A method for converting the transverse relaxation time distribution into the capillary pressure distribution

Abstract

The present invention relates to the technical field of oil and gas field development, and specifically relates to a method for converting the transverse relaxation time distribution into the capillary pressure distribution. The present invention proposes a correction coefficient for converting the high-pressure mercury intrusion pore throat radius into the transverse relaxation time, and then obtains the conversion coefficient by using linear interpolation and volume ratio weighting, and establishes a method for converting the transverse relaxation time distribution into the capillary pressure distribution, providing a technical reference for studying the microscopic structure and properties of reservoirs.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and particularly to a method for converting the transverse relaxation time distribution into the capillary pressure distribution. Background Art

[0002] The capillary pressure distribution is an important means for studying the microscopic characteristics of reservoirs, and a complete capillary pressure distribution has important value. High-pressure mercury injection is the most direct means to obtain the capillary pressure distribution. However, due to the complexity of the microscopic pore throat structure and the limitation of the highest mercury injection pressure in high-pressure mercury injection, the capillary pressure distribution of all pore throats in the core cannot be measured by high-pressure mercury injection. Nuclear magnetic resonance does not directly measure the capillary pressure distribution, but its measurement results represent the transverse relaxation time distribution of all pore throats in the core. There is a linear correlation between the transverse relaxation time and the pore throat radius, and there is a capillary pressure equation between the pore throat radius and the capillary pressure. Therefore, the transverse relaxation time can be converted into the capillary pressure, and the key lies in obtaining the conversion coefficient.

[0003] When high-pressure mercury injection and nuclear magnetic resonance technology are used in combination, if the correction coefficient for converting the pore throat radius of high-pressure mercury injection into the corresponding transverse relaxation time can be determined, all the transverse relaxation times corresponding to all pore throat radii can be found. Subsequently, the conversion coefficient can be obtained by volume weighting, and then the nuclear magnetic resonance capillary pressure distribution can be obtained, which has an important role in studying the capillary pressure characteristics of all pore throats in the core. Summary of the Invention

[0004] The present invention aims at the above problems and proposes a method for converting the transverse relaxation time distribution into the capillary pressure distribution.

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

[0006] According to the basic principle of nuclear magnetic resonance, the transverse relaxation process of fluid in the pore throat is affected by 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, ms; T 2B is the transverse free relaxation time, ms; T 2D is the transverse diffusion relaxation time, ms; T2S is the transverse surface relaxation time, in ms.

[0009] When the fluid in the pore throat is the wetting phase, its transverse free relaxation time T 2B is much greater than the transverse relaxation time T 2 , the 1 / T 2B term in Equation (1) can be ignored; 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 ignored. 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] Where: ρ 2 is the transverse surface relaxation intensity, in μm / ms; S is the surface area of the pore throat, in μm 2 ; V is the volume of the pore throat, in μm 3 ;

[0012] Let S / V = F S / r , substituting into Equation (2), we get:

[0013] r ≈ ρ 2 F S T 2 (3)

[0014] Where: F S is the pore throat shape factor, dimensionless; r is the pore throat radius, in μm.

[0015] Since the 1 / T 2B and 1 / T 2DEffect on 1 / T 2 , so both Equation (2) and Equation (3) are approximate equations. For the convenience of solving, assume that the pore throat radius r and the transverse relaxation time T 2 The equation relationship between them is:

[0016] r= ( ρ 2 F S + δ ) T 2 (4)

[0017] In the formula: δ is the correction coefficient of the transverse free relaxation time and the transverse diffusion relaxation time, μm / ms;

[0018] Introduce δ in Equation (4) to make Equation (3) an equation.

[0019] Since ρ 2 F S and δ The variation laws of both are unknown and difficult to accurately obtain, resulting in the pore throat radius r and the transverse relaxation time T 2 The correlation between them is unknown.

