Reservoir flow property change characterization method based on water drive intensity and application method thereof

Abstract

The invention discloses a reservoir flow property change characterization method based on water flooding intensity and an application method thereof. The method comprises the specific steps that S1, a multi-period water flooding experiment is carried out to calculate reservoir flow properties of different stages; s2, calculating the water drive strength of each stage by adopting an accumulative comprehensive strength multiple; and S3, establishing a model that the reservoir flow property changes along with the water drive intensity, and representing the change of the reservoir flow property. The method has the beneficial effects that a multi-period water flooding experiment is designed, and the change of the flow property of the reservoir can be quickly measured by using a continuous water flooding process once. Meanwhile, the effective permeability of each phase of fluid participating in flowing is preferably selected to directly reflect the strength of the reservoir flow property, the accumulated comprehensive strength multiple is designed to comprehensively measure the water drive strength, and the change rule of the reservoir flow property is accurately represented based on a mathematical model of the two. The invention provides an application method of a reservoir flow property change characterization result, which can be applied to the development practice of a water-driven oil-gas field and guide the deployment of an oil-gas field development adjustment scheme.

Description

Technical Field

[0001] The invention relates to the technical field of water-drive oil and gas reservoir development and exploitation, and more specifically to a reservoir flow property change characterization based on water-drive intensity and an application method thereof. Background Art

[0002] The development practice of multiple water-driven oil and gas reservoirs shows that with the long-term continuous scouring of injected water or marginal bottom water, the rock mineral characteristics, physical properties, multiphase seepage characteristics and other properties of the oil and gas reservoirs will change, which is quite different from the initial development. This is because the injected water causes the crystal layer of clay minerals in the reservoir to expand or crack. Under the influence of long-term continuous scouring, strong sensitivity and sudden changes in pore fluid pressure, the clay mineral particles are induced to fall off and migrate, causing the pore structure of the reservoir to change. The falling of clay mineral particles and the displacement of in-situ fluids by injected water will expose the surface of hydrophilic minerals (quartz, feldspar, etc.) in the rock particles, changing the wettability of the reservoir.

[0003] This characteristic that changes over time at the microscopic scale will affect the flow law of fluids in the reservoir, and at the macroscopic scale it will be manifested as a change in the reservoir's ability to allow fluids to pass through, that is, a change in the reservoir flow properties. This characteristic of flow property change will interfere with developers' understanding of the current production characteristics and remaining oil distribution of water-driven oil and gas reservoirs. If the reservoir flow property parameters used in the early stages of oil and gas field development continue to be used after the oil and gas field has been put into production for many years, the numerical simulation calculation results will be far from the actual state of the oil and gas reservoir, affecting the efficient potential of the oil and gas field. Therefore, the accurate characterization of the law of reservoir flow property change has become the key to accurately understanding the oil and gas reservoirs developed by water drive.

[0004] Most of the existing studies on reservoir flow quality changes use relative permeability and water drive time to characterize them. The change characteristics of different water drive times are studied through the results of multiple sets of core displacement experiments. On the one hand, multiple experiments are prone to introduce large errors and the research efficiency is low. On the other hand, only the water injection volume corresponding to the water drive time is considered to cause flow quality changes, and the water drive intensity, which is more relevant to the change, is not considered. Since the rapid and accurate characterization of reservoir flow quality changes has a great impact on the deployment of oil and gas field development adjustments, it is necessary to propose a method that uses a continuous process of a displacement experiment and is based on water drive intensity to quickly and accurately characterize the law of reservoir flow quality changes, and can be applied to the development practice of water drive oil and gas reservoirs. Summary of the invention

[0005] The present invention overcomes the deficiencies in the prior art and provides a method for characterizing reservoir flow property changes based on water drive intensity and an application method thereof.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A method for characterizing changes in reservoir flow properties based on water flooding intensity, comprising the following specific steps:

[0008] S1. Carry out multi-period waterflooding experiments to calculate reservoir flow properties at different stages;

[0009] S2. Calculate the water drive strength at each stage using the cumulative comprehensive strength multiple;

[0010] S3. Establish a model for the change of reservoir flow properties with water drive intensity to characterize the change of reservoir flow properties.

