Method for evaluating oil displacement performance of oil displacement system

Abstract

The invention provides a method for evaluating oil displacement performance of an oil displacement system. The method comprises the following steps: determining matching parameters of the oil displacement system and oil reservoir performance; determining the weight of the matching parameter, and determining the qualified value range of the matching parameter; determining the oil displacement systems which do not accord with the qualified value range of the matching parameters as unqualified systems, and determining the oil displacement systems which accord with the qualified value range of the matching parameters as qualified systems; independently scoring the value of each matching parameter in the qualified system, performing sub-combination scoring on sub-combinations among the matching parameters, and allocating sub-combination scores to each matching parameter according to weight coefficients in the sub-combinations to obtain comprehensive scores of the matching parameters; and calculating the overall score of the qualified system according to the weight of the matching parameter and the comprehensive score, and carrying out quantitative characterization on the oil displacement system. According to the method, the single-component or multi-component oil displacement system can be evaluated, the oil displacement system with the high oil displacement rate can be screened out only through indoor tests, and the method is simple and convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of oil recovery, and in particular to a method for evaluating the oil recovery performance of an oil recovery system. Background Art

[0002] Chemical flooding is one of the leading technologies for enhancing oil recovery in continental sedimentary oil fields. The results of the second potential assessment indicate that chemical flooding (polymer flooding and chemical combination flooding) can increase recoverable reserves, with chemical combination flooding accounting for 52.3% of the potential. Currently, chemical combination flooding technology is in a critical transition period, from strong alkaline to weak alkaline and alkaline-free.

[0003] With the increasing expansion of reservoir objects and technological progress in chemical flooding, the objects of chemical combination flooding have expanded from medium- and high-permeability reservoirs (Class I) to medium- and low-permeability (Class II and Class III) reservoirs, and from large-scale integrated sandstone reservoirs to complex fault block reservoirs, conglomerate reservoirs, and fractured reservoirs. However, the harsh reservoir conditions and imperfect supporting technologies have limited the application of chemical combination flooding technology.

[0004] Oil displacement experiments have shown that combined flooding produces a continuous emulsion at the production end. Emulsified flooding systems improve oil recovery by 5-8% compared to non-emulsified systems. Field testing at the Daqing mine revealed that emulsified blocks increased oil recovery by 5-6% compared to non-emulsified blocks. Emulsification was observed in 66% of the oil wells produced during binary flooding in Xinjiang. The emulsification performance of an oil displacement system is crucial to ensuring its effectiveness. Surfactants can effectively enhance oil recovery. Previously, surfactant screening focused on their ability to reduce oil-water interfacial tension. However, research has revealed that surfactant systems with excellent interfacial properties do not necessarily improve oil displacement efficiency.

[0005] Research has found that strong emulsification systems can better improve oil recovery efficiency than weak emulsification systems. The emulsion formed during the oil recovery process plays a very important role in improving oil recovery. Especially as the development targets shift to medium-low permeability, highly heterogeneous conglomerate, high-temperature, and high-salinity reservoirs, it is difficult to achieve both polymer injectivity and increased swept volume. Therefore, the emulsification performance of the oil recovery system is crucial. Surfactants with strong emulsification ability will form emulsions with crude oil. Microscopic models have observed that emulsion droplets will cause a certain degree of clogging at the throat during the oil recovery process. Controlling the emulsification strength of the oil recovery system and matching it with the pore throat are key oil recovery mechanisms in binary flooding. It is urgent to research the emulsification control oil recovery system to significantly improve the oil recovery effect and orderly promote the field application of binary composite flooding.

[0006] The current oil displacement evaluation mainly focuses on macroscopic stability performance evaluation and static qualitative evaluation methods (emulsification phase, water separation, emulsification comprehensive index). It is unable to dynamically and systematically evaluate the emulsification performance and cannot obtain the emulsion stability mechanism at the microscopic level, conduct quantitative research on the structure-performance relationship, guide the optimization of personalized oil displacement systems, and achieve quantitative regulation of the emulsification grade of oil displacement systems.

