A method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs

Abstract

A method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs. It includes defining parameters; determining the formula for calculating the volume shift of the oil-water interface; determining the formula for solving the current oil-water interface depth; and obtaining multiple V values. n / V2 value; calculate each V n / V2 value and Q n The difference between / Q2 values ​​yields the current oil-water interface depth H. n The method for calculating the oil-water interface depth in developed edge-bottom water reservoirs provided by this invention has the following beneficial effects: it helps to gain a clearer understanding of the current reservoir characteristics, elevating the understanding from qualitative to quantitative calculation in practical work, guiding the quantitative identification of strongly water-flooded areas and remaining oil-rich areas in the reservoir, and serving as the basis for the next step of rational and efficient reservoir adjustment and development, guiding the deployment of development plans, and helping to further improve reservoir recovery. Since edge-bottom water reservoirs are commonly developed in oilfields worldwide, this method also has high potential for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of reservoir development technology, and specifically relates to a method for calculating the current oil-water interface depth of developed edge-bottom water reservoirs. Background Technology

[0002] A rim-bottom water reservoir refers to an oil reservoir where water bodies develop at the edge or bottom. Due to the significant density difference between oil and water, and through differentiation and adjustment, oil is concentrated in the higher parts of the reservoir, while the water body is located at the edge or bottom. The contact surface between the oil and water body is called the oil-water interface. If the oil-water interface is very large, much larger than the vertical cross-section of the oil layer, such a reservoir is a bottom water reservoir, and its oil layer is generally relatively thick. If the oil-water interface is relatively small, about the same as the vertical cross-section of the oil layer, such a reservoir is a rim water reservoir, and its oil layer is generally relatively thin and has a certain structural dip. However, there is no absolutely clear boundary between bottom water reservoirs and rim water reservoirs, so they are collectively referred to as rim-bottom water reservoirs. Rim-bottom water reservoirs are a common type of reservoir. During the development of this type of reservoir, as the degree of crude oil recovery gradually increases, the rim-bottom water pushes the oil-water interface upwards. In the area affected by the oil-water interface, the crude oil in the reservoir pores is displaced by the rim water, resulting in a strongly water-flooded state.

[0003] Studying the distribution patterns of remaining oil in developed edge-water reservoirs is crucial for improving reservoir recovery. As the recovery rate of edge-water reservoirs increases, the oil-water boundary gradually rises, and the affected reservoirs undergo edge water washing, resulting in a significant decrease in oil saturation, thus excluding them from potential areas for remaining oil accumulation. Therefore, quantitatively calculating the oil-water interface of current reservoirs can, on the one hand, exclude areas of strong water flooding below the current oil-water interface, ensuring the identification of areas rich in remaining oil and the rational deployment of new wells for potential development; on the other hand, it can guide the deployment of reservoir development adjustment plans, including well network deployment, coverage area assessment, and seepage field adjustment.

[0004] Currently, the determination of the oil-water interface mainly relies on calculation methods for the original oil-water interface of the reservoir. However, no quantitative calculation methods for the oil-water interface depth of developed edge-bottom water reservoirs have been found through research. As reservoirs are developed and utilized, the reservoir characteristics and oil-water interface depth at the current stage are becoming the focus of reservoir engineers' attention. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs.

[0006] To achieve the above objectives, the method for calculating the current oil-water interface depth of developed edge-bottom water reservoirs provided by this invention includes the following steps performed in sequence:

[0007] 1) Define parameters including the comprehensive adjustment time, oil-water interface depth, and oil-bearing area at each stage from reservoir development to the present.

[0008] 2) Based on the parameters in step 1), determine the calculation formula for the volume V2 of the oil-water interface shift during the time period from the time T1 of the first scheme to the time T2 of the second scheme.

