Detection method for simulating damage degree of reinjection sewage to reservoir

Abstract

The invention relates to the technical field of oilfield development, in particular to a method for detecting the damage degree of simulated reinjection sewage to a reservoir, which comprises the following steps: acquiring microstructure data; making a visual rock core model; respectively detecting pollutant components in the reinjection sewage and the corresponding content of each pollutant component; the method comprises the following steps: respectively preparing single simulated sewage of a single pollutant component and composite simulated sewage of a composite pollutant component; respectively and independently injecting single simulation sewage and composite simulation sewage; detecting blockage characteristic data in the visual rock core model; calculating the variable quantity of the permeability before and after the visual core model is blocked; adjusting the injection speed of the single simulation sewage or the composite simulation sewage according to the maximum vibration amplitude of the visual rock core model; pollutant components causing blockage are determined by comparing the variable quantity of the permeability, and the proportion data and the blockage removal radius data of the blockage remover are determined. According to the invention, the accuracy of the detection result is improved.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a method for detecting the degree of damage to reservoirs caused by simulated reinjected sewage. Background Art

[0002] In the prior art, in order to maintain sufficient formation energy and give the reservoir a strong driving force and fluid supply capacity during oil extraction, most oil fields adopt water injection development for production. In order to meet the requirements of relevant national environmental protection laws and regulations and meet the needs of sustainable development of water resources, the produced fluid is usually separated into oil and water, and the treated wastewater is injected back into the reservoir, which not only replenishes the formation energy but also reduces or avoids the discharge of wastewater. Since the injected wastewater contains impurities such as polymers, suspended matter, and crude oil, it causes oil layer pollution, permeability and porosity to decrease, and the injection and production capacity of oil and water wells also decreases, affecting the development effect.

[0003] Chinese Patent Publication No.: CN111577243A discloses a method for evaluating reservoir damage caused by polymers in oilfield reinjection wastewater, comprising the following steps: (1) simulating the preparation of formation water used in the experiment according to the formation water data of the oilfield; (2) using the obtained simulated formation water to prepare solutions with polymer concentrations of 50, 100, 150, and 200 mg / L; (3) conducting a core flow experiment, injecting the obtained solutions into artificial cores with air permeabilities of 100, 200, 300, 400, and 500 mD, respectively, and calculating the permeability loss rate; (4) using the software 1stopt to establish a mathematical equation for the internal relationship between the permeability loss rate, injection volume, polymer concentration and air permeability; (5) using the obtained equation to evaluate the damage value and degree of the polymer to a reservoir with a specific air permeability under a certain injection volume and injected polymer concentration. If the permeability loss rate is greater than 30%, the polymer has caused great damage to the reservoir, and if the permeability loss rate exceeds 50%, the damage is serious. It can be seen that the method for evaluating reservoir damage caused by polymers in oilfield reinjection wastewater has the problem of reduced accuracy of detection results due to the inability to clearly determine the migration and blockage of pollutant components within the core during wastewater displacement experiments. Summary of the invention

[0004] To this end, the present invention provides a method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage, so as to overcome the problem in the prior art that the accuracy of the detection results is reduced due to the inability to clearly determine the migration and blockage of pollutant components inside the core.

[0005] To achieve the above object, the present invention provides a method for detecting the degree of damage to a reservoir caused by simulated reinjected sewage, comprising:

[0006] Tomography of reservoir core samples to obtain microstructural data;

[0007] Produce a visual core model based on the microstructure data;

[0008] Respectively detect the pollutant components and the corresponding content of each pollutant component in the reinjected sewage;

[0009] According to the pollutant components and the corresponding contents, single simulated sewage of a single pollutant component and composite simulated sewage of composite pollutant components are prepared respectively;

[0010] Injecting the single simulated sewage and the composite simulated sewage into the visualized core model separately;

[0011] Respectively detecting the blocking characteristic data of the single pollutant component and the composite pollutant component inside the visualized core model;

[0012] According to the pressure change of the sewage injection during the injection of the single simulated sewage or the composite simulated sewage, the change in the permeability of the single simulated sewage and the composite simulated sewage before and after the blockage of the visualized core model is calculated respectively;

[0013] According to the maximum vibration amplitude of the visualized core model during the injection of the single simulated sewage or the composite simulated sewage, the injection speed of the single simulated sewage and the composite simulated sewage are respectively adjusted accordingly;

[0014] The pollutant components causing the blockage are determined according to the change in permeability before and after the blockage, and the proportion data of the blockage-removing agent and the blockage-removing radius data are determined according to the pollutant components causing the blockage and the blockage characteristic data.

