Calculation method for parameters of three - water conductivity model based on nuclear magnetic resonance - constrained conventional logging

Abstract

Aiming at the technical problem that the triple-water conductivity model has too many parameters and a large amount of core experimental data such as mercury injection, rock electricity experiment, clay analysis, cation exchange capacity, etc. are required in the prior art to determine the model parameters, the present invention innovatively proposes a method for calculating the parameters of the triple-water conductivity model based on nuclear magnetic resonance constrained conventional logging. The calculation method substitutes the free fluid porosity, micro-capillary water porosity, and clay water porosity obtained from nuclear magnetic resonance logging interpretation into the formula of the triple-water conductivity model expressed by conventional logging parameters, combines with parameters such as porosity, shale content, and irreducible water saturation interpreted by conventional logging, and finally achieves the calculation of all model parameters without relying on experimental data. When calculating the parameters, relying on the characteristics of the large data sample of the logging data itself and assisted by the optimization algorithm of multiple groups of data, the calculation accuracy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of logging reservoir evaluation in oil and gas reservoirs, and particularly relates to a method for calculating parameters of a triple-water conductivity model based on nuclear magnetic resonance constrained conventional logging. Background Art

[0002] With the in-depth exploration of oil and gas, more and more reservoirs show "non-Archie" phenomena, especially reservoirs with complex lithology, low porosity and permeability, and low resistivity. Saturation formulas such as the shale parallel conductivity model, the W-S model, and the dual-water model have been gradually proposed under certain specific circumstances and replaced the Archie formula to obtain more accurate calculation results. The proposed triple-porosity water conductivity model (hereinafter referred to as the triple-water conductivity model) meets the quantitative evaluation of saturation in more complex clastic rock reservoirs. The triple-water conductivity model believes that the conductive media in the reservoir include formation water in free fluid pores (referred to as free water for short), bound water in micro-capillary pores (referred to as micro-pore water for short), and clay water in clay pores. Among them, the conductivities of free pore formation water and micro-pore bound water are the same and both are ionic conduction, the clay water is cation exchange conduction and its conductivity is different from that of free water, and the total conductivity of the rock is the parallel connection of the three parts of the media.

[0003] The triple-water conductivity model well characterizes the contribution of different conductive media to the conductivity of the rock. However, the triple-water conductivity model requires many parameters to be determined, including the resistivities of free water, micro-pore water, and clay water, the volumes of free water, micro-pore water, and clay water, and the cementation indices corresponding to the three fluids and the saturation index of free water.

[0004] In the prior art, the methods for determining the parameters of the triple-water conductivity model are divided into two categories. One category completely depends on various experimental data. For example, a method for establishing a triple-water component difference parallel conductivity water saturation model disclosed in CN114862113B. Various experimental data include porosity, permeability, relative permeability, mercury injection, nuclear magnetic resonance, cation exchange capacity, grain size analysis, and rock electricity experiments, etc. This type of method has a high cost and great limitations. It is not applicable to areas without rich experimental data, and the obtained results have regional statistics and are only applicable to the restricted study area, making it difficult to promote and use.

[0005] The other category is to rely on conventional logging data and certain empirical coefficients to calculate model parameters. For example, porosity is calculated using neutron, density, and acoustic curves, shale content is calculated using gamma curves, and then clay content is calculated according to empirical formulas to determine the volume of clay water, etc. This type of method has low calculation result accuracy due to the accuracy limitations of conventional logging itself and the use of empirical formulas in some steps, making it difficult to meet the requirements of current exploration and development. Summary of the Invention

[0006] Aiming at the technical problem that there are too many parameters in the three - water conductivity model in the prior art, and a large amount of core experimental data such as mercury injection, rock - electricity experiment, clay analysis, cation exchange capacity, etc. are required to determine the model parameters, a calculation method for the parameters of the three - water conductivity model based on nuclear magnetic resonance (NMR) - constrained conventional logging is proposed. This calculation method adopts a new calculation idea, substituting the free - fluid porosity, micro - capillary porosity, and clay - water porosity obtained from NMR logging interpretation into the three - water conductivity model formula represented by conventional logging data, and combining with conventional logging parameters, finally achieving the calculation of all model parameters without relying on experimental data. At the same time, relying on the characteristics of the large - data sample of logging data itself, an optimization algorithm for multiple groups of data is used to assist in parameter calculation, improving the calculation accuracy.

[0007] To achieve the above object, the present invention provides a calculation method for the parameters of the three - water conductivity model based on NMR - constrained conventional logging, which includes the following steps:

[0008] Step S1: Establish a three - water conductivity model of the rock based on the theory of parallel conductivity of multiple media, and obtain the calculation formulas for the conductivity of the fully - water - saturated rock and the oil - and - gas - bearing rock.

[0009] Step S2: For the three - water conductivity model of the fully - water - saturated rock and the oil - and - gas - bearing rock, calculate the resistivity of free water , the resistivity of micropore water and the resistivity of clay water .

[0010] Step S3: According to the NMR logging response characteristics of the fully - water - saturated rock, calculate the free - fluid porosity , the clay - water porosity , and the micro - capillary porosity

[0011] Step S4: Substitute the , , calculated based on NMR logging of multiple fully - water - saturated rocks into the three - water conductivity model to establish a first over - determined equation set, and apply an optimization algorithm to perform iterative solution on it, and calculate the cementation index of free water , the cementation index of micropore water and the cementation index of clay water

[0012] Step S5: Apply NMR logging to constrain the conventional logging curve, and establish a calculation model for the clay - water volume coefficient of the fully - water - saturated rock based on conventional logging parameters according to the conductivity of the fully - water - saturated rock, and calculate the clay - water volume coefficient .

[0013] Step S6: Establish a calculation model for the saturation index of hydrocarbon-bearing rocks based on conventional logging parameters according to the conductivity of the hydrocarbon-bearing rocks, and calculate the free water saturation index according to the saturation data of oil-bearing cores.

[0014] Step S7: Calculate the cementation index according to the saturation index calculation model and the calculated result. 、 、 the clay water volume coefficient and the free water saturation index , and calculate the water saturation using conventional logging curves. .

[0015] According to an embodiment of the present disclosure, the conductivity of the fully water-bearing rock

[0016] (1)

[0017] The conductivity of the hydrocarbon-bearing rock is expressed as:

[0018] (2)

[0019] Wherein, is the resistivity of the fully water-bearing rock, is the resistivity of the hydrocarbon-bearing rock, , is the water saturation of free fluid pores, is the porosity of free fluid pores.

