Polymer flooding control degree comprehensive factor calculation method

Abstract

The invention relates to the technical field of oil field tertiary oil recovery, in particular to a polymer flooding control degree comprehensive factor calculation method. The method comprises the following steps: statically calculating a polymer flooding control degree value by defining the percentage of the oil layer pore volume which can be swept by a polymer solution in the total pore volume of the oil layer under a certain polymer relative molecular mass condition; the polymer flooding control degree value is calculated according to the ratio of the product of the area affected by the polymer and the flattening thickness affected by the polymer to the product of the total area of the regional flattening thickness region and the regional flattening thickness; giving a single well weight value and a polymer flooding single well weight value; calculating the total area of the flattening thickness area and the area affected by the polymer; analyzing factors influencing the polymer flooding control degree; and according to the polymer flooding control degree value, the corresponding polymer flooding control level is specifically judged. The calculation method is simple and clear in process, the calculation precision and speed are further improved, and then accurate design basic data are provided for polymer flooding development scheme compilation.

Description

Technical Field

[0001] This invention relates to the field of tertiary oil recovery technology, and in particular to a method for calculating the comprehensive factors controlling polymer flooding. Background Technology

[0002] Polymer flooding control level refers to the percentage of oil reservoir pore volume that can be affected by a polymer solution of a certain molecular weight injected into the formation, relative to the total pore volume of the oil reservoir. Industrial polymer flooding practice shows that blocks with a higher degree of polymer flooding control have better polymer flooding effects. The two main factors affecting the degree of polymer flooding control are: first, the degree of control of the well network on polymer flooding; and second, the connectivity between injection wells and production wells in the polymer flooding process. Due to the influence of well network spacing and geological conditions, the degree of polymer flooding control varies in polymer injection blocks, resulting in differences in polymer flooding effects. Therefore, appropriately reducing the well spacing and improving the oil reservoir connectivity is a way to improve the degree of polymer flooding control. With the progress of laboratory tests and field monitoring during oilfield development, and the deepening of multidisciplinary reservoir research such as fine reservoir description, water injection development, polymer flooding development, and combined flooding development, the calculation accuracy of polymer flooding control level has gradually improved. The degree of polymer flooding control plays a crucial role in the design of polymer flooding layer combination, well spacing, and injection parameters. Its accuracy directly affects the development plan and thus the development effect of polymer flooding. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] This invention provides a comprehensive calculation method for polymer flooding control degree, which addresses the problem in the prior art that the polymer flooding control degree plays a crucial role in the design of polymer flooding layer combination, well spacing, and injection parameters, and its accuracy directly affects the development plan and thus the development effect of polymer flooding.

[0005] (II) Technical Solution

[0006] To address the above problems, this invention provides a method for calculating the comprehensive factors of polymer flooding control, comprising the following steps:

[0007] Step S1: Define the polymer flooding control degree value by statistically calculating the percentage of the oil layer pore volume that the polymer solution can reach to the total pore volume of the oil layer under certain polymer relative molecular mass conditions.

[0008] Step S2: The polymer drive control degree value is further calculated by using the product of the polymer swept area and the polymer swept thickness and the ratio of the product of the total area of ​​the region with the region with the thickness of the region with the thickness of the region.

[0009] Step S3: Using the calculation method in step S2, assign weight values ​​for single wells and weight values ​​for polymer flooding single wells;

[0010] Step S4: Calculate the total area of ​​the flattened thickness region and the area affected by the polymer.

[0011] Step S5: Further analyze the factors affecting the degree of polymer flooding control;

[0012] Step S6: Based on the impact of polymer flooding control degree on polymer flooding effect, reduce well spacing, improve reservoir connectivity, and enhance polymer flooding control degree.

[0013] Step S7: Determine the specific level of polymer drive control based on the polymer drive control degree value obtained above.

[0014] Preferably, the calculation formula for calculating the polymer flooding control degree value in step S2 includes:

[0015]

[0016] Where, η 聚 - Degree of control over polymer drive; ν 聚 -Polymer-saturated void volume, m 3 ;

[0017] ν 总 -Total void volume, m 3 S 聚 - The area swept by the polymer; S 总 - Total area of ​​the region;

[0018] h 聚碾平 - The thickness of the polymer-waved flattening; h 总碾平 - Area flattening thickness;

[0019] in:

[0020]

[0021] h 有效i - The effective thickness to which a single-well polymer solution can penetrate;

[0022] h 权i -Single well weight;

[0023] h 聚权i -Polymer flooding single well weight.

[0024] Preferably, the single-well weight coefficient given in step S3 is specifically: listing the total effective thickness encountered by each well, and giving the single-well weight coefficients of the edge wells, corner wells and center wells in the given area.

