CN106481339B - Based on electromagnetism-heat-acoustic effect gas hydrates with probing survey and analogy method - Google Patents
Based on electromagnetism-heat-acoustic effect gas hydrates with probing survey and analogy method Download PDFInfo
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/001—Survey of boreholes or wells for underwater installation
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Abstract
It is a kind of based on electromagnetism-heat-acoustic effect gas hydrates with probing survey and analogy method, be related to it is a kind of for deep-sea bottom gas hydrates with boring detection method, in particular to a kind of to be motivated based on electromagnetic pulse, hydrate phase change is induced, electromagnetism-heat-acoustical signal gas hydrates detection and analogy method are generated.Two groups of coils are placed above drill collar, in well logging pipe nipple, when being passed through transient pulse electric current, contains in the pore media of seawater around and excites eddy current, makes the heated generation phase transformation of pore media moment and thermal expansion, induces electromagnetism-heat-acoustical signal.Electromagnetism-heat-acoustical signal wave equation is established by Maxwell equation and Clapeyron equation, has invented a kind of hydrate phase change induction electromagnetism-heat-acoustical signal method for numerical simulation.
Description
Technical field
The present invention relates to a kind of for deep-sea bottom gas hydrates, based on electromagnetism-heat-acoustic effect with probing survey side
Method, in particular to a kind of to be motivated based on electromagnetic pulse, the gas hydrates of acoustical signal processing are surveyed with probing and analogy method.
Background technique
Gas hydrates are called combustible ice, have that energy density is high, distribution is wide, scale is big, buries shallow, accumulating condition
The features such as superior, has become the crude oil alternative energy source of the following most potentiality to be exploited as a kind of clean energy resource of rich reserves
One of.
By years of researches and development, phase conversion mechanism, the regularity of distribution and spy of the domestic and foreign scholars to gas hydrates
Survey method has carried out many beneficial explorations, has accumulated experience abundant.But due to the Gas Hydrate Deposition of various regions
Environment and geological conditions are not quite similar, therefore are also not quite similar to the method for hydrate exploration and well logging.Wherein current application
Exploitation method mainly has: seismic reflection method, Geochemical method, geothermal method, authigenic sediment mineral method etc.；And logging method is main
Have: resistivity logging, sonic time difference well logging, self-potential method well logging etc..
It is currently with the main method used in guiding well logging is bored with electromagnetic wave resistivity logging is bored, it utilizes the high electricity of oil reservoir
Resistance rate and water flooding, mud low-resistivity between difference obtain oil reservoir by detecting the azimuth distribution of high resistivity and boring
Into directional information in the process, so that dynamic adjusts the drilling direction of drill bit.The resistivity of experiment discovery gas hydrates is big
About 5k Ω/mk Ω m (I type combustible ice) is suitable with oil-gas Layer, make it is traditional with bore electromagnetic wave resistivity logging be difficult to distinguish
Combustible ice and oil-gas Layer.
In order to determine the distributed intelligence of gas hydrates by log data, generally require above-mentioned a variety of well loggings
Data carry out comprehensive analysis.Such as the resistivity logging numerical value of natural gas hydrate deposit is higher, the acoustic logging time difference is smaller,
Natural potential response amplitude is weak, neutron well logging curve values are higher etc..It is generally necessary to could integrate and sentence when meeting above-mentioned multiple conditions
Disconnected current formation may contain gas hydrates, therefore specificity is poor.Finally by this most direct side of drilling extracting core
The result of formula verifying comprehensive descision.Due to the complexity of gas hydrates logging method, make there is presently no it is a kind of efficiently, can
It leans on, the strong well logging method of selectivity, can judge the azimuth distributions of gas hydrates in the first time of drilling.
Gas hydrates are the equilibrium systems of a meta-stable, ambient temperature, pressure disturbance under phase easily occurs
Become, liquid and gas are changed by solid phase.This unique physical characteristic is to reduce combustible ice recovery ratio, draw during drilling
Send out the negative effect factor of down-hole accident；However in well logging field, if it is possible to utilize this phase change characteristics, day can be obtained
Right gas hydrate is different from the log response signal of other oil reservoirs, will be expected to realize it is a kind of specifically for gas hydrates with
Probing looks into and with brill guidance method.