[0020] According to an embodiment of the present disclosure, step S2 includes the following steps:

[0021] Directly measure the resistivity of formation water by taking formation water samples or analyze the salinity of the formation water, and calculate the resistivity of the formation water according to the salinity;

[0022] Calculate the conductivity of clay water based on the first operation logic and calculate the resistivity of clay water according to the conductivity of clay water ; ;

[0023] Wherein, the resistivity of the formation water and the resistivity of free water , the resistivity of micropore water The values are the same, and the first operation logic is expressed as:

[0024]

[0025] Wherein, is the diffusion factor of the ion diffusion layer is the compensation ion in clay water of the equivalent conductivity, is the cation exchange capacity of the clay is the pore volume occupied by clay water when

[0026] According to an embodiment of the present disclosure, the step S3 includes the following steps:

[0027] Determine the completely water-bearing rock according to the oil and gas well testing data. In the completely water-bearing rock, the clay-bound water volume, capillary-bound water volume, and mobile water volume in the nuclear magnetic resonance logging data processing and interpretation result map are respectively used as the clay water porosity in the three-water conductivity model, the micro-capillary porosity and the free fluid porosity

[0028] According to an embodiment of the present disclosure, the step S4 includes the following steps:

[0029] Select multiple completely water-bearing rocks, and take the clay water porosity, micro-capillary porosity, and free fluid porosity at multiple depth points for each completely water-bearing rock on the nuclear magnetic resonance interpretation result map;

[0030] Determine the resistivity of the completely water-bearing rock corresponding to each depth point according to the resistivity logging curve, establish N equations, and form the first overdetermined equation set;

[0031] Solve the first overdetermined equation set by using the optimization algorithm of the least squares method, and calculate the cementation exponent , , .

[0032] According to an embodiment of the present disclosure, the step S5 includes the following steps:

[0033] Calculate the conventional logging parameters of the completely water-bearing rock according to the conventional logging curve. The conventional logging parameters at least include: shale content , the total porosity of the formation , permeability , irreducible water saturation ;

[0034] Based on the conventional logging parameters, obtain the free fluid porosity in the triple water conductivity model , the clay water porosity , the microcapillary porosity representation formulas;

[0035] Substitute the representation formulas of , , derived based on the conventional logging parameters and the cementation index , , calculated in step S4 into the representation formula of the conductivity of the completely water-saturated rock to establish the clay water volume coefficient calculation model;

[0036] Use an optimization algorithm to solve the clay water volume coefficient .

[0037] According to an embodiment of the present disclosure, step S5 further includes the following steps:

[0038] According to the dual water model, obtain the clay water volume in the unit pore volume based on the cation exchange capacity ;

[0039] Obtain the ratio between the cation exchange capacity and the shale content and define it as the clay water volume coefficient ;

[0040] According to the total porosity and the clay water volume in the unit pore volume represented based on the clay water volume coefficient , obtain the representation formula of the clay water porosity ;

[0041] According to the irreducible water saturation , obtain the representation formula of the microcapillary porosity :

[0042] According to the total porosity the clay water porosity and the microcapillary porosity , obtain the free fluid porosity .

[0043] According to an embodiment of the present disclosure, the calculation of the free water saturation index includes the following steps:

[0044] Based on the experimental data of oil-bearing cores, the water saturation and resistivity of different oil-bearing cores are obtained;

[0045] According to the water saturation, the free fluid pore water saturation is calculated ;

[0046] The different resistivities and the free fluid pore water saturation are substituted into the saturation exponent calculation model to obtain a third overdetermined system of equations;

[0047] The third overdetermined system of equations is solved according to the optimization algorithm to calculate the free water saturation exponent .

[0048] According to an embodiment of the present disclosure, the establishment of the saturation exponent calculation model includes the following steps:

[0049] The depth correction is performed on the taken oil-bearing cores to obtain the conventional logging curves corresponding to the depths of each oil-bearing core;

[0050] Based on the conventional logging curves, the conventional logging parameters are calculated, and the conventional logging parameters at least include: total porosity shale content , permeability , irreducible water saturation ;

[0051] According to the conventional logging parameters, the expressions of free fluid porosity , clay water porosity , and microcapillary porosity in the triple water conductivity model are obtained;

[0052] The expressions of , , obtained based on the conventional logging parameters and the cementation exponent , , calculated in step S4 are substituted into the calculation formula of the conductivity of the oil and gas-bearing rock to establish a saturation exponent calculation model.

[0053] According to an embodiment of the present disclosure, the calculation of the water saturation includes the following steps:

[0054] According to the saturation exponent calculation model, the calculation formula of the free fluid pore water saturation is obtained;

[0055] Substitute the calculated cementation index , , , the clay water volume coefficient A and the free water saturation index into the calculation formula of .

[0056] Calculate conventional logging parameters based on the conventional logging curves, and convert the into the water saturation of total pores based on the conventional logging parameters, and calculate the water saturation .

[0057] On the other hand, the present invention also provides a system for calculating the parameters of a triple-water conductivity model based on nuclear magnetic resonance constrained conventional logging to implement the calculation method in the above technical solution. The calculation system includes:

[0058] Triple-water resistivity calculation module, which analyzes and calculates the free water resistivity and the micro-pore water resistivity based on the salinity of the formation water, and calculates the clay water conductivity based on the first operation logic, and calculates the clay water resistivity according to the clay water conductivity ;

[0059] Triple-water porosity extraction module, which extracts the free fluid porosity , the clay water porosity , and the micro-capillary porosity based on the nuclear magnetic resonance logging interpretation results of the fully water-saturated rock;

[0060] Cementation index calculation module, which forms the first overdetermined equation set based on the free fluid porosity , the clay water porosity , and the micro-capillary porosity obtained from the nuclear magnetic resonance logging data, and calculates the cementation index of free water , the cementation index of micro-pore water , and the cementation index of clay water based on the first overdetermined equation set using the optimization algorithm;

[0061] Conventional logging parameter calculation module, which calculates conventional logging parameters based on conventional logging curves, including at least: shale content, total porosity, permeability, irreducible water saturation;

[0062] The clay water volume coefficient calculation module represents the free fluid porosity, clay water porosity, and micro-capillary porosity based on conventional logging parameters, establishes a calculation model for the clay water volume coefficient of a fully water-bearing rock represented by conventional logging parameters, and calculates the clay water volume coefficient in the calculation model. ;

[0063] The saturation index calculation module establishes a calculation model for the saturation index of an oil and gas-bearing rock based on conventional logging parameters, and calculates the free water saturation index according to the saturation data of the oil-bearing core. ;

[0064] The water saturation calculation module calculates the water saturation using conventional logging curves according to the saturation index calculation model and the calculated cementation index, clay water volume coefficient, and free water saturation index. .