[0009] 3) Based on the parameters in step 1), determine the time T from the implementation time T2 of the second plan to the present. n The volume V of the oil-water interface shifting upwards during the time period n The calculation formula;

[0010] 4) The time from the implementation of the second plan at the new well site T2 to the present time T n The volume V of the oil-water interface shifting upwards during the time period n The ratio of the volume V2 that shifted upward at the oil-water interface during the period from the time of the first new well implementation (T1) to the time of the second new well implementation (T2) is used as the current oil-water interface depth H. n Solve the formula;

[0011] 5) Read multiple sets of different contour depth values ​​D from the reservoir microstructure map and oil-bearing area distribution map. m and the oil-bearing area P above this depth value m The data, each pair of data is treated as an array, and the contour depth values ​​D in different arrays are... m and the oil-bearing area P above this depth value m The current oil-water interface depth H is respectively used as the target depth. n And the current oil-water interface depth H n The above oil-bearing area S n Substituting the current oil-water interface depth H into the above... n Solve the formula to obtain multiple V values. n / V2 value;

[0012] 6) Calculate each V n / V2 value and Q n The difference between / Q2 and the total oil production, where Q2 represents the cumulative oil production during the period from the time T1 when the first new well was implemented to the time T2 when the second new well was implemented, and T represents the total oil production during the period from the time T2 when the second new well was implemented to the present. n Cumulative oil production Q n Obtained from oil well production reports; then |V n / V2-Q n / Q2| Contour depth value D corresponding to the minimum absolute value m and the oil-bearing area P above this depth value m The desired current oil-water interface depth H n And the current oil-water interface depth Hn The above oil-bearing area S n The optimal solution can be used to obtain the current oil-water interface depth H. n .

[0013] In step 1), the method for defining parameters including the comprehensive adjustment time, oil-water interface depth, and oil-bearing area at each stage from reservoir development to the present is as follows:

[0014] Based on the chronological order of the reservoir's multiple comprehensive adjustments from discovery to later stages, the comprehensive adjustment times are defined as T1, T2, T3...T n Where T1 represents the time of the first well implementation under the new development plan after the reservoir was discovered, at which point the initial oil-water interface depth of the reservoir is H1, and the initial oil-bearing area above the initial oil-water interface depth H1 is S1; T2 represents the time of the second well implementation under the new development plan, at which point the oil-water interface depth of the reservoir is H2, and the oil-bearing area above the oil-water interface depth H2 is S2; the cumulative oil production during the period from the first well implementation time T1 to the second well implementation time T2 is Q2; T n This represents the current time, from the time T2 when the second plan was implemented to the current time T. n The cumulative oil production is Q n The depth of the oil-water interface in the reservoir is the current oil-water interface depth H. n Currently, the oil-water interface depth H n The above oil-bearing area is S n .

[0015] In step 2), the formula for calculating the volume V2 of the oil-water interface shift during the time period from the first well-opening time T1 to the second well-opening time T2 is as follows:

[0016] V2=(S1-S2)*(H1-H2); (1)

[0017] The original oil-water interface depth H1 and the original oil-bearing area S1 were obtained from the reservoir microstructure map and the oil-bearing area distribution map; the oil-water interface depth H2 was obtained from the interpretation results of the wells encountered in the second adjustment scheme; and the oil-bearing area S2 was obtained from the reservoir microstructure map and the oil-bearing area distribution map.

[0018] In step 3), the second scheme involves a new well implementation time T2 to the present time T. n The volume V of the oil-water interface shifting upwards during the time period n The calculation formula is:

[0019] V n =(S2-S n )*(H2-H n (2)

[0020] Among them, H n To find the current oil-water interface depth, the current oil-water interface depth H is... n The above oil-bearing area is S n .

[0021] In step 4), the current oil-water interface depth H n The solution formula is:

[0022] V n / V2 = [(S2-S n )*(H2-H n )] / [(S1-S2)*(H1-H2)] (3).

[0023] The method for calculating the current oil-water interface depth in developed edge-and-bottom water reservoirs provided by this invention has the following beneficial effects: it helps to gain a clearer understanding of the current reservoir characteristics, elevating the understanding from qualitative to quantitative calculation in practical work. This guides the quantitative identification of strongly water-flooded areas and remaining oil-rich areas in the reservoir, and serves as the basis for the rational and efficient adjustment and development of the reservoir in the next step, guiding the deployment of development plans and helping to further improve reservoir recovery. Since edge-and-bottom water reservoirs are commonly found in oilfields worldwide, this method also has high potential for widespread application. Attached Figure Description

[0024] Figure 1 The flowchart illustrates the calculation method for the current oil-water interface depth in developed edge-bottom water reservoirs provided by this invention.

