Method for evaluating the quality of residual oil re-enrichment

Abstract

The application provides an evaluation method of remaining oil re-enrichment quality, comprising the following steps: (1) obtaining the remaining oil saturation distribution before and after enrichment through remaining oil re-enrichment physical simulation or numerical simulation research; (2) calculating the flow rate curve; (3) calculating the enrichment state value distribution of the remaining oil before and after enrichment; (4) determining the evaluation index and evaluation standard of the remaining oil re-enrichment quality; and (5) evaluating the remaining oil re-enrichment quality. The evaluation method of the remaining oil re-enrichment quality of the high water cut reservoir has the characteristics of simple operation, quick calculation and clear target, can intuitively divide the remaining oil re-enriched in the high water cut reservoir into different types, thereby providing decision reference for tapping the potential of the remaining oil, and has a relatively practical engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development, and more specifically, relates to a method for evaluating the quality of residual oil re-enrichment. Background Technology

[0002] Existing research methods mainly utilize theoretical formulas, physical simulations, and numerical simulations to study the sensitive factors of re-enrichment of remaining oil in high water-cut, closed reservoirs, in order to determine the main controlling factors of re-enrichment of remaining oil. However, no accurate evaluation method has yet been developed for the quality of re-enrichment of remaining oil.

[0003] Existing research methods cannot provide an accurate evaluation of the quality of remaining oil re-enrichment, and lack effective guidance for tapping the potential of remaining oil in high water-cut reservoirs. Summary of the Invention

[0004] The evaluation method for the quality of re-enrichment of residual oil in high water-cut reservoirs provided by this invention is characterized by simple operation, fast calculation and clear objectives. It can intuitively classify the re-enriched residual oil in high water-cut reservoirs into different types, thereby providing a decision-making reference for tapping the potential of residual oil and has practical engineering application value.

[0005] The evaluation method for the quality of residual oil re-enrichment in this application includes: (1) obtaining the saturation distribution of residual oil before and after enrichment through physical simulation or numerical simulation of residual oil re-enrichment; (2) calculating the flow rate curve; (3) calculating the distribution of the enrichment state value of residual oil before and after enrichment; (4) determining the evaluation index and evaluation standard for the quality of residual oil re-enrichment; and (5) evaluating the quality of residual oil re-enrichment.

[0006] Step (1) includes: conducting a detailed reservoir description of the target unit, conducting a water-drive oil physical simulation experiment in combination with the geological parameters of the target unit, and obtaining the remaining oil saturation distribution before and after enrichment.

[0007] Step (2) includes:

[0008] Based on the target unit and its relative permeability curve, the flow distribution curve of the region is calculated using the flow distribution equation.

[0009] According to the water content classification standard, the flow curve is divided into three regions. The saturation points corresponding to these three regions are the boundary points of the oil saturation classification. An enrichment state value α is defined to represent the enrichment state of the remaining oil in each region. That is, when the water content is 0-20%, it is considered low water content, and the remaining oil is considered highly enriched in this region. At this time, the oil saturation is S1-1, and α is assigned a value of 2. When the water content is 20%-90%, it is considered medium-high water content, and the remaining oil is considered moderately enriched in this region. At this time, the oil saturation is S2-S1, and α is assigned a value of 1. When the water content is 90%-100%, it is considered very high water content, and the remaining oil is considered not enriched in this region. At this time, the oil saturation is 0-S2, and α is assigned a value of 0.5.

[0010] Step (3) includes:

[0011] Based on the remaining oil saturation distribution before and after enrichment, the distribution of remaining oil enrichment state values ​​before and after enrichment is calculated according to the saturation points corresponding to the three regions of the flow curve and the enrichment state values ​​corresponding to each region.

[0012] Step (3) further includes:

[0013] The quality of remaining oil enrichment is evaluated based on the remaining oil enrichment index and the utilization potential index.