[0065] Compared with the prior art, the advantages and positive effects of the present invention are as follows: A new idea and method for calculating the parameters of the three-water conductivity model are provided. This calculation method makes full use of the advantage that nuclear magnetic resonance logging can accurately calculate the free fluid porosity, micro-capillary porosity, and clay water porosity. It uses nuclear magnetic resonance to constrain conventional logging, and at the same time uses a large number of sample data to establish an equation set and adopts an optimization algorithm for solution. On the one hand, it avoids the limitation of having to rely on experimental data to determine the model parameters. On the other hand, relying on the constraint of nuclear magnetic resonance logging and supplemented by an optimized algorithm, it improves the calculation accuracy of the model parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0067] Figure 1 is a flowchart of the method for calculating the parameters of the three-water conductivity model based on nuclear magnetic resonance constrained conventional logging according to the embodiment of this application;

[0068] Figure 2 is the three-water conductivity model established based on the parallel conductivity theory according to the embodiment of this application;

[0069] Figure 3 is the nuclear magnetic resonance logging interpretation result diagram of a certain section of the formation of the well used according to the embodiment of this application;

[0070] Figure 4 is the crossplot of core porosity and density logging values according to the embodiment of this application;

[0071] Figure 5It is a cross plot of core porosity and neutron porosity log values according to an embodiment of the present application;

[0072] Figure 6 It is a cross plot of core porosity and acoustic travel time log values according to an embodiment of the present application;

[0073] Figure 7 It is a core porosity-permeability cross plot according to an embodiment of the present application;

[0074] Figure 8 It is a cross plot of irreducible water saturation and according to an embodiment of the present application;

[0075] Figure 9 It is a cross plot of irreducible water saturation and shale content according to an embodiment of the present application;

[0076] Figure 10 It is a calculation result plot of the triple water conductivity model according to an embodiment of the present application. Specific Embodiments

[0077] Next, the technical solutions in the embodiments will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0078] In the description of the present invention, it should be understood that the terms "center", "horizontal", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present invention.

[0079] The terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first", "second", "third" may explicitly or implicitly include one or more of such features.

[0080] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0081] There are mainly two technical problems in the existing calculation methods for the parameters of the triple-water conductivity model. First, in the case of lack of experimental data, the parameters of the triple-water model cannot be determined. The triple-water conductivity model is proposed based on the theory of parallel conductivity of multiple media. There are many parameters to be determined in the model, including free-fluid porosity, micro-capillary porosity, clay-water porosity, free-water resistivity, micro-pore water resistivity, clay-water resistivity, cementation indices of the three types of water, and saturation index of free water. If the above parameters can be accurately determined, the accuracy of the water saturation calculated using the triple-water conductivity model is very high. However, determining the above parameters requires a large amount of core experimental data. In addition to the conventional porosity-permeability experimental data, mercury injection, nuclear magnetic resonance experiments, and clay content analysis data are also required. The cementation indices of the three types of water need to combine rock-electrical experimental data with nuclear magnetic resonance or cation exchange capacity, and the determination of clay-water resistivity requires cation exchange capacity experiments. And it is difficult for most research blocks to have all the above experimental data at the same time. Therefore, the parameters of the triple-water conductivity model cannot be fully determined.

[0082] Second, the accuracy of the model parameters determined solely by using conventional logging data is too low. Conventional logging data reflects a certain physical property or physical parameter of the formation, and all indirectly reflect the geological characteristics of the formation from a certain aspect. Because each logging information has indirectness and multi-solution, the accuracy of the geological parameters calculated directly from the conventional logging curves is relatively low. For example, the porosity calculated from acoustic, neutron, or density curves, and the shale content calculated from the natural gamma curve must be used under specific conditions. Therefore, the errors of the parameters of the triple-water conductivity model calculated based on these shale contents and porosities are even higher.

[0083] To address the above two problems, the present invention provides a method for calculating the parameters of the triple-water conductivity model based on nuclear magnetic resonance constrained conventional logging, referring to Figure 1 , and this calculation method includes the following steps:

[0084] Step S1: Establish a triple-water conductivity model of the rock based on the theory of parallel conductivity of multiple media, and obtain the calculation formulas for the conductivity of the completely water-saturated rock and the oil-gas-bearing rock;

[0085] Step S2: For the triple-water conductivity model of the completely water-saturated rock and the oil-gas-bearing rock, calculate the free-water resistivity 、micro-pore water resistivity and the resistivity of clay water ;

[0086] Step S3: Calculate the free fluid porosity, clay water porosity, and microcapillary porosity in the triple-water conductivity model according to the nuclear magnetic resonance logging response characteristics of the fully water-saturated rock , clay water porosity , microcapillary porosity

[0087] Step S4: Substitute the values of the free fluid porosity, clay water porosity, and microcapillary porosity calculated based on nuclear magnetic resonance logging for multiple fully water-saturated rocks into the triple-water conductivity model to establish a first overdetermined system of equations, and use an optimization algorithm to iteratively solve it to calculate the cementation index of free water , , , the cementation index of micropore water , and the cementation index of clay water

[0088] Step S5: Apply nuclear magnetic resonance logging to constrain the conventional logging curves, and establish a calculation model for the clay water volume coefficient of the fully water-saturated rock based on the conventional logging parameters, and calculate the clay water volume coefficient ;

[0089] Step S6: Establish a calculation model for the saturation index of the oil and gas-bearing rock based on the conventional logging parameters according to the conductivity of the oil and gas-bearing rock, and calculate the free water saturation index according to the saturation data of the oil-bearing core

[0090] Step S7: Calculate the water saturation using the conventional logging curves according to the saturation index calculation model, the calculated cementation index , the clay water volume coefficient , and the free water saturation index . .

[0091] The present invention provides a new calculation method, which solves the problem in the prior art that parameter determination must rely on experimental data. At the same time, it makes full use of the large sample characteristics of logging data and the optimization algorithm to ensure the accuracy of the calculation results

[0092] ​Upon retrieval, the comparative document with the publication number CN114862113B can be used as the closest prior art to the present invention. The three-water component differential parallel conduction model described in this comparative document is similar to the three-water conduction model of the present invention. It divides pore water into free water, weakly bound water, and strongly bound water, while the present invention divides it into free water, micropore water, and clay water. The model parameters to be determined also include the cementation index and the saturation index.

[0093] However, compared with this comparative document, the core inventive point of the present invention is that it uses nuclear magnetic resonance logging curves and conventional logging curves to replace experimental data, avoiding the use of a large amount of experimental data (data that need to be obtained through experiments in the laboratory) as in the comparative document, thus saving huge time and economic costs.

[0094] In the method for establishing the three-water component differential parallel conduction water saturation model disclosed in the comparative document, first, multiple core wells need to be selected in the study area, core samples located in different geological intervals of each core well are collected, and petrophysical experiments are carried out on each core sample. Moreover, most importantly, the cores need to be centrifuged at multiple levels, and nuclear magnetic resonance experiments are carried out on the cores after being displaced by different centrifugal forces. The biggest difficulty in this scheme lies in the setting of the multi-level centrifugal force. Cores with different porosities and different degrees of looseness require different centrifugal forces. How to set it is a great difficulty, and the centrifugal force settings in different regions cannot be extended to another region. It is difficult to quantitatively describe issues such as how much centrifugal force, how long to centrifuge to displace free water, and the difference between strong centrifugation and weak centrifugation. Then, petrophysical experiments need to be carried out on the cores after being displaced by different centrifugal forces, and the resistivity of the cores is measured to calculate the cementation index and the saturation index. These complex core experiments increase the time cost and economic cost.

