Method and system for researching saturation model of ancient oil reservoir

Abstract

The invention provides a paleo-reservoir saturation model research method and system, and the method comprises the steps: carrying out the fitting of a displacement-imbibition capillary pressure mathematical model to determine an original saturation mathematical model of a paleo-reservoir, selecting different paleo-free water interfaces, and determining a current saturation mathematical model of the paleo-reservoir according to the original saturation mathematical model of the paleo-reservoir; determining an adaptive ancient free water interface according to an error value between the current saturation mathematical model of the ancient reservoir and the well logging interpretation water saturation; the current free water interface is adjusted, and the ancient free water interface and the ancient oil reservoir current saturation mathematical model are adapted to obtain a water saturation interpretation model; and applying the water saturation interpretation model to a three-dimensional geologic model to obtain a three-dimensional water saturation model. On the basis of reflecting the characteristic that the water saturation of the conventional oil layer changes along with the change of the oil column height and the reservoir physical property, accurate characterization of the residual oil saturation of the ancient oil reservoir can be formed, the resource potential is defined, and the development basis is tamped.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas field development, and in particular relates to a paleo-oil reservoir saturation model research method and system. Background Art

[0002] A 3D geological model is a key component of reservoir characterization, integrating all insights gained from various reservoir studies. Saturation models depict the fluid distribution within a reservoir, serve as a fundamental parameter for reserve calculations, determine reservoir development potential, and are a key component of geological research for oil and gas field development.

[0003] Existing saturation model research methods mainly include three-dimensional model interpolation and saturation height function methods. The three-dimensional model interpolation method directly uses water saturation logging interpretation as basic data and uses geostatistical methods to perform three-dimensional spatial interpolation to obtain the saturation field. This method is difficult to reflect the characteristics of saturation changing with changes in oil column height and reservoir properties, and it cannot spatially constrain it according to structural height, which can easily lead to confusion in the understanding of oil and water distribution. Although the saturation height function method can reflect the characteristics of saturation changing with changes in oil column height and reservoir properties, it cannot characterize the saturation characteristics of residual oil in ancient reservoirs, resulting in an underestimation of the free water interface and an overestimation of reservoir potential, thereby introducing greater uncertainty. Summary of the Invention

[0004] In response to the above problems, the present invention proposes a method for studying a paleo-oil reservoir saturation model, which includes:

[0005] The mathematical model of the original saturation of the ancient reservoir is determined by fitting the mathematical model of displacement-imbibition capillary pressure, and the mathematical model of the current saturation of the ancient reservoir is determined based on the mathematical model of the original saturation of the ancient reservoir by selecting different ancient free water interfaces.

[0006] According to the error value of the mathematical model of the present saturation of the ancient oil reservoir and the water saturation interpreted by well logging, the appropriate ancient free water interface is determined;

[0007] Adjust the present free water interface, adapt the ancient free water interface and the present saturation mathematical model of the ancient oil reservoir to obtain the water saturation interpretation model;

[0008] The water saturation interpretation model is applied to the three-dimensional geological model to obtain a three-dimensional water saturation model.

[0009] Furthermore, the fitting of the displacement-imbibition capillary pressure mathematical model includes:

[0010] Determine the structural-reservoir evolution history and the displacement-imbibition process experienced by the reservoir based on the structural-reservoir evolution history;

[0011] According to the displacement-imbibition process, the displacement-imbibition curve of the typical reservoir boundary and the scanning curve of imbibition start at different selected oil saturations are determined;

[0012] A displacement-imbibition capillary pressure mathematical model is determined, and parameter fitting is performed on the displacement-imbibition curve and the scanning curve according to the mathematical model to determine the displacement-imbibition capillary pressure mathematical model fitting.

[0013] Furthermore, the reservoir data includes core data, well logging data, oil test data and pressure gradient.

