CN106093100B - A kind of rock core nuclear magnetic signal collection of ME CPMG sequences and inversion method - Google Patents
A kind of rock core nuclear magnetic signal collection of ME CPMG sequences and inversion method Download PDFInfo
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- CN106093100B CN106093100B CN201610431170.4A CN201610431170A CN106093100B CN 106093100 B CN106093100 B CN 106093100B CN 201610431170 A CN201610431170 A CN 201610431170A CN 106093100 B CN106093100 B CN 106093100B
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Abstract
The invention discloses a kind of collection of the rock core nuclear magnetic signal of ME CPMG sequences and inversion method.This method is under the conditions of stationary magnetic field, by setting the stand-by period by the proton perfact polarization of sample to Z axis, reapply 90 ° of radio-frequency pulses to pull macroscopic magnetization vector to X/Y plane down, and then apply a series of 180 ° of radio-frequency pulses, and magnetization vector is gathered between two neighboring 180 ° of radio-frequency pulses.From unlike CPMG pulses, the time intervals of two adjacent 180 ° of radio-frequency pulses can be changed according to the prior information of sample and user's request, typically be increased with the increase in sampling time.ME CPMG pulse sequences reduce 180 ° of radio-frequency pulse numbers, have effectively saved energy and data space needed for signal excitation, have improved inverting speed.This method has larger application prospect in shale, tight sand, carbonate rock etc. have weak relaxation signals, the rock core of complex pore structure.
Description
Technical field
The present invention relates to a kind of rock core nuclear magnetic signal collection based on the ME-CPMG sequences for becoming echo sounding nonuniform sampling
And inversion method, belong to nuclear magnetic resonance and rock physicses field.
Background technology
With further going deep into for energy exploration, the complicated and unconventional reservoir such as carbonate rock, fine and close oil gas, shale oil gas
Into the emphasis of research.These reservoir properties are poor, and anisotropism is strong, complex pore structure, to traditional nuclear magnetic resonance technique band
Carry out huge challenge.Complicated and unconventional reservoir relaxation signals are weak, complex pore structure, and traditional nuclear magnetic resonance technique is based on CPMG
Pulse train, the required radio-frequency pulse number increase when echo sounding shortens, thus, required for encouraging these radio-frequency pulses
Energy will also be sharply increased.In addition, CPMG pulse sequence gathers echo amplitude by the way of uniform sampling, information is easily produced
Redundancy, significantly impacts signal acquisition rate and inversion accuracy.
The content of the invention
For problem above, the present invention proposes the collection of rock core nuclear magnetic signal and the inversion method of a kind of ME-CPMG sequences.
The adopted technical solution is that：
A kind of rock core nuclear magnetic signal collection of ME-CPMG sequences and inversion method, comprise the following steps：
S1, rock core is put into the magnet of stationary magnetic field intensity, pulse train is divided into N number of window；
S2, the N number of window of setting echo sounding TE1,TE2,…,TENWith 180 ° of radio-frequency pulse number P of correspondenceE1,PE2,…,
PEN；
S3, setting stand-by period Tw, make magnetization vector perfact polarization to Z axis；
S4,90 ° of radio-frequency pulses of application pull magnetization vector to X/Y plane；
S5, by TE1/ 2 after-applied first 180 ° of radio-frequency pulse, magnetization vector are turned to the another side of X/Y plane；
S6, again pass through TE1After-applied second 180 ° of radio-frequency pulse, it is hereafter continuous to apply PE1- 2 180 ° of radio-frequency pulses,
And echo amplitude is gathered between two adjacent 180 ° of radio-frequency pulses, complete the echo wave signal acquisition of first window；
S7,180 ° of rf pulse sequences for applying second window, the time interval of adjacent radio frequency pulse is TE2, apply arteries and veins
Number is rushed for PE2, echo amplitude is gathered between two adjacent 180 ° of radio-frequency pulses；
S8, successively the 3rd window of application gather echo amplitude to 180 ° of rf pulse sequences of n-th window；
S9, using SIRT algorithms by echo amplitude inverting into nuclear magnetic resoance spectrum.
It is preferred that, the stand-by period TwFor 6 seconds.
The method have the benefit that：
1st, the rock core nuclear magnetic signal collection for the ME-CPMG sequences that the present invention is provided and inversion method, referred to as pulse train
Divide window method, effective collection of nuclear magnetic signal when relaxation component is more in rock core can be achieved；Different windows has respective time
Wave spacing and radio-frequency pulse number, can to difference from relaxation component carry out meticulous depiction.
2nd, the change echo sounding nonuniform sampling mode that the present invention is provided, can farthest reduce information redundancy, effectively
Saving memory space, while be greatly enhanced inverting speed, available for nuclear magnetic resonance experiment and pore structure evaluation, especially fit
Close the complex samples such as carbonate rock, shale and tight sand.
