Oil field production water reinjection numerical simulation method and system

Abstract

The invention relates to the technical field of oil field water treatment, and provides an oil field production water reinjection numerical simulation method and system.The method comprises the steps that a rock core sample of a reinjection target layer is collected, and experimental reinjection water and distilled water are prepared; carrying out a five-sensitivity experiment on the target layer rock core and reinjection water to obtain sensitive parameters; selecting sensitive parameters having great influence on the reservoir permeability, and establishing an influence characterization mathematical model; introducing the influence characterization mathematical model into a numerical simulation method for characterization, and establishing a numerical model considering the influence of the reinjection water on the permeability of the target reservoir; and carrying out oil field scale reinjection water effect simulation based on the numerical model. According to the method, the accuracy of permeability damage rate calculation can be improved, the influence of injected water on the reservoir is comprehensively considered, and the permeability of the reservoir can be better managed and optimized.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield water treatment, and in particular to a numerical simulation method and system for oilfield produced water reinjection. Background Art

[0002] After the oil field development enters the middle and late stages, the reservoir pressure drops greatly, and water injection is an important means to maintain the reservoir pressure. In multiple oil production operations, the liquid produced from the oil well is separated into oil and water phases through a separator, and the oil phase is transported to the oil transfer station, while the water phase is transported to the sewage treatment station. Sewage generally contains a certain amount of oil, sulfide, organic phenol, cyanide, bacteria, solid particles, and chemical agents such as demulsifiers, flocculants and bactericides. The discharge of a large amount of produced water not only causes environmental pollution, but also wastes precious water resources. Therefore, the reinjection of oil production wastewater after treatment has become an important way to reduce environmental pollution, ensure the sustainable development of oil fields, and improve the economic benefits of oil fields.

[0003] During the development of oil reservoirs, reinjected water has a significant impact on reservoir parameters, especially the change in reservoir permeability, which significantly affects the results of reservoir numerical simulation, the distribution of remaining oil and the understanding of recovery rate. However, existing studies have not clearly pointed out the specific factors that affect the change in permeability, so it is difficult to fully evaluate whether a certain oil recovery effect can be achieved after the reinjection of produced water and the actual impact on the development effect of the oil field. In traditional reservoir numerical simulation methods, the relative permeability curve is usually static and fails to reflect the dynamic changes in reservoir parameters and seepage laws under the conditions of produced water reinjection. This makes it difficult to conduct simulation studies and it is impossible to accurately quantify the distribution of remaining oil in the reservoir when produced water is reinjected. This problem directly affects the accuracy of the oil field in improving the ultimate recovery rate.

[0004] In a Chinese patent application with application publication number CN 109838220 A, a method for evaluating the reinjection index of produced water in an oilfield is disclosed, the evaluation method comprising: obtaining water quality information of produced water in the oilfield and water injection parameter information at different reinjection times, the water injection parameter information comprising injection pressure and injection volume; using the injection pressure and injection volume, obtaining a first water absorption index of the target reservoir in the early stage of water injection and a second water absorption index in the late stage of water injection; obtaining a plurality of core samples from the target reservoir to carry out a core damage experiment, obtaining a first permeability damage rate caused by velocity sensitivity and a second permeability damage rate caused by injection volume; when the water quality information meets the preset standard, the second water absorption index is greater than or equal to the first water absorption index, and the first permeability damage rate and the second permeability damage rate are both less than or equal to the preset value, the reinjection index of the produced water in the oilfield meets the requirements. Regarding the above-mentioned oilfield produced water reinjection index evaluation method used in this patent, through a comprehensive analysis of the water quality of oilfield produced water, the degree of damage of oilfield produced water to the permeability of the target reservoir, and the water absorption performance of the target reservoir, the oilfield produced water reinjection index can be comprehensively and effectively evaluated, and then the oilfield produced water reinjection index can be determined and optimized; however, the method mainly focuses on the first and second permeability damage rates caused by velocity sensitivity and injection volume, and may ignore other factors that may cause damage.

[0005] In the Chinese patent application with application publication number CN 104179499 A, a numerical simulation method considering the time-varying reservoir parameters is provided, which includes: step 1, establishing a numerical simulation model of the reservoir, and in each iterative calculation process of the numerical simulation of the reservoir, according to the attribute parameters of each grid block of the numerical simulation model of the reservoir, a set of new data fields of water injection flushing multiples are calculated; step 2, establishing a relationship model of the reservoir permeability changing with the water injection flushing multiples, and correcting the dynamic change range of the static parameters of the reservoir model from time to time during the iterative calculation process; step 3, calculating the time-varying law of the relative permeability curve based on the change of physical properties, and describing the relative permeability curve of each grid in the iterative calculation; and step 4, after obtaining the relative permeability curve, using it to calculate the law of oil and water movement in each iterative time step. The use of this improved numerical simulation method can effectively reflect the phenomenon that the reservoir parameters of the reservoir change with the change of the water injection flushing multiples, thereby ensuring the reliability of the numerical simulation results of the reservoir, and then providing a reasonable reference basis for the adjustment and optimization of the oilfield development plan. However, the method is used for multi-layer water-drive reservoirs with high recovery rates and is not suitable for the special case of produced water reinjection in oil reservoirs. Summary of the invention

[0006] The purpose of the present invention is to solve at least one technical problem in the background technology and to provide a method and system for numerical simulation of oilfield produced water reinjection.