[0014] Furthermore, the typical reservoir boundary displacement-imbibition curve and the scanning curve for imbibition onset at different selected oil saturations are determined, including:

[0015] determining typical reservoir characteristic samples, and conducting displacement-imbibition experiments on the typical reservoir characteristic samples according to the displacement-imbibition process;

[0016] Determining displacement-imbibition capillary pressure characteristics under reservoir wettability conditions based on the displacement-imbibition experiment;

[0017] Based on the displacement-imbibition capillary pressure characteristics, the typical reservoir boundary displacement-imbibition curve and the scanning curve for the onset of imbibition at different selected oil saturations are determined.

[0018] Further, according to the sampling conditions, the reservoir samples are selected from the entire reservoir; or,

[0019] Typical reservoir characteristic samples were selected according to sedimentary facies type and rock type.

[0020] Furthermore, the mathematical model for determining the present saturation of the ancient oil reservoir includes:

[0021] Determine the mathematical model of the original saturation of the ancient reservoir based on the mathematical model of the ancient free water interface and displacement capillary pressure;

[0022] Determine the present capillary pressure field based on the present free water interface;

[0023] The mathematical model of the current saturation of the ancient oil reservoir under the current capillary pressure field is determined based on the mathematical model of the imbibition capillary pressure.

[0024] The present invention also provides a paleo-reservoir saturation model research system, which includes a first determination unit, a paleo-interface determination unit, a second determination unit, and a three-dimensional model determination unit, wherein:

[0025] The first determination unit is used to determine the original saturation mathematical model of the ancient oil reservoir based on the displacement-imbibition capillary pressure mathematical model, select different ancient free water interfaces and determine the current saturation mathematical model of the ancient oil reservoir based on the original saturation mathematical model of the ancient oil reservoir;

[0026] The paleointerface determination unit is used to determine the appropriate paleofree water interface based on the mathematical model of the present saturation of the paleo-oil reservoir and the error value of the water saturation interpreted by well logging;

[0027] The second determination unit is used to adjust the present free water interface, adapt the ancient free water interface and the present saturation mathematical model of the ancient oil reservoir, and obtain the water saturation interpretation model;

[0028] The three-dimensional model determination unit is used to apply the water saturation interpretation model to the three-dimensional geological model to obtain a three-dimensional water saturation model.

[0029] Specifically, the system further includes a third determination unit, a curve determination unit and a fitting determination unit.

[0030] The third determination unit is used to determine the structural-reservoir evolution history and determine the displacement-imbibition process experienced by the reservoir based on the structural-reservoir evolution history;

[0031] a curve determination unit for determining a typical reservoir boundary displacement-imbibition curve and a scanning curve for imbibition start at different selected oil saturations according to the displacement-imbibition process;

[0032] The fitting determination unit is used to determine the displacement-imbibition capillary pressure mathematical model, perform parameter fitting on the displacement-imbibition curve and the scanning curve according to the mathematical model, and determine the displacement-imbibition capillary pressure mathematical model fitting.

[0033] Specifically, the curve determination unit includes a sample determination module, a first determination module and a curve determination module.

[0034] A sample determination module is used to determine typical reservoir characteristic samples and perform a displacement-imbibition experiment on the typical reservoir characteristic samples according to the displacement-imbibition process;

[0035] A first determination module is configured to determine displacement-imbibition capillary pressure characteristics under reservoir wettability conditions based on the displacement-imbibition experiment;

[0036] The curve determination module is used to determine the typical reservoir boundary displacement-imbibition curve and the scanning curve for starting imbibition at different selected oil saturations based on the displacement-imbibition capillary pressure characteristics.

[0037] Specifically, the first determining unit includes a second determining module, a pressure field determining module and a third determining module.

[0038] The second determination module is used to determine the mathematical model of the original saturation of the ancient oil reservoir based on the mathematical model of the ancient free water interface and the displacement capillary pressure;

[0039] A pressure field determination module, used to determine the current capillary pressure field based on the current free water interface;

[0040] The third determination module is used to determine the current saturation mathematical model of the ancient oil reservoir under the current capillary pressure field based on the imbibition capillary pressure mathematical model.