Magnetic-heat-acoustic imaging (Magnetically mediated thermo-acoustic, MMTA) is by Singapore south
The detection of Novel resistor rate and imaging method that the Feng of foreign Polytechnics was proposed on " Applied Physics flash report " in 2013 for the first time.
As shown in Fig. 1, principle are as follows: by applying the amplitude-modulated current that carrier frequency is 20MHz to a compact magnetic resonance coil
Signal generates transient state alternating magnetic field, induction field is generated inside conductive body, then generates Joule heat, to excite thermoelastic
The acoustical signal of property.Wherein the frequency of modulating wave determines the frequency of thermoacoustic wave.MMTA is based on using alternating magnetic field as excitaton source
Media interior Joule heat absorptivity difference, using sound wave as the detection of the non-intrusion type of information carrier and imaging technique.
The resistivity detection of MMTA is a kind of method for combining electromagnetic excitation with acoustic detection with imaging method.In phase
In the case where same frequency, the wavelength of sound wave is shorter than electromagnetic wave, and it is deeper to propagate depth in the earth formation, therefore detection range is remote, differentiates
Rate is high.And the phase change characteristics of hydrate make it by electromagnetism-thermal agitation, are easy gasification, inspire stronger sound
Wave signal.If electromagnetism-heat-acoustical coupling mechanism can be applied in gas hydrates with field of detecting is bored, will be expected to obtain
" phase transformation thermoacoustic " signal, to enhance the specificity of hydrate detection, improve detection accuracy and Drilling ratio.
Summary of the invention
It is of the present invention based on electromagnetism-heat-acoustic effect gas hydrates with probing survey and analogy method, be utilize
The coil excitation transient state high-energy electromagnetic pulse being installed on well logging pipe nipple, transient electromagnetic pulse is with certain conductivity
Eddy current is excited in stratum, transient eddy currents generate the fuel factor of transient state in the stratum of wellbore；Gas hydrates group
At porous media under the action of transient thermal effect, generate the thermal expansion and phase transformation of transient state；The wherein gas that transient state phase transformation generates
State substance can greatly enhance the transient state cubical expansivity of pore media, excite stronger acoustic signals.
Volume expansion caused by transient state phase transformation and common thermal expansion cooperatively inspire measurable thermoacoustic signal, and to
Surrounding is propagated；The frequency of thermoacoustic wave is consistent with electromagnetic pulse dominant frequency；The acoustical signal of this specific frequency is easy to by identical frequency
Sonic probe detection, and utilize the location distribution information of its inverting hydrate.
According to above-mentioned principle, the acoustical signal that transient electromagnetic pulse excites in hydrate pore media mostlys come from two
Aspect, first is that thermoacoustic source caused by pore media itself thermally expands, second is that gas caused by gas hydrates transient state phase transformation is swollen
Swollen sound source.Assuming that pore media is made of equally distributed hydrate molecule, seawater and the loose seabed grains of sand, one is taken
Micro volume unit is research object, due to electromagnetic excitation short duration (about 1 μ s or so), hydrate transient state phase transformation
When the gas that generates also have little time largely to assemble, also assume that it is dispersed in pore media herein；Unit bodies ponding simultaneously
The volumetric wear that the gas volume that the phase transformation of object solid portion generates is much larger than solid itself is closed, therefore solid in negligible pore media
The loss of body mass volume, that is to say, that, it is believed that the volume expansion of sound source caused by phase transformation mostlys come from liquid.
Under above-mentioned reasonable hypothesis, it can derive under transient electromagnetic pulse excitation, hydrate phase change induces acoustical signal institute
The wave equation of satisfaction.