[0007] To achieve the above object, the present invention provides a numerical simulation method for oilfield produced water reinjection, comprising:

[0008] Collect core samples from the target layer for reinjection and prepare reinjection water and distilled water for the experiment;

[0009] Conduct five-sensitivity experiments on the target layer core and reinjection water to obtain sensitive parameters;

[0010] Select sensitive parameters that have a greater impact on reservoir permeability and establish a mathematical model to characterize the impact;

[0011] The mathematical model for characterizing the impact is introduced into the numerical simulation method for characterization, and a numerical model considering the impact of reinjection water on the permeability of the target reservoir is established;

[0012] Based on the numerical model, a simulation of the effect of water reinjection on an oilfield scale is carried out.

[0013] According to one aspect of the present invention, the five-sensitivity experiment is carried out on the target layer core and the reinjection water to obtain the sensitive parameters, including:

[0014] Through velocity-sensitive experiments, the core of the target layer and the reinjected water were tested to determine the velocity-sensitive index that affects the reservoir permeability;

[0015] The alkaline sensitivity test was conducted on the target layer core and reinjection water to determine the alkaline sensitivity index that affects the reservoir permeability;

[0016] Water sensitivity tests were conducted on the target layer core and reinjected water to determine the water sensitivity index that affects the reservoir permeability;

[0017] Compatibility tests are conducted on formation water and reinjection water to determine whether scaling occurs when reinjection water meets formation water.

[0018] According to one aspect of the present invention, the speed-sensitive experiment is:

[0019] (1) Place the fully saturated core sample into the core holder so that the flow direction of the liquid in the sample is consistent with the flow direction of the gas when measuring the gas permeability, and ensure that no air is left in the system during the entire experiment. Then slowly adjust the confining pressure to 2.0 MPa. During the test, always keep the confining pressure value greater than the core inlet pressure by 1.5-2.0 MPa;

[0020] (2) According to 0.10cm 3 / min, 0.2cm 3 / min, 0.50cm 3 / min, 0.75cm 3 / min, 1.0cm 3 / min、1.5cm 3 / min, 2.0cm3 / min、3.0cm 3 / min, 4.0cm 3 / min, 5.0cm 3 / min and 6.0cm 3 The permeability was measured successively at the liquid flow rate of / min;

[0021] (3) Measure pressure, flow rate, time and temperature, and after the flow state becomes stable, record the test data and determine the speed sensitivity index based on the test data;

[0022] The alkali sensitivity test is:

[0023] (1) Preparation of different alkali solutions: Starting from a pH value of 7.0, adjust the pH value of the potassium chloride solution and increase the pH value of the alkali solution by 1-1.5 pH values ​​until the pH value reaches 13.0;

[0024] (2) Use potassium chloride solution with the same mineralization as formation water to measure the initial permeability, inject alkali solution with adjusted pH value into the rock sample, displace 10-15 times the pore volume of the rock sample, stop displacement, and allow the alkali solution to fully react with the rock minerals for more than 12 hours; then use the alkali solution with the same pH value to displace and measure the liquid permeability. The alkali solution injection sequence is from low to high. During the experiment, the experimental flow rate adopts the speed-sensitive test results. Repeat the above specified operations until the pH value is increased to 13.0;

[0025] (3) Measure pressure, flow rate, time and temperature, and after the flow state becomes stable, record the test data and determine the alkali sensitivity index based on the test data;

[0026] Water sensitivity test:

[0027] (1) The experimental flow rate adopts the speed-sensitive test result;

[0028] (2) Using the initial test fluid to determine the initial liquid permeability of the core sample, after determining the initial liquid permeability of the core sample, displace it with the intermediate test fluid, with the displacement speed being consistent with the initial flow rate, displacing 10 to 15 times the pore volume of the rock sample, stopping the displacement, keeping the confining pressure and temperature constant, and allowing the intermediate test fluid to fully react with the rock minerals for more than 12 hours; adjusting the displacement pump flow rate to the initial flow rate, and then displacing with the intermediate test fluid to determine the core permeability; the same method is used to carry out the distilled water displacement experiment, and determine the permeability of the core sample under distilled water;

[0029] (3) Measure pressure, flow rate, time and temperature, and after the flow state becomes stable, record the test data and determine the water sensitivity index based on the test data;

[0030] Compatibility test:

[0031] (1) The experimental flow rate adopts the speed-sensitive test result;

[0032] (2) Experimental process:

[0033] Dynamic evaluation: The reinjection water and formation water are compounded in a volume ratio of 5:5, 4:6, 3:7, 2:8, and 1:9, and fluid displacement tests are carried out under constant speed and temperature conditions to analyze the impact of the combined effect of the reinjection water and formation water on the reduction in pore permeability, thereby determining their scaling conditions.

