A method for screening and evaluating active agents for oil recovery

Abstract

The application belongs to the field of oil and gas field development, and specifically discloses a method for screening and evaluating active agents for oil production. The method comprises the following steps: determining a plurality of performance evaluation indexes of the active agents for oil production based on the characteristics of an oil reservoir to be exploited; for each performance evaluation index, constructing an evaluation coefficient for characterizing the corresponding performance; based on the evaluation coefficients of the performance evaluation indexes, constructing a comprehensive evaluation index for characterizing the comprehensive performance of the active agents for oil production; and based on the comprehensive evaluation index, evaluating the comprehensive performance of a plurality of active agents for oil production to be evaluated. The scheme of the application comprehensively considers a plurality of performance evaluation indexes to evaluate the comprehensive performance of the active agents for oil production, and can simply, quickly and scientifically screen out the active agent with the best performance from a plurality of types of active agents.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development, and specifically relates to a method for screening and evaluating active agents for oil production. Background Technology

[0002] In the later stages of oil and gas field development (e.g., shale oil reservoirs), problems such as insufficient energy supply and rapid production decline arise, necessitating technological measures to enhance energy supply and stabilize oil production. Oilfields commonly address this issue by injecting gaseous or chemical media. For chemical media, surfactants, with their strong injectability and properties of permeation, displacement, improved wettability, and oil washing, hold promise. However, given the wide variety of surfactants available, the ability to quickly and scientifically select a suitable surfactant system for a specific oil and gas field (e.g., shale oil reservoir) to maximize its energy-enhancing and oil-stabilizing effects is crucial for the development of oil and gas fields (e.g., shale oil).

[0003] Overall, most existing evaluation methods for surfactants focus on evaluating individual indicators of the developed, unique system, or subjectively assess the system's merits, without comprehensively evaluating all indicators. Currently, the industry lacks a comprehensive surfactant evaluation method that integrates various indicators for a holistic assessment. Summary of the Invention

[0004] In view of this, the present invention aims to establish a screening and evaluation method for oilfield surfactants that comprehensively considers multiple indicators, so as to simply, quickly and scientifically screen out the surfactants with the best performance from a variety of surfactant types.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: According to the present invention, a method for screening and evaluating active agents for oil production is provided, comprising the following steps: Based on the characteristics of the oil reservoir to be exploited, multiple performance evaluation indicators for oil production activators were determined. For each performance evaluation index, construct evaluation coefficients to characterize the corresponding performance; Based on the evaluation coefficients of various performance evaluation indicators, a comprehensive evaluation index is constructed to characterize the overall performance of oilfield active agents. The comprehensive performance of various oilfield active agents to be evaluated is assessed based on a comprehensive evaluation index.

[0006] In one possible implementation, a comprehensive evaluation index is constructed based on the evaluation coefficients of various performance evaluation indicators to characterize the overall performance of the oilfield active agent, including: For each performance evaluation indicator, determine the corresponding weighting factor; A comprehensive evaluation index is constructed based on the evaluation coefficients of various performance evaluation indicators and the corresponding weighting factors.

[0007] In one possible implementation, for each performance evaluation metric, a corresponding weighting factor is determined, including: Determine the evaluation coefficient values ​​of various performance evaluation indicators for the multiple oilfield active agents to be evaluated; Based on the evaluation coefficient values ​​of various performance evaluation indicators of the multiple oilfield active agents to be evaluated, the weighting factor for each performance evaluation indicator is determined.

[0008] In one possible implementation, based on the evaluation coefficient values ​​of various performance evaluation indicators of the multiple oilfield active agents to be evaluated, a weighting factor for each performance evaluation indicator is determined, including: For each performance evaluation index, based on the evaluation coefficient values ​​of the corresponding performance evaluation indexes of various oil production activators, the normalized value of the corresponding performance evaluation index of each oil production activator is calculated. Based on the normalized values ​​of the corresponding performance evaluation indicators of various oilfield active agents, the average normalized values ​​of the corresponding performance evaluation indicators of various oilfield active agents are calculated. Based on the normalized values ​​of the corresponding performance evaluation indicators of each oil production active agent and the average normalized values ​​of the corresponding performance evaluation indicators of multiple oil production active agents, the standard deviation of the normalized values ​​of the corresponding performance evaluation indicators of multiple oil production active agents is calculated. Based on the mean normalized value and the standard deviation of the normalized value, the coefficient of variation of the normalized value of the corresponding performance evaluation index is calculated. The weighting factor for each performance evaluation indicator is determined based on the coefficient of variation of the normalized values ​​of multiple performance evaluation indicators.