[0007] Therefore, it is necessary to develop new evaluation methods for oil displacement systems. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for evaluating the oil recovery performance of an oil recovery system. The method combines the advantages of macro-emulsification and in-situ emulsification of porous media, optimizes key evaluation conditions to eliminate system errors, and establishes a multi-dimensional quantitative characterization method for emulsification based on multiple parameters such as water separation rate, emulsion viscosity, stability factor, dynamic and static emulsification particle size, droplet coalescence, microfluidic visualized in-situ emulsification and seepage, thereby achieving accurate definition of the emulsification strength of different oil recovery systems.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for evaluating the oil displacement performance of an oil displacement system, the method comprising:

[0011] Determine the matching parameters between the flooding system and reservoir performance;

[0012] Determine the weights of the matching parameters and determine the qualified value ranges of the matching parameters;

[0013] Determine the flooding system that does not meet the qualified value range of the matching parameters as an unqualified system, and determine the flooding system that meets the qualified value range of the matching parameters as a qualified system;

[0014] Scoring the values ​​of each matching parameter in the qualified system individually and performing sub-combination scoring on the sub-combinations of matching parameters, and apportioning the sub-combination scores to each matching parameter according to the weight coefficients within the sub-combinations to obtain a comprehensive score for the matching parameters;

[0015] The overall score of the qualified system is calculated based on the weights and comprehensive scores of the matching parameters, and the oil displacement system is quantitatively characterized.

[0016] Preferably, the matching parameters include any one or a combination of at least two of the following: water separation rate, emulsion viscosity, stability factor, dynamic and static emulsification particle size, expansion rheological properties, droplet coalescence time, microscopic sweep efficiency or porous medium short core migration and retention capacity, preferably a combination of expansion rheological properties, droplet coalescence time, microscopic sweep efficiency and porous medium short core migration and retention capacity.

[0017] In the present invention, the water separation rate Wr, that is, the separation ratio of water in the lower phase of the oil-water emulsion, is quantitatively equal to the ratio of the separation volume of water to the original volume.

[0018] The emulsion viscosity μ in the present invention refers to the Brookfield viscosity after the oil displacement system is mixed with crude oil.

[0019] The stability factor TSI in the present invention is a measure of the stability of the emulsion. The smaller the value, the more stable the emulsion formed by the oil-water system.

[0020] In the present invention, the dynamic and static emulsification particle size d is also a quantitative representation of the emulsion performance. The smaller the particle size, the smaller the dynamic change, and the better the emulsion stability.

[0021] In the present invention, the dilational rheological property Dr is another quantitative characterization of the emulsion performance, and the interfacial dilational modulus and phase angle are two important parameters in the characterization of dilational rheological properties. Among them, the dilational modulus (ε) is defined as the change in interfacial tension with interfacial area. It is a direct characterization of the strength of the oil-water interface film and is composed of dilational elasticity and dilational viscosity. The phase angle (θ) is the phase difference between the interfacial tension and interfacial area change curves, which is quantitatively equal to the ratio of the viscous modulus to the elastic modulus. The larger the dilational modulus and the smaller the phase angle, the more stable the adsorption film formed by the surfactant molecules on the oil-water interface and the higher the film strength.

[0022] In the present invention, the droplet coalescence time t is an important parameter to characterize the droplet coalescence ability. The longer the time, the weaker the droplet drainage ability, the greater the coalescence difficulty, and the higher the film strength of the emulsion.

[0023] In the present invention, the microscopic sweep efficiency η is an important parameter to characterize the dynamic seepage capacity of microfluidics. The higher the sweep efficiency, the better the effect of improving oil recovery rate.

[0024] In the present invention, the migration and retention capacity Rc of the porous medium short core is the ratio of the oil-water two-phase seepage pressure difference before the emulsion is formed to the oil-water two-phase injection seepage pressure difference after the emulsion is formed after in-situ emulsification in the short core. It is combined with the results of oil displacement experiments to guide the screening of oil displacement systems. The larger the Rc, the weaker the emulsion retention capacity.

