CN110261922B - Method and device for acquiring capillary pressure curve based on nuclear magnetic resonance echo data - Google Patents
Method and device for acquiring capillary pressure curve based on nuclear magnetic resonance echo data Download PDFInfo
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Abstract
The application provides a method and a device for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data, wherein the method comprises the following steps: acquiring nuclear magnetic resonance echo data of each core sample in a plurality of core samples of a target reservoir and the mercury injection saturation of each core sample in the plurality of core samples under each preset mercury injection pressure in a plurality of preset mercury injection pressures; determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample; determining a model coefficient of a target model under each preset mercury injection pressure according to at least one echo parameter of each core sample and the mercury injection saturation of each core sample under each preset mercury injection pressure; and determining a capillary pressure curve of the target reservoir according to the target model and the model coefficients of the target model under each preset mercury injection pressure. According to the method for acquiring the capillary pressure curve based on the nuclear magnetic resonance echo data, the echo data does not need to be inverted, the calculation amount can be effectively reduced, and the calculation precision can be improved.
Description
Technical Field
The application relates to the technical field of oil and gas exploration and development, in particular to a method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data.
Background
The capillary pressure curve and the form thereof can represent the pore throat size and distribution of reservoir rock, and are one of important means for evaluating the pore structure of the reservoir rock. At present, capillary pressure curves used for researching a rock pore structure are generally obtained through a rock core mercury intrusion experiment, however, in actual production, due to the fact that the coring quantity is small, the coring cost is high, the application range is limited to a certain extent, and how to continuously obtain the capillary pressure curves of reservoir rocks is always a main subject of research of oil and gas exploration and development workers.
At present, generally, inversion is performed on nuclear magnetic resonance echo data acquired by nuclear magnetic resonance logging to obtain nuclear magnetic resonance transverse relaxation time T2 distribution, and then certain transformation is performed on the nuclear magnetic resonance transverse relaxation time T2 distribution to obtain a corresponding capillary pressure curve. However, for a compact sandstone reservoir which is more complex than a conventional reservoir, when nuclear magnetic resonance logging is performed, a large error exists in inversion of nuclear magnetic resonance echo data under a low signal-to-noise ratio, so that large uncertainty exists in the inverted nuclear magnetic resonance transverse relaxation time T2 distribution, and a large error exists in a converted capillary pressure curve.
In view of the above problems, no effective solution has been proposed.
Disclosure of Invention
The embodiment of the application provides a method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data, which aims to solve the problem that the capillary pressure curve obtained in the prior art has large errors.
The embodiment of the application provides a method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data, which comprises the following steps: acquiring nuclear magnetic resonance echo data of each core sample in a plurality of core samples of a target reservoir and the mercury injection saturation of each core sample in the plurality of core samples under each preset mercury injection pressure in a plurality of preset mercury injection pressures; determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample; determining a model coefficient of a target model under each preset mercury injection pressure according to at least one echo parameter of each core sample and the mercury injection saturation of each core sample under each preset mercury injection pressure; and determining a capillary pressure curve of the target reservoir according to the target model and the model coefficients of the target model under each preset mercury injection pressure.
In one embodiment, the at least one echo parameter comprises at least one of: the method comprises the following steps of (1) total porosity, echo data surrounding area, echo data attenuation time and an optimal echo amplitude value; determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample, wherein the echo parameter comprises at least one of the following parameters: determining the total porosity of each core sample according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample; determining the echo data surrounding area of each rock core sample according to the amplitude values of all echoes in the nuclear magnetic resonance echo data of each rock core sample; determining the attenuation time of the echo data of each rock core sample according to the average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each rock core sample; and determining the optimal echo amplitude value of each core sample according to the correlation coefficient of each echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of core samples.
In one embodiment, determining the total porosity of each core sample from the first wave amplitude values of the nuclear magnetic resonance echo data of each core sample comprises: the total porosity of each core sample was determined according to the following formula:
φk＝Echo_amp_1,k；
wherein phi iskIs the total porosity, φ, of the kth core samplek＝Echo_amp_1,kThe first wave amplitude value of the nuclear magnetic resonance echo data of the kth core sample is shown, wherein K is 1,2.
In one embodiment, determining the echo data enclosure area of each core sample according to the amplitude values of all echoes in the nuclear magnetic resonance echo data of each core sample comprises: determining the enclosed area of the echo data of each core sample according to the following formula:
wherein, EakThe area enclosed by echo data of the kth core sample, TE echo interval, Echo_amp_i,kThe amplitude value of the ith echo of the nuclear magnetic resonance echo data of the kth core sample is 1,2, … N, wherein N is the total number of echoes in the nuclear magnetic resonance echo data, and K is 1,2.
In one embodiment, determining the decay time of the echo data of each core sample according to the average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample comprises:
determining an amplitude average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample according to the following formula:
determining the time corresponding to the first echo amplitude value equal to the average amplitude value in the nuclear magnetic resonance echo data of each rock core sample as the echo data attenuation time of each rock core sample;
wherein E ischo_cf_kAmplitude average of kth core sample, Echo_amp_i,kN is an integer greater than N, which is the total number of echoes in the nuclear magnetic resonance echo data, and N is a preset positive integer.
In one embodiment, determining the optimal echo amplitude value of each core sample according to the correlation coefficient between each echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of a plurality of core samples comprises:
determining the correlation coefficient of each echo amplitude value and mercury injection saturation in nuclear magnetic resonance echo data of a plurality of core samples according to the following formula:
determining the echo serial number corresponding to the correlation coefficient with the largest median among the obtained correlation coefficients as the optimal echo serial number;
determining the optimal echo amplitude value of each rock core sample according to the optimal echo serial number and the nuclear magnetic resonance echo data of each rock core sample;
wherein R is_i(Eamp_i) The correlation coefficient between the ith echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of rock core samples is shown, wherein i is 2, 3.. N, and N is the total number of echoes in the nuclear magnetic resonance echo data; (E)amp_i)1×KAmplitude value E of the i-th echo for each of a plurality of core samplescho_amp_i,kForming a 1 × K matrix, K being 1K, wherein K is the total number of the core samples; (S)hg_j)1×KFor mercury filling saturation, for a predetermined mercury filling pressure Pc_jMercury injection saturation S for each of the next plurality of sampleshg_j,kA matrix of 1 × K is formed, j being 1,2.. m, m being the total number of preset mercury injection pressures.
