A method for judging the rationality of a nuclear magnetic resonance power function relation

Abstract

The present invention relates to the technical field of oil and gas field development, and particularly relates to a method for judging the rationality of a nuclear magnetic resonance power function relation. A method for judging the rationality of a nuclear magnetic resonance power function relation is to respectively construct the value range of the power exponent n and the value range of the conversion coefficient C ; if the value of the power exponent n and the value of the conversion coefficient C obtained by other methods both fall within the above value ranges, it indicates that the value of the power exponent n and the value of the conversion coefficient C obtained by other methods are reasonable, otherwise they are unreasonable. The present invention has high application value.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and particularly to a method for judging the rationality of a nuclear magnetic resonance power function relationship. Background Art

[0002] Based on the nuclear magnetic resonance phenomenon, nuclear magnetic resonance core experiments measure the nuclear magnetic resonance signals of hydrogen nuclei in fluids (such as oil, gas, and water) in rock pores to obtain key parameters such as porosity, pore size distribution, movable fluid saturation, and permeability of the rock pore structure, and have been widely used in fields such as oil and gas reservoir evaluation, oil and gas field exploration, and development. To convert the transverse relaxation time measured by nuclear magnetic resonance into the nuclear magnetic resonance pore throat radius, existing research has proposed that there is a power function relationship between the transverse relaxation time and the pore throat radius. Only by obtaining the conversion coefficient and the power exponent can the transverse relaxation time distribution be converted into the nuclear magnetic resonance pore throat radius distribution.

[0003] The conversion coefficient and the power exponent jointly determine the accuracy of converting the transverse relaxation time into the pore throat radius; however, there is currently little relevant research in this field. If a method can be constructed to judge the rationality of the conversion coefficient and the power exponent in the nuclear magnetic resonance power function relationship by means of the correlation between the transverse relaxation time distribution and the pore throat radius distribution measured by high-pressure mercury injection, the reliability of the pore structure analysis results can be effectively improved. Summary of the Invention

[0004] The present invention aims at the above problems and proposes a method for judging the rationality of a nuclear magnetic resonance power function relationship.

[0005] The technical solution of the present invention lies in that:

[0006] According to the basic principle of nuclear magnetic resonance, the transverse relaxation process of the fluid in the pore throat is affected by the combined action of three mechanisms: free relaxation, diffusion relaxation, and surface relaxation. Its transverse relaxation time is expressed as:

[0007] 1 / T 2 = 1 / T 2B + 1 / T 2D + 1 / T 2S (1)

[0008] In the formula: T 2 is the transverse relaxation time, with the dimension of ms; T 2B is the transverse free relaxation time, with the dimension of ms; T 2D is the transverse diffusion relaxation time, with the dimension of ms; T 2S is the transverse surface relaxation time, with the dimension of ms.

[0009] When the fluid in the core pore throat is the wetting phase, its transverse free relaxation time T 2B is much greater than the transverse relaxation time T 2, and the 1 / T 2B term in Equation (1) can be neglected; when the magnetic field gradient is small and the echo spacing is short enough, the transverse diffusion relaxation time T 2D is usually long, and the 1 / T 2D term in Equation (1) can be neglected. For nuclear magnetic resonance experiments, the fluid used in the experiment is usually simulated formation water, the magnetic field is weak and the echo spacing is short, so Equation (1) can be approximately written as:

[0010] 1 / T 2≈1 / T 2S = ρ 2 S / V (2)

[0011] In the formula: ρ 2 is the transverse surface relaxation strength, with the dimension of μm / ms;

[0012] S is the surface area of the pore throat, with the dimension of μm 2 ; V is the pore throat volume, with the dimension of μm 3 ;

[0013] Let S / V = F S / r , substitute it into Equation (2), and we get:

[0014] r ≈ ρ 2 F S T 2 (3)

[0015] In the formula: F S is the pore throat shape factor, dimensionless; r is the pore throat radius, with the dimension of μm.

[0016] Since the influence of 1 / T 2B and 1 / T 2D on 1 / T 2 is neglected, so both Equation (2) and Equation (3) are approximate equations. For the convenience of solution, assume the pore throat radiusr The equation relationship with the transverse relaxation time T and 2 is as follows:

[0017] r= ( ρ 2 F S + δ ) T 2 (4)

[0018] In the formula: δ is the correction coefficient of the transverse free relaxation time and the transverse diffusion relaxation time, with the dimension of μm / ms;

[0019] Introduce δ into formula (4) to turn formula (3) into an equation.