[0025] Preferably, the specific method for assigning the weight value of a polymer flooding well in step S3 is as follows: taking each well as the center, determine the control area of ​​the wells connected between injection and production wells, and deduct the area that cannot be connected by polymer flooding by reducing the weight coefficient accordingly, and assign a weight coefficient to each well for polymer flooding development.

[0026] Preferably, step S4 specifically includes:

[0027] The effectiveness of the oil well is determined based on the number of connectivity directions. The total area of ​​the study region is reduced by the area where polymer flooding cannot connect, and S is used as the unit of measurement. 单位面积 Multiples of .

[0028] Preferably, step S5 specifically includes: due to different types of obstruction between the injection well and the production well, the polymer flooding process between the injection and production wells is not connected, thus affecting the degree of polymer flooding control. Specifically, these obstructions can be classified into four types:

[0029] (i) Both injection and production wells are located within the dominant facies zone, which is blocked by sedimentary facies pinch-out and facies zones with poor physical properties;

[0030] (ii) Both injection and production wells are located in areas with high permeability, and are blocked by the permeability deterioration zone inside the connected phase.

[0031] (iii) Both injection and production wells are dominated by sheet-like sand, with vertical discontinuity of inter-river sand bodies providing obstruction;

[0032] (iv) Both injection and production wells are located in the sedimentary facies dominance area, with connecting facies faults blocking the flow.

[0033] Preferably, the specific criteria for determining the level in step S7 include:

[0034] (1) A polymer flooding control level greater than 85% is rated as good;

[0035] (2) The polymer flooding control level is greater than 80% and less than or equal to 85%, which is rated as good;

[0036] (3) If the polymer flooding control level is between 75% and 80%, the rating is medium;

[0037] (4) If the polymer flooding control level is greater than 70% and less than or equal to 75%, the rating is poor;

[0038] (5) If the degree of polymer flooding control is less than 70%, the rating is poor.

[0039] (III) Beneficial Effects

[0040] This invention provides a method for calculating the comprehensive factors of polymer flooding control, which has the following advantages:

[0041] (1) The method of calculating the degree of control of polymer flooding by volume method not only considers the thickness of oil layer connectivity between injection and production wells, but also the degree of perfection of injection and production relationship on the plane, that is, the connectivity direction (degree) on the oil layer plane. The effectiveness of the production well is determined according to the number of connectivity directions.

[0042] (2) The concept of phase is added to the plane, and the thickness corresponding to the permeability controlled by polymer flooding is screened. The medium and low permeability layer areas that polymer flooding cannot reach are fully considered. This method can better reflect the influence of oil reservoir geological conditions on polymer flooding effect than the traditional water flooding control method.

[0043] (3) This invention eliminates the need to calculate the polymer flooding control level of each well group within a block. Using each well as the center, a weighting coefficient is applied for the first time; only the weighting coefficient and effective thickness of a single well are needed to calculate the polymer flooding control level of the entire block. This calculation method is simple and clear, further improving calculation accuracy and speed, thus providing accurate design basis data for the preparation of polymer flooding development plans. Attached Figure Description

[0044] Figure 1 This is a flowchart of the comprehensive factor calculation method for polymer flooding control degree of the present invention;

[0045] Figure 2 This is a schematic diagram showing the values ​​of the total flattening thickness weighting coefficient in an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram showing the values ​​of the polymer-driven flattening thickness weighting coefficient in an embodiment of the present invention;

[0047] Figure 4 The influence of the degree of polymer flooding control on the polymer flooding effect in this embodiment of the invention is shown (vk = 0.62). Detailed Implementation

[0048] The following detailed description of a method for identifying the lithology of sandstone and conglomerate strata according to the present invention is provided to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention. It should be noted that the descriptions of the specific embodiments are exemplary and do not imply a limitation on the scope of protection of the present invention. The scope of the present invention is defined by the claims.

[0049] like Figures 1-4 As shown, this invention discloses a method for calculating the degree of polymer flooding control, the specific steps of which are as follows:

[0050] Step S1: Define the polymer flooding control degree value by statistically calculating the percentage of the oil layer pore volume that the polymer solution can reach to the total pore volume of the oil layer under certain polymer relative molecular mass conditions.

[0051] In this step, the degree of polymer flooding control should consider not only the connectivity direction (degree) in the oil reservoir plane, but also the pore volume that polymer molecules can enter. That is, when calculating the degree of polymer flooding control, the percentage of the oil reservoir pore volume that the polymer solution can reach to the total pore volume of the oil reservoir is used as the statistical method under a certain polymer relative molecular mass.

