Carbonate rock water saturation modeling method and device based on pore structure classification

Abstract

The invention discloses a carbonate rock water saturation modeling method and device based on pore structure classification, and belongs to the technical field of rock physics and well logging interpretation. Carrying out matched conventional pore permeability, rock electricity, casting body slice, nuclear magnetic resonance and constant-speed mercury injection experiments on the reservoir core; dividing pore structures into four types according to core casting body sheet characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics and capillary pressure curve forms; the actual water saturation of the reservoir rock core is obtained according to the nuclear magnetic resonance experiment in the rock core saturation and centrifugal state; respectively fitting rock electrical parameters for the four pore structure types; and calculating the water saturation of the whole well section in combination with an Archie formula. According to the method, the relation between the carbonate rock pore structure and the rock electrical parameters is fully excavated, the problem that the non-Archie phenomenon of the heterogeneous carbonate rock reservoir is serious is solved, and the calculation precision of the water saturation is greatly improved.

Description

Technical Field

[0001] The invention relates to the field of petroleum exploration and development, belongs to the category of rock physics and well logging interpretation, and specifically relates to a carbonate rock water saturation modeling method based on pore structure classification. Background Art

[0002] Due to regional differences, diagenetic environment and many other factors, the genesis of oil and gas reservoirs is not the same, so when evaluating reservoir water saturation, it is necessary to use an appropriate method model for quantitative interpretation. Establishing a saturation interpretation model based on the Archie Equation is still the most basic method in well logging evaluation.

[0003] However, due to the strong heterogeneity of carbonate reservoirs, a single rock electrical parameter obviously cannot meet the calculation accuracy. Therefore, it is particularly important to establish dynamic rock electrical parameters based on pore structure to improve the accuracy of water saturation.

[0004] At present, there is no unified conclusion on the water saturation model of carbonate reservoirs in the Leikoupo Formation Lei 3 in a certain basin. There are mainly three problems: 1) The diagenetic process of carbonate rocks is changeable, and microcracks and dissolution pores are developed, resulting in a complex conductive mechanism; 2) The pore structure is complex, resulting in a wide range of changes in the cementation index m and saturation index n; 3) The accuracy of water saturation needs to be improved. Therefore, it is urgent to provide a method that can improve the accuracy of water saturation modeling. Summary of the invention

[0005] The present invention aims to solve the problem of insufficient accuracy of water saturation evaluation models in the prior art, and proposes a carbonate rock water saturation modeling method and device based on pore structure classification. The present invention classifies the pore structure into four categories based on core data of various scales, and classifies the rock electrical parameter modeling, thereby improving the accuracy of modeling of formation factors and porosity, resistivity increase coefficient and water saturation.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0007] A carbonate rock water saturation modeling method based on pore structure classification, characterized by comprising the following steps:

[0008] Carry out routine logging and drilling coring of the study layer;

[0009] Carry out supporting conventional porosity, rock electrical, casting thin section, nuclear magnetic resonance, and constant rate mercury injection experiments on reservoir cores;

[0010] According to the core casting thin section characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics, and capillary pressure curve morphology, the pore structure is divided into type I pore structure, type II pore structure, type III pore structure, and type IV pore structure according to grade.

[0011] The actual water saturation of the reservoir core is obtained based on the nuclear magnetic resonance experiments under core saturation and centrifugal conditions;

[0012] The rock electrical parameters of the reservoir cores are fitted according to the pore structure types;

[0013] Based on the pore structure division results, the water saturation of the entire well section is calculated in combination with the Archie formula and compared with the actual water saturation of the reservoir core.

[0014] Furthermore, the NMR T2 spectrum distribution of the type I pore structure is a bimodal coarse pore throat type, with a porosity greater than 12%, a permeability K>4.5mD, and an irreducible water saturation <35%.

[0015] Furthermore, the NMR T2 spectrum of the type II pore structure is a three-peak coarse pore throat type, with a porosity between 6 and 12%, a permeability between 0.75 and 4.5 mD, and an irreducible water saturation between 35 and 60%.

[0016] Furthermore, the NMR T2 spectrum of the type III pore structure is a three-double peak mesopore throat type, with a porosity between 3 and 6%, a permeability between 0.05 and 1.75 mD, and an irreducible water saturation between 60 and 70%.

