Oil recovery enhancement methods based on ternary composite emulsification and their applications

Abstract

This application relates to the field of oilfield technology, specifically to a method for enhancing oil recovery based on the emulsification effect of ternary composite flooding and its application. The method includes: determining the optimal ratio of ternary composite flooding under each type of reservoir condition; setting up monitoring points; analyzing the injection pressure variation characteristics of ternary composite flooding during the early injection void volume stage, combining the numerical deviation of the injection pressure to obtain necessity evaluation parameters, and determining the injection pressure control time and priority of the early injection pressure control targets; during the mid-stage injection void volume stage, analyzing the water cut changes at each monitoring point and control time during each injection process, determining emulsification evaluation indicators, determining adjustment coefficients, and obtaining the target injection rate at each pressure control time in the mid-stage. This application aims to adjust the injection strategy in real time to ensure that ternary composite flooding achieves optimal results at different stages, thereby effectively improving oil recovery.

Description

Technical Field

[0001] This application relates to the field of oilfield technology, specifically to a method for enhancing oil recovery based on ternary composite flooding emulsification and its application. Background Technology

[0002] Ternary composite flooding is a commonly used oil recovery technology. It involves adding different proportions of alkali (A), low concentrations of surfactant (S), and polymer (P) to the injection water to form an ASP composite system. The alkali enhances the thickening ability of the polymer, reacts with acids in the petroleum to produce surfactants that emulsify the oil, increasing the viscosity of the medium and allowing the polymer to effectively control fluid flow. The surfactant reduces the interfacial tension between oil and water. The polymer increases formation porosity and improves the relative permeability of oil and water. Through the synergistic effect of multiple displacement agents, the oil recovery rate is enhanced.

[0003] Emulsification is one of the recognized important mechanisms in ternary composite flooding oil recovery systems. The alkali and surfactant in ternary composite flooding are conducive to the occurrence of emulsification. After a large amount of residual oil comes into contact with the ternary fluid, an emulsification reaction occurs, forming an O / W or W / O type emulsion. The emulsion can effectively carry oil droplets of residual oil through the rock fissures, thereby improving the oil recovery rate.

[0004] When using ternary composite flooding to enhance oil recovery, traditional processes present problems in areas such as injection, scale prevention, and lift systems. For example, the degree of emulsification needs to match the reservoir characteristics, and the injection system cannot dynamically adjust the concentration of chemical agents. Excessive injection pressure caused by polymer blockage or over-emulsification, or uneven profile caused by significant interlayer heterogeneity, can lead to instability in the displacement effect of ternary composite flooding when different slugs are injected, resulting in the oil displacement effect of ternary composite flooding not meeting expectations. Summary of the Invention

[0005] In view of the above, it is necessary to provide a method for enhancing oil recovery based on ternary composite flooding emulsification and its application to solve the above problems.

[0006] The first aspect of this application provides a method for enhancing oil recovery based on ternary composite flooding emulsification, the method comprising:

[0007] By analyzing the effects of the relative molecular weight of the polymer, alkali concentration, and type of surfactant on emulsification, the optimal ratio of ternary composite flooding under each type of reservoir condition was determined.

[0008] Monitoring points are set up, and during the early injection void volume stage, the injection pressure variation characteristics of each monitoring point at each moment during each injection process of the ternary composite drive are analyzed to obtain the anomaly probability. The absolute value of the difference between the injection pressure at each monitoring point at each moment and the preset pressure is taken as the injection pressure deviation. Dividing it by the preset pressure, the deviation ratio is obtained. The anomaly probability and deviation ratio at each monitoring point at each moment are weighted respectively, and the weighted sum is used to obtain the necessity evaluation parameters at each monitoring point at each moment. Based on the necessity evaluation parameters, the injection pressure adjustment time is determined, and the priority of the early injection pressure adjustment object is determined.

[0009] During the mid-term injection void volume stage, the changes in water content at each monitoring point and at each control time during each injection of the ternary composite flooding were analyzed to determine the emulsification evaluation index at each monitoring point and at each time. The changes in injection pressure at each pressure control time at each monitoring point were compared with the changes in injection pressure at historical times. Based on the overall distribution of the emulsification evaluation index, the adjustment coefficient was determined to obtain the target injection rate at each pressure control time at each monitoring point during the mid-term.

