A novel method and system for evaluating the enrichment effect of polymer flooding on crude oil.

Abstract

This invention discloses a novel method and system for evaluating the enrichment effect of crude oil in polymer flooding. The method includes: acquiring basic data during the polymer flooding process based on a physical simulation experiment using sand-filled pipes; calculating, based on the basic data, peak significance index, front steepness index, mobility contrast index, pressure anomaly index, water-bearing disturbance intensity index, and oil wall stability advancement coefficient; calculating the comprehensive evaluation index of the oil wall based on the above indicators; and determining the level of the oil wall's development and migration effect based on the values. This invention overcomes the limitations of traditional single saturation peak evaluation by integrating multi-dimensional indicators and applying stability constraints. It can comprehensively, quantitatively, and stably reflect the enrichment degree, morphological characteristics, dynamic response, and advancement state of the oil wall, providing a unified and objective decision-making basis for optimizing polymer flooding schemes.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction, specifically, it relates to a new method and system for evaluating the enrichment effect of polymer flooding crude oil. Background Technology

[0002] As major oilfields enter the later stages of high water-cut development, the efficiency of conventional waterflooding gradually decreases, and the remaining oil distribution becomes increasingly dispersed with significantly enhanced heterogeneity. To maintain stable production and tap the potential of older oilfields, tertiary oil recovery technologies, represented by polymer flooding, are widely used. This technology increases the viscosity of the displacing fluid and improves the oil-water mobility ratio by adding polymers (such as HPAM) to the injected water, thereby expanding the swept volume and enhancing oil recovery.

[0003] The core oil recovery mechanism of polymer flooding lies in the enrichment and overall advancement of crude oil at the displacement front. After the polymer solution is injected into the formation, its high viscosity helps to suppress fingering and water channeling, allowing crude oil to gradually accumulate in the front region, forming an "oil wall" with a significantly higher oil saturation than the surrounding area. The formation and stable advancement of the oil wall are key to the effective utilization of remaining oil in polymer flooding, and its spatial scale, continuity, enrichment level, and advancement state directly affect the final recovery effect.

[0004] Current quantitative evaluation methods for oil walls mainly rely on the Buckley-Leverett displacement theory or numerical simulations, identifying oil walls by analyzing oil saturation distribution curves. However, in highly heterogeneous, low-permeability, or high-viscosity crude oil reservoirs, the peak oil saturation is often indistinct due to interlayer differences, fingering, and emulsification, and the curve may exhibit a gentle plateau or gradual change. In such cases, although displacement is still effectively advancing, it can easily be misjudged as a lack of oil wall development, leading to evaluation bias. Furthermore, the oil wall itself is a dynamic spatiotemporal structure involving complex mechanisms such as multiphase flow, rheology, and seepage field reconstruction. A single peak saturation value at a particular moment cannot comprehensively reflect its enrichment capacity and displacement efficiency. Therefore, developing a unified evaluation index system that can quantitatively reflect the enrichment effect of crude oil is of great significance. Summary of the Invention

[0005] After long-term research, the inventors unexpectedly discovered that the method for evaluating the enrichment effect of polymer flooding crude oil, which includes the following steps, can provide a unified evaluation index system for comprehensively and quantitatively reflecting the enrichment effect of crude oil.

[0006] Therefore, based on the above findings, in a first aspect, the present invention provides a method for evaluating the enrichment effect of polymer flooding crude oil, comprising the following steps:

[0007] Based on the physical simulation experiment of the sand-filled pipe, basic data of the polymer flooding process were obtained. The basic data includes oil saturation distribution data, mobility response data, water content change data, pressure drop response data, and displacement front position data.

[0008] Based on the oil saturation distribution data, a peak significance index was calculated to characterize the degree of oil wall enrichment. The calculation formula is as follows: ,in, The initial oil saturation, Residual oil saturation, This represents the peak oil saturation.

[0009] Based on the oil saturation distribution data, the front steepness index, used to characterize the morphology and gradient features of the oil wall front, is calculated. The calculation formula is as follows: ,in, This represents the spatial gradient of oil saturation at the steepest point on the leading edge of the oil wall.

[0010] Based on the fluidity response data, a fluidity contrast index is calculated to characterize the fluidity regulation capability of the displacing fluid. The calculation formula is as follows: ,in, The leading-edge mobility under polymer-driven conditions is defined as krw(Sw) / μ p , The mobility under baseline water drive conditions is defined as krw(Sw) / μ w krw(Sw) is the relative permeability of the aqueous phase, μ p The viscosity of the polymer solution is μ. w The viscosity of the aqueous phase;

[0011] Based on the pressure drop response data, calculate the pressure anomaly index to characterize the dynamic anomalies in the displacement process. The calculation formula is as follows: ,in, This represents the average pressure drop during the asphalt wall advancement stage. The average pressure drop under baseline displacement or expected stable displacement;

[0012] Based on the moisture content change data, calculate the moisture content disturbance intensity index to characterize the dynamic response of the oilwall production. The calculation formula is as follows: ,in, To analyze the maximum rate of change of moisture content within the window, This represents the average rate of change in moisture content within the same analysis window.