[0017] Furthermore, the nuclear magnetic resonance T2 spectrum of the type IV pore structure is a bimodal fine pore throat type, with a porosity of less than 3%, a permeability distribution below 0.05 mD, and an irreducible water saturation of >70%.

[0018] Furthermore, the rock electrical parameter fitting of the reservoir core according to the pore structure type specifically includes:

[0019] Based on the pore structure classification results, with the help of Archie's formula, the relationship between formation factors and porosity is re-established:

[0020] Type I pore structure: F = φ -1.899 , R 2 =0.9836; (4)

[0021] Type II pore structure: F = φ -1.8756 , R 2 =0.9461; (5)

[0022] Type III pore structure: F = φ -1.7956 , R 2 =0.9657; (6)

[0023] Type IV pore structure: F = φ -1.6039 , R 2 =0.9838; (7)

[0024] Re-establishing the relationship between resistivity increase rate and water saturation, we have:

[0025] Type I pore structure: R 2 =0.9296; (8)

[0026] Type II pore structure: R 2 =0.8978; (9)

[0027] Type III pore structure: R 2 =0.8740; (10)

[0028] Type IV pore structure: R 2 =0.8992; (11)

[0029] According to the fitting results, the rock electrical parameters a=b=1 are obtained;

[0030] The cementation index of type I pore structure is m = 1.89, and the saturation index is n = 2.31;

[0031] Type II pore structure has a cementation index of m = 1.87 and a saturation index of n = 2.70;

[0032] Type III pore structure has a cementation index of m = 1.79 and a saturation index of n = 3.17;

[0033] The cementation index of type IV pore structure is m=1.60, and the saturation index is n=3.53.

[0034] The present invention also discloses a carbonate rock water saturation modeling device based on pore structure classification, which is characterized by comprising: a reservoir core acquisition module for performing conventional well logging and drilling coring on the research layer;

[0035] Data acquisition module, used to carry out conventional porosity, rock electrical, casting thin section, nuclear magnetic resonance, constant rate mercury injection experiments on reservoir cores and obtain relevant data;

[0036] The pore structure classification module is used to classify the pore structure into Class I pore structure, Class II pore structure, Class III pore structure and Class IV pore structure according to the core casting thin section characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics and capillary pressure curve morphology;

[0037] The actual water saturation measurement module is used to obtain the actual water saturation of the reservoir core according to the nuclear magnetic resonance experiment under the core saturation and centrifugal state;

[0038] The rock electrical parameter classification fitting module is used to fit the rock electrical parameters of the reservoir core according to the pore structure type;

[0039] The water saturation calculation module is used to calculate the water saturation of the entire well section according to the Archie formula and compare it with the actual water saturation of the reservoir core.

[0040] Furthermore, the pore structure classification module divides the Type I pore structure into two types, whose NMR T2 spectrum distribution is a bimodal coarse pore throat type, with a porosity greater than 12%, a permeability K>4.5mD, and an irreducible water saturation <35%.

[0041] Furthermore, the type II pore structure classified by the pore structure classification module has a three-peak coarse pore throat type in its nuclear magnetic resonance T2 spectrum, a porosity between 6 and 12%, a permeability between 0.75 and 4.5 mD, and a bound water saturation between 35 and 60%.

[0042] Furthermore, the Class III pore structure classified by the pore structure classification module has a three-double peak mesopore throat type NMR T2 spectrum, a porosity between 3 and 6%, a permeability between 0.05 and 1.75 mD, and an irreducible water saturation between 60 and 70%.

[0043] Furthermore, the pore structure classification module divides the Class IV pore structure, whose NMR T2 spectrum is a bimodal fine pore throat type, with a porosity of less than 3%, a permeability distribution below 0.05 mD, and a bound water saturation of >70%.

[0044] Furthermore, the rock electrical parameter classification fitting module is specifically used for:

[0045] Based on the pore structure classification results, with the help of Archie's formula, the relationship between formation factors and porosity, resistivity increase rate and water saturation is re-established, and cross plots of formation factors and porosity, resistivity increase coefficient and saturation are made to obtain the rock electrical parameters of various pore structures.

