CN102121860A - Corrugated diaphragm type pipe external pressure sensor, oil-water well casing external pressure monitoring device and method - Google Patents

Abstract

The invention discloses a corrugated diaphragm type pipe external pressure sensor, an oil-water well casing external pressure monitoring device and an oil-water well casing external pressure monitoring method, which belong to the technical field of fiber optical sensing and aim to solve the problems that the conventional pressure monitoring of an oil-water well casing only can be performed at a single point in the casing and that real-time online monitoring cannot be performed. An optical fiber and a fiber Bragg grating are arranged in a central cavity of a corrugated diaphragm type pipe external pressure sensor substrate, and are packaged with fiber reinforced plastic intellectual ribs. The two ends of the substrate fixedly clamp the intellectual ribs by expansion bolts respectively. A contact terminal hole is reserved in the center of the sidewall of the substrate. A pressure contact terminal is arranged in the contact hole. Two contacts of the pressure contact terminal are connected to the FRP intellectual ribs in a contacting way, and longitudinally stridden at the two ends of the fiber Bragg grating. A gap between the internal corrugated surface of a corrugated diaphragm at an orifice of the contact terminal hole and the surface of the outer wall of the pressure contact terminal is equal. The corrugated diaphragm type pipe external pressure sensor is adopted in both the oil-water well casing external pressure monitoring device and the oil-water well casing external pressure monitoring method. The corrugated diaphragm type pipe external pressure sensor, the oil-water well casing external pressure monitoring device and the oil-water well casing external pressure monitoring method are used for pressure monitoring.

Description

Convoluted diaphragm-type pipe external pressure sensor and Casing Failure external pressure monitoring device and method

Technical field

The present invention relates to a kind of Convoluted diaphragm-type pipe external pressure sensor and Casing Failure external pressure monitoring device and method, belong to technical field of optical fiber sensing.

Background technology

Casing damage in oil-water well not only can be brought economically loss to the oil field, also can bring adverse effect to the application of oilfield development program and the measure of raising recovery ratio, thereby directly have influence on the exploitation of oil and the development in oil field, at present, the problem of casing damage in oil-water well has become China's oil field problem demanding prompt solution, in order to prevent and slow down the damage of Casing Failure in advance, sleeve pipe is managed external pressure monitor significant.

At present, the most test modes that adopt mechanical type and electronics memory-type of the test of oil-water well down-hole pressure, this mode need be gone into the well by steel wire suspention coherent detection equipment behind the oil-water well closing well, again equipment is taken out after test a period of time, can not accomplish real-time well logging, data interpretation seriously lags behind the well logging process, and influences the ordinary production of oil well; It can only carry out the monitoring of single-point pipe internal pressure in sleeve pipe simultaneously.Relevant metering system also has the permanent type electronic metering equipment, be about to instrument and forever be installed in the down-hole, draw signal to ground by cable, the equipment that this metering system adopts can not take out easily, measuring equipment is prone to drift, problem such as aging under the condition of down-hole High Temperature High Pressure, make measurement data inaccurate, plant maintenance and calibration be difficulty very.

Summary of the invention

The objective of the invention is for the pressure monitoring that solves existing Casing Failure can only be in pipe single-point carry out and problem that can't real time on-line monitoring, a kind of Convoluted diaphragm-type pipe external pressure sensor and Casing Failure external pressure monitoring device and method are provided.

Convoluted diaphragm-type pipe external pressure sensor of the present invention, described Convoluted diaphragm-type pipe external pressure sensor comprise convoluted diaphragm, pressure contact, FRP intelligence muscle, Fiber Bragg Grating FBG, optical fiber, pedestal and cinch bolt,

Optical fiber and Fiber Bragg Grating FBG are set in the center cavity of pedestal, Fiber Bragg Grating FBG is positioned at the center of described center cavity, the two ends of Fiber Bragg Grating FBG are provided with optical fiber respectively, all encapsulate FRP intelligence muscle on the outer round surface of optical fiber and Fiber Bragg Grating FBG, FRP intelligence muscle two fixed ends in pedestal, the two ends of pedestal respectively by cinch bolt with intelligent muscle clamping

A sidewall center of pedestal has a contact apertures, another lateral wall of the pedestal relative with this sidewall is a stationary plane, the pressure contact is set in the described contact apertures, two ends with the optical fiber axially parallel on the pressure contact have a contact respectively, described two contacts touch on FRP intelligence muscle, two contacts are vertically across the two ends of Fiber Bragg Grating FBG, the port of described contact apertures is provided with convoluted diaphragm, and the interior corrugated surface of convoluted diaphragm equates with gap between the outer wall surface of pressure contact.

