阅读说明：本技术 一种扩散t2弛豫二维谱的校正方法和装置 (Correction method and device for diffusion T2 relaxation two-dimensional spectrum ) 是由 薛志波 姜志敏 党煜蒲 张嘉伟 张国强 李�东 刘世明 张璋 于 2019-09-10 设计创作，主要内容包括：本发明实施例公开了一种扩散T2弛豫二维谱的校正方法和装置,包括：根据第一梯度场对多维核磁共振回波数据进行反演得到原始的扩散T2弛豫二维谱；根据原始的扩散T2弛豫二维谱中受内部梯度场影响明显的区域的扩散系数计算内建梯度场；根据第一梯度场和内建梯度场之和对多维核磁共振回波数据进行反演得到校正后的扩散T2弛豫二维谱。本发明实施例基于原始的扩散T2弛豫二维谱中受内部梯度场影响明显的区域的扩散系数消除了内部梯度场的影响,保证了同一流体处于不同弛豫时间T2的谱峰具有相同的扩散系数,提高了精度；能够适用更多的应用场景。(The embodiment of the invention discloses a method and a device for correcting a diffusion T2 relaxation two-dimensional spectrum, which comprises the following steps: inverting the multi-dimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum; calculating a built-in gradient field according to a diffusion coefficient of a region obviously influenced by the internal gradient field in an original diffusion T2 relaxation two-dimensional spectrum; and inverting the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum. The embodiment of the invention eliminates the influence of the internal gradient field based on the diffusion coefficient of the region obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum, ensures that the spectrum peaks of the same fluid at different relaxation times T2 have the same diffusion coefficient, and improves the precision; more application scenarios can be applied.)

1. A correction method of diffusion T2 relaxation two-dimensional spectrum comprises the following steps:

inverting the multi-dimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum;

calculating a built-in gradient field according to a diffusion coefficient of a region obviously influenced by the internal gradient field in an original diffusion T2 relaxation two-dimensional spectrum;

and inverting the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum.

2. The method according to claim 1, wherein the calculating the built-in gradient field from diffusion coefficients of regions of the original diffusion T2 relaxation two-dimensional spectrum that are apparent from the internal gradient field comprises:

calculating the average value of diffusion coefficients of regions which are obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum; calculating an internal gradient field average value according to the diffusion coefficient average value; and calculating the built-in gradient field according to the internal gradient field average value.

3. The method of claim 2, wherein (G) is expressed in terms of formula (a)_int+G_app)×D₀＝G_app2Calculating the average value of the internal gradient field by x D; wherein D is₀For measuring the free diffusion coefficient of water at temperature, D is the mean value of said diffusion coefficients, G_app2Is said first gradient field, G_intIs the mean value of the internal gradient field, G_appThe external magnetic field strength applied when the logging instrument measures.

4. The method of claim 2, wherein G is expressed according to formula_int(t2r)×t2r＝G_int(t2)X t2 calculating the built-in gradient field;

wherein G is_int(t2r)Is the internal gradient field mean, t2r is the internal gradient field meanMean value, G, of T2 spectrum corresponding to regions where gradient field effects are significant_int(t2)For the built-in gradient field, t2 is the relaxation time.

5. A correction device for diffusion T2 relaxation two-dimensional spectrum, comprising:

the first inversion module is used for inverting the multi-dimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum;

the calculation module is used for calculating a built-in gradient field according to the diffusion coefficient of a region obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum;

and the second inversion module is used for inverting the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum.

6. An apparatus for correcting a diffusion T2 relaxation two-dimensional spectrum, comprising a processor and a computer readable storage medium having stored therein instructions, wherein the instructions, when executed by the processor, implement the method for correcting a diffusion T2 relaxation two-dimensional spectrum according to any one of claims 1 to 4.

7. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method for correcting a diffusion T2 relaxation two-dimensional spectrum according to any one of claims 1 to 4.

Technical Field

The embodiments of the present invention relate to, but not limited to, nuclear magnetic resonance logging technologies, and in particular, to a method and an apparatus for correcting a diffusion T2 relaxation two-dimensional spectrum.

Background

¹The nuclear magnetic resonance of H nucleus can directly obtain hydrogen-containing substances¹H nuclear signal, water and crude oil all contain¹The H nucleus can directly obtain the information of the content, the property and the like of water and crude oil by nuclear magnetic logging, is a powerful tool for logging, and provides direct and rich information for petroleum exploration and development. At present, the main method of nuclear magnetic logging is to utilize a CPMG sequence or a DE-CPMG sequence to obtain the characteristics of crude oil and water content, T2 relaxation time, diffusion coefficient and the like. The CPMG sequence can measure T2 relaxation time and 1H nuclear total amount, but the oil-water saturation cannot be determined through T2 relaxation time due to the large influence of rock surface properties on T2 relaxation time and complex mechanism. The CPMG sequence is combined with a plurality of DE-CPMG sequences with different long echo intervals, T2 relaxation time and diffusion coefficients can be measured simultaneously to form a diffusion T2 relaxation two-dimensional spectrum, and the diffusion coefficients are influenced by the properties of the rock core by a very clear mechanism and can be used as main marks for distinguishing oil and water. Multi-dimensional nuclear magnetic logging has become a developing direction for nuclear magnetic logging.