In the hot thermodynamical equilibrium system of gas hydrates, the Clapeyron equation that system meets can be written as differential shape
Formula:
Wherein p is pressure, and T is temperature, HxIt is latent heat of phase change, Δ v indicates the variation of volume in phase transition process.Consider dynamic
Change procedure, the derivative of time can be obtained by introducing on equation (1) both sides:
Equation (2) is shown under heat source excitation, and t's pore media temperature T changes at any time, the volume expansion of phase transformation
Effect can cause pressure p to change with time.H thereinxIt is that latent heat of phase change is converted into heat source function under electromagnetic excitation
Part.Assuming that total heat source function of transient electromagnetic pulse excitation is H, then H thereinxIt is changed into latent heat, H-HxIt is partially converted to
Interior energy, generates the temperature rise of transient state.So that
H (r, t)=Hin(r,t)+Hx(r,t) (3)
Here any point in r representation space.Assuming that Hin(r, t)=χ H (r, t) then Hx(r, t)=(1- χ) H (r, t),
Here χ indicates that the heat that interior energy is converted in heat source function accounts for the percentage of total amount of heat.
According to the equation of heat conductionDiffusion term can be ignored in the case where pulse excitation:
Wherein CpFor specific heat capacity.It brings formula (3) (4) into formula (1), can obtain:
The characteristics of according to electromagnetism-heat-acoustically-driven, it will be assumed that external heat content is swashed with the time form of Dirac function
It encourages, then formula (5) is writeable are as follows:
Formula (6) both sides are integrated multiplied by dt, then to the time
Enabling p ' is initial pressure change caused by sound source, then in the initial acoustic pressure at t=0 moment are as follows:
Since what is be precipitated in pore media is gas, and assume that the sound source of its volume expansion excitation acts only on pore media
In fluid section, the variation so as to cause initial acoustic pressure exists only in internal fluid；That is, thermoacoustic source is only to liquid portion
The initial acoustic pressure divided contributes；Additionally, due to be transient state excitation, the only a small part solid under the action of this excitation
Phase transformation has occurred in grain, produces substantial portion of gas (the solid, liquid ratio of nominally phase transformation is 1:164), that is to say, that
Thermoacoustic source influences much larger than the influence to solid phase the liquid phase in pore media, thus ignores the sound that phase transformation excites in solid phase
Source can obtain:
Wherein u be liquid in acoustic displacement vector, by formula (8) bring into (9) can obtain initial displacement caused by phase transformation dissipate
The variation of degree is
Below the fluctuation that electromagnetism-heat-acoustic signal propagation is met in pore media will be established on the basis of phase transformation sound source
Equation.It is theoretical according to the Underwater Acoustic Propagation of BIOT pore media, consider heat caused by the divergence sound source and temperature rise of formula (10) description
Sound source can rewrite Hooke's law are as follows:
Wherein, λ and μ is the Lame constants of solid matter in pore media, and ε indicates normal strain, and γ indicates shear strain, σ table
Show direct stress, τ indicates shearing stress, and R is the coefficient between liquid volume expansion and fluid pressure, and Q is liquid volume variation and solid
The coefficient of coup between body volume change, β1For the thermal expansion coefficient of solid matter, β2For the thermal expansion coefficient of liquid substance, ρ is
The density of liquid, CsIt is the velocity of sound in liquid, CpIt is the specific heat capacity of liquid, T is temperature, exbpzCaused by being phase transformation
The volume expansion factor.
According to formula (11), the expansion wave that the electromagnetism-heat-sound source excitation magnetosonic wave meets can be obtained using law of conservation of energy
Equation are as follows:
The physical parameter and distribution situation of the given pore media containing hydrate, can be in the hope of using numerical algorithms such as finite elements
The numerical solution of formula (12) obtains the electromagnetism-regularity of distribution of heat-acoustical signal in the medium, believes to realize electromagnetism-heat-sound
Number emulation and simulation.Right side first item in formula (12) indicates contribution of the thermal expansion to sound source, and Section 2 indicates phase transformation pair
The contribution of sound source.