[0010] The ternary composite drive is injected using a multi-segment plug method, wherein the multi-segment plug includes a front polymer segment plug, a ternary main segment plug, a ternary secondary segment plug, and a rear polymer protection segment plug.

[0011] Specifically, the abnormal probability is obtained as follows:

[0012] For each injection void volume, the pressure difference between the injection pressure at the next moment and the injection pressure at the previous moment is calculated for each monitoring point. The ratio of the pressure difference to the time interval is used as the pressure rise rate at the next moment. Anomaly detection is performed on the pressure rise rate at each moment for each monitoring point to obtain the anomaly probability.

[0013] The step of determining the injection pressure control time is as follows:

[0014] The prediction evaluation parameters for each moment are obtained by using the prediction algorithm based on the necessity evaluation parameters of each monitoring point at historical time.

[0015] When the difference between the predicted evaluation parameter and the necessity evaluation parameter at each time point is not zero, the corresponding time point is taken as the control time for injecting pressure.

[0016] The priority of the early injection pressure control object is determined by the correlation between the control object and the pressure rise rate at each monitoring point in historical time.

[0017] The process of determining the emulsification evaluation index at each monitoring point at each time point is specifically as follows:

[0018] For each monitoring point, the ratio obtained by dividing the difference between the moisture content at each time point and the moisture content at the previous time point by the moisture content at the previous time point is used as the emulsification evaluation index.

[0019] The specific method for obtaining the adjustment coefficient is as follows:

[0020] For each monitoring point, the numerical distribution characteristics of the pressure rise rate at each time point and previous time points are analyzed to determine the decreasing evaluation index for each monitoring point at each time point. The evaluation index representing the decrease of monitoring point a at time t;

[0021] The specific formula for the adjustment coefficient is as follows:

[0022]

[0023] In the formula, This represents the adjustment coefficient for monitoring point a at time t; This represents the emulsification evaluation index of monitoring point a at time t under each PV; This represents the maximum value of the emulsification evaluation index for monitoring point a under all PV conditions. This indicates that the rate of pressure rise is maintained greater than the initial rate of pressure rise from the initial time to time t. Duration This represents the rate of pressure increase at monitoring point a at the initial moment. represents the rate of pressure rise at monitoring point a at time t; exp() represents an exponential function with the natural constant as the base. This represents the injection pressure at monitoring point a at time t; This represents the maximum value of the injection pressure at monitoring point a at time t-1 in history; This represents the average rate of pressure rise at monitoring point a at time t-1 in history; This represents the average injection pressure at all historical moments of monitoring point a; Indicates the preset injection pressure; Represents logical operators.

[0024] Specifically, determining the decreasing evaluation index for each monitoring point at each time point involves:

[0025] Obtain the maximum value of the rate of pressure rise for each monitoring point;

[0026] The pressure rise rates at each time point and the time point corresponding to the previous maximum pressure rise rate are sorted by time, and the slope of the fitted line of the sorted result is used as the decreasing evaluation index.

[0027] The specific formula for obtaining the target injection rate at each pressure control moment for each monitoring point during the medium-term period is as follows:

[0028]

[0029] In the formula, This represents the target injection velocity at monitoring point a at time t; This indicates the minimum value within the preset injection speed control range; This indicates the preset initial injection speed; max() represents the maximum value function.

[0030] Secondly, the application of any of the methods described above in oil recovery is also provided.

[0031] This application has at least the following beneficial effects:

[0032] This application primarily employs different injection control strategies based on the varying dominant factors at different PV stages. In the early PV stage, injection pressure is the main control parameter. The priority of adjustment is determined according to its influence on the injection process. By controlling the injection pressure in the early PV stage and prioritizing adjustments based on its impact, reservoir pressure and fluid distribution can be better managed, thereby improving injection efficiency and recovery rate, reducing costs and risks, and ensuring the controllability and optimization of the injection process. In the mid-PV stage, the injection rate is adjusted in stages, considering the strength of emulsification and reservoir absorption capacity. The injection rate ratio is dynamically adjusted based on real-time monitoring data. The strength of emulsification directly affects the interaction between the injected fluid and the reservoir. By dynamically adjusting the injection rate based on emulsification intensity, the emulsification process can be more precisely controlled, ensuring thorough mixing of the injected fluid with the crude oil in the reservoir and improving oil displacement. Appropriate injection rates can enhance emulsification and increase recovery rate. Through differentiated injection schemes, targeted adjustments to emulsification intensity are implemented in different permeable layers to optimize the injection process, thereby improving oil recovery rate. Attached Figure Description