[0020] Since ρ 2 F S and δ both have unknown variation laws and are difficult to accurately obtain, resulting in the unknown correlation between the pore throat radius r and the transverse relaxation time T and 2.

[0021] If we let C =( ρ 2 F S + δ ) T 2 1-1 / n , and substitute it into formula (4), we get:

[0022] r = CT 2 1 / n (5)

[0023] In the formula: C is the conversion coefficient, with the dimension of μm / ms, n is the power exponent, dimensionless.

[0024] Regarding the conversion coefficient C of the same core as a constant, formula (5) is then the power function relationship between the pore throat radius r and the transverse relaxation time T and 2.

[0025] It can be seen from formula (5) that the power function relationship contains two unknown parameters, the conversion coefficient C and the power exponent n . Usually, the combination of the transverse relaxation time T and the pore throat radius r is adopted, resulting in various calculation methods. However, the conversion coefficients C and the power exponents nIt remains to be demonstrated whether it is reasonable.

[0026] The pore throat radius measured by high-pressure mercury intrusion experiment r pc distribution cannot represent the complete pore throat radius r distribution. According to nuclear magnetic resonance T 2-converted nuclear magnetic resonance pore throat radius r T2 distribution represents an almost complete pore throat radius r distribution. Therefore, there is the objective fact of "nuclear magnetic resonance pore throat radius r T2 distribution includes high-pressure mercury intrusion pore throat radius r pc distribution".

[0027] According to the objective fact of "nuclear magnetic resonance pore throat radius r T2 distribution includes high-pressure mercury intrusion pore throat radius r pc distribution", the minimum pore throat radius of high-pressure mercury intrusion r pc,min needs to meet two constraint conditions:

[0028] ① The minimum pore throat radius of nuclear magnetic resonance < the minimum pore throat radius of high-pressure mercury intrusion r pc,min ;

[0029] ② The volume proportion of the minimum pore throat radius of high-pressure mercury intrusion γ ( r pc,min ) ≤ the cumulative volume proportion from the minimum transverse relaxation time T 2min to the transverse relaxation time corresponding to the minimum pore throat radius of high-pressure mercury intrusion T 2( r pc,min ).

[0030] Since the measurement results of high-pressure mercury intrusion and nuclear magnetic resonance are both discrete data points, the transverse relaxation time corresponding to the minimum pore throat radius of high-pressure mercury intrusion T 2( r pc,min ) has a lower limit of value:

[0031] T 2( r pc,min ) ≥ T 2min * (6)

[0032] In the formula: r pc,minis the minimum pore throat radius of high-pressure mercury intrusion, with the dimension of μm; T 2( r pc,min ) is the transverse relaxation time corresponding to the minimum pore throat radius of high-pressure mercury intrusion, with the dimension of ms; T 2min * is T 2( r pc,min )'s lower limit of value, that is, the lower limit of the transverse relaxation time corresponding to the minimum pore throat radius of high-pressure mercury intrusion;

[0033] Starting from the minimum transverse relaxation time T 2min , in the direction of increasing transverse relaxation time T 2, there must exist a certain transverse relaxation time that satisfies the constraint condition ② of the minimum pore throat radius of high-pressure mercury intrusion r pc,min . Then the transverse relaxation time at this moment is T 2min * .

[0034] The minimum pore throat radius of high-pressure mercury intrusion r pc,min and its corresponding T 2( r pc,min ) satisfy Equation (5), that is T 2( r pc,min ) = r pc,min n / C n ; Substitute it into Equation (6) and derive the upper limit of the conversion coefficient C :

[0035] C ≤ r pc,min / ( T 2min * ) 1 / n (7).

[0036] Similarly, according to the objective fact that "the nuclear magnetic resonance pore throat radius r T2 distribution contains the high-pressure mercury intrusion pore throat radius r pc distribution", the maximum pore throat radius of high-pressure mercury intrusion r pc,max needs to satisfy 2 constraint conditions:

[0037] ① The maximum pore throat radius of nuclear magnetic resonance ≥ the maximum pore throat radius of high-pressure mercury injection r pc,max ;

[0038] ② From any high-pressure mercury injection pore throat radius r pc to the maximum pore throat radius of high-pressure mercury injection r pc,max the cumulative volume fraction ≤ from any high-pressure mercury injection pore throat radius r pc the corresponding transverse relaxation time to the maximum transverse relaxation time T 2max the cumulative volume fraction.