In one embodiment, the target model is:
log(Shg_j)＝Dj+C1,j(log(φ))+C2,j(log(Ea))+C3,j(log(t_dec))+C4,j(log(Echo_amp_best))；
wherein S ishg_jTo at a preset mercury injection pressure Pc_jLower mercury injection saturation, phi, Ea, t_decAnd Echo_amp_bestIs at least one echo parameter, where φ is total porosity, Ea is echo data envelope area, t_decDecay time for echo data, Echo_amp_bestFor optimum echo amplitude values, Dj、C1,j、C2,j、C3,jAnd C4,jFor the target model at the preset mercury injection pressure Pc_jThe model coefficients are given below, wherein j is 1,2.. m, and m is the total number of preset mercury injection pressures.
The embodiment of the application also provides a device based on nuclear magnetic resonance echo data acquisition capillary pressure curve, includes: the acquisition module is used for acquiring nuclear magnetic resonance echo data of each core sample in a plurality of core samples of a target reservoir and the mercury injection saturation of each core sample in the plurality of core samples under each preset mercury injection pressure in a plurality of preset mercury injection pressures; the first determining module is used for determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample; the second determining module is used for determining a model coefficient of the target model under each preset mercury injection pressure according to at least one echo parameter of each core sample and the mercury injection saturation of each core sample under each preset mercury injection pressure; and the third determining module is used for determining a capillary pressure curve of the target reservoir according to the target model and the model coefficients of the target model under each preset mercury injection pressure.
An embodiment of the present application further provides a computer device, which includes a processor and a memory for storing processor-executable instructions, where the processor executes the instructions to implement the steps of the method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data described in any of the above embodiments.
Embodiments of the present application further provide a computer-readable storage medium, on which computer instructions are stored, and the instructions, when executed, implement the steps of the method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data described in any of the above embodiments.
In the embodiment of the application, a method for obtaining a capillary pressure curve based on nuclear magnetic resonance echo data is provided, the core data of a plurality of core samples of a target reservoir are obtained, the core data comprises nuclear magnetic resonance echo data and mercury injection saturation degrees under each pressure in a plurality of preset mercury injection pressures, echo parameters of each core sample are determined according to the echo data of each core sample, model coefficients of the target model under each preset mercury injection pressure are determined according to the echo parameters of all the core samples and the mercury injection saturation degrees under each preset mercury injection pressure, the target model is used for representing the relation between the mercury injection saturation degrees and the echo parameters, and then the capillary pressure curve of the target reservoir is determined according to the target model and the model coefficients of the target model under each preset mercury injection pressure. According to the scheme, the core data of a plurality of core samples of the target reservoir are obtained, the model coefficients of the target model under a plurality of mercury injection pressures are determined according to the core data, the capillary pressure curve of the target reservoir is determined according to the model and the determined model coefficients, inversion of nuclear magnetic resonance echo data is not needed, errors caused by the inversion of the echo data can be avoided, the calculated amount is effectively reduced, and the calculation precision is improved. By the scheme, the technical problem that the error of the existing method for acquiring the capillary pressure curve is large is solved, and the technical effects of effectively reducing the calculated amount and improving the calculation precision are achieved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application, are incorporated in and constitute a part of this application, and are not intended to limit the application. In the drawings:
FIG. 1 is a flow chart illustrating a method for obtaining a capillary pressure curve based on nuclear magnetic resonance echo data in an embodiment of the present application;
FIG. 2 is a schematic diagram illustrating the calculation of decay time of nuclear magnetic resonance echo data of a core sample according to an embodiment of the present disclosure;
FIG. 3 is a flow chart illustrating a method for calculating an optimal amplitude value of nuclear magnetic resonance echo data according to an embodiment of the present application;
FIG. 4 is a diagram illustrating an exemplary calculation of an optimal amplitude value of nuclear magnetic resonance echo data according to an embodiment of the present application;
fig. 5 shows a schematic of experimentally measured capillary pressure curves for a #4 core sample and capillary pressure curves predicted by the methods provided by the examples of the present application;
fig. 6 shows a schematic of experimentally measured capillary pressure curves for a #12 core sample and capillary pressure curves predicted by the methods provided by the examples of the present application;
fig. 7 shows a schematic of experimentally measured capillary pressure curves for a #16 core sample and capillary pressure curves predicted by the methods provided by the examples of the present application;
FIG. 8 shows a cross plot of experimentally measured displacement pressure values for 19 core samples versus displacement pressure values predicted by a method provided by an embodiment of the present application;
FIG. 9 shows a cross plot of experimentally measured median pressure values for 19 core samples versus median pressure values predicted by a method provided by an embodiment of the present application;
FIG. 10 is a schematic diagram of an apparatus for acquiring a capillary pressure curve based on NMR echo data in an embodiment of the present application;
FIG. 11 shows a schematic diagram of a computer device in an embodiment of the present application.
Detailed Description
The principles and spirit of the present application will be described with reference to a number of exemplary embodiments. It should be understood that these embodiments are given solely for the purpose of enabling those skilled in the art to better understand and to practice the present application, and are not intended to limit the scope of the present application in any way. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As will be appreciated by one skilled in the art, embodiments of the present application may be embodied as a system, apparatus, device, method or computer program product. Accordingly, the present disclosure may be embodied in the form of: entirely hardware, entirely software (including firmware, resident software, micro-code, etc.), or a combination of hardware and software.
In consideration of the fact that the existing scheme for acquiring the capillary pressure curve is to acquire the capillary pressure curve by inverting nuclear magnetic resonance echo data to obtain T2 distribution and then transforming T2 distribution, the inventor finds that the capillary pressure curve can be directly acquired through the nuclear magnetic resonance echo data without inverting the echo data because the inversion has larger errors and the acquired capillary pressure curve has larger errors, so that the inventor can avoid errors caused by the inversion, effectively improve the accuracy of the acquired capillary pressure curve and reduce the calculation amount.
Based on the above problems, an embodiment of the present application provides a method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data, and fig. 1 shows a flowchart of the method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data in an embodiment of the present application. Although the present application provides method operational steps or apparatus configurations as illustrated in the following examples or figures, more or fewer operational steps or modular units may be included in the methods or apparatus based on conventional or non-inventive efforts. In the case of steps or structures which do not logically have the necessary cause and effect relationship, the execution sequence of the steps or the module structure of the apparatus is not limited to the execution sequence or the module structure described in the embodiments and shown in the drawings of the present application. The described methods or modular structures may be implemented sequentially or concurrently in accordance with embodiments or with connections of the figures, as may be used in an apparatus or end product in practice, for example, in a parallel processor or multi-threaded processing environment or even a distributed processing environment.
