Method for determining permeability of fractured-vuggy reservoir

Abstract

The invention discloses a method for determining the permeability of a fractured-vuggy reservoir. The method comprises the following steps: establishing a theoretical model related to the permeability, porosity, split-phase size and karst background of three phases of pores, fractures and karst caves in the fractured-vuggy reservoir; screening a tracer test well group, and determining the migration flow velocity of the tracer by using the obtained breakthrough time and migration path of the tracer; and determining parameters of different split phases in the theoretical model through a numerical model test to obtain a complete theoretical model for determining the permeability. The correlation between the permeability of different split phases and the porosity, size and karst background of the different split phases is established, and the method can be applied to permeability prediction of other areas in the same oil reservoir; the migration flow velocity is determined according to the migration path and time of the tracer agent, then the permeability values of different split phases are determined by utilizing the Darcy law, and the method is relatively reliable in terms of physical principles and engineering backgrounds.

Description

Technical Field

[0001] The present invention relates to the field of reservoir physical property prediction, and specifically to a method for determining reservoir permeability based on different phase separations of pores, fractures, and caves in a fractured-vuggy reservoir. Background Art

[0002] Existing methods for calculating the permeability of fractured-vuggy reservoirs mainly include seismic, core analysis, logging, and well testing methods. (1) The basic principle of seismic analysis method is to obtain the relationship between seismic records and physical parameters of the two-phase medium according to the seismic wave propagation theory in the two-phase medium. Since the relationship between permeability and seismic attributes is a multi-valued function, the RoughSet (RS) theory can be used to find the seismic attributes closely related to permeability to obtain an optimized attribute combination, and then a neural network is used for training. The training result can perform pattern classification on the seismic attributes with attribute selection at the un-drilled location, and finally the function approximation method is used to predict the permeability. (2) Geophysical logging is implemented in almost every well, and logging data is the most easily obtained data. Therefore, obtaining permeability from logging data is a key research area for people. The main methods for obtaining formation permeability through logging are: ① Empirical method, using Archie's formula; ② Nuclear magnetic logging method (NML); ③ Geochemical logging method (GLT). For the special structure of fractured-vuggy reservoirs, this type of method is less used and is only applicable to some highly filled karst caves. (3) Well testing is a method based on seepage mechanics, using various test instruments to study the characteristics of oil, gas, and water layers and the various characteristic parameters, production capacity, and the connectivity relationship between oil, gas, and water of the test well through the testing of the production dynamics of oil wells, gas wells, or water wells. Determining permeability through well testing is also a commonly used method. The energy and diffusion ability of the formation can be obtained through transient well testing. To calculate permeability through well testing, we need to know the formation thickness affected by the disturbance. Usually, open-hole logging (gamma ray, spontaneous potential, porosity logging) is used to determine the formation thickness. The formation thickness affected by well testing may not be consistent with that calculated by logging. The only effective way is to obtain the pressure drop in production and the production profile. With the flow profile information at each depth, the transient diffusion equation of the pressure drop can be obtained. By plotting the P bhf ~logt curve to obtain a straight line with a slope of m, the k can be obtained, which represents the average permeability of the formation affected by the disturbance.

[0003] Due to the particularity of fractured-vuggy reservoirs, there is currently no specific prediction and calculation method for the permeability of pores, fractures, and caves in fractured-vuggy reservoirs. Under the above three calculation methods, only the vertical distribution of permeability near a single well or the overall permeability value representing the reservoir surroundings is calculated. Therefore, it is necessary to develop a method for determining the permeability of different phase separations of pores, fractures, and caves in fractured-vuggy reservoirs to predict the permeability of other pores, fractures, and caves in the target block. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method flow for determining the theoretical relationships among fracture-vug size, porosity, karst properties, and permeability based on tracer testing, seismic interpretation, and seepage equation data. First, a theoretical model related to the permeability of pores, fractures, and caves in a fracture-vug reservoir, porosity, phase size, and karst background is established; secondly, based on seismic data, a group of tracer test well groups are screened in the Tahe fracture-vug reservoir, where the migration paths of the tracers in the well groups are relatively clear, facilitating the direct calculation of the migration path size between two wells; then, the flow velocity of the tracer in the fracture-vug reservoir is determined using the breakthrough time and migration path of the tracer; finally, through numerical experiments, a numerical model related to the target well group is established to determine the pore space, size, and distance of different phases, and then by setting the permeability values of different phases until the simulated breakthrough time of the tracer is equal to the actual breakthrough time, the correlation coefficients in the theoretical model are determined using the curve regression method. This theoretical model can calculate the phase permeability in other areas of the same reservoir, effectively solving the problem of calculating the different phase permeabilities in a fracture-vug reservoir. Model testing and application in actual work areas show that the present invention can better predict the permeabilities of pores, fractures, and caves in different phases in other areas of the same fracture-vug reservoir, and has good application prospects. The specific technical solutions are as follows:

[0005] A method for determining the permeability of a fracture-vug reservoir, comprising the following steps:

[0006] Establish a theoretical model related to the permeability of pores, fractures, and caves in a fracture-vug reservoir, porosity, phase size, and karst background;

[0007] Screen a group of tracer test well groups, and determine the flow velocity of the tracer migration using the obtained breakthrough time and migration path of the tracer;

[0008] Determine the parameters of different phases in the theoretical model through numerical model experiments, and obtain a complete theoretical model for determining permeability.

[0009] Preferably, the theoretical model is:

[0010] Cave phase:

[0011]

[0012] Pore phase:

[0013]

[0014] Fracture phase:

[0015]

[0016] Wherein, k c 、k p 、kf Absolute permeability of solution cave, pore and fracture phases, m c , m p , m f Overall correlation coefficients of solution cave, pore and fracture phases, a c , a p , a f Porosity correlation coefficients of solution cave, pore and fracture phases, b c , b p , b f Diameter correlation coefficients of solution cave, pore and fracture phases, c c , c p , c f Karst background correlation coefficients of solution cave, pore and fracture phases Porosity, d c Diameter of different karst backgrounds

[0017] Preferably, when screening a group of tracer test well groups, the wells with clear migration paths of tracers and affected wells are screened through seismic data

[0018] Preferably, the tracer test well group has the following conditions: fast tracer response time; clear tracer migration path; simple relevant karst phase background relationship

[0019] Preferably, determining the parameters of different sub-phases in the theoretical model through numerical model tests includes the following

[0020] Through numerical experiments, establish a numerical model related to the target well group, determine the pore space, size and distance of different sub-phases, and then by setting the permeability values of different sub-phases until the simulated breakthrough time of the tracer is equal to the actual breakthrough time, use the curve regression method to determine the relevant parameters in the theoretical model

[0021] Preferably, through numerical experiments, establish a numerical model related to the target well group, determine the pore space, size and distance of different sub-phases, and then by setting the permeability values of different sub-phases until the simulated breakthrough time of the tracer is equal to the actual breakthrough time, use the curve regression method to determine the relevant parameters in the theoretical model, which includes the following

[0022] Determine the relationship between flow velocity and permeability according to Darcy's formula

[0023]

[0024] where u x is the flow velocity term, k x is the absolute permeability of the tracer path, μ is the viscosity of the tracer, u xis a total velocity, which includes the sum of the velocities of the tracer migrating in different sub-phases, as follows:

[0025]

[0026] where s1, s2, and s3 are the migration paths of the tracer in different sub-phases respectively, and the parameter x refers to the distance in the flow direction in Darcy's formula;

[0027] Numerical experiments are carried out, different permeabilities are assigned to different sub-phases to achieve equal total flow rates, and then curve regression is performed based on the test points, and finally the relevant parameters of the permeabilities of different sub-phases are obtained.

[0028] Preferably, s1, s2, and s3 are measured through seismic data volumes.

[0029] Preferably, the following steps are further included:

[0030] The complete theoretical model is used to predict the permeabilities of other regions in the same oil reservoir.

[0031] Preferably, the total seepage velocity of the tracer is obtained as 18.45 m / d through the path and the affected time.

[0032] Preferably, the complete theoretical model is as follows:

[0033]

[0034]

[0035]

[0036] It has the following technical effects:

[0037] The present invention establishes a theoretical relationship method process for determining the fracture-vug size, porosity, karst property, and permeability based on the three-party data of tracer testing, seismic interpretation, and seepage equation. Based on the three-party data of tracer testing, seismic interpretation, and seepage equation, the present invention constructs a theoretical equation for the fracture-vug size, porosity, and permeability of the pore, fracture, and vug three-phases in the fracture-vug reservoir, further highlighting the permeability characterization characteristics of different sub-phases in the fracture-vug reservoir and improving the prediction accuracy of the sub-phase permeability in similar fracture-vug reservoirs.

[0038] For fracture-vug reservoirs, the correlation between the permeabilities of different sub-phases and their porosities, sizes, and karst backgrounds is established, which can be applied to the prediction of permeabilities in other regions of the same oil reservoir; the migration velocity is determined through the path and time of tracer migration, and then the permeability values of different sub-phases are determined using Darcy's law. This method is relatively reliable both in terms of physical principles and engineering backgrounds. Description of the Drawings

[0039] Figure 1 It is a flowchart of a specific implementation manner of a method for determining the permeability of a fracture-vuggy reservoir provided.