[0009] In one possible implementation, the normalized value of the corresponding performance evaluation index of each oil production activator is the ratio of the difference between the evaluation coefficient value of the corresponding performance evaluation index of the oil production activator and the minimum evaluation coefficient value of the corresponding performance evaluation index among multiple oil production activators to the difference between the maximum evaluation coefficient value and the minimum evaluation coefficient value of the corresponding performance evaluation index among multiple oil production activators.

[0010] In one possible implementation, the coefficient of variation of the normalized value of the corresponding performance evaluation index is the ratio of the standard deviation of the normalized value of the corresponding performance evaluation index to the mean normalized value of the corresponding performance evaluation index.

[0011] In one possible implementation, the weighting factor for each performance evaluation metric is the ratio of the coefficient of variation of the normalized value of that performance evaluation metric to the sum of the coefficients of variation of the normalized values ​​of all performance evaluation metrics.

[0012] In one possible implementation, the screening and evaluation method for oilfield active agents is applicable to the screening and evaluation of various active agents for shale oil.

[0013] In one possible implementation, based on the characteristics of the reservoir to be exploited, multiple performance evaluation indicators for the oil production activator are determined, including: Based on the characteristics of shale oil, several performance evaluation indicators for surfactants used in shale oil were determined. These indicators include performance evaluation indicators for reducing interfacial tension, thermal stability, improving wetting performance, and oil washing performance.

[0014] In one possible implementation, for each performance evaluation metric, evaluation coefficients are constructed to characterize the corresponding performance, including: Based on the interfacial tension of water / oil and the interfacial tension of surfactant / oil, an interfacial tension reduction coefficient is constructed to evaluate the performance of reducing interfacial tension. A thermal stability coefficient for evaluating thermal stability performance is constructed based on the initial surfactant / oil interfacial tension and the surfactant / oil interfacial tension after aging. Based on the capillary self-absorption height of water and the capillary self-absorption height of surfactant, a wettability improvement coefficient is constructed to evaluate the improvement of wettability. Based on the oil washing efficiency of water and the oil washing efficiency of surfactants, an oil washing performance improvement coefficient is constructed to evaluate the oil washing performance.

[0015] In one possible implementation, the interface tension reduction factor is constructed as follows: , in: —Interfacial tension reduction coefficient, dimensionless; —Interfacial tension between water and oil, mN / m; —Active agent / oil interfacial tension value, mN / m.

[0016] In one possible implementation, the thermal stability coefficient is constructed as follows: , in: —Thermal stability coefficient, dimensionless; —Active agent / oil interfacial tension value after aging, mN / m; —Initial surfactant / oil interfacial tension value, mN / m.

[0017] In one possible implementation, the wettability improvement coefficient is constructed as follows: , in: — Coefficient of improvement in wettability, dimensionless; —Active agent capillary self-absorption height, mm; —Water capillary self-priming height, mm.

[0018] In one possible implementation, the oil-washing performance improvement factor is constructed in the following way: , in: —Effect coefficient for improving oil washing performance, dimensionless; —Active oil-washing efficiency, % —Water washing efficiency,%.

[0019] In one possible implementation, based on the evaluation coefficients of various performance evaluation indicators, a comprehensive evaluation index for characterizing the overall performance of oilfield active agents is constructed in the following way: , in: C EI This is a comprehensive evaluation index, dimensionless. , , , These are the maximum interfacial tension reduction coefficient, maximum thermal stability coefficient, maximum wettability improvement coefficient, and maximum oil washing performance improvement coefficient among various shale oil surfactants. oh J , oh L , oh H , oh X , are the weighting factors for the performance evaluation indices of reducing interfacial tension, thermal stability, improving wetting performance, and washing performance, respectively, and are dimensionless.

[0020] In one possible implementation, the interfacial tension between water and oil and the interfacial tension between surfactant and oil are measured using a spin-drop interfacial tension meter.

[0021] In one possible implementation, the initial surfactant / oil interfacial tension and the aged surfactant / oil interfacial tension are respectively the surfactant / oil interfacial tensions measured by a spin drop interfacial tension meter before and after surfactant aging, wherein the aging temperature is determined based on the target reservoir temperature and the aging time is determined based on the well shut-in time during on-site construction.

[0022] In one possible implementation, the capillary self-absorption height for water and the capillary self-absorption height for surfactant are obtained by conducting capillary self-absorption height tests under water and surfactant conditions using oleophilic standard capillary tubes with pore throat dimensions similar to those of the target reservoir.