[0033] Figure 1 A flowchart illustrating the steps of an oil recovery enhancement method based on ternary composite flooding emulsification provided in one embodiment of this application;

[0034] Figure 2 This is a flowchart illustrating the acquisition of the target injection rate at each pressure control moment at each monitoring point during the intermediate period, as provided in one embodiment of this application. Detailed Implementation

[0035] In the description of the embodiments in this application, the words "exemplary," "or," and "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "exemplary," "or," and "for example" is intended to present the relevant concepts in a specific manner.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0037] It should also be noted that the terms "first" and "second" in this application and its accompanying drawings are used to distinguish similar objects, rather than to describe a specific order or sequence. The methods disclosed in the embodiments of this application or the methods shown in the flowcharts include one or more steps for implementing the method. Without departing from the scope of protection of this application, the execution order of multiple steps can be interchanged, and some steps can also be deleted.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0039] The following, in conjunction with the accompanying drawings, provides a detailed explanation of the oil recovery enhancement method based on ternary composite emulsification and its specific application scheme provided in this application.

[0040] Please see Figure 1 It illustrates a flowchart of the steps of an embodiment of the present application for a method to enhance oil recovery based on ternary composite flooding emulsification, the method including the following steps:

[0041] Step 1: By analyzing the effects of the relative molecular weight of the polymer, alkali concentration, and type of surfactant on emulsification, the optimal ratio of ternary composite flooding under each type of reservoir condition is determined.

[0042] In the development zone, reservoirs with different physical properties and crude oil properties are selected to determine the optimal ratio of ternary composite flooding, which is used for early preparation in the subsequent injection stage.

[0043] For any type of reservoir, several sets of proportioning parameters for ternary composite flooding are selected through emulsification experiments. These proportioning parameters include different relative molecular weights of the polymers, for example... , , , , , , Different types of surfactants, such as anionic surfactants like HABS, SDS, and ORS-41, nonionic surfactants like OP-4 and OP-7, and amphoteric surfactants; different alkali concentrations, such as 0.1%wt, 0.3%wt, 0.5%wt, 0.8%wt, etc.

[0044] Emulsification experiments were conducted under different control groups, such as simulated formation water with different salinities and simulated oil with different viscosities. By analyzing the effects of the relative molecular weight of the polymer, alkali concentration, and type of surfactant on emulsification, different ratios of ternary composite flooding were screened, and the ternary composite flooding ratio with the best emulsification effect was selected. Among them, the emulsification experiment of the ternary composite system is a commonly used technique in the field of reservoir recovery, and the specific process will not be described in detail.

[0045] After obtaining the optimal ratio of ternary composite flooding for different reservoirs in each study area, a lookup table is established between the study area and ternary composite flooding with different ratios, which can be used as a reference for injection volume in the subsequent injection stage.

[0046] It should be noted that during the injection process, for any given ratio, the three solutions are mixed in a predetermined order. The mixing order is generally to add the alkali solution first, then the surfactant, and finally the polymer solution, in order to avoid excessive local concentrations that could cause phase separation or degradation.

[0047] Step 2: Set up monitoring points. In the early injection void volume stage, analyze the injection pressure change characteristics of each monitoring point at each time during each injection process of the ternary composite drive to obtain the anomaly probability. Take the absolute value of the difference between the injection pressure at each monitoring point at each time and the preset pressure as the injection pressure deviation, divide it by the preset pressure to obtain the deviation ratio. Assign weights to the anomaly probability and deviation ratio at each monitoring point at each time, and sum them by weight to obtain the necessity evaluation parameters for each monitoring point at each time. Based on the necessity evaluation parameters, determine the injection pressure control time and the priority of the early injection pressure control object.