The main way to distinguish different fluids by multidimensional spectroscopy is to see the magnitude of the diffusion coefficient, which is mainly influenced by the fact that limited diffusion leads to a decrease in the diffusion coefficient and by the fact that magnetic field inhomogeneities lead to an increase in the diffusion coefficient. The increase of the diffusion coefficient caused by the magnetic field nonuniformity is a main influence factor of inaccurate measurement results of the diffusion coefficient, and the magnetic field nonuniformity in logging is caused by an internal gradient field caused by the inconsistency of the magnetic susceptibility in the core. The key to the success of multidimensional spectral measurement is to correct the influence of the internal gradient field on the downhole data.

Disclosure of Invention

The embodiment of the invention provides a method and a device for correcting a diffusion T2 relaxation two-dimensional spectrum, which can be applied to various application scenes and improve the precision.

The embodiment of the invention provides a method for correcting a diffusion T2 relaxation two-dimensional spectrum, which comprises the following steps:

inverting the multi-dimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum;

calculating a built-in gradient field according to a diffusion coefficient of a region obviously influenced by the internal gradient field in an original diffusion T2 relaxation two-dimensional spectrum;

and inverting the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum.

In an embodiment of the present invention, the calculating the built-in gradient field according to the diffusion coefficient of the region in the original diffusion T2 relaxation two-dimensional spectrum, where the region is significantly affected by the internal gradient field, includes:

calculating the average value of diffusion coefficients of regions which are obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum; calculating an internal gradient field average value according to the diffusion coefficient average value; and calculating the built-in gradient field according to the internal gradient field average value.

In the embodiment of the invention, according to the formula (G)_int+G_app)×D₀＝G_app2Calculating the average value of the internal gradient field by x D; wherein D is₀For measuring the free diffusion coefficient of water at temperature, D is the mean value of said diffusion coefficients, G_app2Is said first gradient field, G_intIs the mean value of the internal gradient field, G_appThe external magnetic field strength applied when the logging instrument measures.

In the embodiment of the invention, the formula G is followed_int(t2r)×t2r＝G_int(t2)X t2 calculating the built-in gradient field;

wherein G is_int(t2r)T2r is the average of the T2 spectrum corresponding to the region significantly affected by the internal gradient field, G_int(t2)For the built-in gradient field, t2 is the relaxation time.

The embodiment of the invention provides a device for correcting a diffusion T2 relaxation two-dimensional spectrum, which comprises:

the first inversion module is used for inverting the multi-dimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum;

the calculation module is used for calculating a built-in gradient field according to the diffusion coefficient of a region obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum;

and the second inversion module is used for inverting the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum.

The embodiment of the invention provides a device for correcting a diffusion T2 relaxation two-dimensional spectrum, which comprises a processor and a computer readable storage medium, wherein the computer readable storage medium stores instructions, and when the instructions are executed by the processor, the instructions realize any one of the above methods for correcting the diffusion T2 relaxation two-dimensional spectrum.

Embodiments of the present invention provide a computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, implements the steps of any one of the above-mentioned methods for correcting a diffusion T2 relaxation two-dimensional spectrum.

The embodiment of the invention comprises the following steps: inverting the multi-dimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum; calculating a built-in gradient field according to a diffusion coefficient of a region obviously influenced by the internal gradient field in an original diffusion T2 relaxation two-dimensional spectrum; and inverting the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum. The embodiment of the invention eliminates the influence of the internal gradient field based on the diffusion coefficient of the region obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum, ensures that the spectrum peaks of the same fluid at different relaxation times T2 have the same diffusion coefficient, and improves the precision; moreover, only the tested area is required to contain water, and the tested area is not required to contain only water; moreover, the internal gradient field is not required to be in direct proportion to the nuclear magnetic resonance measurement frequency of the instrument; in addition, an additional measurement sequence is not required to be added, and the measurement speed and the resolution ratio are not influenced; that is, more application scenarios can be applied.

Additional features and advantages of embodiments of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the invention. The objectives and other advantages of the embodiments of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the examples of the invention serve to explain the principles of the embodiments of the invention and not to limit the embodiments of the invention.