[0039] Since the measurement results of high-pressure mercury injection and nuclear magnetic resonance are both discrete data points, there is a lower limit for the transverse relaxation time corresponding to the maximum pore throat radius of high-pressure mercury injection:

[0040] T 2( r pc,max ) ≤ T 2max * (8)

[0041] In the formula: r pc,max is the maximum pore throat radius of high-pressure mercury injection, with the dimension of μm; T 2( r pc,max ) is the transverse relaxation time corresponding to the maximum pore throat radius of high-pressure mercury injection, with the dimension of ms; T 2max * is T 2( r pc,max ) the upper limit of the value, that is, the upper limit of the transverse relaxation time corresponding to the maximum pore throat radius of high-pressure mercury injection;

[0042] Starting from the maximum transverse relaxation time T 2max and moving in the direction of decreasing transverse relaxation time T 2, there must be a certain transverse relaxation time that satisfies the constraint condition ② of the maximum pore throat radius of high-pressure mercury injection r pc,max , and the transverse relaxation time at this moment is T 2max * .

[0043] The maximum pore throat radius of high-pressure mercury injection r pc,max and its corresponding T 2( r pc,max) satisfy Equation (5), that is T 2( r pc,max )= r pc,max n / C n ; Substituting it into Equation (8), the lower limit of the conversion coefficient C is derived as follows:

[0044] C ≥ r pc,max / ( T 2max * ) 1 / n (9).

[0045] According to Equation (7) and Equation (9), the value range of the conversion coefficient C is established as:

[0046] r pc,max / ( T 2max * ) 1 / n ≤ C ≤ r pc,min / ( T 2min * ) 1 / n (10).

[0047] In Equation (10), both the upper limit and the lower limit of the conversion coefficient C include the power exponent n , and the power exponent n is an unknown parameter. Therefore, using the parameter interval r pc,max / ( T 2max * ) 1 / n , r pc,min / ( T 2min * ) 1 / n to verify the rationality of the conversion coefficient C obtained by other methods, it is necessary to n value is known. Therefore, it is also necessary to establish a method for judging the rationality of the power exponent n .

[0048] It can be seen from Equation (10) that the power exponent n satisfies the following inequality:

[0049] r pc,max / ( T 2max * ) 1 / n ≤ r pc,min / ( T 2min * ) 1 / n (11)

[0050] Deriving equation (11) can obtain the upper limit of the power exponent n :

[0051] n ≤ ln( T 2max * / T 2min * ) / ln( r pc,max / r pc,min ) (12)

[0052] According to the basic principle of nuclear magnetic resonance, whether using a linear correlation formula or a power function relationship formula, the pore throat radius r and the transverse relaxation time T 2 should satisfy a positive correlation relationship, that is, the pore throat radius r increases as the transverse relaxation time T 2 increases. Equation (5) is a power function relationship formula. Since the pore throat radius r and the transverse relaxation time T 2 need to satisfy a positive correlation relationship, it is required that n > 0. It should be noted that the power function relationship formula also requires the conversion coefficient C > 0, but it can be seen from equation (10) that the conversion coefficient C > 0 necessarily holds.

[0053] According to equation (12) and n > 0 this condition, establish the value range of the power exponent n of the power function relationship formula:

[0054] 0 < n ≤ ln ( T 2max * / T 2min * ) / ln ( r pc,max / r pc,min ) (13)

[0055] It can be seen from formula (13) that the power exponent n has a value range of (0, ln( T 2max * / T 2min * ) / ln( r pc,max / r pc,min ))], which is a semi-open and semi-closed interval and can be used to verify the rationality of the power exponent n value obtained by other methods.

[0056] By combining formula (10) and formula (13) and respectively evaluating the conversion coefficient C and the power exponent n , the rationality of the power function relationship obtained by other methods can be judged: if the conversion coefficient C value obtained by other methods satisfies formula (10), and at the same time the power exponent n value satisfies formula (13), it indicates that the power function relationship obtained by other methods is reasonable; otherwise, it is unreasonable.