[0011] The multi-period waterflooding experiment adopts a continuous waterflooding process to realize the calculation of the reservoir flow properties corresponding to any metering point with an incremental cumulative oil production within the final waterflooding multiple.

[0012] In S1, when the final water injection volume set in the experiment is reached and the oil production has no increment compared with the previous cumulative oil production increment measurement point at the end of the final water flooding, the previous period is regarded as the last period.

[0013] The specific steps of S1 include:

[0014] S11, setting the final water drive multiple;

[0015] S12, continuously injecting water into the core, measuring the volume of water injected during this process and the corresponding cumulative oil production, cumulative liquid production and displacement pressure difference, and calculating the corresponding water drive multiple;

[0016] S13, determining whether the injected water volume reaches the set value;

[0017] When the injected water volume reaches the set value, the water drive multiple, cumulative oil production, cumulative liquid production and displacement pressure difference are recorded, the effective permeability of the water phase is calculated, and this period is recorded as the first period, i=1 is recorded, and step S14 is entered;

[0018] When the injected water volume does not reach the set value, repeat step S12;

[0019] S14, determining whether the cumulative oil production has increased;

[0020] When it is determined that the cumulative oil production has increased, the process proceeds to step S15;

[0021] When it is judged that the cumulative oil production has no increase, re-judge;

[0022] S15, record the corresponding water drive multiple;

[0023] S16, determining whether the difference between the water drive multiple currently recorded in S15 and the water drive multiple last recorded is not less than 10;

[0024] When the judgment condition is met, i=i+1, the water drive multiple is rounded up to ten, the current period is recorded as the i-th period, the cumulative oil production, cumulative liquid production and displacement pressure difference at this time are measured, the effective permeability of the water phase is calculated, and the process goes to step S17;

[0025] When the judgment condition is not met, the two time periods are merged, the smaller time period number is counted, and the process returns to step S15;

[0026] S17, judging whether the final water drive multiple set in the experiment has been reached;

[0027] When the conditions are met, the overall cumulative oil production, cumulative liquid production, displacement pressure difference are measured, the effective permeability of the water phase for the entire period is calculated, and the process is terminated;

[0028] When the condition is not met, return to step S12.

[0029] S18. Calculate the effective permeability of each phase fluid based on experimental data.

[0030] The set value of the S13 injected water volume is 30 times the core pore volume.

[0031] The reservoir flow property in S1 is the effective permeability of each phase of fluid involved in the flow. The calculation formula of effective permeability is as follows:

[0032] K i =K ri ·K o0 (S wc )

[0033] Where: i is a phase of fluid that is flowing, such as oil, gas, or water; K i is the effective permeability of phase i fluid, mD; K ri is the relative permeability of phase i fluid, dimensionless; K o0 (S wc ) is the effective permeability of the oil phase at the irreducible water saturation measured before the water flooding experiment, mD.

[0034] In S2, the water drive strength of each stage is calculated by using the cumulative comprehensive strength multiple. The calculation formula of the cumulative comprehensive strength multiple value is as follows:

[0035]

[0036] Where: G is the cumulative comprehensive strength multiple, dimensionless; q w is the flow rate of injected water, cm 3 / s; V p is the pore volume of the core, cm 3 ; q(t) is the liquid flow rate at the core outlet end face at time t, cm 3 / s; Δp(t) is the displacement pressure difference at time t, MPa, q0 is the liquid flow rate at the core outlet end face in the initial pure oil flow stage, cm 3 / s; Δp0 is the displacement pressure difference in the initial pure oil flow stage, MPa.

[0037] The specific steps of S3 include:

[0038] S31, draw a scatter plot of oil and gas saturation and cumulative comprehensive intensity multiples in each period, and obtain the first relationship through regression;

[0039] S32, calculating the effective permeability of the fluid by the phase permeability value obtained from the last period of testing to characterize the flow properties of the reservoir;

[0040] S33, through the relationship between fluid effective permeability and oil and gas saturation, the second relationship is obtained by regression;

[0041] S34. Combine the first relationship and the second relationship to obtain a mathematical model that characterizes the change of reservoir flow properties with water drive intensity.