[0048] For each development zone, a multi-stage injection strategy is used for injection. During the injection process, a monitoring system is used to monitor and record key parameters such as injection pressure, injection rate, and chemical concentration. Based on the recorded data, the injection process is dynamically adjusted, which can ensure the accuracy of configuration and the stability of injection, and also build a mechanism model to determine the optimal emulsification zone, thereby improving the recovery rate while reducing costs.

[0049] In this application, high-precision flow sensors are used to monitor the flow rates of the alkali, surfactant, and polymer solutions in real time. A control algorithm is employed to precisely adjust the flow control valves of each solution according to a preset ratio (obtained using the lookup table in step one), achieving high-precision real-time dispensing of the ternary composite system. This enhances chemical dispersion and prevents excessively high local concentrations. Online quality monitoring instruments, such as near-infrared spectrometers, are installed on the dispensing pipeline to detect the composition and concentration of the ternary composite system in real time. The detection data is fed back to the control system. When a deviation between the actual composition and the set value is detected, the control system automatically adjusts the flow control valves to ensure that the dispensed ternary composite system always meets the requirements.

[0050] In this application, ternary composite drive is injected using a multi-segment plug method, wherein the multi-segment plug includes a front polymer segment plug, a ternary main segment plug, a ternary secondary segment plug, and a rear polymer protection segment plug; and the injection is performed according to the production and injection criteria.

[0051] First, the monitoring points in this application are located from the wellhead to the production section. In this application, the number of monitoring points can be set by the implementer according to the length of the core and the permeability during the core experiment. The setting standard is: the lower the permeability, the more monitoring points; the higher the permeability, the fewer monitoring points; the longer the core length, the more monitoring points; the shorter the core length, the fewer sampling points.

[0052] Preferably, in one embodiment of this application, a core length of 6m and an average permeability of 479mD are selected. Seven sampling points are set at distances of 50cm, 150cm, 250cm, 350cm, 450cm, 550cm, and 600cm from the inlet, respectively. Multiple data samplings are performed at each monitoring point, with each sampling conducted at different injection void volumes (PV). The injection pressure is recorded at each monitoring point during each sampling, and the polymer concentration, surfactant concentration, alkali concentration, cation concentration, and interfacial tension of the aqueous phase are extracted from the solution sample at each monitoring point. Concentration detection can be obtained using standard methods. Taking polymer concentration as an example, the absorbance values ​​of different concentrations of the original sample are first measured using spectrophotometry, and a standard curve of spectrophotometry (absorbance value) versus HAMP concentration is plotted. The spectrophotometry value (absorbance value) of the extracted fluid (test fluid) is then measured, and the corresponding polymer concentration value is found on the HAMP concentration standard curve using this value. It should be noted that, to avoid errors from a single measurement, the average value is taken after multiple measurements in this application.

[0053] Based on the relationship curves between seven monitoring data points—recovery rate, water cut, injection pressure, and the concentrations of polymers, alkalis, surfactants, and cations in the produced solution—and PV across all sampling results, the dynamic changes of each monitoring data point and PV at different injection stages were analyzed. Furthermore, for ternary composite flooding, multiple factors interact and influence the improvement of oil recovery, including but not limited to polymer viscosity, injection void volume, residual drag coefficient, adsorption coefficient, and interfacial tension.

[0054] Specifically, taking water cut as an example, in the waterflooding stage, the water cut is low in the early stages and gradually increases after water is reached. The recovery rate rises rapidly in the early stages of waterflooding, then gradually stabilizes. In the chemical flooding stage (constant pressure injection), as the PV number increases, the water cut first decreases and then increases, while the recovery rate first increases and then gradually stabilizes. In subsequent waterflooding stages, as the PV number increases, the water cut continues to rise, and the recovery rate continues to stabilize.

[0055] On the other hand, the rate of decrease in moisture content is affected by five factors: polymer viscosity, injected void volume, residual resistance coefficient, adsorption coefficient, and interfacial tension. The timing of the minimum moisture content is mainly influenced by viscosity, injected void volume, adsorption coefficient, and interfacial tension. The timing of the moisture content recovery is mainly influenced by the size of the injected void volume and the chemical adsorption coefficient. The rate of moisture content recovery is mainly influenced by the size of the injected void volume, interfacial tension, and chemical adsorption coefficient. In other words, different factors can affect a certain property on the moisture content curve, and the degree of influence of a factor on different properties on the moisture content curve varies, as does the degree of influence on the ternary composite emulsification effect.