In order to realize above-mentioned excitation and detection process, three crucial groups must be provided simultaneously in Hardware Design
At part: electromagnetic exciter system, acoustic wave sensing system and synchronous control system.Electromagnetic exciter system is mainly by two groups of excitation lines
Circle, transient state Impulsive Current generator composition；Detection system is by several sonic probes, weak acoustic signal amplifier and synchrodata
Collector composition；Excitation and detection work asynchronously under the control of synchronous control system；Excitation coil and sonic probe are placed
In well logging pipe nipple.
Excitation and testing process are as described below: step 1 is passed through pulse in two coils under the control of master control system
Current excitation signal excites the magnetosonic wave in fluid；Step 2, after fixed ultrasonic transmission time, the multiple sound of synchronous acquisition
The acoustical signal that probe receives；The collected data of Multi-path synchronous are carried out analytical calculation, utilize sound wave by step 3, master control system
Propagation law obtain gas hydrates pore media location information.
Detailed description of the invention
Fig. 1 magnetic-heat-acoustic imaging schematic diagram.
In figure: 11 transient pulse magnetic fields, 12 conductive imaging bodies, 6 sonic probes, 8 excitation coils 1.
Fig. 2 is based on electromagnetism-heat-acoustical coupling with brill hydrate detection method schematic diagram.
In figure: 1 (inside has mud) without magnetic GRP drilling tool, 2 annular spaces, 3 invaded zones, 4 intermediate zones, 5 excitation coil, 2,6 sound wave
Probe, 8 excitation coil, 1,9 pore media containing hydrate, 10 magnetic thermoacoustic waves, 11 prime stratums.
Fig. 3 surveys excitation and testing process schematic diagram with probing based on electromagnetism-heat-acoustical coupling hydrate.
In figure: 31 apply electromagnetic excitation, 32 synchronous acquisition multi-path echo data, and 33 analyzing multiple echo datas determine water
It closes object and is distributed azimuth information, 34 electromagnetic exciter systems, 35 acoustic wave sensing systems, 36 synchronous control systems.
Specific embodiment
The present invention will be further described with reference to the accompanying drawings and detailed description.
It is of the present invention to excite the porous media containing hydrate using transient state high-energy electromagnetic pulse, electromagnetic energy excitation
Joule heat is as a kind of thermal transient source forcing, in the case where transient energy is sufficiently large, can destroy the Asia of gas hydrates
Equilibrium system makes local pore media while generating transient state thermal expansion, (becomes liquid from solid-state along with the phase transformation of transient state
And gaseous state).The phase transformation of hydrate can generate gaseous material, greatly increase its volume, see enhance thermoacoustic on the whole
The cubical expansivity in source, to improve wave amplitude.Therefore, the acoustic signals detected using this method can be surveyed with brill
Position (lateral depth) information for reflecting gas hydrates in amount, can also rebuild hydrate in hole by the research of inverse problem
Distribution in medium.
Electromagnetism-heat-acoustic effect is similar to microwave thermoacoustic effect, is all based on transient electromagnetic wave incentives target body and generates thermoacoustic
The physical mechanism in source.And microwave thermoacoustic imaging has expanded extensive research in fields such as biomedicines, gradually moves towards
Clinical application.But influenced by running space and ambient enviroment, the microwave source in microwave thermoacoustic is difficult to apply to be surveyed with brill
In measuring appratus.And water is very big to the absorptivity of microwave, so that the depth of microwave penetration is shallower.Since Feng was proposed in 2013
After magnetic-heat-acoustic imaging method, the excitation of transient state magnetic field impulse used by him also can reach effect similar with microwave excitation, by
It is low in its carrier frequency, thus penetration depth is bigger, measurement range is wider.Although larger (the moment function of pulsed magnetic field instantaneous power
Rate is 2 megawatts), short-time energy is stronger, but duty is smaller (10 a ten thousandth), and average energy is low (only 20 watts), to ring
Border requires low.With the development of power electronics technology, using power electronic devices control capacitor repid discharge, generation high energy pulse
Technology it is increasingly mature, be expected to develop practical measurement while-drilling instrument in measurement while drilling field.