Specifically, as shown in fig. 1, a method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data according to an embodiment of the present application may include the following steps:
step S101, obtaining nuclear magnetic resonance echo data of each core sample in a plurality of core samples of a target reservoir and mercury injection saturation of each core sample in the plurality of core samples under each preset mercury injection pressure in a plurality of preset mercury injection pressures.
Specifically, a plurality of core samples of the target reservoir may be obtained first, and the nuclear magnetic resonance echo data of each core sample and the mercury injection saturation of each core sample under each preset mercury injection pressure (that is, the capillary pressure curve of each core sample may be obtained) may be obtained by performing the nuclear magnetic resonance experiment on each core sample among the plurality of core samples and performing the high-pressure mercury injection experiment under a plurality of preset mercury injection pressures. The nuclear magnetic resonance echo data includes echo amplitude values of a plurality of echoes and corresponding moments, and a time interval between adjacent echoes is referred to as an echo interval TE.
And S102, determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample.
And S103, determining a model coefficient of the target model under each preset mercury injection pressure according to at least one echo parameter of each core sample and the mercury injection saturation of each core sample under each preset mercury injection pressure.
After obtaining the nmr echo data of each core sample, at least one echo parameter of each core sample may be determined from the nmr echo data of each core sample. The target model is a preset model and is used for representing the relation between the mercury injection saturation and at least one echo parameter, and the target model comprises a plurality of to-be-determined model coefficients. Therefore, the determined at least one echo parameter of all core samples and the mercury injection saturation of all core samples under the preset mercury injection pressure are substituted into the target model to obtain model coefficients of the target model under each preset mercury injection pressure in a plurality of preset mercury injection pressures, that is, one preset mercury injection pressure corresponds to one determined target model. For example, the model coefficients may be solved by performing a multiple linear regression analysis on the target model using at least one echo parameter of each of the plurality of core samples and a mercury injection saturation of each core sample at a predetermined mercury injection pressure. It is understood that other methods may be used to solve the model coefficients, and the present application is not limited in this respect.
And step S104, determining a capillary pressure curve of the target reservoir according to the target model and the model coefficients of the target model under each preset mercury injection pressure.
After determining the model coefficients of the target model under each preset pressure, the capillary pressure curve of the target reservoir can be determined according to the target model and the model coefficients of the target model under each preset mercury injection pressure, that is, according to the determined target model under each preset mercury injection pressure. Wherein, the capillary pressure curve can be a relation curve between the mercury injection pressure and the mercury injection saturation. Specifically, nuclear magnetic resonance echo data of each layer of a target reservoir can be obtained, at least one echo parameter of the target reservoir is determined according to the nuclear magnetic resonance echo data of each layer, mercury injection saturation under each preset mercury injection pressure is determined according to the at least one echo parameter and a target model under each preset mercury injection pressure, and then a capillary pressure curve of the target reservoir is determined according to each preset mercury injection pressure and mercury injection saturation under each preset mercury injection pressure.
According to the scheme, the core data of a plurality of core samples of the target reservoir are obtained, the model coefficients of the target model under a plurality of mercury injection pressures are determined according to the core data, the capillary pressure curve of the target reservoir is determined according to the model and the determined model coefficients, inversion of nuclear magnetic resonance echo data is not needed, errors caused by the inversion of the echo data can be avoided, the calculated amount is effectively reduced, and the accuracy is improved.
Further, in some embodiments of the present application, the at least one echo parameter may comprise at least one of: total porosity, echo data enclosed area, echo data decay time and optimal echo amplitude value. Correspondingly, determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample may include at least one of: determining the total porosity of each core sample according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample; determining the echo data surrounding area of each rock core sample according to the amplitude values of all echoes in the nuclear magnetic resonance echo data of each rock core sample; determining the attenuation time of the echo data of each rock core sample according to the average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each rock core sample; and determining the optimal echo amplitude value of each core sample according to the correlation coefficient of each echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of core samples.
Specifically, after the nuclear magnetic resonance echo data of each core sample is acquired, the total porosity of each core sample can be determined according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample. The head wave amplitude value refers to the amplitude value of the first echo in the nuclear magnetic resonance echo data. The echo data enclosure area of each core sample can be determined according to the amplitude values and the echo intervals of all echoes in the nuclear magnetic resonance echo data of each core sample. The echo data attenuation time of each core sample can be determined according to an average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of the core sample, wherein the plurality of echo amplitude values can be amplitude values of a plurality of echoes which are later in time in the echo data. The optimal echo amplitude value of each core sample can be determined according to the correlation coefficient of each echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of core samples. The optimal echo amplitude value may be an echo amplitude value corresponding to an echo with the highest correlation with mercury injection saturation. And when determining the correlation coefficient between each echo amplitude value and the mercury injection saturation, comprehensively considering the echo amplitude values of the plurality of core samples and the mercury injection saturation of the plurality of core samples under a plurality of preset mercury injection pressures. By the method, at least one echo parameter of each core sample can be determined according to the nuclear magnetic resonance echo data.
Further, in some embodiments of the present application, determining the total porosity of each core sample according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample may include: the total porosity of each core sample was determined according to the following formula:
φk＝Echo_amp_1,k；
wherein phi iskIs the total porosity, φ, of the kth core samplek＝Echo_amp_1,kThe first wave amplitude value of the nuclear magnetic resonance echo data of the kth core sample is shown, wherein K is 1,2.
Further, in some embodiments of the present application, determining an echo data enclosure area of each core sample according to amplitude values of all echoes in the nuclear magnetic resonance echo data of each core sample may include: determining the enclosed area of the echo data of each core sample according to the following formula:
wherein, EakThe area enclosed by echo data of the kth core sample, TE echo interval, Echo_amp_i,kThe amplitude value of the ith echo of the nuclear magnetic resonance echo data of the kth core sample is 1,2, … N, wherein N is the total number of echoes in the nuclear magnetic resonance echo data, and K is 1,2.