[0014] The enrichment index is calculated using the following formula:

[0015]

[0016] In the formula:

[0017] S1 i The area corresponding to the highly enriched region after re-enrichment is m. 2 ;

[0018] S2 i The area corresponding to the moderately enriched region after re-enrichment is m. 2 ;

[0019] S3 i The area of ​​the non-enriched region after re-enrichment is m. 2 ;

[0020] m represents the number of grids corresponding to the highly enriched regions after re-enrichment;

[0021] n represents the number of grids corresponding to the moderately enriched region after re-enrichment;

[0022] k is the number of grids corresponding to the non-enriched regions after re-enrichment;

[0023] i is a subscript;

[0024] αi The value of the remaining oil enrichment state before the remaining oil in grid i is re-enriched.

[0025] The formula for calculating the potential index is as follows:

[0026]

[0027] in,

[0028] In the formula:

[0029] i and j are subscripts;

[0030] N i The number of remaining oil blocks corresponding to the i-th type of remaining oil after re-enrichment;

[0031] S ij For the area corresponding to the j-th oil-bearing block of the i-th remaining oil type after re-enrichment, m 2 ;

[0032] S ijmax m is the area corresponding to the largest oil-bearing block of the i-th type of remaining oil after re-enrichment. 2 ;

[0033] S i This refers to the j-th oil-bearing block of the i-th remaining oil type after further enrichment;

[0034] σ si The area variance of the i-th type of residual oil after re-enrichment is normalized and is dimensionless.

[0035] η i The weight is the utilization potential weight corresponding to the i-th type of residual oil after re-enrichment. For highly enriched residual oil, the weight is 2; for moderately enriched residual oil, the weight is 1; and for unenriched residual oil, the weight is 0.5.

[0036] Step (4) includes:

[0037] Based on the evaluation criteria for the quality of residual oil re-enrichment established in step (3), and based on the evaluation indicators for the quality of residual oil re-enrichment in step (2), the evaluation criteria for the quality of residual oil re-enrichment are determined.

[0038] Using the enrichment index as the horizontal axis and the utilization potential index as the vertical axis, when both the remaining oil enrichment index and the utilization potential index are greater than 1, it indicates that the quality of the remaining oil re-enrichment is relatively good, and it is defined as Class A remaining oil; when the remaining oil enrichment index is greater than 1 but the utilization potential index is less than 1, it is defined as Class B remaining oil; when the remaining oil enrichment index is less than 1 but the utilization potential index is greater than 1, it is defined as Class C remaining oil; when both the remaining oil enrichment index and the utilization potential index are less than 1, it indicates that the quality of the remaining oil re-enrichment is the worst, and it is defined as Class D remaining oil.

[0039] Step (5) includes:

[0040] Based on the evaluation criteria for the quality of the re-enriched residual oil established in step (4), and combined with the enrichment index and utilization potential index of the residual oil after re-enrichment obtained in step (3), the quality of the residual oil after re-enrichment is finally determined.

[0041] The method for evaluating the quality of residual oil re-enrichment in this application has the following beneficial effects:

[0042] The evaluation method for the quality of residual oil re-enrichment in this application includes: (1) obtaining the saturation distribution of residual oil before and after enrichment through physical simulation or numerical simulation of residual oil re-enrichment; (2) calculating the flow distribution curve; (3) calculating the distribution of enrichment state values ​​of residual oil before and after enrichment; (4) determining the evaluation index and evaluation standard for the quality of residual oil re-enrichment; and (5) evaluating the quality of residual oil re-enrichment. The evaluation method for the quality of residual oil re-enrichment in high water-cut reservoirs provided by this invention has the characteristics of simple operation, fast calculation, and clear objectives. It can intuitively classify the residual oil re-enriched in high water-cut reservoirs into different types, thereby providing a decision-making reference for tapping the potential of residual oil and has relatively practical engineering application value. Attached Figure Description

[0043] Figure 1 A flowchart for the quality evaluation method of residual oil re-enrichment;

[0044] Figure 2 A chart illustrating the evaluation criteria for the quality of residual oil re-enrichment;

[0045] Figure 3 This is a diagram showing the saturation distribution of residual oil before re-enrichment, obtained from a physical simulation.

[0046] Figure 4 This is a diagram showing the saturation distribution of the remaining oil after re-enrichment, obtained from a physical simulation.