Casing Failure external pressure monitoring device based on said apparatus of the present invention, it comprises Convoluted diaphragm-type pipe external pressure sensor, laser instrument, photo-coupler and data acquisition processing circuit,

The light signal input end of described Convoluted diaphragm-type pipe external pressure sensor connects the light signal output end of photo-coupler, and the light signal input end of photo-coupler connects the light signal output end of laser instrument; The light signal output end of described Convoluted diaphragm-type pipe external pressure sensor connects the light signal input end of data acquisition processing circuit.

The method of realization Casing Failure external pressure monitoring of the present invention, realize that the process of pressure monitoring is:

Step 1: one or more Convoluted diaphragm-type pipe external pressure sensors are fixed on described Casing Failure needs the monitoring pressure place outward, the stationary plane of described Convoluted diaphragm-type pipe external pressure sensor is closely contacted with the Casing Failure outer wall, will be installed on by the FBG (FBG) demodulator that laser instrument, photo-coupler and data acquisition processing circuit are formed on the ground at described oil-water well well head place;

Step 2: the control Laser Output Beam, make described light beam export optical fiber to, and transfer to Fiber Bragg Grating FBG through photo-coupler, gather the light signal of optical fiber output by data acquisition processing circuit, calculate and obtain the pressure that described Casing Failure is subjected to outward.

Advantage of the present invention is: the present invention is simple in structure, is easy to make; Lay Convoluted diaphragm-type pipe external pressure sensor by the position that outside Casing Failure, needs monitoring pressure, realized the pipe external pressure monitoring of quasi-distributed Casing Failure; Described Convoluted diaphragm-type pipe external pressure transducer sensitivity coefficient height can reach the Practical Performance requirement; And the inventive method has realized real-time online measuring Casing Failure being carried out do not influence the ordinary production of oil well in the process of pressure monitoring.

After the Casing Failure external pressure affacts convoluted diaphragm, the displacement that convoluted diaphragm produces pressure direction drives pressure contact press-bending FRP intelligence muscle, the bending of FRP intelligence muscle makes the Fiber Bragg Grating FBG in the FRP intelligence muscle deform, cause the variation of grating centre wavelength, by the variation of grating centre wavelength in the data acquisition processing circuit collection reflectance spectrum, calculate grating center wavelength variation and the relation of managing the external pressure size of obtaining.

Description of drawings

Fig. 1 is a Convoluted diaphragm-type pipe external pressure sensor of the present invention when measuring the Casing Failure external pressure and the relative position synoptic diagram of tested sleeve pipe;

Fig. 2 is the structural representation of Convoluted diaphragm-type pipe external pressure sensor;

Fig. 3 is the cross-sectional view of Fiber Bragg Grating FBG encapsulation FRP intelligence muscle;

Fig. 4 is the cross-sectional view of optical fiber.

Embodiment

Embodiment one: present embodiment is described below in conjunction with Fig. 2, the described Convoluted diaphragm-type pipe of present embodiment external pressure sensor, it is characterized in that: described Convoluted diaphragm-type pipe external pressure sensor 4 comprises convoluted diaphragm 4-1, pressure contact 4-2, FRP intelligence muscle 4-3, Fiber Bragg Grating FBG 4-4, optical fiber 4-5, pedestal 4-6 and cinch bolt 4-7

Optical fiber 4-5 and Fiber Bragg Grating FBG 4-4 are set in the center cavity of pedestal 4-6, Fiber Bragg Grating FBG 4-4 is positioned at the center of described center cavity, the two ends of Fiber Bragg Grating FBG 4-4 are provided with optical fiber 4-5 respectively, all encapsulate FRP intelligence muscle 4-3 on the outer round surface of optical fiber 4-5 and Fiber Bragg Grating FBG 4-4, FRP intelligence muscle 4-3 two fixed ends in pedestal 4-6, the two ends of pedestal 4-6 are passed through cinch bolt 4-7 respectively with intelligent muscle 4-3 clamping

The sidewall center of pedestal 4-6 has a contact apertures, another lateral wall of the pedestal 4-6 relative with this sidewall is a stationary plane, pressure contact 4-2 is set in the described contact apertures, pressure contact 4-2 goes up and the two ends of optical fiber 4-5 axially parallel have a contact respectively, described two contacts touch on FRP intelligence muscle 4-3, two contacts are vertically across the two ends of Fiber Bragg Grating FBG 4-4, the port of described contact apertures is provided with convoluted diaphragm 4-1, and the interior corrugated surface of convoluted diaphragm 4-1 equates with gap between the outer wall surface of pressure contact 4-2.

The outer wall surface of pressure contact 4-2 is carried out contoured design according to the shape of convoluted diaphragm 4-1; make the outer wall surface of pressure contact 4-2 have the corrugated that the surface with convoluted diaphragm 4-1 matches; not only can bear the pressure of convoluted diaphragm 4-1; the function that has protection convoluted diaphragm 4-1 simultaneously prevents that pressure is excessive to produce the distortion that can't recover to convoluted diaphragm 4-1 because of bearing.