[0056] In the early PV stage (less than or equal to 0.3 PV), the increase in injection pressure is the dominant factor. The correlation between the pressure rise rate in the early PV stage and the polymer viscosity, residual drag coefficient, adsorption coefficient and interfacial tension is analyzed.

[0057] Specifically, for each monitoring point at each PV value, the pressure difference between the injection pressure at the next moment and the injection pressure at the previous moment is calculated, and the ratio of the pressure difference to the time interval is used as the pressure rise rate at the next moment. The polymer viscosity, surfactant concentration, alkali concentration, cation concentration, and interfacial tension of the aqueous phase are measured by sampling the solution at each monitoring point, and correlation analysis is performed on the synchronously acquired data throughout the entire online monitoring cycle. The polymer viscosity, surfactant concentration, alkali concentration, cation concentration, and interfacial tension of the aqueous phase are used as the control targets for the injection pressure in the early PV stage.

[0058] For each monitoring point, the absolute value of the difference between the injection pressure and the preset pressure at each monitoring time is taken as the injection pressure deviation. Considering the varying distances of each monitoring point from the inlet and the insufficient absorption capacity of the reservoir where the monitoring point is located, a sharp pressure rise may occur at monitoring points in reservoirs with poor absorption capacity. In this case, the injection rate needs to be gradually reduced to ensure the pressure remains within a safe range. Anomaly detection is used in real time to detect anomalies in the pressure rise rate, obtaining the anomaly probability for each pressure rise rate. In this embodiment, the dynamic anomaly detection uses the RRCF algorithm, a well-known existing technology, which will not be elaborated upon here. Based on the injection pressure deviation at each time, the necessity evaluation parameters for adjusting the injection parameters at each monitoring time are determined, with the specific formula as follows:

[0059]

[0060] In the formula, The parameter representing the necessity evaluation of monitoring point a at time t; , Both represent weighted weights, where, + Here, all values ​​are taken. This represents the deviation of the injection pressure at monitoring point a at time t; This indicates the preset injection pressure, which is 0.3 MPa in this embodiment; This represents the probability of an anomaly in the rate of pressure rise at monitoring point a at time t; This is denoted as the deviation percentage.

[0061] The degree of anomaly in injection pressure is assessed through two dimensions: the magnitude of the injection pressure and the rate of change of the injection pressure, thus obtaining necessity evaluation parameters. For each monitoring point, after acquiring the necessity evaluation parameters in real time, the stability of the necessity evaluation parameters at each moment is calculated compared to all necessity evaluation parameters at historical moments. Specifically, a prediction algorithm is used to predict the necessity evaluation parameters at each moment based on the necessity evaluation parameters at historical moments. When there is a deviation between the predicted value and the actual calculated value, i.e., the difference is not zero, that moment is designated as the moment when injection pressure adjustment is required. The order of adjustment is determined according to the correlation between each factor and the rate of pressure rise at each monitoring point in historical moments, from strong to weak. For example, the correlation between polymer viscosity and surfactant is greater than that between polymer viscosity and surfactant. When adjusting injection pressure, adjusting the polymer concentration is preferred, thus determining the priority of the injection pressure adjustment target. In this embodiment, the correlation is calculated using the Pearson correlation coefficient.

[0062] Data prediction is a well-known technology, and commonly used prediction models include LSTM model, exponential smoothing prediction EMA, ARIMA, etc. This embodiment adopts LSTM model. Implementers can choose a suitable prediction model according to the actual situation. This application does not impose any special restrictions on the prediction method.

[0063] Step 3: During the mid-term injection void volume stage, analyze the changes in water content at each monitoring point and at each control time during each injection of the ternary composite flooding process, and determine the emulsification evaluation index at each monitoring point and at each time. Compare the changes in injection pressure at each pressure control time at each monitoring point with the injection pressure at historical times, and combine the overall distribution of emulsification evaluation index to determine the adjustment coefficient and obtain the target injection rate at each pressure control time at each monitoring point during the mid-term.