3rd, radio-frequency pulse is optimized combination by the inventive method, is dropped by changing the time interval of adjacent radio frequency pulse
Radio-frequency pulse number needed for low signal collection.Meanwhile, using the method for pulse train point window, between the echo for setting different windows
Every with radio-frequency pulse number, be effectively reduced the energy excited needed for radio-frequency pulse, farthest reduce information redundancy, it is convenient
Nuclear magnetic resonance is tested and inverting.
Brief description of the drawings
Fig. 1 is a kind of rock core nuclear-magnetism based on the ME-CPMG sequences for becoming echo sounding nonuniform sampling that the present invention is provided
The flow chart of signal acquisition and inversion method；
Fig. 2 is the ME-CPMG sequence diagrams for the change echo sounding nonuniform sampling that the present invention is provided；
Fig. 3 is that certain has the echo amplitude signal and inversion result of unimodal relaxation signals；
Fig. 4 is that certain has the echo amplitude signal and inversion result of bimodal relaxation signals；
Fig. 5 is certain echo amplitude signal and inversion result with three peak relaxation signals.
Embodiment
The present invention proposes a kind of rock core nuclear magnetic signal collection based on the ME-CPMG sequences for becoming echo sounding nonuniform sampling
And inversion method.Under the conditions of stationary magnetic field, the proton perfact polarization of sample, to Z axis, is reapplied by setting the stand-by period
90 ° of radio-frequency pulses pull macroscopic magnetization vector to X/Y plane down, and then apply a series of 180 ° of radio-frequency pulses, and adjacent two
Magnetization vector is gathered between individual 180 ° of radio-frequency pulses.From unlike CPMG pulses, between the time of two adjacent 180 ° of radio-frequency pulses
Every that can be changed according to the prior information of sample and user's request, typically increase with the increase in sampling time.ME-
CPMG pulse sequence reduces 180 ° of radio-frequency pulse numbers, has effectively saved energy and data storage sky needed for signal excitation
Between, inverting speed is improved, in the rock core with weak relaxation signals, complex pore structure such as shale, tight sand, carbonate rock
In have larger application prospect.
The present invention will be described with embodiment below in conjunction with the accompanying drawings.
As shown in figure 1, a kind of rock core nuclear magnetic signal collection based on the ME-CPMG sequences for becoming echo sounding nonuniform sampling
And inversion method, mainly include window segmentation, the design of echo sounding and rf pulse sequence number, the pulse train of different windows
Realize and echo amplitude collection, the inverting of echo amplitude and nuclear magnetic resoance spectrum generation, four parts are indispensable, and order can not run
.This method is specifically carried out successively according to the following steps：
S1, rock core is put into the magnet of stationary magnetic field intensity, pulse train is divided into N number of window；
S2, the N number of window of setting echo sounding (TE1,TE2,…,TEN) and 180 ° of radio-frequency pulse number (P of correspondenceE1,
PE2,…,PEN)；
S3, setting stand-by period Tw(generally 6 seconds), make magnetization vector perfact polarization to Z axis；
S4,90 ° of radio-frequency pulses of application pull magnetization vector to X/Y plane；
S5, by TE1/ 2 after-applied first 180 ° of radio-frequency pulse, magnetization vector are turned to the another side of X/Y plane；
S6, again pass through TE1After-applied second 180 ° of radio-frequency pulse, it is hereafter continuous to apply PE1- 2 180 ° of radio-frequency pulses,
And echo amplitude is gathered between two adjacent 180 ° of radio-frequency pulses, complete the echo wave signal acquisition of first window；
S7,180 ° of rf pulse sequences for applying second window, the time interval of adjacent radio frequency pulse is TE2, apply arteries and veins
Number is rushed for PE2, echo amplitude is gathered between two adjacent 180 ° of radio-frequency pulses；
S8, apply the 3rd window successively to 180 ° of rf pulse sequences of n-th window, the time of adjacent radio frequency pulse
Interval is followed successively by TE3,TE4,…,TEN, the corresponding pulse number that applies is PE3,PE4,…,PEN, gather echo amplitude；
S9, using SIRT algorithms by echo amplitude inverting into nuclear magnetic resoance spectrum.
Fig. 2 is the schematic diagram for becoming echo sounding nonuniform sampling ME-CPMG sequences.Penetrated using 90 ° of radio-frequency pulses and 180 °
The mode of frequency pulse optimization combination carries out a point window to pulse train, sets the echo sounding and pulse number of different windows so that
The generation and collection of signal are more targeted, can be effectively reduced radio-frequency pulse number and data space.
Fig. 3 is that certain has the echo amplitude signal and inversion result of unimodal relaxation signals.Fig. 3 (a) is the echo width of generation
Signal is spent, when signal is produced, the stand-by period is 6s.Pulse train is divided into 6 windows, the echo sounding difference of each window
For 0.05ms, 0.1ms, 0.2ms, 0.4ms, 0.6ms, 0.8ms, corresponding pulse number is respectively 1000,500,250,125,
64、32.Fig. 3 (b) is the nuclear magnetic resoance spectrum obtained according to echo amplitude inverting, inverting application SIRT algorithms.