[0034] According to one aspect of the present invention, the sensitive parameters with greater impact on reservoir permeability are selected to establish an impact characterization mathematical model as follows:

[0035] Select sensitive parameters with a sensitivity index of more than 30% and construct a mathematical model to characterize their impact:

[0036] α=β·f 1 (v) f 2 (PH)·f 3 (k)·f 4 (pv);

[0037] In the formula, α represents the impact characterization value, which is used to quantify the influence of reservoir sensitivity on permeability; β is the unknown coefficient of the mathematical model; f 1 (v) is the volume sensitive parameter, f 2 (PH) is the acid-base sensitive parameter, f 3 (k) is the flow sensitive parameter, f 4 (pv) is the pressure sensitive parameter.

[0038] According to one aspect of the present invention, the method of introducing the impact characterization mathematical model into the numerical simulation method for characterization and establishing a numerical model that considers the impact of reinjection water on the permeability of the target reservoir includes:

[0039] Establish the governing equations that take into account the absolute permeability variation;

[0040] The control equations are differentially discretized to obtain the numerical simulation conductivity;

[0041] establishing a numerical model based on the conductivity;

[0042] Among them, permeability is reflected in conductivity in numerical simulation, and permeability is a function of the mathematical model.

[0043] To achieve the above object, the present invention also provides an oilfield produced water reinjection numerical simulation system, comprising:

[0044] Experiment preparation module, collects core samples of the target layer for reinjection, and prepares reinjection water and distilled water for the experiment;

[0045] Sensitive parameter acquisition module, which conducts five-sensitivity experiments on the target layer core and reinjection water to obtain sensitive parameters;

[0046] The impact characterization mathematical model construction module selects sensitive parameters that have a greater impact on reservoir permeability and establishes an impact characterization mathematical model;

[0047] The numerical model building module introduces the impact characterization mathematical model into the numerical simulation method for characterization, and establishes a numerical model that considers the impact of reinjection water on the permeability of the target reservoir;

[0048] The numerical simulation module carries out simulation of the effect of water reinjection on the scale of oilfield based on the numerical model.

[0049] To achieve the above objectives, the present invention also provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the numerical simulation method for oilfield produced water reinjection as described above.

[0050] To achieve the above objectives, the present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the above-mentioned oilfield produced water reinjection numerical simulation method is implemented.

[0051] According to the scheme of the present invention, the present invention can improve the accuracy of permeability damage rate calculation: by collecting fluid and core data of the target layer, and conducting experiments to obtain parameters related to reservoir sensitivity. By summarizing the change law of reservoir physical properties, the permeability damage rate is calculated, and parameters with an impact of more than 30% are selected. Careful analysis and calculation enable the model to more accurately capture the behavior of the reservoir and improve the accuracy of predicting permeability changes.

[0052] The present invention comprehensively considers the impact of injected water on the reservoir: the impact equation of injected water on reservoir physical properties is introduced into the numerical simulator. By establishing an impact characterization mathematical model, multiple influencing factors are comprehensively considered, which helps to more comprehensively understand the impact of injected water on reservoir permeability. The comprehensive model enables oilfield developers to better manage and optimize reservoir permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A flowchart schematically showing a numerical simulation method for oilfield produced water reinjection according to an embodiment of the present invention;

[0054] Figure 2 Schematically showing the effect of velocity on permeability according to one embodiment of the present invention;

[0055] Figure 3A diagram schematically showing the effect of pH value on permeability according to one embodiment of the present invention;

[0056] Figure 4 A diagram schematically showing the effect of mineralization on permeability according to an embodiment of the present invention;

[0057] Figure 5 and Figure 6 The figure schematically shows the influence of the injection volume PV number on the permeability according to one embodiment of the present invention. DETAILED DESCRIPTION

[0058] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only to enable those skilled in the art to better understand and thus implement the present invention, rather than implying any limitation on the scope of the present invention.

[0059] As used herein, the term “including” and variations thereof are to be interpreted as open-ended terms meaning “including, but not limited to.” The term “based on” is to be interpreted as “based, at least in part, on.” The terms “one embodiment” and “an embodiment” are to be interpreted as “at least one embodiment.”

[0060] Figure 1 The flowchart schematically shows a numerical simulation method for oilfield produced water reinjection according to one embodiment of the present invention. Figure 1 As shown, in this embodiment, the numerical simulation method for oilfield produced water reinjection includes:

[0061] Collect core samples from the target layer for reinjection and prepare reinjection water and distilled water for the experiment;

[0062] Conduct five-sensitivity experiments on the target layer core and reinjection water to obtain sensitive parameters;

[0063] Select sensitive parameters that have a greater impact on reservoir permeability and establish a mathematical model to characterize the impact;

[0064] The mathematical model for characterizing the impact is introduced into the numerical simulation method for characterization, and a numerical model considering the impact of reinjection water on the permeability of the target reservoir is established;

[0065] Based on the numerical model, a simulation of the effect of water reinjection on an oilfield scale is carried out.

[0066] Further, according to an embodiment of the present invention, five sensitivity experiments are carried out on the target layer core and the reinjection water to obtain sensitive parameters, including:

[0067] Through velocity-sensitive experiments, the core of the target layer and the reinjected water were tested to determine the velocity-sensitive index that affects the reservoir permeability;

[0068] The alkaline sensitivity test was conducted on the target layer core and reinjection water to determine the alkaline sensitivity index that affects the reservoir permeability;

[0069] Water sensitivity tests were conducted on the target layer core and reinjected water to determine the water sensitivity index that affects the reservoir permeability;

[0070] Compatibility tests are conducted on formation water and reinjection water to determine whether scaling occurs when reinjection water meets formation water.