[0046] In summary, the present invention has the following advantages:

[0047] 1. The method of the present invention intuitively and quantitatively evaluates the development of fractures and caves in carbonate reservoirs based on core casting thin section data, thereby evaluating reservoir connectivity; deeply analyzes the distribution of nuclear magnetic resonance T2 spectra to obtain pore structure information, and calculates water saturation using T2 spectra under saturated and centrifugal core states; and uses the advantage of constant-rate mercury injection to separate pores and throats to analyze the pore throat distribution of carbonate reservoir cores;

[0048] 2. The method of the present invention classifies the pore structure into four categories based on core data of various scales, and classifies the rock electrical parameter modeling, thereby improving the accuracy of modeling of formation factors and porosity, resistivity increase coefficient and water saturation;

[0049] 3. The method of the present invention applies the rock electrical parameters based on pore structure classification to the logging evaluation of the entire well section, and uses the water saturation calibration obtained by core measurement. The accuracy is improved compared with the water saturation obtained without pore structure classification. The water saturation calculation result with high accuracy is more conducive to reflecting the gas content of carbonate reservoirs, thereby providing favorable technical support for reservoir fluid identification and reserve calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the method flow of the present invention;

[0051] Figure 2 This is the capillary pressure curve of Type I pore structure in the study area of ​​the present invention;

[0052] Figure 3 This is the capillary pressure curve of the Type II pore structure in the study area of ​​the present invention;

[0053] Figure 4 This is the capillary pressure curve of the Type III pore structure in the study area of ​​the present invention;

[0054] Figure 5 This is the capillary pressure curve of the Type IV pore structure in the study area of ​​the present invention;

[0055] Figure 6 This is a schematic diagram of the nuclear magnetic resonance of the type I pore structure in the study area of ​​the present invention;

[0056] Figure 7 This is a schematic diagram of the nuclear magnetic resonance of the type II pore structure in the study area of ​​the present invention;

[0057] Figure 8 This is a schematic diagram of the nuclear magnetic resonance of the type III pore structure in the study area of ​​the present invention;

[0058] Fig. 9 This is a schematic diagram of the nuclear magnetic resonance of the type IV pore structure in the study area of ​​the present invention;

[0059] Fig.10 This is the characteristic diagram of the thin section of the cast body with type I pore structure in the study area of ​​the present invention;

[0060] Fig.11 This is the characteristic diagram of the thin section of the cast body with type II pore structure in the study area of ​​the present invention;

[0061] Fig.12 This is the characteristic diagram of the thin section of the cast body with type III pore structure in the study area of ​​the present invention;

[0062] Fig.13 This is the characteristic diagram of the thin section of the cast body with type IV pore structure in the study area of ​​the present invention;

[0063] Fig.14This is a relationship diagram between formation factors and porosity when the pore structure is not distinguished in the study area of ​​the present invention;

[0064] Fig.15 This is a relationship diagram between the resistivity increase coefficient and the water saturation when the pore structure is not distinguished in the study area of ​​the present invention;

[0065] Fig.16 A diagram showing the relationship between formation factors and porosity when distinguishing pore structures in the present invention;

[0066] Fig.17 This is a relationship diagram between resistivity increase coefficient and water saturation when studying the pore structure of the area in the present invention;

[0067] Fig.18 This is a schematic diagram of the water saturation calculation result obtained by the method of the present invention; DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0069] Example 1

[0070] This embodiment discloses a carbonate rock water saturation modeling method based on pore structure classification. Figure 1 As shown, the following steps are included:

[0071] Step 1: Conduct conventional logging and drilling coring on the studied layer;

[0072] Step 2: Conduct conventional porosity, rock electrical, casting thin section, nuclear magnetic resonance, and constant rate mercury injection experiments on reservoir cores;

[0073] Step 3: According to the core casting thin section characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics, and capillary pressure curve morphology, the pore structure is divided into Class I pore structure, Class II pore structure, Class III pore structure, and Class IV pore structure according to grade; wherein:

[0074] The NMR T2 spectrum distribution of type I pore structure is bimodal coarse pore throat type, with porosity greater than 12%, permeability K>4.5mD, and irreducible water saturation <35%;

[0075] The nuclear magnetic resonance T2 spectrum of type II pore structure is a three-peak coarse pore throat type, with a porosity between 6 and 12%, a permeability between 0.75 and 4.5 mD, and an irreducible water saturation between 35 and 60%.

[0076] The nuclear magnetic resonance T2 spectrum of the type III pore structure is a three-double peak mesopore throat type, with a porosity between 3% and 6%, a permeability between 0.05 and 1.75 mD, and an irreducible water saturation between 60 and 70%.

