A kind of method of inversing soft ground horizontal wave velocity by leaky mode waves
Technical field
The invention belongs to the applied geophysics acoustic logging, when particularly relating to the serious soft formation exploration of super large hole diameter, loose shallow-layer or hole enlargement, the method for utilizing the leakage mode ripple of frequency dispersion to come inverting stratum shear wave velocity.
Background technology
Development along with oil exploration and development technique, the equal an urgent demand acoustic logging in field such as seismic prospecting and drilling engineering provides stratum shear wave velocity section accurately, as the inverting of earthquake elastic wave impedance, the processing of earthquake AVO attribute, drilling stratum pressure prediction and borehole wall stability evaluation.At present, the wellhole acoustic logging provides the effective means of continuous stratum shear wave velocity section.But the stratum shear wave velocity less than well in the soft formation of the mud velocity of sound, the symmetrical monopole sound source of traditional acoustic logging can not excite the shear wave on stratum, but the Stoneley wave inverting stratum shear wave velocity that utilizes one pole to excite.In recent years, developed asymmetrical sound source of the dipole, realized measuring the dipole acoustic logging technique of any stratum shear wave velocity by exciting wellhole beam mode ripple.During actual the well logging, the excitation intensity of one pole Stoneley wave and DIPOLE FLEXURAL WAVES and Dispersion all are subjected to parameter influences such as formation properties and hole diameter serious, even at big hole diameter, loose shallow-layer or the more serious soft formation of hole enlargement, doublet source often can not excite bending wave, the one pole sound source can not excite Stoneley wave, shown in 430~435 meters and 446~452 meters well sections among Fig. 1.Therefore, at big hole diameter, loose shallow-layer or the more serious soft formation of hole enlargement,, all can't guarantee to provide the shear wave velocity on stratum from the angle of existing dipole acoustic log commercial measurement and the angle of one pole Stoneley wave inverting.
From a large amount of on-the-spot multipoles (one pole and dipole) array sonic log data, find the shear wave velocity that the stratum can't be directly measured in big hole diameter, loose shallow-layer or the more serious soft formation dipole well logging of hole enlargement.Set up wellhole multipole array acoustic log theoretical model, the one pole of numerical simulation study soft formation, dipole acoustic log response characteristic show, serious soft formation one pole, the dipole of hole enlargement all excites the bigger leakage mode ripple of amplitude in theory, and the one pole Stoneley wave and the DIPOLE FLEXURAL WAVES amplitude that are used to measure shear wave velocity are very little, even complete obiteration, as shown in Figures 2 and 3.The leakage mode ripple of soft formation one pole, dipole excitation is a kind of frequency dispersion mode wave, and promptly phase velocity changes with frequency change, as shown in Figure 4.The Dispersion of leakage mode ripple mainly is sensitive to the mud velocity of sound and stratum shear wave velocity in stratum velocity of longitudinal wave, the well, and as shown in Figure 5, wherein, this mode wave reaches 10% to the sensitivity of stratum shear wave velocity.Therefore, in the soft formation situation that one pole Stoneley wave and DIPOLE FLEXURAL WAVES all do not excite, can consider shear wave velocity with the Dispersion inverting soft formation of the leakage mode ripple of relatively stable one pole or dipole.
Summary of the invention
The object of the present invention is to provide a kind of method of inversing soft ground horizontal wave velocity by leaky mode waves, the technical problem that the leakage mode ripple that utilizes frequency dispersion with solution carries out inverting to the shear wave velocity of the more serious soft formation of big hole diameter, loose shallow-layer or hole enlargement.
The objective of the invention is Windows environment, utilize Microsoft VC++ SDK, realize in the following way based on the microcomputer more than the internal memory 256M:
The Wave data of the leakage mode ripple of being measured by multipole array sonic log instrument one pole or dipole mode of operation of at first, that hole enlargement is a serious depth point of soft formation well section and stratum velocity of longitudinal wave, hole diameter, the mud velocity of sound, the mud density parameter that this corresponding depth point is measured by conventional logging input to several memories of computer.