[0015] Furthermore, the microstructure data includes pore throat types existing in the reservoir core sample, pore throat structure data corresponding to each pore throat type, and pore radius structure data.

[0016] Furthermore, the process of making a visual core model includes:

[0017] vectorizing the microstructure data into a microstructure map;

[0018] Making a mask according to the microstructure diagram;

[0019] Covering the mask on a transparent substrate;

[0020] wet-etching the transparent substrate according to the microstructure map;

[0021] After removing the mask, a transparent cover is mounted on the etched transparent substrate and sealed to obtain the visualized core model.

[0022] Furthermore, the process of detecting the pollutant components in the reinjected wastewater includes:

[0023] detecting the size of polymer molecules in the reinjected wastewater;

[0024] The suspended matter in the reinjected sewage is dissolved, and the constituent elements and solid matter types of the suspended matter are detected.

[0025] Furthermore, the corresponding contents of the pollutant components include the molecular concentration of the polymer, the concentration of each of the constituent elements, the content of each solid substance and the oil content in the reinjected sewage;

[0026] The content of each solid substance is the ratio of the sum of the product of the concentration of each element in the solid substance and the relative atomic mass of the element to the original mass of the suspended matter.

[0027] Further, the process of respectively detecting the blockage characteristic data of the single pollutant component and the composite pollutant component inside the visualized core model includes:

[0028] Injecting a single simulated sewage containing the polymer, a single simulated sewage containing the suspended matter, and a single simulated sewage containing crude oil into the visualized core model respectively, and injecting a composite simulated sewage containing the polymer, the suspended matter, and the crude oil into the visualized core model;

[0029] The blocking characteristic data of various pollutant components during the flow inside the visualized core model are recorded.

[0030] Furthermore, the process of calculating the change in permeability of the visualized core model before and after plugging includes:

[0031] Respectively detecting the pressure changes per unit time of the single simulated sewage and the composite simulated sewage during the process of being injected into the visualized core model;

[0032] Calculating the permeability of the single simulated sewage or the composite simulated sewage according to the pressure change;

[0033] Obtaining the initial permeability of the initially injected single simulated sewage or the composite simulated sewage and the blocked permeability when blockage occurs;

[0034] Calculate the change in permeability of the visualized core model before and after plugging according to the initial permeability and the plugging permeability corresponding to the single simulated sewage or the composite simulated sewage;

[0035] Wherein, the change in permeability is the difference between the initial permeability and the blocked permeability;

[0036] Among them, the pressure change is the difference between the injection pressure of the single simulated sewage or the composite simulated sewage at the end time of the unit time and the injection pressure of the single simulated sewage or the composite simulated sewage at the start time of the unit time.

[0037] Further, the process of adjusting the injection speed of the single simulated sewage or the composite simulated sewage includes:

[0038] Acquire the maximum vibration amplitude per unit time of the visualized core model during the injection process of the single simulated sewage or the composite simulated sewage;

[0039] If the maximum vibration amplitude is greater than the preset maximum vibration amplitude, it is determined that the permeability detection accuracy does not meet the requirements, and the injection speed of the single simulated sewage or the composite simulated sewage is reduced;

[0040] Wherein, the reduction amplitude of the injection speed of the single simulated sewage or the composite simulated sewage is positively correlated with the maximum vibration amplitude.

[0041] Furthermore, the reservoir core sample is a natural core of the layer where the reinjected sewage is injected.

[0042] Furthermore, the process of determining the pollutant component causing the blockage according to the change in permeability before and after the blockage, and determining the proportion data of the blockage-removing agent and the blockage-removing radius data according to the pollutant component causing the blockage and the blockage characteristic data includes:

[0043] respectively calculating the difference between the change in permeability of a number of the single simulated sewage and the change in permeability of the composite simulated sewage;

[0044] Screening out the single simulated sewage with the smallest difference between the change in permeability of the single simulated sewage and the change in permeability of the composite simulated sewage;

[0045] Obtaining the pollutant components, corresponding contents of the pollutant components and the clogging characteristic data in the screened single simulated sewage;

[0046] Calculating the proportion data of the components of the blocking remover according to the pollutant components and the corresponding contents of the pollutant components in the screened single simulated sewage;

[0047] Determine the unblocking radius data according to the blocking characteristic data;

[0048] The unblocking radius data is the pore radius of the blocking point.