[0077] The nuclear magnetic resonance T2 spectrum of type IV pore structure is a double-peak fine pore throat type, with a porosity of less than 3%, a permeability distribution below 0.05mD, and a bound water saturation of >70%.

[0078] Step 4: Obtain the actual water saturation of the reservoir core according to the nuclear magnetic resonance experiment under the core saturation and centrifugal state;

[0079] Step 5: Fitting the rock electrical parameters of the reservoir cores according to the pore structure types;

[0080] Step 6: Based on the pore structure division results, the Archie formula is used to calculate the water saturation of the entire well section.

[0081] The present invention intuitively and quantitatively evaluates the development of carbonate reservoir fractures and caves based on core casting thin section data, thereby evaluating reservoir connectivity; deeply analyzes the distribution of nuclear magnetic resonance T2 spectrum to obtain pore structure information, and uses the T2 spectrum of the core under saturated and centrifugal conditions to calculate water saturation; and uses the advantage of constant-rate mercury injection to separate pores and throats to analyze the distribution of pore throats in carbonate reservoir cores. The pore structures obtained by integrating core data of various scales are divided into four categories, and rock electrical parameter modeling is carried out by classification, which improves the accuracy of modeling of formation factors and porosity, resistivity increase coefficient and water saturation.

[0082] Example 2

[0083] This embodiment discloses a carbonate rock water saturation modeling method based on pore structure classification. Figure 1 As shown, the following steps are included:

[0084] Step 1: Conduct conventional logging and drilling coring on the studied layer;

[0085] Step 2: Conduct supporting conventional porosity, rock electrical, casting thin section, nuclear magnetic resonance, and constant rate mercury injection experiments on the reservoir core of the Leikoupo Formation Lei 3 in the Sichuan Basin;

[0086] Step 3: Cast thin sections, nuclear magnetic resonance and capillary pressure experiments can well characterize the rock pore structure. Therefore, the present invention divides the pore structure based on the core cast thin section characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics, and capillary pressure curve morphology. According to the influence of the pore structure characteristics on the rock electrical properties, the saturation interpretation model is determined. The pore structure is divided into four categories, which makes the selection of rock electrical parameters more precise and accurate, and the final saturation calculation is more realistic. The division results are as follows: Figures 2 to 13 As shown, the features are as follows:

[0087] The nuclear magnetic resonance T2 spectrum distribution of type I pore structure is a bimodal coarse pore throat type, with a porosity generally greater than 12%, a permeability K generally>4.5mD, a bound water saturation generally <35%, and some microfractures developed; the mercury injection curve shows a low displacement pressure, averaging 0.097Mpa, an average mercury saturation of 65.363%, a long flat section of the curve and the lowest position, most of the pore throat radii are greater than 5μm, and the distribution range is wide, but the main throat control is obvious, showing a combination of medium, small and large throats, and mainly large throats. The rock has good storage and permeability.

[0088] The nuclear magnetic resonance T2 spectrum of the type II pore structure is a three-peak coarse pore throat type, with a porosity generally between 6 and 12%, a permeability generally between 0.75 and 4.5 mD, and a bound water saturation generally between 35 and 60%. The mercury injection curve shows that the average displacement pressure is 0.446 MPa, the average mercury saturation is 62%, the pore throat radius varies in a large range, the proportion of large pore throats is not high, and large throats, medium throats and small throats exist, so the pore throat structure is worse than that of type I.

[0089] The nuclear magnetic resonance T2 spectrum of type III pore structure is a three-double peak medium pore throat type, the porosity is generally between 3 and 6%, the permeability is generally between 0.05 and 1.75 mD, and the bound water saturation is generally between 60 and 70%; the mercury injection curve shows an average displacement pressure of 1.024 MPa, the pore throat radius is less than 2 um, the medium throat is dominant, there are also many small throats, and the pore throat structure is poor.

[0090] The nuclear magnetic resonance T2 spectrum of type IV pore structure is a double-peak fine pore throat type, with a porosity generally less than 3%, a permeability generally distributed below 0.05mD, and a bound water saturation generally >70%; the mercury injection curve shows that the average displacement pressure is as high as 1.098Mpa, and more than 90% of the pore throat radii are less than 0.3um, mainly throats, and the pore throat structure is the worst.