Pressure contact 4-2 contacts with 2 of FRP intelligence muscle 4-3, can guarantee when being applied to subsurface environment, and effectively that Casing Failure is outer pressure is converted to the axial strain that is encapsulated in the Fiber Bragg Grating FBG 4-4 among the FRP intelligence muscle 4-3.Two contact points of pressure contact 4-2 contact with FRP intelligence muscle 4-3, can guarantee except that axial force, not to be subjected to the acting force of any direction, therefore can guarantee ambient pressure is changed into fully the axial strain of Fiber Bragg Grating FBG 4-4 with the corresponding Fiber Bragg Grating FBG 4-4 of pressure contact 4-2 center section.

Embodiment two: present embodiment is described below in conjunction with Fig. 2, the difference of present embodiment and embodiment one is that described Convoluted diaphragm-type pipe external pressure sensor 4 also comprises fastening nut 4-8 and rubber sheet gasket 4-9, described convoluted diaphragm 4-1 is provided with rubber sheet gasket 4-9 by the port that fastening nut 4-8 is fixed on contact apertures between described convoluted diaphragm 4-1 and the fastening nut 4-8.Other composition and annexation are identical with embodiment one.

Rubber sheet gasket 4-9 described in the present embodiment is a standard component.

Adopt fastening nut 4-8 and rubber sheet gasket 4-9 that convoluted diaphragm 4-1 is fixed, have two functions: the one, can play sealing function to convoluted diaphragm 4-1, when being applied to subsurface environment,, accurately monitor the outer pressure of Casing Failure thereby produce pressure reduction inside and outside making with the fluid and Convoluted diaphragm-type pipe external pressure sensor 4 internal insulation of down-hole; The 2nd, can make convoluted diaphragm 4-1 that peripheral warping phenomenon does not take place behind pressurized, rubber sheet gasket 4-9 can be alleviated convoluted diaphragm 4-1 because the diaphragm that edge stress concentrate to produce damages, and makes convoluted diaphragm 4-1 can stand repeatedly elasticity extruding force.

Embodiment three: present embodiment is described below in conjunction with Fig. 2, present embodiment is further specifying embodiment one or two, be provided with a groove in the center cavity of described pedestal 4-6, described groove and contact apertures are oppositely arranged, and this groove along the axial length of optical fiber 4-5 greater than the axial length of described contact apertures along optical fiber 4-5.Other composition and annexation are identical with embodiment one or two.

The described design feature of present embodiment makes that the permanance of pedestal 4-6 is strong, good reliability and stable performance, can guarantee accuracy of detection.

Embodiment four: present embodiment is for to the further specifying of embodiment three, and the material of described convoluted diaphragm 4-1 is that model is the stainless steel of 316L.Other composition and annexation are identical with embodiment three.

Model is that the stainless elastic modulus of 316L is about 200 * 10 ⁹Pa is being a steady state value below 200 ℃, and linear expansion coefficient is 10.8 * 10 ^-6/ ℃, not very big with respect to other metals, can make measurement data relatively stable.

Embodiment five: below in conjunction with Fig. 2 present embodiment is described, present embodiment is the further qualification to embodiment three, and the corrugated surface of described convoluted diaphragm 4-1 is the sinusoidal curve shape.Other composition and annexation are identical with embodiment three.

The diaphragm sensitivity of the convoluted diaphragm 4-1 of sinusoidal curve shape is good, and it is concentrated to be not easy to produce stress.

Embodiment six: present embodiment is the further qualification to embodiment three, and the thickness of described convoluted diaphragm 4-1 is 1mm, and crest is 2mm to the distance between the trough, and the effective radius of described crest or trough place curve is 21mm.Other composition and annexation are identical with embodiment three.

Concrete size described in the present embodiment relatively obtains by finite element analysis.Pressure-sag curve to the convoluted diaphragm 4-1 of different thickness is analyzed as can be known, and uniform pressure point thickness is that the center amount of deflection of the center amount of deflection of the model of the 0.5mm model that is respectively 1mm and 1.5mm than thickness is big, and the linearity is best.This explanation thickness is more little, and the distortion of diaphragm is responsive more to pressure, and promptly the sensitivity of convoluted diaphragm 4-1 is high more.As can be seen, the ripple degree of depth is that crest is more little to the degree of depth between the trough from pressure-sag curve of the convoluted diaphragm 4-1 of the different ripple degree of depth, and the sensitivity of convoluted diaphragm is high more, and linearity is good more.But the ripple degree of depth is big more, the suffered stress of convoluted diaphragm 4-1 is just more little, by to the analysis of finite element result simultaneously in conjunction with in the engineering reality to the requirement of transducer range, the convoluted diaphragm 4-1 of selected above-mentioned parameter is as the flexible member of sensor in the present embodiment, 4-1 loads to convoluted diaphragm, obtain distortion, stress and strain result that load produces from 1MPa to 30MPa loading procedure, experimental result shows, the realistic engine request of yield strength of range, precision and the convoluted diaphragm 4-1 of Convoluted diaphragm-type pipe external pressure sensor 4.

