CN103244104A - Method for extracting sleeve wave attenuation rate through dispersion correction - Google Patents

Abstract

The invention belongs to the field of applied geophysical well logging and particularly relates to a method for extracting sleeve wave attenuation rate through dispersion correction. The method includes the following steps: 1 calculating a sleeve wave theory dispersion curve; 2 conducting sector cement bond well logging on measuring points and obtaining waveform data corresponding to each sector; 3 conducting dispersion correction on the waveform data transmitted and received by sound wave; 4 extracting waveform attenuation rate after dispersion correction; and 5 repeating step 2, step 3 and step 4 and obtaining attenuation rate of each sector of the measuring points. The method has the advantage of being capable of eliminating effects of dispersion effect in a sleeve on waveform amplitude, obtaining real attenuation rate corresponding to a gluing condition of the sleeve and the cement sheath and greatly reducing attenuation rate calculation errors.

Description

Utilize frequency dispersion to proofread and correct the method for extracting the casing wave attenuation rate

Technical field

The invention belongs to applied geophysics well logging field, particularly, relate to a kind of method of extracting the casing wave attenuation rate; Be used for eliminating the influence that sleeve pipe frequency dispersion effect causes wave-shape amplitude, accurately obtain the corresponding attenuation rate of the glued situation of sleeve pipe and cement sheath.

Background technology

Aspect primary cement evaluation, sector cement bond logging unit (SBT, Segmented Bond Tool) measuring system is to comprise 6 angle block quantitative measurment cementing situations of whole well around mode.Core component is made up of six slide plates, and a soic wave transmitting energy converter (T) and a sound wave receiving transducer (R) are installed on each slide plate, forms two pair receipts compensation sleeve wave attenuation rate measuring systems of sending out that 6 sector zigzag shapes are arranged jointly.Utilize sound wave through the energy loss in space between two sound wave receiving transducers, realize the attenuation rate measurement.

The attenuation rate result that the sector cement bond logging unit is calculated has got rid of the influence of soic wave transmitting energy converter emissive porwer and the sensitivity of sound wave receiving transducer, but exist than mistake between the attenuation rate that calculates and the Trueattenuation rate, causing this reasons of error is that above-mentioned processing method does not consider that sound wave is along the frequency dispersion effect in the sleeve pipe communication process.The preliminary wave that sector cement bond logging unit (SBT) produces in sleeve pipe is a kind of stretching ripple (or being called symmetric form Lamb ripple), stronger dispersion phenomenon is arranged in the working frequency range of instrument, and this frequency dispersion effect makes wave amplitude reduce because of the waveform disperse, produces the decay of apparent wave amplitude.Therefore, should the waveform that receiver receives be removed because the frequency dispersion effect causes the part of wave-shape amplitude decay, could really obtain sleeve pipe and the corresponding attenuation rate of the glued situation of cement sheath.The sector cement bond logging unit device of present domestic development (being called for short CBMT, Cement Bond Mapping Tool) can record the all-wave waveform that pastes the borehole wall, for the invention provides waveform is done the initial data that frequency dispersion is proofreaied and correct.

Summary of the invention

For overcoming the defective of prior art, the invention provides a kind of frequency dispersion of utilizing and proofread and correct the method for extracting the casing wave attenuation rate, the frequency dispersion effect is to the influence of wave-shape amplitude in the elimination sleeve pipe, get rid of the apparent wave amplitude decay part that dispersion phenomenon causes, obtain the corresponding attenuation rate of the glued situation of sleeve pipe and cement sheath.

For achieving the above object, the present invention is by the following technical solutions:

A kind of frequency dispersion of utilizing is proofreaied and correct the method for extracting the casing wave attenuation rate, it is characterized in that, comprises the steps:

Step 1 is calculated the theoretical dispersion curve of casing wave

Step 2 is carried out the sector cement bond log to survey mark, obtains the Wave data of each sector correspondence

Step 3, the Wave data that emission receives to sound wave are carried out frequency dispersion and are proofreaied and correct

Step 4 is extracted the attenuation rate that frequency dispersion is proofreaied and correct the back waveform

Step 5, repeating step two, step 3 and step 4, the attenuation rate of each sector of acquisition survey mark.