Further, in some embodiments of the present application, determining the decay time of the echo data of each core sample according to an average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample may include:
determining an amplitude average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample according to the following formula:
determining the time corresponding to the first echo amplitude value equal to the amplitude average value of the corresponding core sample in the nuclear magnetic resonance echo data of each core sample as the echo data attenuation time of each core sample, namely t _ deck＝i_cf_k·TE；
Wherein E ischo_cf_kAmplitude average of kth core sample, Echo_amp_i,kN, where N is an integer greater than N, is the total number of echoes in the nuclear magnetic resonance echo data, N is a preset positive integer, and t _ dec is a preset positive integerkDecay time of echo data for kth core sample, i_cf_kFor the first and E in the NMR echo data of the kth core samplecho_cf_kThe serial numbers corresponding to the equal echoes, TE, are the echo intervals. Where N is much greater than N. For example, n can range from 50 to 100.
Specifically, when determining the decay time of the echo data of each core sample, the reciprocal n echoes in the wave data are retrieved, and the average value E of the amplitudes of the n echoes is calculatedcho_cf_kThen determining the amplitude average value Echo_cf_kTime t _ dec corresponding to a first intersection of echo data of the core samplekThe time t _ deckDetermining the decay time of the echo data of the core sample. Fig. 2 is a schematic diagram illustrating the calculation of decay time of nmr echo data of a core sample according to an embodiment of the present disclosure. In fig. 2, the echo data, i.e. the echo amplitude value versus time curve, of a core sample is shown, the amplitude mean value E of which is determinedcho_cfThen, the amplitude average value E is determinedcho_cfThe first intersection point of the echo data curve and the corresponding moment of the intersection point is the attenuation time t of the echo data of the rock core sample_dec. It will be appreciated that the echo data may be an echo data curve, i.e. an echo amplitude value versus time, where time is the product of the echo sequence number and the time interval.
Further, in some embodiments of the present application, determining an optimal echo amplitude value of each core sample according to a correlation coefficient between each echo amplitude value and mercury injection saturation in nuclear magnetic resonance echo data of a plurality of core samples may include:
determining the correlation coefficient of each echo amplitude value and mercury injection saturation in nuclear magnetic resonance echo data of a plurality of core samples according to the following formula:
determining the echo serial number corresponding to the correlation coefficient with the largest median among the obtained correlation coefficients as the optimal echo serial number;
determining the optimal echo amplitude value of each rock core sample according to the optimal echo serial number and the nuclear magnetic resonance echo data of each rock core sample;
wherein R is_i(Eamp_i) The correlation coefficient between the ith echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of rock core samples is shown, wherein i is 2, 3.. N, and N is the total number of echoes in the nuclear magnetic resonance echo data; (E)amp_i)1×KAmplitude value E of the i-th echo for each of a plurality of core samplescho_amp_i,kA formed 1 × K matrix, wherein K is 1,2.. K, and K is the total number of the core samples, (S)hg_j)1×KFor mercury filling saturation, for a predetermined mercury filling pressure Pc_jMercury injection saturation S for each of the next plurality of sampleshg_j,kA matrix of 1 × K is formed, j being 1,2.. m, m being the total number of preset mercury injection pressures.
Referring to fig. 3, fig. 3 is a flowchart illustrating a procedure of calculating an optimal amplitude value of nuclear magnetic resonance echo data according to an embodiment of the present application. As shown in FIG. 3, at each mercury injection pressure, the mercury injection saturations for all core samples form a matrix of (S)hg_j)1×KAbbreviated as S in FIG. 3hg_jJ is 1,2, … m; under the ith echo, the matrix formed by the nuclear magnetic resonance echo data amplitude values of all the rock core samples is (E)amp_i)1×KAbbreviated as E in FIG. 3amp_i. Calculate E at each echoamp_iAnd Shg_jIs related to coefficient R_i,jJ is 1,2, … m, and the correlation number R_i,jAveraging after summing to obtain a correlation coefficient R of the ith echo amplitude value and mercury injection saturation_i. Then, R is obtained_iMaximum value of R_hDetermining the optimal echo sequence number as h, the kth sample is the mostThe value of the excellent echo amplitude is Echo_amp_h,kK is 1,2. Referring to fig. 4, fig. 4 is a schematic diagram illustrating a calculation of an optimal amplitude value of nuclear magnetic resonance echo data according to an embodiment of the present application. As shown in fig. 4, by plotting a relationship curve between the correlation coefficient and time (time is a product of the echo sequence number and the echo interval), a time corresponding to the maximum correlation coefficient can be determined, and the time is divided by the echo interval to obtain an echo sequence number h, and then the optimal echo amplitude value of each core sample can be obtained according to the echo sequence number h and the echo data of each core sample. Wherein the upper right graph of fig. 4 is an enlarged view of the correlation coefficient versus time graph between 0ms and 90ms, the maximum correlation coefficient R can be found_hMaximum correlation coefficient R_hThe echo amplitude value corresponding to the corresponding echo sequence number h is the optimal amplitude value, namely
Wherein E ischo_amp_best_kThe optimal echo amplitude value for the kth sample.
Further, in some embodiments of the present application, the target model may be:
log(Shg_j)＝Dj+C1,j(log(φ))+C2,j(log(Ea))+C3,j(log(t_dec))+C4,j(log(Echo_amp_best))；
wherein S ishg_jTo at a preset mercury injection pressure Pc_jLower mercury injection saturation, phi, Ea, t_decAnd Echo_amp_bestIs at least one echo parameter, where φ is total porosity, Ea is echo data envelope area, t_decDecay time for echo data, Echo_amp_bestFor optimum echo amplitude values, Dj、C1,j、C2,j、C3,jAnd C4,jFor the target model at the preset mercury injection pressure Pc_jThe model coefficients are given below, wherein j is 1,2.. m, and m is the total number of preset mercury injection pressures.
The target model may be derived by:
sezginer formula for permeability calculation based on nuclear magnetic resonance echo data:
wherein A, B is a model coefficient; k is the core permeability; HI is hydrogen index; phi is porosity; TE is the echo spacing;<T2>the relaxation time average is.
The L everett J function characterizing reservoir properties is:
wherein: pcIs capillary pressure; σ is the interfacial tension; θ is the contact angle of the inner surface of the fluid and the pore wall; k is the core permeability; phi is the core porosity; j (S)w) Is a dimensionless function; swIs the water saturation, and J (S)w) Are in a power function relationship.