[0049] Compared with the prior art, the beneficial effect of the present invention lies in that the method of the present invention digitizes the complex, three-dimensional, and interlaced pore structure inside the natural core by constructing a visual core model, thereby improving the accuracy of simulating the core pore structure, analyzing the degree of damage of sewage to reservoir rocks through visualization technology, and detecting the interaction process between sewage and reservoir rocks in real time, analyzing the blockage mechanism from a microscopic perspective, thereby achieving accurate display of the blockage situation and damage degree of the reservoir; by repeatedly using the manufactured visual core model, comparing the degree of blockage damage of the core model by different pollutant components, reducing the error of the detection result caused by the heterogeneity of the natural core, and achieving improvement in the simulation accuracy of the visual core model; by analyzing the change in permeability before and after blockage of the visual core model, the degree of damage to the reservoir core is quantified, and then the type and distribution of the blockage are determined, thereby achieving improvement in the detection accuracy of the microscopic blockage mechanism of the reservoir by reinjected sewage.

[0050] Furthermore, the method of the present invention enhances the accuracy of physical and chemical reactions of reservoir cores during simulated sewage reinjection by making a visual core model, and digitizes the complex, three-dimensional, and interlaced pore structure inside natural cores by performing tomographic scanning on reservoir core samples, thereby providing a basic guarantee for the produced visual chip model to truly simulate the core pore structure, and improves the accuracy of detection and experimental efficiency by intuitively observing the degree of damage. The visual core model structure is easy to copy and can be used for repeated detection multiple times, thereby enhancing the reliability of the detection results.

[0051] Furthermore, the method of the present invention detects the composition and content of pollutants in the reinjected wastewater, and detects polymers, suspended matter, and crude oil components in the reinjected wastewater to detect the characteristics of the reinjected wastewater from a microscopic perspective. By detecting the degree of damage to the reservoir caused by different pollutant components of polymers, suspended matter, and crude oil in the comparative experiment, the error in the experimental results caused by the heterogeneity of the natural core can be reduced or eliminated, thereby achieving an improvement in the accuracy of the detection of reinjected wastewater characteristics.

[0052] Furthermore, the method of the present invention quantifies the degree of damage to the reservoir core caused by the reinjected wastewater by calculating the change in permeability before and after plugging and by comparing the permeability data before and after plugging. At the same time, it provides data for the long-term operation of the oil and gas field, increases the stability of oil and gas production, and improves the accuracy of the test results by experimentally testing the visualized core model, thereby further achieving an improvement in the effectiveness of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is an overall flow chart of a method for detecting the degree of damage to a reservoir caused by reinjected sewage according to an embodiment of the present invention;

[0054] Figure 2 A microscopic structure diagram of a natural core of a reservoir in a method for detecting the degree of damage to a reservoir caused by reinjected sewage in an embodiment of the present invention;

[0055] Figure 3 The mask diagram of the method for detecting the degree of damage to the reservoir caused by the reinjected sewage according to the embodiment of the present invention;

[0056] Figure 4 This is a transparent substrate after etching in the method for detecting the degree of damage to the reservoir caused by the reinjected sewage according to the embodiment of the present invention;

[0057] Figure 5 A visualized core model diagram of a method for detecting the degree of damage to a reservoir caused by reinjected wastewater according to an embodiment of the present invention;

[0058] Figure 6 This is a microscopic picture of the method for detecting the degree of damage to the reservoir caused by the reinjected sewage according to the embodiment of the present invention after the injection of the simulated sewage X13-copy;

[0059] Figure 7 This is a pore throat characteristic diagram of the blockage point after the injection of simulated sewage X13-copy according to the method for detecting the degree of reservoir damage caused by reinjected sewage in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0061] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0062] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0063] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] See also Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 as well as Figure 7 As shown, they are respectively an overall flow chart of the method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to an embodiment of the present invention, a microstructure diagram of the natural core of the reservoir, a mask diagram, a transparent substrate diagram after etching, a visualized core model diagram, a microscopic diagram after injecting simulated sewage X13-copy, and a pore throat characteristic diagram of the blocked point after injecting simulated sewage X13-copy. A method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to the present invention comprises:

[0065] Tomography of reservoir core samples to obtain microstructural data;

[0066] Produce a visual core model based on the microstructure data;

[0067] Respectively detect the pollutant components and the corresponding content of each pollutant component in the reinjected sewage;

[0068] According to the pollutant components and the corresponding contents, single simulated sewage of a single pollutant component and composite simulated sewage of composite pollutant components are prepared respectively;

[0069] Injecting the single simulated sewage and the composite simulated sewage into the visualized core model separately;

[0070] Respectively detecting the blocking characteristic data of the single pollutant component and the composite pollutant component inside the visualized core model;

[0071] According to the pressure change of the sewage injection during the injection of the single simulated sewage or the composite simulated sewage, the change in the permeability of the single simulated sewage and the composite simulated sewage before and after the blockage of the visualized core model is calculated respectively;

[0072] According to the maximum vibration amplitude of the visualized core model during the injection of the single simulated sewage or the composite simulated sewage, the injection speed of the single simulated sewage and the composite simulated sewage are respectively adjusted accordingly;

[0073] The pollutant components causing the blockage are determined according to the change in permeability before and after the blockage, and the proportion data of the blockage-removing agent and the blockage-removing radius data are determined according to the pollutant components causing the blockage and the blockage characteristic data.

[0074] Specifically, the blockage characteristic data include the migration distance of single simulated sewage or composite simulated sewage during the flow inside the visualized core model, the pore throat structure of the blockage point, the pore radius of the blockage point, and the change in porosity before and after blockage.

[0075] In practice, the method of the present invention digitizes the complex, three-dimensional, and interlaced pore structure inside the natural core by constructing a visual core model, thereby improving the accuracy of simulating the core pore structure, analyzing the degree of damage to the reservoir rock caused by sewage through visualization technology, and detecting the interaction process between sewage and reservoir rock in real time, analyzing the blockage mechanism from a microscopic perspective, thereby achieving an accurate display of the blockage situation and the degree of damage to the reservoir; by repeatedly using the manufactured visual core model, comparing the degree of blockage damage to the core model caused by different pollutant components, reducing the error of the detection result caused by the heterogeneity of the natural core, and achieving an improvement in the simulation accuracy of the visual core model; by analyzing the change in permeability before and after the blockage of the visual core model, the degree of damage to the reservoir core is quantified, and then the type and distribution of the blockage are determined, thereby achieving an improvement in the detection accuracy of the microscopic blockage mechanism of the reservoir caused by the reinjected sewage.

[0076] Specifically, the microstructure data includes pore throat types existing in the reservoir core sample, pore throat structure data corresponding to each pore throat type, and pore radius structure data.

[0077] Specifically, the microstructural data were obtained by monitoring with an ultra-high resolution imager.

[0078] Specifically, the pore throat types include neck throats, point throats, sheet or curved sheet throats, and bundle throats.

[0079] Specifically, the pore-throat structure data include pore-throat distribution density, connection direction, and pore-throat radius.

[0080] Specifically, the pore radius structure data includes pore radius, pore length, and porosity.

[0081] Specifically, the reservoir core samples are scanned by computer tomography (CT) to obtain the microstructure of the reservoir core. The scanning accuracy of computer tomography (CT) is 500nm, and the size of the reservoir core is Φ2.5cm×5cm.

[0082] Specifically, the process of making a visual core model includes:

[0083] vectorizing the microstructure data into a microstructure map;

[0084] Making a mask according to the microstructure diagram;

[0085] Covering the mask on a transparent substrate;

[0086] wet-etching the transparent substrate according to the microstructure map;

[0087] After removing the mask, a transparent cover is mounted on the etched transparent substrate and sealed to obtain the visualized core model.

[0088] Specifically, the vectorization process of vectorizing the microstructure data into the microstructure map is to map the microstructure data to the graphic attributes of the microstructure map and draw the microstructure map according to the graphic attributes.

[0089] Specifically, according to the pore throat types existing in the reservoir core samples obtained by CT scanning, the pore throat structure data corresponding to each pore throat type, and the pore radius structure data, the transparent substrate is etched by wet etching to obtain a visual core model consistent with the microscopic pore throat structure and pore radius of the reservoir core.