Fig. 4 is that certain has the echo amplitude signal and inversion result of bimodal relaxation signals.Fig. 4 (a) is the echo width of generation
Signal is spent, when signal is produced, the stand-by period is 6s.Pulse train is divided into 6 windows, the echo sounding difference of each window
For 0.05ms, 0.1ms, 0.2ms, 0.4ms, 0.6ms, 0.8ms, corresponding pulse number is respectively 1000,500,250,125,
64、32.Fig. 4 (b) is the nuclear magnetic resoance spectrum obtained according to echo amplitude inverting, inverting application SIRT algorithms.
Fig. 5 is certain echo amplitude signal and inversion result with three peak relaxation signals.Fig. 5 (a) is the echo width of generation
Signal is spent, when signal is produced, the stand-by period is 6s.Pulse train is divided into 6 windows, the echo sounding difference of each window
For 0.05ms, 0.1ms, 0.2ms, 0.4ms, 0.6ms, 0.8ms, corresponding pulse number is respectively 1000,500,250,125,
64、32.Fig. 5 (b) is the nuclear magnetic resoance spectrum obtained according to echo amplitude inverting, inverting application SIRT algorithms.
Take or use for reference prior art and can be achieved in the part do not addressed in aforesaid way.
It should be noted that under the teaching of this specification, any equivalent substitute side made by those skilled in the art
Formula, or obvious variant, all should be within protection scope of the present invention.
Claims (2)
1. a kind of rock core nuclear magnetic signal collection of ME-CPMG sequences and inversion method, it is characterised in that comprise the following steps：
S1, rock core is put into the magnet of stationary magnetic field intensity, pulse train is divided into N number of window；
S2, the N number of window of setting echo sounding TE1,TE2,…,TENWith 180 ° of radio-frequency pulse number P of correspondenceE1,PE2,…,PEN；
S3, setting stand-by period Tw, make magnetization vector perfact polarization to Z axis；
S4,90 ° of radio-frequency pulses of application pull magnetization vector to X/Y plane；
S5, by TE1/ 2 after-applied first 180 ° of radio-frequency pulse, magnetization vector are turned to the another side of X/Y plane；
S6, again pass through TE1After-applied second 180 ° of radio-frequency pulse, it is hereafter continuous to apply PE1- 2 180 ° of radio-frequency pulses, and two
Echo amplitude is gathered between individual adjacent 180 ° of radio-frequency pulses, the echo wave signal acquisition of first window is completed；
S7,180 ° of rf pulse sequences for applying second window, the time interval of adjacent radio frequency pulse is TE2, apply pulse
Number is PE2, echo amplitude is gathered between two adjacent 180 ° of radio-frequency pulses；
S8, successively the 3rd window of application gather echo amplitude to 180 ° of rf pulse sequences of n-th window；
S9, using SIRT algorithms by echo amplitude inverting into nuclear magnetic resoance spectrum.
2. a kind of rock core nuclear magnetic signal collection of ME-CPMG sequences according to claim 1 and inversion method, its feature exist
In：The stand-by period TwFor 6 seconds.
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| CN107966465B (en) * | 2017-11-23 | 2019-12-03 | 中国石油大学(华东) | A kind of acquisition of rock core nuclear magnetic signal and inversion method based on three-dimensional pulse train |
| CN111044960B (en) * | 2019-12-31 | 2021-02-12 | 苏州大学 | Solid nuclear magnetic resonance quantitative detection method and device based on successive cross polarization |
| CN112798635B (en) * | 2020-12-31 | 2024-02-20 | 东南大学 | Nuclear magnetic resonance signal pulse method for compensating non-uniformity of radio frequency magnetic field |
| CN112835111A (en) * | 2021-01-04 | 2021-05-25 | 中国石油天然气集团有限公司 | Composite radio frequency pulse method for nuclear magnetic resonance logging |
| CN114324441A (en) * | 2021-12-31 | 2022-04-12 | 苏州纽迈分析仪器股份有限公司 | Two-dimensional inversion map generation method, equipment and storage medium |
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| US6331775B1 (en) * | 1999-09-15 | 2001-12-18 | Baker Hughes Incorporated | Gas zone evaluation by combining dual wait time NMR data with density data |
| US6714009B2 (en) * | 2002-05-16 | 2004-03-30 | Schlumberger Technology Corporation | Method for the inversion of CPMG measurements enhanced by often repeated short wait time measurements |
| DE102004017852B4 (en) * | 2004-04-13 | 2008-11-27 | Siemens Ag | Motion-corrected multi-shot method for diffusion-weighted imaging in magnetic resonance imaging |
| DE102012204434B3 (en) * | 2012-03-20 | 2013-07-11 | Siemens Aktiengesellschaft | Method for operating magnetic resonance imaging system for producing magnetic resonance image data of investigation object e.g. patient, involves selecting width of radio frequency (RF) refocusing pulses for generating echo signals |
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| CN104297278B (en) * | 2014-09-28 | 2016-06-01 | 中国石油大学(华东) | Improvement type CPMG sequence T2-G acquisition parameter t0Self-adaptation method |
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