[0013] Calculate the oil wall stability advance coefficient based on the displacement leading edge position data. The calculation formula is as follows: ,in, Let the standard deviation of the oil wall advance speed be , This represents the average speed of the oil wall advance;

[0014] According to the peak significance index Frontal steepness index Flowability Comparison Index Abnormal stress index Water content disturbance intensity index and the stability advancement coefficient of the oil wall Calculate the comprehensive evaluation index of the paint wall The calculation formula is as follows: ,in This is the stability advancement coefficient of the oil wall, which applies stability constraints to the comprehensive evaluation of the oil wall. to Here are the weighting coefficients for each indicator, and ;

[0015] According to the comprehensive evaluation index of the oil wall The numerical value is used to determine the grade of the development and migration effect of the oil wall.

[0016] In one implementation, the basic data is obtained through a physical simulation experiment using a sand-filled pipe. This experiment includes: evacuating the sand-filled pipe, injecting simulated formation water to saturate it, and then injecting simulated crude oil to establish an initial oil-bearing state, thereby obtaining the oil saturation distribution data; performing baseline water flooding until the water cut reaches a predetermined value, and then switching to polymer flooding to obtain the water cut change data; during polymer flooding, acquiring the oil saturation distribution data through image acquisition, acquiring the pressure drop response data through a pressure sensor, acquiring the water cut change data through metering the produced liquid, and acquiring the displacement front position data through tracer tracking.

[0017] In one embodiment, the oil saturation distribution data includes initial oil saturation. Residual oil saturation Peak oil saturation One-dimensional oil saturation distribution curve Spatial gradient of oil saturation at the steepest point of the oil wall The mobility response data includes the relative permeability of the aqueous phase krw(Sw) and the viscosity of the aqueous phase μ. w and polymer solution viscosity μ p The moisture content change data includes moisture content Maximum strength due to change in moisture content over time and the average intensity of change within the same analysis window The voltage drop response data includes voltage drops at different times. Pressure drop response at the leading edge of the oil wall Compared with the voltage drop response under the baseline or expected steady-state operating conditions. The displacement leading edge position data includes the instantaneous advance velocity of the oil wall in each time period. Standard deviation of the oil wall advance speed and the average speed of the oil wall advance .

[0018] In one implementation, the weighting coefficients w1, w2, w3, w4, and w5 represent their relative importance in the comprehensive evaluation. They are flexibly adjusted according to different reservoir conditions and data sources to make the evaluation method adaptable to different reservoir types and experimental / field conditions.

[0019] In one implementation plan, based on the comprehensive evaluation index of the paint wall The rating determination includes: when When, it is judged as a significant oil wall; when At that time, it was judged to be a medium-grade paint wall; and when At that time, it is determined to be a weak oil wall or no oil wall has been formed.

[0020] In one implementation, the method for identifying the oil wall enrichment zone includes: identifying areas on the oil saturation distribution curve where the oil saturation is significantly higher than that upstream and downstream in a continuous spatial segment, and where the area maintains its morphology intact and advances unidirectionally toward the production end in multiple consecutive time steps, thus confirming it as an oil wall enrichment zone.

[0021] In another aspect, the present invention provides an evaluation system for the enrichment effect of crude oil in polymer flooding, comprising: a data acquisition module for acquiring basic data during the polymer flooding process, including oil saturation profile data, pressure data, and production dynamic data; an index calculation module for executing the index calculation steps in the evaluation method for crude oil enrichment effect in polymer flooding, and obtaining peak significance index, front steepness index, mobility comparison index, pressure anomaly index, water disturbance intensity index, and oil wall stability advancement coefficient; and a comprehensive evaluation module for calculating the comprehensive evaluation index of the oil wall based on the results of the index calculation module, and outputting the crude oil enrichment effect evaluation level according to a preset grading standard. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or related technologies, the accompanying drawings used in describing this invention or related technologies will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without any inventive effort.

[0023] Figure 1 This is a flowchart of a sand-filled tube displacement experiment.

[0024] Figure 2 This is a schematic diagram of a one-dimensional model of polymer flooding and the distribution of oil saturation with distance.

[0025] Figure 3 It is the law of change of production pressure difference over time.

[0026] Figure 4 It is the comprehensive evaluation index of the paint wall. Distribution diagram.