[0064] In the mid-term PV (0.3-0.7PV): emulsification is the dominant process, accompanied by the injection of ternary composite flooding. The water cut decreases significantly and the recovery rate increases rapidly. The correlation between the increase in recovery rate and the interfacial tension level and the emulsification state of the produced fluid during this stage is analyzed. The injection pressure is controlled below the fracturing pressure, and the injection rate is determined according to the reservoir absorption capacity. The fracturing pressure can be determined according to the principle of production and injection matching.

[0065] In ternary composite drive With sewage , After the process, carbonate microparticles are formed and retained in the pores of the high-permeability core, thereby increasing seepage resistance and producing an additional fluid flow diversion effect. The higher the pressure values ​​at each pressure measurement point during the ternary composite flooding injection process, the greater the likelihood of emulsification or carbonate particle retention within the core pores, and the more pronounced the effect. When emulsification occurs during ternary composite flooding injection, the emulsification intensity is divided into three stages: emulsification enhancement, emulsification weakening, and emulsification disappearance. As the migration distance of the ternary composite system increases, the emulsification capacity of the system continuously weakens. Therefore, the emulsification effect varies at different monitoring points. This application considers using monitoring data from these points to quantitatively assess the strength of the emulsification effect and obtain emulsification evaluation indicators.

[0066] In one embodiment, when emulsification is enhanced, the water content of the produced fluid decreases significantly; when emulsification weakens, the water content rebounds. By comparing the magnitude of the water content decrease at different monitoring points, the strength and effective duration of the emulsification at that point can be determined. The magnitude of the decrease is defined as the ratio of the difference between the water content at the current moment and the water content at the adjacent previous moment in the water content vs. PV curve to the water content at the previous moment. Substituting this ratio into the exp() function yields the emulsification evaluation index. The larger the ratio, the more significant the decrease and the stronger the emulsification; exp() represents an exponential function with the natural constant as the base.

[0067] During ternary composite flooding injection, the injection of high-viscosity polymer solutions gradually increases the flow resistance in the near-wellbore zone, leading to a natural decrease in injection rate at the same wellhead pressure. Furthermore, the localized high-viscosity zones created by emulsification further affect the formation's fluid uptake capacity. The high-viscosity emulsion produced by emulsification alters the reservoir's adsorption capacity due to the Jamin effect, expanding the swept volume and improving oil displacement efficiency. However, it also generates significant flow resistance, making injection more difficult at the same injection pressure. In such cases, the injection rate is typically increased slightly below a preset fracture pressure threshold. When the injection pressure rises rapidly, the injection rate should be reduced to prevent subsurface fracturing. Conversely, when the rate of increase in injection pressure gradually decreases until it plateaus, it indicates that microfractures may have formed in the formation, and the injection rate should be immediately and significantly reduced.

[0068] First, based on the injection pressure at monitoring point a, the strength of the emulsification effect, and the rate of pressure rise, the injection speed is comprehensively adjusted, with time t as the control time. According to the magnitude of the injection pressure and the rate of pressure rise, the injection state is divided into three types. At time t, the injection pressure... When the injection pressure is less than the maximum value within the historical time t-1 and the pressure rise rate is... The rate of pressure rise is greater than the average rate of increase over the past t-1 time points. At time t, it is determined that the emulsification process is generating significant ternary composite flooding injection resistance, and the injection rate should be increased; when the injection pressure at time t... Less than the preset injection pressure When the pressure rise rate at time t is greater than the historical average injection pressure and the pressure rise rate at time t gradually decreases across all times between the previous maximum point (i.e., the maximum point with the smallest time interval between time t and time t in the historical t-1 time intervals), it is determined that the injection rate should be reduced to prevent subsurface rupture. The specific formula is as follows:

[0069]

[0070] In the formula, This represents the target injection velocity at monitoring point a at time t; This represents the rate of pressure increase at monitoring point a at time t; This represents the average rate of pressure rise at monitoring point a at time t-1 in history; This indicates the preset initial injection rate; it is usually no more than 0.15PV / a, and here it is taken as 0.1PV / a. This represents the maximum value of the injected pressure at monitoring point a over the historical time t-1 moments; This represents the adjustment coefficient for monitoring point a at time t; This represents the minimum value within the injection rate control range. In this embodiment, the preset injection rate control range is 0.25 mL / min to 1.2 mL / min, so the minimum value is 0.25 mL / min. Represents logical operators.