The two formulas are combined to obtain:
wherein a, b and c are model coefficients.
Due to non-wetting phase saturation Snw(i.e. mercury injection saturation S)hg) Saturation with wetting phase Sw(i.e., water saturation) there is a relationship: snw+Sw1 (i.e. S)hg+Sw1). In the above formula, at a given mercury injection pressure PcNext, there is a correlation between J (Sw) and φ, Ea, whereby it can be understood that the mercury injection saturation S is given for each mercury injection pressurehgThere is a certain correlation between phi and Ea, and is marked as Shg～log(Ep)，EpIs at least one echo parameter of the nuclear magnetic resonance echo data. In the Sezginer formula for evaluating formation permeability based on NMR echo data in NMR logging, only two parameters are considered, while in practical application, permeability and at least one echo parameter (total porosity phi, echo) of the NMR echo dataArea Ea enclosed by data, echo data attenuation time t_decAnd echo data amplitude value Echo_amp) Are all related, therefore, for each mercury injection pressure Pc_jEstablishing mercury injection saturation ShgAt least one echo parameter E associated with the echo datapThe relationship of (a) to (b) is as follows:
log(Shg_j)＝Dj+Cl,j(log(Ep))(j＝1:m；l＝1:n)；
wherein: m is the number of mercury injection pressure points, n is the number of nuclear magnetic resonance echo data parameters, log (S)hg_j) Is a pressure of Pc_jMercury filling saturation S of all sampleshg,jOf the logarithmic values of DjIs a constant number, Cl,jAs model coefficient, log (E)p) For extracting echo parameters E in nuclear magnetic resonance echo data participating in modelingpLogarithmic value of (E)pMay include total porosity φ, area Ea enclosed by echo data, echo data decay time t_decAnd an optimum echo data amplitude value Echo_amp_best。
Thus, each mercury injection pressure point Pc_jNext, the target model established for obtaining the capillary pressure curve based on the nmr echo data is expressed as follows:
log(Shg_j)＝Dj+C1,j(log(φ))+C2,j(log(Ea))+C3,j(log(t_dec))+C4,j(log(Echo_amp_best))；
wherein S ishg_jTo at a preset mercury injection pressure Pc_jLower mercury injection saturation, phi is total porosity, Ea is echo data enclosing area, t_decDecay time for echo data, Echo_amp_bestFor optimum echo amplitude values, Dj、C1,j、C2,j、C3,jAnd C4,jFor the target model at the preset mercury injection pressure Pc_jThe model coefficients are given below, wherein j is 1,2.. m, and m is the total number of preset mercury injection pressures.
The above method is described below with reference to a specific example, however, it should be noted that the specific example is only for better describing the present application and is not to be construed as limiting the present application.
In this embodiment, the method for obtaining a capillary pressure curve based on nuclear magnetic resonance echo data may include the following steps:
φk＝Echo_amp_1,k；
wherein phi iskIs the total porosity, φ, of the kth core samplek＝Echo_amp_1,kThe first wave amplitude value of the nuclear magnetic resonance echo data of the kth core sample is obtained, wherein K is 1,2.. K, and K is the number of the plurality of core samples;
wherein, EakThe area enclosed by echo data of the kth core sample, TE echo interval, Echo_amp_i,kThe amplitude value of the ith echo of the nuclear magnetic resonance echo data of the kth core sample is 1,2, … N, wherein N is the total number of echoes in the nuclear magnetic resonance echo data, and K is 1,2,. K, and K is the total number of the plurality of core samples;
determining the time corresponding to the first echo amplitude value equal to the average amplitude value in the nuclear magnetic resonance echo data of each core sample as each core sampleDecay time of echo data of the article, i.e. t _ deck＝i_cf_k·TE；
Wherein E ischo_cf_kAmplitude average of kth core sample, Echo_amp_i,kN, where N is an integer greater than N, is the total number of echoes in the nuclear magnetic resonance echo data, N is a preset positive integer, and t _ dec is a preset positive integerkDecay time of echo data for kth core sample, i_cf_kFor the first and E in the NMR echo data of the kth core samplecho_cf_kThe serial numbers corresponding to the equal echoes, TE is the echo interval;
and 5, determining the correlation coefficient of each echo amplitude value and mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of rock core samples according to the following formula:
determining the echo sequence number corresponding to the correlation coefficient with the largest median among the obtained correlation coefficients as the optimal echo sequence number, namely R_h＝max(R_i) H is the optimal echo sequence number;
determining the optimal echo amplitude value of each core sample according to the optimal echo serial number and the nuclear magnetic resonance echo data of each core sample, namely
Wherein R is_i(Eamp_i) The correlation coefficient between the ith echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of rock core samples is shown, wherein i is 2, 3.. N, and N is the total number of echoes in the nuclear magnetic resonance echo data; (E)amp_i)1×KAmplitude value E of the i-th echo for each of a plurality of core samplescho_amp_i,kA formed 1 × K matrix, wherein K is 1,2.. K, and K is the total number of the core samples, (S)hg_j)1×KFor mercury filling saturation, for a predetermined mercury filling pressure Pc_jThe mercury injection of each of the next plurality of samples was saturatedDegree of neutralization Shg_j,kA matrix of 1 × K is formed, j is 1,2,. m, m is the total number of preset mercury injection pressures, Echo_amp_best_kThe optimal echo amplitude value of the kth sample is obtained;
log(Shg_j)＝Dj+C1,j(log(φ))+C2,j(log(Ea))+C3,j(log(t_dec))+C4,j(log(Echo_amp_best))；
wherein S ishg_jTo at a preset mercury injection pressure Pc_jLower mercury injection saturation, phi, Ea, t_decAnd Echo_amp_bestIs at least one echo parameter, where φ is total porosity, Ea is echo data envelope area, t_decDecay time for echo data, Echo_amp_bestFor optimum echo amplitude values, Dj、C1,j、C2,j、C3,jAnd C4,jFor the target model at the preset mercury injection pressure Pc_jThe model coefficients are given, wherein j is 1,2.. m, and m is the total number of preset mercury injection pressures;
step 9, determining mercury injection saturation degrees under a plurality of preset mercury injection pressures in each layer according to the extracted echo parameters and the target model;
and step 10, determining a capillary pressure curve of the target reservoir according to the corresponding relation between the mercury injection saturation and the preset mercury injection pressure.