[0042] The oil and gas saturation refers to the oil saturation at the last incremental measurement point of cumulative oil production before injecting 30 times the pore volume, the increased oil saturation in each period and the ultimate residual oil saturation in the last period. The effective fluid permeability refers to the effective permeability of each phase fluid corresponding to the oil and gas saturation.

[0043] A method for applying the characterization results of reservoir flow property changes based on water flooding intensity, using the characterization method described in any one of claims 1 to 9, comprising:

[0044] The judgment process is used to judge whether the water injection volume multiple of the oil and gas reservoir grid is greater than 30 times the injected pore volume in the oil and gas reservoir numerical model;

[0045] A marking process is used to mark the oil and gas reservoir model grids with a judgment result of being greater than and calculate the cumulative comprehensive strength multiple;

[0046] A computational process for calculating values ​​of grid reservoir flow properties;

[0047] The output process is used to output the reservoir flow properties of each grid in the numerical model of the oil and gas reservoir under current conditions, which is used for iterative calculations of the numerical simulator and to guide the deployment of oil and gas field development adjustments.

[0048] The beneficial effects of the present invention are:

[0049] This scheme designs a multi-period water flooding experiment, which can use a continuous water flooding process to quickly measure the changes in reservoir flow properties. At the same time, the effective permeability of each phase of fluid participating in the flow is preferably directly reflected in the strength of the reservoir flow properties, and the cumulative comprehensive strength multiple is designed to comprehensively measure the water flooding strength. The mathematical model based on the two accurately characterizes the law of changes in reservoir flow properties. The present invention provides an application method for the characterization results of reservoir flow property changes, which can be applied to the development practice of water-driven oil and gas fields and guide the deployment of oil and gas field development adjustment plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of a flow chart of a method for characterizing changes in reservoir flow properties provided by the present invention;

[0051] Figure 2 A schematic diagram of a multi-period water flooding experiment in an embodiment of the present invention;

[0052] Figure 3 It is a display diagram of the calculation results of the water phase reservoir flow properties in an embodiment of the present invention;

[0053] Figure 4 A schematic diagram of a flow chart for establishing a mathematical model of reservoir flow properties changing with water drive intensity provided by the present invention. DETAILED DESCRIPTION

[0054] Example

[0055] This embodiment is specifically described by taking A water-driven sandstone reservoir as an example.

[0056] like Figure 1 As shown, the present invention provides a method for characterizing changes in reservoir flow properties based on water flooding intensity, and the specific steps include:

[0057] S1. Carry out multi-period waterflooding experiments to calculate reservoir flow properties at different stages;

[0058] S2. Calculate the water drive strength at each stage using the cumulative comprehensive strength multiple;

[0059] S3. Establish a model for the change of reservoir flow properties with water flooding intensity to characterize the change of reservoir flow properties

[0060] In S1, the multi-period water flooding experiment requires the water injection volume to reach more than 30 times the core pore volume.

[0061] At the same time, the multi-period water flooding experiment defines the first period as the period from the start of water injection to the injection of 30 times the pore volume, and the water flooding multiples corresponding to the second period and each subsequent period are defined as the water flooding multiples corresponding to each cumulative oil production incremental measurement point between the first period and the end of the final water flooding, rounded up to the nearest ten. If the water flooding multiples corresponding to two cumulative oil production incremental measurement points are less than 10, then the two periods are merged and the smaller period number is used as the basis; if the final water injection volume set in the experiment is reached and there is no incremental oil production at the end of the final water flooding compared with the previous cumulative oil production incremental measurement point, the previous period will be taken as the last period of the water flooding experiment to carry out a study on the changes in reservoir flow properties.

[0062] like Figure 2 As shown, the specific steps of S1 include:

[0063] In S1, when the final water injection volume set in the experiment is reached and the oil production has no increment compared with the previous cumulative oil production increment measurement point at the end of the final water flooding, the previous period is regarded as the last period.