[0023] In one possible implementation, the oil washing efficiency of water and the oil washing efficiency of surfactants are obtained respectively through the following methods: Based on the oil saturation of the target reservoir, shale oil is mixed with natural core fragments to prepare a certain proportion of oil sands. After aging treatment of the oil sands, a certain amount of aged oil sands is weighed, placed in a reactor, and weighed and recorded as m1. Add water or surfactant to the reactor, place the reactor in an aging kettle, and wash the oil under pressure and at the target reservoir temperature. After washing the oil, remove the reactor, remove the crude oil floating in the sample solution after standing and the crude oil adhering to the reactor wall, and remove the upper surfactant solution. Then dry the reactor to constant weight and record it as m2. The dried sample was eluted with petroleum ether until the petroleum ether became colorless. The reactor after elution of crude oil was dried to constant weight and recorded as m3. Washing efficiency R h Calculate according to the following formula: , in: —Oil washing efficiency (%) —The mass of the reactor containing oil sands, in grams (g); —The mass of the reactor containing oily sand after washing and drying, in grams (g). —The mass of the reactor containing oily sand after drying following petroleum ether elution, expressed in grams (g).

[0024] In one possible implementation, the comprehensive performance of various oilfield active agents to be evaluated is assessed based on a comprehensive evaluation index, including: The oil production activator with the highest comprehensive evaluation index among the various oil production activators to be evaluated was determined to be the best activator for implementing huff and puff in the oil reservoir to be developed.

[0025] By adopting the above technical solution, the present invention has at least the following beneficial technical effects: The method for screening and evaluating oil production surfactants provided by this invention determines multiple performance evaluation indicators of oil production surfactants based on the characteristics of the oil reservoir to be exploited, and constructs a comprehensive evaluation index based on the evaluation coefficients of each performance evaluation indicator to evaluate the comprehensive performance of oil production surfactants. This method is more objective and scientific, ensuring more accurate screening of surfactants for huff and puff in the oil reservoir to be exploited and better application results. Attached Figure Description

[0026] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart of the method for screening and evaluating oilfield active agents provided by the present invention; Figure 2 This is a block diagram of an embodiment of the oilfield active agent screening and evaluation method provided by the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. These embodiments are provided in this disclosure to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art.

[0029] It should be noted that, in the description of this disclosure, unless otherwise stated, the expressions "multiple," "multiple items," "various types," etc., mean more than or equal to two, two items, or two kinds. In the description of this disclosure, words such as "including" or "containing" mean that the element preceding the word covers the element listed after the word, and do not exclude the possibility of covering other elements as well.

[0030] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0031] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0032] According to the present invention, a method for screening and evaluating active agents for oil production is provided, such as... Figure 1 As shown, the method includes the following steps: S1: Based on the characteristics of the oil reservoir to be exploited, determine multiple performance evaluation indicators for oil production activators; S2: For each performance evaluation indicator, construct an evaluation coefficient to characterize the corresponding performance; S3: Based on the evaluation coefficients of each performance evaluation indicator, construct a comprehensive evaluation index to characterize the comprehensive performance of the oil production activator; S4: Based on the comprehensive evaluation index, evaluate the comprehensive performance of the multiple oil production activators to be evaluated.

[0033] The method for screening and evaluating oil production surfactants provided by this invention determines multiple performance evaluation indicators of oil production surfactants based on the characteristics of the oil reservoir to be exploited, and constructs a comprehensive evaluation index based on the evaluation coefficients of each performance evaluation indicator to evaluate the comprehensive performance of oil production surfactants. This method is more objective and scientific, ensuring more accurate screening of surfactants for huff and puff in the oil reservoir to be exploited and better application results.

[0034] In one possible implementation, step S3 involves constructing a comprehensive evaluation index to characterize the overall performance of the oilfield active agent based on the evaluation coefficients of each performance evaluation index. This includes: determining the corresponding weighting factor for each performance evaluation index; and constructing the comprehensive evaluation index based on the evaluation coefficients of each performance evaluation index and the corresponding weighting factors. By determining the weighting factors of each performance evaluation index and constructing the comprehensive evaluation index based on these weighting factors, the weights of each performance evaluation index are balanced, thereby making the comprehensive performance evaluation of the oilfield active agent more systematic.

[0035] In one possible implementation, for each performance evaluation index, a corresponding weighting factor is determined, including: determining the evaluation coefficient values ​​of each performance evaluation index of the various oilfield active agents to be evaluated; and determining the weighting factor for each performance evaluation index based on the evaluation coefficient values ​​of the various performance evaluation indexes of the various oilfield active agents to be evaluated. By determining the weighting factor based on the evaluation coefficient values ​​of each performance evaluation index of the various oilfield active agents to be evaluated, the mathematical and statistical characteristics of each performance evaluation index in these oilfield active agents are utilized, thereby making the comprehensive performance evaluation of oilfield active agents more systematic, objective, and scientific, and avoiding the influence of human subjectivity.