[0027] Figure Labels

[0028] 1. Distilled water, 2. Flow pump, 3. Simulated formation water, 4. Simulated crude oil, 5. Chemical reagent, 6. Back pressure valve, 7. Sand packing pipe, 8. Measuring cylinder, 9. Pressure data acquisition device, 10. Pressure sensor Detailed Implementation

[0029] To better illustrate the technical means and effects of the present invention, the invention is further described below in conjunction with non-limiting embodiments. These embodiments (including descriptions mentioned in the embodiments) are intended to illustrate the implementation of the invention and are not intended to limit the scope of any claim. According to the present invention, those skilled in the art will understand that many changes can be made to the specific embodiments disclosed without departing from the spirit and scope of the invention, and the same or similar results can still be obtained.

[0030] In this paper, the term "oil wall" refers to the oil-rich zone formed during polymer displacement where, due to improved mobility, crude oil at the displacement front spatially enriches, resulting in an oil saturation significantly higher than that of the upstream and downstream regions. Its core characteristics are "local enrichment" and "overall propulsion."

[0031] In this paper, the term "peak significance index" is a dimensionless index used to quantitatively evaluate the enrichment degree of the oil wall. It reflects the enrichment efficiency of the oil wall peak relative to the available crude oil space by normalizing the maximum oil saturation of the oil wall to the difference between the initial oil saturation and the residual oil saturation.

[0032] In this paper, the term "front steepness index" is used as a dimensionless index to quantitatively evaluate the degree of morphological concentration at the oil wall front. It characterizes the steepness of the oil wall front by measuring the spatial gradient of the maximum oil saturation at the front. The larger the gradient, the more concentrated the front is, and the closer it is to piston-like displacement.

[0033] In this paper, the term "mobility comparison index" is used as a dimensionless index to quantitatively evaluate the mobility regulation capability of polymer flooding. It reflects the relative strength of the polymer's improvement in mobility ratio by comparing the logarithmic ratio of the equivalent mobility at the polymer flooding front to that of the baseline water flooding.

[0034] In this paper, the term "pressure anomaly index" is used as a dimensionless index to quantitatively evaluate the pressure response caused by the remodeling of the seepage field during the formation and advancement of the oil wall. It reflects the impact of the oil wall on flow resistance by comparing the average pressure drop during the oil wall advancement stage with the pressure drop under the baseline condition.

[0035] In this paper, the term "water content disturbance intensity index" is used to quantitatively evaluate the impact of oilwall advancement on the dynamics of water content at the production end. It reflects the degree of disturbance to production dynamics caused by oilwall breakthrough or advancement by analyzing the ratio of the peak value to the mean value of the rate of change in water content.

[0036] In this paper, the term "residual oil saturation" refers to the percentage of crude oil remaining in the porous medium after sufficient displacement, which cannot be effectively recovered, under existing displacement technologies (such as polymer flooding) and economic conditions. It is a relatively stable final state value that reflects the theoretical limit of oil recovery for a given reservoir and displacement system.

[0037] In this paper, the term "maximum oil saturation within the oil wall enrichment zone" refers to the highest value reached on the oil saturation distribution curve within the identified oil wall region during polymer displacement. It represents the peak intensity of crude oil enrichment in the core area of ​​the oil wall and is a core parameter for quantitatively evaluating the degree of oil wall enrichment.

[0038] In a preferred embodiment of the present invention, the acquisition of basic data and the identification of the oil wall are accomplished through a physical simulation experiment using a sand-filled pipe 7, to simulate the migration and enrichment behavior of crude oil in a porous medium during polymer flooding. This model employs a one-dimensional sand-filled pipe model, using corrosion-resistant glass tubing with a diameter of 25 mm, a length of 1 m, and a volume of 490 cm³. 3 The end is equipped with an injection end and a production end. The inside of the sand-filled pipe is filled with sieved quartz sand or artificial core particles to simulate the reservoir pore structure. Its permeability can be controlled by particle size distribution to represent different types of reservoir conditions.

[0039] Before the experiment, the sand-filled pipe 7 was evacuated under vacuum. Distilled water 1 and simulated formation water 3 were then injected into the sand-filled pipe 7 via a horizontal flow pump 2 to fully saturate it. Simulated crude oil 4 was then injected to establish an initial oil-bearing state. The initial oil saturation within the sand-filled pipe 7 was determined using mass balance or volumetric measurement methods. During the experiment, the experimental temperature was controlled by a thermostat, the experimental pressure was controlled by a backpressure valve 6, pressure data at different locations was monitored by a pressure sensor 10, and pressure data throughout the displacement process was recorded by a pressure data acquisition device 9. In the polymer flooding stage, a polymer solution was injected using a chemical agent 5, and the volume of the produced liquid was measured at the extraction end using a measuring cylinder 8 to ensure that the injected polymer solution had stable rheological properties under experimental conditions. The experimental flow chart is shown below. Figure 1 As shown.

[0040] After establishing the initial state, baseline water flooding is first implemented. Once the water cut at the produced end reaches the predetermined high water cut stage, polymer flooding is switched on. The polymer solution concentration, injection rate, and injection slug volume can be set according to the experimental objectives. In order to obtain the position of the polymer flooding leading edge, methylene blue staining agent needs to be added to the polymer solution.