[0071] Further, according to one embodiment of the present invention, since tiny solid particles in the rock pores will adhere to the particles of the skeleton, when the flow rate is extremely low, the fluid's impulse is insufficient to remove them and move them, so the reservoir rock is not sensitive at extremely low flow rates. However, as the flow rate increases, the fluid's impulse also increases. When the flow rate exceeds a certain limit, the fluid's impulse exceeds its adhesion, the particles fall off and begin to move, and finally stay in the pore throat and block the pores, thereby reducing the permeability of the rock and causing the reservoir to become sensitive. The minimum flow rate that produces sensitivity is determined through speed-sensitive experiments to avoid damage to the formation caused by particle migration, and to determine a reasonable injection and production rate while helping to protect the oil and gas layers. Two parameters are used to evaluate speed sensitivity. One is the critical flow rate, which reflects the difficulty of destroying the clay microstructure. The higher the critical flow rate, the more stable the clay microstructure; the other is the degree of permeability reduction after particle migration occurs (i.e., the damage rate).

[0072] In this embodiment, the speed-sensitive experiment is:

[0073] (1) Place the fully saturated core sample into the core holder so that the flow direction of the liquid in the sample is consistent with the flow direction of the gas when measuring the gas permeability, and ensure that no air is left in the system during the entire experiment. Then slowly adjust the confining pressure to 2.0 MPa. During the test, always keep the confining pressure value greater than the core inlet pressure by 1.5-2.0 MPa;

[0074] (2) According to 0.10cm 3 / min, 0.2cm 3 / min, 0.50cm 3 / min, 0.75cm 3 / min, 1.0cm 3 / min、1.5cm 3 / min, 2.0cm 3 / min、3.0cm 3 / min, 4.0cm 3 / min, 5.0cm 3 / min and 6.0cm 3 / min liquid flow rate is measured in turn to measure the permeability (if the permeability decreases significantly with the decrease of the injected water salinity, it indicates that the reservoir is water sensitive.); the appropriate initial test flow rate and flow rate interval can also be selected according to the air permeability of the rock sample. For low-permeability dense rock samples, when the flow rate has not yet reached 6.0cm 3 / min. If the pressure gradient is greater than 2MPa / cm, the experiment can be terminated;

[0075] (3) Measure pressure, flow rate, time and temperature. After the flow state becomes stable, record the test data and determine the velocity sensitivity index based on the test data. Figure 2 shown.

[0076] In this embodiment, in the velocity-sensitive experiment, the variation of core permeability with flow velocity is obtained by detecting data such as pressure, flow rate, and temperature, and then the velocity-sensitive index is determined. The determination method includes:

[0077] 1. Calculate the permeability. According to Darcy's law (where Q is the flow rate, K is the permeability, A is the cross-sectional area of ​​the core, △P is the pressure difference, μ is the fluid viscosity, and L is the core length). During the experiment, the geometric dimensions of the core (A and L) and the fluid viscosity μ are known. By measuring the flow rate Q and the pressure difference △P, the permeability K of the core at different flow rates can be calculated.

[0078] 2. Determine K min and K max In this experiment with different flow rate variations, the permeabilities calculated at different flow rates are compared. max It is the maximum value of permeability within the experimental flow rate range, which represents the maximum permeability of the core under experimental conditions. min It is the minimum value of permeability, which is usually the result of permeability reduction due to damage such as particle migration caused by excessive flow rate.

[0079] 3. Calculate the speed sensitivity index. Using the formula To calculate the speed sensitivity index.

[0080] Further, according to one embodiment of the present invention, alkali sensitivity refers to the phenomenon that the external alkaline liquid reacts with the minerals in the reservoir to disperse, fall off or generate new precipitation or colloidal substances, block the pore throat, and cause the permeability of the reservoir to change. The pH value of the formation fluid is generally distributed in 4-9. If the pH value of the external fluid entering the reservoir is too high or too low, it will cause the incompatibility of the external fluid and the reservoir. The purpose of the alkali sensitivity evaluation experiment is to understand whether the various alkali solutions entering the well cause damage to the reservoir and the extent of the damage. According to current research, the main mechanisms of alkali-sensitive damage are: ① Alkaline working fluid induces the dispersion of clay minerals, causing structural instability. ② High pH alkali solution has a dissolving effect on cat soil minerals and minerals such as quartz and feldspar, which reacts with kaolinite to form montmorillonite, causing further damage to the reservoir.