[0041] The paleo-reservoir saturation model research method and system of the present invention, based on the characteristics that the water saturation of conventional oil layers changes with the changes in oil column height and reservoir physical properties, can form an accurate representation of the residual oil saturation of paleo-reservoirs, clarify the resource potential, and lay a solid foundation for development; at the same time, it can clearly define the residual oil distribution area between the current free water surface and the ancient free water surface, and clearly distinguish it from conventional oil layers. Based on this, different development methods can be adopted respectively, which can reduce development risks.

[0042] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 A schematic flow chart of a method for studying a paleo-oil reservoir saturation model in an embodiment of the present invention is shown;

[0045] Figure 2 A schematic diagram of determining the current free water surface according to the pressure gradient in an embodiment of the present invention is shown;

[0046] Figure 3 The process of calculating the current free water interface according to the pressure gradient in an embodiment of the present invention is shown;

[0047] Figure 4 A schematic diagram showing the fitting results of residual oil-water saturation in a paleo-oil reservoir in an embodiment of the present invention is shown;

[0048] Figure 5 A schematic cross-sectional view of a three-dimensional water saturation model in an embodiment of the present invention is shown;

[0049] Figure 6 FIG. 4 shows a schematic diagram of the structure of a paleo-oil reservoir saturation model research system in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0051] The present invention provides a method for studying the saturation model of a paleo-oil reservoir. Figure 1 The figure shows a flow chart of the paleo-oil reservoir saturation model research method in an embodiment of the present invention. Figure 1 The method includes: determining the mathematical model of the original saturation of the ancient oil reservoir according to the mathematical model of displacement-imbibition capillary pressure, selecting different ancient free water interfaces and determining the mathematical model of the present saturation of the ancient oil reservoir according to the mathematical model of the original saturation of the ancient oil reservoir; determining the adapted ancient free water interface according to the error value between the mathematical model of the present saturation of the ancient oil reservoir and the water saturation interpreted by well logging; adjusting the present free water interface, adapting the ancient free water interface and the mathematical model of the present saturation of the ancient oil reservoir to obtain a water saturation interpretation model; and applying the water saturation interpretation model to the three-dimensional geological model to obtain a three-dimensional water saturation model.

[0052] Specifically, determining the fitting of the mathematical model of displacement-imbibition capillary pressure includes: determining the structural-reservoir evolution history, and determining the displacement-imbibition process experienced by the reservoir according to the structural-reservoir evolution history; determining the typical reservoir boundary displacement-imbibition curve and the scanning curve for starting imbibition at different selected oil saturations according to the displacement-imbibition process; determining the mathematical model of displacement-imbibition capillary pressure, and performing parameter fitting on the displacement-imbibition curve and the scanning curve according to the mathematical model to determine the fitting of the mathematical model of displacement-imbibition capillary pressure.

[0053] Specifically, the reservoir data includes core data, well logging data, oil test data and pressure gradient.

[0054] Specifically, determining the displacement-imbibition curve of a typical reservoir boundary and the scanning curve for imbibition to begin at different selected oil saturations includes: determining a typical reservoir characteristic sample, and performing a displacement-imbibition experiment on the typical reservoir characteristic sample according to a displacement-imbibition process; determining a displacement-imbibition capillary pressure characteristic under reservoir wettability according to the displacement-imbibition experiment; and determining a typical reservoir boundary displacement-imbibition curve and a scanning curve for imbibition to begin at different selected oil saturations according to the displacement-imbibition capillary pressure characteristic.

[0055] Specifically, according to the sampling conditions, the reservoir samples are selected from the entire reservoir; or,

[0056] Typical reservoir characteristic samples were selected according to sedimentary facies type and rock type.