[0036] In one possible implementation, based on the evaluation coefficient values ​​of various performance evaluation indicators of multiple oilfield active agents to be evaluated, the weighting factor for each performance evaluation indicator is determined, including: for each performance evaluation indicator, based on the evaluation coefficient values ​​of the corresponding performance evaluation indicators of multiple oilfield active agents, calculating the normalized value of the corresponding performance evaluation indicator for each oilfield active agent; based on the normalized values ​​of the corresponding performance evaluation indicators of multiple oilfield active agents, calculating the average normalized value of the corresponding performance evaluation indicators of multiple oilfield active agents; based on the normalized values ​​of the corresponding performance evaluation indicators of each oilfield active agent and the average normalized value of the corresponding performance evaluation indicators of multiple oilfield active agents, calculating the standard deviation of the normalized values ​​of the corresponding performance evaluation indicators of multiple oilfield active agents; based on the average normalized value and the standard deviation of the normalized values, calculating the coefficient of variation of the normalized values ​​of the corresponding performance evaluation indicators; and based on the coefficient of variation of the normalized values ​​of multiple performance evaluation indicators, determining the weighting factor for each performance evaluation indicator.

[0037] In one possible implementation, the normalized value of the corresponding performance evaluation index of each oil production activator is the ratio of the difference between the evaluation coefficient value of the corresponding performance evaluation index of the oil production activator and the minimum evaluation coefficient value of the corresponding performance evaluation index among multiple oil production activators to the difference between the maximum evaluation coefficient value and the minimum evaluation coefficient value of the corresponding performance evaluation index among multiple oil production activators.

[0038] In one possible implementation, the coefficient of variation of the normalized value of the corresponding performance evaluation index is the ratio of the standard deviation of the normalized value of the corresponding performance evaluation index to the mean normalized value of the corresponding performance evaluation index.

[0039] In one possible implementation, the weighting factor for each performance evaluation metric is the ratio of the coefficient of variation of the normalized value of that performance evaluation metric to the sum of the coefficients of variation of the normalized values ​​of all performance evaluation metrics.

[0040] The method for screening and evaluating active agents for oil production provided by this invention is applicable to the screening and evaluation of active agents for shale oil. The following uses the screening and evaluation of active agents for shale oil as an example, with reference to... Figure 2 The present invention will be further described below. However, it should be understood that the concept of the present invention is not limited thereto, and the method for screening and evaluating active agents for oil production provided by the present invention is also applicable to screening and evaluating active agents for other types of oil reservoirs.

[0041] Shale oil reservoirs are characterized by tight reservoirs and poor connectivity, leading to insufficient energy supply and rapid production decline in the later stages of development. Therefore, there is an urgent need for energy-enhancing and oil-stabilizing technologies. In oilfields, this problem is commonly addressed by injecting gaseous or chemical media. For chemical media, surfactants, with their strong injectability and the ability to permeate, replace, improve wettability, and wash away oil, show promising application prospects. However, with a wide variety of surfactants available, the rapid and scientific selection of a suitable surfactant system for shale oil reservoirs to maximize its energy-enhancing and oil-stabilizing effects is of great significance for shale oil development.

[0042] In one possible implementation, based on the characteristics of shale oil, multiple performance evaluation indicators for surfactants used in shale oil are determined. These indicators include performance evaluation indicators for reducing interfacial tension, thermal stability, improving wetting performance, and oil-washing performance. This establishes a comprehensive screening and evaluation method for surfactants used in shale oil, considering static interfacial tension, thermal stability, improved wetting performance, and dynamic oil-washing performance.

[0043] In shale oil huff and puff processes using surfactants or "surfactant + X" methods, percolation and displacement, improved wettability, and oil-washing effects are crucial mechanisms for enhancing development efficiency. However, existing surfactant screening and evaluation processes often rely on only one or a few key indicators as evaluation criteria because it's impossible to ensure all indicators meet the standards. This leads to a degree of subjectivity in surfactant selection. This invention, based on mathematical statistics, establishes a comprehensive screening and evaluation method that considers static interfacial tension, thermal stability, improved wettability, and dynamic oil-washing performance. A comprehensive evaluation index is used to determine the overall performance of the system, making the method more objective and scientific, ensuring more accurate surfactant selection and better application results for shale oil huff and puff.

[0044] In one possible implementation, an interfacial tension reduction coefficient is constructed based on the interfacial tension between water and oil and the interfacial tension between the surfactant and oil to evaluate the performance of reducing interfacial tension. Here and below, "oil" refers to the target crude oil, i.e., the oil available at the reservoir to be exploited.

[0045] In one possible implementation, the interface tension reduction coefficient is constructed using the following formula (1): (1) in: —Interfacial tension reduction coefficient, dimensionless; —Interfacial tension between water and oil, mN / m; —Active agent / oil interfacial tension value, mN / m.