Fig. 1 is a flowchart of a method for correcting a diffusion T2 relaxation two-dimensional spectrum according to an embodiment of the present invention;

FIG. 2 is a graph showing the original diffusion T2 relaxation two-dimensional spectrum of a measured region (containing only water) according to an embodiment of the present invention;

FIG. 3 is a graph illustrating a built-in gradient field and relaxation time T2 according to an embodiment of the present invention;

FIG. 4 is a two-dimensional relaxation spectrum of diffusion T2 after correction according to an embodiment of the present invention;

fig. 5 is a schematic structural composition diagram of a correction apparatus for diffusion T2 relaxation two-dimensional spectrum according to another embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments of the present invention may be arbitrarily combined with each other without conflict.

The steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions. Also, while a logical order is shown in the flow diagrams, in some cases, the steps shown or described may be performed in an order different than here.

Referring to fig. 1, an embodiment of the present invention provides a method for correcting a diffusion T2 relaxation two-dimensional spectrum, including:

and step 100, inverting the multi-dimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum.

In the embodiment of the invention, the multi-dimensional nuclear magnetic resonance echo data is echo data acquired by adopting nuclear magnetic resonance logging on a measured area. The region to be measured may contain only water or water and other fluids.

Step 101, calculating a built-in gradient field according to diffusion coefficients of regions obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum.

In one illustrative example, calculating the built-in gradient field from the diffusion coefficients of regions of the original diffusion T2 relaxation two-dimensional spectrum that are evident from the internal gradient field comprises:

calculating the average value of diffusion coefficients of regions obviously influenced by internal gradient fields in the original diffusion T2 relaxation two-dimensional spectrum; calculating the average value of the internal gradient field according to the average value of the diffusion coefficient; the built-in gradient field is calculated from the internal gradient field mean.

Wherein, the region obviously affected by the internal gradient field can be determined by the observation of the original diffusion T2 relaxation two-dimensional spectrum by the user, and then manually selected.

FIG. 2 is a graph showing the original diffusion T2 relaxation two-dimensional spectrum of a measured region (containing only water) according to an embodiment of the present invention. As shown in fig. 2, the abscissa is the relaxation time T2, and the ordinate is the diffusion coefficient. The spectral peak diffusion coefficient for small apertures (shorter relaxation time T2) is significantly larger due to the presence of the internal gradient field, as shown by the dashed box in fig. 2. After selecting the region which is obviously influenced by the internal gradient field, calculating the average value of all diffusion coefficients in the selected region, namely the diffusion coefficient average value.

In one illustrative example, according to the formula (G)_int+G_app)×D₀＝G_app2Calculating the average value of the internal gradient field by multiplying by D; wherein D is₀To measure the free diffusion coefficient of water at temperature (e.g. logging temperature), D is the mean value of the diffusion coefficients, G_app2Is a first gradient field, G_intAs internal gradient field mean, G_appThe external magnetic field strength applied when the logging instrument measures.

Since the relaxation time T2 is proportional to the aperture size, T2 can be used to replace the aperture size to calculate the built-in gradient field, i.e. G, corresponding to different T2_int(t2r)×t2r＝G_int(t2)×t2；

Wherein G is_int(t2r)The mean value of the internal gradient field, T2r is the mean value of the T2 spectrum corresponding to the region significantly affected by the internal gradient field, G_int(t2)For the built-in gradient field, t2 is the relaxation time.

FIG. 3 is a graph illustrating the built-in gradient field and relaxation time T2 according to an embodiment of the present invention. As shown in fig. 3, the abscissa is the relaxation time T2 and the ordinate is the magnitude of the built-in gradient field.

And 102, inverting the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum.

FIG. 4 is a two-dimensional relaxation spectrum of diffusion T2 after correction according to an embodiment of the present invention. As shown in fig. 4, the abscissa is the relaxation time T2, and the ordinate is the diffusion coefficient. Comparing fig. 2 and fig. 4, it can be seen that the influence of the internal gradient field on the diffusion coefficient is eliminated.

The embodiment of the invention eliminates the influence of the internal gradient field based on the diffusion coefficient of the region obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum, ensures that the spectrum peaks of the same fluid at different relaxation times T2 have the same diffusion coefficient, and improves the precision; moreover, only the tested area is required to contain water, and the tested area is not required to contain only water; moreover, it is not necessary that the internal gradient field be proportional to the instrument frequency; in addition, an additional measurement sequence is not required to be added, and the measurement speed and the resolution ratio are not influenced; that is, more application scenarios can be applied.

Another embodiment of the present invention provides an apparatus for calibrating multi-dimensional nuclear magnetic resonance echo data, including a processor and a computer-readable storage medium, where instructions are stored in the computer-readable storage medium, and when the instructions are executed by the processor, the apparatus implements any one of the above-mentioned methods for calibrating multi-dimensional nuclear magnetic resonance echo data.

Another embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, performs the steps of any one of the above-mentioned methods for correcting multi-dimensional nuclear magnetic resonance echo data.