[0064] The specific steps of S1 include:

[0065] S11, setting the final water drive multiple;

[0066] S12, continuously injecting water into the core, measuring the volume of water injected during this process and the corresponding cumulative oil production, cumulative liquid production and displacement pressure difference, and calculating the corresponding water drive multiple;

[0067] S13, determining whether the injected water volume reaches the set value;

[0068] When the injected water volume reaches the set value, the water drive multiple, cumulative oil production, cumulative liquid production and displacement pressure difference are recorded, the effective permeability of the water phase is calculated, and this period is recorded as the first period, i=1 is recorded, and step S14 is entered;

[0069] When the injected water volume does not reach the set value, repeat step S12;

[0070] S14, determining whether the cumulative oil production has increased;

[0071] When it is determined that the cumulative oil production has increased, the process proceeds to step S15;

[0072] When it is judged that the cumulative oil production has no increase, re-judge;

[0073] S15, record the corresponding water drive multiple;

[0074] S16, determining whether the difference between the water drive multiple currently recorded in S15 and the water drive multiple last recorded is not less than 10;

[0075] When the judgment condition is met, i=i+1, the water drive multiple is rounded up to ten, the current period is recorded as the i-th period, the cumulative oil production, cumulative liquid production and displacement pressure difference at this time are measured, the effective permeability of the water phase is calculated, and the process goes to step S17;

[0076] When the judgment condition is not met, the two time periods are merged, the smaller time period number is counted, and the process returns to step S15;

[0077] S17, judging whether the final water drive multiple set in the experiment has been reached;

[0078] When the conditions are met, the overall cumulative oil production, cumulative liquid production, displacement pressure difference are measured, the effective permeability of the water phase for the entire period is calculated, and the process is terminated;

[0079] When the condition is not met, return to step S12.

[0080] S18. Calculate the effective permeability of each phase fluid based on experimental data.

[0081] At the same time, the cumulative oil production, cumulative liquid production, and displacement pressure difference must be measured separately at the end point of each period of the multi-period water flooding experiment, and the effective permeability of the water phase must be calculated; at the end of the final water flooding, the cumulative oil production, cumulative liquid production, and displacement pressure difference must be measured to calculate the effective permeability of the water phase.

[0082] The reservoir flow properties are characterized by the effective permeability of each phase of fluid involved in the flow, which is calculated by formula A:

[0083] K i =K ri ·K o0 (S wc )(Formula A)

[0084] Where: i is a phase of fluid that is flowing, such as oil, gas, or water; K i is the effective permeability of phase i fluid, mD; K ri is the relative permeability of phase i fluid, dimensionless, obtained by processing the experimental data of multi-period water flooding experiments; K o0 (S wc ) is the effective permeability of the oil phase at the irreducible water saturation measured before the water flooding experiment, mD.

[0085] In this embodiment, a multi-period water flooding experiment was carried out using a natural core of a water-flooded sandstone reservoir A. According to the maximum water injection volume of the grid of the numerical simulation model of the water-flooded sandstone reservoir A, the water injection volume of the multi-period water flooding experiment was designed to be 2000 times the core pore volume. The experimental data showed that after injecting 30 times the core pore volume, there were 5 metering points where the cumulative oil production increased. Therefore, the experiment of this embodiment was divided into 6 periods, as shown in Table 1. The flow properties of the water phase reservoir in each period were calculated using the experimental data as follows: Figure 3 shown.

[0086] Table 1 Results of multi-period water flooding experiment in water flooding sandstone reservoir A

[0087]

[0088] like Figure 1 As shown in Figure 2, the cumulative comprehensive strength multiple is used in S2 to calculate the water drive intensity of each stage.