[0020] If C = ρ 2 F S + δ , substitute it into Equation (4) to get the linear correlation formula between the transverse relaxation time T 2 and the pore throat radius C :

[0021] T 2 = r / C (5)

[0022] In the formula: C is the conversion coefficient, μm / ms.

[0023] (5) Equation is the linear correlation formula between the pore throat radius r and the transverse relaxation time T 2 .

[0024] At the same time, the pore throat radiusr Satisfy the capillary force equation:

[0025] r =2 σ cos θ / p c (6)

[0026] In the formula: σ is the interfacial tension of mercury, N / m; θ is the wetting contact angle of mercury, °; p c is the capillary force, MPa.

[0027] Substitute (5) into equation (6) to obtain the conversion relationship between the capillary force and the transverse relaxation time T 2 :

[0028] p c =2 σ cos θ / ( CT 2 ) (7)

[0029] The capillary force can be used to study the microscopic structure and properties of the reservoir, providing important basic theoretical support for oil and gas exploration and development. The high-pressure mercury injection experiment is the most direct means to obtain the capillary force. However, due to the limitation of the maximum mercury injection pressure, the capillary force curve obtained by high-pressure mercury injection cannot fully reflect the capillary force distribution of all pore throats. At the same time, because the experimental measurement data points of high-pressure mercury injection are few, it further leads to a relatively rough capillary force distribution reflected by the capillary force curve obtained by high-pressure mercury injection.

[0030] The nuclear magnetic resonance saturated water core experiment can measure the transverse relaxation time distribution of almost all pore throats. When the nuclear magnetic resonance saturated water core experiment and the high-pressure mercury injection experiment are combined to obtain 2 σ cos θ / C, the transverse relaxation time distribution of nuclear magnetic resonance can be converted into the capillary force distribution of nuclear magnetic resonance through equation (7). Since the transverse relaxation time of nuclear magnetic resonance is the transverse relaxation time of all pore throats, the capillary force distribution of nuclear magnetic resonance also represents the capillary force distribution of all pore throats.

[0031] Since the fluid used in the high-pressure mercury injection experiment is mercury, for mercury, σ =0.48 N / m, θ =140°, so 2 σ cos θ =0.735. Substitute it into equation (7) to get:

[0032] p c=0.735 / ( CT 2 ) (8)

[0033] It can be seen from Equation (8) that the main purpose of jointly conducting the core experiment of nuclear magnetic resonance saturated water and the high-pressure mercury injection experiment is to obtain the conversion coefficient C . Since the core experiment of nuclear magnetic resonance saturated water measures all pore throats, while the high-pressure mercury injection experiment only measures some pore throats, there is an objective fact that "the pore throat distribution of nuclear magnetic resonance contains the pore throat distribution of high-pressure mercury injection".

[0034] Since it involves the mutual conversion between nuclear magnetic resonance and high-pressure mercury injection, for the sake of distinction, let:

[0035] (1)The pore throat radius is r , the high-pressure mercury injection pore throat radius is r (pc) , and the nuclear magnetic resonance pore throat radius is r ( T 2 );

[0036] (2)The transverse relaxation time is T 2 , the nuclear magnetic resonance transverse relaxation time is T 2 (NMR) , the transverse relaxation time corresponding to the capillary force of high-pressure mercury injection is T 2 ( p c (HPMI) )、the transverse relaxation time corresponding to the high-pressure mercury injection pore throat radius is T 2 ( r (pc) );

[0037] (3)The capillary force is p c , the high-pressure mercury injection capillary force is p c (HPMI) , and the nuclear magnetic resonance capillary force is p c ( T 2 )。

[0038] The distribution curve of the nuclear magnetic resonance transverse relaxation time T 2 (NMR) measured by the core experiment of nuclear magnetic resonance saturated water ( T 2 (NMR) curve) is the nuclear magnetic resonance transverse relaxation time T 2(NMR) The distribution of cumulative volume percentage, and the mercury intrusion capillary pressure curve measured by high-pressure mercury intrusion experiment ( p c (HPMI) curve) is the mercury intrusion capillary pressure p c (HPMI) and the distribution of cumulative mercury intrusion saturation, and the cumulative mercury intrusion saturation is the cumulative volume percentage.