[0041] During polymer flooding, the following basic data are acquired simultaneously along the displacement direction:

[0042] (1) Oil saturation distribution data

[0043] During the experiment, a high-resolution industrial camera was used to capture real-time images of the displacement process along the axial direction of the sand-filled pipe, obtaining a high-definition image sequence of the sand-filled pipe at different time steps of polymer flooding. In the image processing stage, the acquired high-definition images underwent preprocessing, including background subtraction, brightness normalization, and noise filtering, to eliminate interference from uneven illumination and changes in the experimental environment. Subsequently, the processed images were partitioned along the axial direction of the sand-filled pipe, dividing the entire pipe into several equal-length spatial units. Statistical analysis was performed on the pixels within each spatial unit to calculate the average grayscale value or color feature parameters of that unit. Based on the aforementioned calibration relationship, the image feature values ​​of each spatial unit were converted into corresponding oil saturation, thereby obtaining a one-dimensional oil saturation distribution curve along the displacement direction at a certain time step. .

[0044] (2) Data on changes in moisture content

[0045] The water content of the produced liquid is monitored and recorded in real time at the production end. Curves showing the variation of time or injected pore volume number (PV). This data is used to reflect the response to disturbances in the production characteristics during oilwall advancement.

[0046] (3) Pressure drop response data

[0047] High-precision pressure sensors are installed at both ends of the sand-filled pipe to record the pressure changes at the injection and production ends in real time, thus obtaining the pressure drop. By observing the pattern of change over time, the pressure drop response at the leading edge of the oil wall can be obtained. Compared with the voltage drop response under the baseline or expected steady-state operating conditions. Pressure drop data are used to reflect changes in the flow field during polymer flooding and the impact of oil wall formation on flow resistance.

[0048] (4) Displacement leading edge position data

[0049] By combining the results of tracer experiments, the position of the polymer displacement leading edge at different times was determined, thereby obtaining the propulsion trajectory of the displacement leading edge.

[0050] In obtaining After the data is collected, the oil saturation is spatially segmented along the axial direction of the sand-filled pipe. In practice, the length of the sand-filled pipe is discretized into several spatial units, and the oil saturation value at the corresponding position is extracted at each time step to form a continuous spatial profile of oil saturation.

[0051] Furthermore, at every moment ,right Analysis shows that when the oil saturation in a continuous spatial segment is significantly higher than that in its upstream and downstream regions, and this high-value segment moves towards the production end as a whole in adjacent time steps, then this segment is identified as a candidate area for an oil wall. This criterion does not require the oil saturation to form a sharp peak, but rather emphasizes the essential characteristic of "local enrichment + overall advancement," thus avoiding the problem of missed detection caused by indistinct peaks in traditional methods. Figure 2 As shown, the candidate oil wall region in the oil saturation profile is usually a relatively flat but generally higher than the initial oil saturation zone. Its leading and trailing edges can be determined by the change in oil saturation gradient or the relative threshold method.

[0052] Furthermore, to prevent misidentification of localized random enrichment or measurement noise as oil walls, this invention introduces a temporal continuity constraint during the oil wall identification process. Specifically, the spatial position of candidate oil wall regions is tracked across multiple consecutive time steps. If the enriched region maintains its complete shape for at least two consecutive time steps and exhibits a unidirectional advancing trend along the displacement direction, it is confirmed as a genuine oil wall region. This method effectively eliminates transient enrichment phenomena caused by local heterogeneity or experimental perturbations, ensuring that the identified oil walls have stable physical meaning.

[0053] In a preferred embodiment of the present invention, the peak significance index This was achieved through a physical simulation experiment using sand-filled pipes combined with high-definition image recognition technology. After obtaining the oil saturation distribution curve, peak identification processing was performed. Specifically, the maximum oil saturation value was searched within the candidate oil wall region to determine the peak oil saturation. Unlike traditional methods that rely solely on visual estimation of peak values, this invention combines image recognition with numerical inversion to ensure the objectivity and repeatability of peak extraction. Furthermore, by combining the initial experimental state and the later displacement state, the initial oil saturation is determined through image inversion. and residual oil saturation ,in It is usually calculated from images of the initial oil saturation and the sand-filled pipe. It is calculated from the image of the polymer flooding followed by water flooding to the stable high water content stage.

[0054] Based on the above, the peak significance index is calculated using the following formula:

[0055]

[0056] This index represents the enrichment of the oil wall peak relative to the available crude oil space, and is a dimensionless quantity. By adopting a normalized form, the influence of factors such as differences in initial oil saturation and sand filling degree in different experiments on the evaluation results can be effectively eliminated.