[0071] The decreasing evaluation index representing the rate of pressure rise at monitoring point a at time t is obtained in one embodiment by sorting the rate of pressure rise at all times between time t and the time corresponding to the previous maximum rate of pressure rise, and using the slope of the fitted line of the sorted result as the decreasing evaluation index. The smaller the decreasing evaluation index, the greater the possibility that the rate of pressure rise is gradually decreasing, and the injection speed should be reduced accordingly. In another embodiment, the mean of the elements in the first-order difference sequence of the sorted result is used as the decreasing evaluation index.

[0072] The adjustment coefficient is determined by the strength of the emulsification at monitoring point a at time t, which dictates the proportion of injection rate adjustment. A larger adjustment coefficient results in a higher proportion of injection rate adjustment. Under the current PV, the adjustment coefficient is obtained based on the emulsification evaluation index of monitoring point a at time t, using the following formula:

[0073]

[0074] In the formula, This represents the maximum value of the emulsification evaluation index for monitoring point a under all PV conditions. This indicates that at time t, the rate of pressure rise is greater than the initial rate of pressure rise. The duration of the rapid growth phase, This represents the rate of pressure increase at monitoring point a at the initial moment. It should be noted that the initial moment here refers to the moment when the pressure begins to rise; exp() represents an exponential function with the natural constant as the base.

[0075] Among these factors, the stronger the emulsification effect, the stronger the injection penetration of the ternary composite flooding, and the stronger the adjustment ratio of the injection rate should be to ensure that the injection rate quickly reaches the target injection rate. Layers with strong absorption capacity typically exhibit low injection pressure but high liquid absorption, and rapid pressure diffusion; that is, the pressure of strongly absorbent layers is stable or rises slowly. Therefore... The larger the value, the more likely the reservoir at monitoring point a is to be in a state of rapid pressure rise. In this case, the injection rate should be reduced to prevent subsurface rupture, and the duration of the effect should be constrained by using an exponential function decay method.

[0076] The flowchart for obtaining the target injection rate at each pressure control moment for each monitoring point in the medium term is as follows: Figure 2 As shown.

[0077] Based on the same inventive concept as the methods described above, this application provides the application of any of the methods described above in oil recovery.

[0078] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than that shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. In the descriptions corresponding to the flowcharts and block diagrams in the accompanying drawings, the operations or steps corresponding to different blocks may also occur in a different order than disclosed in the description; sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. Each block in a block diagram and / or flowchart, and combinations of blocks in a block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0079] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from its essential characteristics. Therefore, the embodiments described above should be considered exemplary and non-limiting in all respects; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions of some technical features, without causing the essence of the corresponding technical solutions to deviate from the scope of the technical solutions in the embodiments of this application, should all be included within the protection scope of this application.

Claims

1. A method for enhanced oil recovery based on emulsification of a ternary complexing agent, characterized in that, The method comprises the following steps: By analyzing the influence of the relative molecular weight of the polymer, the alkali concentration, and the type of surfactant on the emulsification, the optimal ratio of the ternary combination flooding under each type of reservoir condition is determined; A monitoring point is set, and in the early injection void volume stage, the change characteristics of the injection pressure of the ternary combination flooding at each monitoring point at each time are analyzed, an abnormal probability is obtained, the absolute value of the difference between the injection pressure at each time of each monitoring point and the preset pressure is taken as an injection pressure deviation amount, and the injection pressure deviation amount is divided by the preset pressure to obtain a deviation proportion; the abnormal probability at each time of each monitoring point and the deviation proportion are respectively weighted, a necessity evaluation parameter at each time of each monitoring point is obtained by weighted summation, and an injection pressure regulation time is determined based on the necessity evaluation parameter, and a priority of an early injection pressure regulation object is determined; In the middle injection void volume stage, the change of the water cut of the ternary combination flooding at each regulation time of each monitoring point in each injection process is analyzed, and an emulsification evaluation index at each time of each monitoring point is determined; the change characteristics of the injection pressure at each pressure regulation time of each monitoring point are compared with the injection pressure at the historical time, and the overall distribution of the emulsification evaluation index is combined to determine an adjustment coefficient, and a target injection speed at each pressure regulation time of each monitoring point in the middle stage is obtained.