[0039] If the conversion coefficient C is known, substituting the mercury intrusion capillary pressure p c (HPMI) into Equation (8) gives T 2 ( p c (HPMI) ) = 0.735× T 2max M / ( r max (pc) × p c (HPMI) ), and thus the mercury intrusion capillary pressure p c (HPMI) can be converted into the transverse relaxation time corresponding to the mercury intrusion capillary pressure T 2 ( p c (HPMI) ). Taking the cumulative volume percentage as the abscissa and the transverse relaxation time as the ordinate, plotting the nuclear magnetic resonance transverse relaxation time T 2 (NMR) and the transverse relaxation time corresponding to the mercury intrusion capillary pressure T 2 ( p c (HPMI) ) on the same graph, due to the need to satisfy the objective fact that "the nuclear magnetic resonance pore throat distribution contains the high-pressure mercury intrusion pore throat distribution", there is a phenomenon: for any same transverse relaxation time T 2 , the cumulative volume percentage of the nuclear magnetic resonance transverse relaxation time T 2 (NMR) > the cumulative volume percentage of the transverse relaxation time corresponding to the mercury intrusion capillary pressure T 2 ( p c (HPMI) ).

[0040] As can be seen from Equation (5), when obtaining the conversion coefficient by combining the core experiment of nuclear magnetic resonance saturated water and the high-pressure mercury injection experiment, it is only necessary to find the transverse relaxation time corresponding to the pore throat radius of the high-pressure mercury injection C ; according to the different selected pore throat radii of the high-pressure mercury injection and their corresponding transverse relaxation times, methods such as the double eigenvalue method, the maximum eigenvalue method, and the cumulative saturation method are formed. Among them, the double eigenvalue method uses two pore throat radii of the high-pressure mercury injection, the maximum eigenvalue method uses one pore throat radius of the high-pressure mercury injection, and the cumulative saturation method uses all pore throat radii of the high-pressure mercury injection. Since the purpose of the present invention is to obtain the nuclear magnetic resonance capillary force T 2 ( r (pc) ) distribution, and the cumulative saturation method utilizes the high-pressure mercury injection capillary force p c ( T 2 ) distribution, it is more reasonable to use the cumulative saturation method to obtain the conversion coefficient p c (HPMI) . However, the conventional cumulative saturation method does not consider the rationality of the conversion result, resulting in the conversion result may be contradictory to the objective fact that "the nuclear magnetic resonance pore throat distribution contains the high-pressure mercury injection pore throat distribution". Therefore, it is necessary to correct the conventional cumulative saturation method. C The corrected cumulative saturation method is as follows:

[0041] Use

[0042] to represent the correction coefficient, which is used to convert the pore throat radius ω of the high-pressure mercury injection into the transverse relaxation time r (pc) corresponding to the pore throat radius of the high-pressure mercury injection T 2 ( r (pc) ); use T 2max M to represent the intermediate parameter in the correction process;

[0043] (2) Starting from T 2max M = T 2max , adopt T 2 ( p c (HPMI) ) = 0.735 × T 2max M / ( r max(pc) × p c (HPMI) ) Convert the high-pressure mercury injection capillary pressure p c (HPMI) into the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) ), with the cumulative volume fraction as the abscissa and the transverse relaxation time T 2 as the ordinate, plot the nuclear magnetic resonance transverse relaxation time T 2 (NMR) and the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) ) on the same graph, and determine whether it satisfies "for any same transverse relaxation time, the cumulative volume fraction of the nuclear magnetic resonance transverse relaxation time T 2 (NMR) > the cumulative volume fraction of the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) )". If it is satisfied, take the cumulative volume fraction from T 2max to T 2max M as ω ;