[0057] Furthermore, to avoid interference from image noise or local abnormal pixels on peak calculation, this invention preferably introduces spatial averaging processing near the oil wall peak, that is, performing a moving average of the oil saturation over a certain length range before and after the peak position, and using this average value as... The representative value. This processing method can make the peak significance index more stable and avoid evaluation bias caused by single-point extrema.

[0058] In a preferred embodiment of the present invention, the oil wall morphology and leading edge concentration are used to characterize the spatial distribution characteristics and propagation mode of the crude oil enrichment zone during polymer flooding. In the sand-filled tube experiment, the oil saturation distribution obtained by high-definition image recognition inversion is used. A continuous spatial analysis of the oil wall region is performed along the displacement direction. Specifically, at each time step, the oil saturation profile near the leading edge of the oil wall candidate region is locally magnified to highlight the saturation change characteristics during the transition from the enriched region to the undisplaced region. This transition region typically corresponds to the leading edge of the oil wall, and its morphology can reflect whether there are obvious fingering or diffusion phenomena during the oil wall advancement process.

[0059] Furthermore, to quantitatively characterize the concentration at the oil wall front, the spatial gradient of oil saturation is introduced as a morphological index. This is achieved by analyzing the oil saturation distribution function... By taking the derivative in space, the oil saturation gradient distribution can be obtained. The larger the gradient value, the more significant the change in oil saturation over a shorter distance, and the more concentrated and piston-like the oil wall leading edge becomes; the smaller the gradient value, the more dispersed the leading edge becomes, and the displacement process tends to be diffuse or fingering.

[0060] Furthermore, to avoid local noise interfering with the gradient results, this invention preferably uses a smoothed saturation profile for gradient calculation. This is achieved by using a moving average... Preprocessing is performed, and then the derivative of the smoothing result is calculated. Subsequently, the maximum absolute value of the gradient is extracted in the leading edge region of the oil wall as a representative quantity of the concentration of the leading edge of the oil wall at that time step.

[0061] Based on this, a frontal steepness index is constructed. Its definition is:

[0062]

[0063] in, The initial oil saturation, This represents the residual oil saturation. By introducing a normalization term, this indicator is made unaffected by different experiments or different initial oil-bearing conditions of reservoirs, thus ensuring good comparability.

[0064] Furthermore, the present invention utilizes multiple consecutive time steps... Statistical analysis can reveal the temporal evolution characteristics of the concentration at the oilwall front. Over a longer timescale... Maintaining a consistently high level indicates that the paint wall has good overall morphological stability; conversely, if... Large fluctuations or a continuous decrease indicate that the leading edge of the oil wall is prone to fingering or breakage.

[0065] In a preferred embodiment of the present invention, flow and dynamic characteristics are used to characterize the seepage response of the displacement system during the formation and advancement of the oil wall. During the sand-filled pipe experiment, high-precision pressure sensors are installed at the injection and production ends to continuously record the pressure changes over time during the displacement process, thereby obtaining the overall pressure drop of the sand-filled pipe. Simultaneously, by combining the injection rate, fluid viscosity, and experimental parameters under polymer solution and baseline water flooding conditions, the equivalent mobility characteristics of different displacement stages were calculated. Equivalent mobility reflects the overall flowability of fluid in porous media under specific displacement conditions and is an important kinetic basis for polymer flooding to improve the mobility ratio and form an oil wall.

[0066] Furthermore, to quantitatively compare the differences in flow capacity between polymer flooding and benchmark water flooding, a mobility comparison index was constructed. In specific implementation, the equivalent mobility corresponding to the polymer-driven stable propulsion stage and the baseline water-driven stable propulsion stage are selected respectively. and And calculate according to the following formula:

[0067]

[0068] in, The equivalent mobility at the oil wall front or within its corresponding time window under polymer flooding conditions is defined as krw(Sw) / μ p , The equivalent mobility under baseline water drive conditions is characterized by krw(Sw) / μ w Where krw(Sw) is the relative permeability of the aqueous phase, μ p The viscosity of the polymer solution is μ. w The viscosity of the aqueous phase is denoted by 1. By introducing a logarithmic form, the sensitivity of this index to the magnitude of changes in mobility can be enhanced, while avoiding the influence of excessively large or small absolute values ​​of mobility on the evaluation results.

[0069] Furthermore, pressure anomaly characteristics are introduced to reflect the remodeling behavior of the seepage field during the formation and advancement of the oil wall. In sand-filled pipe experiments, as the oil wall gradually forms and advances during displacement, it is often accompanied by changes in local flow resistance, manifested as a shift or fluctuation in the pressure drop curve relative to the baseline condition. To quantitatively characterize this phenomenon, this invention defines a pressure anomaly index. The calculation method is as follows:

[0070]

[0071] in, This represents the average pressure drop within the corresponding time window during the oil wall advancement stage. This represents the average pressure drop during the baseline displacement phase or under expected stable displacement conditions. This index is normalized to ensure comparability of pressure drop variations across different experimental scales or injection conditions.