Embodiment seven: present embodiment is described below in conjunction with Fig. 1 to Fig. 4, the described Casing Failure external pressure monitoring device of present embodiment based on embodiment one described Convoluted diaphragm-type pipe external pressure sensor, it comprises Convoluted diaphragm-type pipe external pressure sensor 4, laser instrument 1, photo-coupler 2 and data acquisition processing circuit 3

The light signal input end of described Convoluted diaphragm-type pipe external pressure sensor 4 connects the light signal output end of photo-coupler 2, and the light signal input end of photo-coupler 2 connects the light signal output end of laser instrument 1; The light signal output end of described Convoluted diaphragm-type pipe external pressure sensor 4 connects the light signal input end of data acquisition processing circuit 3.

The outer pressure of described Casing Failure at first affacts on the convoluted diaphragm 4-1, the pressure direction displacement that convoluted diaphragm 4-1 produces makes pressure contact 4-2 that FRP intelligence muscle 4-3 is bent, the pressure that FRP intelligence muscle 4-3 is born makes encapsulation Fiber Bragg Grating FBG 4-4 within it that axial deformation take place, at this moment, the outer pressure of Casing Failure changes the variation that shows as grating centre wavelength.The light signal of laser instrument 1 output is coupled among the Fiber Bragg Grating FBG 4-4 behind photo-coupler 2, data acquisition processing circuit 3 is gathered the variation that obtains grating centre wavelength in the reflectance spectrum, by the pressure calibration experiment, can obtain fiber grating center wavelength variation and the relation of managing the external pressure size, and then obtain the pipe external pressure of Casing Failure.FRP intelligence muscle 4-3 is a kind of fibre-reinforced plastics; have that high-strength light, corrosion resistance and good, good electrical property, thermal behavior are good, designability reaches advantages such as manufacturability is good well, can play a very good protection optical fiber 4-5 and Fiber Bragg Grating FBG 4-4.

The effect of cinch bolt 4-7 is that FRP intelligence muscle 4-3 and pedestal 4-6 are sealed and clamp, and cinch bolt 4-7 can be coated with fluid sealant in use, can play clamping action and can play sealing function again.The outward appearance of described Convoluted diaphragm-type pipe external pressure sensor 4 is a rectangle, and according to the empirical data of down-hole, can select the range of Convoluted diaphragm-type pipe external pressure sensor 4 is 30MPa.The centre wavelength of Fiber Bragg Grating FBG 4-4 may be selected to be 1530.452nm; Laser instrument 1, photo-coupler 2 and data acquisition processing circuit 3 are formed the FBG (FBG) demodulator, it is the Fiber Bragg Grating FBG (FBG) demodulator, the SI-720 type FBG (FBG) demodulator that described FBG (FBG) demodulator can adopt U.S. Micron Optics company to produce, the wavelength resolution of this instrument is 1pm, sweep limit is 1520nm～1570nm, and sweep frequency is 5Hz.

Embodiment eight: present embodiment is described below in conjunction with Fig. 1, the difference of present embodiment and embodiment seven is that it also comprises one or more Convoluted diaphragm-type pipe external pressure sensors 4, and described one or more Convoluted diaphragm-type pipe external pressure sensors 4 and former Convoluted diaphragm-type pipe external pressure sensor 4 are connected in series by optical fiber.Other composition and annexation are identical with embodiment seven.

A plurality of Convoluted diaphragm-type pipe external pressure sensors 4 can be realized the pressure state monitoring to the outer a plurality of positions of Casing Failure.

Embodiment nine: below in conjunction with Fig. 1 present embodiment is described, the method that described employing embodiment seven of present embodiment or eight described Casing Failure external pressure monitoring devices are realized the monitoring of pipe external pressure, realize that the process of pressure monitoring is:

Step 1: one or more Convoluted diaphragm-type pipe external pressure sensors 4 are fixed on described Casing Failure needs the monitoring pressure place outward, the stationary plane of described Convoluted diaphragm-type pipe external pressure sensor 4 is closely contacted with the Casing Failure outer wall, will be installed on by the FBG (FBG) demodulator that laser instrument 1, photo-coupler 2 and data acquisition processing circuit 3 are formed on the ground at described oil-water well well head place;

Step 2: control laser instrument 1 output beam, make described light beam export optical fiber 4-5 to through photo-coupler 2, and transfer to Fiber Bragg Grating FBG 4-4, and gather the light signal of optical fiber 4-5 output by data acquisition processing circuit 3, calculate and obtain the pressure that described Casing Failure is subjected to outward.

