc.; This technology is easy to realize automatic real time on-line monitoring, and cost is lower;

(3) piping displacement monitoring, according to the feature of pipeline place permafrost region, in pipeline one side, fixed bar is installed, adopt the connected mode of expansion link that pipeline and fixed bar are linked together, installing optical fibres grating displacement sensor on fixed bar, the displacement situation of monitoring pipeline; This monitoring method has been avoided distinguishing by the excavation pipeline whether pipeline is subjected to displacement, the selection of carrying out protection works opportunitys for the permafrost region oil and gas pipes provides effective foundation, reduced the blindness of protection works and saved the conduit running cost, also guaranteed the security of operation of pipeline simultaneously, the construction when having reduced the excavation checking is dangerous;

(4) permafrost region temperature monitoring, adopt fiber-optical grating temperature sensor monitoring permafrost region temperature, have the advantage of wavelength-division multiplex due to fiber grating sensing technology, an optical fiber a plurality of fiber-optical grating temperature sensors of can connecting, avoid complicated cabling, also saved cost simultaneously.

Description of drawings

Fig. 1 adopts permafrost region oil and gas pipes monitoring method principle flow chart

Fig. 2 permafrost region oil and gas pipes monitoring method figure

Fig. 3 software flow pattern

Fig. 4 piping displacement monitoring device figure

Fig. 5 permafrost region device for detecting temperature figure

Fig. 6 permafrost region water cut monitoring device figure

Fig. 7 permafrost region oil and gas pipes Fundamentals of Supervisory Systems block diagram

Fig. 8 permafrost region oil and gas pipes monitoring system electrical schematic diagram

1-permafrost region 2-pipeline a wherein

3-fiber-optical grating temperature sensor a 4-fiber-optical grating temperature sensor b

5-fiber-optical grating temperature sensor c 6-fiber grating water content sensor a

7-fiber grating water content sensor b 8-fiber grating water content sensor c

9-fiber grating water content sensor d 10-fiber grating displacement sensor a

11-fiber grating displacement sensor b 12-optical cable

13-photoswitch 14-fiber Bragg grating (FBG) demodulator

15-slave computer 16-satellite communication module a

17-low-orbit satellite 18-satellite communication module b

19-host computer 20-pipeline b

21-fixed bar 22-slide block

The thick expansion link of the thin expansion link 24-of 23-

25-pipe clamp 26-fiber grating displacement sensor c

27-cable junction box a 28-pipeline c

29-fiber-optical grating temperature sensor group a 30-fiber-optical grating temperature sensor group b

31-fiber-optical grating temperature sensor group c 32-fiber-optical grating temperature sensor group d

The single core armored optical cable of 33-fiber-optical grating temperature sensor d 34-a

35-cable junction box b 36-pipeline d

37-fiber grating water content sensor group a 38-fiber grating water content sensor group b

39-fiber grating water content sensor group c 40-fiber grating water content sensor e

The single core armored optical cable of 41-b 42-cable junction box c

Embodiment

Embodiment. this example is a kind of test method, and tests for the permafrost region of the full ice of rich ice at frost zone thickness 2m, frozen soil type, buried depth of pipeline 2m wherein, pipe diameter is that 813mm, wall thickness are 10mm, grade of steel X65.

The overall formation of permafrost region oil and gas pipes monitoring system as shown in Figure 2; Theory diagram as shown in Figure 7.installing optical fibres grating temperature sensor 3 on oil and gas pipes 2 surface of permafrost region 1 and on every side, 4, 5 sets of temperature sensors that form, installing optical fibres grating water content sensor 6 around oil and gas pipes 2, 7, 8, the 9 water content sensor groups that form, in oil and gas pipes 2 one sides, installing optical fibres grating displacement sensor 10, 11, the all the sensors series welding, then guide in the monitoring station by optical cable 12, optical cable 12 is connected with photoswitch 13, photoswitch 13 is connected with fiber Bragg grating (FBG) demodulator 14, fiber Bragg grating (FBG) demodulator 14 is connected with slave computer 15, the pretreated data of slave computer 15 communication module 16 via satellite transfer to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 after receiving data, satellite communication module 18 is analyzed to host computer 19 data transmission that receives and process, thereby realize the safety monitoring to the permafrost region oil and gas pipes.