As shown in Fig. 2, the present invention excites the pore media containing hydrate, electromagnetic energy using the high-energy electromagnetic pulse of transient state
The Joule heat of excitation can change natural gas in invaded zone, intermediate zone and prime stratum as a kind of transient state thermal excitation
The transient state Asia equilibrium condition of hydrate, while making local medium generate transient state thermal expansion, along with quick phase transformation (gasification).
In phase transition process, the natural gas of 164 volumes is can be obtained in 1 volume gas hydrate dissociation, therefore synchronous with driving pulse
Rapid phase transition can greatly enhance the expansion effect in thermoacoustic source, obtain stronger acoustical signal.During conventional drilling, hydrate
Phase transformation be it is random, be difficult to measure, can not therefrom obtain useful acoustic signals.But draw under being motivated for pulsed magnetic field
The thermoacoustic wave risen, can measure under the synchronization of driving pulse, this will substantially improve signal-to-noise ratio, and then improve detection essence
Degree.
In conventional magnetic-heat-acoustic imaging, measured target body is located at the surface of excitation coil, and sonic probe is looped around mesh
Standard type is outer (as shown in Figure 1).And when being used for measurement while drilling, objective body, that is, stratum, including invaded zone, intermediate zone and original
Stratum, positioned at the outside of coil, sonic probe is placed on the inside of drilling tool.Several sound waves are uniformly distributed on different angles of circumference to visit
Head, for detecting the thermoacoustic wave of stratum sending.These probes are rotated with the rotation of drilling tool, thus have circumferential resolution
Rate can distinguish the acoustical signal issued on different operating face angle.This excitation and detection pattern are all made of non-contact design, with
Electromagnetic wave resistivity logging is similar, especially suitable for measurement while drilling process.
It is surveyed based on magnetic-heat-acoustical coupling mechanism gas hydrates with probing to realize, the present invention is first from electromagnetism-
Heat-acoustical coupling direct problem is set out, and by multi- scenarios method equation, has studied the generation mechanism in thermoacoustic source, thermoacoustic source is divided into swollen
Two class of swollen thermoacoustic source and heat of transformation sound source, while deriving for the first time and establishing gas hydrates phase transformation to the mathematics of sound wave effect
Physical equation.
The sound source that transient electromagnetic pulse excites in gas hydrates pore media mostlys come from two aspects, first is that
Thermoacoustic source caused by pore media itself thermally expands, second is that gas expansion sound source caused by gas hydrates transient state phase transformation.It is false
If pore media is made of equally distributed gas hydrates molecule, seawater and the loose seabed grains of sand, take one it is micro-
Small size member is research object, due to electromagnetic excitation short duration (about 1 μ s or so), when hydrate transient state phase transformation
The gas of generation also has little time largely to assemble, and is also assumed that herein to be dispersed in pore media；Unit volume hydration simultaneously
The gas volume that object solid portion phase transformation generates is much larger than the volumetric wear of solid itself, therefore solid in negligible pore media
The loss of mass volume, that is to say, that, it is believed that the volume expansion of sound source caused by phase transformation mostlys come from liquid.
The calculation formula that transient electromagnetic pulse motivates lower phase transformation sound source is derived below.
For above-mentioned model, the Clapeyron equation met in static transformation balance can be written as differential form:
Wherein p is pressure, and T is temperature, HxIt is latent heat of phase change, Δ v indicates the variation of volume in phase transition process.Consider dynamic
Change procedure, the derivative of time can be obtained by introducing on equation (1) both sides:
Equation (2) is shown under heat source excitation, and t's pore media temperature T changes at any time, due to the volume of phase transformation
Expansion can cause pressure p to change with time.H thereinxIt is that phase transformation is converted into heat source function under electromagnetic excitation
The part of latent heat.Assuming that total heat source function of transient electromagnetic pulse excitation is H, then H thereinxIt is changed into latent heat, H-HxPart turns
It is changed to interior energy, generates the temperature rise of transient state.So that
H (r, t)=Hin(r,t)+Hx(r,t) (3)
Assuming that Hin(r, t)=χ H (r, t) then Hx(r, t)=(1- χ) H (r, t), χ here indicate to convert in heat source function
The percentage of total amount of heat is accounted for for the heat of interior energy.