[0081] In this embodiment, the alkali sensitivity test is:

[0082] (1) Preparation of different alkali solutions: Starting from a pH value of 7.0, adjust the pH value of the potassium chloride solution and increase the pH value of the alkali solution by 1-1.5 pH values ​​until the pH value reaches 13.0;

[0083] (2) Use potassium chloride solution with the same mineralization as formation water to measure the initial permeability, inject alkali solution with adjusted pH value into the rock sample, displace 10-15 times the pore volume of the rock sample, stop displacement, and allow the alkali solution to fully react with the rock minerals for more than 12 hours; then use the alkali solution with the same pH value to displace and measure the liquid permeability. The alkali solution injection sequence is from low to high. During the experiment, the experimental flow rate uses the speed sensitivity test result (the speed sensitivity test result is the obtained speed sensitivity index. The speed sensitivity degree of the reservoir can be divided according to the size of the speed sensitivity index. It can provide a basis for reasonably determining the injection speed. For example, for a highly speed-sensitive reservoir, the injection speed should be strictly controlled at a low level to avoid a significant drop in permeability.) Repeat the above specified operations until the pH value is increased to 13.0;

[0084] (3) Measure pressure, flow rate, time and temperature. After the flow state becomes stable, record the test data and determine the alkali sensitivity index based on the test data. The influence of pH value on permeability is as follows: Figure 3 shown.

[0085] In this embodiment, the alkali sensitivity index (I b ) is usually calculated using the following formula:

[0086]

[0087] Among them, K i is the initial permeability of the core, K min It is the minimum permeability after treatment with alkali solution.

[0088] Further, according to one embodiment of the present invention, the purpose of water sensitivity evaluation is to understand the phenomenon that when the mineralization of the external fluid is incompatible with the clay minerals in the reservoir, the clay minerals are hydrated, expanded, dispersed, and migrated, resulting in a decrease in reservoir permeability. The purpose of the water sensitivity experiment is to evaluate the maximum degree of change in reservoir rock permeability caused by clay expansion or particle migration. The level of clay mineral content directly affects the strength of reservoir water sensitivity. In addition, the factors that affect the degree of damage to reservoir water sensitivity are not only related to the type and content of clay minerals, but also depend on the distribution pattern of dynamic earth minerals in the formation and the porosity of the formation. Through the water sensitivity experiment, it is determined whether the reinjected formation is water-sensitive to the produced water and harms the formation.

[0089] In this embodiment, the water sensitivity test is:

[0090] (1) The experimental flow rate adopts the speed-sensitive test result;

[0091] (2) The initial test fluid is used to determine the initial liquid permeability of the core sample. After determining the initial liquid permeability of the core sample, it is displaced with an intermediate test fluid (brine, used to simulate formation water with different salinities). The displacement speed is consistent with the initial flow rate. 10-15 times the pore volume of the rock sample is displaced. The displacement is stopped and the confining pressure and temperature are kept constant to allow the intermediate test fluid to fully react with the rock minerals for more than 12 hours. The displacement pump flow rate is adjusted to the initial flow rate, and the intermediate test fluid is used for displacement again to determine the core permeability. The distilled water displacement experiment is carried out in the same way, and the permeability of the core sample under distilled water is determined.

[0092] (3) Measure pressure, flow rate, time and temperature, and record the test data after the flow state becomes stable; the influence of mineralization on permeability is as follows: Figure 4 shown.

[0093] In this embodiment, the water sensitivity index is determined by measuring the change in core permeability under the action of injected water of different salinities. Permeability data is a key indicator for determining reservoir water sensitivity. The determination method is usually calculated using the following formula:

[0094]

[0095] Among them, K i is the initial permeability of the core, K min It is the minimum value of the core permeability during the process of mineralization reduction, that is, the permeability measured by the distilled water.

[0096] Furthermore, according to one embodiment of the present invention, during multi-layer mining, the produced fluids from different layers have poor compatibility, and CaSO is easily generated after mixing. 4 ,BaSO 4 、SrSO 4The formation will be clogged due to precipitation, which will cause corrosion and scaling of pipelines outside the station and facilities inside the station, thus facing a series of problems such as the rising costs of personnel and equipment depreciation. In order to solve the above problems, it is necessary to study the compatibility of produced water. Formation water and reinjection water are injected at the same flow rate at the same time, and the relationship between the PV number of different injection volumes and the permeability Kr of the rock sample is measured to determine whether scaling occurs when the produced water (reinjection water) meets the formation water, thereby causing damage to the formation. The influence of the injection volume PV number on the permeability is as follows: Figure 5 and Figure 6 shown.

[0097] In this embodiment, the compatibility test is:

[0098] (1) The experimental flow rate adopts the speed-sensitive test result;

[0099] (2) Experimental process:

[0100] Dynamic evaluation: The reinjection water and formation water are compounded in a volume ratio of 5:5, 4:6, 3:7, 2:8, and 1:9, and fluid displacement tests are carried out under constant speed and temperature conditions to analyze the impact of the combined effect of the reinjection water and formation water on the reduction in pore permeability, thereby determining their scaling conditions.

[0101] Further, according to an embodiment of the present invention, sensitive parameters with a greater impact on reservoir permeability are selected to establish an impact characterization mathematical model as follows:

[0102] Based on the above experimental results, the permeability damage rate is calculated, and the effects of production water injection rate, salinity and water injection multiple on permeability damage are comprehensively considered to establish a more accurate evaluation model. According to the standard "SY / T 5358-2010 Reservoir Sensitivity Flow Experiment Evaluation Method", sensitive parameters with a sensitivity index exceeding 30% are selected to construct a mathematical model for impact characterization:

[0103] α=β·f 1 (v) f 2 (PH)·f 3 (k)·f 4 (pv);

[0104] In the formula, α represents the impact characterization value, which is used to quantify the influence of reservoir sensitivity on permeability; β is the unknown coefficient of the mathematical model; f 1 (v) is the volume sensitive parameter, f 2 (PH) is the acid-base sensitive parameter, f 3 (k) is the flow sensitive parameter, f 4 (pv) is the pressure sensitive parameter.