[0046] In one possible implementation, the interfacial tension between water and oil and the interfacial tension between surfactant and oil are measured using a spin-drop interfacial tension meter.

[0047] In one possible implementation, a thermal stability coefficient is constructed to evaluate thermal stability performance based on the initial surfactant / oil interfacial tension and the surfactant / oil interfacial tension after aging.

[0048] In one possible implementation, the thermal stability coefficient is constructed using the following formula (2): (2) in: —Thermal stability coefficient, dimensionless; —Active agent / oil interfacial tension value after aging, mN / m; —Initial surfactant / oil interfacial tension value, mN / m.

[0049] In one possible implementation, the initial surfactant / oil interfacial tension and the aged surfactant / oil interfacial tension are respectively the surfactant / oil interfacial tensions measured by a spin drop interfacial tension meter before and after surfactant aging, wherein the aging temperature is determined based on the target reservoir temperature and the aging time is determined based on the well shut-in time during on-site construction.

[0050] Specifically, in one example, a prepared surfactant solution of a certain mass concentration is placed in a high-temperature reactor, which is then placed in an oven (or heated in a constant-temperature water bath) at the target reservoir temperature. After aging for a certain period, the solution is removed and the interfacial tension is retested. The specific aging time is determined according to the well shut-in time during shale oil huff and puff operations. By comparing the interfacial tension values ​​between the surfactant and the target crude oil before and after aging, the temperature resistance of the system can be evaluated.

[0051] In one possible implementation, a wettability improvement coefficient is constructed based on the capillary self-absorption height of water and the capillary self-absorption height of surfactant to evaluate the improvement of wettability.

[0052] In one possible implementation, the wettability improvement coefficient is constructed using the following formula (3): (3) in: — Coefficient of improvement in wettability, dimensionless; —Active agent capillary self-absorption height, mm; —Water capillary self-priming height, mm.

[0053] In one possible implementation, the capillary self-absorption height for water and the capillary self-absorption height for surfactant are obtained by conducting capillary self-absorption height tests under water and surfactant conditions using oleophilic standard capillary tubes with pore throat dimensions similar to those of the target reservoir.

[0054] Specifically, in one example, an oleophilic standard capillary with a pore throat size similar to that of the target reservoir was used to conduct a capillary self-absorption height test. By comparing the heights, the improvement in wetting performance of the system was evaluated. The specific experimental steps included: ① Preparing the standard capillary into an oil-wetted capillary and storing it for later use; ② Taking a prepared surfactant solution of a certain mass concentration, adding a small amount of dyeing ink, and pouring the solution to be tested into a cuvette up to the top boundary, with the scale placed firmly against the back wall; ③ Placing the three prepared capillary tubes vertically in the cuvette, ensuring that all test capillary tubes had the same tilt angle, reading the height difference between the liquid level in the tube and the top boundary of the cuvette, and recording the highest liquid level height of the capillary tube submerged in the liquid surface, which is the measurement result. By comparing the capillary self-absorption height values ​​of water / surfactant solutions, the improvement in wetting performance of the surfactant solution can be evaluated.

[0055] In one possible implementation, a washing performance improvement coefficient is constructed to evaluate the washing performance based on the washing efficiency of water and the washing efficiency of surfactants.

[0056] In one possible implementation, the oil washing performance improvement coefficient is constructed by the following formula (4): (4) in: —Effect coefficient for improving oil washing performance, dimensionless; —Active oil-washing efficiency, % —Water washing efficiency,%.

[0057] In one possible implementation, the water washing efficiency and the surfactant washing efficiency are obtained as follows: Based on the oil saturation of the target reservoir, shale oil is mixed with natural core fragments to prepare a certain proportion of oil sands. After aging the oil sands, a certain amount of aged oil sands is weighed and placed in a reactor, recorded as m1. Water or surfactant is added to the reactor, which is then placed in an aging vessel. Under pressure and at the target reservoir temperature, the oil is washed. After washing, the reactor is removed, and the crude oil floating in the sample solution and adhering to the reactor wall is removed. The surfactant solution is also removed, and the reactor is dried to constant weight, recorded as m2. Petroleum ether is used to elute the dried sample until the ether is colorless. The reactor, after all crude oil has been washed away, is dried to constant weight, recorded as m3. The washing efficiency R... h Calculate according to the following formula (5): (5) in: —Oil washing efficiency (%) —The mass of the reactor containing oil sands, in grams (g); —The mass of the reactor containing oily sand after washing and drying, in grams (g). —The mass of the reactor containing oily sand after drying following petroleum ether elution, expressed in grams (g).