Secondly, utilize the Matrix Pencil method of frequency spectrum weighting correlation method, Prony method, correction or the array waveform dispersion curve extractive technique of homomorphism processing method, monopole array waveform or dipole array waveform extracting by soft formation go out leakage mode phase velocity of wave dispersion curve, and the main energy frequency range of definite one pole leakage mode ripple or dipole leakage mode ripple.
Once more, liquid-filled well bore sound field theory according to people such as Kurkjian proposition, set up wellhole multipole array acoustic log model, stratum velocity of longitudinal wave in the model, density, hole diameter, the mud velocity of sound and mud density are measured known by traditional logging method, change the stratum shear wave velocity with iterative method or parabolic method dispersion equation D (f by theory, k, V
s, V
c, V
f, ρ, ρ
f, R)=0 solve soft formation one pole or dipole leakage mode phase velocity of wave dispersion curve with frequency change, in the formula, k=
2π f/V
pBe wave number, f-frequency, V
p-phase velocity, V
s-stratum shear wave velocity, V
c-stratum velocity of longitudinal wave, V
fThe mud velocity of sound in the-well, ρ-density of earth formations, ρ
f-mud density, R-well radius.
Then, in one pole or the main energy frequency range of dipole leakage mode ripple, calculate the variance sum of the leakage mode phase velocity of wave of theoretical down leakage mode phase velocity of wave of calculating of Different Strata shear wave velocity and the extraction of on-the-spot array waveform information, obtain the variance curve that changes with the stratum shear wave velocity.Utilize Lagrangian method to the variance curve precise interpolation, the stratum shear wave velocity of correspondence is the stratum shear wave velocity that this depth point inverting obtains when determining variance and be zero.
At last, utilize above-mentioned inverting flow process that the serious soft formation well section of hole enlargement is handled continuously, obtain the stratum shear wave velocity result map of soft formation well section, result map is presented on the display, or print and publish picture.
The present invention has overcome existing multipole array sonic log instrument can not directly be measured the stratum shear wave velocity in the serious loose soft formation well section of hole enlargement shortcoming, utilize the leakage mode ripple of frequency dispersion in one pole or the dipole array waveform to come inverting stratum shear wave velocity, this method has been widened the application of wellhole acoustic logging in oil exploration and development process, has improved its using value.
Description of drawings
Fig. 1 is the waveform information and the contrast schematic diagram of loose shallow-layer well section one pole and dipole acoustic log.
Fig. 2 is the array time domain waveform schematic diagram of the theoretical monopole acoustic logging of synthesizing of soft formation.Fig. 3 is the array time domain waveform schematic diagram that the theoretical synthetic dipole acoustic of soft formation is logged well.
Fig. 4 is the leakage mode phase velocity of wave dispersion curve figure that soft formation monopole sound source excites.
Fig. 5 is the sensitivity curves figure of soft formation monopole leakage mode ripple to the mud velocity of sound in stratum shear wave velocity, velocity of longitudinal wave and the well.
Fig. 6 is the FB(flow block) according to the leakage mode ripple inverting stratum shear wave velocity method of a kind of frequency dispersion provided by the present invention.
Fig. 7 is the monopole array time domain waveform schematic diagram of the theoretical soft formation that synthesizes.
Fig. 8 is the spectrum diagram of soft formation monopole array waveform correspondence.
Fig. 9 utilizes the frequency spectrum weighted, coherent figure of the leakage mode ripple that frequency spectrum weighting correlation method obtains from monopole array waveform and the dispersion curve (shown in the heavy line) that extracts.
Figure 10 is a wellhole monopole acoustic logging theoretical model schematic diagram.