[0025] Preferably, the method limits the qualified value range of the water separation rate to 15-90%, for example, it can be 15%, 24%, 32%, 40%, 49%, 57%, 65%, 74%, 82% or 90%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0026] Preferably, the qualified value range of the emulsion viscosity is 1.0 to 40.0 cp, for example, it can be 1.0 cp, 1.4 cp, 1.7 cp, 2 cp, 2.4 cp, 2.7 cp, 3 cp, 3.4 cp, 3.7 cp, 4.0 cp, 10 cp, 15 cp, 20 cp, 25 cp, 30 cp, 35 cp or 40 cp, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0027] Preferably, the qualified value range of the stability factor is 0.8 to 10, for example, it can be 0.8, 1.83, 2.85, 3.87, 4.89, 5.92, 6.94, 7.96, 8.98 or 10, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0028] Preferably, the qualified value range of the dynamic and static emulsification particle size is 60 to 180 μm, for example, it can be 60 μm, 75 μm, 80 μm, 100 μm, 110 μm, 120 μm, 140 μm, 150 μm, 160 μm or 180 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0029] Preferably, the qualified value range of the expansion rheological properties is 20 to 60 mN / m, for example, it can be 20 mN / m, 25 mN / m, 29 mN / m, 34 mN / m, 38 mN / m, 43 mN / m, 47 mN / m, 52 mN / m, 56 mN / m or 60 mN / m, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] Preferably, the qualified value range of the droplet coalescence time is 2 to 50 s, for example, it can be 2 s, 8 s, 13 s, 18 s, 24 s, 29 s, 34 s, 40 s, 45 s or 50 s, etc., but is not limited to the listed values, and other values ​​not listed in this range are also applicable.

[0031] Preferably, the qualified value range of the microscopic wave efficiency is 50-95%, for example, it can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] Preferably, the retention capacity of the porous medium short core is in the range of 0.6 to 2.5, for example, it can be 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.5, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0033] Preferably, the sub-combination includes a first sub-combination and a second sub-combination.

[0034] Preferably, the first sub-combination is droplet coalescence time and dilation rheological properties.

[0035] The present invention further prefers droplet coalescence time and expansion rheological properties as the first sub-combination for combined scoring. This is because the combination of the two reflects the strength of the adsorption film formed by surfactant molecules on the oil-water interface, strengthens the effect of the membrane strength of the adsorption film on oil displacement, and makes the final evaluation more accurate.

[0036] Preferably, the sub-weight of the droplet coalescence time in the first sub-combination is 0.5 to 0.6, for example, it can be 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.58 or 0.6, and the sub-weight of the expansion rheological properties in the first sub-combination is 0.4 to 0.5, for example, it can be 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46 or 0.5, etc.

[0037] Preferably, the second sub-combination is a combination of a stabilization factor and a dynamic and static emulsification particle size.

[0038] The present invention further prefers to conduct combined evaluation based on the sub-combination of stability factor and dynamic and static emulsification particle size, because the two factors together reflect the stability of the emulsion formed by the oil-water system, strengthen the effect of the emulsion stability on oil displacement, and make the final evaluation more accurate.

[0039] Preferably, the sub-weight of the stability factor in the second sub-combination is 0.3 to 0.45, for example, it can be 0.3, 0.31, 0.32, 0.33, 0.35, 0.38, 0.40, 0.41, 0.42, 0.43, 0.44 or 0.45, etc., and the sub-weight of the dynamic and static emulsification particle size in the second sub-combination is 0.55 to 0.7, for example, it can be 0.55, 0.58, 0.59, 0.6, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67 or 0.7, etc.

[0040] Preferably, the individual scoring and sub-combination scoring are each independently performed using an expert scoring method.

[0041] Preferably, the expert scoring method includes: firstly, the experts determine the optimal range value of each matching parameter, and then divide it into 4 different levels according to the degree of proximity to the optimal range value, and the 4 different levels are excellent, good, medium and qualified.