[0047] Figure 5 This is a flow rate curve;

[0048] Figure 6 This represents the remaining oil enrichment state value before further enrichment of the remaining oil.

[0049] Figure 7 This represents the enrichment state value of the remaining oil after re-enrichment. Detailed Implementation

[0050] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0051] In the existing technology, due to the large number of factors affecting the quality of residual oil re-enrichment, and the fact that research on residual oil re-enrichment is currently in its early stages, an accurate evaluation method for the quality of residual oil re-enrichment has not yet been formed.

[0052] Example 1

[0053] The present application provides a method for evaluating the quality of residual oil re-enrichment, which includes: (1) obtaining the saturation distribution of residual oil before and after enrichment through physical simulation or numerical simulation of residual oil re-enrichment; (2) calculating the flow rate curve; (3) calculating the distribution of the enrichment state value of residual oil before and after enrichment; (4) determining the evaluation index and evaluation standard for the quality of residual oil re-enrichment; and (5) evaluating the quality of residual oil re-enrichment.

[0054] This application establishes evaluation indicators and standards for the quality of residual oil re-enrichment, and achieves accurate evaluation of the quality of residual oil re-enrichment.

[0055] Example 2

[0056] like Figure 1 As shown, Figure 1 A flowchart of a specific embodiment of the residual oil re-enrichment quality evaluation method of the present invention includes the following steps:

[0057] Step 1) Conduct detailed reservoir description of the target unit, and further combine the geological parameters of the target unit to carry out waterflooding physical simulation experiments to obtain the remaining oil saturation distribution before and after enrichment, such as... Figure 3 and Figure 4 As shown.

[0058] Step 2): Based on the target unit in Step 1), and combining the relative permeability curve of that unit, calculate the flow distribution curve for that region using the flow distribution equation (ignoring gravity and capillary force), as shown below. Figure 5As shown. According to the water content classification standard, the flow curve is divided into three regions. When the water content is 0-20%, it is considered low water content, and the remaining oil is considered to be highly enriched here. At this time, the oil saturation is 0.69-1, and α is assigned a value of 2. When the water content is 20%-90%, it is considered medium-high water content, and the remaining oil is considered to be moderately enriched here. At this time, the oil saturation is 0.51-0.69, and α is assigned a value of 1. When the water content is 90%-100%, it is considered very high water content, and the remaining oil is considered not enriched here. At this time, the oil saturation is 0-0.51, and α is assigned a value of 0.5.

[0059] In other embodiments, the flow rate curve is divided into three regions according to the water content grading standard. The saturation points corresponding to these three regions are the boundary points of the oil saturation grading. An enrichment state value α is defined to represent the enrichment state of the remaining oil in each region. That is, when the water content is between 0% and 20%, it is considered to be low water content, and the remaining oil is considered to be highly enriched at this point. At this time, the oil saturation is S1 to 1, and a value is assigned.

[0060] α is 2; when the water content is between 20% and 90%, it is considered medium to high water content, and the remaining oil is considered to be moderately enriched in this area. The oil saturation is S2 to S1, and α is assigned a value of 1; when the water content is between 90% and 100%, it is considered very high water content, and the remaining oil is considered not enriched in this area. The oil saturation is 0 to S2, and α is assigned a value of 1.

[0061] α is 0.5.

[0062] In step 3), based on the remaining oil saturation distribution before and after enrichment obtained in step 1), and according to the saturation points corresponding to the three regions of the flow distribution curve obtained in step 2) and the enrichment state values ​​corresponding to each region, the remaining oil enrichment state value distribution before and after enrichment is calculated respectively, as follows: Figure 6 and Figure 7 As shown in the figure. Further evaluation of the quality of remaining oil enrichment is based on the remaining oil enrichment degree index and the utilization potential index.