[0044] If not, gradually decrease the T 2max M value, and use T 2 ( p c (HPMI) ) = 0.735× T 2max M / ( r max (pc) × p c (HPMI) ) to convert the high-pressure mercury injection capillary pressure p c (HPMI) into the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T2 ( p c (HPMI) ), with the cumulative volume fraction as the abscissa and the transverse relaxation time T 2 as the ordinate, plot the nuclear magnetic resonance transverse relaxation time T 2 (NMR) and the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) ) on the same graph and determine whether it satisfies "for any same transverse relaxation time, the cumulative volume fraction of the nuclear magnetic resonance transverse relaxation time T 2 (NMR) > the cumulative volume fraction of the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) )". If it is satisfied, take the cumulative volume fraction from T 2max to T 2max M as ω ;

[0045] (3) Calculate the transverse relaxation time corresponding to the high-pressure mercury injection pore throat radius T 2 ( r (pc) ) by linear interpolation. The linear interpolation formula is:

[0046] (9)

[0047] In the formula: ω is the correction coefficient, dimensionless;

[0048] T 2 ( r (pc) ) is the transverse relaxation time corresponding to the high-pressure mercury injection pore throat radius, ms;

[0049] r (pc) is the high-pressure mercury injection pore throat radius, um; γ ( r (pc) ) is r (pc) the corresponding volume fraction, dimensionless;

[0050] T 2 (0) is the first intermediate parameter, ms; γ ( T 2 (0) ) is T 2 (0) the corresponding volume fraction, dimensionless;

[0051] T 2 (1) is the second intermediate parameter, ms; T 2 (1) < T 2 (0) ≤ T 2max and is adjacent to T 2 (0) ;

[0052] γ ( T 2 (1) ) is T 2 (1) the corresponding volume fraction, dimensionless;

[0053] r max (pc) is the maximum pore throat radius of high-pressure mercury intrusion, um;

[0054] γ ( r max (pc) ) is r max (pc) the corresponding volume fraction, dimensionless;

[0055] γ pc is the intermediate variable for calculating , dimensionless;

[0056] is γ ( r (pc) ) to γ ( r max (pc) ) cumulative volume fraction, dimensionless;

[0057] γ ( T2max ) is T 2max the corresponding volume fraction, dimensionless;

[0058] T 2max the maximum transverse relaxation time of nuclear magnetic resonance, ms;

[0059] is γ ( T 2 (0) ) to γ ( T 2max ) the cumulative volume fraction, dimensionless;

[0060] γ T2 is the intermediate variable for calculating , dimensionless;

[0061] The specific calculation steps are as follows:

[0062] ① Let r (pc) = r max (pc) ;

[0063] ② Calculate the cumulative volume fraction γ ( r (pc) ) from γ ( r max (pc) ) to ;

[0064] ③ Let T 2 (0) = T 2max ;

[0065] ④ According to T 2 (0) obtain T 2 (1) , T 2 (1) less than T 2 (0) and adjacent to T 2 (0) ; Calculate γ ( T 2(0) ) and γ ( T 2 (1) );

[0066] ⑤ Calculate , and determine whether it satisfies . If not satisfied, go to step ⑥; if satisfied, go to step ⑦;

[0067] ⑥ Gradually decrease T 2 (0) the value, and return to step ④;

[0068] ⑦ Calculate and obtain r (pc) the corresponding T 2 ( r (pc) );

[0069] ⑧ Gradually decrease r (pc) the value, and return to step ② until the calculated r (pc) = r min (pc) when T 2 ( r (pc) ), and the calculation ends.

[0070] Through the above steps, the transverse relaxation time corresponding to all high-pressure mercury injection pore throat radii is calculated T 2 ( r (pc) ).

[0071] (4) Calculate the conversion coefficient by weighting method C :

[0072] (10).