[0091] Step 4: Obtain the actual water saturation of the core according to the nuclear magnetic resonance experiment under the core saturation and centrifugal state;

[0092] Step 5: First, make the formation factor F and porosity Φ, resistivity increase coefficient I and saturation S without distinguishing the pore structure type. w The intersection diagram of Fig.14 and Fig.15 shown.

[0093] In this step, Archie's formula is used to study the relationship between porosity and resistivity, and all cores are integrated to model the formation factors and porosity, resistivity increase coefficient and water saturation, and the rock electrical parameters a = 1, b = 1.13, m = 1.72, n = 2.53 are obtained, then:

[0094]

[0095] F=φ -1.7258 , R 2 =0.6513; (2)

[0096] R 2 =0.7757; (3)

[0097] Where, F is the formation resistivity factor;

[0098] Φ——porosity;

[0099] I——resistance increase coefficient;

[0100] R W ——Resistivity of formation water, Ω.m;

[0101] S w ——water saturation;

[0102] R0——Resistivity of pure rock containing 100% water;

[0103] R 2 ——Correlation coefficient.

[0104] It can be found that the correlation coefficient R 2 Less than 0.8, therefore, when the rock electrical parameters are fitted regardless of the pore structure type, the fitting effect does not meet the standard.

[0105] Step 6: Draw cross-plots of formation factors, porosity, resistivity increase coefficient and saturation according to pore structure types, such as Fig.16 and Fig.17 shown.

[0106] Based on the pore structure classification results, the relationship between formation factors and porosity is re-established, and the correlation coefficient is significantly improved, which can better reflect the relationship between formation factors and porosity. The expressions after classification are shown in equations (4) to (7):

[0107] Type I pore structure: F = φ -1.899 , R 2 =0.9836; (4)

[0108] Type II pore structure: F = φ -1.8756 , R 2 =0.9461; (5)

[0109] Type III pore structure: F = φ -1.7956 , R 2 =0.9657; (6)

[0110] Type IV pore structure: F = φ-1.6039 , R 2 =0.9838. (7)

[0111] Based on the pore structure classification results, the relationship between the resistivity increase rate and water saturation is re-established. It can be found that the correlation coefficient has improved significantly, and the correlation coefficient value has reached above 0.85, which can better reflect the relationship between the resistivity increase rate and water saturation. The expressions after classification are shown in equations (8) to (11):

[0112] Type I pore structure: R 2 =0.9296; (8)

[0113] Type II pore structure: R 2 =0.8978; (9)

[0114] Type III pore structure: R 2 =0.8740; (10)

[0115] Type IV pore structure: R 2 =0.8992. (11)

[0116] According to the fitting results, the rock electrical parameters a=b=1 are obtained; the cementation index m=1.89 and the saturation index n=2.31 of type I pore structure; the cementation index m=1.87 and the saturation index n=2.70 of type II pore structure; the cementation index m=1.79 and the saturation index n=3.17 of type III pore structure; the cementation index m=1.60 and the saturation index n=3.53 of type IV pore structure.

[0117] It can be seen that as the pore structure deteriorates, the m value gradually decreases, the n value gradually increases, and the water saturation value decreases.

[0118] Step 7: Combine Archie's formula to calculate the water saturation of the entire well section. This method is applied to Well 80 in the Leikoupo Formation Lei Section 3 in the Sichuan Basin. The water saturation calculation results are as follows: Fig.18 As shown, the 8th column is the calculated water saturation. After calibration and comparison with the core data, the calculated results are in good agreement with the water saturation actually measured by the core test.

[0119] Example 3

[0120] This embodiment discloses a carbonate rock water saturation modeling device based on pore structure classification, which includes a reservoir core acquisition module, a data acquisition module, a pore structure classification module, an actual water saturation measurement module, a rock electrical parameter classification fitting module and a water saturation calculation module.