[0095] The present invention is precisely to solve the technical problem of the need for complex core experiments in the above-mentioned comparative document, using logging curves to replace core experiments. Because logging curves are continuous and cover the entire well section, and the measurement cost is low, the saturation of all wells can be calculated according to the model obtained by the present invention.

[0096] Specifically, in this embodiment, conventional logging and nuclear magnetic resonance logging are combined. On the one hand, the free fluid porosity, microcapillary porosity, and clay water porosity interpreted from nuclear magnetic resonance logging are substituted into the three-water conduction model formula represented by conventional logging data, and combined with parameters such as porosity, shale content, and irreducible water saturation interpreted from conventional logging to calculate the three-water model parameters, solving the problem that the calculation of model parameters must rely on experimental data.

[0097] On the other hand, as is well known, at least 8 data points are measured per meter during logging (one data point is measured every 0.125 meters). Therefore, for a formation of a certain thickness, the logging data all have a relatively large sample size, meeting the requirements of the large sample data for the optimization algorithm. So, in the process of parameter calculation, the optimization algorithm with multiple sets of data is used for calculation to obtain the optimal solution, which ensures the calculation accuracy to a certain extent.

[0098] It should be noted that the main purpose of the present invention is to provide a new idea and method for calculating the parameters of the triple-water conductivity model. Specifically, the calculation accuracy is affected by the actual data sample size and the accuracy of the data itself.

[0099] Furthermore, in the above step S1, according to the theory of parallel conductivity of multiple media, a triple-water conductivity model of the rock is established. According to the theory of parallel conductivity of multiple media, it is obtained that the conductive medium of the rock is composed of three parts in parallel, namely free fluid water, micropore water, and clay-bound water (hereinafter referred to as clay water).

[0100] For a completely water-saturated rock, the conductivity of the completely water-saturated rock is:

[0101] (1)

[0102] For an oil- and gas-bearing rock, only the free fluid pores contain oil and gas. Therefore, the conductivity of the oil- and gas-bearing rock is expressed as:

[0103] (2)

[0104] Free fluid water (which can be simply referred to as free water) is the water in the free fluid pores, stored in the free fluid pores, and is the water that can flow and be produced freely under normal formation pressure. In a completely water-saturated rock, the volume of free fluid water is equal to the volume of free fluid pores.

[0105] In an oil- and gas-bearing rock, a part of the free water is replaced by oil and gas; micropore water, also known as capillary-bound water, is the formation water stored in the tiny pore space and cannot flow and be produced under normal formation pressure. The volume of micropore water is equal to the volume of micro-capillary pores; clay water is a part of the water with special conductivity formed due to the cation exchange adsorption of clay and cannot flow freely. The volume of clay water is equal to the volume of clay pores.

[0106] In an oil- and gas-bearing rock, the total water saturation is the volume of the three kinds of water divided by the volume of all pores, and is expressed as:

[0107] (3)

[0108] In the above formulas, is the resistivity of a completely water - saturated rock, is the resistivity of an oil - and - gas - bearing rock, , , are the resistivity of free water, the resistivity of micropore water, and the resistivity of clay water respectively; , , are the free - fluid porosity, the micro - capillary porosity, and the clay - water porosity respectively, and in a unit volume of completely water - saturated rock, they are equal to the volume of free water, the volume of micropore water, and the volume of clay water respectively, , , are the pore - structure indices of free - fluid pores, micro - capillary pores, and clay pores respectively, also known as the cementation indices. , is the water saturation of free - fluid pores, is the free - water pore.

[0109] It should be noted that the resistivity of free water in the rock is the same as that of micropore water, and both belong to ionic conduction. The calculation method of its resistivity is mainly to directly measure the formation water resistivity by sampling the formation water or analyze the salinity of the formation water, and calculate the formation water resistivity according to the salinity. Among them, the value of the formation water resistivity is the same as the values of the free - water resistivity and the micropore - water resistivity.

[0110] Furthermore, the resistivity of clay water can be calculated based on the salinity and temperature of the formation water;

[0111] Specifically, in the above step S2, calculating the free - water resistivity , the micropore - water resistivity and the clay - water resistivity include the following steps:

[0112] Directly measure the formation water resistivity by sampling the formation water or analyze the salinity of the formation water, and calculate the formation water resistivity according to the salinity;

[0113] Calculate the conductivity of clay water based on the first operation logic , and take the reciprocal of the conductivity of clay water to calculate the resistivity of clay water ;

[0114] Among them, the formation water resistivity is the same as the free - water resistivity and the micropore - water resistivity . The first operation logic is expressed as:

[0115] (4)

[0116] Among them, is the conductivity of clay water, and its unit is (S / m), is the diffusion factor of the ion diffusion layer is the compensating ion in clay water The equivalent conductivity of, and its unit is (S / m)(mmol / L). is the cation exchange capacity of clay, which is the pore volume occupied by clay water when, and it is only related to the formation temperature.

[0117] It can be understood that for a specific formation, the formation water salinity and formation temperature are basically constant, so and can be regarded as a constant. can be calculated according to the following formula (5), calculated according to the following formula (6), calculated according to the following formula (7).

[0118] (5)

[0119] (6)

[0120] (7)

[0121] Among them, is the formation water salinity when the thickness of the clay surface diffusion layer is the minimum thickness, is the actual formation water salinity, is the formation temperature, and the unit is degree Celsius (°C).

[0122] Exemplarily, taking the formation water as water type for illustration. The formation water is water type. A total of 6 water samples are taken. The water analysis data is shown in Table 1. The average total salinity of the water samples is 31,248.5 mg / L. The average formation depth of the water samples is 2,470 m. The ground temperature is 18 °C, and the geothermal gradient is 3.41 °C / 100 m. According to the conversion calculation software of formation water salinity and formation water resistivity, the formation water resistivity is calculated to be 0.075 (Ω·m).

[0123] Table 1 Ion content and salinity of water samples Unit: mg / L

[0124]

[0125] In this embodiment, is the formation water salinity when the thickness of the diffusion layer on the clay surface is the minimum thickness, and it is 0.35 mol / cm 3 , calculated according to the Nacl solution, the equivalent salinity is 20475 mg / L, is the actual formation water salinity. According to the analysis data in Table 1, Take the average value of the equivalent Nacl salinity, which is 30386 mg / L. At this time, , so .

[0126] Both are only related to the formation temperature . The formation temperature is calculated according to the formation depth and the geothermal gradient. In this embodiment, the surface temperature is 18 °C, and the geothermal gradient is 3.41 °C / 100 m, , where H is the sampling depth point, and the unit is meter.

[0127] In step S3, according to the nuclear magnetic resonance logging response characteristics of the completely water-bearing rock, calculate the free fluid porosity , clay water porosity , and micro-capillary porosity in the three-water conductivity model. Specifically, it includes the following steps:

[0128] Determine the completely water-bearing rock according to the oil testing and production data. In the completely water-bearing rock, the volume of clay-bound water, capillary-bound water, and movable water read from the nuclear magnetic resonance logging data processing and interpretation result map are used as the clay water porosity , micro-capillary porosity , and free fluid porosity in the three-water conductivity model respectively.