[0058] Specifically, in one example, a high-temperature steel aging reactor and a stoppered ground-glass conical flask were used to evaluate the oil washing efficiency. The specific operating steps were as follows: ① According to the oil saturation of the reservoir, shale oil was mixed with natural core fragments to prepare a certain proportion of oil sands. The oil sands were then placed in the aging reactor and aged at the target block temperature for later use; ② A certain mass of aged oil sands was weighed using a balance and added to a stoppered ground-glass conical flask, and the weight was recorded as m1; ③ An active agent system of a certain mass concentration was added to the conical flask to completely submerge the oil sands, and the conical flask was placed... In the aging kettle, pressurize with air or inert gas (pressure is used to prevent the surfactant from boiling at high temperatures) and let it stand for washing at the target block temperature; ④ Remove the conical flask, use clean cotton gauze to remove the crude oil floating in the sample solution and the crude oil adhering to the flask wall after standing, remove the upper clean surfactant solution, and place the conical flask in a high-temperature oven to dry to constant weight, recorded as m2; ⑤ Use petroleum ether to elute the crude oil from the dried sample until the petroleum ether is colorless; ⑥ Place the conical flask with all crude oil eluted in a high-temperature oven to dry to constant weight, recorded as m3; ⑦ Washing efficiency R h Calculate according to the above formula (5).

[0059] In one possible implementation, a comprehensive evaluation index for characterizing the overall performance of the oilfield active agent is constructed based on the evaluation coefficients of various performance evaluation indicators using the following formula (6): (6) in: C EI This is a comprehensive evaluation index, dimensionless. , , , These are the maximum interfacial tension reduction coefficient, maximum thermal stability coefficient, maximum wettability improvement coefficient, and maximum oil washing performance improvement coefficient among various shale oil surfactants. oh J , oh L , oh H , oh X , are the weighting factors for the performance evaluation indices of reducing interfacial tension, thermal stability, improving wetting performance, and washing performance, respectively, and are dimensionless.

[0060] The calculation methods for each weighting factor in formula (6) are as follows: (a) Calculate the normalized value using the formula shown in equation (7): (7) in: y The interfacial tension reduction coefficient ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or the coefficient of performance improvement in washing oil ( The normalized value of ), dimensionless; x The interfacial tension reduction coefficient ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or the coefficient of performance improvement in washing oil ( ); x max The interfacial tension reduction coefficient ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or the coefficient of performance improvement in washing oil ( The maximum value of ). x min The interfacial tension reduction coefficient ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or improve the washing performance coefficient ( The minimum value of ).

[0061] (b) Calculate the average normalized value using the following formula (8): (8) in: The interfacial tension reduction coefficient ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or the coefficient of performance improvement in washing oil ( The average normalized value of (), dimensionless; n The quantity of the oilfield active agent to be evaluated is dimensionless. y i The interfacial tension reduction coefficient of the i-th oilfield surfactant to be evaluated ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or the coefficient of performance improvement in washing oil ( The normalized value of ).

[0062] (c) Calculate the standard deviation of the normalized value using the following formula (9): (9) in: s The interfacial tension reduction coefficient ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or the coefficient of performance improvement in washing oil ( The standard deviation of the normalized value is dimensionless.

[0063] (d) Calculate the coefficient of variation of the normalized value, using the formula (10) below: (10) in: C V The interfacial tension reduction coefficient ( ) or thermal stability coefficient ( ) or wettability improvement coefficient ( ) or the coefficient of performance improvement in washing oil ( The coefficient of variation of the normalized value, dimensionless.

[0064] (e) Calculate the weighting factor oh ,in: (11) in: This is a weighting factor for the interfacial tension reduction coefficient. , , , These are the coefficients of variation of the normalized values ​​of the interfacial tension reduction coefficient, thermal stability coefficient, wettability improvement coefficient, and oil washing performance improvement coefficient, respectively, and are dimensionless.

[0065] The weighting factors for the thermal stability coefficient, wettability improvement coefficient, and oil washing performance improvement coefficient are determined in a manner similar to the above formula (11).

[0066] In one possible implementation, the comprehensive performance of various oil production activators to be evaluated is assessed based on a comprehensive evaluation index, including: determining the oil production activator with the highest comprehensive evaluation index among the various oil production activators to be evaluated as the best activator for implementing huff and puff in the oil reservoir to be developed.

[0067] To more clearly illustrate the shale oil surfactant screening and evaluation method provided by this invention, specific implementation steps of this invention are illustrated with examples.

[0068] (1) Results of basic performance tests of surfactants This example uses shale oil crude oil A as the experimental subject and evaluates four surfactants (mass concentration 0.2%). The experimental results are shown in Table 1 below: Table 1. Results of Basic Performance Tests for Surfactants

[0069] (2) Comprehensive performance evaluation of surfactants for shale oil According to formulas (1) to (11), the evaluation coefficients, weighting factors and comprehensive evaluation indices of the four active agents are calculated respectively. The calculation results are shown in Tables 2, 3 and 4.