[0121] The reservoir core acquisition module is used for conventional logging and drilling coring of the studied layers;

[0122] The data acquisition module is used to carry out conventional porosity, rock electricity, casting thin section, nuclear magnetic resonance, and constant-rate mercury injection experiments on reservoir cores and obtain relevant data;

[0123] The pore structure classification module is used to classify the pore structure into Class I pore structure, Class II pore structure, Class III pore structure and Class IV pore structure according to the core casting thin section characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics and capillary pressure curve morphology;

[0124] The actual water saturation measurement module is used to obtain the actual water saturation of the reservoir core according to the nuclear magnetic resonance experiment under the core saturation and centrifugal state;

[0125] The rock electrical parameter classification fitting module is used to fit the rock electrical parameters of reservoir cores according to the pore structure type; more specifically, based on the four classification results of pore structure, with the help of Archie's formula, the relationship between formation factors and porosity, resistivity increase rate and water saturation is re-established, and the formation factors and porosity, resistivity increase coefficient and saturation are cross-plotted to obtain the rock electrical parameters of various pore structures.

[0126] The water saturation calculation module is used to calculate the water saturation of the entire well section according to the Archie formula and compare it with the actual water saturation of the reservoir core.

[0127] The type I pore structure classified by the pore structure classification module has a bimodal coarse pore throat type NMR T2 spectrum distribution, porosity greater than 12%, permeability K>4.5mD, irreducible water saturation <35%, and some microcracks developed; the mercury injection curve shows a low displacement pressure, averaging 0.097Mpa, an average mercury saturation of 65.363%, a long flat section of the curve and the lowest position, most of the pore throat radii are greater than 5μm, and the distribution range is wide, but the main throat control is obvious, showing a combination of medium, small and large throats, and mainly large throats. The rock has good reservoir and permeability.

[0128] The pore structure classification module divides the Class II pore structure into three-peak coarse pore throat type, with a porosity of 6-12%, a permeability of 0.75-4.5mD, and a bound water saturation of 35-60%. The mercury injection curve shows that the average displacement pressure is 0.446Mpa, the average mercury injection saturation is 62%, the pore throat radius varies widely, the proportion of large pore throats is not high, and there are large throats, medium throats, and small throats, so the pore throat structure is worse than Class I.

[0129] The pore structure classification module divides the Class III pore structure, whose NMR T2 spectrum is a three-double peak medium pore throat type, with a porosity between 3% and 6%, a permeability between 0.05 and 1.75 mD, and a bound water saturation between 60 and 70%. The mercury injection curve shows an average displacement pressure of 1.024 MPa, a pore throat radius of less than 2 um, mainly medium throats, and a large number of small throats, and a poor pore throat structure.

[0130] The IV type pore structure classified by the pore structure classification module has a double-peak fine pore throat type in its NMR T2 spectrum, a porosity of less than 3%, a permeability distribution below 0.05mD, and a bound water saturation of >70%. The mercury injection curve shows that the average displacement pressure is as high as 1.098Mpa, and more than 90% of the pore throat radii are less than 0.3um, mainly throats, and the pore throat structure is the worst.

[0131] Although the specific implementation of the present invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

[0132] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A carbonate rock water saturation modeling method based on pore structure classification, characterized in that: The steps include: Carry out routine logging and drilling coring of the study layer; Carry out supporting conventional porosity, rock electrical, casting thin section, nuclear magnetic resonance, and constant rate mercury injection experiments on reservoir cores; According to the core casting thin section characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics, and capillary pressure curve morphology, the pore structure is divided into type I pore structure, type II pore structure, type III pore structure, and type IV pore structure according to grade. The actual water saturation of the reservoir core is obtained based on the nuclear magnetic resonance experiments under core saturation and centrifugal conditions; The rock electrical parameters of the reservoir cores are fitted according to the pore structure types; Based on the pore structure division results, the water saturation of the entire well section is calculated in combination with the Archie formula and compared with the actual water saturation of the reservoir core.

2. The carbonate rock water saturation modeling method based on pore structure classification according to claim 1 is characterized in that: The NMR T2 spectrum distribution of type I pore structure is a bimodal coarse pore throat type, with a porosity greater than 12%, a permeability K>4.5mD, and an irreducible water saturation <35%.

3. The carbonate rock water saturation modeling method based on pore structure classification according to claim 1 is characterized in that: The nuclear magnetic resonance T2 spectrum of the type II pore structure is a three-peak coarse pore throat type, with a porosity between 6 and 12%, a permeability between 0.75 and 4.5 mD, and a bound water saturation between 35 and 60%.

4. The carbonate rock water saturation modeling method based on pore structure classification according to claim 1 is characterized in that: The nuclear magnetic resonance T2 spectrum of the type III pore structure is a three-double peak mesopore throat type, with a porosity between 3 and 6%, a permeability between 0.05 and 1.75 mD, and an irreducible water saturation between 60 and 70%.