Preferably, step 1 is specific as follows:

(1), sets up the cased well model according to mud, sleeve pipe, cement and formation parameter

According to parameters,acoustic and the thickness of mud, sleeve pipe, cement and the stratum media of production well, set up the cased well model of planar interface layered medium

(2), adopt the gloomy alternative manner of newton-pressgang, the theoretical dispersion curve of casing wave of calculating planar interface layered medium cased well model.

Preferably, step 2 is specific as follows:

Wave data according to the sector cement bond log is measured obtains the corresponding Wave data in each sector on the survey mark.

Preferably, step 3 is as follows: the theoretical dispersion curve of the casing wave that utilizes step 1 to calculate, the four train wave graphic data of handling in the step 2 on the sector that obtains are carried out the frequency dispersion correction: respectively at up transmitter emission, far, nearly spacing the receiver Wave data and the emission of downlink device that receive, the frequency dispersion of carrying out of the Wave data that far away, nearly receiver receives is proofreaied and correct;

The essence that frequency dispersion is proofreaied and correct is exactly ripple to be propagated the phase place variation that produces with V (ω) be corrected to V ₀Go in situation during propagation, the wave spectrum after obtaining proofreading and correct is:

${{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">A</figure-callout>}}_1}^{\&prime;}(\mathrm{\&omega;},D_1)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00003180786700032.png,HDA00003180786700051.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}=A_1(\mathrm{\&omega;},D_1)e^{\mathrm{i\&omega;}[{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V_0-{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V\left(\mathrm{\&omega;}\right)]}$

Wherein, A ₁' (ω, D ₁) be the complex wave spectrum after frequency dispersion is proofreaied and correct, A ₀Be receiving range D ₁=0 o'clock reception wave spectrum, i are plural imaginary units, and V (ω) is the dispersion curve with stretching ripple in the sleeve pipe of frequencies omega variation.

Preferably, institute sector cement bond logging unit utensil has two pair receipts compensation sleeve wave attenuation rate measuring systems of sending out that six sector zigzag shapes are arranged; Compensation sonic system on sector has a up soic wave transmitting energy converter, a descending soic wave transmitting energy converter, two sound wave receiving transducers; Four train wave graphic data on each sector are respectively up soic wave transmitting energy converter emissions, two two train wave graphic data that the sound wave receiving transducer receives; Descending soic wave transmitting energy converter emission, two two train wave graphic data that the sound wave receiving transducer receives.

Preferably, the frequency step in the frequency spectrum of the frequency step that adopts when calculating dispersion curve and actual measurement waveform is consistent.

With respect to prior art, the present invention has following beneficial effect: can eliminate the influence that the frequency dispersion effect causes wave-shape amplitude in the sleeve pipe, obtain the corresponding Trueattenuation rate of the glued situation of sleeve pipe and cement sheath, significantly reduce the error that attenuation rate is calculated.

Description of drawings

Fig. 1 is that the present invention utilizes frequency dispersion to proofread and correct the method workflow diagram that extracts the casing wave attenuation rate;

Fig. 2 is theoretical cased well model schematic diagram;

Fig. 3 is the compensation sonic system structural representation on sector of sector cement bond logging unit;

Fig. 4 is the theoretical dispersion curve figure of the casing wave of different casing wall thickness correspondences;

Fig. 5 is the theoretical attenuation curve figure of the casing wave of different casing wall thickness correspondences;

Fig. 6 is that casing wall thickness is 0.5in, comparison of wave shape figure before and after frequency dispersion was proofreaied and correct when spacing was 0.3m and 0.6m;

Fig. 7 is the frequency dispersion correction signal that carries out of the method for utilizing frequency dispersion proofread and correct to extract the casing wave attenuation rate according to the present invention and the Hilbert transform envelope diagram of correction signal;

Fig. 8 is that the method for utilizing frequency dispersion proofread and correct to extract the casing wave attenuation rate according to the present invention is extracted the attenuation rate of the different casing thicknesses that Hilbert envelope peak obtains and the comparison diagram of theoretical value.