[0057] The technical effect of the present invention is as follows:

[0058] Based on the power function relationship between the transverse relaxation time T 2 and the pore throat radius r , by using the minimum pore throat radius of high-pressure mercury injection and its corresponding transverse relaxation time, as well as the maximum pore throat radius of high-pressure mercury injection and its corresponding transverse relaxation time, the value ranges of the conversion coefficient C and the power exponent n are respectively constructed, which can be used to judge the rationality of the power function relationship obtained by other methods and has high application value. Description of the Drawings

[0059] Figure 1 is the cumulative volume fraction distribution curve of the pore throat radius of high-pressure mercury injection.

[0060] Figure 2 is the cumulative volume fraction distribution curve of the transverse relaxation time.

[0061] Figure 3 is T 2max M = 816.26 ms, the cumulative volume fraction distribution curve of the nuclear magnetic resonance pore throat radius.

[0062] Figure 4 is Figure 1 and Figure 3 comparison chart.

[0063] Figure 5 For T 2max M = 29.72 ms, the cumulative volume fraction distribution curve of the nuclear magnetic resonance pore throat radius.

[0064] Figure 6 For Figure 1 and Figure 5 Comparison chart. Specific implementation manner

[0065] A method for judging the rationality of a nuclear magnetic resonance power function relationship, the method is as follows:

[0066] Step 1: Obtain the distribution data of the high-pressure mercury injection pore throat radius through high-pressure mercury injection experiments, and then obtain the minimum pore throat radius of high-pressure mercury injection r pc , the maximum pore throat radius of high-pressure mercury injection r pc,min , and the volume fraction of the minimum pore throat radius of high-pressure mercury injection r pc,max ( γ ( r pc,min ));

[0067] Step 2: Obtain the distribution data of the transverse relaxation time T 2 through nuclear magnetic resonance experiments, and then obtain the maximum transverse relaxation time T 2max and the minimum transverse relaxation time T 2min ;

[0068] Step 3: Obtain the upper limit of the transverse relaxation time corresponding to the maximum pore throat radius of high-pressure mercury injection T 2max * and the lower limit of the transverse relaxation time corresponding to the minimum pore throat radius of high-pressure mercury injection T 2min * ; The specific process is as follows:

[0069] (1) Define the first intermediate parameter T 2max M and the second intermediate parameter T 2min M ;

[0070] (2) Starting with T 2max M = T 2max and using rT2 =( r pc,max / T 2max M )× T 2 Convert nuclear magnetic resonance T 2 to r T2 ; Construct the first judgment condition: r T2 Whether the cumulative volume fraction distribution curve of r pc is entirely to the right of the cumulative volume fraction distribution curve of T 2max M ; If the first judgment condition is satisfied, then use the current T 2max * as T 2max M ; Otherwise, decrease the

[0071] (3)Starting from T 2min M = T 2min begin, if the second judgment conditions of " r pc,max / T 2max * ≤ r pc,min / T 2min M ” and “ γ ( r pc,min )≤ Cumulative volume fraction from T 2min to T 2min M are satisfied, then use the current T 2min M as T 2min * ; Otherwise, increase the T 2min M value and start over until the second judgment condition is satisfied;

[0072] Step 4: Construct the value range of the power exponent n is (0, ln( T 2max* / T 2min * ) / ln( r pc,max / r pc,min )] and the conversion coefficient C value range r pc,max / ( T 2max * ) 1 / n , r pc,min / ( T 2min * ) 1 / n ;

[0073] Step 5: If the power exponent n and the conversion coefficient C obtained by other methods both fall within the above value range, it indicates that the value of the power exponent n and the conversion coefficient C obtained by other methods is reasonable; otherwise, it is unreasonable.

[0074] Specific application case

[0075] A method for judging the rationality of a nuclear magnetic resonance power function relationship is as follows:

[0076] The distribution data of the high-pressure mercury intrusion pore throat radius r pc measured by high-pressure mercury intrusion experiment is shown in Table 1; the distribution data of the transverse relaxation time T 2 measured by nuclear magnetic resonance experiment is shown in Table 2;

[0077] Table 1 Distribution data of high-pressure mercury intrusion pore throat radius r pc distribution data

[0078] ;

[0079] Table 2 Distribution data of transverse relaxation time T 2

[0080] .