[0025] Figure 2 This is a schematic diagram of the oil-water boundary in the edge-bottom water reservoir of this invention. Among them, (a) is a microstructure and oil-bearing area distribution diagram of the XX reservoir, and (b) is a schematic diagram of the cross section of reservoir A to B.

[0026] Figure 3 This is a diagram showing the microstructure and oil-bearing area distribution of the YY oil layer in an embodiment of the present invention.

[0027] Figure 4 This is a comprehensive interpretation diagram of well logging in an embodiment of the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, the method for calculating the current oil-water interface depth of developed edge-bottom water reservoirs provided by this invention includes the following steps performed in sequence:

[0030] 1) Define parameters including the comprehensive adjustment time, oil-water interface depth, and oil-bearing area at each stage from reservoir development to the present.

[0031] Oil reservoir development involves multiple stages of comprehensive adjustments to improve the injection-production well network, tap the potential of remaining oil-rich areas, and achieve rational and efficient reservoir development. Based on the chronological order of these comprehensive adjustments from reservoir discovery to later stages, the adjustment periods are defined as T1, T2, T3…T… n Where T1 represents the time when the reservoir was first discovered and put into development, and a new well was implemented. At this time, the initial oil-water interface depth of the reservoir was H1, and the initial oil-bearing area above the initial oil-water interface depth H1 was S1. After many years of development, as the cumulative oil production increases, the oil-water interface changes accordingly. T2 represents the time when the reservoir was second-time to implement a new well, and the initial oil-water interface depth was H2. At this time, the oil-water interface depth of the reservoir was H2, and the oil-bearing area above the oil-water interface depth H2 was S2. The cumulative oil production from the time of the first implementation of the new well T1 to the time of the second implementation of the new well T2 is Q2. Figure 2 As shown; T n This represents the current time, from the time T2 when the second plan was implemented to the current time T. n The cumulative oil production is Q n At this point, the depth of the oil-water interface in the reservoir is the desired current oil-water interface depth H. n Currently, the oil-water interface depth H n The above oil-bearing area is S n .

[0032] Having undergone two or more development adjustments, based on reservoir development data and drilled wells, the known parameters include: original oil-water interface depth H1, original oil-bearing area S1, oil-water interface depth H2, oil-bearing area S2, cumulative oil production Q2 from the time of the first well implementation (T1) to the time of the second well implementation (T2), and the time from the time of the second well implementation (T2) to the present (T). n Cumulative oil production Q n ;

[0033] 2) Based on the parameters in step 1), determine the calculation formula for the volume V2 of the oil-water interface shift during the time period from the first well implementation time T1 to the second well implementation time T2:

[0034] V2=(S1-S2)*(H1-H2); (1)

[0035] The original oil-water interface depth H1 and the original oil-bearing area S1 were obtained from the reservoir microstructure map and the oil-bearing area distribution map; the oil-water interface depth H2 was obtained from the interpretation results of the wells encountered in the second adjustment scheme; and the oil-bearing area S2 was obtained from the reservoir microstructure map and the oil-bearing area distribution map.

[0036] 3) Based on the parameters in step 1), determine the time T from the implementation time T2 of the second plan to the present.n The volume V of the oil-water interface shifting upwards during the time period n The calculation formula is as follows:

[0037] V n =(S2-S n )*(H2-H n (2)

[0038] Among them, H n To find the current oil-water interface depth, the current oil-water interface depth H is... n The above oil-bearing area is S n ;

[0039] 4) The time from the implementation of the second plan at the new well site T2 to the present time T n The volume V of the oil-water interface shifting upwards during the time period n The ratio of the volume V2 that shifted upward at the oil-water interface during the period from the time of the first new well implementation (T1) to the time of the second new well implementation (T2) is used as the current oil-water interface depth H. n Solution formula:

[0040] V n / V2 = [(S2-S n )*(H2-H n )] / [(S1-S2)*(H1-H2)] (3)

[0041] 5) Read multiple sets of different contour depth values ​​D from the reservoir microstructure map and oil-bearing area distribution map. m and the oil-bearing area P above this depth value m The data, each pair of data is treated as an array, as shown in Table 1. The contour depth values ​​D in different arrays are... m and the oil-bearing area P above this depth value m The current oil-water interface depth H is respectively used as the target depth. n And the current oil-water interface depth H n The above oil-bearing area S n Substituting into the solution formula shown in equation (3), multiple V values ​​are obtained. n / V2 value; the interval of contour depth values ​​is determined according to the required accuracy. Generally, the interval of contour depth values ​​is less than 2 meters to meet the practical applications of reservoir development and analysis.