the electric principle of this example as shown in Figure 8, the fiber-optical grating temperature sensor group, the FC joint of fiber grating water content sensor group and fiber grating displacement sensor group respectively with the FC input port 1 of photoswitch, FC input port 2, FC input port 3 connects, the R232 port of photoswitch connects the R232 port one of slave computer, the FC output port of photoswitch connects the FC input port of fiber Bragg grating (FBG) demodulator, the LAN port of fiber Bragg grating (FBG) demodulator connects the LAN port of slave computer, the VGA of slave computer is connected with the VGA of display, the R232 port 2 of slave computer connects the R232 port of satellite communication module, satellite communication module transfers data to low-orbit satellite, low-orbit satellite forwards the data to another satellite communication module in real time, this satellite communication module with receive data by the R232 port of R232 port transmission to host computer, host computer exports display to by the VGA port after data analysis is processed.

The fiber-optic grating sensor signal of three types through photoswitch 13 one by one conducting transfer to fiber Bragg grating (FBG) demodulator 14, the centre wavelength that fiber Bragg grating (FBG) demodulator 14 demodulates each fiber-optic grating sensor transfers to slave computer 15, and the cycle of photoswitch 13 Continuity signals is controlled by slave computer 15.15 pairs of data of slave computer are carried out pre-service, and the data after processing are defeated by satellite communication module 16, satellite communication module 16 transfers data to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 in real time, satellite communication module 18 transfers to host computer with receive data, host computer carries out analyzing and processing by self-programmed software to data, is shown by display.

Wherein:

Fiber-optical grating temperature sensor: the temperature sensor of selecting the designed, designed encapsulation;

Fiber grating displacement sensor: the displacement transducer of selecting the designed, designed encapsulation;

Fiber grating water content sensor: the water content sensor of selecting the designed, designed encapsulation;

Optical cable: select middle day scientific and technological GYTA-12B1;

Photoswitch: select the grand scientific and technological SUM-FSW of light;

Fiber Bragg grating (FBG) demodulator: select SM130;

Slave computer and program: select and grind magnificent IPC-610, program is self-editing;

Telstar module: the ST2500 of STELLAR company;

Host computer and program: select and grind magnificent IPC-610, program is self-editing.

The monitoring method process flow diagram as shown in Figure 1, monitoring method is as shown in Figure 2.installing optical fibres grating temperature sensor a3 on the oil and gas pipes a2 of permafrost region 1 surface and on every side, fiber-optical grating temperature sensor b4, the sets of temperature sensors that fiber-optical grating temperature sensor c5 forms, installing optical fibres grating water content sensor a6 around oil and gas pipes a2, fiber grating water content sensor b7, fiber grating water content sensor c8, the water content sensor group that fiber grating water content sensor d9 forms, in oil and gas pipes 2 one sides, installing optical fibres grating displacement sensor a10, fiber grating displacement sensor b11, the all the sensors series welding, then guide in the monitoring station by optical cable 12, optical cable 12 is connected with photoswitch 13, photoswitch 13 is connected with fiber Bragg grating (FBG) demodulator 14, (FBG) demodulator 14 is connected with slave computer 15, the pretreated data of slave computer 15 communication module 16 via satellite transfer to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 after receiving data, satellite communication module 18 is analyzed to host computer 19 data transmission that receives and process, thereby realize the safety monitoring to the permafrost region oil and gas pipes.