[0052] Step S2: The polymer drive control degree value is further calculated by using the product of the polymer swept area and the polymer swept thickness and the ratio of the product of the total area of ​​the region with the region with the thickness of the region with the thickness of the region.

[0053] In this step, the formula for calculating the degree of polymer flooding control is derived.

[0054]

[0055] η 聚 —Degree of polymer drive control, ν 聚 —Porosity of polymer wave, m 3 ;ν 总 —Total void volume, m 3 S 聚 —The area swept by the polymer, S 总 —The total area of ​​the region. h 聚碾平 —The thickness of the polymer-bearing layer, h 总碾平 —Thickness of the flattened area. Wherein:

[0056]

[0057] h 有效i —The effective thickness that a single-well polymer solution can penetrate, h 权i —Single well weight, h 聚权i —Polymer flooding single well weight.

[0058] Step S3: Using the calculation method in step S2, give the weight values ​​for single wells and the weight values ​​for polymer flooding single wells.

[0059] See Figure 2 The single-well weight value (h) 权i ): Determine the corner wells, edge wells, and center wells of the polymer flooding block. The weighting coefficients are given as follows: corner wells 0.25, edge wells 0.5, and center wells 1.

[0060] Polymer flooding single well weight value (h) 聚权i ): Taking each well as the center, determine the control area of ​​the wells connected between injection and production wells, and reduce the area that cannot be connected by polymer flooding by reducing the weight coefficient accordingly. Give the weight coefficient of each well for polymer flooding development.

[0061] Step S4: Calculate the total area of ​​the flattened thickness region and the area affected by the polymer.

[0062] See Figure 3 The effectiveness of the oil well is determined based on the number of connectivity directions. The total area of ​​the study region is reduced by the area that cannot be connected by polymer flooding. This is expressed in terms of the number of S-unit areas.

[0063] Step S5: Further analyze the factors affecting the degree of polymer flooding control.

[0064] In this step, different types of obstruction exist between the injection well and the production well, causing the polymer flooding process between the injection and production wells to be disconnected, thus affecting the degree of polymer flooding control. Specifically, these obstructions can be classified into four types:

[0065] (i) Both injection and production wells are located within the dominant facies zone, which is blocked by sedimentary facies pinch-out and facies zones with poor physical properties;

[0066] (ii) Both injection and production wells are located in areas with high permeability, and are blocked by the permeability deterioration zone inside the connected phase.

[0067] (iii) Both injection and production wells are dominated by sheet-like sand, with vertical discontinuity of inter-river sand bodies providing obstruction;

[0068] (iv) Both injection and production wells are located in the sedimentary facies dominance area, with connecting facies faults blocking the flow.

[0069] Step S6: Based on the impact of polymer flooding control degree on polymer flooding effect, reduce well spacing, improve reservoir connectivity, and enhance polymer flooding control degree.

[0070] For details, see Figure 4 Due to the influence of well spacing and geological conditions, the degree of polymer flooding control varies in polymer injection blocks. A lower degree of polymer flooding control results in a lower increase in oil recovery. Appropriately reducing well spacing and improving reservoir connectivity are important ways to enhance polymer flooding control effectiveness.

[0071] Step S7: Determine the specific level of polymer drive control based on the polymer drive control degree value obtained above.

[0072] The degree to which the well network controls the reservoir via polymer flooding directly affects development indicators such as oil production rate, water cut increase rate, reserve utilization, and polymer flooding recovery rate. The evaluation criteria for the degree of polymer flooding control in my country are as follows.

[0073]

[0074] To illustrate the above method more clearly, the following example from a domestic oilfield will be used for further explanation.

[0075] Example 1:

[0076] This study focuses on the Sa, Pu, and Gao oil layers in the northern part of the Daqing Changyuan Oilfield, and investigates a method for calculating the degree of polymer flooding control using the aforementioned method described in this invention. (See also...) Figure 1 The specific steps are as follows:

[0077] (1) Polymer flooding control degree refers to the percentage of oil layer pore volume that the polymer solution can influence to the total pore volume of the oil layer under certain polymer relative molecular mass conditions. The volumetric method for calculating polymer flooding control degree not only considers the connectivity direction (degree) on the oil layer plane, but also the size of the pore volume that polymer molecules can enter.

[0078] Derivation of the formula for the degree of control of the polymer drive

[0079]

[0080] η 聚 —Degree of polymer drive control, ν 聚 —Porosity of polymer wave, m 3 ν total void volume, m 3 S 聚 —The area swept by the polymer, S 总 —The total area of ​​the region. h 聚碾平 —The thickness of the polymer-bearing layer, h 总碾平 —Thickness of the flattened area. Wherein:

[0081]

[0082] h 有效i —The effective thickness that a single-well polymer can penetrate, h 权i —Single well weight, h 聚权i —Polymer flooding single well weight.