The specific embodiment

As shown in Figure 1, utilize frequency dispersion to proofread and correct the method for extracting the casing wave attenuation rate, comprise the steps:

Step 1, the theoretical dispersion curve of calculating casing wave

(1), sets up the cased well model according to mud, sleeve pipe, cement and formation parameter

According to parameters,acoustic and the thickness of mud, sleeve pipe, cement and the stratum media of production well, set up the cased well model of planar interface layered medium, as shown in Figure 2, r is the well radius, and d is casing thickness, and h is cement thickness.

(2), adopt the gloomy alternative manner of newton-pressgang, the theoretical dispersion curve of casing wave of calculating planar interface layered medium cased well model

Set up displacement potential function (1) formula, find the solution the dispersion equation formula (3) that obtains cased well in conjunction with Acoustic Boundary Conditions (2) formula.

$\left\{\begin{array}{c}\mathrm{\&Phi;}=\underset{-\&infin;}{\overset{+\&infin;}{\&Integral;}}\left[{\mathrm{Ae}}^{{\mathrm{ik}}_{z}z}\right]e^{{\mathrm{ik}}_{x}x}{\mathrm{dk}}_x\\ X=\underset{-\&infin;}{\overset{+\&infin;}{\&Integral;}}[{\mathrm{Be}}^{{-\mathrm{ik}}_{c}z}+{\mathrm{Ce}}^{{\mathrm{ik}}_{c}z}]e^{{\mathrm{ik}}_{x}x}{\mathrm{dk}}_x\\ \mathrm{\&Gamma;}=\underset{-\&infin;}{\overset{+\&infin;}{\&Integral;}}[{\mathrm{De}}^{{-\mathrm{ik}}_{s}z}+{\mathrm{Ee}}^{{\mathrm{ik}}_{s}z}]e^{{\mathrm{ik}}_{x}x}{\mathrm{dk}}_x\end{array}\right.---\left(1\right)$

Wherein, Φ is the displacement of fluid potential function, and Χ is the P-wave displacement potential function, and Γ is shear wave displacement potential function, k _xBe axial wave number, Be radially wave number of fluid,

Be radially wave number of compressional wave,

It is radially wave number of shear wave.I is plural imaginary unit, and ω is angular frequency, v _fBe fluid velocity, v _cBe velocity of longitudinal wave, v _sBe shear wave velocity, z is radial distance, and A, B, C, D and E are undetermined coefficients.

$\left\{\begin{array}{c}u=u_f\\ {\mathrm{\&sigma;}}_{\mathrm{rr}}={\mathrm{\&sigma;}}_{\mathrm{rrf}}\\ {\mathrm{\&sigma;}}_{\mathrm{rz}}=0\\ {\mathrm{\&sigma;}}_{\mathrm{r\&theta;}}=0\end{array}\right.---\left(2\right)$

Wherein, u is radial displacement, u _fBe the radial displacement of fluid, σ _RrBe radial normal stress, σ _RrfBe the radial normal stress of fluid, σ _RzAnd σ _{R θ}It is shear stress.

D(k _x,ω)=|M(k _x,ω)|=0 (3)

Wherein, M (k _x, ω) be the matrix equation that obtains according to (1) formula and (2) formula.

Utilize the gloomy alternative manner of newton-pressgang to find the solution the root of formula (3), thereby obtain casing wave along with the velocity amplitude of change of frequency, obtain casing wave along with the rate curve of change of frequency, be the theoretical dispersion curve of casing wave.

The frequency step that adopts when calculating dispersion curve is consistent with the frequency step in the frequency spectrum of actual measurement waveform.

Step 2, survey mark is carried out the sector cement bond log, obtain the Wave data of each sector correspondence

Wave data according to the sector cement bond log is measured obtains the corresponding Wave data in each sector on the survey mark.During measurement, the Wave data that a plurality of (can be designated as n) sector is arranged on survey mark, each sector is to there being 4 train wave graphic data, following frequency dispersion trimming process is that 4 train wave graphic data on the sector are proofreaied and correct, so should accurately obtain the corresponding Wave data in each sector from the 4n train wave graphic data of survey mark in this step.