[0063] The enrichment index is calculated using the following formula:

[0064]

[0065] In the formula:

[0066] S1 i The area corresponding to the highly enriched region after re-enrichment is m. 2 ;

[0067] S2 i The area corresponding to the moderately enriched region after re-enrichment is m. 2 ;

[0068] S3 iThe area of ​​the non-enriched region after re-enrichment is m. 2 ;

[0069] m represents the number of grids corresponding to the highly enriched regions after re-enrichment;

[0070] n represents the number of grids corresponding to the moderately enriched region after re-enrichment;

[0071] k is the number of grids corresponding to the non-enriched regions after re-enrichment;

[0072] i is a subscript;

[0073] α i The value represents the remaining oil enrichment state of grid i before further enrichment.

[0074] The formula for calculating the potential index is as follows:

[0075]

[0076] in,

[0077] In the formula:

[0078] i and j are subscripts;

[0079] N i The number of remaining oil blocks corresponding to the i-th type of remaining oil after re-enrichment;

[0080] S ij For the area corresponding to the j-th oil-bearing block of the i-th remaining oil type after re-enrichment, m 2 ;

[0081] S ijmax m is the area corresponding to the largest oil-bearing block of the i-th type of remaining oil after re-enrichment. 2 ;

[0082] S i This refers to the j-th oil-bearing block of the i-th remaining oil type after further enrichment;

[0083] σ si The area variance of the i-th type of residual oil after re-enrichment is normalized and is dimensionless.

[0084] η i The weight is the utilization potential weight corresponding to the i-th type of residual oil after re-enrichment. For highly enriched residual oil, the weight is 2; for moderately enriched residual oil, the weight is 1; and for unenriched residual oil, the weight is 0.5.

[0085] Calculations show that the enrichment index and utilization potential index of the remaining oil after re-enrichment are 0.6842 and 1.1076, respectively.

[0086] Step 4): Based on the evaluation criteria for the quality of residual oil re-enrichment established in Step 3), and based on the evaluation indicators for the quality of residual oil re-enrichment in Step 2), determine the evaluation criteria for the quality of residual oil re-enrichment, such as... Figure 2 As shown in the figure, with the enrichment index on the horizontal axis and the utilization potential index on the vertical axis, when both the remaining oil enrichment index and the utilization potential index are greater than 1, it indicates that the quality of the remaining oil re-enrichment is relatively good, and it is defined as Class A remaining oil; when the remaining oil enrichment index is greater than 1 but the utilization potential index is less than 1, it is defined as Class B remaining oil; when the remaining oil enrichment index is less than 1 but the utilization potential index is greater than 1, it is defined as Class C remaining oil; when both the remaining oil enrichment index and the utilization potential index are less than 1, it indicates that the quality of the remaining oil re-enrichment is the worst, and it is defined as Class D remaining oil.

[0087] In step 5), based on the evaluation criteria for the quality of the re-enriched residual oil established in step 4), and combined with step 3), the enrichment degree index and utilization potential index of the re-enriched residual oil are obtained. Finally, the quality of the re-enriched residual oil is determined to be Class C residual oil.

[0088] The evaluation method for the quality of re-enrichment of residual oil in high water-cut reservoirs provided by this invention is characterized by simple operation, fast calculation and clear objectives. It can intuitively classify the re-enriched residual oil in high water-cut reservoirs into different types, thereby providing a decision-making reference for tapping the potential of residual oil and has practical engineering application value.