[0083] (2) Figure 2 The study block uses a five-point area well network, with the single well weight set to (h). 权i Wells 1, 4, 9, and 12 are corner wells with a weighting factor of 0.25; wells 2, 3, 5, 8, 10, and 11 are lateral wells with a weighting factor of 0.5; wells 6 and 7 are center wells with a weighting factor of 1. See also... Figure 2 .

[0084] Polymer flooding single well weight value (h) 聚权iCentered on each well, the controlled area of ​​interconnected injection and production wells is determined. Areas not connected by polymer flooding are deducted, and the thickness corresponding to the permeability controlled by polymer flooding is screened. A weight coefficient is assigned to each well for polymer flooding development. Wells 1, 2, 5, 6, and 9 have a weight coefficient of 0. Well 6 has such a low permeability that the polymer solution cannot reach the oil (according to the block's laboratory experiments, the critical permeability value KL = 0.200 μm²). Corner well 9 is located in a triangular non-connected area, so its weight coefficient is 0. Side wells 3, 8, and 11 have a weight coefficient of 0.5, and corner wells 4 and 12 have a weight coefficient of 0.25. The controlled area of ​​the central well 7, after deducting the non-connected area by polymer flooding, has a weight coefficient of 0.75. (Continue to see...) Figure 3 .

[0085] (3) See Figure 2 The sum of the controlled areas of a single well is the total area of ​​the region, denoted by S unit area. The total area of ​​the study region S is 24S unit area. Taking each well as the center, the controlled area of ​​the wells connected between injection and production wells is determined. The area that cannot be connected by polymer flooding is deducted, and the area of ​​the study region S of polymer flooding is 12S unit area.

[0086] (4) Formulas derived based on the degree of polymer flooding control. List the effective thickness and weighting coefficients required for polymer penetration in a single well. (Refer to...) Figure 2 The effective thicknesses that a single well can penetrate within the region are as follows:

[0087] h 有效1 =0m,h 有效2 =2.2m, h 有效3 =2.8m, h 有效4 =1.5m, h 有效5 =0m,h 有

[0088] 效6 =0.8m, h 有效7 =2.0m, h 有效8 =3.1m, h 有效9 =1.2m, h 有效10 =2.5m, h 有效11 =3.0m, h 有效12 =3.9m.

[0089]

[0090]

[0091] V 总 =S 总 xh 总碾平 =24S 单位面积 x1.875=45S 单位面积

[0092]

[0093]

[0094] V 总 =S 聚 xh 聚碾平 =12S 单位面积 x2.629=31.548S 单位面积

[0095]

[0096] η 聚 =70.11% is the degree of polymer drive control in the study block calculated using this invention.

[0097] (5) Different types of obstruction exist between injection wells and production wells, causing the polymer flooding process between injection and production wells to be disconnected, thus affecting the degree of polymer flooding control. The factors affecting the degree of polymer flooding control can be classified into four types of obstruction:

[0098] (i) Sedimentary facies pinch-out and poor physical property facies zone blocking; both injection and production wells are located inside the dominant facies zone. Due to the presence of sedimentary facies with poor physical properties between injection and production wells, such as external and some non-main sandstone, due to the presence of road wells, seismic attributes or geological predictions, the polymerization and flooding process between injection and production wells is not connected.

[0099] (ii) The permeability variation zone within the connected phase is blocked; both injection and production wells are located in areas with high permeability, and there are areas with poor permeability between injection and production wells due to road crossings, seismic attributes, or geological predictions, resulting in the lack of connection between injection and production wells in the polymer flooding process.

[0100] (iii) Vertical discontinuity of interfluvial sand bodies: Both injection and production wells are dominated by sheet-like sands, with no differential facies zones between them. However, sedimentary facies profiles show that the sand bodies in the injection and production wells do not correspond, and the actual sand bodies are not connected, resulting in a lack of connectivity in the aggregation and flooding process between injection and production wells.

[0101] (iv) Interfacial faults block the flow between the injection and production wells. Both the injection and production wells are located in the sedimentary facies-dominant region. Due to the presence of faults between the injection and production wells, the flow process between them is not interconnected.

[0102] (6) Industrial polymer flooding practices show that blocks with a higher degree of polymer flooding control have better polymer flooding effects. Due to the influence of well pattern, well spacing, and geological conditions, the degree of polymer flooding control varies among polymer injection blocks, resulting in differences in polymer flooding effects. Therefore, appropriately reducing well spacing, improving reservoir connectivity, and increasing the degree of polymer flooding control are important ways to improve polymer flooding effects.