[0090] Specifically, the microstructure diagram is a CAD structure diagram.

[0091] In implementation, the method of the present invention enhances the accuracy of physical and chemical reactions of reservoir cores during simulated sewage reinjection by making a visual core model, and digitizes the complex, three-dimensional, and interlaced pore structure inside the natural core by performing tomographic scanning on reservoir core samples, thereby providing a basic guarantee for the produced visual chip model to truly simulate the core pore structure, and improves the accuracy of detection and experimental efficiency by intuitively observing the degree of damage. The structure of the visual core model is easy to copy and can be repeatedly tested, thereby enhancing the reliability of the test results.

[0092] Specifically, the process of detecting pollutant components in reinjected wastewater includes:

[0093] detecting the size of polymer molecules in the reinjected wastewater;

[0094] The suspended matter in the reinjected sewage is dissolved, and the constituent elements and solid matter types of the suspended matter are detected.

[0095] Specifically, the corresponding contents of the pollutant components include the molecular concentration of the polymer, the concentration of each of the constituent elements, the content of each solid substance, and the oil content in the reinjected sewage;

[0096] The content of each solid substance is the ratio of the sum of the product of the concentration of each element in the solid substance and the relative atomic mass of the element to the original mass of the suspended matter.

[0097] Specifically, the starch-cadmium iodide method is used to detect the concentration of polymers in the reinjected sewage. The dynamic light scattering method is used to detect the molecular size of polymers in the reinjected sewage. The membrane filter constant weight method is used to detect the concentration of suspended matter in the reinjected sewage. The laser particle size analyzer is used to detect the particle size of suspended matter in the reinjected sewage. The surface photoelectron energy spectrum analyzer and X-ray diffraction analyzer are used to determine the elemental composition and solid matter type of the suspended matter. The suspended matter is dissolved, and the inductively coupled plasma emission spectrometer is used to determine the concentration of the elements and the content of the solid matter is estimated. The spectrophotometry method is used to detect the oil content in the reinjected sewage.

[0098] Specifically, solid matter types include silt, metal oxides, etc.

[0099] In implementation, the method of the present invention detects the composition and content of pollutants in the reinjected wastewater, and detects polymers, suspended matter, and crude oil components in the reinjected wastewater to detect the characteristics of the reinjected wastewater from a microscopic perspective. By detecting the degree of damage to the reservoir caused by different pollutant components of polymers, suspended matter, and crude oil in the comparative experiment, the error in the experimental results caused by the heterogeneity of the natural core can be reduced or eliminated, thereby achieving an improvement in the accuracy of the detection of reinjected wastewater characteristics.

[0100] Specifically, the process of respectively detecting the blocking characteristic data of the single pollutant component and the composite pollutant component inside the visualized core model includes:

[0101] Injecting a single simulated sewage containing the polymer, a single simulated sewage containing the suspended matter, and a single simulated sewage containing crude oil into the visualized core model respectively, and injecting a composite simulated sewage containing the polymer, the suspended matter, and the crude oil into the visualized core model;

[0102] The blocking characteristic data of various pollutant components during the flow inside the visualized core model are recorded.

[0103] Specifically, the process of calculating the change in permeability before and after the blockage of the visualized core model includes:

[0104] Respectively detecting the pressure changes per unit time of the single simulated sewage and the composite simulated sewage during the process of being injected into the visualized core model;

[0105] Calculating the permeability of the single simulated sewage or the composite simulated sewage according to the pressure change;

[0106] Obtaining the initial permeability of the initially injected single simulated sewage or the composite simulated sewage and the blocked permeability when blockage occurs;

[0107] Calculate the change in permeability of the visualized core model before and after plugging according to the initial permeability and the plugging permeability corresponding to the single simulated sewage or the composite simulated sewage;

[0108] Wherein, the change in permeability is the difference between the initial permeability and the blocked permeability;

[0109] Among them, the pressure change is the difference between the injection pressure of the single simulated sewage or the composite simulated sewage at the end time of the unit time and the injection pressure of the single simulated sewage or the composite simulated sewage at the start time of the unit time.

[0110] Specifically, the injection pressure of the simulated sewage is detected by a pressure sensor at the injection port.