[0072] Furthermore, such as Figure 3 As shown, to avoid interference from instantaneous pressure fluctuations or measurement noise on the evaluation results, this invention preferably selects multiple continuous time steps during the stable advancement stage of the oil wall, averages the pressure drop data over time, and then calculates the pressure anomaly index. This approach helps to highlight the continuous dynamic response brought about by the formation of the oil wall, rather than occasional disturbances.

[0073] In a preferred embodiment of the present invention, the water content disturbance intensity index is used to characterize the degree of influence of the oil wall on the water content characteristics of the produced liquid during the advancement process, thereby providing a supplementary evaluation of the oil wall's effectiveness from a production response perspective. In the sand-filled pipe experiment, the water content of the produced liquid is measured in real time at the production end to obtain a continuous curve of water content change over time. The sampling time interval is kept consistent with the image acquisition and voltage drop recording, thereby achieving time synchronization of multi-source data.

[0074] Furthermore, the moisture content time series is subjected to differential processing to calculate the rate of change of moisture content. This rate of change reflects the intensity of water cut change per unit time. When an oil wall forms and advances within the sand-filled pipe, the water cut at the produced end often fluctuates in stages or rises slowly due to the blocking effect of the oil-rich zone on the water phase. Its rate of change will be significantly different from that of baseline water drive or displacement processes without an oil wall.

[0075] Based on this, the water-bearing disturbance intensity index is introduced. Its definition is:

[0076]

[0077] in, To analyze the maximum rate of change of water content within a time window, This represents the average rate of change in water content within the same time window. By employing a normalized form, this index can effectively eliminate the influence of differences in the magnitude of water content changes under different experimental scales and injection rates.

[0078] Furthermore, in a specific implementation plan, to avoid interference from boundary effects in the early or late stages of displacement on the evaluation results, this invention preferably selects an analysis time window after the oil wall has formed and entered a stable propagation stage to calculate the intensity of water-bearing disturbance. Through this method, the obtained... The indicators can more accurately reflect the impact of the oil wall propulsion itself on the water content behavior of the output, rather than transient factors such as injection switching or experiment termination.

[0079] In a preferred embodiment of the present invention, the oil wall advancement stability evaluation is used to characterize whether the oil wall advances continuously and smoothly during the displacement process, thereby avoiding misjudgments of the oil wall effect based solely on local enrichment or instantaneous response. In the sand-filled pipe experiment, the spatial position of the oil wall leading edge at different time steps has been obtained through the aforementioned oil wall identification method. Using the representative position of the oil wall leading edge as a tracking point, its axial coordinates in continuous time steps are recorded, thereby constructing a functional relationship between the position of the oil wall leading edge and time. By calculating the difference in oil wall leading edge position and time interval between adjacent time steps, the instantaneous advancement velocity of the oil wall in each time period is obtained. .

[0080] Furthermore, a statistical analysis was performed on the oil wall advancement speed sequence. First, the time average of the oil wall advancement speed was calculated. This is used to characterize the average propulsion capability of the oil wall during the overall displacement process; simultaneously, the standard deviation of the propulsion velocity is calculated. This is used to characterize the degree of fluctuation during the oil wall advancement process. If the oil wall advancement is stable, its advancement speed will vary little over different time periods, and the corresponding standard deviation will be low; conversely, if there are obvious leading-edge surges, stagnation, or repeated adjustments, the advancement speed will fluctuate significantly.

[0081] Based on this, the stability propulsion coefficient of the oil wall is constructed. This is used to perform dimensionless quantification of the stability of oil wall propulsion, and it is defined as:

[0082]

[0083] This coefficient ranges from 0 to 1, when When the value is close to 1, it indicates that the oil wall propulsion speed fluctuates less and the propulsion process is stable; when... A lower value indicates significant instability in the oil wall propulsion process. This definition transforms propulsion stability from a qualitative description into a quantitative indicator that can be directly used in comprehensive evaluation.

[0084] Furthermore, to avoid the interference of boundary effects in the early or late stages of the experiment on the stability evaluation, this invention preferably selects the analysis time window after the oil wall has formed and entered the continuous propagation stage, and only performs statistical calculations on the propagation velocity sequence within this stage. This approach helps ensure that the stable propagation coefficient reflects the propagation characteristics of the oil wall itself, rather than the transient effects of the start-up or termination stages.

[0085] In a preferred embodiment of the present invention, based on the completion of the oil wall enrichment significance index, the leading edge morphology concentration index, the flow and dynamic characteristics index, the water-bearing disturbance intensity index, and the propulsion stability evaluation, a comprehensive oil wall evaluation index is further constructed to provide a unified quantitative evaluation of the overall formation quality and propulsion effectiveness of the oil wall during polymer flooding.