The FBG (FBG) demodulator is installed on the ground at well head place, with Convoluted diaphragm-type pipe external pressure sensor 4 times in oil well, and be fixed on the Casing Failure outer wall that need carry out the pressure monitoring position, the stationary plane of pedestal 4-6 is fixed on the described well sleeve outer wall, make optical fiber 4-5 axially and axially the paralleling of described well sleeve pipe, the light signal of laser instrument 1 output is coupled among the Fiber Bragg Grating FBG 4-4 behind photo-coupler 2, the data that data acquisition processing circuit 3 is gathered change with the variation of grating centre wavelength in the reflectance spectrum, by the relation of grating center wavelength variation and sleeve pipe external pressure size, obtain the size of sleeve pipe external pressure by the change calculations of grating centre wavelength.

Outside Casing Failure, need the position of monitoring pressure that Convoluted diaphragm-type pipe external pressure sensor 4 is installed respectively as required, obtain the pressure value of outer bound pair Casing Failure, realized the quasi-distributed real-time online measuring of Casing Failure external pressure.

Embodiment ten: below in conjunction with Fig. 3 and Fig. 4 present embodiment is described, present embodiment is further specifying embodiment nine: the method for the pressure that the calculating Casing Failure is subjected to outward in the described step 2 is:

According to the classical equation of Maxwell,, obtain formula in conjunction with optical fiber coupled mode theory:

λ _B＝2n _effΛ，

λ in the formula _BCentre wavelength for Fiber Bragg Grating FBG 4-4;

n _EffEffective refractive index for Fiber Bragg Grating FBG 4-4;

Λ is the grid cycle of Fiber Bragg Grating FBG 4-4;

The change Δ Λ of Fiber Bragg Grating FBG 4-4 grid cycle is:

ΔΛ＝Δε·Λ，

Δ ε is subjected to the axial strain that the axial stress effect produces for Fiber Bragg Grating FBG 4-4 in the formula;

The effective refractive index changes delta n of Fiber Bragg Grating FBG 4-4 _EffFor:

$\mathrm{\Δ}{n}_{\mathrm{eff}}=\frac{{n_{\mathrm{eff}}}^3\mathrm{\Δ\ϵ}}{2}[{\mathrm{\μp}}_{11}-(1-\mathrm{\μ})p_{12}],$

μ is a Poisson ratio in the formula, p ₁₁Be first elasto-optical coefficient of optical fiber 4-5, p ₁₂Be second elasto-optical coefficient of optical fiber 4-5, according to the center wavelength variation Δ λ of above-mentioned various acquisition Fiber Bragg Grating FBG 4-4 _BWith λ _BThe relational expression of ratio be:

$\frac{\mathrm{\Δ}{\mathrm{\λ}}_B}{{\mathrm{\λ}}_B}=\frac{\mathrm{\Δ\Λ}}{\mathrm{\Λ}}+\frac{{\mathrm{\Δn}}_{\mathrm{eff}}}{n_{\mathrm{eff}}}=(1-P_e)\mathrm{\Δ\ϵ},$

In the formula $P_e=-\frac{{{\mathrm{<figure-callout\; id="2"\; label="n\; eff"\; filenames="HDA0000038966930000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_{\mathrm{eff}}}^2}{2}[{\mathrm{\&mu;p}}_{11}-(1-\mathrm{\&mu;})p_{12}],$

With formula

Be deformed into: Δ λ _B=k _zΔ ε,

K in the formula _z=λ _B(1-P _e), k _zFor causing, axial strain the sensitivity coefficient of wavelength variations obtains Casing Failure external pressure P and wavelength variations Δ λ by the four-point bending principle again _BThe pass be:

$P=\frac{{144E}^2{I}^2{(l-2b)}^2}{({3l}^2-{4b}^2)\&CenterDot;k_z\&CenterDot;b}\&CenterDot;{(\mathrm{\&Delta;}{\mathrm{\&lambda;}}_B+\frac{{2k}_{z}b}{l-2b})}^2-\frac{{576k}_{z}b{E}^2{I}^2}{{3l}^2-{4\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA0000038966930000011.png"\; state="\{\{state\}\}">b</figure-callout>}}^2},$

E is the elastic modulus of FRP intelligence muscle 4-3 in the formula, and I is the section modulus of FRP intelligence muscle 4-3, and l is the length overall of beam between the two fixed ends point of FRP intelligence muscle 4-3, and b is stress point and the nearest distance of consolidating between the fulcrum,