[0089] The improvements of this invention include: 1. Calculating the flow rate curve based on the residual oil saturation obtained from physical simulation or reservoir numerical simulation, combined with the relative permeability curve; 2. Calculating the distribution of residual oil enrichment state values ​​before and after enrichment; 3. Establishing evaluation indicators and standards for the quality of residual oil re-enrichment.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for evaluating the quality of residual oil re-enrichment, characterized in that, include: (1) The remaining oil saturation distribution before and after enrichment is obtained through physical simulation or numerical simulation of the remaining oil re-enrichment; including: carrying out fine reservoir description of the target unit, and carrying out water-drive oil physical simulation experiments in combination with the geological parameters of the target unit to obtain the remaining oil saturation distribution before and after enrichment. (2) Calculate the flow distribution curve; including: based on the target unit, combined with the relative permeability curve of the target unit, calculate the flow distribution curve of the region through the flow distribution equation; according to the water content classification standard, divide the flow distribution curve into 3 regions, and the saturation points corresponding to these 3 regions are the boundary points of the oil saturation classification, and define an enrichment state value. This indicates the enrichment state of the remaining oil in each region; (3) Calculate the distribution of the remaining oil enrichment state values ​​before and after enrichment; step (3) also includes: The quality of remaining oil enrichment is evaluated based on the remaining oil enrichment index and the utilization potential index. The enrichment index is calculated using the following formula: In the formula: The area corresponding to the highly enriched region after re-enrichment is m. 2 ; The area corresponding to the moderately enriched region after re-enrichment, in m 2 ; The area of ​​the non-enriched region after re-enrichment is m. 2 ; m The number of grid cells corresponding to the highly enriched regions after re-enrichment; n The number of grids corresponding to the moderately enriched region after re-enrichment; k The number of grid cells corresponding to the non-enriched regions after re-enrichment; i Subscript; For grid i The remaining oil enrichment state value before re-enrichment of the remaining oil; The formula for calculating the potential index is as follows: in, In the formula: i, j Subscript; For further enrichment i The number of remaining oil blocks corresponding to each type of remaining oil; For further enrichment i Remaining oil j The area corresponding to each oil-bearing block, m 2 ; For further enrichment i The area corresponding to the largest oil-bearing block in the remaining oil category, m 2 ; For further enrichment i Remaining oil j One oil-containing block; For further enrichment i The area variance of the remaining oil class is normalized and dimensionless. For further enrichment i The utilization potential weights for different types of residual oil are as follows: for highly enriched residual oil, the weight is 2; for moderately enriched residual oil, the weight is 1; and for non-enriched residual oil, the weight is 0.

5. (4) Determine the evaluation indicators and standards for the quality of residual oil re-enrichment; (5) Evaluate the quality of the remaining oil re-enrichment.

2. The method for evaluating the quality of residual oil re-enrichment according to claim 1, characterized in that, When the water content is between 0% and 20%, it is considered low water content, and the remaining oil is considered to be highly enriched at this point. The oil saturation at this time is S1 to 1, and a value is assigned accordingly. The value is 2; when the water content is between 20% and 90%, it is considered to be medium to high water content, and the remaining oil is considered to be moderately enriched at this point. At this time, the oil saturation is S2 to S2. 1， and assign values The value is 1; when the water content is between 90% and 100%, it is considered to be an extremely high water content, and the remaining oil is not enriched at this point. In this case, the oil saturation is 0 to S2, and a value is assigned. It is 0.

5.

3. The method for evaluating the quality of residual oil re-enrichment according to claim 2, characterized in that, Step (3) includes: Based on the remaining oil saturation distribution before and after enrichment, the distribution of remaining oil enrichment state values ​​before and after enrichment is calculated according to the saturation points corresponding to the three regions of the flow curve and the enrichment state values ​​corresponding to each region.

4. The method for evaluating the quality of residual oil re-enrichment according to claim 3, characterized in that, Step (4) includes: Using the enrichment index as the horizontal axis and the utilization potential index as the vertical axis, when both the remaining oil enrichment index and the utilization potential index are greater than 1, it indicates that the quality of the remaining oil re-enrichment is relatively good, and it is defined as Class A remaining oil. When the remaining oil enrichment index is greater than 1 but the utilization potential index is less than 1, it is defined as Class B remaining oil. When the remaining oil enrichment index is less than 1 but the utilization potential index is greater than 1, it is defined as Class C remaining oil. When both the remaining oil enrichment index and the utilization potential index are less than 1, it indicates that the quality of the remaining oil re-enrichment is the worst, and it is defined as Class D remaining oil.

5. The method for evaluating the quality of residual oil re-enrichment according to claim 4, characterized in that, Step (5) includes: Based on the evaluation criteria for the quality of the re-enriched residual oil established in step (4), and combined with the enrichment index and utilization potential index of the residual oil after re-enrichment obtained in step (3), the quality of the residual oil after re-enrichment is finally determined.

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