[0057] Specifically, the mathematical model for determining the present saturation of ancient oil reservoirs includes:

[0058] Determine the mathematical model of the original saturation of the ancient reservoir based on the mathematical model of the ancient free water interface and displacement capillary pressure;

[0059] Determine the present capillary pressure field based on the present free water interface;

[0060] The mathematical model of the current saturation of the ancient oil reservoir under the current capillary pressure field is determined based on the mathematical model of the imbibition capillary pressure. In the embodiment of the present invention, the process of the ancient oil reservoir saturation model research method is also specifically described, and a saturation model is established for a carbonate reservoir with residual oil in a certain ancient oil reservoir:

[0061] In the embodiment of the present invention, the ancient oil reservoir refers to the oil reservoir developed in the geological history period, which was destroyed by tectonic movement in the later period. The oil reservoir part is below the current free water interface, and the part above the current free water interface is a conventional oil reservoir.

[0062] Step S101: Based on well data, seismic data, and geochemical data, perform structural evolution analysis and reservoir formation history analysis, clarify the relationship between the two, establish a structural-reservoir formation evolution history, and clarify the displacement-imbibition process experienced by the reservoir;

[0063] In the embodiment of the present invention, the structural-reservoir evolution history includes analyzing the formation and destruction process of each phase of the reservoir based on the structural evolution history and the reservoir formation history, and clarifying all the evolution processes of the reservoir since the initial accumulation.

[0064] In the embodiments of the present invention, the displacement-imbibition process experienced by the reservoir is also specifically described. The reservoir has undergone one oil and gas injection (displacement process) in geological history. Subsequently, with the development of faults, the reservoir was destroyed, the lower part of the reservoir was washed by water, and the imbibition process occurred. Therefore, the reservoir has undergone one displacement and one imbibition process to date.

[0065] Step S102: Select typical reservoir characteristic samples according to the displacement-imbibition process to simulate the actual process, conduct displacement-imbibition experiments, clarify the displacement and imbibition capillary pressure characteristics of the entire process under reservoir wettability conditions, obtain typical reservoir boundary displacement-imbibition curves, and scanning curves for the onset of imbibition at selected different oil saturations;

[0066] Specifically, in the embodiment of the present invention, typical reservoir characteristic samples can be selected according to sampling conditions, and typical samples can be selected from the entire reservoir. If conditions permit, samples can be selected for each sedimentary facies type or rock type.

[0067] In the embodiment of the present invention, the imbibition scanning curves at oil saturation of 80%, 60%, 40%, and 15% are selected, as shown in FIG. Figure 2 As shown in the figure, the horizontal axis is water saturation, the vertical axis is capillary pressure, the curves with thicker black lines are the displacement (upper thick curve) and imbibition curve (lower thick curve) of the boundary, and the series of line curves between the two curves represent the capillary pressure curves of the displacement process and the capillary pressure curves when the imbibition process starts at different water saturations.

[0068] Step S103: determining a displacement-imbibition capillary pressure mathematical model, performing parameter fitting on the displacement-imbibition curve and the scanning curve according to the mathematical model, and describing the capillary pressure mathematical model and the scanning curve of the displacement and imbibition process;

[0069] Figure 3 FIG. 4 shows a process of calculating the current free water interface according to the pressure gradient in an embodiment of the present invention. Figure 3 In the figure, the horizontal axis represents pressure / psi and the vertical axis represents depth / ft. Based on the pressure gradient difference between the oil layer and the water layer, the free water surface is obtained at the inflection point of the pressure curve.

[0070] In the embodiment of the present invention, the displacement-imbibition capillary pressure mathematical model is selected as the Van Genuchen formula. It should be noted that the selection of the displacement-imbibition capillary pressure mathematical model in the embodiment of the present invention is only an example. Without departing from the technical concept of the present invention, the selection of only the type of displacement-imbibition capillary pressure mathematical model is also within the scope of protection of the present invention.

[0071] Step S104: Determine the present free water surface based on the core data, well logging data, oil test data, and pressure gradient; determine the paleo-reservoir saturation mathematical model based on the displacement-imbibition capillary pressure mathematical model; use a trial-and-error method to select different paleo-free water interfaces and determine the model water saturation based on the paleo-reservoir saturation mathematical model; and determine the matching paleo-free water interface based on the error between the model water saturation and the well logging interpreted water saturation, when the error is minimized compared to the well logging interpreted water saturation.