According to the equation of heat conductionDiffusion term can be ignored in the case where pulse excitation:
Wherein CpFor specific heat capacity.It brings formula (3) (4) into formula (1), can obtain:
The characteristics of according to electromagnetism-heat-acoustically-driven, it will be assumed that external heat content is swashed with the time form of Dirac function
It encourages, then formula (5) is writeable are as follows:
Formula (6) both sides are integrated multiplied by dt, then to the time
Enabling p ' is initial pressure change caused by sound source, then the initial acoustic pressure at the t=0 moment are as follows:
Since what is be precipitated in pore media is gas, and assume that the sound source of its volume expansion excitation acts only on pore media
In fluid section, the variation so as to cause initial acoustic pressure exists only in internal fluid；That is, thermoacoustic source is only to liquid portion
The initial acoustic pressure divided contributes；Additionally, due to be transient state excitation, the only a small part solid under the action of this excitation
Phase transformation has occurred in grain, produces substantial portion of gas (nominally solid-to-liquid ratio is 1:164), that is to say, that thermoacoustic source pair
Liquid phase in pore media is influenced much larger than the influence to solid phase, thus ignores the sound source that phase transformation excites in solid phase, can be obtained:
Wherein u be liquid in acoustic displacement vector, by formula (8) bring into (9) can obtain initial displacement caused by phase transformation dissipate
The variation of degree is
Below the fluctuation side that magnetic-heat-acoustic signal propagation is met in pore media will be established on the basis of phase transformation sound source
Journey.It is theoretical according to the Underwater Acoustic Propagation of BIOT pore media, consider thermoacoustic caused by the divergence sound source and temperature rise of formula (10) description
Source can rewrite Hooke's law are as follows:
Wherein, λ and μ is the Lame constants of solid matter in pore media, and ε indicates normal strain, and γ indicates shear strain, σ table
Show direct stress, τ indicates shearing stress, and R is the coefficient between liquid volume expansion and fluid pressure, and Q is liquid volume variation and solid
The coefficient of coup between body volume change, β1For the thermal expansion coefficient of solid matter, β2For the thermal expansion coefficient of liquid substance, ρ is
The density of liquid, CsIt is the velocity of sound in liquid, CpIt is the specific heat capacity of liquid, T is temperature, exbpzCaused by being phase transformation
The volume expansion factor.
According to formula (11), the expansion that the electromagnetism-heat-sound source excitation magnetosonic wave meets can be obtained using law of conservation of energy
Wave equation are as follows:
The physical parameter and distribution situation of the given pore media containing gas hydrates, can using numerical algorithms such as finite elements
To solve, i.e. magnetic-the propagation condition of heat-acoustical signal in the medium, to realize to being generated in gas hydrates pore media
Electromagnetism-heat-acoustical signal emulation and simulation.
Detection system and process are as shown in Figure 3.It, must in Hardware Design in order to realize excitation and detection process
Three major parts: electromagnetic exciter system, acoustic wave sensing system and synchronous control system must be provided simultaneously with.Electromagnetic exciter system master
It to be made of two groups of excitation coils and transient state Impulsive Current generator；Detection system is by several sonic probes, weak acoustic signal
Amplifier and synchronous data collection device composition；Excitation and detection work asynchronously under the control of synchronous control system；Excitation line
Circle and sonic probe are both placed in well logging pipe nipple.
The specific implementation process of excitation and testing process are as follows: step 1, under the control of master control system, in two coils
It is passed through pulsed current excitation signal, excites electromagnetism-heat-acoustical signal in fluid；Step 2, by fixed ultrasonic transmission time with
Afterwards, the acoustical signal that the multiple sonic probes of synchronous acquisition receive；Step 3, master control system carry out the collected data of Multi-path synchronous
Analytical calculation obtains the location information of gas hydrates pore media using the propagation law of sound wave.When can be used conventional
Between the imaging methods such as reversal process or filtered back projection.Above-mentioned three step is repeated, can measure the hydrate distribution on different drilling depths
Location information.Arrow in Fig. 3 indicates that the implementing procedure in left side is completed under the corresponding hardware system support in right side.