[0070] Table 2 Evaluation coefficient values ​​of different properties of surfactants

[0071] Table 3 Weighting factor values ​​for various properties of surfactants

[0072] Table 4 Comprehensive Evaluation Index of Surfactants

[0073] As can be seen from the table, surfactant #1 has the highest comprehensive evaluation index. Therefore, surfactant #1 is determined to be the best surfactant for implementing shale oil huff and puff.

[0074] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. The sequence numbers of the disclosed embodiments of this invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0075] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0076] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for screening and evaluating active agents for oil recovery, characterized in that, Includes the following steps: Based on the characteristics of the oil reservoir to be exploited, multiple performance evaluation indicators for oil production activators were determined. For each performance evaluation index, construct evaluation coefficients to characterize the corresponding performance; Based on the evaluation coefficients of various performance evaluation indicators, a comprehensive evaluation index is constructed to characterize the overall performance of oilfield active agents. The comprehensive performance of various oilfield active agents to be evaluated is assessed based on a comprehensive evaluation index.

2. The method for screening and evaluating oilfield active agents according to claim 1, characterized in that, Based on the evaluation coefficients of various performance evaluation indicators, a comprehensive evaluation index is constructed to characterize the overall performance of oilfield active agents, including: For each performance evaluation indicator, determine the corresponding weighting factor; A comprehensive evaluation index is constructed based on the evaluation coefficients of various performance evaluation indicators and the corresponding weighting factors.

3. The method for screening and evaluating oilfield active agents according to claim 2, characterized in that, For each performance evaluation metric, determine the corresponding weighting factors, including: Determine the evaluation coefficient values ​​of various performance evaluation indicators for the multiple oilfield active agents to be evaluated; Based on the evaluation coefficient values ​​of various performance evaluation indicators of the multiple oilfield active agents to be evaluated, the weighting factor for each performance evaluation indicator is determined.

4. The method for screening and evaluating oilfield active agents according to claim 3, characterized in that, Based on the evaluation coefficient values ​​of various performance evaluation indicators of the multiple oilfield active agents to be evaluated, the weighting factor for each performance evaluation indicator is determined, including: For each performance evaluation index, based on the evaluation coefficient values ​​of the corresponding performance evaluation indexes of various oil production activators, the normalized value of the corresponding performance evaluation index of each oil production activator is calculated. Based on the normalized values ​​of the corresponding performance evaluation indicators of various oilfield active agents, the average normalized values ​​of the corresponding performance evaluation indicators of various oilfield active agents are calculated. Based on the normalized values ​​of the corresponding performance evaluation indicators of each oil production active agent and the average normalized values ​​of the corresponding performance evaluation indicators of multiple oil production active agents, the standard deviation of the normalized values ​​of the corresponding performance evaluation indicators of multiple oil production active agents is calculated. Based on the mean normalized value and the standard deviation of the normalized value, the coefficient of variation of the normalized value of the corresponding performance evaluation index is calculated. The weighting factor for each performance evaluation indicator is determined based on the coefficient of variation of the normalized values ​​of multiple performance evaluation indicators.

5. The method for screening and evaluating oilfield active agents according to claim 4, characterized in that, The normalized value of the corresponding performance evaluation index for each oil production activator is the ratio of the difference between the evaluation coefficient value of the corresponding performance evaluation index for that oil production activator and the minimum evaluation coefficient value of the corresponding performance evaluation index among multiple oil production activators to the difference between the maximum evaluation coefficient value and the minimum evaluation coefficient value of the corresponding performance evaluation index among multiple oil production activators. The coefficient of variation of the normalized value of the corresponding performance evaluation index is the ratio of the standard deviation of the normalized value of the corresponding performance evaluation index to the mean normalized value of the corresponding performance evaluation index. The weighting factor for each performance evaluation indicator is the ratio of the coefficient of variation of the normalized value of that performance evaluation indicator to the sum of the coefficients of variation of the normalized values ​​of all performance evaluation indicators.

6. The method for screening and evaluating oilfield active agents according to claim 1, characterized in that, The screening and evaluation method for active agents used in oil production is applicable to the screening and evaluation of various active agents for shale oil.

7. The method for screening and evaluating oilfield active agents according to claim 6, characterized in that, Based on the characteristics of the oil reservoir to be exploited, several performance evaluation indicators for oil production activators were determined, including: Based on the characteristics of shale oil, several performance evaluation indicators for surfactants used in shale oil were determined. These indicators include performance evaluation indicators for reducing interfacial tension, thermal stability, improving wetting performance, and oil washing performance.