The method for acquiring the capillary pressure curve based on the nuclear magnetic resonance echo data constructed in the above embodiment predicts the capillary pressure curves of the three samples with large differences in physical properties # 4, #12 and # 16. In the present implementation, 19 core samples are collected, wherein three core samples # 4, #12, #16 are used as a prediction set, and the remaining 16 cores are used as a training set, so as to construct a model for predicting the tight sandstone capillary pressure curve based on nuclear magnetic resonance echo data. Referring to fig. 5, 6 and 7, fig. 5 shows a schematic diagram of a capillary pressure curve experimentally measured for a #4 core sample and predicted by a method provided by an embodiment of the present application; fig. 6 shows a schematic of experimentally measured capillary pressure curves for a #12 core sample and capillary pressure curves predicted by the methods provided by the examples of the present application; fig. 7 shows a schematic of experimentally measured capillary pressure curves for a #16 core sample and capillary pressure curves predicted by the methods provided by the examples of the present application. In fig. 5, 6 and 7, the solid line is the result predicted by the method provided in the examples of the present application, and the dot is the capillary pressure curve measured by the high-pressure mercury intrusion test. As can be seen from fig. 5, 6 and 7, the predicted capillary pressure curve has higher accuracy, which indicates that the method provided by the present application has higher reliability and stability.
The displacement pressure value and the median pressure value of 19 core samples are predicted by using the method for acquiring the capillary pressure curve based on the nuclear magnetic resonance echo data, which is constructed in the embodiment. Referring to fig. 8 and 9, fig. 8 shows a cross-plot of experimentally measured displacement pressure values of 19 core samples with displacement pressure values predicted by the method provided by the embodiments of the present application; fig. 9 shows a cross plot of experimentally measured median pressure values for 19 core samples versus the median pressure values predicted by the methods provided by embodiments of the present application. In FIG. 8, Pd"predict" is the displacement pressure value, P, predicted according to the method provided in the present applicationd"measured" is the displacement pressure value measured through the experiment, R is the correlation coefficient between the predicted displacement pressure value and the displacement pressure value measured through the experiment, and RMSE is the root mean square error between the predicted displacement pressure value and the displacement pressure value measured through the experiment. In FIG. 9, Pc50"predict" is the displacement pressure value, P, predicted according to the method provided in the present applicationc50Measured is the measured displacementAnd the pressure value, R is a correlation coefficient of the predicted median pressure value and the experimentally measured median pressure value, and RMSE is the root mean square error of the predicted median pressure value and the experimentally measured median pressure value. As can be seen from fig. 8 and 9, the correlation between the displacement pressure value predicted by the target model provided by the present application and the displacement pressure value actually measured is high, and the root mean square error is low, and the correlation between the median pressure value predicted by the target model provided by the present application and the median pressure value actually measured is high, and the root mean square error is low, which indicates that the performance of the model is stable and the prediction error is small.
Based on the same inventive concept, the embodiment of the present application further provides a device for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data, as described in the following embodiments. The principle of solving the problems of the device for acquiring the capillary pressure curve based on the nuclear magnetic resonance echo data is similar to that of the method for acquiring the capillary pressure curve based on the nuclear magnetic resonance echo data, so the implementation of the device for acquiring the capillary pressure curve based on the nuclear magnetic resonance echo data can refer to the implementation of the method for acquiring the capillary pressure curve based on the nuclear magnetic resonance echo data, and repeated parts are not repeated. As used hereinafter, the term "unit" or "module" may be a combination of software and/or hardware that implements a predetermined function. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware, or a combination of software and hardware is also possible and contemplated. Fig. 10 is a block diagram of a structure of an apparatus for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data according to an embodiment of the present application, as shown in fig. 10, including: an acquisition module 1001, a first determination module 1002, a second determination module 1003, and a third determination module 1004, the structure of which will be described below.
The obtaining module 1001 is configured to obtain nuclear magnetic resonance echo data of each core sample in a plurality of core samples of a target reservoir and a mercury injection saturation of each core sample in the plurality of core samples at each preset mercury injection pressure in a plurality of preset mercury injection pressures.
The first determining module 1002 is configured to determine at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample.
The second determining module 1003 is configured to determine a model coefficient of the target model at each preset mercury injection pressure according to at least one echo parameter of each core sample and the mercury injection saturation of each core sample at each preset mercury injection pressure.
The third determining module 1004 is configured to determine a capillary pressure curve of the target reservoir according to the target model and the model coefficients of the target model under each preset mercury injection pressure.
In some embodiments of the present application, the at least one echo parameter may comprise at least one of: the method comprises the following steps of (1) total porosity, echo data surrounding area, echo data attenuation time and an optimal echo amplitude value; the first determining module may be specifically configured to at least one of: determining the total porosity of each core sample according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample; determining the echo data surrounding area of each rock core sample according to the amplitude values of all echoes in the nuclear magnetic resonance echo data of each rock core sample; determining the attenuation time of the echo data of each rock core sample according to the average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each rock core sample; and determining the optimal echo amplitude value of each core sample according to the correlation coefficient of each echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of core samples.
In some embodiments of the present application, determining the total porosity of each core sample according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample may include: the total porosity of each core sample was determined according to the following formula:
φk＝Echo_amp_1,k；
wherein phi iskIs the total porosity, φ, of the kth core samplek＝Echo_amp_1,kThe first wave amplitude value of the nuclear magnetic resonance echo data of the kth core sample is shown, wherein K is 1,2.
In some embodiments of the present application, determining an echo data enclosure area of each core sample according to amplitude values of all echoes in the nuclear magnetic resonance echo data of each core sample may include: determining the enclosed area of the echo data of each core sample according to the following formula:
wherein, EakThe area enclosed by echo data of the kth core sample, TE echo interval, Echo_amp_i,kThe amplitude value of the ith echo of the nuclear magnetic resonance echo data of the kth core sample is 1,2, … N, wherein N is the total number of echoes in the nuclear magnetic resonance echo data, and K is 1,2.
In some embodiments of the present application, determining the decay time of the echo data of each core sample according to an average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample may include:
determining an amplitude average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample according to the following formula:
determining the time corresponding to the first echo amplitude value equal to the average amplitude value in the nuclear magnetic resonance echo data of each rock core sample as the echo data attenuation time of each rock core sample;
wherein E ischo_cf_kAmplitude average of kth core sample, Echo_amp_i,kAnd the amplitude value of the ith echo of the kth core sample is i ═ N-N +1, N-N +2 and … N, wherein N is an integer larger than N and is the total number of echoes in the nuclear magnetic resonance echo data, and N is a preset positive integer.