[0086] In the specific implementation process, this invention selects the peak significance index. Frontal steepness index Flowability Comparison Index Abnormal stress index and water-bearing disturbance intensity index As a basic quantity for comprehensive evaluation of painted walls. Among them, Used to characterize the enrichment significance of the oil wall relative to the available crude oil space. Used to reflect the concentration at the leading edge of the paint wall. and The dynamic characteristics of oil wall formation are characterized from the perspectives of flowability control capability and pressure drop response. This provides supplementary verification of the oil wall advancement effect from the perspective of output response. All the above indices are in dimensionless or normalized form, ensuring good comparability and additive properties.

[0087] Based on this, the present invention constructs a comprehensive evaluation index for oil walls. The formula for its calculation is:

[0088]

[0089] in, to For the weighting coefficients, satisfying This is used to reflect the relative importance of each individual indicator in the comprehensive evaluation; The stability advancement coefficient of the oil wall is used to constrain the stability of the oil wall advancement process. By introducing the stability advancement coefficient into the comprehensive evaluation index in a multiplicative manner, even if the oil wall performs well in terms of enrichment degree or morphological indicators, if its advancement process is unstable or accompanied by significant fluctuations, its comprehensive evaluation result will still be suppressed, thereby avoiding the misjudgment of "instantaneous enrichment but limited overall effect".

[0090] Furthermore, regarding the setting of weighting coefficients, this invention allows for flexible adjustments based on different reservoir conditions and data sources. For example, in strongly heterogeneous reservoirs or under conditions prone to fingering, the weights of the front steepness index and the stability propulsion coefficient can be appropriately increased; under conditions of significant polymer concentration changes or rheological effects, the weights of the mobility contrast index and the pressure anomaly index can be increased. This weighting adjustment mechanism enables the comprehensive evaluation index of the oilwall to adapt to different reservoir types and experimental / field conditions, rather than being limited to a single application scenario.

[0091] After obtaining the comprehensive evaluation index of the oil wall, this invention further provides a graded evaluation method for the oil wall to facilitate rapid comparison between engineering applications and different displacement schemes. Specifically, according to The numerical value of the oil wall is used to classify oil walls into three categories: significant oil wall, medium oil wall, and weak oil wall or no oil wall. This classification method transforms complex multidimensional evaluation results into intuitive classification criteria, making it easy for engineers to quickly understand and apply.

[0092] In a preferred embodiment, the paint wall grading criteria can be set as follows:

[0093]

[0094] Figure 4This diagram illustrates the distribution of the comprehensive evaluation index for oil walls. The horizontal axis represents different experimental schemes or time windows, and the vertical axis represents the numerical value of the comprehensive evaluation index. The diagram uses different colors or regions to show the index intervals corresponding to three levels: significant oil wall, moderate oil wall, and weak oil wall / no oil wall formation. This facilitates a direct comparison and rapid grading evaluation of the oil wall development effects under different displacement conditions. Figure 4 As shown, when Reaching a significant oil wall level indicates a high degree of oil wall enrichment, concentrated leading-edge morphology, clear dynamic response, and stable propulsion, typically corresponding to a good polymer flooding oil enhancement effect; when At a medium level, it indicates that the oil wall has formed but still has some dispersion or fluctuation; when A lower value indicates insufficient oil wall formation or unstable propagation, requiring optimization and adjustment of injection parameters or development plan.

[0095] The present invention provides an evaluation system for the enrichment effect of polymer flooding crude oil, comprising:

[0096] The data acquisition module is used to acquire basic data during the polymer flooding process: oil saturation distribution data, water content change data, pressure response data, and displacement front position data.

[0097] The index calculation module is used to perform the index calculation steps in the evaluation method of polymer flooding crude oil enrichment effect, obtaining the peak significance index, front steepness index, mobility comparison index, pressure anomaly index, water-bearing disturbance intensity index, and oil wall stability advancement coefficient; and

[0098] The comprehensive evaluation module is used to calculate the comprehensive evaluation index of the paint wall based on the results of the index calculation module. It outputs the evaluation level of the oil wall effect according to the preset grading standard.

[0099] The computer device of the present invention includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of an evaluation method for the enrichment effect of polymer flooding crude oil.

[0100] The computer-readable storage medium of the present invention stores a computer program, which, when executed by a processor, implements the steps of an evaluation method for the effect of polymer-driven oil displacement walls.