[0105] Multiple experiments were conducted under the same conditions, ensuring that the initial and operating conditions were the same for each experiment. The experimental data were linked to the mathematical model and the value of the coefficient β was determined using statistical methods.

[0106] Further, according to an embodiment of the present invention, the impact characterization mathematical model is introduced into the numerical simulation method for characterization, and a numerical model considering the impact of reinjection water on the permeability of the target reservoir is established, including:

[0107] Establish the governing equations that take into account the absolute permeability variation;

[0108] The control equations are differentially discretized to obtain the numerical simulation conductivity;

[0109] establishing a numerical model based on the conductivity;

[0110] Among them, permeability is reflected in conductivity in numerical simulation, and permeability is a function of the mathematical model.

[0111] In this embodiment, starting from the equation of motion, the equation of state, and the continuity equation, a control equation considering the change of absolute permeability is established:

[0112] Oil phase:

[0113]

[0114] Aqueous phase:

[0115]

[0116] Taking the oil phase control equation as an example, it is differentially discretized and expanded into the component form in the Cartesian rectangular coordinate system:

[0117]

[0118] Taking (i, j, k, n+1) as the research point, the differential equation is established:

[0119]

[0120] The subscripts in the above formula are in simplified format, such as represent Since the study is based on the (i, j, k, n+1) grid block, multiply the two segments of the above formula by their volumes, that is, V ijk =Δx i Δy j Δz k , in order to facilitate the expression of the equation, the following conduction coefficient is defined:

[0121]

[0122] Continue to define the second-order difference quotient operator as:

[0123]

[0124] The oil phase differential dispersion equation can be simplified as:

[0125]

[0126] It can be further simplified as:

[0127]

[0128] Permeability is reflected in conductivity in numerical simulation. Take the conductivity of the oil phase in the X direction as an example:

[0129]

[0130] Permeability is a function of α. Here, α is displayed, that is, the α of the nth step is taken to calculate the absolute permeability of the n+1th step, and then the conductivity of the n+1th step is obtained, that is:

[0131]

[0132] According to the above scheme of the present invention, the present invention can improve the accuracy of permeability damage rate calculation: by collecting fluid and core data of the target layer, and conducting experiments to obtain parameters related to reservoir sensitivity. By summarizing the change law of reservoir physical properties, the permeability damage rate is calculated, and parameters with an impact of more than 30% are selected. Careful analysis and calculation enable the model to more accurately capture the behavior of the reservoir and improve the accuracy of predicting permeability changes.

[0133] The present invention comprehensively considers the impact of injected water on the reservoir: the impact equation of injected water on reservoir physical properties is introduced into the numerical simulator. By establishing an impact characterization mathematical model, multiple influencing factors are comprehensively considered, which helps to more comprehensively understand the impact of injected water on reservoir permeability. The comprehensive model enables oilfield developers to better manage and optimize reservoir permeability.

[0134] Furthermore, to achieve the above-mentioned purpose, the present invention also provides an oilfield produced water reinjection numerical simulation system, comprising:

[0135] Experiment preparation module, collects core samples of the target layer for reinjection, and prepares reinjection water and distilled water for the experiment;

[0136] Sensitive parameter acquisition module, which conducts five-sensitivity experiments on the target layer core and reinjection water to obtain sensitive parameters;

[0137] The impact characterization mathematical model construction module selects sensitive parameters that have a greater impact on reservoir permeability and establishes an impact characterization mathematical model;

[0138] The numerical model building module introduces the impact characterization mathematical model into the numerical simulation method for characterization, and establishes a numerical model that considers the impact of reinjection water on the permeability of the target reservoir;

[0139] The numerical simulation module carries out simulation of the effect of water reinjection on the scale of oilfield based on the numerical model.

[0140] The oilfield produced water reinjection numerical simulation system according to the present invention can implement the above-mentioned oilfield produced water reinjection numerical simulation method. The specific process steps are as described above and will not be repeated here.

[0141] Furthermore, to achieve the above objectives, the present invention also provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the numerical simulation method for oilfield production water reinjection as described above is implemented.

[0142] Furthermore, to achieve the above-mentioned purpose, the present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the above-mentioned oilfield produced water reinjection numerical simulation method is implemented.

[0143] Based on the above solution of the present invention, the solution of the present invention is described in detail in the following in combination with the accompanying drawings in the form of a specific embodiment.

[0144] Example 1

[0145] Taking the second section of the corner of Well WZ12-8-1 as an example, the following research was carried out by taking formation plunger core samples and using the A2 water of the 12-1C platform as the reinjection water.

[0146] The numerical simulation method of oilfield produced water considering reinjection water provided in this embodiment considers the influence of oilfield produced water reinjection on reservoir physical parameters, with the purpose of establishing a numerical simulation model (numerical model) considering various influencing factors.