Referring to fig. 5, another embodiment of the present invention provides a device for correcting a diffusion T2 relaxation two-dimensional spectrum, including:

the first inversion module 501 is configured to invert the multidimensional nuclear magnetic resonance echo data according to the first gradient field to obtain an original diffusion T2 relaxation two-dimensional spectrum;

a calculating module 502, configured to calculate a built-in gradient field according to a diffusion coefficient of a region, which is obviously affected by the internal gradient field, in the original diffusion T2 relaxation two-dimensional spectrum;

the second inversion module 503 is configured to invert the multi-dimensional nuclear magnetic resonance echo data according to the sum of the first gradient field and the built-in gradient field to obtain a corrected diffusion T2 relaxation two-dimensional spectrum.

In the embodiment of the invention, the multi-dimensional nuclear magnetic resonance echo data is echo data acquired by adopting nuclear magnetic resonance logging on a measured area. The region to be measured may contain only water or water and other fluids.

In an exemplary embodiment, the calculation module 502 is specifically configured to:

calculating the average value of diffusion coefficients of regions obviously influenced by internal gradient fields in the original diffusion T2 relaxation two-dimensional spectrum; calculating the average value of the internal gradient field according to the average value of the diffusion coefficient; the built-in gradient field is calculated from the internal gradient field mean.

Wherein, the region obviously affected by the internal gradient field can be determined by the observation of the original diffusion T2 relaxation two-dimensional spectrum by the user, and then manually selected.

FIG. 2 is a graph showing the original diffusion T2 relaxation two-dimensional spectrum of a measured region (containing only water) according to an embodiment of the present invention. As shown in fig. 2, the abscissa is the relaxation time T2, and the ordinate is the diffusion coefficient. The spectral peak diffusion coefficient for small apertures (shorter relaxation time T2) is significantly larger due to the presence of the internal gradient field, as shown by the dashed box in fig. 2. After selecting the region which is obviously influenced by the internal gradient field, calculating the average value of all diffusion coefficients in the selected region, namely the diffusion coefficient average value.

In one illustrative example, the calculation module 502 follows the formula (G)_int+G_app)×D₀＝G_app2Calculating the average value of the internal gradient field by multiplying by D; wherein D is₀Free diffusion systems for measuring temperature (e.g. logging temperature) of waterNumber, D is the average value of the diffusion coefficient, G_app2Is a first gradient field, G_intAs internal gradient field mean, G_appThe external magnetic field strength applied when the logging instrument measures.

Since the relaxation time T2 is proportional to the aperture size, T2 can be used to replace the aperture size to calculate the built-in gradient field, i.e. G, corresponding to different T2_int(t2r)×t2r＝G_int(t2)×t2；

Wherein G is_int(t2r)The mean value of the internal gradient field, T2r is the mean value of the T2 spectrum corresponding to the region significantly affected by the internal gradient field, G_int(t2)For the built-in gradient field, t2 is the relaxation time.

FIG. 3 is a graph illustrating the built-in gradient field and relaxation time T2 according to an embodiment of the present invention. As shown in fig. 3, the abscissa is the relaxation time T2 and the ordinate is the magnitude of the built-in gradient field.

FIG. 4 is a two-dimensional relaxation spectrum of diffusion T2 after correction according to an embodiment of the present invention. As shown in fig. 4, the abscissa is the relaxation time T2, and the ordinate is the diffusion coefficient. Comparing fig. 2 and fig. 4, it can be seen that the influence of the internal gradient field on the diffusion coefficient is eliminated.

The embodiment of the invention eliminates the influence of the internal gradient field based on the diffusion coefficient of the region obviously influenced by the internal gradient field in the original diffusion T2 relaxation two-dimensional spectrum, ensures that the spectrum peaks of the same fluid at different relaxation times T2 have the same diffusion coefficient, and improves the precision; moreover, only the tested area is required to contain water, and the tested area is not required to contain only water; moreover, it is not necessary that the internal gradient field be proportional to the instrument frequency; in addition, an additional measurement sequence is not required to be added, and the measurement speed and the resolution ratio are not influenced; that is, more application scenarios can be applied.

The specific implementation process of the correction device for multi-dimensional nuclear magnetic resonance echo data is the same as the specific implementation process of the correction method for multi-dimensional nuclear magnetic resonance echo data of the foregoing embodiment.

It will be understood by those of ordinary skill in the art that all or some of the steps of the methods, systems, functional modules/units in the devices disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed by several physical components in cooperation. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as is well known to those of ordinary skill in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by a computer. In addition, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media as known to those skilled in the art.

Although the embodiments of the present invention have been described above, the descriptions are only used for understanding the embodiments of the present invention, and are not intended to limit the embodiments of the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the embodiments of the invention as defined by the appended claims.