[0101] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for evaluating the enrichment effect of polymer flooding on crude oil, comprising: Based on the physical simulation experiment of the sand-filled pipe, basic data of the polymer flooding process were obtained. The basic data includes oil saturation distribution data, mobility response data, water content change data, pressure drop response data, and displacement front position data. Based on the oil saturation distribution data, a peak significance index was calculated to characterize the degree of oil wall enrichment. The calculation formula is as follows: in, The initial oil saturation, Residual oil saturation, This represents the peak oil saturation. Based on the oil saturation distribution data, the front steepness index, used to characterize the morphology and gradient features of the oil wall front, is calculated. The calculation formula is as follows: in, This represents the spatial gradient of oil saturation at the steepest point on the leading edge of the oil wall. Based on the fluidity response data, a fluidity contrast index is calculated to characterize the fluidity regulation capability of the displacing fluid. The calculation formula is as follows: in, The leading-edge mobility under polymer-driven conditions is defined as krw(Sw) / μ p , The mobility under baseline water drive conditions is defined as krw(Sw) / μ w krw(Sw) is the relative permeability of the aqueous phase, μ p The viscosity of the polymer solution is μ. w The viscosity of the aqueous phase; Based on the pressure drop response data, calculate the pressure anomaly index to characterize the dynamic anomalies in the displacement process. The calculation formula is as follows: in, This represents the average pressure drop during the asphalt wall advancement stage. The average pressure drop under baseline displacement or expected stable displacement; Based on the moisture content change data, calculate the moisture content disturbance intensity index to characterize the dynamic response of the oilwall production. The calculation formula is as follows: in, To analyze the maximum rate of change of moisture content within the window, This represents the average rate of change in moisture content within the same analysis window. Calculate the oil wall stability advance coefficient based on the displacement leading edge position data. The calculation formula is as follows: in, Let the standard deviation of the oil wall advance speed be , This represents the average speed of the oil wall advance; According to the peak significance index Frontal steepness index Flowability Comparison Index Abnormal stress index Water content disturbance intensity index and the stability advancement coefficient of the oil wall Calculate the comprehensive evaluation index of the paint wall The calculation formula is as follows: in This is the stability advancement coefficient of the oil wall, which applies stability constraints to the comprehensive evaluation of the oil wall. to Here are the weighting coefficients for each indicator, and ; According to the comprehensive evaluation index of the oil wall The numerical value is used to determine the grade of the development and migration effect of the oil wall.

2. The method according to claim 1, wherein the basic data is obtained through a physical simulation experiment of a sand-filled pipe, the physical simulation experiment of the sand-filled pipe comprising: After vacuuming the sand-filled pipe, simulated formation water is injected and saturated. Then, simulated crude oil is injected to establish an initial oil-bearing state, and the oil saturation distribution data is obtained. After performing baseline water flooding until the water content reaches a predetermined value, the process switches to polymer flooding to obtain the water content change data. During polymer flooding, oil saturation distribution data is acquired through image acquisition, pressure drop response data is acquired through pressure sensors, water content change data is acquired through metering of produced liquid, and displacement front position data is acquired through tracer tracking.

3. The method according to claim 1 or 2, wherein the oil saturation distribution data includes the initial oil saturation. Residual oil saturation Peak oil saturation Spatial gradient of oil saturation at the steepest point of the oil wall The mobility response data includes the relative permeability of the aqueous phase krw(Sw) and the viscosity of the aqueous phase μ. w and polymer solution viscosity μ p The moisture content change data includes moisture content Maximum strength due to change in moisture content over time and the average intensity of change within the same analysis window The voltage drop response data includes voltage drops at different times. Pressure drop response at the leading edge of the oil wall Compared with the voltage drop response under the baseline or expected steady-state operating conditions. The displacement leading edge position data includes the instantaneous advance velocity of the oil wall in each time period. Standard deviation of the oil wall advance speed and the average speed of the oil wall advance .

4. The method according to any one of claims 1 to 3, wherein the weighting coefficients w1, w2, w3, w4, and w5 represent their relative importance in the comprehensive evaluation, and the weighting coefficients are set according to reservoir conditions and data sources to adapt to different reservoir types and experimental or field conditions.

5. The method according to any one of claims 1 to 4, wherein the method is based on the comprehensive evaluation index of the paint wall. The rating process includes: when At that time, it was judged to be a significant oil wall; when At that time, it was judged to be a medium-grade paint wall; when At that time, it is determined to be a weak oil wall or no oil wall has been formed.

6. The method according to claim 1, wherein the method for identifying the oil wall enrichment zone comprises: On the oil saturation distribution curve, areas with significantly higher oil saturation than upstream and downstream within a continuous spatial segment, and which maintain their morphology and advance unidirectionally toward the production end in multiple consecutive time steps, are identified as oil wall enrichment zones.

7. An evaluation system for the enrichment effect of polymer flooding crude oil, comprising: The data acquisition module is used to acquire basic data during the polymer flooding process: oil saturation distribution data, mobility response data, water cut change data, pressure drop response data, and displacement front position data. The index calculation module is used to execute the index calculation steps in the method according to any one of claims 1 to 6 to obtain the peak significance index, front steepness index, mobility comparison index, pressure anomaly index, water-bearing disturbance intensity index and oil wall stability advancement coefficient. The comprehensive evaluation module is used to calculate the comprehensive evaluation index of the oil wall based on the results of the index calculation module, and output the evaluation level of crude oil enrichment effect according to the preset grading standard.

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