[0147] The total mineralization of A2 water is close to 35500-36500 mg / L, which is CaCl 2 Type water, Ca 2+ and Mg 2+ SO4 2- The content is close.

[0148] Speed ​​sensitivity test:

[0149] The basic information of the speed-sensitive test samples is shown in Table 1:

[0150] Core number Horizon Length cm Diametercm Gas permeability md <![CDATA[Pore volume cm 3 > Porosity% WZ12-8-2-3 Corner Section 2 10.176 2.5 2520.911 20.087 40.213

[0151] Table 1

[0152] The results of the speed-sensitive experiment are shown in Table 2:

[0153]

[0154] Table 2

[0155] Alkali sensitivity test:

[0156] The basic information of the alkali sensitivity test samples is shown in Table 3:

[0157] Core number Horizon Length cm Diametercm Gas permeability md <![CDATA[Pore volume cm 3 > Porosity% WZ12-8-2-4 Corner Section 2 10.5 2.5 2432.472 20.03 38.881

[0158] Table 3

[0159] The results of the alkali sensitivity test are shown in Table 4:

[0160]

[0161] Table 4

[0162] Water sensitivity test:

[0163] The basic information of water sensitivity test samples is shown in Table 5:

[0164] Core number Horizon Length cm Diametercm Gas permeability md <![CDATA[Pore volume cm 3 > Porosity% WZ12-8-2-1 Corner Section 2 10.176 2.5 4208.522 21.020 40.194

[0165] Table 5

[0166] The results of the water sensitivity test are shown in Table 6:

[0167]

[0168] Table 6

[0169] Fluid compatibility test:

[0170] The basic information of the compatibility test samples is shown in Table 7:

[0171] Core number Horizon Length cm Diametercm Gas permeability md <![CDATA[Pore volume cm 3 > Porosity% WZ12-10-2(5)-3 Corner Section 2 10.5 2.54 2115.505 19.93 37.459

[0172] Table 7

[0173] Experimental parameter optimization and mathematical model establishment:

[0174] According to the experimental results, the permeability damage rate is calculated and the chart is drawn. The reservoir of the second section of the angle of WZ12-8 oilfield is weakly velocity-sensitive, moderately water-sensitive, weakly alkaline-sensitive, with a critical mineralization of 17g / L. The compatibility of A2 water and formation water is good and close, the damage rate is 13%, and the pressure of the displacement process tends to be stable. According to the above method of selecting sensitive parameters, the parameters for water sensitivity experiments are selected and other parameters are discarded.

[0175] α=β·f 1 (v) f 2 (PH)·f 3 (k)·f4 (pv);

[0176] The permeability change multiple of the WZ12-8 oilfield angle 2 reservoir is expressed as a function of fluid salinity:

[0177] f 3 =10 -10 k 3 -2×10 -6 k 2 +0.0135k+20;

[0178] Then β=1, and the mathematical formula for permeability is:

[0179] α=10 -10 k 3 -2×10 -6 k 2 +0.0135k+20;

[0180] Then the numerical model: K n+1 =α*K n ;

[0181] Finally, a field-scale study of the effect of water reinjection is conducted based on numerical models.

[0182] Those skilled in the art will appreciate that the modules and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0183] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and equipment can refer to the corresponding processes in the aforementioned method implementation methods, and will not be repeated here.

[0184] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0185] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the embodiments of the present invention.

[0186] In addition, each functional module in the embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0187] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the energy-saving signal sending / receiving method of each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, ROM, RAM, magnetic disks, or optical disks.

[0188] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

[0189] It should be understood that the size of the serial numbers of each step in the content of the invention and the implementation methods of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation methods of the present invention.

Claims

1. A numerical simulation method for oilfield produced water reinjection, characterized in that: include: Collect core samples from the target layer for reinjection and prepare reinjection water and distilled water for the experiment; Conduct five-sensitivity experiments on the target layer core and reinjection water to obtain sensitive parameters; Select sensitive parameters that have a greater impact on reservoir permeability and establish a mathematical model to characterize the impact; The mathematical model for characterizing the impact is introduced into the numerical simulation method for characterization, and a numerical model considering the impact of reinjection water on the permeability of the target reservoir is established; Based on the numerical model, a simulation of the effect of water reinjection on an oilfield scale is carried out.

2. The oilfield produced water reinjection numerical simulation method according to claim 1, characterized in that: The five-sensitivity experiment is carried out on the target layer core and reinjection water to obtain sensitive parameters, including: Through velocity-sensitive experiments, the core of the target layer and the reinjected water were tested to determine the velocity-sensitive index that affects the reservoir permeability; The alkaline sensitivity test was conducted on the target layer core and reinjection water to determine the alkaline sensitivity index that affects the reservoir permeability; Water sensitivity tests were conducted on the target layer core and reinjected water to determine the water sensitivity index that affects the reservoir permeability; Compatibility tests are conducted on formation water and reinjection water to determine whether scaling occurs when reinjection water meets formation water.