[0073] The technical effect of the present invention is as follows:

[0074] The present invention proposes a correction coefficient for converting the high-pressure mercury injection pore throat radius into the transverse relaxation time, and then obtains the conversion coefficient by using linear interpolation and volume ratio weighting, and establishes a method for converting the transverse relaxation time distribution into the capillary pressure distribution, providing a technical reference for studying the microscopic structure and properties of the reservoir. Description of the Drawings

[0075] Figure 1 For T2max M = 816.256 ms, the transverse relaxation time of nuclear magnetic resonance and the transverse relaxation time corresponding to the capillary pressure of high-pressure mercury injection.

[0076] Figure 2 is T 2max M = 117.053 ms, the transverse relaxation time of nuclear magnetic resonance and the transverse relaxation time corresponding to the capillary pressure of high-pressure mercury injection.

[0077] Figure 3 is the capillary pressure of high-pressure mercury injection and the capillary pressure of nuclear magnetic resonance. Specific implementation method

[0078] A method for converting the transverse relaxation time distribution into the capillary pressure distribution is as follows:

[0079] Step 1: Obtain the correction coefficient ω ;

[0080] Step 1.1: According to the results of the high-pressure mercury injection experiment, obtain the high-pressure mercury injection pore throat radius r (pc) distribution data, read the maximum pore throat radius of high-pressure mercury injection r max (pc) and the minimum pore throat radius of high-pressure mercury injection r min (pc) ; According to the results of the nuclear magnetic resonance experiment, obtain the nuclear magnetic resonance transverse relaxation time T 2 (NMR) distribution data, read the maximum nuclear magnetic resonance transverse relaxation time T 2max ;

[0081] Step 1.2: Define an intermediate parameter T 2max M ; Let T 2max M = T 2max ;

[0082] Step 1.3: Use T 2 ( p c (HPMI) ) = 0.735 × T 2max M / ( r max (pc) ×p c (HPMI) ) to convert the high-pressure mercury injection capillary pressure p c (HPMI) into the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) );

[0083] Step 1.4: With the cumulative volume ratio as the abscissa and the transverse relaxation time as the ordinate, plot the nuclear magnetic resonance transverse relaxation time T 2 (NMR) and the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) ) on one graph;

[0084] Step 1.5: Construct the first judgment condition: For any same transverse relaxation time, the cumulative volume ratio of the nuclear magnetic resonance transverse relaxation time T 2 (NMR) > the cumulative volume ratio of the transverse relaxation time corresponding to the high-pressure mercury injection capillary pressure T 2 ( p c (HPMI) );

[0085] Perform the condition of the first judgment condition. If it is satisfied, take the cumulative volume ratio from T 2max to T 2max M as the correction coefficient ω ; if not satisfied, gradually decrease the T 2max M value, repeat Steps 1.3 to 1.5, and obtain the T 2max M value that satisfies the first judgment condition. Take the cumulative volume ratio from T 2max to T 2max M as the correction coefficient ω .

[0086] Step 2: Calculate the transverse relaxation time corresponding to the high-pressure mercury injection pore throat radius through linear interpolation T2 ( r (pc) );

[0087] Step 2.1: Let r (pc) = r max (pc) ; Calculate the cumulative volume ratio from γ ( r (pc) ) to γ ( r max (pc) ) as ;

[0088] Step 2.2: Let T 2 (0) = T 2max , T 2 (1) less than T 2 (0) and adjacent to T 2 (0) , obtain γ ( T 2 (0) ) and γ ( T 2 (1) ); Calculate ;

[0089] Step 2.3: Construct the second judgment condition: ;

[0090] Make a judgment on the second judgment condition. If it is satisfied, substitute the current that satisfies the second judgment condition into Equation (9) to calculate and obtain r (pc) corresponding T 2 ( r (pc) );

[0091] If it is not satisfied, decrease the T 2 (0) value and make a new judgment on the second judgment condition until the that satisfies the second judgment condition is obtained, and then substitute it back into Equation (9) to calculate and obtain r (pc) corresponding T2 ( r (pc) );

[0092] Step 2.4: Gradually reduce the r (pc) value, and return to Step 2.2 to recalculate until r (pc) = r min (pc) at T 2 ( r (pc) ).