[0111] In implementation, the method of the present invention calculates the change in permeability before and after plugging, and quantifies the degree of damage to the reservoir core caused by the reinjected wastewater by comparing the permeability data before and after plugging. At the same time, it provides data for the long-term operation of the oil and gas field, increases the stability of oil and gas production, and improves the accuracy of the test results by experimentally testing the visualized core model, thereby further achieving an improvement in the effectiveness of the test.

[0112] Specifically, the process of adjusting the injection speed of the single simulated sewage or the composite simulated sewage includes:

[0113] Acquire the maximum vibration amplitude per unit time of the visualized core model during the injection process of the single simulated sewage or the composite simulated sewage;

[0114] If the maximum vibration amplitude is greater than the preset maximum vibration amplitude, it is determined that the permeability detection accuracy does not meet the requirements, and the injection speed of the single simulated sewage or the composite simulated sewage is reduced;

[0115] Wherein, the reduction amplitude of the injection speed of the single simulated sewage or the composite simulated sewage is positively correlated with the maximum vibration amplitude.

[0116] Specifically, the maximum vibration amplitude is detected by a laser vibrometer.

[0117] In implementation, the general value range of the preset maximum vibration amplitude is [12 μm, 15 μm].

[0118] Preferably, the preset maximum vibration amplitude is 14 μm.

[0119] Specifically, when the difference between the maximum vibration amplitude and the preset maximum vibration amplitude is less than 1 μm, the injection speed of the simulated sewage is reduced by 0.02 ml / min; when the difference between the maximum vibration amplitude and the preset maximum vibration amplitude exceeds 1, the injection speed of the simulated sewage is reduced by 0.04 ml / min for every 1 μm exceeding it. For example, when the maximum vibration amplitude is 18 μm, the injection speed of the simulated sewage is 0.34 ml / min, and the injection speed of the simulated sewage is reduced to 0.34 ml / min-0.02 ml / min-0.04 ml / min×3=0.2 ml / min

[0120] Specifically, the reservoir core samples are natural cores of the layers where the reinjected wastewater is injected.

[0121] Specifically, the process of determining the pollutant component causing the blockage according to the change in permeability before and after the blockage, and determining the proportion data of the blockage-removing agent and the blockage-removing radius data according to the pollutant component causing the blockage and the blockage characteristic data includes:

[0122] respectively calculating the difference between the change in permeability of a number of the single simulated sewage and the change in permeability of the composite simulated sewage;

[0123] Screening out the single simulated sewage with the smallest difference between the change in permeability of the single simulated sewage and the change in permeability of the composite simulated sewage;

[0124] Obtaining the pollutant components, corresponding contents of the pollutant components and the clogging characteristic data in the screened single simulated sewage;

[0125] Calculating the proportion data of the components of the blocking remover according to the pollutant components and the corresponding contents of the pollutant components in the screened single simulated sewage;

[0126] Determine the unblocking radius data according to the blocking characteristic data;

[0127] The unblocking radius data is the pore radius of the blocking point.

[0128] Specifically, the components of the required unblocking agent and the mass of the components of each unblocking agent are output according to the pollutant components in the screened single simulated sewage, the corresponding contents of the pollutant components and the corresponding unblocking reaction equation.

[0129] Specifically, the ratio data of the components of the plugging remover is the ratio of the mass of each component of the plugging remover to the total mass of the plugging remover.

[0130] The following takes the research on reservoir damage caused by the reinjection of wastewater in Block X of Daqing Oilfield as an example to illustrate the effect of implementing the method of the present invention.

[0131] Embodiment 1, as Figure 2 , Figure 3 , Figure 4 as well as Figure 5 As shown, they are respectively a microstructure diagram of a natural core of a reservoir, a mask diagram, a transparent substrate diagram after etching, and a visualized core model diagram of a method for detecting the degree of damage to a reservoir caused by reinjected sewage in an embodiment of the present invention.

[0132] A natural core with a size of Φ2.5cm×5cm was selected from the injection layer of the reinjected sewage in Block X. The core was scanned using a computed tomography (CT) scanner with a scanning accuracy of 500nm to obtain the pore throat type and pore radius of the natural core of the reservoir in Block X. The microscopic pore structure data of the core obtained by CT scanning was vectorized and converted into a CAD structure diagram, and then a mask was made according to the CAD structure diagram; the mask was covered on a transparent substrate, and the transparent substrate was etched by wet etching to obtain a model consistent with the microscopic pore throat structure and pore radius of the reservoir core; the mask was removed, and the transparent cover was installed on the etched transparent substrate, and sealed to obtain a visualized core model.