5. The carbonate rock water saturation modeling method based on pore structure classification according to claim 1 is characterized in that: The nuclear magnetic resonance T2 spectrum of type IV pore structure is a double-peak fine pore throat type, with a porosity of less than 3%, a permeability distribution below 0.05mD, and a bound water saturation of >70%.

6. The carbonate rock water saturation modeling method based on pore structure classification according to claim 1 is characterized in that: The rock electrical parameter fitting of the reservoir core according to the pore structure type specifically includes: Based on the pore structure classification results, with the help of Archie's formula, the relationship between formation factors and porosity is re-established: Type I pore structure: F = φ -1.899 , R 2 =0.9836; (4) Type II pore structure: F = φ -1.8756 , R 2 =0.9461; (5) Type III pore structure: F = φ -1.7956 , R 2 =0.9657; (6) Type IV pore structure: F = φ -1.6039 , R 2 =0.9838; (7) Re-establishing the relationship between resistivity increase rate and water saturation, we have: Type I pore structure: R 2 =0.9296; (8) Type II pore structure: R 2 =0.8978; (9) Type III pore structure: R 2 =0.8740; (10) Type IV pore structure: R 2 =0.8992; (11) According to the fitting results, the rock electrical parameters a=b=1 are obtained; The cementation index of type I pore structure is m = 1.89, and the saturation index is n = 2.31; Type II pore structure has a cementation index of m = 1.87 and a saturation index of n = 2.70; Type III pore structure has a cementation index of m = 1.79 and a saturation index of n = 3.17; The cementation index of type IV pore structure is m=1.60, and the saturation index is n=3.

53.

7. A carbonate rock water saturation modeling device based on pore structure classification, characterized in that: include: Reservoir core acquisition module, used for conventional logging and drilling coring of the studied layers; Data acquisition module, used to carry out conventional porosity, rock electrical, casting thin section, nuclear magnetic resonance, constant rate mercury injection experiments on reservoir cores and obtain relevant data; The pore structure classification module is used to classify the pore structure into Class I pore structure, Class II pore structure, Class III pore structure and Class IV pore structure according to the core casting thin section characteristics, nuclear magnetic resonance T2 spectrum distribution characteristics and capillary pressure curve morphology; The actual water saturation measurement module is used to obtain the actual water saturation of the reservoir core according to the nuclear magnetic resonance experiment under the core saturation and centrifugal state; The rock electrical parameter classification fitting module is used to fit the rock electrical parameters of the reservoir core according to the pore structure type; The water saturation calculation module is used to calculate the water saturation of the entire well section according to the Archie formula and compare it with the actual water saturation of the reservoir core.

8. The carbonate rock water saturation modeling device based on pore structure classification according to claim 7, characterized in that: The type I pore structure classified by the pore structure classification module has a bimodal coarse pore throat type NMR T2 spectrum distribution, a porosity greater than 12%, a permeability K>4.5mD, and an irreducible water saturation <35%. The type II pore structure classified by the pore structure classification module has a three-peak coarse pore throat type in the nuclear magnetic resonance T2 spectrum, a porosity between 6 and 12%, a permeability between 0.75 and 4.5 mD, and a bound water saturation between 35 and 60%.

9. The carbonate rock water saturation modeling device based on pore structure classification according to claim 7, characterized in that: The type III pore structure classified by the pore structure classification module has a three-double peak medium pore throat type NMR T2 spectrum, a porosity between 3 and 6%, a permeability between 0.05 and 1.75 mD, and a bound water saturation between 60 and 70%. The pore structure classification module classifies the type IV pore structure, whose nuclear magnetic resonance T2 spectrum is a bimodal fine pore throat type, with a porosity of less than 3%, a permeability distribution below 0.05 mD, and a bound water saturation of >70%.

10. The carbonate rock water saturation modeling device based on pore structure classification according to claim 7, characterized in that: The rock electrical parameter classification fitting module is specifically used for: Based on the pore structure classification results, with the help of Archie's formula, the relationship between formation factors and porosity, resistivity increase rate and water saturation is re-established, and cross plots of formation factors and porosity, resistivity increase coefficient and saturation are made to obtain the rock electrical parameters of various pore structures.

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