Figure 11 is leakage mode phase velocity of wave dispersion curve (small circle) and theoretical leakage mode phase velocity of wave dispersion curve (solid line) figure that calculates of adjustment stratum shear wave velocity that extracts from the array waveform according to the method for the invention.
Figure 12 be according to the method for the invention in the main energy frequency range of one pole leakage mode ripple, the Different Strata shear wave velocity is the leakage mode wave dispersion curve and the variance sum of extracting dispersion curve of calculating down, is finally inversed by the schematic diagram of soft formation shear wave velocity when being equalled zero by both variances.
Figure 13 is the stratum shear wave velocity result map that the one pole leakage mode ripple inverting of on-the-spot shallow-layer well section (velocity of longitudinal wave of stratum about 2500 meter per seconds, stratum shear wave velocity about 1200) multipole array sonic log data is drawn according to the method for the invention.
The specific embodiment
The present invention is as follows about the description of the drawings:
Fig. 1 has reflected the waveform information and the contrast of loose shallow-layer well section one pole and dipole acoustic log, and this well section is a soft formation well section, and the 1st road provides natural gamma, bit size and CAL among the figure, and the 2nd, 3 roads provide dipole and one pole waveform respectively.Can find out from the one pole and the dipole waveform of 430~435 meters and 446~452 meters two well sections:, do not excited one pole Stoneley wave and DIPOLE FLEXURAL WAVES because hole enlargement seriously causes one pole and dipole acoustic log data to have only a kind of leakage mode ripple.
Fig. 2 has reflected the array time domain waveform of the theoretical monopole acoustic logging of synthesizing of soft formation, and as can be seen from Figure, this soft formation situation one pole sound source has only excited the leakage mode ripple, does not have Stoneley wave.
Fig. 3 has reflected the array time domain waveform that the theoretical synthetic dipole acoustic of soft formation is logged well, and as can be seen from Figure, this soft formation situation doublet source has only excited the leakage mode ripple, does not have bending wave.
Fig. 4 has reflected the leakage mode phase velocity of wave dispersion curve that soft formation monopole sound source excites, and wherein abscissa is a frequency, and ordinate is a phase velocity.
Fig. 5 reflects the sensitivity curves of soft formation monopole leakage mode ripple to the mud velocity of sound in stratum shear wave velocity, velocity of longitudinal wave and the well, the Dispersion of leakage mode ripple mainly is sensitive to the stratum velocity of longitudinal wave in low-frequency range as can be seen from Figure, and high band mainly is sensitive to the mud velocity of sound in the well.Find simultaneously at the Dispersion of main this mode wave of energy frequency band the stratum shear wave velocity also to be compared sensitivity, sensitivity coefficient reaches about 10%.
Fig. 7 has reflected the monopole array time domain waveform of theoretical synthetic soft formation, wherein has only a kind of leakage mode ripple, does not have Stoneley wave.
Fig. 8 has reflected the frequency spectrum of soft formation monopole array waveform correspondence, and main concentration of energy is at 5 KHzs~10 KHzs.
Describe the present invention in detail below in conjunction with drawings and Examples.
At the serious soft formation of hole enlargement, one pole sound source and doublet source have all excited the leakage mode compressional wave of the very strong frequency dispersion of amplitude, and this mode wave is relatively stable, and are sensitive to very much the stratum shear wave velocity.Therefore, the present invention greater than 30 centimetres, the stratum shear wave velocity soft formation less than 1400 meter per seconds, can adopt one pole leakage mode ripple inverting stratum shear wave velocity and two kinds of specific embodiments of dipole leakage mode ripple inverting stratum shear wave velocity at hole diameter.
Scheme one, the concrete steps of one pole leakage mode ripple inverting stratum shear wave velocity are:
(1). waveform (as shown in Figure 7) data of the leakage mode ripple of being measured by multipole array sonic log instrument monopolar operation pattern of the depth point of soft formation well section that hole enlargement is serious and stratum velocity of longitudinal wave, hole diameter, the mud velocity of sound, the mud density parameter that this corresponding depth point is measured by conventional logging input to several memories of computer.