Belonging to sum up, transient electromagnetic pulse is applied to hydrate pore media using this method and is motivated, since hydrate is easy
In the feature of phase transformation, stronger acoustical signal can be inspired in the pore media containing hydrate, to obtain specificity
Hydrate response message can be ultimately utilized in for hydrate in probing survey.
Claims (3)
1. it is a kind of based on electromagnetism-heat-acoustic effect gas hydrates with probing survey and analogy method, which is characterized in that utilize
The coil excitation transient electromagnetic pulse being installed on well logging pipe nipple, transient electromagnetic pulse is on the stratum with certain conductivity
Middle excitation eddy current, transient eddy currents generate the fuel factor of transient state in the stratum of wellbore；Gas hydrates composition
Pore media generates the thermal expansion and phase transformation of transient state under the action of transient thermal effect；The wherein gaseous state object that transient state phase transformation generates
Mass-energy greatly enhances the transient state cubical expansivity of gas hydrates pore media；Volume expansion caused by transient state phase transformation and heat are swollen
Swollen two kinds of effects inspire measurable acoustical signal jointly, and propagate around；Acoustical signal frequency is consistent with the dominant frequency of electromagnetic pulse；
It can be used for detecting the pore media containing gas hydrates with the acoustical signal of the consistent frequency of electromagnetic pulse dominant frequency；Utilize the side BIOT
Journey and Clapyron Equation simultaneous can acquire gas hydrates electromagnetism-heat-acoustical signal wave equation；Wherein, expansion wave is full
The Equations of Mathematical Physics of foot are as follows:
Wherein, λ and μ is the Lame constants of solid matter in pore media, and u is the displacement vector of solid matter, is divided into three sides
To component ux,uy,uz,U is the displacement vector of liquid, is divided into point in three directions
Measure Ux,Uy,Uz,p0It is static pressure, ρ is the density of liquid, csIt is in liquid
The velocity of sound, CpIt is the specific heat capacity of liquid, RbFor Boltzmann constant, T is temperature, and H is additional transient state burst pulse in pore media
The heat source distribution function of middle excitation, outside are applied in all heat source distribution function H of system, have χ to be partially converted to interior energy,
1- χ is partially converted to latent heat of phase change (0 < χ < 1), β1For the thermal expansion coefficient of solid matter, β2For the thermal expansion system of liquid substance
Number, ρ11、ρ22And ρ12It is to liquid substance density, solid matter density and the measurement for being associated with density between them respectively, R is liquid
The coefficient of coup between body volume expanded and fluid pressure, Q are the coupled systemes between liquid volume variation and solid volume variation
Number, ▽ is gradient operator, and t is the time, any point in r representation space.
2. it is according to claim 1 based on electromagnetism-heat-acoustic effect gas hydrates with probing survey and analogy method,
It is characterized in that hardware system is divided into electromagnetic exciter system, acoustic wave sensing system and synchronous control system three parts；Excitation system
The equipment of system mainly has: two groups of excitation coils, transient state Impulsive Current generator；The capital equipment of detection system has: Ruo Gansheng
Wave probe, weak acoustic signal amplifier, synchronous data collection device；They work asynchronously under the control of synchronous control system；
Excitation coil and sonic probe are both placed in well logging pipe nipple, and tested region is located at the stratum on the outside of pipe nipple.
3. according to claim 1 or 2 surveyed and simulation side based on electromagnetism-heat-acoustic effect gas hydrates with probing
Method, it is characterised in that excitation and testing process are as described below: step 1 is passed through pulse under the control of master control system in coil
Current excitation signal excites the sound wave in fluid；Step 2, after fixed ultrasonic transmission time, the multiple probes of synchronous acquisition are connect
The acoustical signal received；The collected data of Multi-path synchronous are carried out analytical calculation, utilize the propagation of sound wave by step 3, master control system
Rule obtains the location information of gas hydrates pore media.
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