The sector cement bond logging unit device of domestic development (being called for short CBMT) has two two compensation sleeve wave attenuation rate measuring systems of receiving that six sector zigzag shapes are arranged.Compensation sonic system structure on sector as shown in Figure 3, T1 is up soic wave transmitting energy converter, and the descending soic wave transmitting energy converter of T4, R2, R3 are that the sound wave receiving transducer is (when launching with respect to T1, R2 belongs to nearly spacing sound wave receiving transducer, and R3 belongs to spacing sound wave receiving transducer far away; When launching with respect to T4, R2 belongs to spacing sound wave receiving transducer far away, and R3 belongs to nearly spacing sound wave receiving transducer).

Four train wave graphic data on each sector are respectively soic wave transmitting energy converter T1 emissions, the two train wave graphic data that nearly spacing sound wave receiving transducer R2 and spacing sound wave receiving transducer R3 far away receive; Soic wave transmitting energy converter T4 emission, the two train wave graphic data that nearly spacing sound wave receiving transducer R3 and spacing sound wave receiving transducer R2 far away receive.

Step 3, the Wave data that emission receives to sound wave carry out frequency dispersion and proofread and correct

The theoretical dispersion curve of the casing wave that utilizes step 1 to calculate carries out the frequency dispersion correction to the four train wave graphic data of handling in the step 2 on the sector that obtains.At up emitter emission, Wave data and downlink device that far away, nearly spacing receiver receives are launched respectively, and the frequency dispersion of carrying out of the Wave data that far away, nearly receiver receives is proofreaied and correct.

(1), up soic wave transmitting energy converter T1

To soic wave transmitting energy converter T1 emission, the two train wave shapes that nearly spacing sound wave receiving transducer R2 and spacing sound wave receiving transducer R3 far away receive are carried out frequency dispersion and are proofreaied and correct, and the frequency dispersion trimming process is as follows:

The soic wave transmitting energy converter distance of adjusting the distance is D ₁The Wave data that receives of nearly spacing sound wave receiving transducer R2 carry out Fast Fourier Transform (FFT), the time-domain waveform signal is transformed into the frequency-domain waveform frequency spectrum, obtaining frequency domain plural number wave spectrum is A ₁(ω, D ₁).For the frequency dispersion stretching ripple of propagating along sleeve pipe, this complex wave spectrum can show be:

$A_1(\mathrm{\&omega;},D_1)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V\left(\mathrm{\&omega;}\right)}---\left(4\right)$

Wherein, A ₀Be receiving range D ₁=0 o'clock reception wave spectrum, i are plural imaginary units, and V (ω) is the dispersion curve with stretching ripple in the sleeve pipe of frequencies omega variation, and this variation has caused the disperse of waveform in the time domain just.V (ω) obtains in step 1, when the parameters,acoustic on uncertain cement and stratum, can utilize the dispersion curve under the cased well model that 3 layers of medium of mud, sleeve pipe and mud form.

Therefore, the essence of frequency dispersion correction is exactly ripple to be propagated the phase place variation that produces with V (ω) be corrected to V ₀Go in situation during propagation, the wave spectrum after obtaining proofreading and correct is:

${{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">A</figure-callout>}}_1}^{\&prime;}(\mathrm{\&omega;},D_1)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00003180786700032.png,HDA00003180786700051.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}=A_1(\mathrm{\&omega;},D_1)e^{\mathrm{i\&omega;}[{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V_0-{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V\left(\mathrm{\&omega;}\right)]}---\left(5\right)$

Wherein, A ₁' (ω, D ₁) be the complex wave spectrum after frequency dispersion is proofreaied and correct.Constant velocity V ₀Get the low frequency value 5432.5m/s(of V (ω) as seen from Figure 4, the dispersion curve V (ω) of the different thickness of pipe is the same velocity amplitude of convergence).