(2). utilize FFT that monopole array waveform is as shown in Figure 7 done spectrum analysis, obtain the frequency spectrum of per pass waveform, as shown in Figure 8.On this basis, utilize following formula to obtain frequency spectrum weighting correlation diagram, and extract one pole leakage mode phase velocity of wave dispersion curve by index of correlation maximum by the array waveform, as shown in Figure 9,
F is a frequency in the formula, k=2 π f/V
pBe wave number, V
pBe phase velocity; N is the number of receiver, and d is the spacing of adjacent two receivers; X
n(f) be the frequency spectrum of the waveform correspondence of n receiver, complex conjugate is got in " * " expression.
(3). set up wellhole monopole acoustic logging theoretical model, as shown in figure 10, derive theoretical dispersion equation D (f, k, the V of wellhole monopole mode wave according to the inside and outside wave equation of wellhole and fringe conditions
s, V
c, V
f, ρ, ρ
f, R)=0, wherein, k=2 π f/V
pBe wave number, f-frequency, V
p-phase velocity, V
s-stratum shear wave velocity, V
c-stratum velocity of longitudinal wave, V
fThe mud velocity of sound in the-well, ρ-density of earth formations, ρ
f-mud density, R-well radius.Stratum velocity of longitudinal wave, density, hole diameter, the mud velocity of sound and mud density are measured known by other logging methods in the model, change the stratum shear wave velocity and find the solution one pole leakage mode phase velocity of wave dispersion curve by dispersion equation, shown in solid line among Figure 11 with Newton iteration method.
(4). in the main energy frequency range of one pole leakage mode ripple, i.e. 5 KHzs~10 KHzs, calculate the leakage mode phase velocity of wave (solid line among Figure 11) of theoretical calculating under the Different Strata shear wave velocity and the variance sum of the leakage mode phase velocity of wave (small circle among Figure 11) that the array waveform information extracts, obtain variance curve, as shown in figure 12 with the variation of stratum shear wave velocity.
(5). by to the variance curve interpolation, determine the stratum shear wave velocity of correspondence when variance is zero, be the stratum shear wave velocity that this depth point inverting obtains, as shown in figure 12.This stratum shear wave velocity that obtains by the method for the invention is 507.32m/s, and actual stratum shear wave velocity is 508m/s.
Scheme two, the concrete steps of dipole leakage mode ripple inverting stratum shear wave velocity are:
(1). the Wave data of the leakage mode ripple of being measured by multipole array sonic log instrument dipole mode of operation of the depth point of soft formation well section that hole enlargement is serious and stratum velocity of longitudinal wave, hole diameter, the mud velocity of sound, the mud density parameter that this corresponding depth point is measured by conventional logging input to several memories of computer.
(2). utilize FFT electrode couple subarray waveform to do spectrum analysis, obtain the frequency spectrum of per pass waveform.On this basis, utilize frequency spectrum weighting correlation method to extract dipole leakage mode phase velocity of wave dispersion curve.
(3). set up wellhole dipole acoustic logging theory model, derive the theoretical dispersion equation of wellhole dipole mode wave according to the inside and outside wave equation of wellhole and fringe conditions.Stratum velocity of longitudinal wave, density, hole diameter, the mud velocity of sound and mud density are known by other logging methods measurements in the model, change the stratum shear wave velocity and find the solution dipole leakage mode phase velocity of wave dispersion curve with Newton iteration method by dispersion equation.
(4). in the main energy frequency range of dipole leakage mode ripple, i.e. 2 KHzs~5 KHzs, calculate the variance sum of the leakage mode phase velocity of wave of theoretical down leakage mode phase velocity of wave of calculating of Different Strata shear wave velocity and the extraction of on-the-spot dipole array waveform information, obtain the variance curve that changes with the stratum shear wave velocity.