[0040] Figure 2 Well TK650 is shown, which is a well with a relatively clear tracer response path screened in the Tahe area.

[0041] Figure 3 It shows a numerical experiment carried out on the section where the tracer migrates, and different permeability values are assigned to different phases to make the total flow rate equal. Specific implementation manner

[0042] To solve the above technical problems, the present invention provides a method for determining the permeability of a fracture-vuggy reservoir. Combining Figures 1-3 , Figure 1 It is a flowchart of a specific implementation manner of a method for determining the permeability of a fracture-vuggy reservoir provided.

[0043] Figure 2 Well TK650 is shown, which is a well with a relatively clear tracer response path screened in the Tahe area.

[0044] Figure 3 It shows a numerical experiment carried out on the section where the tracer migrates, and different permeability values are assigned to different phases to make the total flow rate equal.

[0045] A method for determining the permeability of a fracture-vuggy reservoir provided includes the following steps:

[0046] Establish a theoretical model related to the permeability, porosity, phase size, and karst background of the pore, fracture, and cave phases in the fracture-vuggy reservoir;

[0047] Screen a group of tracer test well groups, and use the breakthrough time and migration path of the obtained tracer to determine the flow rate of the tracer migration;

[0048] Determine the parameters of different phases in the theoretical model through numerical model tests, and obtain a complete theoretical model for determining the permeability.

[0049] Preferably, the theoretical model is:

[0050] Cave phase:

[0051]

[0052] Pore phase:

[0053]

[0054] Fracture phase:

[0055]

[0056] Among them, k c , k p , k f are the absolute permeabilities of the karst cave, pore and fracture phases respectively, m c , m p , m f are the overall correlation coefficients of the karst cave, pore and fracture phases respectively, a c , a p , a f are the porosity correlation coefficients of the karst cave, pore and fracture phases respectively, b c , b p , b f are the diameter correlation coefficients of the karst cave, pore and fracture phases respectively, c c , c p , c f are the karst background correlation coefficients of the karst cave, pore and fracture phases respectively, is the porosity, d c is the diameter of different karst backgrounds.

[0057] In a specific embodiment, when screening a group of tracer test well groups, wells with clear migration paths of tracers and affected wells are screened through seismic data.

[0058] Among them, the tracer test well group has the following conditions: fast tracer response time; clear tracer migration path; simple relevant karst facies background relationship.

[0059] In a specific embodiment, determining the parameters of different sub-phases in the theoretical model through numerical model experiments includes the following:

[0060] Through numerical experiments, a numerical model related to the target well group is established, the pore space, size and distance of different sub-phases are determined, and then by setting the permeability values of different sub-phases until the simulated breakthrough time of the tracer is equal to the actual breakthrough time, the relevant parameters in the theoretical model are determined using the curve regression method.

[0061] In a specific embodiment, through numerical experiments, a numerical model related to the target well group is established, the pore space, size and distance of different sub-phases are determined, and then by setting the permeability values of different sub-phases until the simulated breakthrough time of the tracer is equal to the actual breakthrough time, the relevant parameters in the theoretical model are determined using the curve regression method, which includes the following:

[0062] Determine the relationship between flow velocity and permeability according to Darcy's formula:

[0063]

[0064] Among them, ux is the flow velocity term, k x is the absolute permeability of the tracer pathway, μ is the viscosity of the tracer, and u x is the total velocity, which includes the sum of the velocities of the tracer migrating in different sub-phases, as follows:

[0065]

[0066] where s1, s2, and s3 are the migration paths of the tracer in different sub-phases respectively, and the parameter x refers to the distance in the flow direction in Darcy's formula;

[0067] Numerical experiments are carried out. Different permeabilities are given to different sub-phases to achieve equal total flow velocities, and then curve regression is performed based on the test points, and finally the relevant parameters of the permeabilities of different sub-phases are obtained.

[0068] The present invention establishes a theoretical relationship method process for determining the fracture-vug size, porosity, karst properties, and permeability based on three-party data of tracer testing, seismic interpretation, and seepage equations. Based on the three-party data of tracer testing, seismic interpretation, and seepage equations, the present invention constructs theoretical equations for the fracture-vug size, porosity, and permeability of the pore, fracture, and vug three-phases in a fracture-vug reservoir, further highlighting the permeability characterization characteristics of different sub-phases in a fracture-vug reservoir and improving the prediction accuracy of the sub-phase permeability in similar fracture-vug reservoirs.