[0129] In this embodiment, by making full use of nuclear magnetic resonance logging, the clay water porosity , micro-capillary porosity , and free fluid porosity can be accurately calculated.

[0130] Specifically, referring to Figure 3The nuclear magnetic resonance logging interpretation result diagram shown. In the diagram, the first - track data is the depth track, the second - track data is the lithology (logging) curve, the third - track data is the nuclear magnetic resonance standard T2 spectrum, the fourth - track data is the interval porosity distribution, the fifth - track data is the permeability analysis, which is the resistivity logging value at different detection depths and the nuclear magnetic resonance - calculated permeability, the sixth - track data is the saturation analysis, which is the water - containing saturation, total porosity, effective porosity, and capillary - bound water porosity calculated by nuclear magnetic resonance logging, the seventh - track data is the MRIAN analysis, which is the clay - bound water volume, capillary - bound water volume, and movable water volume obtained after curve filling based on the calculation results of the sixth track, and the hydrocarbon volume calculated by the differential spectrum method, and the eighth - track data is the interpretation conclusion of nuclear magnetic resonance logging.

[0131] The clay water porosity read in the present invention , micro - capillary porosity and free - fluid porosity are the data in the seventh track of the diagram, which are the clay - bound water volume, capillary - bound water volume, and movable water volume in the seventh track respectively.

[0132] Read the data of completely water - saturated rocks. Figure 3 Layers 93, 95, 96, and 97 among them are completely water - saturated rocks verified by trial production, and nuclear magnetic resonance fluid analysis also shows them as completely water - saturated rocks.

[0133] Read the depth, rock resistivity, clay water porosity , micro - capillary porosity and free - fluid porosity at different depth points within the water layer of completely water - saturated rocks. Meanwhile, according to step S2, the formation temperature , clay water conductivity can be calculated. See Table 2 below, which is a partial data example of the nuclear magnetic resonance logging calculation data points of completely water - saturated rocks.

[0134] Table 2 Partial Nuclear Magnetic Resonance Logging Calculation Data Points of Completely Water - Saturated Rocks

[0135]

[0136] Furthermore, step S4 specifically includes the following steps:

[0137] Select multiple completely water - saturated rocks, and take the clay water porosity, micro - capillary porosity, and free - fluid porosity at multiple depth points for each completely water - saturated rock on the nuclear magnetic resonance interpretation result diagram;

[0138] Determine the resistivity of each completely water - saturated rock corresponding to each of the above - mentioned depth points according to the resistivity logging curve, substitute it into the triple - water conductivity model, establish N equations, and form the first over - determined equation set;

[0139] The optimization algorithm using the least squares method is employed to solve the first overdetermined system of equations, and the cementation index is calculated. and and .

[0140] Specifically, N completely water-bearing rocks are selected. On the nuclear magnetic resonance interpretation result graph, clay water porosity, micro-capillary porosity, and free fluid porosity values at multiple depth points are taken for each completely water-bearing rock. At the same time, according to the resistivity logging curve, the resistivities corresponding to N depth points are respectively and and …… Based on this, a first overdetermined system of equations as shown in formula (8) is established.

[0141] Among them, the overdetermined system of equations has a unique least squares solution. According to the programming of the least squares method, the unknowns in this system of equations and and .

[0142] (8)

[0143] Exemplarily, in this embodiment, the data in Table 2 are substituted into the calculation formula of the conductivity of the completely water-bearing rock shown in formula (1) to obtain a first overdetermined system of equations in the form of formula (8). The optimization algorithm using the least squares method is used to solve the first overdetermined system of equations. Specifically, the method of matlab programming can be used for the solution, and finally and and are calculated.

[0144] In this embodiment, based on the free fluid porosity, micro-capillary porosity, and clay water porosity calculated from nuclear magnetic resonance logging, combined with the resistivity of the completely water-bearing rock in the conventional logging data, a large number of sample data are used to establish a system of equations and the optimization method is used to solve the parameters and and of the three-water conductivity model, avoiding the limitation of having to rely on experimental data to determine the model parameters.

[0145] Further, step S5 may include the following steps:

[0146] Calculate the conventional logging parameters of the completely water-bearing rock according to the conventional logging curve. The conventional logging parameters at least include: shale content , total porosity of the formation , permeability , irreducible water saturation ;

[0147] Based on conventional logging parameters, obtain the free fluid porosity in the triple-water conductivity model , the clay water porosity , and the micro-capillary porosity representation formulas;

[0148] Substitute the representation formulas of , , obtained based on conventional logging parameters and the cementation index calculated in step S4 , , into the representation formula of the conductivity of the completely water-saturated rock to establish a clay water volume coefficient calculation model;

[0149] Use the optimization algorithm to solve the clay water volume coefficient .

[0150] In this embodiment, using nuclear magnetic resonance logging as a constraint condition, substitute the free fluid porosity, micro-capillary porosity, and clay water porosity interpreted from nuclear magnetic resonance logging into the triple-water conductivity model formula based on conventional logging parameter data, combine with parameters such as porosity, shale content, and irreducible water saturation interpreted from conventional logging, and at the same time rely on the characteristics of the large data sample of the logging data itself. The optimization algorithm of multiple groups of data is used to assist in improving the calculation accuracy during parameter calculation, avoiding the limitation of having to rely on experimental data to determine model parameters.

[0151] Furthermore, step S5 further includes the following steps:

[0152] According to the dual-water model, obtain the clay water volume in the unit pore volume based on the cation exchange capacity ;

[0153] Obtain the ratio between the cation exchange capacity and the shale content and define it as the clay water volume coefficient ;

[0154] According to the total porosity and the clay water volume in the unit pore volume represented based on the clay water volume coefficient , obtain the representation formula of the clay water porosity ;

[0155] According to the irreducible water saturation , obtain the representation formula of the micro-capillary porosity :

[0156] According to the total porosity the clay water porosity and the microcapillary porosity to obtain the free fluid porosity .

[0157] Specifically, the shale content can be calculated according to the natural gamma curve or the spontaneous potential curve, and the calculation formula is:

[0158] (9)

[0159] In the formula, can be the shale index, which can be calculated according to the following formula (10) or (11).

[0160] (10)

[0161] (11)

[0162] Among them, 、 are the spontaneous potential and natural gamma logging values respectively, 、 are the spontaneous potential and natural gamma of pure sandstone respectively, 、 are the spontaneous potential and natural gamma of pure shale respectively, and c is the formation factor. Among them, for old formations, c = 2, and for new formations, c = 3.7.

[0163] In some embodiments, the total porosity can be calculated according to the three-porosity logging values. First, it is necessary to perform cross-plot analysis on the porosity measured from the core with the acoustic travel time, density, and neutron porosity logging values respectively to determine the logging curve with the best correlation with the core porosity, and then use the fitting formula to calculate the porosity.