[0093] Step 3: Calculate the conversion coefficient through Equation (10) C .

[0094] Step 4: According to the nuclear magnetic resonance experiment results, substitute the nuclear magnetic resonance transverse relaxation time T 2 (NMR) into Equation (8) to obtain p c ( T 2 ) = 0.735 / ( CT 2 (NMR) ), and then obtain the nuclear magnetic resonance capillary force p c ( T 2 ).

[0095] Specific application cases

[0096] A method for converting the transverse relaxation time distribution into the capillary force distribution is as follows:

[0097] Step 1: Obtain the correction coefficient ω ;

[0098] Step 1.1: According to the high-pressure mercury injection experiment results (Table 1), obtain the high-pressure mercury injection pore throat radius r (pc) distribution data, and read the maximum pore throat radius of high-pressure mercury injection r max (pc) = 0.6828 μm, and the minimum pore throat radius of high-pressure mercury injection r min (pc) = 0.0036 μm; according to the nuclear magnetic resonance experiment results (Table 2), obtain the nuclear magnetic resonance transverse relaxation time T 2 (NMR)Distribution data, read the maximum transverse relaxation time of nuclear magnetic resonance T 2max = 816.256 ms;

[0099] Table 1 Results of high-pressure mercury intrusion experiment

[0100] ;

[0101] Table 2 Results of nuclear magnetic resonance experiment

[0102] ;

[0103] Step 1.2: Define an intermediate parameter T 2max M ; Let T 2max M = T 2max = 816.256 ms;

[0104] Step 1.3: Use T 2 ( p c (HPMI) ) = 0.735 × T 2max M / ( r max (pc) × p c (HPMI) ) to convert the high-pressure mercury intrusion capillary force p c (HPMI) into the transverse relaxation time corresponding to the high-pressure mercury intrusion capillary force T 2 ( p c (HPMI) ), as shown in Table 3;

[0105] Table 3 T 2max M = 816.256 ms, the transverse relaxation time corresponding to the high-pressure mercury intrusion capillary force T 2 ( p c (HPMI) )

[0106] ;

[0107] Step 1.4: According to the data in Table 3, with the cumulative volume percentage as the abscissa and the transverse relaxation time as the ordinate, plot the nuclear magnetic resonance transverse relaxation time T 2 (NMR) and the high-pressure mercury intrusion transverse relaxation time T 2 ( p c (HPMI) ) on the same graph, as shown in Figure 1 ;

[0108] Step 1.5: Construct the first judgment condition: For any same transverse relaxation time, the cumulative volume percentage of the nuclear magnetic resonance transverse relaxation time T 2 (NMR) > the cumulative volume percentage of the transverse relaxation time corresponding to the high-pressure mercury intrusion capillary force T 2 ( p c (HPMI) );

[0109] According to Figure 1 it can be seen that the first judgment condition is not satisfied; therefore, reduce the T 2max M value and repeat the calculation;

[0110] until T 2max M = 117.053 ms, and adopt T 2 ( p c (HPMI) ) = 0.735 × T 2max M / ( r max (pc) × p c (HPMI) ), and convert the high-pressure mercury intrusion capillary force p c (HPMI) to the transverse relaxation time corresponding to the high-pressure mercury intrusion capillary force T 2 ( p c (HPMI) ), as shown in Table 4;

[0111] Table 4 T 2max M= 117.053 ms, the transverse relaxation time corresponding to the high-pressure mercury injection capillary force T 2 ( p c (HPMI) )

[0112] ;

[0113] According to the data in Table 4, with the cumulative volume ratio as the abscissa and the transverse relaxation time as the ordinate, the nuclear magnetic resonance transverse relaxation time T 2 (NMR) and the transverse relaxation time corresponding to the high-pressure mercury injection capillary force T 2 ( p c (HPMI) ) are plotted on one graph, see Figure 2 ;

[0114] According to Figure 2 it can be seen that the first judgment condition is satisfied;

[0115] Obtained from Table 2, then from T 2max = 816.256 ms to T 2max M = 117.053 ms, the cumulative volume ratio is 10.757%, so the correction coefficient ω = 10.757%.