The soic wave transmitting energy converter distance of adjusting the distance is D ₂The Wave data that receives of spacing sound wave receiving transducer far away carry out Fast Fourier Transform (FFT), the time-domain waveform signal is transformed into the frequency-domain waveform frequency spectrum, obtaining frequency domain plural number wave spectrum is A ₂(ω, D ₂).This complex wave spectrum can be shown:

$A_2(\mathrm{\&omega;},D_2)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/V\left(\mathrm{\&omega;}\right)}---\left(6\right)$

Wave spectrum after the correction is:

${A_2}^{\&prime;}(\mathrm{\&omega;},D_2)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00003180786700032.png,HDA00003180786700051.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}=A_2(\mathrm{\&omega;},D_2)e^{\mathrm{i\&omega;}[{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/V_0-{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/V\left(\mathrm{\&omega;}\right)]}---\left(7\right)$

Wherein, A ₂' (ω, D ₂) be the complex wave spectrum after frequency dispersion is proofreaied and correct.Wave data A after at last the twice frequency dispersion of soic wave transmitting energy converter T1 emission being proofreaied and correct ₁' (ω, D ₁) and A ₂' (ω, D ₂) make Fast Fourier Transform Inverse, obtain the Wave data after frequency dispersion is proofreaied and correct on the time domain.

(2), descending soic wave transmitting energy converter T4

To soic wave transmitting energy converter T4 emission, the two train wave shapes that nearly spacing sound wave receiving transducer R3 and spacing sound wave receiving transducer R2 far away receive are carried out frequency dispersion and are proofreaied and correct, and the frequency dispersion trimming process is as follows:

The soic wave transmitting energy converter distance of adjusting the distance is D ₁The Wave data that receives of nearly spacing sound wave receiving transducer R3 carry out Fast Fourier Transform (FFT), the time-domain waveform signal is transformed into the frequency-domain waveform frequency spectrum, obtaining frequency domain plural number wave spectrum is A ₃(ω, D ₁).This complex wave spectrum can be shown:

$A_3(\mathrm{\&omega;},D_1)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V\left(\mathrm{\&omega;}\right)}---\left(8\right)$

Wave spectrum after the correction is:

${A_3}^{\&prime;}(\mathrm{\&omega;},D_1)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00003180786700032.png,HDA00003180786700051.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}=A_3(\mathrm{\&omega;},D_1)e^{\mathrm{i\&omega;}[{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V_0-{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">D</figure-callout>}}_1/V\left(\mathrm{\&omega;}\right)]}---\left(9\right)$

Wherein, A ₃' (ω, D ₁) be the complex wave spectrum after frequency dispersion is proofreaied and correct.

The soic wave transmitting energy converter distance of adjusting the distance is D ₂The Wave data that receives of nearly spacing sound wave receiving transducer R2 carry out Fast Fourier Transform (FFT), the time-domain waveform signal is transformed into the frequency-domain waveform frequency spectrum, obtaining frequency domain plural number wave spectrum is A ₄(ω, D ₂).This complex wave spectrum can be shown:

$A_2(\mathrm{\&omega;},D_2)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/V\left(\mathrm{\&omega;}\right)}---\left(10\right)$

Wave spectrum after the correction is:

${A_4}^{\&prime;}(\mathrm{\&omega;},D_2)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00003180786700032.png,HDA00003180786700051.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}=A_4(\mathrm{\&omega;},D_2)e^{\mathrm{i\&omega;}[{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/V_0-{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/V\left(\mathrm{\&omega;}\right)]}---\left(11\right)$

Wherein, A ₄' (ω, D ₂) be the complex wave spectrum after frequency dispersion is proofreaied and correct.

Wave data A after at last the twice frequency dispersion of soic wave transmitting energy converter T4 emission being proofreaied and correct ₃' (ω, D ₁) and A ₄' (ω, D ₂) make Fast Fourier Transform Inverse, obtain the Wave data after frequency dispersion is proofreaied and correct on the time domain.

The attenuation rate that step 4, extraction frequency dispersion are proofreaied and correct the back waveform

The attenuation rate that sector cement bond logging unit (be called for short CBMT) is calculated is by reading the wave-shape amplitude that sound wave receiving transducer far away and nearly sound wave receiving transducer receive, and utilizes formula (12) to calculate:

α=(-20/D)lg(A ₁/A ₂) (12)

Wherein, α is the acoustic attenuation rate, A ₁Be the wave-shape amplitude that spacing sound wave receiving transducer far away receives, A ₂Be the wave-shape amplitude that nearly spacing sound wave receiving transducer receives, D is the distance between receiving transducer R2 and the R3.