[0133] The on-site injection water from the three injection wells in Block X was taken and the concentration of polymers in the samples was detected by starch-cadmium iodide method. The molecular size of polymers in the reinjected wastewater was detected by dynamic light scattering method. The test results are shown in Table 1.

[0134] Table 1- Results of polymer testing in the field injected water of three injection wells in Block X

[0135] Water Sample X6 X7 X13 Concentration (mg / L) 236.98 250.74 188.55 Average molecular size (nm) 167 116 54

[0136] The concentration of suspended matter in the reinjected sewage was detected by the membrane constant weight method. The particle size of suspended matter in the reinjected sewage was detected by a laser particle size analyzer. The elemental composition and solid matter type of the suspended matter were determined by a surface photoelectron spectrometer and an X-ray diffraction analyzer. The suspended matter was dissolved and the concentration of the elements was determined by an inductively coupled plasma emission spectrometer to estimate the content of solid matter. The test results are shown in Table 2.

[0137] Table 2-X Block 3 injection wells on-site injection water suspended matter detection results

[0138]

[0139]

[0140] The oil content in the reinjected wastewater was tested by spectrophotometry. The test results are shown in Table 3.

[0141] Table 3- Results of crude oil testing in the field injected water of three injection wells in Block X

[0142] Water Sample X6 X7 X13 Concentration (mg / L) 324.68 463.82 241.19

[0143] The composition and content of pollutants in the reinjected wastewater can be obtained from Tables 2 and 3.

[0144] Embodiment 2, as Figure 6 and Figure 7 As shown, they are respectively a microscopic image after the injection of simulated sewage X13-copy and a pore throat characteristic image of the blockage point after the injection of simulated sewage X13-copy according to the method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage in an embodiment of the present invention.

[0145] According to the detection results of suspended matter in the on-site reinjection sewage sample X13, simulated sewage X13-copy was prepared and injected into the visualized core model to observe the movement distance of the suspended matter inside the visualized core model. It can be seen from the figure that the suspended matter is more likely to accumulate at the entrance, and the migration route from the entrance to the exit is A→B→C→D. With the increase of the migration distance, the amount of suspended matter deposited in the pores is also getting lower and lower. Simulated sewage X13-copy was injected into the visualized core model, and the pore throat characteristics of the suspended matter blocking points inside the visualized core model were observed. It can be seen from the figure that the suspended matter is mainly blocked at the sheet throat point E and the point throat point F.

[0146] Example 3: Prepare simulated sewage with different suspended matter concentrations, inject the simulated sewage into the visualized core model, and monitor the injection pressure of the simulated sewage before and after the injection, and the changes in the porosity and permeability of the visualized core model.

[0147] Table 4 - Changes in porosity and permeability of the core model injected with simulated sewage of different suspended solids concentrations

[0148]

[0149] It can be seen from Table 4 that with the increase of suspended matter concentration, the injection pressure gradually increases, and the permeability and porosity gradually decrease.

[0150] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for detecting the degree of damage to a reservoir caused by simulated reinjection of wastewater, characterized in that: include: Tomography of reservoir core samples to obtain microstructural data; Produce a visual core model based on the microstructure data; Respectively detect the pollutant components and the corresponding content of each pollutant component in the reinjected sewage; According to the pollutant components and the corresponding contents, single simulated sewage of a single pollutant component and composite simulated sewage of composite pollutant components are prepared respectively; Injecting the single simulated sewage and the composite simulated sewage into the visualized core model separately; Respectively detecting the blocking characteristic data of the single pollutant component and the composite pollutant component inside the visualized core model; According to the pressure change of the sewage injection during the injection of the single simulated sewage or the composite simulated sewage, the change in the permeability of the single simulated sewage and the composite simulated sewage before and after the blockage of the visualized core model is calculated respectively; According to the maximum vibration amplitude of the visualized core model during the injection of the single simulated sewage or the composite simulated sewage, the injection speed of the single simulated sewage and the composite simulated sewage are respectively adjusted accordingly; The pollutant components causing the blockage are determined according to the change in permeability before and after the blockage, and the proportion data of the blockage-removing agent and the blockage-removing radius data are determined according to the pollutant components causing the blockage and the blockage characteristic data.

2. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 1 is characterized in that: The microstructure data include pore throat types existing in the reservoir core sample, pore throat structure data corresponding to each pore throat type, and pore radius structure data.

3. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 2 is characterized in that: The process of making a visual core model includes: vectorizing the microstructure data into a microstructure map; Making a mask according to the microstructure diagram; Covering the mask on a transparent substrate; wet-etching the transparent substrate according to the microstructure map; After removing the mask, a transparent cover is mounted on the etched transparent substrate and sealed to obtain the visualized core model.

4. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 3 is characterized in that: The process of detecting pollutants in the reinjected wastewater includes: detecting the size of polymer molecules in the reinjected wastewater; The suspended matter in the reinjected sewage is dissolved, and the constituent elements and solid matter types of the suspended matter are detected.

5. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 4 is characterized in that: The corresponding contents of the pollutant components include the molecular concentration of the polymer, the concentration of each of the constituent elements, the content of each solid substance and the oil content in the reinjected sewage; The content of each solid substance is the ratio of the sum of the product of the concentration of each element in the solid substance and the relative atomic mass of the element to the original mass of the suspended matter.

6. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 5 is characterized in that: The process of respectively detecting the blocking characteristic data of the single pollutant component and the composite pollutant component inside the visualized core model includes: Injecting a single simulated sewage containing the polymer, a single simulated sewage containing the suspended matter, and a single simulated sewage containing crude oil into the visualized core model respectively, and injecting a composite simulated sewage containing the polymer, the suspended matter, and the crude oil into the visualized core model; The blocking characteristic data of various pollutant components during the flow inside the visualized core model are recorded.

7. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 6 is characterized in that: The process of calculating the change in permeability before and after the plugging of the visualized core model includes: Respectively detecting the pressure changes per unit time of the single simulated sewage and the composite simulated sewage during the process of being injected into the visualized core model; Calculating the permeability of the single simulated sewage or the composite simulated sewage according to the pressure change; Obtaining the initial permeability of the initially injected single simulated sewage or the composite simulated sewage and the blocked permeability when blockage occurs; Calculate the change in permeability of the visualized core model before and after plugging according to the initial permeability and the plugging permeability corresponding to the single simulated sewage or the composite simulated sewage; Wherein, the change in permeability is the difference between the initial permeability and the blocked permeability; Among them, the pressure change is the difference between the injection pressure of the single simulated sewage or the composite simulated sewage at the end time of the unit time and the injection pressure of the single simulated sewage or the composite simulated sewage at the start time of the unit time.

8. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 7 is characterized in that: The process of adjusting the injection speed of the single simulated sewage or the composite simulated sewage comprises: Acquire the maximum vibration amplitude per unit time of the visualized core model during the injection process of the single simulated sewage or the composite simulated sewage; If the maximum vibration amplitude is greater than the preset maximum vibration amplitude, it is determined that the permeability detection accuracy does not meet the requirements, and the injection speed of the single simulated sewage or the composite simulated sewage is reduced; Wherein, the reduction amplitude of the injection speed of the single simulated sewage or the composite simulated sewage is positively correlated with the maximum vibration amplitude.

9. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 8 is characterized in that: The reservoir core samples are natural cores of the layers where the reinjected wastewater is injected.

10. The method for detecting the degree of damage to the reservoir caused by simulated reinjected sewage according to claim 9, characterized in that: The process of determining the pollutant component causing the blockage according to the change in permeability before and after the blockage, and determining the proportion data of the blockage-removing agent and the blockage-removing radius data according to the pollutant component causing the blockage and the blockage characteristic data includes: respectively calculating the difference between the change in permeability of a number of the single simulated sewage and the change in permeability of the composite simulated sewage; Screening out the single simulated sewage with the smallest difference between the change in permeability of the single simulated sewage and the change in permeability of the composite simulated sewage; Obtaining the pollutant components, corresponding contents of the pollutant components and the clogging characteristic data in the screened single simulated sewage; Calculating the proportion data of the components of the blocking remover according to the pollutant components and the corresponding contents of the pollutant components in the screened single simulated sewage; Determine the unblocking radius data according to the blocking characteristic data; The unblocking radius data is the pore radius of the blocking point.

Images