[0081] Step 1: According to the data in Table 1, obtain the maximum high-pressure mercury intrusion pore throat radius r pc,max = 0.1508 μm, the minimum high-pressure mercury intrusion pore throat radius r pc,min= 0.0036 μm; volume percentage of the minimum pore throat radius in high-pressure mercury intrusion γ ( r pc,min ) = 0.24%; plot the cumulative volume percentage distribution curve of the pore throat radius in high-pressure mercury intrusion ( Figure 1 ).

[0082] Step 2: Obtain the maximum transverse relaxation time T 2max = 816.26 ms and the minimum transverse relaxation time T 2min = 0.04 ms according to the data in Table 2; plot the cumulative volume percentage distribution curve of the transverse relaxation time ( Figure 2 ).

[0083] Step 3: Obtain the upper limit of the transverse relaxation time corresponding to the maximum pore throat radius in high-pressure mercury intrusion T 2max * and the lower limit of the transverse relaxation time corresponding to the minimum pore throat radius in high-pressure mercury intrusion T 2min * ; the specific process is as follows:

[0084] (1) Define the first intermediate parameter T 2max M and the second intermediate parameter T 2min M ;

[0085] (2) Starting with T 2max M = T 2max = 816.26 ms, use r T2 = ( r pc,max / T 2max M ) × T 2 = 0.000184745 × T 2 to convert the nuclear magnetic resonance T 2 to the nuclear magnetic resonance pore throat radius r T2 ; the conversion results are shown in Table 3;

[0086] Table 3 T 2max M When r T2 the data of the nuclear magnetic resonance pore throat radius

[0087] ;

[0088] According to the data in Table 3, plot the cumulative volume fraction distribution curve of the nuclear magnetic resonance pore throat radius when T 2max M = 816.26 ms ( Figure 3 ); Let the pore throat radius r = nuclear magnetic resonance pore throat radius r T2 , and the pore throat radius r = mercury intrusion pore throat radius r pc , and plot Figure 1 and Figure 3 on the same graph ( Figure 4 ) for comparison; T 2max M = T 2max = 816.26 ms, the cumulative volume fraction distribution curve of r T2 is not entirely to the right of the cumulative volume fraction distribution curve of r pc , so the first judgment condition is not met; therefore, reduce the T 2max M value;

[0089] until T 2max M = 29.72 ms, use r T2 = ( r pc,max / T 2max M ) × T 2 = 0.005074024 × T 2 to convert the nuclear magnetic resonance T 2 to the nuclear magnetic resonance pore throat radius r T2 , and the conversion results are shown in Table 4;

[0090] Table 4 T 2max M = 29.72 ms, the data of the nuclear magnetic resonance pore throat radius r T2

[0091]

[0092] According to the data in Table 4, plot the cumulative volume fraction distribution curve of the nuclear magnetic resonance pore throat radius when T 2max M = 29.72 ms ( Figure 5 ); Let the pore throat radius r = the nuclear magnetic resonance pore throat radius r T2 , and the pore throat radius r = the mercury injection pore throat radius r pc , and plot Figure 1 and Figure 5 on the same graph ( Figure 6 ) for comparison; When T 2max M = 29.72 ms, r T2 's cumulative volume fraction distribution curve is entirely on the right side of r pc 's cumulative volume fraction distribution curve, then the first judgment condition is satisfied; Then T 2max * = T 2max M = 29.72 ms;

[0093] (3) Starting from T 2min M = T 2min = 0.04 ms, according to the data in Table 2, from T 2min to T 2min M 's cumulative volume fraction = 0.006% (the volume fraction when the transverse relaxation time T 2 is 0.04 ms), judge the second judgment condition, and the result shows that:

[0094] r pc,max / T 2max * = 0.005074024 μm / ms, r pc,min / T 2min M = 0.09 μm / ms, satisfying " r pc,max / T 2max * ≤r pc,min / T 2min M ”;

[0095] γ ( r pc,min ) = 0.24%, from T 2min to T 2min M the cumulative volume fraction = 0.006%, not meeting “ γ ( r pc,min ) ≤ the cumulative volume fraction from T 2min to T 2min M ”; then the second judgment condition is not met; thus increase T 2min M the value;

[0096] until when T 2min M = 0.12 ms, r pc,min / T 2min M = 0.03 μm / ms, meeting “ r pc,max / T 2max * ≤ r pc,min / T 2min M ”;

[0097] γ ( r pc,min ) = 0.24%, from T 2min to T 2min M the cumulative volume fraction = 0.344%, meeting “ γ ( r pc,min ) ≤ the cumulative volume fraction from T 2min to T 2min M ”; then the second judgment condition is met; thus T2min * = T 2min M = 0.12 ms.