It is as follows to read the waveforms amplitude method: the Wave data after earlier frequency dispersion being proofreaied and correct is done Hilbert transform, reads first peak value of Hilbert envelope then.

In the four train wave graphic data that above-mentioned frequency dispersion is proofreaied and correct, soic wave transmitting energy converter T1 emission, the two train wave graphic data that nearly spacing sound wave receiving transducer R2 and spacing sound wave receiving transducer R3 far away receive are made the Xi Er baud conversion, and the peak value of first envelope is designated as A respectively behind the Xi Er baud conversion ₁₂And A ₁₃, extract after then frequency dispersion is proofreaied and correct attenuation rate α ₁For:

α ₁=(-20/D)lg(A ₁₃/A ₁₂) (13)

In like manner, the emission of T4 soic wave transmitting energy converter, the two train wave shapes that nearly spacing sound wave receiving transducer R3 and spacing sound wave receiving transducer R2 far away receive are made the Xi Er baud conversion, and the peak value of first envelope behind the Xi Er baud conversion is designated as A respectively ₄₃And A ₄₂, extract after then frequency dispersion is proofreaied and correct attenuation rate α ₂For:

α ₂=(-20/D)lg(A ₄₃/A ₄₂) (14)

The attenuation rate result who utilizes two transmitters to calculate, ask for the attenuation rate after the compensation:

$\mathrm{<figure-callout\; id="1"\; label="ATC"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">ATC</figure-callout>}1=\frac{{\mathrm{\&alpha;}}_1+{\mathrm{\&alpha;}}_2}{2}-\mathrm{ATSP}---\left(15\right)$

Wherein, ATSP is the sound wave amplitude fading that how much diffusions cause, value is 3/D, and ATC1 is the attenuation rate after compensating.

When the attenuation rate ATC1 that calculate this moment has got rid of soic wave transmitting energy converter emissive porwer and sound wave receiving transducer sensitivity influence, also eliminated the influence that the frequency dispersion effect causes wave-shape amplitude.

The attenuation rate of each sector of step 5, acquisition survey mark

The processing procedure of repeating step two, step 3 and step 4 obtains the attenuation rate on other each sector on the survey mark, obtains n attenuation rate of n sector correspondence at last.

For the method performing step that utilizes frequency dispersion to proofread and correct extraction casing wave attenuation rate provided by the invention is described, further specify below by embodiment.

At first, calculate the theoretical dispersion curve of cased well according to step 1.Described according to step 1, the theoretical cased well model according to setting up utilizes the model parameter in the table 1, find the solution the cased well dispersion equation by the gloomy alternative manner of newton-pressgang, calculate the theoretical dispersion curve of cased well, as shown in Figure 4, shown the dispersion curve under 6 casing thicknesses among the figure.As can be seen from the figure, along with the increase of casing wall thickness, dispersion phenomenon is more serious.Be that casing wall thickness is more big, the frequency dispersion effect is more serious to the decay that wave-shape amplitude causes, and the attenuation rate that calculates also more departs from actual value.When calculating casing wave along with the velocity amplitude of change of frequency, also simultaneously can obtain casing wave along with the pad value of change of frequency, the rate curve along with change of frequency that this method is obtained is called theoretical attenuation curve, as shown in Figure 5.Shown the theoretical attenuation curve under 6 casing thicknesses among the figure, visible casing thickness is more thick, and is more serious in the working frequency range decay of logger.