[0069] For a fracture-vug reservoir, the correlation between the permeability of different sub-phases and their porosity, size, and karst background is established, which can be applied to the prediction of the permeability in other areas of the same reservoir; the migration velocity is determined through the path and time of tracer migration, and then the permeability values of different sub-phases are determined using Darcy's law. This method is relatively reliable both in terms of physical principles and engineering background.

[0070] In a specific embodiment, s1, s2, and s3 are measured through seismic data volumes.

[0071] In a specific embodiment, the following steps are further included:

[0072] The complete theoretical model is used to predict the permeability in other areas of the same reservoir.

[0073] Such as Figure 2 and 3 , in a specific embodiment, the total seepage velocity of the tracer is obtained as 18.45 m / d through the path and the affected time.

[0074] The obtained complete theoretical model is as follows:

[0075]

[0076]

[0077]

Claims

1. A method for determining the permeability of a fractured-vuggy reservoir, characterized in that, It includes the following steps: Establish a theoretical model of the permeability of the pore, fracture, and karst cave phases in a fractured-vuggy reservoir, which is related to porosity, phase size, and karst background; Select a group of tracer test well groups, and determine the flow velocity of tracer migration using the breakthrough time and migration path of the obtained tracer; Determine the parameters of different phases in the theoretical model through numerical model tests, and obtain a complete theoretical model for determining permeability.

2. The method for determining the permeability of a fracture-vuggy reservoir according to claim 1, wherein The theoretical model is as follows: Karst cave phase: Pore phase: Fracture phase: where k c , k p , k f are the absolute permeabilities of the karst cave, pore and fracture phases, respectively, in m c , m p , m f are the overall correlation coefficients of the karst cave, pore and fracture phases, respectively, ac, ap, af are the porosity correlation coefficients of the karst cave, pore and fracture phases, respectively, bc, bp, bf are the diameter correlation coefficients of the karst cave, pore and fracture phases, respectively, cc, cp, cf are the karst background correlation coefficients of the karst cave, pore and fracture phases, is the porosity, and dc is the diameter of different karst backgrounds.

3. The method for determining the permeability of a fracture-vuggy reservoir according to claim 2, wherein When selecting a group of tracer test well groups, the wells with clear migration paths of tracers and affected wells are selected through seismic data.

4. The method for determining the permeability of a fracture-vuggy reservoir according to claim 3, wherein The tracer test well groups have the following conditions: fast tracer response time; clear tracer migration path; simple relevant karst phase background relationship.

5. The method for determining the permeability of a fractured-vuggy reservoir according to claim 2, characterized in that Determining the parameters of different phases in the theoretical model through numerical model tests includes the following: Through numerical experiments, establish a numerical model related to the target well group, determine the pore space, size, and distance of different phases, and then set the permeability values of different phases until the simulated breakthrough time of the tracer is equal to the actual breakthrough time, and use the curve regression method to determine the relevant parameters in the theoretical model.

6. The method for determining the permeability of a fracture-vuggy reservoir according to claim 5, characterized in that, Through numerical experiments, establish a numerical model related to the target well group, determine the pore space, size, and distance of different phases, and then set the permeability values of different phases until the simulated breakthrough time of the tracer is equal to the actual breakthrough time, and use the curve regression method to determine the relevant parameters in the theoretical model, which includes the following: Determine the relationship between flow velocity and permeability according to Darcy's formula: Where ux is the flow velocity term, kx is the absolute permeability of the tracer's path, μ is the viscosity of the tracer, and ux is the total velocity, which includes the sum of the velocities of the tracer migrating in different phases, as follows: Where s1, s2, and s3 are the migration paths of the tracer in different phases respectively, and the parameter x refers to the distance in the flow direction in Darcy's formula; Conduct numerical experiments, assign different permeabilities to different phases to achieve equal total flow velocities, and then perform curve regression based on the test points to finally obtain the relevant parameters of the permeabilities of different phases.

7. The method for determining the permeability of a fracture-vuggy reservoir according to claim 6, wherein s1, s2, and s3 are measured through seismic data volumes.

8. The method for determining the permeability of a fracture-vuggy reservoir according to claim 6, wherein It also includes the following steps: Use this complete theoretical model to predict the permeability of other areas in the same reservoir.

9. The method for determining the permeability of a fracture-vuggy reservoir according to claim 8, wherein The total seepage velocity of the tracer is obtained as 18.45 m / d through the path and response time.

10. The method for determining the permeability of a fractured-vuggy reservoir according to claim 9, wherein The complete theoretical model is as follows:

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