[0042] Preferably, each of the levels corresponds to a different score.

[0043] Preferably, the weight range of the water separation rate is 0.05 to 0.1, for example, it can be 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, but is not limited to the listed values. Other values ​​not listed in the range are also applicable.

[0044] Preferably, the weight range of the emulsion viscosity is 0.05 to 0.1, for example, it can be 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0045] Preferably, the weight range of the stability factor is 0.1 to 0.15, for example, it can be 0.1, 0.11, 0.12, 0.13, 0.14 or 0.15, but is not limited to the listed values. Other values ​​not listed in the range are also applicable.

[0046] Preferably, the weight range of the dynamic and static emulsification particle size is 0.2 to 0.25, for example, it can be 0.2, 0.21, 0.22, 0.23, 0.24 or 0.25, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0047] Preferably, the weight range of the expansion rheological property is 0.10 to 0.2, for example, it can be 0.10, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.2, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0048] Preferably, the weight range of the droplet coalescence time is 0.15 to 0.25, for example, it can be 0.15, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24 or 0.25, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0049] Preferably, the weight range of the microscopic sweep efficiency is 0.05 to 0.15, for example, it can be 0.05, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14 or 0.15, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0050] Preferably, the weight range of the short core retention capacity of the porous medium is 0.1 to 0.3, for example, it can be 0.1, 0.13, 0.15, 0.17, 0.19, 0.22, 0.24, 0.26, 0.28 or 0.3, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0051] Preferably, the oil displacement system comprises a single-component surfactant, a multi-component surfactant, or a combination of a surfactant and other components.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) The method for evaluating the oil displacement performance of the oil displacement system provided by the present invention is based on the performance characterization of multiple parameters such as water separation rate, emulsion viscosity, stability factor, dynamic and static emulsification particle size, expansion rheological properties, droplet coalescence, microfluidic visualization in situ emulsification and seepage, and short core retention capacity of porous media, so as to achieve accurate definition of the emulsification strength of different oil displacement systems;

[0054] (2) The method for evaluating the oil displacement performance of the oil displacement system provided by the present invention can reveal the surfactant / polymer interface and bulk molecular interaction mechanism through the above-mentioned evaluation mechanism, and deepen the synergistic enhancement law of the oil displacement system;

[0055] (3) The method for evaluating the oil recovery performance of the oil recovery system provided by the present invention is based on the quantitative characterization of multiple parameters of the emulsification control oil recovery system, clarifies the rules of system emulsification control and pore throat matching and its key role in the large-scale recovery rate of binary composite drive, reveals the key technical indicators of emulsification control, deepens the understanding of the emulsification control oil recovery mechanism, and clarifies the potential for significantly improving the recovery rate of oil reservoirs with different physical properties and the main technical direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a flow chart of the method for evaluating the oil displacement performance of an oil displacement system provided by the present invention. DETAILED DESCRIPTION

[0057] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0058] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0059] As a specific embodiment of the present invention, a method for evaluating the oil displacement performance of an oil displacement system is provided, such as Figure 1 As shown, the method includes the following steps:

[0060] Determine the matching parameters between the flooding system and reservoir performance;

[0061] Determine the weights of the matching parameters and determine the qualified value ranges of the matching parameters;

[0062] Determine the flooding system that does not meet the qualified value range of the matching parameters as an unqualified system, and determine the flooding system that meets the qualified value range of the matching parameters as a qualified system;

[0063] Scoring the values ​​of each matching parameter in the qualified system individually and performing sub-combination scoring on the sub-combinations of matching parameters, and apportioning the sub-combination scores to each matching parameter according to the weight coefficients within the sub-combinations to obtain a comprehensive score for the matching parameters;

[0064] The overall score of the qualified system is calculated based on the weights and comprehensive scores of the matching parameters, and the oil displacement system is quantitatively characterized.