Following formula is reduced to: P=A δ+B,

In the formula $A=\frac{144E^2{I}^2{(l-2b)}^2}{({3l}^2-{4b}^2)\&CenterDot;k_z\&CenterDot;b},$ $B=-\frac{576k_{z}b{E}^2{I}^2}{{3l}^2-{4\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA0000038966930000011.png"\; state="\{\{state\}\}">b</figure-callout>}}^2},$ $\mathrm{\&delta;}={(\mathrm{\&Delta;}{\mathrm{\&lambda;}}_B+\frac{{2k}_{z}b}{l-2b})}^2.$

The center wavelength variation Δ λ of Fiber Bragg Grating FBG 4-4 in the present embodiment _BObtain by data acquisition processing circuit 3 direct detections, can obtain corresponding δ value,, promptly obtained the center wavelength variation of Fiber Bragg Grating FBG 4-4 and the relation of Casing Failure external pressure P by the relation of δ and P.

Present embodiment has been utilized the pipe external pressure on-line monitoring principle based on optical fiber sensing network, when Fiber Bragg Grating FBG 4-4 is subjected to extraneous strain variation, grating grid cycle Λ can change, photoelastic effect can cause the variation of Fiber Bragg Grating FBG 4-4 effective refractive index simultaneously, thus the grating center wavelength variation.

The prerequisite that the change Δ Λ of Fiber Bragg Grating FBG 4-4 grid cycle is calculated is, suppose that ambient temperature is invariable, when Fiber Bragg Grating FBG 4-4 is subjected to axial strain that the axial stress effect produces and is Δ ε, be-μ Δ ε that shear stress is zero in strain perpendicular to other both direction of optical fiber 4-5 axle.

In single-mode fiber, k _z=1.2pm.

By formula Δ λ _B=k _zΔ ε as can be known, the drift of Fiber Bragg Grating FBG 4-4 wavelength with should become good linear relationship, because Fiber Bragg Grating FBG 4-4 is minimum measurement unit with light wavelength, it can reach the pm magnitude for the detection resolution of the drift of Fiber Bragg Grating FBG 4-4 wavelength, and promptly Fiber Bragg Grating FBG 4-4 can be as accurate as 1 microstrain to the measurement of strain.

Casing Failure external pressure P and wavelength variations Δ λ _BRelational expression used the four-point bending principle in the mechanics of materials,

The mechanics principle of four-point bending is as follows:

FRP intelligence muscle 4-3 two fixed ends in pedestal 4-6, when only having any to be under pressure on the beam between the two fixed ends point, maximum defluxion f is:

$f=-\frac{\mathrm{Pb}({3l}^2-{4b}^2)}{48\mathrm{EI}},$

This moment, P was the single-point pressure.Four-point bending is to superpose on the basis in three-point bending, can obtain the amount of deflection f formula that FRP intelligence muscle 4-3 produces when pressure contact 4-2 compresses:

$f=-\frac{\mathrm{Pb}({3l}^2-{4b}^2)}{24\mathrm{EI}},$

Can determine that thus Fiber Bragg Grating FBG 4-4 is subjected to the axial strain Δ ε that the axial stress effect produces and is:

$\mathrm{\&Delta;\&epsiv;}=\frac{2(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA0000038966930000011.png"\; state="\{\{state\}\}">b</figure-callout>}}^2+f^2}-b)}{l-2b},$

Be the elongation of beam Fiber Bragg Grating FBG 4-4 under the effect of single-point power, l-2b is the length of Fiber Bragg Grating FBG 4-4.

Can obtain based on above-mentioned formula

$\mathrm{\&Delta;}{\mathrm{\&lambda;}}_B=k_z\&CenterDot;\frac{2(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA0000038966930000011.png"\; state="\{\{state\}\}">b</figure-callout>}}^2+f^2}-b)}{l-2b},$

And then obtain Casing Failure external pressure P and wavelength variations Δ λ _BRelational expression.

In the present embodiment, Fiber Bragg Grating FBG 4-4 is encapsulated among the FRP intelligence muscle 4-3 as seen from Figure 3, FRP intelligence muscle 4-3 adopts fiber-reinforced resin, fiber-reinforced resin is to be mixed by certain technology by epoxy resin and fiberglass reinforcement, has corrosion resistant characteristic, and have very high intensity, can be good at protecting inner Fiber Bragg Grating FBG 4-4; Fiber Bragg Grating FBG 4-4 and FRP intelligence muscle 4-3 is closely sticking and be in the same place, and the Fiber Bragg Grating FBG 4-4 of inside also can cooperative transformation when strain takes place FRP intelligence muscle 4-3, has so just guaranteed the precision of detection.