[0072] In the embodiment of the present invention, the current methods for obtaining the free water interface mainly include three types: the pressure gradient method, which obtains the free water surface at the inflection point of the pressure curve based on the pressure gradient difference between the oil layer and the water layer; the best fit method, which determines the free water interface based on the best interface that meets the saturation and saturation height model results of the well logging interpretation; the oil-water interface method, which determines the lowest depth of the oil layer and the highest depth of the water layer based on core and oil test data to determine the oil-water interface, and then calculates the oil and gas starting filling height based on the main reservoir type near the fluid interface. The oil-water interface minus the oil and gas starting filling height is the free water interface.

[0073] Step S105: Fine-tune and optimize the mathematical model for solving the present-day saturation of the ancient oil reservoir, the ancient free water interface, the present-day free water surface, etc., and continuously adjust the above three conditions to minimize the error of the logging interpretation saturation and saturation height model results and achieve the best agreement with the logging curve to obtain the final water saturation interpretation model;

[0074] In the embodiment of the present invention, the depth at which the error is minimum is obtained, and the error is less than 10%. In the embodiment of the present invention, the value of the error is only an example.

[0075] Figure 4 Schematic diagram showing the fitting results of residual oil-water saturation in the ancient oil reservoir in the embodiment of the present invention, Figure 4 The figure describes the interpretation results of the ancient oil reservoir water saturation of Well A. The figure contains three curves. The left figure is the well logging curve. In the embodiment of the present invention, the porosity curve is used. The right figure shows the saturation of the imbibition model and the saturation interpreted by the well logging. The current free water surface is located at a depth of about 1075m, and the ancient free water interface is located at a depth of about 1195m. By adjusting the mathematical model for solving the ancient oil reservoir saturation, the ancient free water interface, and the current free water surface, the saturation curves of the imbibition model and the well logging interpretation are infinitely close to the porosity curve.

[0076] Step S106: Apply the interpretation model directly to the 3D geological model to obtain a 3D water saturation model. This model can reflect the characteristics of the residual oil in the reservoir, mainly the residual oil developed below the current oil-water interface and above the ancient oil-water interface.

[0077] Figure 5 : shows a schematic cross-sectional view of a three-dimensional water saturation model in an embodiment of the present invention, Figure 5 In the middle, the oil saturation is highest between the present free water surface and the ancient free water interface and interface.

[0078] The present invention also provides a paleo-reservoir saturation model research system. Figure 6 FIG. 1 shows a schematic diagram of the structure of a paleo-oil reservoir saturation model research system in an embodiment of the present invention. Figure 6 In the system, the system includes a first determination unit, a paleo-interface determination unit, a second determination unit, and a three-dimensional model determination unit, wherein:

[0079] The first determination unit is used to determine the original saturation mathematical model of the ancient oil reservoir based on the displacement-imbibition capillary pressure mathematical model, select different ancient free water interfaces and determine the current saturation mathematical model of the ancient oil reservoir based on the original saturation mathematical model of the ancient oil reservoir;

[0080] The paleointerface determination unit is used to determine the appropriate paleofree water interface based on the mathematical model of the present saturation of the paleo-oil reservoir and the error value of the water saturation interpreted by well logging;

[0081] The second determination unit is used to adjust the present free water interface, adapt the ancient free water interface and the present saturation mathematical model of the ancient oil reservoir, and obtain the water saturation interpretation model;

[0082] The three-dimensional model determination unit is used to apply the water saturation interpretation model to the three-dimensional geological model to obtain a three-dimensional water saturation model.

[0083] Specifically, the system further includes a third determination unit, a curve determination unit and a fitting determination unit.