3. The oilfield produced water reinjection numerical simulation method according to claim 2, characterized in that: The speed-sensitive experiment is: (1) Place the fully saturated core sample into the core holder so that the flow direction of the liquid in the sample is consistent with the flow direction of the gas when measuring the gas permeability, and ensure that no air is left in the system during the entire experiment. Then slowly adjust the confining pressure to 2.0 MPa. During the test, always keep the confining pressure value greater than the core inlet pressure by 1.5-2.0 MPa; (2) According to 0.10cm 3 / min, 0.2cm 3 / min, 0.50cm 3 / min, 0.75cm 3 / min, 1.0cm 3 / min、1.5cm 3 / min, 2.0cm 3 / min、3.0cm 3 / min, 4.0cm 3 / min, 5.0cm 3 / min and 6.0cm 3 The permeability was measured successively at the liquid flow rate of / min; (3) Measure pressure, flow rate, time and temperature, and after the flow state becomes stable, record the test data and determine the speed sensitivity index based on the test data; The alkali sensitivity test is: (1) Preparation of different alkali solutions: Starting from a pH value of 7.0, adjust the pH value of the potassium chloride solution and increase the pH value of the alkali solution by 1-1.5 pH values ​​until the pH value reaches 13.0; (2) Use potassium chloride solution with the same mineralization as formation water to measure the initial permeability, inject alkali solution with adjusted pH value into the rock sample, displace 10-15 times the pore volume of the rock sample, stop displacement, and allow the alkali solution to fully react with the rock minerals for more than 12 hours; then use the alkali solution with the same pH value to displace and measure the liquid permeability. The alkali solution injection sequence is from low to high. During the experiment, the experimental flow rate adopts the speed-sensitive test results. Repeat the above specified operations until the pH value is increased to 13.0; (3) Measure pressure, flow rate, time and temperature, and after the flow state becomes stable, record the test data and determine the alkali sensitivity index based on the test data; The water sensitivity test is: (1) The experimental flow rate adopts the speed-sensitive test result; (2) Using the initial test fluid to determine the initial liquid permeability of the core sample, after determining the initial liquid permeability of the core sample, displace it with the intermediate test fluid, with the displacement speed being consistent with the initial flow rate, displacing 10 to 15 times the pore volume of the rock sample, stopping the displacement, keeping the confining pressure and temperature constant, and allowing the intermediate test fluid to fully react with the rock minerals for more than 12 hours; adjusting the displacement pump flow rate to the initial flow rate, and then displacing with the intermediate test fluid to determine the core permeability; the same method is used to carry out the distilled water displacement experiment, and determine the permeability of the core sample under distilled water; (3) Measure pressure, flow rate, time and temperature, and after the flow state becomes stable, record the test data and determine the water sensitivity index based on the test data; The compatibility test: (1) The experimental flow rate adopts the speed-sensitive test result; (2) Experimental process: Dynamic evaluation: The reinjection water and formation water are compounded in a volume ratio of 5:5, 4:6, 3:7, 2:8, and 1:9, and fluid displacement tests are carried out under constant speed and temperature conditions to analyze the impact of the combined effect of the reinjection water and formation water on the reduction in pore permeability, thereby determining their scaling conditions.

4. The oilfield produced water reinjection numerical simulation method according to claim 1, characterized in that: The sensitive parameters with greater influence on reservoir permeability are selected to establish the influence characterization mathematical model as follows: Select sensitive parameters with a sensitivity index of more than 30% and construct a mathematical model to characterize their impact: α=β·f1(v)·f2(PH)·f3(k)·f4(pv); Wherein, α represents the impact characterization value, which is used to quantify the influence of reservoir sensitivity on permeability; β is the unknown coefficient of the mathematical model; f1(v) is the volume sensitivity parameter, f2(PH) is the acid-base sensitivity parameter, f3(k) is the flow sensitivity parameter, and f4(pv) is the pressure sensitivity parameter.

5. The oilfield produced water reinjection numerical simulation method according to any one of claims 1 to 4, characterized in that: The method of introducing the influence characterization mathematical model into the numerical simulation method for characterization and establishing a numerical model considering the influence of reinjection water on the permeability of the target reservoir includes: Establish the governing equations that take into account the absolute permeability variation; The control equations are differentially discretized to obtain the numerical simulation conductivity; establishing a numerical model based on the conductivity; Among them, permeability is reflected in conductivity in numerical simulation, and permeability is a function of the mathematical model.

6. Oilfield produced water reinjection numerical simulation system, characterized by: include: Experiment preparation module, collects core samples of the target layer for reinjection, and prepares reinjection water and distilled water for the experiment; Sensitive parameter acquisition module, which conducts five-sensitivity experiments on the target layer core and reinjection water to obtain sensitive parameters; The impact characterization mathematical model construction module selects sensitive parameters that have a greater impact on reservoir permeability and establishes an impact characterization mathematical model; The numerical model building module introduces the impact characterization mathematical model into the numerical simulation method for characterization, and establishes a numerical model that considers the impact of reinjection water on the permeability of the target reservoir; The numerical simulation module carries out simulation of the effect of water reinjection on the scale of oilfield based on the numerical model.

7. An electronic device, characterized in that The method comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the method for numerical simulation of oilfield produced water reinjection as claimed in any one of claims 1 to 7 is implemented.

8. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for numerical simulation of oilfield produced water reinjection according to any one of claims 1 to 7 is implemented.

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