the monitoring flow process of permafrost region oil and gas pipes: by fiber-optical grating temperature sensor a3, fiber-optical grating temperature sensor b4, the sets of temperature sensors that fiber-optical grating temperature sensor c5 forms, fiber grating water content sensor a6, fiber grating water content sensor b7, fiber grating water content sensor c8, water content sensor group and fiber grating displacement sensor a10 that fiber grating water content sensor d9 forms, fiber grating displacement sensor b11 is respectively to the temperature of pipeline, moisture and body displacement are monitored, the signal that this monitoring obtains is gathered and pre-service by slave computer 15, pretreated data are through teletransmission and reception, to host computer 19, analyze and process by host computer 19, the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows, the hazard forecasting of permafrost region frozen swell and melt settlement, the safe early warning of oil and gas pipes.

Water content sensor group and fiber grating displacement sensor a10, fiber grating displacement sensor b11 that the sets of temperature sensors that fiber-optical grating temperature sensor a3, fiber-optical grating temperature sensor b4, fiber-optical grating temperature sensor c5 form, fiber grating water content sensor a6, fiber grating water content sensor b7, fiber grating water content sensor c8, fiber grating water content sensor d9 form monitor temperature, moisture and the body displacement of pipeline respectively; The signal that this monitoring obtains passes to photoswitch 13 through optical cable 12, reaches slave computer 15 through (FBG) demodulator 14 demodulation, and slave computer 15 calls self-editing program, controls photoswitch 13 and (FBG) demodulator 14, realizes the collection of data and data are carried out pre-service; Pretreated data communication module 16 via satellite transfer to low-orbit satellite 17, low-orbit satellite 17 forwards the data to satellite communication module 18 after receiving data, satellite communication module 18 is analyzed to host computer 19 data transmission that receives and process, the safe condition of judgement permafrost region pipeline.

The processing of data is mainly completed by software, and software flow (as shown in Figure 3) is: after beginning, and the slave computer data acquisition; The photoswitch conducting; The fiber Bragg grating (FBG) demodulator image data; The pre-service of slave computer data; Satellite communication; Does host computer judge whether data complete? if not, return to the pre-service of slave computer data, if process and judge that data exceed threshold values? if exceed, report to the police.

The pre-service of slave computer data is mainly with data based temperature, moisture and the displacement data of being converted into of the optical wavelength of fiber Bragg grating (FBG) demodulator collection, host computer is after receive data, at first with Data classification, draw out the trend map of pipeline temperature and water cut and piping displacement thereof, and three Monitoring Data merge the most at last, the steady state (SS) of judgement permafrost region and the safety case of pipeline.

When monitoring, temperature and moisture need long term monitoring with said method, and according to the analysis to long term monitoring data, total junction temperature and moisture variable condition and trend are used for the judgement of pipe and soil interaction analysis-by-synthesis and pipeline potential risk.Displacement monitoring can reflect the safe condition of pipeline in real time, when permafrost region generation frozen swell and melt settlement disaster, the pipeline that is embedded in soil body below is subject to the frozen soil effect and is subjected to displacement, the displacement of pipeline passes to fiber grating displacement sensor by displacement monitor, the data of displacement transducer are transferred to host computer and show in real time after slave computer is processed, the program of host computer is done contrast with piping displacement amount and alarm threshold value automatically, exceeds the threshold value alarm.

Through monitoring for a long time, this example is easy to build monitoring system, is easy to realize real-time automatic collecting analysis and the long-range issue of permafrost region and pipeline combined monitoring data, long-range real-time automatic alarm.Avoided loaded down with trivial details artificial image data, improved the precision of early warning, reduced time of fire alarming, can also accurately locate place of alarm simultaneously, this to the pipeline emergency measure take most important.