[0065] Example 1

[0066] This example provides a method for evaluating the oil displacement performance of an oil displacement system. The method tests four different unknown single-component surfactants, designated as anionic nonionic surfactant A, anionic surfactant B, linear betaine C, and branched betaine D. The evaluation method comprises the following steps:

[0067] (1) Determine the matching parameters between the oil displacement system and reservoir performance

[0068] The selected matching parameters include water separation rate, emulsion viscosity, stability factor, dynamic and static emulsification particle size, dilational rheological properties, droplet coalescence time, microscopic sweep efficiency and short core retention capacity of porous media.

[0069] The test methods for each matching parameter are as follows:

[0070] The water separation rate Wr, that is, the ratio of water separation in the lower phase of the oil-water emulsion, is quantitatively equal to the ratio of the separation volume of water to the original volume.

[0071] Emulsion viscosity μ: After mixing the displacement system and crude oil in a volume ratio of 1:1, the Brookfield viscosity is tested at a speed of 6 r / min. 1 ml of crude oil emulsion with good stability is aspirated and placed in the center of the cone plate of the viscometer to ensure sample homogeneity. The viscosity value is the steady-state value that does not change within 30 s.

[0072] The stability factor (TSI) is measured optically. A fully emulsified crude oil emulsion (the volume ratio of the displacement system to the crude oil is 1:1, the same below) is immediately placed in a sample cell. An optical scan is performed every 30 seconds for 2 hours. The sum of the differences in light intensity before and after each scan is the stability factor.

[0073] The dynamic and static emulsion particle size d is measured using a Malvern particle size analyzer. 1 ml of crude oil emulsion at different times is diluted 500 times with simulated formation water and placed in a quartz tank. The peak value of the distribution of the test curve is considered to be the current emulsion particle size.

[0074] To measure the dilational rheological property, an 8μL oil droplet was immersed in a quartz cell filled with a surfactant solution via a curved needle. An oscillator applied a sinusoidal perturbation of dA / A = 10% to the oil droplet. The first step, in which the perturbation frequency remained constant, was called the dynamic mode process and was fixed at 0.1 Hz. After the dilational modulus remained constant, the second step, in which the perturbation frequency varied, was called the variable frequency process. The oscillation frequency was decreased in the order of 0.1, 0.055, 0.03, 0.017, 0.009, and 0.005 Hz. The interfacial dilational modulus and phase angle were measured, and the dilational rheological property, Dr, was calculated.

[0075] Droplet coalescence time t. During the test, a syringe is used to form two oil droplets of similar size through a steel needle, and the whole is immersed in a quartz tank filled with a surfactant solution. The upper needle remains stationary and is connected to a micro-force balance. The lower needle slowly rises along the needle tip until the two oil droplets contact, squeeze, and finally coalesce into a complete large oil droplet. The process from the initial contact of the two oil droplets to the completion of coalescence is the coalescence time t.

[0076] Microscopic sweep efficiency η: During the test, a surfactant was injected into an oil-saturated heterogeneous glass model at a rate of 0.1 μL / min. The seepage and sweep conditions in the model were monitored and recorded in real time using a stereo microscope. When the volume of the oil in the model stopped changing, a photo was taken and grayscale processed. The grayscale change of the oil phase is the microscopic sweep efficiency.

[0077] The retention capacity Rc of a short core of a porous medium is determined by taking a natural core or a short Berea core of a target permeability of a reservoir with a length of 5.0 cm and a diameter of 2.5 cm, evacuating it and saturating it with brine, placing it in a constant temperature drying oven, and keeping it at a constant temperature of 45°C for more than 3 hours to allow the water to fully wet the core and the core as a whole to reach the experimental temperature; a branch line simultaneously injects 1.5 PV of crude oil and brine into the core, with a volume ratio of crude oil to brine of 1:1 and an injection rate of 0.3 mL / min. The pressure value during the injection process is recorded every 5 minutes. The average pressure during the injection of 1 to 1.5 PV is taken and recorded as p wo ; The pipelines simultaneously inject 10PV of crude oil and chemical flooding system solution into the core, with a volume ratio of crude oil to chemical flooding system solution of 1:1 and an injection rate of 0.3mL / min; The pipelines simultaneously inject 3PV of crude oil and brine into the core, with a volume ratio of crude oil to brine of 1:1 and an injection rate of 0.3mL / min. The pressure values ​​during the injection process are recorded every 5 minutes. The average pressure during the injection of 2 to 3PV is recorded as p ewo ; Calculate Rc, the calculation formula of Rc is

[0078] The test results of the above matching parameters are shown in Table 1.