[0164] In this embodiment, the cross-plot of the core porosity and the three-porosity curves is as Figures 4 to 6 , it can be seen that the core porosity has a better correlation with the density and neutron porosity. Therefore, the density and neutron porosity are combined to calculate the porosity, and using multiple regression analysis, the calculation formula for the total porosity is obtained as:

[0165] (12)

[0166] Among them, is the density logging value, with the unit g / cm 3 , is the neutron porosity log value, with the unit of %.

[0167] The above formula (12) is a fitting formula obtained based on the specific core and logging data in the embodiments. The present application does not impose any restrictions on the formula for calculating porosity. In some other embodiments, other calculation formulas can be obtained according to the available core data.

[0168] In some embodiments, referring to Figure 7 , the permeability can be obtained from the porosity-permeability crossplot of the core. The calculation formula for the permeability is:

[0169] (13)

[0170] In formula (13), is the permeability, with the unit of , is the total porosity, with the unit of % in this formula. The present application does not impose any restrictions on the calculation of permeability. In some other embodiments, other calculation formulas for permeability can also be obtained according to the core data.

[0171] It can be understood that the irreducible water saturation is generally proportional to the shale content and inversely proportional to the rock physical properties.

[0172] In some embodiments, crossplot analysis can be performed on the irreducible water saturation of the core obtained from the mercury injection experiment, and parameters such as shale content, porosity, and permeability ( Figure 8 , Figure 9 ), and the calculation formula for the irreducible water saturation can be obtained:

[0173] (14)

[0174] In the above formula (14), is the irreducible water saturation, with the unit of %, is the shale content, with the unit of decimal in the formula, is the permeability, with the unit of , is the total porosity of the formation, which is calculated in decimals in this formula.

[0175] It can be understood that the present application does not impose any restrictions on the calculation of irreducible water saturation. In some other embodiments, other calculation formulas for irreducible water saturation can also be obtained according to other data.

[0176] Step S5 further includes: calculating the free fluid porosity, clay water porosity, and micropore porosity in the completely water-saturated rock according to conventional logging parameters, and the calculation formulas thereof. , clay water porosity , micropore porosity .

[0177] Specifically, according to the clay water volume formula in the dual-water conductivity model, the clay water volume in the unit pore volume is expressed as:

[0178] (15)

[0179] In the formula, , have the same meanings as in formula (4), and the calculation methods refer to formula (5) and formula (6). is the cation exchange capacity, which is proportional to the shale content , where .

[0180] For a formation with a total porosity of , the clay water porosity can be expressed as:

[0181] (16)

[0182] Among them, is the total porosity of the formation, which can be calculated from the conventional logging curves such as neutron, density, or acoustic travel time disclosed in the foregoing embodiments. is the shale content, which can be calculated from the spontaneous potential or natural gamma curve disclosed in the foregoing embodiments. The coefficient is the unknown to be solved in formula (16), and can be named the clay water volume coefficient.

[0183] It should be noted that both the clay water and micropore water in the formation belong to the bound water, and the volume of the micropore water can be calculated by subtracting the clay water volume from the total bound water volume of the rock.

[0184] Therefore, the micropore porosity is expressed as:

[0185] (17)

[0186] Among them, the formation bound water saturation can be obtained from the core data calculated in the foregoing embodiments.

[0187] It should be noted that the core data mentioned in this article basically only includes the most basic experiments such as porosity and permeability, and they are not necessary conditions. The logging curves can also be used for calculation.

[0188] Free fluid porosity It is equal to the total porosity of the rock minus the porosity of all the irreducible water (including clay water and micropore water):

[0189] (18)

[0190] Furthermore, substitute the calculation formulas of , , obtained based on conventional logging parameters in step S5, and , , calculated according to nuclear magnetic resonance and the optimization algorithm in step S4 into the representation formula of the conductivity of a completely water-saturated rock (triple-water conductivity model) to realize the constraint of nuclear magnetic resonance on conventional logging, and obtain a calculation model of the clay water volume coefficient based on conventional logging:

[0191] (19)

[0192] In this embodiment, according to the idea of constraining conventional logging by nuclear magnetic resonance, take the same set of data points as in formula (8), and calculate the total porosity, permeability, shale content, and irreducible water saturation at each depth point according to the corresponding depth.

[0193] Calculate according to step S2 , and the resistivity of clay water and the resistivity of formation water , and use the data points of the same well section and depth as in step S3 to obtain the data in Table 3.

[0194] Substitute the data points in Table 3 and , , calculated from nuclear magnetic logging data in step S4 into formula (19) to obtain a system of equations for the calculation model of the clay water volume coefficient expressed by conventional logging parameters, and calculate the coefficients using the least squares method. In this embodiment, the solution is implemented through matlab programming to obtain .

[0195] Table 3 Conventional logging parameter table of a completely water-saturated rock (partial)

[0196]

[0197] In some embodiments, the calculation of the free water saturation index in step S6 includes the following steps:

[0198] Based on the experimental data of oil-bearing cores, the water saturation and resistivity of different oil-bearing cores are obtained;

[0199] Calculate the free fluid pore water saturation according to the water saturation ;

[0200] Substitute the different resistivities and the free fluid pore water saturation into the saturation exponent calculation model to obtain a third overdetermined system of equations;

[0201] Solve the third overdetermined system of equations according to the optimization algorithm to calculate the free water saturation exponent .

[0202] It can be understood that the water saturation of the oil-bearing core is the total water saturation. If the core is a sealed core, the experimentally measured water saturation and core resistivity are directly used. If the core is an unsealed core, the experimentally measured water saturation needs to be corrected for volatilization, and the core resistivity is obtained according to the conventional logging curve.

[0203] In this embodiment, after correcting the oil saturation and water saturation of the core for volatilization and then performing core depth alignment, the conventional logging curve values such as natural gamma, three porosities, resistivity, etc. corresponding to each core are obtained. Calculate the corresponding conventional logging parameters according to the method in step 5, and calculate the free fluid pore water saturation according to the total water saturation of the core using formula (3) to obtain the data in Table 4.

[0204] Furthermore, in the above step S6, the establishment of the saturation exponent calculation model includes the following steps:

[0205] Perform depth correction on the taken oil-bearing cores to obtain the conventional logging curves corresponding to the depths of each oil-bearing core;

[0206] Calculate the conventional logging parameters based on the conventional logging curves. The conventional logging parameters at least include: total porosity shale content , permeability , irreducible water saturation ;

[0207] Obtain the expression formulas of free fluid porosity , clay water porosity , and microcapillary porosity in the triple water conductivity model according to the conventional logging parameters;

[0208] Substitute the obtained based on the conventional logging parameters , , The expression formula and the cementation index calculated in step S4 、 、 and the clay water volume coefficient calculated in step S5 , substitute them into the calculation formula of the conductivity of the oil-bearing rock, and establish the following formula (20) saturation index calculation model:

[0209] (20)

[0210] Specifically, substitute the data in Table 4 into the saturation index calculation model characterized by formula (20), and the third overdetermined equation set of the three-water conductivity model of the oil-bearing rock can be obtained. Use the optimization algorithm of the least square method to calculate the free water saturation index . In this embodiment, it is solved by matlab programming to obtain .