[0089] Among them, the value of the cumulative comprehensive strength multiple is calculated using formula B:

[0090]

[0091] Where: G is the cumulative comprehensive strength multiple, dimensionless; q w is the flow rate of injected water, cm 3 / s; V p is the pore volume of the core, cm 3 ; q(t) is the liquid flow rate at the core outlet end face at time t, cm 3 / s; Δp(t) is the displacement pressure difference at time t, MPa, q0 is the liquid flow rate at the core outlet end face in the initial pure oil flow stage, cm 3 / s; Δp0 is the displacement pressure difference in the initial pure oil flow stage, MPa.

[0092] The calculation results of water flooding intensity at each stage of water flooding sandstone reservoir A are shown in Table 2.

[0093] Table 2 Calculation results of water flooding strength in water flooding sandstone reservoirs

[0094]

[0095] like Figure 1 As shown, S3. A model of reservoir flow properties changing with water drive intensity is established to characterize the changes in reservoir flow properties.

[0096] like Figure 4 As shown, the specific steps of S3 include:

[0097] S31, draw a scatter plot of oil and gas saturation and cumulative comprehensive intensity multiples in each period, and obtain the first relationship through regression;

[0098] S32, calculating the effective permeability of the fluid by the phase permeability value obtained from the last period of testing to characterize the flow properties of the reservoir;

[0099] S33, through the relationship between fluid effective permeability and oil and gas saturation, the second relationship is obtained by regression;

[0100] S34. Combine the first relationship and the second relationship to obtain a mathematical model that characterizes the change of reservoir flow properties with water drive intensity.

[0101] In this embodiment, the mathematical model for characterizing the change of the flow properties of the water phase reservoir with the water flooding intensity of the A water flooding sandstone reservoir is shown in Formula C.

[0102]

[0103] Where: S o is the oil saturation, dimensionless; G is the cumulative comprehensive strength multiple, dimensionless; K w is the effective permeability of the water phase, that is, the flow properties of the water phase reservoir, mD.

[0104] In summary, the changes in reservoir flow properties of A water-flooded sandstone reservoir were characterized based on water-flooding intensity.

[0105] The present invention provides an application method for characterizing results of changes in reservoir flow properties, the method comprising: a judgment process, in an oil and gas reservoir numerical model, for judging whether the water injection volume multiple of an oil and gas reservoir grid is greater than 30 times the injected pore volume; a marking process, for marking the oil and gas reservoir model grids whose judgment results are greater than and calculating the cumulative comprehensive strength multiples; a calculation process, for calculating the value of the grid reservoir flow property; an output process, for outputting the reservoir flow property of each grid in the oil and gas reservoir numerical model under current conditions, for iterative calculation of a numerical simulator, and guiding the deployment of oil and gas field development adjustment.

[0106] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for characterizing changes in reservoir flow properties based on water flooding intensity, characterized in that: The specific steps include: S1. Carry out multi-period waterflooding experiments to calculate the reservoir flow properties at different stages; S2. Calculate the water drive strength at each stage using the cumulative comprehensive strength multiple; S3. Establish a model for the change of reservoir flow properties with water drive intensity to characterize the change of reservoir flow properties.

2. A method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 1, characterized in that: The multi-period waterflooding experiment adopts a continuous waterflooding process to realize the calculation of the reservoir flow properties corresponding to any metering point with an incremental cumulative oil production within the final waterflooding multiple.

3. The method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 1, characterized in that: In S1, when the final water injection volume set in the experiment is reached and the oil production has no increment compared with the previous cumulative oil production increment measurement point at the end of the final water flooding, the previous period is regarded as the last period.