Claims (4)

1. permafrost region oil and gas pipes monitoring method, it is characterized in that on the oil and gas pipes a (2) of permafrost region (1) surface and a plurality of fiber-optical grating temperature sensor a (3) are installed on every side, fiber-optical grating temperature sensor b (4), the sets of temperature sensors that fiber-optical grating temperature sensor c (5) forms, at oil and gas pipes a (2), a plurality of fiber grating water content sensor a (6) are installed on every side, fiber grating water content sensor b (7), fiber grating water content sensor c (8), the water content sensor group that fiber grating water content sensor d (9) forms, in oil and gas pipes (2) one sides, a plurality of fiber grating displacement sensor a (10) are installed, fiber grating displacement sensor b (11), the all the sensors series welding, then guide in the monitoring station by optical cable (12), optical cable (12) is connected with photoswitch (13), photoswitch (13) is connected with fiber Bragg grating (FBG) demodulator (14), (FBG) demodulator (14) is connected with slave computer (15), the pretreated data of slave computer (15) communication module (16) via satellite transfer to low-orbit satellite (17), low-orbit satellite (17) forwards the data to satellite communication module (18) after receiving data, satellite communication module (18) is analyzed to host computer (19) data transmission that receives and process,

the monitoring flow process of permafrost region oil and gas pipes: a plurality of fiber-optical grating temperature sensor a (3), fiber-optical grating temperature sensor b (4), the sets of temperature sensors that fiber-optical grating temperature sensor c (5) forms, a plurality of fiber grating water content sensor a (6), fiber grating water content sensor b (7), fiber grating water content sensor c (8), water content sensor group and a plurality of fiber grating displacement sensor a (10) that fiber grating water content sensor d (9) forms, the fiber grating displacement sensor group that fiber grating displacement sensor b (11) forms is respectively to the temperature of pipeline, moisture and body displacement are monitored, the signal that this monitoring obtains passes to photoswitch (13) through optical cable (12), reach slave computer (15) through (FBG) demodulator (14) demodulation, slave computer (15) calls self-editing program, control photoswitch (13) and (FBG) demodulator (14), realize the collection of data and data are carried out pre-service, pretreated data communication module (16) via satellite transfer to low-orbit satellite (17), low-orbit satellite (17) forwards the data to satellite communication module (18) after receiving data, satellite communication module (18) is analyzed to host computer (19) data transmission that receives and process, the safe condition of judgement permafrost region pipeline is to the safe early warning of the hazard forecasting of permafrost region frozen swell and melt settlement, oil and gas pipes,

The processing of data is mainly completed by software, and its flow process is: after beginning, and the slave computer data acquisition; The photoswitch conducting; The fiber Bragg grating (FBG) demodulator image data; The pre-service of slave computer data; Satellite communication; Does host computer judge whether data complete? if not, return to the pre-service of slave computer data, if process and judge that data exceed threshold values? if exceed, report to the police.

2. a kind of permafrost region oil and gas pipes monitoring method according to claim 1 is characterized in that described piping displacement monitoring method is: a plurality of fiber grating displacement sensor a (10), fiber grating displacement sensor b (11) to body displacement monitor; The signal that this monitoring obtains is gathered and pre-service by slave computer (15), pretreated data are through teletransmission and reception, to host computer (19), analyze and process by host computer (19), the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows; Safe early warning to the hazard forecasting of permafrost region frozen swell and melt settlement, oil and gas pipes;

Judge whether safety of pipeline, only need axis stress and the body yield stress of pipeline are compared, if exceed yield stress, report to the police; Computing formula between the displacement y of pipeline and conduit axis stress σ is as follows:

When calculating, pipeline is regarded as the beam of the semi-infinite space, according to the STRESS VARIATION of ground beam theory qualitative analysis pipeline.