2. The enhanced oil recovery method based on emulsification of ternary complex flooding according to claim 1, characterized by, The injection of the ternary combination flooding is performed in a multi-segment manner, and the multi-segment includes a front polymer segment, a ternary main segment, a ternary auxiliary segment, and a rear polymer protection segment.

3. The enhanced oil recovery method based on emulsification of ternary complex flooding according to claim 1, characterized by, The abnormal probability is obtained in the following manner: For each injection void volume, a pressure difference between the injection pressure at the next time and the injection pressure at the previous time of each monitoring point at adjacent times is calculated, and the ratio of the pressure difference to the time interval is taken as a pressure rise rate at the next time; the pressure rise rate at each time of each monitoring point is subjected to abnormal detection to obtain an abnormal probability.

4. The method for enhanced oil recovery based on emulsification of ternary complex flooding according to claim 1, characterized in that, The step of determining the injection pressure regulation time is as follows: A prediction algorithm is used to obtain a prediction evaluation parameter at each time based on the necessity evaluation parameter at the historical time of each monitoring point; When the difference between the prediction evaluation parameter at each time and the necessity evaluation parameter is not zero, the corresponding time is taken as the regulation time of the injection pressure.

5. The enhanced oil recovery method based on emulsification of ternary complex flooding according to claim 3, characterized by, The priority of the early injection pressure regulation object is determined by the correlation between the regulation object and the pressure rise rate at the historical time of each monitoring point.

6. The method for enhanced oil recovery based on emulsification of ternary complex flooding according to claim 1, characterized in that, The process of determining the emulsification evaluation index at each time of each monitoring point is as follows: For each monitoring point, the difference between the water cut at each time and the water cut at the adjacent previous time is divided by the water cut at the previous time to obtain a ratio as the emulsification evaluation index.

7. The method for enhanced oil recovery based on emulsification of ternary complex flooding according to claim 1, characterized in that, The specific acquisition method of the adjustment coefficient is as follows: For each monitoring point, the numerical distribution characteristics of the pressure rise rate at each time and the previous time are analyzed, and a decreasing evaluation index of each monitoring point at each time is determined, which is represented by a decreasing evaluation index of monitoring point a at time t. The specific formula of the adjustment coefficient is as follows: , in the formula, represents the adjustment coefficient of the monitoring point a at time t; represents the emulsification evaluation index of the monitoring point a at time t under each PV; represents the maximum value of the emulsification evaluation index of the monitoring point a under all PVs, represents the duration of the pressure rise rate greater than the initial pressure rise rate from the initial time to time t; represents the pressure rise rate of the monitoring point a at the initial time; represents the pressure rise rate of the monitoring point a at time t; exp() represents the exponential function with the natural constant as the base; represents the injection pressure of the monitoring point a at time t; represents the maximum value of the injection pressure of the monitoring point a at the historical time t-1; represents the average pressure rise rate of the monitoring point a at the historical time t-1; represents the average injection pressure of the monitoring point a at all historical times; represents the preset injection pressure; represents a logical operator.

8. The enhanced oil recovery method based on emulsification of ternary complex flooding according to claim 7, characterized by, The determination of the decreasing evaluation index at each time of each monitoring point is as follows: The maximum value point of all the pressure rise rates of each monitoring point is obtained; All the pressure rise rates at all times between each time and the time corresponding to the adjacent previous pressure rise rate maximum value point of the time are sorted according to time, and the slope of the fitting straight line of the sorting result is taken as the decreasing evaluation index.

9. The enhanced oil recovery method based on emulsification of ternary complex flooding according to claim 7, characterized by, The target injection speed at each pressure regulation time of each monitoring point in the middle stage is obtained in the following formula: , wherein, represents the target injection rate of the monitoring point a at time t; represents the minimum value in the preset injection rate control range; represents the preset initial injection rate; represents the maximum function.

10. Use of enhanced oil recovery based on emulsification of a ternary complexing agent, characterized in that, Use in oil recovery using the method as claimed in any one of claims 1-9.

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