[0116] Step 2: Calculate the high-pressure mercury injection pore throat radius through linear interpolation r (pc) The corresponding transverse relaxation time T 2 ( r (pc) )

[0117] Step 2.1: Let r (pc) = r max (pc) = 0.6828 μm, obtained from Table 1, = 0.85%;

[0118] Step 2.2: Let T 2 (0) = T 2max = 816.256 ms, obtained from Table 2, T 2 (1)= 728.135ms, γ ( T 2 (1) ) = 0.097%, calculate = 0.043%;

[0119] Step 2.3: Construct the second judgment condition:;

[0120] = 0.85% + 10.757% = 11.607%; = 0.043% + 0.097% = 0.140%; Does not meet the second judgment condition;

[0121] Decrease T 2 (0) the value, let T 2 (0) = 728.135ms, according to Table 2, T 2 (1) = 649.528ms; γ ( T 2 (1) ) = 0.162%; Calculate to get = 0.140%; = 0.140% + 0.162% = 0.302%; Still does not meet the second judgment condition;

[0122] Continue to decrease T 2 (0) the value until T 2 (0) = 104.416ms, according to Table 2, T 2 (1) = 93.144 ms;

[0123] γ ( T 2 (1) ) = 0.670%; Calculate to get = 11.483%, = 12.153%; Meets the second judgment condition;

[0124] Then r (pc) = 0.6828μm, T 2 (0)= 104.416ms, T 2 (1) = 93.144 ms, γ ( T 2 (1) )= 0.670%, =11.483%, substitute into Equation (9) to calculate and obtain r (pc) corresponding T 2 ( r (pc) )= 102.229ms;

[0125] Step 2.4: Gradually reduce r (pc) the value of r (pc) = r min (pc) =0.0036μm, the T 2 ( r (pc) ) to obtain the transverse relaxation time corresponding to all high-pressure mercury intrusion pore throat radii T 2 ( r (pc) ), as shown in Table 5;

[0126] Table 5 Transverse relaxation time corresponding to high-pressure mercury intrusion pore throat radius T 2 ( r (pc) )

[0127] .

[0128] Step 3: According to the data in Table 5, calculate the conversion coefficient through Equation (10) C =0.00846μm / ms, the specific calculation process of the conversion coefficient C is shown in Table 6;

[0129] Table 6 Specific calculation process of the conversion coefficient C of

[0130] .

[0131] Step 4: According to the nuclear magnetic resonance experiment results, adopt p c ( T 2 )=0.735 / ( CT2 (NMR) ) to convert the nuclear magnetic resonance transverse relaxation time T 2 (NMR) into nuclear magnetic resonance capillary force p c ( T 2 ). The conversion results are shown in Table 7;

[0132] Table 7 Nuclear magnetic resonance capillary force p c ( T 2 )

[0133] .