8. The method for screening and evaluating oilfield active agents according to claim 7, characterized in that, For each performance evaluation metric, evaluation coefficients are constructed to characterize the corresponding performance, including: Based on the interfacial tension of water / oil and surfactant / oil, an interfacial tension reduction coefficient is constructed to evaluate the performance of reducing interfacial tension; and / or A thermal stability coefficient is constructed based on the initial surfactant / oil interfacial tension and the surfactant / oil interfacial tension after aging to evaluate thermal stability performance; and / or Based on the capillary self-absorption height of water and the capillary self-absorption height of surfactant, a wettability improvement coefficient is constructed to evaluate the improvement of wetting performance; and / or Based on the oil washing efficiency of water and the oil washing efficiency of surfactants, an oil washing performance improvement coefficient is constructed to evaluate the oil washing performance.

9. The method for screening and evaluating oilfield active agents according to claim 8, characterized in that, The interfacial tension reduction coefficient is constructed in the following way: in: —Interfacial tension reduction coefficient, dimensionless; —Interfacial tension between water and oil, mN / m; —Active agent / oil interfacial tension value, mN / m; and / or The thermal stability coefficient is constructed in the following way: in: —Thermal stability coefficient, dimensionless; —Active agent / oil interfacial tension value after aging, mN / m; —Initial surfactant / oil interfacial tension, mN / m; and / or The wettability improvement coefficient is constructed in the following way: in: — Coefficient of improvement in wettability, dimensionless; —Active agent capillary self-absorption height, mm; —Water capillary self-priming height, mm; and / or The oil-washing performance improvement coefficient is constructed in the following way: in: —Effect coefficient for improving oil washing performance, dimensionless; —Active agent degreasing efficiency, % —Water washing efficiency,%.

10. The method for screening and evaluating oilfield active agents according to claim 9, characterized in that, Based on the evaluation coefficients of various performance evaluation indicators, a comprehensive evaluation index for characterizing the overall performance of oilfield active agents is constructed using the following method: in: C EI This is a comprehensive evaluation index, dimensionless. , , , These are the maximum interfacial tension reduction coefficient, maximum thermal stability coefficient, maximum wettability improvement coefficient, and maximum oil washing performance improvement coefficient among various shale oil surfactants. ω J , ω L , ω H , ω X , are the weighting factors for the performance evaluation indices of reducing interfacial tension, thermal stability, improving wetting performance, and washing performance, respectively, and are dimensionless.

11. The method for screening and evaluating oilfield active agents according to claim 8, characterized in that, The interfacial tensions between water and oil and between surfactant and oil were measured using a spin drop interfacial tension meter.

12. The method for screening and evaluating oilfield active agents according to claim 8, characterized in that, The initial surfactant / oil interfacial tension and the surfactant / oil interfacial tension after aging are the surfactant / oil interfacial tensions measured by a spin drop interfacial tension meter before and after surfactant aging, respectively. The aging temperature is determined based on the target reservoir temperature, and the aging time is determined based on the well shut-in time during on-site construction.

13. The method for screening and evaluating oilfield active agents according to claim 8, characterized in that, The capillary self-absorption heights for water and surfactant were obtained by conducting capillary self-absorption height tests under water and surfactant conditions using oleophilic standard capillary tubes with pore throat dimensions similar to those of the target reservoir.

14. The method for screening and evaluating oilfield active agents according to claim 8, characterized in that, The oil washing efficiency of water and the oil washing efficiency of surfactants were obtained through the following methods: Based on the oil saturation of the target reservoir, shale oil is mixed with natural core fragments to prepare a certain proportion of oil sands. After aging treatment of the oil sands, a certain amount of aged oil sands is weighed, placed in a reactor, and weighed and recorded as m1. Add water or surfactant to the reactor, place the reactor in an aging kettle, and wash the oil under pressure and at the target reservoir temperature. After washing the oil, remove the reactor, remove the crude oil floating in the sample solution after standing and the crude oil adhering to the reactor wall, and remove the upper surfactant solution. Then dry the reactor to constant weight and record it as m2. The dried sample was eluted with petroleum ether until the petroleum ether became colorless. The reactor after elution of crude oil was dried to constant weight and recorded as m3. Washing efficiency R h Calculate according to the following formula: in: —Oil washing efficiency (%) —The mass of the reactor containing oil sand, in grams (g); —The mass of the reactor containing oily sand after washing and drying, in grams (g). —The mass of the reactor containing oily sand after drying following petroleum ether elution, expressed in grams (g).

15. The method for screening and evaluating oilfield active agents according to claim 1, characterized in that, Based on the comprehensive evaluation index, the overall performance of various oilfield active agents to be evaluated is assessed, including: The oil production activator with the highest comprehensive evaluation index among the various oil production activators to be evaluated was determined to be the best activator for implementing huff and puff in the oil reservoir to be developed.

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