[0084] The third determination unit is used to determine the structural-reservoir evolution history and determine the displacement-imbibition process experienced by the reservoir based on the structural-reservoir evolution history;

[0085] a curve determination unit for determining a typical reservoir boundary displacement-imbibition curve and a scanning curve for imbibition start at different selected oil saturations according to the displacement-imbibition process;

[0086] The fitting determination unit is used to determine the displacement-imbibition capillary pressure mathematical model, perform parameter fitting on the displacement-imbibition curve and the scanning curve according to the mathematical model, and determine the displacement-imbibition capillary pressure mathematical model fitting.

[0087] Specifically, the curve determination unit includes a sample determination module, a first determination module and a curve determination module.

[0088] A sample determination module is used to determine typical reservoir characteristic samples and perform a displacement-imbibition experiment on the typical reservoir characteristic samples according to the displacement-imbibition process;

[0089] A first determination module is configured to determine displacement-imbibition capillary pressure characteristics under reservoir wettability conditions based on the displacement-imbibition experiment;

[0090] The curve determination module is used to determine the typical reservoir boundary displacement-imbibition curve and the scanning curve for starting imbibition at different selected oil saturations based on the displacement-imbibition capillary pressure characteristics.

[0091] Specifically, the first determining unit includes a second determining module, a pressure field determining module and a third determining module.

[0092] The second determination module is used to determine the mathematical model of the original saturation of the ancient oil reservoir based on the mathematical model of the ancient free water interface and the displacement capillary pressure;

[0093] A pressure field determination module, used to determine the current capillary pressure field based on the current free water interface;

[0094] The third determination module is used to determine the current saturation mathematical model of the ancient oil reservoir under the current capillary pressure field based on the imbibition capillary pressure mathematical model.

[0095] The paleo-reservoir saturation model research method and system of the present invention, based on the characteristics that the water saturation of conventional oil layers changes with the changes in oil column height and reservoir physical properties, can form an accurate representation of the residual oil saturation of paleo-reservoirs, clarify the resource potential, and lay a solid foundation for development; at the same time, it can clearly define the residual oil distribution area between the current free water surface and the ancient free water surface, and clearly distinguish it from conventional oil layers. Based on this, different development methods can be adopted respectively, which can reduce development risks.

[0096] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for studying paleo-reservoir saturation models, characterized in that: The method comprises: The mathematical model of the original saturation of the ancient reservoir is determined by fitting the mathematical model of displacement-imbibition capillary pressure, and the mathematical model of the current saturation of the ancient reservoir is determined based on the mathematical model of the original saturation of the ancient reservoir by selecting different ancient free water interfaces. According to the error value of the mathematical model of the present saturation of the ancient oil reservoir and the water saturation interpreted by well logging, the appropriate ancient free water interface is determined; Adjust the present free water interface, adapt the ancient free water interface and the present saturation mathematical model of the ancient oil reservoir to obtain the water saturation interpretation model; The water saturation interpretation model is applied to the three-dimensional geological model to obtain a three-dimensional water saturation model.

2. The paleo-oil reservoir saturation model research method according to claim 1, characterized in that: The mathematical model fitting for determining displacement-imbibition capillary pressure includes: Determine the structural-reservoir evolution history and the displacement-imbibition process experienced by the reservoir based on the structural-reservoir evolution history; According to the displacement-imbibition process, the displacement-imbibition curve of the typical reservoir boundary and the scanning curve of imbibition start at different selected oil saturations are determined; A displacement-imbibition capillary pressure mathematical model is determined, and parameter fitting is performed on the displacement-imbibition curve and the scanning curve according to the mathematical model to determine the displacement-imbibition capillary pressure mathematical model fitting.

3. The method for studying the ancient oil reservoir saturation model according to claim 1, characterized in that: The reservoir data includes core data, well logging data, oil test data and pressure gradient.