[0098] Step 4: Establish the power exponent n and the conversion coefficient C value range; the specific process is as follows:

[0099] ln( T 2max * / T 2min * ) / ln( r pc,max / r pc,min ) = 1.48, so the value range of the power exponent n is (0, 1.48];

[0100] r pc,max / ( T 2max * ) 1 / n = 0.1508 / (29.72) 1 / n , r pc,min / ( T 2min * ) 1 / n = 0.0036 / (0.12) 1 / n , so the value range of the conversion coefficient C is [0.1508 / (29.72) 1 / n , 0.0036 / (0.12) 1 / n .

[0101] Step 5: If the power exponent n obtained by other methods is within (0, 1.48] and the conversion coefficient C is within [0.1508 / (29.72) 1 / n , 0.0036 / (0.12) 1 / n , it indicates that the values of the power exponent n and the conversion coefficient C obtained by this method are reasonable; otherwise, they are unreasonable.

Claims

1. A method for judging the rationality of a nuclear magnetic resonance power function relationship, characterized in that: The nuclear magnetic resonance power function relationship is specifically a power function relationship between the transverse relaxation time and the pore throat radius, and the method is as follows: Build n The value range of (0, ln( T 2max * / T 2min * ) / ln( r pc,max / r pc,min )]; Build C The value range of [ r pc,max / ( T 2max * ) 1 / n , r pc,min / ( T 2min * ) 1 / n ]; If obtained by other means n Value and C If the values ​​fall within the above range, it means that the n Value and C The value is reasonable, otherwise it is unreasonable; in, T 2max * and T 2min * The specific process of obtaining is: (1) Definition T 2max M and T 2min M ; (2) T 2max M = T 2max Start using r T2 =( r pc,max / T 2max M )× T 2 Nuclear Magnetic Resonance T 2Convert to r T2 ; Construct the first judgment condition: r T2 Are all the cumulative volume share distribution curves located in r pc The right side of the cumulative volume proportion distribution curve; if the first judgment condition is met, the current T 2max M As T 2max * Otherwise, reduce T 2max M The value taking starts again until the first judgment condition is met; (3) T 2min M = T 2min Start by building the second judgment condition: r pc,max / T 2max * ≤ r pc,min / T 2min M "and" γ ( r pc,min )≤From T 2min arrive T 2min M If the second judgment condition is met, the current T 2min M As T 2min * Otherwise, increase T 2min M The value taking starts again until the second judgment condition is met; in, C is the conversion coefficient, the dimension is μm / ms; n is the power exponent, dimensionless; r pc,max is the maximum pore throat radius of high-pressure mercury injection, with the dimension of μm; r pc,min is the minimum pore throat radius of high-pressure mercury injection, with the dimension of μm; T 2max * for r pc,max The corresponding upper limit of the transverse relaxation time is in ms; T 2min * for r pc,min The corresponding lower limit of transverse relaxation time is in ms; T 2max M is the first intermediate parameter, with the dimension of ms; T 2min M is the second intermediate parameter, with the dimension of ms; T 2 is the transverse relaxation time, with the dimension of ms; T 2max is the maximum transverse relaxation time, with the dimension of ms; T 2min is the minimum transverse relaxation time, with the dimension of ms; r T2 is the NMR pore throat radius, dimension is μm; r pc is the high-pressure mercury injection pore throat radius, with the dimension of μm; γ ( r pc,min )for r pc,min The volume percentage of , dimensionless.

2. The method for judging the rationality of the nuclear magnetic resonance power function relationship according to claim 1, characterized in that: Said r pc , r pc,max , r pc,min and γ ( r pc,min ) were obtained through high-pressure mercury injection experiments.

3. The method for judging the rationality of the nuclear magnetic resonance power function relationship according to claim 1, characterized in that: Said T 2max and T 2min All were obtained through nuclear magnetic resonance experiments.

4. The method for judging the rationality of the nuclear magnetic resonance power function relationship according to claim 1, characterized in that: Also includes reducing T 2max M When taking the value, the transverse relaxation time measured by NMR experiment is T 2 The distribution data of is correspondingly reduced; Increase T 2min M When taking the value, the transverse relaxation time measured by NMR experiment is T 2 The distribution data increases accordingly.

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