[0211] Table 4 Conventional logging data of oil-bearing cores (partial)

[0212]

[0213] Step S7 can obtain the calculation formula of the water saturation according to the various models established and the various parameters calculated in steps S1 to S6, which may include the following steps:

[0214] According to the saturation index calculation model, obtain the calculation formula of the free fluid pore water saturation ;

[0215] Substitute the calculated cementation index 、 、 , the clay water volume coefficient and the free water saturation index into the calculation formula of ;

[0216] Calculate the conventional logging parameters according to the conventional logging curves, and convert the into the water saturation of the total pores based on the conventional logging parameters, and calculate the water saturation .

[0217] Specifically, according to the saturation index calculation model, the calculation formula of the free fluid pore water saturation is:

[0218] (21)

[0219] Calculate the free fluid pore water saturation , and convert it into the water saturation of total pores according to the following formula (22) based on conventional logging parameters :

[0220] (22)

[0221] Specifically, the , , , and calculated in steps S4 - S6, as well as the conventional logging parameters calculated from the conventional logging curves: total porosity shale content , irreducible water saturation and resistivity logging value are substituted into formula (21) to calculate the free - fluid pore water saturation of all reservoirs in the whole well.

[0222] Convert the free - fluid pore water saturation into the water saturation of total pores to achieve the identification of oil - gas layers and the quantitative calculation of oil - gas reserves.

[0223] In this embodiment, the total water saturation is calculated according to the above method, and the oil saturation is obtained therefrom, and a curve is plotted, as shown in Figure 10 . Figure 10 Among them, the first track is the lithology logging curve track (including spontaneous potential SP, natural gamma GR and caliper curve ), the second track is the porosity logging curve track (including density curve and acoustic travel - time curve AC), the third track is the array induction curve, the fourth track is the depth track, the fifth track is the logging lithology profile, the sixth track is the shale content and porosity calculated from conventional logging, the seventh track is the nuclear magnetic resonance logging interpretation result, the green filling is the clay water volume, the gray cross - hatched filling is the micro - capillary water volume, the blue filling is the movable water volume, the eighth track is the total water saturation and oil saturation calculated according to the triple - water conductivity model, the blue filling represents the movable water saturation in the total pores, and the red filling represents the oil saturation in the total pores. The ninth track is the test layer, and several test layers in the figure are all oil - water layers. The thirteenth track is the clay water, micropore water and free water volumes calculated according to the triple - water conductivity model, and the filling type is the same as that of the seventh track.

[0224] Continuing to refer to Figure 10 , the 10th track is the total water saturation interpreted by nuclear magnetic resonance logging, the 11th track is the water saturation calculated using the parallel conductivity formula for shaly sandstone, and the 12th track is the water saturation calculated using Archie's formula. Archie's formula is the most commonly used formula for calculating water saturation in conventional shaly sandstone reservoirs, and the formula is as follows:

[0225] (23)

[0226] Among them, in formula (23), is the water saturation, with the unit of decimal unit and can be converted to %; is the formation water resistivity, with the unit of ohm-meter (Ω·m); is the formation resistivity (resistivity of oil-bearing and gas-bearing rocks), with the unit of ohm-meter (Ω·m); a and b are lithology coefficients, generally both taken as 1; m is the cementation exponent, n is the saturation exponent, and m and n are obtained from litho-electric data or taken as empirical coefficient 2.

[0227] For formations with more shale, the shale sandstone parallel conduction formula is also often used to calculate the water saturation, and the formula is as follows:

[0228] (24)

[0229] Among them, in formula (24), is the water saturation, with the unit of decimal unit and can be converted to %; is the formation water resistivity, with the unit of ohm-meter; is the formation resistivity, with the unit of ohm-meter; a and b are lithology coefficients, generally both taken as 1; m is the cementation exponent, n is the saturation exponent, and m and n are obtained from litho-electric data or taken as empirical coefficient 2; is the shale content, and the decimal unit is used during calculation; is the resistivity of shale, with the unit of ohm-meter.

[0230] From Figure 10 it can be seen that for several test layers in this layer section, the oil saturation calculated by the triple-water conduction model is distributed between 30% and 80%, the water saturation is distributed between 20% and 70%, and there is a certain amount of mobile water, belonging to the oil-water coexisting layer, which is consistent with the test results.

[0231] Specifically, according to the data in channels 8, 10, 11, and 12 in the figure, it can be seen that the water saturation calculated by this method (channel 8 curve) has a higher degree of conformity with the water saturation interpreted by nuclear magnetic resonance (channel 10). As the most advanced and high-precision logging method currently, the interpretation result of nuclear magnetic resonance is considered to be the most consistent with the actual formation. The coincidence rates of the calculation results of the existing Archie formula and the shale sandstone parallel conduction formula with the nuclear magnetic resonance water saturation are lower than the calculation results of this method.

[0232] Figure 10 The saturation calculation results of some oil-bearing layers in Relative error with nuclear magnetic resonance water saturation (Water saturation interpreted by nuclear magnetic resonance). The specific calculation method is (water saturation of the triple-water model - nuclear magnetic resonance water saturation) / nuclear magnetic resonance water saturation * 100%. "Relative error 2" is the water saturation calculated by Archie's formula Relative error with nuclear magnetic resonance water saturation The calculation method is the same as above. "Relative error 3" is the water saturation calculated by the parallel conductivity formula for shaly sandstone Relative error with nuclear magnetic resonance water saturation As can also be seen from the data in Table 5, the overall relative error of the calculation results of this method is the smallest

[0233] Table 5 Analysis data table of calculation results (partial)

[0234]

[0235] It should be noted that the main purpose of the present invention is to provide an innovative idea and specific method. In the case of lack of experimental data, with the aid of nuclear magnetic resonance and optimization algorithms to calculate water saturation, the accuracy of the calculation results depends on the data situation. When using the optimization algorithm to solve the model parameters, the accuracy of the calculation results is closely related to the selected data points and the amount of data

[0236] The calculation method of the triple-water conductivity model parameters based on nuclear magnetic resonance constrained conventional logging provided by the present invention makes full use of the advantages of nuclear magnetic resonance logging in accurately calculating free fluid porosity, microcapillary porosity and clay water porosity. By using nuclear magnetic resonance constrained conventional logging and establishing equations with a large number of sample data and solving them by optimization methods, on the one hand, it avoids the limitation of having to rely entirely on experimental data to determine model parameters, and on the other hand, relying on the constraints of nuclear magnetic resonance logging and optimization algorithms, it improves the calculation accuracy of model parameters, thus calculating the water saturation of the reservoir more accurately. The present invention effectively solves the limitation of having to rely on a large number of experimental data such as mercury injection, rock electricity experiment, clay analysis, cation exchange capacity, etc. to determine the parameters of the triple-water conductivity model. In the case of lack of experimental data, relatively accurate model parameters can still be obtained, improving the calculation accuracy of the water saturation of complex reservoirs