[0103] (7) The degree of polymer flooding control of the oil reservoir by the well network directly affects the quality of development indicators such as oil production rate, water cut increase rate, reserve utilization rate, and polymer flooding recovery rate. The evaluation criteria for the degree of polymer flooding control in my country are: greater than 85% is good, between 80% and 85% is relatively good, between 75% and 80% is moderate, between 70% and 75% is relatively poor, and less than 70% is poor.

[0104] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A method for calculating the comprehensive factors of polymer flooding control, characterized in that, The steps include the following: Step S1: Define the polymer flooding control degree value by statistically calculating the percentage of the oil layer pore volume that the polymer solution can reach to the total pore volume of the oil layer under certain polymer relative molecular mass conditions. Step S2: Calculate the polymer drive control degree value by using the product of the polymer swept area and the polymer swept thickness and the ratio of the product of the total area of ​​the region with the region with the thickness of the region with the thickness of the region. Step S3: Using the calculation method in step S2, assign weight values ​​for single wells and weight values ​​for polymer flooding single wells; Step S4: Calculate the total area of ​​the flattened thickness region and the area affected by the polymer. Step S5: Further analyze the factors affecting the degree of polymer flooding control; Step S6: Based on the impact of polymer flooding control degree on polymer flooding effect, reduce well spacing, improve reservoir connectivity, and enhance polymer flooding control degree. Step S7: Determine the specific level of polymer drive control based on the polymer drive control degree value obtained above.

2. The method for calculating the comprehensive factors of polymer flooding control as described in claim 1, characterized in that, The calculation formula for calculating the polymer flooding control degree value in step S2 includes: Where, η 聚 - Degree of control over polymer drive; ν 聚 -Polymer-saturated void volume, m 3 ; ν 总 -Total void volume, m 3 S 聚 - The area swept by the polymer; S 总 - Total area of ​​the region; h 聚碾平 - The thickness of the polymer-waved flattening; h 总碾平 - Area flattening thickness; in: h 有效i - The effective thickness to which a single-well polymer solution can penetrate; h 权i -Single well weight; h 聚权i -Polymer flooding single well weight.

3. The method for calculating the comprehensive factors of polymer flooding control as described in claim 2, characterized in that, The specific steps for giving the single-well weight coefficient in step S3 are as follows: list the total effective thickness encountered by each well, and give the single-well weight coefficients for edge wells, corner wells and center wells within the given area.

4. The method for calculating the comprehensive factors of polymer flooding control degree as described in claim 2, characterized in that, The specific steps for determining the weight of a single polymer flooding well in step S3 are as follows: taking each well as the center, determine the control area of ​​the wells connected between injection and production wells, reduce the weight coefficient accordingly, deduct the area that cannot be connected by polymer flooding, and give a weight coefficient for each well in polymer flooding development.

5. The method for calculating the comprehensive factors of polymer flooding control degree as described in claim 2, characterized in that, Step S4 specifically includes: The effectiveness of the oil well is determined based on the number of connectivity directions. The total area of ​​the study region is reduced by the area where polymer flooding cannot connect, and S is used as the unit of measurement. 单位面积 Multiples of .

6. The method for calculating the comprehensive factors of polymer flooding control degree as described in claim 1, characterized in that, Step S5 specifically includes: Due to different types of obstruction between injection wells and production wells, the polymer flooding process between injection and production wells is not connected, thus affecting the degree of polymer flooding control. These obstructions can be categorized into four types: (i) Both injection and production wells are located within the dominant facies zone, which is blocked by sedimentary facies pinch-out and facies zones with poor physical properties; (ii) Both injection and production wells are located in areas with high permeability, and are blocked by the permeability deterioration zone inside the connected phase. (iii) Both injection and production wells are dominated by sheet-like sand, with vertical discontinuity of inter-river sand bodies providing obstruction; (iv) Both injection and production wells are located in the sedimentary facies dominance area, with connecting facies faults blocking the flow.

7. The method for calculating the comprehensive factors of polymer flooding control degree as described in claim 1, characterized in that, The specific criteria for determining the level in step S7 include: (1) A polymer flooding control level greater than 85% is rated as good; (2) The polymer flooding control level is greater than 80% and less than or equal to 85%, which is rated as good; (3) If the polymer flooding control level is between 75% and 80%, the rating is medium; (4) If the polymer flooding control level is greater than 70% and less than or equal to 75%, the rating is poor; (5) If the degree of polymer flooding control is less than 70%, the rating is poor.

Images