In some embodiments of the present application, determining an optimal echo amplitude value of each core sample according to a correlation coefficient between each echo amplitude value and mercury injection saturation in nuclear magnetic resonance echo data of a plurality of core samples may include:
determining the correlation coefficient of each echo amplitude value and mercury injection saturation in nuclear magnetic resonance echo data of a plurality of core samples according to the following formula:
determining the echo serial number corresponding to the correlation coefficient with the largest median among the obtained correlation coefficients as the optimal echo serial number;
determining the optimal echo amplitude value of each rock core sample according to the optimal echo serial number and the nuclear magnetic resonance echo data of each rock core sample;
wherein R is_i(Eamp_i) The correlation coefficient between the ith echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of rock core samples is shown, wherein i is 2, 3.. N, and N is the total number of echoes in the nuclear magnetic resonance echo data; (E)amp_i)1×KAmplitude value E of the i-th echo for each of a plurality of core samplescho_amp_i,kA formed 1 × K matrix, wherein K is 1,2.. K, and K is the total number of the core samples, (S)hg_j)1×KFor mercury filling saturation, for a predetermined mercury filling pressure Pc_jMercury injection saturation S for each of the next plurality of sampleshg_j,kA matrix of 1 × K is formed, j being 1,2.. m, m being the total number of preset mercury injection pressures.
In some embodiments of the present application, the target model may be:
log(Shg_j)＝Dj+C1,j(log(φ))+C2,j(log(Ea))+C3,j(log(t_dec))+C4,j(log(Echo_amp_best))；
wherein S ishg_jTo at a preset mercury injection pressure Pc_jLower mercury injection saturation, phi, Ea, t_decAnd Echo_amp_bestIs at least one echo parameter, where φ is total porosity, Ea is echo data envelope area, t_decDecay time for echo data, Echo_amp_bestFor optimum echo amplitude values, Dj、C1,j、C2,j、C3,jAnd C4,jFor the target model at the preset mercury injection pressure Pc_jThe model coefficients are given below, wherein j is 1,2.. m, and m is the total number of preset mercury injection pressures.
From the above description, it can be seen that the embodiments of the present application achieve the following technical effects: by acquiring the core data of a plurality of core samples of the target reservoir, determining the model coefficients of the target model under a plurality of mercury injection pressures according to the core data, and determining the capillary pressure curve of the target reservoir according to the model and the determined model coefficients, the inversion of nuclear magnetic resonance echo data is not needed, the error caused by the inversion of the echo data can be avoided, the calculated amount is effectively reduced, and the accuracy is improved. By the scheme, the technical problem that the error of the existing method for acquiring the capillary pressure curve is large is solved, and the technical effects of effectively reducing the calculated amount and improving the calculation precision are achieved.
The embodiment of the present application further provides a computer device, which may specifically refer to fig. 11, which is a schematic structural diagram of a computer device according to the method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data provided in the embodiment of the present application, and the computer device may specifically include an input device 111, a processor 112, and a memory 113. Wherein the memory 113 is configured to store processor-executable instructions. The processor 112 when executing the instructions performs the steps of the method for obtaining a capillary pressure curve based on nuclear magnetic resonance echo data as described in any of the embodiments above. The input device 31 may be specifically configured to input nuclear magnetic resonance echo data and preset mercury injection pressures of a plurality of core samples and corresponding mercury injection saturations.
In this embodiment, the input device may be one of the main apparatuses for information exchange between a user and a computer system. The input device may include a keyboard, a mouse, a camera, a scanner, a light pen, a handwriting input board, a voice input device, etc.; the input device is used to input raw data and a program for processing the data into the computer. The input device can also acquire and receive data transmitted by other modules, units and devices. The processor may be implemented in any suitable way. For example, the processor may take the form of, for example, a microprocessor or processor and a computer-readable medium that stores computer-readable program code (e.g., software or firmware) executable by the (micro) processor, logic gates, switches, an Application Specific Integrated Circuit (ASIC), a programmable logic controller, an embedded microcontroller, and so forth. The memory may in particular be a memory device used in modern information technology for storing information. The memory may include multiple levels, and in a digital system, the memory may be any memory as long as it can store binary data; in an integrated circuit, a circuit without a physical form and with a storage function is also called a memory, such as a RAM, a FIFO and the like; in the system, the storage device in physical form is also called a memory, such as a memory bank, a TF card and the like.
In this embodiment, the functions and effects of the specific implementation of the computer device can be explained in comparison with other embodiments, and are not described herein again.
The present application further provides a computer storage medium for a method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data, where the computer storage medium stores computer program instructions, and the computer program instructions, when executed, implement the steps of the method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data in any of the above embodiments.
In the present embodiment, the storage medium includes, but is not limited to, a Random Access Memory (RAM), a Read-Only Memory (ROM), a Cache (Cache), a Hard disk (HDD), or a Memory Card (Memory Card). The memory may be used to store computer program instructions. The network communication unit may be an interface for performing network connection communication, which is set in accordance with a standard prescribed by a communication protocol.
In this embodiment, the functions and effects specifically realized by the program instructions stored in the computer storage medium can be explained by comparing with other embodiments, and are not described herein again.
It will be apparent to those skilled in the art that the modules or steps of the embodiments of the present application described above may be implemented by a general purpose computing device, they may be centralized on a single computing device or distributed across a network of multiple computing devices, and alternatively, they may be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by a computing device, and in some cases, the steps shown or described may be performed in an order different from that described herein, or they may be separately fabricated into individual integrated circuit modules, or multiple ones of them may be fabricated into a single integrated circuit module. Thus, embodiments of the present application are not limited to any specific combination of hardware and software.