[0237] The above are only the preferred embodiments of the present invention, and are not limitations on the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention

Claims

1. A method for calculating parameters of three-water conductive model based on conventional logging constrained by nuclear magnetic resonance, characterized in that: The following steps are involved: Step S1, establishing a three-water conductive model of rock based on the multi-medium parallel conductive theory, and obtaining a calculation formula for the conductivity of completely water-containing rock and oil and gas-containing rock; Step S2: Calculate the free water resistivity for the three-water conductive model of fully water-bearing rock and oil- and gas-bearing rock , micropore water resistivity and clay water resistivity ; Step S3: Calculate the free fluid porosity in the three-water conductive model based on the nuclear magnetic resonance logging response characteristics of the fully water-bearing rock. , Clay water porosity , microcapillary porosity ; Step S4: calculate the water content of the plurality of fully water-bearing rocks based on nuclear magnetic resonance logging. , , , substitute the three-water conductive model to establish the first overdetermined equation group, and apply the optimization algorithm to iteratively solve it to calculate the cementation index of free water , cementation index of micropore water and the cementation index of clay water ; Step S5, using nuclear magnetic resonance logging to constrain conventional logging curves: Calculate the conventional logging parameters of the completely water-bearing rock according to the conventional logging curve; Cation exchange capacity The mud content The ratio between the two is defined as the clay water volume coefficient ; According to the conductivity of the completely water-containing rock, a clay water volume coefficient calculation model of the completely water-containing rock based on the conventional logging parameters is established, and the cementation index calculated based on the nuclear magnetic resonance logging in step S4 is calculated. , , Calculate the clay water volume coefficient ; Step S6: Establish a saturation index calculation model for oil and gas-bearing rocks based on conventional logging parameters according to the electrical conductivity of the oil and gas-bearing rocks, and calculate the free water saturation index according to the saturation data of the oil-bearing core. ; Step S7: Calculate the cementation index according to the saturation index calculation model and calculation , , , the clay water volume coefficient and the free water saturation index , using conventional logging curves to calculate water saturation .

2. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 1, characterized in that: The conductivity of the fully hydrated rock for: （1） The electrical conductivity of the oil and gas bearing rock It is expressed as: （2） in, is the resistivity of the completely hydrated rock, is the resistivity of the oil and gas bearing rock, , is the free fluid pore water saturation, Free water pores.

3. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 1, characterized in that: The step S2 comprises the following steps: Directly measuring the resistivity of formation water according to formation water sampling or performing mineralization analysis on the formation water and calculating the resistivity of the formation water according to the mineralization; Calculation of clay water conductivity based on the first operation logic , and according to the clay water conductivity Calculate the clay water resistivity ; Wherein, the formation water resistivity The free water resistivity , the micropore water resistivity The value of is the same, the first operation logic is expressed as: in, for The diffusion factor of the ion diffusion layer, Compensating ions for clay water The equivalent conductivity of The cation exchange capacity of clay is The pore volume occupied by water in clay.

4. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 1, characterized in that: The step S3 comprises the following steps: The completely water-bearing rock is determined according to the test oil and production data, and the clay bound water volume, capillary bound water volume and movable water volume in the nuclear magnetic resonance logging data processing and interpretation result map are used as the clay water porosity in the three-water conductive model. , the microcapillary porosity and the free fluid porosity .

5. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 1, characterized in that: The step S4 comprises the following steps: Selecting a plurality of said completely water-bearing rocks, and obtaining clay water porosity, microcapillary porosity and free fluid porosity at a plurality of depth points for each of said completely water-bearing rocks on a nuclear magnetic resonance interpretation result map; Determine the resistivity of the completely water-bearing rock corresponding to each of the depth points according to the resistivity logging curve, and establish N equations to form the first overdetermined equation group; The optimization algorithm of the least square method is used to solve the first overdetermined equations to calculate the cementation index. , , .

6. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 1, characterized in that: The step S5 comprises the following steps: The conventional logging parameters of the completely water-bearing rock are calculated according to the conventional logging curve, and the conventional logging parameters at least include: , the total porosity of the formation , Permeability , Irreducible water saturation ; According to the conventional logging parameters, the free fluid porosity in the three-water conductive model is obtained. , Clay water porosity , microcapillary porosity The expression formula of ; The conventional logging parameters are used to obtain , , The expression formula and the cementation index calculated in step S4 , , , bring in the conductivity expression formula of the completely water-containing rock, and establish the calculation model of the clay water volume coefficient; The clay water volume coefficient is solved by using an optimization algorithm .

7. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 6, characterized in that: The step S5 further comprises the following steps: According to the total porosity And based on the clay water volume coefficient The volume of clay water per unit pore volume , the clay water porosity is obtained The expression formula of ; According to the irreducible water saturation , the microcapillary porosity is obtained The expression formula is: According to the total porosity , the clay water porosity With the microcapillary porosity , obtain the free fluid porosity .

8. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 1, characterized in that: The free water saturation index The calculation of includes the following steps: According to the experimental data of oil-bearing cores, the water saturation and resistivity of different oil-bearing cores are obtained; Based on the water saturation, calculate the free fluid pore water saturation ; The different resistivities and free fluid pore water saturation Substitute into the saturation index calculation model to obtain a third overdetermined equation group; The free water saturation index is calculated by solving the third overdetermined equations according to the optimization algorithm. .

9. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 7, characterized in that: The establishment of the saturation index calculation model comprises the following steps: Performing depth correction on the oil-bearing cores obtained to obtain a conventional logging curve corresponding to the depth of each oil-bearing core; The conventional logging parameters are calculated based on the conventional logging curve, and the conventional logging parameters at least include: total porosity , mud content , Permeability , Irreducible water saturation ; According to the conventional logging parameters, the free fluid porosity in the three-water conductive model is obtained. , Clay water porosity , microcapillary porosity The expression formula of ; The conventional logging parameters are used to obtain , , The expression formula and the cementation index calculated in step S4 , , , bring into the calculation formula of the electrical conductivity of the oil and gas bearing rock, and establish a saturation index calculation model.

10. The method for calculating parameters of the three-water conductive model based on conventional well logging constrained by nuclear magnetic resonance according to claim 1, characterized in that: The water saturation The calculation of includes the following steps: According to the saturation index calculation model, the free fluid pore water saturation is obtained. The calculation formula of The calculated cementation index , , , the clay water volume coefficient and the free water saturation index , substitute the The calculation formula of Calculate conventional logging parameters according to the conventional logging curve, and convert the Convert to total pore water saturation and calculate water saturation .

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