As seen from Figure 4; be encapsulated in the optical fiber 4-5 in the FRP intelligence muscle 4-3; have a plurality of protective seams; a plurality of protective seams and optical fiber 4-5 form the armouring optical cable; they are respectively from inside to outside: metal hose layer A; 8 gangs of Kevlar layer B; wire sheathing C; PU inner restrictive coating D; wire sheathing E; PU external sheath layer F; the axial load of optical fiber 4-5 is all carried by outer field metal organization level like this, and impact radially also can absorb by protected seam, and optical fiber 4-5 is in the state that does not stress substantially; the data transmission that Convoluted diaphragm-type pipe external pressure sensor 4 is collected that can success and can not born the bigger axial load and the borehole wall because of needs to ground; the bump of sleeve pipe and being destroyed.

Claims (10)

1. Convoluted diaphragm-type pipe external pressure sensor, it is characterized in that: described Convoluted diaphragm-type pipe external pressure sensor (4) comprises convoluted diaphragm (4-1), pressure contact (4-2), FRP intelligence muscle (4-3), Fiber Bragg Grating FBG (4-4), optical fiber (4-5), pedestal (4-6) and cinch bolt (4-7)

Pedestal, in the center cavity (4-6) optical fiber is set, (4-5) and Fiber Bragg Grating FBG, (4-4), Fiber Bragg Grating FBG, (4-4) be positioned at the center of described center cavity, Fiber Bragg Grating FBG, two ends (4-4) are provided with optical fiber respectively, (4-5), optical fiber, (4-5) and Fiber Bragg Grating FBG, all encapsulate FRP intelligence muscle on the outer round surface (4-4), (4-3), FRP intelligence muscle, (4-3) at pedestal, two fixed ends (4-6), pedestal, cinch bolt is passed through at two ends (4-6) respectively, (4-7) with intelligent muscle, (4-3) clamping

A sidewall center of pedestal (4-6) has a contact apertures, another lateral wall of the pedestal (4-6) relative with this sidewall is a stationary plane, pressure contact (4-2) is set in the described contact apertures, pressure contact (4-2) is gone up and the two ends of optical fiber (4-5) axially parallel have a contact respectively, described two contacts touch on FRP intelligence muscle (4-3), two contacts are vertically across the two ends of Fiber Bragg Grating FBG (4-4), the port of described contact apertures is provided with convoluted diaphragm (4-1), and the interior corrugated surface of convoluted diaphragm (4-1) equates with gap between the outer wall surface of pressure contact (4-2).

2. Convoluted diaphragm-type pipe external pressure sensor according to claim 1, it is characterized in that: described Convoluted diaphragm-type pipe external pressure sensor (4) also comprises fastening nut (4-8) and rubber sheet gasket (4-9), described convoluted diaphragm (4-1) is fixed on the port of contact apertures by fastening nut (4-8), between described convoluted diaphragm (4-1) and the fastening nut (4-8) rubber sheet gasket (4-9) is set.

3. Convoluted diaphragm-type pipe external pressure sensor according to claim 1 and 2, it is characterized in that: be provided with a groove in the center cavity of described pedestal (4-6), described groove and contact apertures are oppositely arranged, and this groove along the axial length of optical fiber (4-5) greater than the axial length of described contact apertures along optical fiber (4-5).

4. Convoluted diaphragm-type pipe external pressure sensor according to claim 3 is characterized in that: the material of described convoluted diaphragm (4-1) is that model is the stainless steel of 316L.

5. Convoluted diaphragm-type pipe external pressure sensor according to claim 3, it is characterized in that: the corrugated surface of described convoluted diaphragm (4-1) is the sinusoidal curve shape.

6. Convoluted diaphragm-type pipe external pressure sensor according to claim 3, it is characterized in that: the thickness of described convoluted diaphragm (4-1) is 1mm, and crest is 2mm to the distance between the trough, and the effective radius of described crest or trough place curve is 21mm.

7. Casing Failure external pressure monitoring device based on the described Convoluted diaphragm-type pipe of claim 1 external pressure sensor, it is characterized in that: it comprises Convoluted diaphragm-type pipe external pressure sensor (4), laser instrument (1), photo-coupler (2) and data acquisition processing circuit (3)

The light signal input end of described Convoluted diaphragm-type pipe external pressure sensor (4) connects the light signal output end of photo-coupler (2), and the light signal input end of photo-coupler (2) connects the light signal output end of laser instrument (1); The light signal output end of described Convoluted diaphragm-type pipe external pressure sensor (4) connects the light signal input end of data acquisition processing circuit (3).

8. the Casing Failure external pressure monitoring device based on Convoluted diaphragm-type pipe external pressure sensor according to claim 7, it is characterized in that: it also comprises one or more Convoluted diaphragm-type pipe external pressure sensors (4), and described one or more Convoluted diaphragm-type pipe external pressure sensors (4) are connected in series by optical fiber with former Convoluted diaphragm-type pipe external pressure sensor (4).