It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and many applications other than the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the application should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the pending claims along with the full scope of equivalents to which such claims are entitled.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and it will be apparent to those skilled in the art that various modifications and variations can be made in the embodiment of the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (9)
1. A method for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data is characterized by comprising the following steps:
acquiring nuclear magnetic resonance echo data of each core sample in a plurality of core samples of a target reservoir and the mercury injection saturation of each core sample in the plurality of core samples under each preset mercury injection pressure in a plurality of preset mercury injection pressures;
determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample, wherein the at least one echo parameter comprises at least one of the following parameters: the method comprises the following steps of (1) total porosity, echo data surrounding area, echo data attenuation time and an optimal echo amplitude value;
determining a model coefficient of a target model under each preset mercury injection pressure according to at least one echo parameter of each core sample and the mercury injection saturation of each core sample under each preset mercury injection pressure;
determining a capillary pressure curve of the target reservoir according to the target model and model coefficients of the target model under each preset mercury injection pressure;
determining at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample, wherein the at least one echo parameter comprises at least one of the following parameters:
determining the total porosity of each core sample according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample;
determining the echo data surrounding area of each rock core sample according to the amplitude values of all echoes in the nuclear magnetic resonance echo data of each rock core sample;
determining the attenuation time of the echo data of each rock core sample according to the average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each rock core sample;
and determining the optimal echo amplitude value of each core sample according to the correlation coefficient of each echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of core samples.
2. The method of claim 1, wherein determining the total porosity of each core sample from the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample comprises:
determining the total porosity of each core sample according to the following formula:
φk＝Echo_amp_1,k；
wherein phi iskIs the total porosity, φ, of the kth core samplek＝Echo_amp_1,kAnd the first wave amplitude value of the nuclear magnetic resonance echo data of the kth core sample is obtained, wherein K is 1,2.
3. The method according to claim 1, wherein determining the echo data envelope area of each core sample according to the amplitude values of all echoes in the nuclear magnetic resonance echo data of each core sample comprises:
determining the enclosed area of the echo data of each core sample according to the following formula:
wherein, EakThe area enclosed by echo data of the kth core sample, TE echo interval, Echo_amp_i,kThe amplitude value of the ith echo of the nuclear magnetic resonance echo data of the kth core sample is 1,2, … N, wherein N is the total number of echoes in the nuclear magnetic resonance echo data, and K is 1,2.
4. The method according to claim 1, wherein determining the decay time of the echo data of each core sample from an average of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample comprises:
determining an amplitude average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each core sample according to the following formula:
determining the time corresponding to the first echo amplitude value equal to the average amplitude value in the nuclear magnetic resonance echo data of each core sample as the echo data attenuation time of each core sample;
wherein E ischo_cf_kAmplitude average of kth core sample, Echo_amp_i,kAnd the amplitude value of the ith echo of the kth core sample is i ═ N-N +1, N-N +2 and … N, wherein N is an integer larger than N and is the total number of echoes in the nuclear magnetic resonance echo data, and N is a preset positive integer.
5. The method according to claim 1, wherein determining the optimal echo amplitude value of each core sample according to a correlation coefficient between each echo amplitude value and mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of core samples comprises:
determining a correlation coefficient between each echo amplitude value and mercury injection saturation in nuclear magnetic resonance echo data of the plurality of core samples according to the following formula:
determining the echo serial number corresponding to the correlation coefficient with the largest median among the obtained correlation coefficients as the optimal echo serial number;
determining the optimal echo amplitude value of each rock core sample according to the optimal echo serial number and the nuclear magnetic resonance echo data of each rock core sample;
wherein R is_i(Eamp_i) The correlation coefficient of the ith echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of rock core samples is (i is 2, 3.. N, and N is the total number of echoes in the nuclear magnetic resonance echo data); (E)amp_i)1×KAn amplitude value E of the ith echo of each of the plurality of core samplescho_amp_i,kA formed 1 × K matrix, wherein K is 1,2.. K, and K is the total number of the core samples, (S)hg_j)1×KFor the mercury injection saturation, at a predetermined mercury injection pressure Pc_jMercury injection saturation S for each of the next plurality of sampleshg_j,kA matrix of 1 × K is formed, j being 1,2.. m, m being the total number of preset mercury injection pressures.
6. The method of claim 1, wherein the target model is:
log(Shg_j)＝Dj+C1,j(log(φ))+C2,j(log(Ea))+C3,j(log(t_dec))+C4,j(log(Echo_amp_best))；
wherein S ishg_jTo at a preset mercury injection pressure Pc_jLower mercury injection saturation, phi, Ea, t_decAnd Echo_amp_bestIs the at least one echo parameter, where φ is total porosity, Ea is echo data envelope area, t_decDecay time for echo data, Echo_amp_bestFor optimum echo amplitude values, Dj、C1,j、C2,j、C3,jAnd C4,jSetting the preset mercury injection pressure P for the target modelc_jThe model coefficients of (a), where j is 1,2.. m, and m is the total number of the preset mercury injection pressures.
7. A device for acquiring a capillary pressure curve based on nuclear magnetic resonance echo data is characterized by comprising:
the acquisition module is used for acquiring nuclear magnetic resonance echo data of each core sample in a plurality of core samples of a target reservoir and the mercury injection saturation of each core sample in the plurality of core samples under each preset mercury injection pressure in a plurality of preset mercury injection pressures;
a first determining module, configured to determine at least one echo parameter of each core sample according to the nuclear magnetic resonance echo data of each core sample, where the at least one echo parameter includes at least one of: the method comprises the following steps of (1) total porosity, echo data surrounding area, echo data attenuation time and an optimal echo amplitude value;
the second determining module is used for determining model coefficients of the target model under each preset mercury injection pressure according to at least one echo parameter of each core sample and the mercury injection saturation of each core sample under each preset mercury injection pressure;
the third determination module is used for determining a capillary pressure curve of the target reservoir according to the target model and model coefficients of the target model under each preset mercury injection pressure;
the first determining module is specifically configured to at least one of:
determining the total porosity of each core sample according to the first wave amplitude value of the nuclear magnetic resonance echo data of each core sample;
determining the echo data surrounding area of each rock core sample according to the amplitude values of all echoes in the nuclear magnetic resonance echo data of each rock core sample;
determining the attenuation time of the echo data of each rock core sample according to the average value of a plurality of echo amplitude values in the nuclear magnetic resonance echo data of each rock core sample;
and determining the optimal echo amplitude value of each core sample according to the correlation coefficient of each echo amplitude value and the mercury injection saturation in the nuclear magnetic resonance echo data of the plurality of core samples.
8. A computer device comprising a processor and a memory for storing processor-executable instructions that, when executed by the processor, implement the steps of the method of any one of claims 1 to 6.
9. A computer-readable storage medium having computer instructions stored thereon which, when executed, implement the steps of the method of any one of claims 1 to 6.
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