Piping displacement y curve is:

$y=-\frac{2\mathrm{\&Delta;}}{I^3}{x}^3+\frac{3\mathrm{\&Delta;}}{I^2}{x}^2---\left(1\right)$

The computing formula of moment M:

$M=-E{I}_z\frac{d^{2}y}{d{x}^2}---\left(2\right)$

Formula (1) substitution formula (2) is got:

$M=E{I}_z(\frac{6\mathrm{\&Delta;}}{I^2}-\frac{12\mathrm{\&Delta;}}{I^3}x)---\left(3\right)$

I _zBe beam section moment of inertia, I _zComputing formula be:

$I_z=\mathrm{\&pi;}{R}^3\mathrm{\&delta;}+\frac{3}{2}\mathrm{\&pi;}{R}^2{\mathrm{\&delta;}}^2+\mathrm{\&pi;R}{\mathrm{\&delta;}}^3+\frac{1}{4}\mathrm{\&pi;}{\mathrm{\&delta;}}^4---\left(4\right)$

The axis stress σ of pipeline section:

$\mathrm{\&sigma;}=\frac{\mathrm{My}}{I_z}---\left(5\right)$

In formula: E is the tubing elastic modulus; R is internal diameter of the pipeline, and δ is pipeline wall thickness;

According to the displacement y that pipeline occurs, calculate the axis stress σ of pipeline, with σ and the contrast of pipeline yield stress, the safe condition of judgement pipeline.

3. a kind of permafrost region oil and gas pipes monitoring method according to claim 1, is characterized in that described permafrost region temperature monitoring method is: by the sets of temperature sensors that a plurality of fiber-optical grating temperature sensor a (3), fiber-optical grating temperature sensor b (4), fiber-optical grating temperature sensor c (5) form, the temperature of pipeline is monitored; The signal that this monitoring obtains is gathered and pre-service by slave computer (15), pretreated data are through teletransmission and reception, to host computer (19), analyze and process by host computer (19), the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows; The hazard forecasting of permafrost region frozen swell and melt settlement; The safe early warning of oil and gas pipes;

Adopt the year-round average temperature of soil temperature year change layer bottom to represent and contrast the frozen soil layer temperature; At first the temperature value with each position measurement is depicted as curve according to the degree of depth, and order is got a little on temperature curve, with the degree of depth and the Temperature numerical substitution formula (6) of each point, until till equation two ends equated, the temperature that draws thus was year-round average temperature T _C, the depth value that draws adds that the frost zone layer depth is the year variation depth D of soil temperature;

$\ln \frac{t_{\mathrm{cp}}}{0.1}=Z\sqrt{\frac{\mathrm{\&pi;}}{\mathrm{KT}}}---\left(6\right)$

In formula: t _cpFor annual ground temperature (℃); Z changes the degree of depth (m) in the year of soil temperature; K is soil layer thermal diffusivity (cm2s-1); T is annual period (s);

Calculate soil layer year variation depth D according to radical (6), learn pipeline to the coverage of Temperature Field of Permafrost, and then further calculate the contingent thaw collapse situation of pipeline under this impact by finite element method.

4. a kind of permafrost region oil and gas pipes monitoring method according to claim 1, is characterized in that described permafrost region water cut monitoring method is: by the water content sensor group that a plurality of fiber grating water content sensor b (7), fiber grating water content sensor c (8), fiber grating water content sensor d (9) form, the moisture of pipeline is monitored; The signal that this monitoring obtains is gathered and pre-service by slave computer (15), pretreated data are through teletransmission and reception, to host computer (19), analyze and process by host computer (19), the safe condition of judgement permafrost region pipeline carries out that permafrost region pipe temperature field dynamically shows, the displacement of permafrost region body dynamically shows, permafrost region Pipeline Water branch dynamically shows; Safe early warning to the hazard forecasting of permafrost region frozen swell and melt settlement, oil and gas pipes;

When the frost heave disaster occurs, only have when the foundation soil water cut surpasses the certain limit value to produce frost heave; Usually this Atterberg limits is called initial frost heaving amount W ₀, the plastic limit water cut of soil is W _p, the natural aqueous value of soil that water content sensor is measured is W, when W satisfies following formula, strong frost heave will occur in the soil body;

W _p+5＜W≤W _p+15 (7)

In formula: W _pBe the plastic limit of soil water cut, can obtain by experiment.

With the measured value W substitution following formula of water content sensor, when satisfying condition, system just can automatic alarm.

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