[0042] 6) Calculate each V n / V2 value and Q n The difference between / Q2 and the total oil production, where Q2 represents the cumulative oil production during the period from the time T1 when the first new well was implemented to the time T2 when the second new well was implemented, and T represents the total oil production during the period from the time T2 when the second new well was implemented to the present. n Cumulative oil production Q nObtained from oil well production reports; then |V n / V2-Q n / Q2| Contour depth value D corresponding to the minimum absolute value m and the oil-bearing area P above this depth value m The desired current oil-water interface depth H n And the current oil-water interface depth H n The above oil-bearing area S n The optimal solution can be used to obtain the current oil-water interface depth H. n .

[0043] Table 1. Statistics of different contour depths and their corresponding oil-bearing areas

[0044]

[0045] like Figure 3 As shown, the method of the present invention will be described in detail below using the oil reservoir on the south side of fault No. 50 in the xx fault block of a certain oil field as an example:

[0046] (1) Characteristics of reservoirs in their initial development;

[0047] T1: June 2001; original oil-water interface depth H1: 1804 meters; original oil-bearing area S1: 0.24 square kilometers.

[0048] (2) Secondary adjustment of reservoir characteristics;

[0049] T2: June 2007; oil-water interface depth H2: 1796 meters; oil-bearing area S2: 0.173 square kilometers; cumulative oil production Q2 during the T1-T2 period: 102,000 tons.

[0050] Note: Well X15 was the second adjustment well, completed in June 2007. The current oil-water interface depth H2, read from the comprehensive electrical logging interpretation, is 1796 meters. Figure 4 As shown. The oil-bearing area S2, which is the oil-bearing area above the 1796m contour line depth, is read as 0.173 square kilometers on the microstructure and oil-bearing area map. The cumulative oil production Q2 during the T1-T2 period, i.e., the cumulative oil production of the southern reservoir from June 2001 to June 2007, is 102,000 tons according to the well production report.

[0051] (3) Table 2 shows the statistical table of different contour depth values ​​and their corresponding oil-bearing areas;

[0052] Note: The oil reservoir is located south of fault No. 50 in the xx fault block. The contour depth values ​​are spaced 2 meters apart. The contour depth values ​​in Table 2 are from... Figure 3 Read the contour line depth value; the oil-bearing area above this contour line depth value is from... Figure 3 Measurement and reading.

[0053] (4)Q n The cumulative oil production from July 2007 to the present is 36,600 tons, according to the well production report.

[0054] (5) Based on the current oil-water interface depth H n Solution formula:

[0055] V n / V2=[(S2-S n )*(H2-H n )] / [(S1-S2)*(H1-H2)]

[0056] Sequentially assign (D1, P1) to (D m P m The arrays represent the current oil-water interface depth H. n And the current oil-water interface depth H n The above oil-bearing area S n Substituting into the above solution formula, we obtain multiple V values. n / V2 value;

[0057] (6) Calculate each V n / V2 value and Q n The difference between / Q2 values ​​is calculated, and the results are shown in Table 3. Then, |V n / V2-Q n / Q2| Contour depth value D corresponding to the minimum absolute value m and the oil-bearing area P above this depth value m The desired current oil-water interface depth H n And the current oil-water interface depth H n The above oil-bearing area is S n The optimal solution can be used to obtain the current oil-water interface depth H. n .

[0058] In this embodiment, Q n / Q2=3.66 / 10.2=0.36;

[0059] |V n / V2-Q n The minimum absolute value of / Q2 is 0.11, and the corresponding contour depth of 1792 meters is the current oil-water interface depth H. n .

[0060] Table 2. Statistics of different contour depths and their corresponding oil-bearing areas

[0061]

[0062]

[0063] Table 3. Statistical Table of Calculation Results

[0064]

[0065] The desired depth H of the oil-water interface is... n The depth is 1792 meters, which is 12 meters higher than the original oil-water interface H1 of 1804 meters. Therefore, within the oil-bearing area above the current oil-water interface depth, the remaining oil-rich area can be identified, and 5 new wells can be deployed for potential tapping.