(5). by to the variance curve interpolation, determine the stratum shear wave velocity of correspondence when variance is zero, be the stratum shear wave velocity that this depth point inverting obtains.
In sum, with the multipole array acoustic log data of the method for the invention processing shallow-layer well section, export continuous stratum shear wave velocity section, as shown in figure 13.The stratum velocity of longitudinal wave of this shallow-layer well section is about 2500 meter per seconds, and the stratum shear wave velocity belongs to typical soft formation about 1200.Shown in the 1st road bit size, hole diameter and gamma ray curve among the figure, this well uses 9.5 inches drill bits well-diggings serious hole enlargement phenomenon to occur 430~435 meters and 446~453 meters well sections, and hole diameter reaches 50 centimetres.The 2nd and 3 roads provide the one pole of multipole array sonic log data and the full-wave train waveform of dipole respectively among the figure, can find out from the full-wave train waveform, two well section one pole and the dipole serious in hole enlargement all excite the very strong leakage mode ripple of amplitude, are not used for one pole Stoneley wave and the DIPOLE FLEXURAL WAVES that soft formation is measured shear wave velocity and excite.Handle the dipole array waveform information with traditional slowness time matching method, the stratum shear wave velocity that obtains index of correlation plane and correspondence is shown in the 4th road among the figure.Find out from the index of correlation plan view, only the index of correlation 435~445 meters regular slim hole section DIPOLE FLEXURAL WAVES is bigger, can extract reliable stratum shear wave velocity by DIPOLE FLEXURAL WAVES, and very poor even do not have in the correlation of the serious well section DIPOLE FLEXURAL WAVES of other two hole enlargements, can't extract the stratum shear wave velocity this moment by the dipole data.The 5th road provides shear wave velocity, the contrast of stratum velocity of longitudinal wave that the stratum shear wave velocity that utilizes the inventive method to utilize the inverting of one pole leakage mode ripple Dispersion and regular well section dipole extract among the figure.Comparing result shows that the inventive method can obtain continuous stratum shear wave velocity section by the inverting of leakage mode ripple at the loose shallow-layer of hole condition complexity.In the soft formation well section of 435~445 meters hole diameter rules, the DIPOLE FLEXURAL WAVES waveform is better, identical fine of the shear wave velocity result (small circle) that the inversion result of the method for the invention (heavy line) and dipole extract; 430~435 meters and 446~453 meters serious well sections of hole enlargement, do not excited DIPOLE FLEXURAL WAVES, can't extract the stratum shear wave velocity from the dipole data, the method of the invention is stable, reliable by the stratum shear wave velocity that the one pole leakage mode ripple of frequency dispersion is finally inversed by, consistent with stratum velocity of longitudinal wave trend and the engineering that can be used for oil exploration and exploitation is used than rationally the ripple time difference in length and breadth.
1, frequency spectrum weighting correlation method list of references: Tang Xiaoming, Zheng Chuanhan work,, the acoustics of quantitatively logging well, petroleum industry publishing house, p52-54 in 2004.
2, Prony method list of references: Lang, S.W.Kurkjian, J.H. etc., 1987, Estimatingslowness dispersion from arrays of sonic logging waveforms, Geophysics, Vol.52, p530-544.
3, Matrix Pencil method list of references: Ekstrom, M.P., 1995, Dispersion estimationfrom borehole acoustic arrays using a modified matrix pencil algorithm, 29thAsilomar Conference on Signals Systems and Computers, p449-453.
4, homomorphism processing method list of references: Ellefsen, K.J.Cheng, C.H.Tubman, K.M., 1989, Estimating phase velocity and attenuation of guided waves inacoustic logging data, Geophysics, VOL, 54, p1054-1059.
5, wellhole sound field Modeling Theory list of references: Kurkjian, J.H.and Chang, S.K., 1986, Acoustic multipole sources in fuid-filled boreholes, Geophysics.51 (1) 148-163.