4. The method for studying the ancient oil reservoir saturation model according to claim 2, characterized in that: Determine the typical reservoir boundary displacement-imbibition curve and the scan curve for imbibition onset at selected oil saturations including: determining typical reservoir characteristic samples, and conducting displacement-imbibition experiments on the typical reservoir characteristic samples according to the displacement-imbibition process; Determining displacement-imbibition capillary pressure characteristics under reservoir wettability conditions based on the displacement-imbibition experiment; Based on the displacement-imbibition capillary pressure characteristics, the typical reservoir boundary displacement-imbibition curve and the scanning curve for the onset of imbibition at different selected oil saturations are determined.

5. The method for studying the ancient oil reservoir saturation model according to claim 4, characterized in that: Based on the sampling conditions, the reservoir samples are selected from the entire reservoir; or, Typical reservoir characteristic samples were selected according to sedimentary facies type and rock type.

6. The method for studying the ancient oil reservoir saturation model according to claim 2 or 4, characterized in that: The mathematical model for determining the present saturation of ancient oil reservoirs includes: Determine the mathematical model of the original saturation of the ancient reservoir based on the mathematical model of the ancient free water interface and displacement capillary pressure; Determine the present capillary pressure field based on the present free water interface; The mathematical model of the current saturation of the ancient oil reservoir under the current capillary pressure field is determined based on the mathematical model of the imbibition capillary pressure.

7. A paleo-reservoir saturation model research system, characterized in that: The system includes a first determination unit, a paleo-interface determination unit, a second determination unit, and a three-dimensional model determination unit, wherein: The first determination unit is used to determine the original saturation mathematical model of the ancient oil reservoir based on the displacement-imbibition capillary pressure mathematical model, select different ancient free water interfaces and determine the current saturation mathematical model of the ancient oil reservoir based on the original saturation mathematical model of the ancient oil reservoir; The paleointerface determination unit is used to determine the appropriate paleofree water interface based on the mathematical model of the present saturation of the paleo-oil reservoir and the error value of the water saturation interpreted by well logging; The second determination unit is used to adjust the present free water interface, adapt the ancient free water interface and the present saturation mathematical model of the ancient oil reservoir, and obtain the water saturation interpretation model; The three-dimensional model determination unit is used to apply the water saturation interpretation model to the three-dimensional geological model to obtain a three-dimensional water saturation model.

8. The paleo-reservoir saturation model research system according to claim 7, characterized in that: The system further includes a third determination unit, a curve determination unit and a fitting determination unit, The third determination unit is used to determine the structural-reservoir evolution history and determine the displacement-imbibition process experienced by the reservoir based on the structural-reservoir evolution history; a curve determination unit for determining a typical reservoir boundary displacement-imbibition curve and a scanning curve for imbibition start at different selected oil saturations according to the displacement-imbibition process; The fitting determination unit is used to determine the displacement-imbibition capillary pressure mathematical model, perform parameter fitting on the displacement-imbibition curve and the scanning curve according to the mathematical model, and determine the displacement-imbibition capillary pressure mathematical model fitting.

9. The paleo-oil reservoir saturation model research system according to claim 8, characterized in that: The curve determination unit includes a sample determination module, a first determination module and a curve determination module. A sample determination module is used to determine typical reservoir characteristic samples and perform a displacement-imbibition experiment on the typical reservoir characteristic samples according to the displacement-imbibition process; A first determination module is configured to determine displacement-imbibition capillary pressure characteristics under reservoir wettability conditions based on the displacement-imbibition experiment; The curve determination module is used to determine the typical reservoir boundary displacement-imbibition curve and the scanning curve for starting imbibition at different selected oil saturations based on the displacement-imbibition capillary pressure characteristics.

10. The paleo-oil reservoir saturation model research system according to claim 8, characterized in that: The first determination unit includes a second determination module, a pressure field determination module and a third determination module. The second determination module is used to determine the mathematical model of the original saturation of the ancient oil reservoir based on the mathematical model of the ancient free water interface and the displacement capillary pressure; A pressure field determination module, used to determine the current capillary pressure field based on the current free water interface; The third determination module is used to determine the current saturation mathematical model of the ancient oil reservoir under the current capillary pressure field based on the imbibition capillary pressure mathematical model.

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