[0079] Table 1

[0080]

[0081] (2) Determine the weights of the matching parameters and the qualified value range of the matching parameters. The results are shown in Table 2.

[0082] Table 2

[0083]

[0084] (3) The displacement system that does not meet the qualified value range of the matching parameters is judged as an unqualified system, and the displacement system that meets the qualified value range of the matching parameters is judged as a qualified system; among them, the anionic surfactant B does not meet the range of the droplet coalescence time t and is judged as an unqualified system.

[0085] (4) The values ​​of each matching parameter in the qualified system are scored individually and the sub-combinations between the matching parameters are scored as sub-combinations, and the sub-combination scores are apportioned to each matching parameter according to the weight coefficients within the sub-combinations to obtain the comprehensive scores of the matching parameters.

[0086] Five experts were selected to determine the optimal range values ​​for each matching parameter, and the upper and lower limits were averaged to obtain the optimal range values. The results were then divided into four different levels according to the degree of proximity to the optimal range values. The four different levels were excellent, good, medium, and qualified, with corresponding scores of 1, 0.8, 0.6, and 0.4, respectively. Excellent and good must fall within the optimal range values, while medium and qualified are not within this range. The average results of the five experts are shown in Table 3. The units refer to the units in Table 2.

[0087] Table 3

[0088]

[0089] The first sub-combination includes the droplet coalescence time and the expansion rheological property. The sub-weight of the droplet coalescence time in the first sub-combination is 0.5, and the sub-weight of the expansion rheological property in the first sub-combination is 0.5.

[0090] The second sub-combination is a combination of the stability factor and the dynamic and static emulsified particle size. The sub-weight of the stability factor in this second sub-combination is 0.35, and the sub-weight of the dynamic and static emulsified particle size in this second sub-combination is 0.65. These sub-weights are redistributed to the corresponding matching parameters to obtain the scores for each matching parameter, as shown in Table 4.

[0091] Table 4

[0092]

[0093]

[0094] (5) The overall score of the qualified system is calculated based on the weights and comprehensive scores of the matching parameters, and the oil displacement system is quantitatively characterized. The calculation results are shown in Table 5.

[0095] Table 5

[0096] Anionic nonionic surfactant A Straight chain betaine C Branched chain betaine D Overall score 0.9075 0.7655 0.6035

[0097] As can be seen from Table 5, the anionic nonionic surfactant A should have the best oil displacement effect, followed by the linear betaine C, the last is the branched betaine D, and the worst is the anionic surfactant B which was judged to be unqualified.

[0098] To verify the above conclusions, oil recovery experiments were carried out using the above different oil recovery systems, and various indicators during the oil recovery process were measured, including the EOR oil recovery rate. The results are shown in Table 6.

[0099] The EOR testing method is as follows: A 30×4.5×4.5 cm core is vacuum-saturated with water, and the pore volume is measured. The core is then heated in a 45°C thermostat for 15 hours. The core is saturated with crude oil and then heated in a 45°C thermostat for 20 hours. Water flooding is performed until the outlet water cut reaches 98%, and the water flooding recovery is calculated. A 0.3 PV (0.3 PV) corresponding system plus a 0.2 PV (0.2 PV) polymer protective slug is injected at 30 mPa·s. Subsequent water flooding is performed until the outlet water cut reaches 98%, and the recovery is calculated.