Claims

1. A method for converting transverse relaxation time distribution into capillary force distribution, characterized in that: Here’s how: Step 1: Get the correction coefficient; The specific process is: (1-1) Construct the first judgment condition: For any identical T2, T2 (NMR) Cumulative volume share> T2(p c (HPMI) )’s cumulative volume share; (1-2) Define T 2max M ; T 2max M =T 2max Initially, T2(p c (HPMI) )=0.735×T 2max M / (r max (pc) ×p c (HPMI) ), p c (HPMI) Convert to T2(p c (HPMI) ); Performing a judgment on a first judgment condition; If it is satisfied, get T that satisfies the first judgment condition 2max M , then T 2max to T 2max M The cumulative volume proportion of is taken as the correction coefficient ω; If not satisfied, reduce T 2max M Take the value, re-judge the first judgment condition, and finally get T that meets the first judgment condition 2max M , with T 2max to T 2max M The cumulative volume proportion of is taken as the correction coefficient ω; Step 2: Calculate T2(r by linear interpolation (pc) ); The specific process is: (2-1) Let r (pc) =r max (pc) ;calculate ; (2-2) Let T2 (0) =T 2max , T2 (1) Less than T2 (0) And with T2 (0) Adjacent, get γ(T2 (0) ),calculate ; (2-3) Construct the second judgment condition: ; The second judgment condition is judged: If it is satisfied, get the second judgment condition ; Substitute into the following formula (9) and calculate T2(r (pc) ); （9） If not satisfied, reduce T2 (0) The value is obtained, and the second judgment condition is judged again until a value that satisfies the second judgment condition is obtained. , re-substituting into formula (9) to calculate r (pc) The corresponding T2(r (pc) ); (2-4): Gradually reduce r (pc) Take the value and restart the calculation until you get r (pc) =r min (pc) T2(r (pc) ); Step 3: Calculate C using the following formula (10): （10） Step 4: Combine C and T2 (NMR) Convert to p c (T2); Where: T2 is the transverse relaxation time, ms; T2 (NMR) is the transverse relaxation time of NMR, ms; T2(p c (HPMI) ) is the transverse relaxation time corresponding to the capillary force of high-pressure mercury injection, ms; T 2max M is the intermediate parameter, ms; T 2max is the maximum transverse relaxation time of NMR, ms; r max (pc) is the maximum pore throat radius of high-pressure mercury injection, um; p c (HPMI) is the high-pressure mercury injection capillary force, MPa; ω is the correction factor, dimensionless; T2(r (pc) ) is the transverse relaxation time corresponding to the pore throat radius of high-pressure mercury injection, ms; r (pc) is the pore throat radius of high-pressure mercury injection, um; is γ(r (pc) ) to γ(r max (pc) ) is the cumulative volume percentage, dimensionless; γ(r (pc) ) is r (pc) The corresponding volume fraction is dimensionless; γ(r max (pc) ) is r max (pc) The corresponding volume fraction, dimensionless; γ pc For calculation The intermediate variable of , dimensionless; T2 (0) is the first intermediate parameter, ms; T2 (1) is the second intermediate parameter, ms, T2 (1) <T2 (0) ≤T 2max And with T2 (0) adjacent; γ(T2 (1) ) is T2 (1) The corresponding volume fraction, dimensionless; is γ(T2 (0) ) to γ(T 2max )’s cumulative volume share, dimensionless; γ T2 For calculation The intermediate variable is dimensionless; γ(T2 (0) ) is T2 (0) The corresponding volume fraction is dimensionless; γ(T 2max ) is T 2max The corresponding volume fraction, dimensionless; r min (pc) is the minimum pore throat radius of high-pressure mercury injection, um; C is the conversion coefficient, μm / ms; p c (T2) is the NMR capillary force, MPa.

2. The method for converting transverse relaxation time distribution into capillary force distribution according to claim 1, characterized in that: The p c The specific acquisition process of (T2) is as follows: p c (T2)=0.735 / (CT2 (NMR) )。 3. The method for converting transverse relaxation time distribution into capillary force distribution according to claim 1, characterized in that: The T2 (NMR) and T 2max Obtained through nuclear magnetic resonance experiments.

4. The method for converting transverse relaxation time distribution into capillary force distribution according to claim 1, characterized in that: The p c (HPMI) 、r (pc) 、r max (pc) and r min (pc) All of them were obtained through high-pressure mercury injection experiments.

5. The method for converting transverse relaxation time distribution into capillary force distribution according to claim 1, characterized in that: The reduction of T 2max M The value varies with T2 (NMR) The distribution data changes.

6. The method for converting transverse relaxation time distribution into capillary force distribution according to claim 1, characterized in that: The reduction r (pc) The value varies with r (pc) The distribution data changes.

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