The waveform that the sector cement bond logging unit measures is the multifrequency signal with certain bandwidth, attenuation rate difference under the different frequency is obvious as seen from Figure 5, therefore needs to obtain to use at the sector cement bond logging unit the theoretical attenuation rate of the frequency spectrum weighting of frequency range.The step of asking for the attenuation rate of frequency spectrum weighting is: the corresponding amplitude spectrum of waveform after at first frequency dispersion being proofreaied and correct is made normalized, choose the spectrum value of each Frequency point correspondence then as weight coefficient, utilize formula (4) to be weighted with the attenuation rate under the corresponding frequencies:

$K=\frac{{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">B</figure-callout>}}_1\&times;{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">f</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">B</figure-callout>}}_2\&times;{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="B"\; filenames="HDA00003180786700032.png,HDA00003180786700052.png"\; state="\{\{state\}\}">B</figure-callout>}}_3\&times;{\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="HDA00003180786700032.png,HDA00003180786700052.png"\; state="\{\{state\}\}">f</figure-callout>}}_3+{\mathrm{<figure-callout\; id="4"\; label="B"\; filenames="HDA00003180786700041.png,HDA00003180786700051.png"\; state="\{\{state\}\}">B</figure-callout>}}_4\&times;{\mathrm{<figure-callout\; id="4"\; label="f"\; filenames="HDA00003180786700041.png,HDA00003180786700051.png"\; state="\{\{state\}\}">f</figure-callout>}}_4+...}{{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA00003180786700032.png"\; state="\{\{state\}\}">f</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA00003180786700032.png,HDA00003180786700041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="HDA00003180786700032.png,HDA00003180786700052.png"\; state="\{\{state\}\}">f</figure-callout>}}_3+{\mathrm{<figure-callout\; id="4"\; label="f"\; filenames="HDA00003180786700041.png,HDA00003180786700051.png"\; state="\{\{state\}\}">f</figure-callout>}}_4+...}---\left(16\right)$

Wherein, K is the theoretical attenuation rate after the frequency spectrum weighted average, B _iBe the attenuation rate of different frequency correspondence, f _iIt is the amplitude spectrum of different frequency correspondence after the normalization.

Table 1 cased well model parameter

Parameter	Velocity of longitudinal wave (m/s)	Shear wave velocity (m/s)	Density (g/cm 3)
				Water	1500	-	1.0
Sleeve pipe	5930	3250	7.8
				Water	1500	-	1.0

Secondly, read in CBMT Wave data on the sector of survey mark.The CBMT Wave data that present embodiment reads in is replaced by the waveform that theoretical numerical simulation obtains.Set up above-mentioned cased well model, model parameter is as shown in table 1, and the work dominant frequency of instrument is 80kHz.Utilize real axis integration method numerical simulation to obtain the waveform of receiver far away and nearly receiver reception.Fig. 6 has provided the twice waveform under the cased well model shown in the table 1, and the distance of nearly receiver and receiver range transmission probe far away is respectively 0.3m and 0.6m, and casing wall thickness is 0.5in, the original waveform that this twice Wave data is proofreaied and correct as frequency dispersion in the present embodiment.

Then, nearly receiver and receiver reception waveform far away are carried out the frequency dispersion correction.Fig. 6 has provided the comparison diagram that far away, nearly two train wave graphic data frequency dispersions are proofreaied and correct front and back.As can be seen from Figure 6, obviously increase the whole Phase advance of waveform through the waveform casing wave first wave amplitude after the frequency dispersion correction; From the relative amplitude that waveform increases, the casing wave first wave amplitude increase at spacing 0.6m place is bigger.The result of Fig. 6 shows: frequency dispersion is proofreaied and correct the apparent attenuation rate eliminated the wave amplitude that frequency dispersion causes effectively, makes it more can reflect the corresponding attenuation change of sleeve pipe and cement sheath gluing situation.

At last, extract the attenuation rate that frequency dispersion is proofreaied and correct the back waveform.Waveform after earlier frequency dispersion being proofreaied and correct carries out Hilbert transform, obtains the Hilbert envelope of waveform, as shown in Figure 7.Read first peak value of waveform Hilbert envelope, utilize decay formula (13) to obtain corresponding attenuation rate.

Fig. 8 has provided the contrast of the attenuation rate (discrete point among the figure ●) that the attenuation rate (the discrete point ★ among the figure) of utilizing the present invention to extract and former method extract, solid black lines among the figure is frequency theoretical attenuation rate under the different casing thicknesses when being 80kHz, and red solid line is according to the theoretical attenuation rate after frequency spectrum (waveform frequency spectrum) weighting.As shown in Figure 8, the attenuation rate of utilizing the present invention to calculate is compared with former method more and can more can be reflected the corresponding attenuation change of the glued situation of sleeve pipe and cement sheath under actual conditions, thereby superiority of the present invention has been described near theoretical attenuation rate.