4. The method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 1, characterized in that: The specific steps of S1 include: S11, setting the final water drive multiple; S12, continuously injecting water into the core, measuring the volume of water injected during this process and the corresponding cumulative oil production, cumulative liquid production and displacement pressure difference, and calculating the corresponding water drive multiple; S13, determining whether the injected water volume reaches the set value; When the injected water volume reaches the set value, the water drive multiple, cumulative oil production, cumulative liquid production and displacement pressure difference are recorded, the effective permeability of the water phase is calculated, and this period is recorded as the first period, i=1 is recorded, and step S14 is entered; When the injected water volume does not reach the set value, repeat step S12; S14, judging whether the cumulative oil production has an increase; When it is determined that the cumulative oil production has increased, the process proceeds to step S15; When it is judged that the cumulative oil production has no increase, re-judge; S15, record the corresponding water drive multiple; S16, determining whether the difference between the water drive multiple currently recorded in S15 and the water drive multiple last recorded is not less than 10; When the judgment condition is met, i=i+1, the water drive multiple is rounded up to ten, the current period is recorded as the i-th period, the cumulative oil production, cumulative liquid production and displacement pressure difference at this time are measured, the effective permeability of the water phase is calculated, and the process goes to step S17; When the judgment condition is not met, the two time periods are merged, the smaller time period number is counted, and the process returns to step S15; S17, judging whether the final water drive multiple set in the experiment has been reached; When the conditions are met, the overall cumulative oil production, cumulative liquid production, displacement pressure difference are measured, the effective permeability of the water phase for the entire period is calculated, and the process is terminated; When the condition is not met, return to step S12. S18. Calculate the effective permeability of each phase fluid based on experimental data.

5. A method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 4, characterized in that: The set value of the S13 injected water volume is 30 times the core pore volume.

6. The method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 1, characterized in that: The reservoir flow property in S1 is the effective permeability of each phase of fluid involved in the flow. The calculation formula of effective permeability is as follows: K i =K ri ·K o0 (S wc ) Where: i is a phase of fluid that is flowing, such as oil, gas, or water; K i is the effective permeability of phase i fluid, mD; K ri is the relative permeability of phase i fluid, dimensionless; K o0 (S wc ) is the effective permeability of the oil phase at the irreducible water saturation measured before the water flooding experiment, mD.

7. The method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 1, characterized in that: In S2, the water drive strength of each stage is calculated by using the cumulative comprehensive strength multiple. The calculation formula of the cumulative comprehensive strength multiple value is as follows: Where: G is the cumulative comprehensive strength multiple, dimensionless; q w is the flow rate of injected water, cm 3 / s; V p is the pore volume of the core, cm 3 ; q(t) is the liquid flow rate at the core outlet end face at time t, cm 3 / s; Δp(t) is the displacement pressure difference at time t, MPa, q0 is the liquid flow rate at the core outlet end face in the initial pure oil flow stage, cm 3 / s; Δp0 is the displacement pressure difference in the initial pure oil flow stage, MPa.

8. The method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 1, characterized in that: The specific steps of S3 include: S31, draw a scatter plot of oil and gas saturation and cumulative comprehensive intensity multiples in each period, and obtain the first relationship through regression; S32, calculating the effective permeability of the fluid by the phase permeability value obtained from the last period of testing to characterize the flow properties of the reservoir; S33, through the relationship between fluid effective permeability and oil and gas saturation, the second relationship is obtained by regression; S34. Combine the first relationship and the second relationship to obtain a mathematical model that characterizes the change of reservoir flow properties with water drive intensity.

9. A method for characterizing changes in reservoir flow properties based on water flooding intensity according to claim 8, characterized in that: The oil and gas saturation refers to the oil saturation at the last incremental measurement point of cumulative oil production before injecting 30 times the pore volume, the increased oil saturation in each period and the ultimate residual oil saturation in the last period. The effective fluid permeability refers to the effective permeability of each phase fluid corresponding to the oil and gas saturation.

10. An application method for characterizing changes in reservoir flow properties based on water flooding intensity, using the characterization method described in any one of claims 1 to 9, characterized in that: include: The judgment process is used to judge whether the water injection volume multiple of the oil and gas reservoir grid is greater than 30 times the injected pore volume in the oil and gas reservoir numerical model; A marking process is used to mark the oil and gas reservoir model grids with a judgment result of being greater than and calculate the cumulative comprehensive strength multiple; A computational process for calculating values ​​of grid reservoir flow properties; The output process is used to output the reservoir flow properties of each grid in the numerical model of the oil and gas reservoir under current conditions, which is used for iterative calculations of the numerical simulator and to guide the deployment of oil and gas field development adjustments.

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