Claims

1. A method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs, characterized in that: The calculation method includes the following steps performed in sequence: 1) Define parameters including the comprehensive adjustment time, oil-water interface depth, and oil-bearing area at each stage from reservoir development to the present. 2) Based on the parameters in step 1), determine the calculation formula for the volume V2 of the oil-water interface shift during the time period from the time T1 of the first scheme to the time T2 of the second scheme. 3) Based on the parameters in step 1), determine the time T from the implementation time T2 of the second plan to the present. n The volume V of the oil-water interface shifting upwards during the time period n The calculation formula; 4) The time from the implementation of the second plan at the new well site T2 to the present time T n The volume V of the oil-water interface shifting upwards during the time period n The ratio of the volume V2 that shifted upward at the oil-water interface during the period from the time of the first new well implementation (T1) to the time of the second new well implementation (T2) is used as the current oil-water interface depth H. n Solve the formula; 5) Read multiple sets of different contour depth values ​​D from the reservoir microstructure map and oil-bearing area distribution map. m and the oil-bearing area P above this depth value m The data, each pair of data is treated as an array, and the contour depth values ​​D in different arrays are... m and the oil-bearing area P above this depth value m The current oil-water interface depth H is respectively used as the target depth. n And the current oil-water interface depth H n The above oil-bearing area S n Substituting the current oil-water interface depth H into the above... n Solve the formula to obtain multiple V values. n / V2 value; 6) Calculate each V n / V2 value and Q n The difference between / Q2 and the total oil production, where Q2 represents the cumulative oil production during the period from the time T1 when the first new well was implemented to the time T2 when the second new well was implemented, and T represents the total oil production during the period from the time T2 when the second new well was implemented to the present. n Cumulative oil production Q n Obtained from oil well production reports; then |V n / V2-Q n / Q2| Contour depth value D corresponding to the minimum absolute value m and the oil-bearing area P above this depth value m The desired current oil-water interface depth H n And the current oil-water interface depth H n The above oil-bearing area S n The optimal solution can be used to obtain the current oil-water interface depth H. n .

2. The method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs according to claim 1, characterized in that: In step 1), the method for defining parameters including the comprehensive adjustment time, oil-water interface depth, and oil-bearing area at each stage from reservoir development to the present is as follows: Based on the chronological order of the reservoir's multiple comprehensive adjustments from discovery to later stages, the comprehensive adjustment times are defined as T1, T2, T3...T n Where T1 represents the time of the first well implementation for the reservoir discovery and development plan, at which point the initial oil-water interface depth is H1, and the initial oil-bearing area above the initial oil-water interface depth H1 is S1; T2 represents the time of the second well implementation for the reservoir, at which point the oil-water interface depth is H2, and the oil-bearing area above the oil-water interface depth H2 is S2; the cumulative oil production from the time of the first well implementation T1 to the time of the second well implementation T2 is Q2; T n This represents the current time, from the time T2 when the second plan was implemented to the current time T. n The cumulative oil production is Q n The depth of the oil-water interface in the reservoir is the current oil-water interface depth H. n Currently, the oil-water interface depth H n The above oil-bearing area is S n .

3. The method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs according to claim 2, characterized in that: In step 2), the formula for calculating the volume V2 of the oil-water interface shift during the time period from the first well-opening time T1 to the second well-opening time T2 is as follows: V2=(S1-S2)*(H1-H2); (1) The original oil-water interface depth H1 and the original oil-bearing area S1 were obtained from the reservoir microstructure map and the oil-bearing area distribution map; the oil-water interface depth H2 was obtained from the interpretation results of the wells encountered in the second adjustment scheme; and the oil-bearing area S2 was obtained from the reservoir microstructure map and the oil-bearing area distribution map.

4. The method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs according to claim 2, characterized in that: In step 3), the second scheme involves a new well implementation time T2 to the present time T. n The volume V of the oil-water interface shifting upwards during the time period n The calculation formula is: V n =(S2-S n )*(H2-H n ) (2) Among them, H n To find the current oil-water interface depth, the current oil-water interface depth H is... n The above oil-bearing area is S n .

5. The method for calculating the current oil-water interface depth in developed edge-bottom water reservoirs according to claim 2, characterized in that: In step 4), the current oil-water interface depth H n The solution formula is: V n / V2 =[(S2-S n (H2-H) n (3)

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