Claims (6)

1. one kind is utilized frequency dispersion to proofread and correct the method for extracting the casing wave attenuation rate, it is characterized in that, comprises the steps:

Step 1 is calculated the theoretical dispersion curve of casing wave

Step 2 is carried out the sector cement bond log to survey mark, obtains the Wave data of each sector correspondence

Step 3, the Wave data that emission receives to sound wave are carried out frequency dispersion and are proofreaied and correct

Step 4 is extracted the attenuation rate that frequency dispersion is proofreaied and correct the back waveform

Step 5, repeating step two, step 3 and step 4, the attenuation rate of each sector of acquisition survey mark.

2. the frequency dispersion of utilizing according to claim 1 is proofreaied and correct the method for extracting the casing wave attenuation rate, it is characterized in that step 1 is specific as follows:

(1), sets up the cased well model according to mud, sleeve pipe, cement and formation parameter

According to parameters,acoustic and the thickness of mud, sleeve pipe, cement and the stratum media of production well, set up the cased well model of planar interface layered medium

(2), adopt the gloomy alternative manner of newton-pressgang, the theoretical dispersion curve of casing wave of calculating planar interface layered medium cased well model.

3. proofread and correct the method for extracting the casing wave attenuation rate according to the described frequency dispersion of utilizing of claim 1-2, it is characterized in that step 2 is specific as follows:

Wave data according to the sector cement bond log is measured obtains the corresponding Wave data in each sector on the survey mark.

4. proofread and correct the method for extracting the casing wave attenuation rate according to the described frequency dispersion of utilizing of claim 1-3, it is characterized in that, the theoretical dispersion curve of the casing wave that utilizes step 1 to calculate, the four train wave graphic data of handling in the step 2 on the sector that obtains are carried out the frequency dispersion correction: respectively at up transmitter emission, far, nearly spacing the receiver Wave data and the emission of downlink device that receive, the frequency dispersion of carrying out of the Wave data that far away, nearly receiver receives is proofreaied and correct;

The essence that frequency dispersion is proofreaied and correct is exactly ripple to be propagated the phase place variation that produces with V (ω) be corrected to V ₀Go in situation during propagation, the wave spectrum after obtaining proofreading and correct is:

${A_1}^{\&prime;}(\mathrm{\&omega;},D_1)=A_0\left(\mathrm{\&omega;}\right)e^{\mathrm{i\&omega;}{D}_1/V_0}=A_1(\mathrm{\&omega;},D_1)e^{\mathrm{i\&omega;}[D_1/V_0-D_1/V\left(\mathrm{\&omega;}\right)]}$

Wherein, A ₁' (ω, D ₁) be the complex wave spectrum after frequency dispersion is proofreaied and correct, A ₀Be receiving range D ₁=0 o'clock reception wave spectrum, i are plural imaginary units, and V (ω) is the dispersion curve with stretching ripple in the sleeve pipe of frequencies omega variation.

5. proofread and correct the method for extracting the casing wave attenuation rate according to the described frequency dispersion of utilizing of claim 1-4, it is characterized in that, two two compensation sleeve wave attenuation rate measuring systems of receiving that institute's sector cement bond logging unit utensil has six sector zigzag shapes to arrange; Compensation sonic system on sector has a up soic wave transmitting energy converter, a descending soic wave transmitting energy converter, two sound wave receiving transducers; Four train wave graphic data on each sector are respectively up soic wave transmitting energy converter emissions, two two train wave graphic data that the sound wave receiving transducer receives; Descending soic wave transmitting energy converter emission, two two train wave graphic data that the sound wave receiving transducer receives.

6. proofread and correct the method for extracting the casing wave attenuation rate according to the described frequency dispersion of utilizing of claim 1-5, it is characterized in that the frequency step that adopts is consistent with the frequency step in the frequency spectrum of actual measurement waveform when calculating dispersion curve.

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