[0100] Table 6

[0101]

[0102] As can be seen from Table 6 above, the method for evaluating the oil displacement performance of an oil displacement system provided by the present invention can well evaluate an oil displacement system with excellent oil displacement effect. Oil displacement systems with high oil displacement effect can be well screened out only through indoor tests. Both single-component and multi-component systems can be evaluated from multiple angles, which reduces the screening cost of oil displacement agents and makes the evaluation more accurate.

[0103] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for evaluating the oil displacement performance of an oil displacement system, characterized in that: The method comprises: Determine the matching parameters between the oil displacement system and reservoir performance; Determine the weight of the matching parameter and determine the qualified value range of the matching parameter; Determine the oil displacement system that does not meet the qualified value range of the matching parameter as an unqualified system, and determine the oil displacement system that meets the qualified value range of the matching parameter as a qualified system; The values ​​of each matching parameter in the qualified system are scored separately and the sub-combinations between the matching parameters are scored as sub-combinations, and the sub-combination scores are apportioned to each matching parameter according to the weight coefficients within the sub-combinations to obtain a comprehensive score of the matching parameters; The overall score of the qualified system is calculated according to the weights and comprehensive scores of the matching parameters, and the oil displacement system is quantitatively characterized.

2. The method according to claim 1, characterized in that The matching parameters include any one or a combination of at least two of the following: water separation rate, emulsion viscosity, stability factor, dynamic and static emulsification particle size, expansion rheological properties, droplet coalescence time, microscopic sweep efficiency or porous medium short core migration retention capacity.

3. The method according to claim 1 or 2, characterized in that: The method limits the qualified value range of the water separation rate to 15-90%; Preferably, the qualified value range of the emulsion viscosity is 1.0 to 40.0 cp; Preferably, the qualified value range of the stability factor is 0.8 to 10; Preferably, the qualified value range of the dynamic and static emulsification particle size is 60 to 180 μm.

4. The method according to any one of claims 1 to 3, characterized in that: The qualified value range of the expansion rheological property is 20 to 60 mN / m; Preferably, the qualified value range of the droplet coalescence time is 2 to 50 s; Preferably, the qualified value range of the microscopic sweep efficiency is 50-95%; Preferably, the migration and retention capacity of the porous medium short core is in the range of 0.6 to 2.

5.

5. The method according to any one of claims 1 to 4, characterized in that: The sub-combination includes a first sub-combination and a second sub-combination; Preferably, the first sub-combination is droplet coalescence time and dilation rheological properties; Preferably, the sub-weight of the droplet coalescence time in the first sub-combination is 0.5-0.6, and the sub-weight of the expansion rheological property in the first sub-combination is 0.4-0.

5.

6. The method according to claim 5, characterized in that The second sub-combination is a combination of a stabilization factor and a dynamic and static emulsification particle size; Preferably, the sub-weight of the stability factor in the second sub-combination is 0.3-0.45, and the sub-weight of the dynamic and static emulsification particle size in the second sub-combination is 0.55-0.

7.

7. The method according to any one of claims 1 to 6, characterized in that: The individual scoring and sub-combination scoring are each independently performed using an expert scoring method.

8. The method according to claim 7, characterized in that The expert scoring method includes: firstly, the experts determine the optimal range value of each matching parameter, and then divide it into four different levels according to the degree of proximity to the optimal range value, and the four different levels are excellent, good, medium and qualified; Preferably, each of the levels corresponds to a different score.

9. The method according to any one of claims 1 to 8, characterized in that: The weight range of the water separation rate is 0.05 to 0.1; Preferably, the weight range of the viscosity of the emulsion is 0.05 to 0.1; Preferably, the weight range of the stability factor is 0.1 to 0.15; Preferably, the weight range of the dynamic and static emulsification particle size is 0.2 to 0.

25.

10. The method according to any one of claims 1 to 9, characterized in that: The weight range of the dilational rheological properties is 0.10 to 0.2; Preferably, the weight range of the droplet coalescence time is 0.15 to 0.25; Preferably, the weight range of the microscopic sweep efficiency is 0.05 to 0.15; Preferably, the weight range of the porous medium short core migration and retention capacity is 0.1 to 0.3.

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