9. one kind is adopted claim 7 or 8 described Casing Failure external pressure monitoring devices to realize the method that the pipe external pressure is monitored, and it is characterized in that: the process that realizes pressure monitoring is:

Step 1: one or more Convoluted diaphragm-type pipe external pressure sensors (4) are fixed on described Casing Failure needs the monitoring pressure place outward, the stationary plane of described Convoluted diaphragm-type pipe external pressure sensor (4) is closely contacted with the Casing Failure outer wall, will be installed on by the FBG (FBG) demodulator that laser instrument (1), photo-coupler (2) and data acquisition processing circuit (3) are formed on the ground at described oil-water well well head place;

Step 2: control laser instrument (1) output beam, make described light beam export optical fiber (4-5) to through photo-coupler (2), and transfer to Fiber Bragg Grating FBG (4-4), gather the light signal of optical fiber (4-5) output by data acquisition processing circuit (3), calculate and obtain the pressure that described Casing Failure is subjected to outward.

10. the method for realization Casing Failure external pressure monitoring according to claim 9 is characterized in that: the method for the pressure that the calculating Casing Failure is subjected to outward in the described step 2 is:

According to the classical equation of Maxwell,, obtain formula in conjunction with optical fiber coupled mode theory:

λ _B＝2n _effΛ，

λ in the formula _BCentre wavelength for Fiber Bragg Grating FBG (4-4);

n _EffEffective refractive index for Fiber Bragg Grating FBG (4-4);

Λ is the grid cycle of Fiber Bragg Grating FBG (4-4);

The change Δ Λ of Fiber Bragg Grating FBG (4-4) grid cycle is:

ΔΛ＝Δε·Λ，

Δ ε is that Fiber Bragg Grating FBG (4-4) is subjected to the axial strain that the axial stress effect produces in the formula;

The effective refractive index changes delta n of Fiber Bragg Grating FBG (4-4) _EffFor:

$\mathrm{\&Delta;}{n}_{\mathrm{eff}}=\frac{{n_{\mathrm{eff}}}^3\mathrm{\&Delta;\&epsiv;}}{2}[{\mathrm{\&mu;p}}_{11}-(1-\mathrm{\&mu;})p_{12}],$

μ is a Poisson ratio in the formula, p ₁₁Be first elasto-optical coefficient of optical fiber (4-5), p ₁₂Be second elasto-optical coefficient of optical fiber (4-5),

Center wavelength variation Δ λ according to above-mentioned various acquisition Fiber Bragg Grating FBG (4-4) _BWith λ _BThe relational expression of ratio be:

$\frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_B}{{\mathrm{\&lambda;}}_B}=\frac{\mathrm{\&Delta;\&Lambda;}}{\mathrm{\&Lambda;}}+\frac{{\mathrm{\&Delta;n}}_{\mathrm{eff}}}{n_{\mathrm{eff}}}=(1-P_e)\mathrm{\&Delta;\&epsiv;},$

In the formula $P_e=-\frac{{n_{\mathrm{eff}}}^2}{2}[{\mathrm{\&mu;p}}_{11}-(1-\mathrm{\&mu;})p_{12}],$

With formula

Be deformed into: Δ λ _B=k _zΔ ε,

K in the formula _z=λ _B(1-P _e), k _zFor axial strain causes the sensitivity coefficient of wavelength variations,

Obtain Casing Failure external pressure P and wavelength variations Δ λ by the four-point bending principle again _BThe pass be:

$P=\frac{{144E}^2{I}^2{(l-2b)}^2}{({3l}^2-{4b}^2)\&CenterDot;k_z\&CenterDot;b}\&CenterDot;{(\mathrm{\&Delta;}{\mathrm{\&lambda;}}_B+\frac{{2k}_{z}b}{l-2b})}^2-\frac{{576k}_{z}b{E}^2{I}^2}{{3l}^2-{4b}^2},$

E is the elastic modulus of FRP intelligence muscle (4-3) in the formula, and I is the section modulus of FRP intelligence muscle (4-3), and l is the length overall of beam between the two fixed ends point of FRP intelligence muscle (4-3), and b is stress point and the nearest distance of consolidating between the fulcrum,

Following formula is reduced to: P=A δ+B,

In the formula $A=\frac{144E^2{I}^2{(l-2b)}^2}{({3l}^2-{4b}^2)\&CenterDot;k_z\&CenterDot;b},$ $\mathrm{\&delta;}={(\mathrm{\&Delta;}{\mathrm{\&lambda;}}_B+\frac{{2k}_{z}b}{l-2b})}^2,$ $B=-\frac{576k_{z}b{E}^2{I}^2}{{3l}^2-{4b}^2}.$

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