Cross-well flow field optimization method

Abstract

The invention relates to the technical field of oilfield development injection-production flow field optimization and hydrodynamic recovery efficiency improvement, and provides an inter-well flow field optimization method. The method includes: determining an oil well corresponding to a central well by taking a water injection well as a center; calculating the inter-well sweep area; calculating inter-well sweep area parameters; calculating seepage resistance between injection and production wells; the relation between the inter-well injection time and the plugging adjusting depth is established; establishing a relation between seepage resistance and plugging time; the optimal plugging distance under the maximum oil production constraint is determined; the method has very practical engineering theory application value for improving the recovery efficiency by optimizing the hydrodynamic flow field, and particularly for improving the recovery efficiency by optimizing the flow field of an offshore oilfield solidified well pattern and expanding the water injection wave.

Description

Technical Field

[0001] This invention relates to the field of oilfield development injection-production flow field optimization and hydrodynamic enhanced oil recovery technology, and provides a method for optimizing the inter-well flow field. Background Technology

[0002] Currently, most oilfields in my country have entered the medium-to-high water-cut stage. To achieve high and stable production, timely flow field optimization is crucial for stabilizing oil production and controlling water levels, ensuring the successful completion of production targets. Unlike onshore oilfields, offshore oilfields are affected by factors such as platform size and drilling costs. Large-scale well densification and frequent perforation and layer modification cannot meet the economic and technical adjustment requirements of offshore oilfields. Therefore, optimizing and adjusting the hydrodynamic flow field has long been a core technology for ensuring high and stable production in offshore oilfields.

[0003] To adapt to the requirements of offshore oilfield development and adjustment, and considering the limitations of new wells and the high cost of well pattern adjustment in offshore oilfields, it is necessary to continuously study the hydrodynamic flow field adjustment methods under well pattern solidification conditions.

[0004] Currently, the most common hydrodynamic adjustment method is cyclic injection-production. However, after oilfields enter the medium-to-high water-cut stage, water channeling and solidification in the injection-production flow field between wells become severe. Meanwhile, a large number of relatively rich areas of residual oil still exist between the well layers within the injection-production well group. The difference in seepage resistance between the water channel and the relatively rich areas of residual oil causes the injected water to continuously circulate ineffectively along the water channel, while the residual oil in the relatively rich areas remains in an undriven state. This invention mainly addresses the coexistence of high water-flooded water channeling and relatively rich areas of residual oil. By changing the seepage resistance of the flow field, it enhances the resistance-increasing effect of the water channeling in the high water-flooded area and reduces the relative seepage resistance in the relatively rich areas, thereby achieving the goal of expanding the oilfield's reach and improving recovery. The establishment of this method has significant engineering application value for improving the recovery rate of offshore oilfields.

[0005] Chinese invention patent CN202110051322.9 discloses a method for optimizing and controlling reservoir flow field based on neural networks. This method includes: Step 1, organizing historical development data of the study area and obtaining reservoir properties and oil and water well production dynamic data; Step 2, designing control intervals; Step 3, establishing a flow field control sample library; Step 4, establishing and optimizing a neural network model; Step 5, predicting the effect of reservoir flow field control.

[0006] The aforementioned patents can quantitatively predict the oil production effect of flow field control schemes, providing effective guidance for reservoir production management decisions and showing good application prospects in the development and adjustment of high water-cut reservoirs; however, the aforementioned technical means cannot achieve balanced injection and production.

[0007] Chinese invention patent CN202010707438.9 discloses a method for adjusting the flow field by exchanging layers in a multi-layered reservoir with ultra-high water cut. The method includes: Step 1. Analysis of the heterogeneity characteristics of the ultra-high water cut reservoir; Step 2. Analysis of water consumption and streamline differences in different chromatograms; Step 3. Study on the distribution characteristics of remaining oil between different layers; Step 4. Feasibility analysis of layer exchange; Step 5. Design and optimization of the flow field adjustment scheme for layer exchange; Step 6. Establishment of flow field adjustment models for layer exchange in different types of reservoirs.

[0008] The aforementioned patents are highly targeted and have great practical applications for ultra-high water-cut multi-layered oil reservoirs. They can utilize the characteristics of vertically stacked multi-layered systems to comprehensively adjust the well network of the reservoirs, transform streamlines, and adjust the flow field, which is of great significance for achieving efficient development of integrated oil reservoirs and further improving the recovery rate. However, they cannot meet the requirements for development and adjustment in offshore oil fields and cannot provide technical insights into the problems of limited new wells and high well network adjustment costs in offshore oil fields.

[0009] To address the coexistence of water channeling and residual oil enrichment between well layers within offshore oilfield water injection well groups, and the inability to effectively displace the solidified residual oil enrichment zone in the water channeling, a novel flow field optimization method based on intelligent calculation of plugging depth is established. This method is grounded in inter-well seepage resistance, adheres to the concept of "balanced injection and production," and utilizes automatic intelligent calculation of the effective plugging depth between well layers to modify the inter-well flow field, increase the seepage resistance of water channeling, expand the driving force of non-water channeling channels and relatively enriched zones, and achieve flow field optimization. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for optimizing the flow field between wells.

[0011] By calculating the depth of inter-layer plugging within the injection well group, the contradiction of water channeling between the layers of the existing injection and production well network can be resolved, thereby achieving the goal of optimizing the flow field between injection and production wells, expanding the reach, and improving the recovery rate.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A method for optimizing the flow field between wells includes the following steps:

[0014] Step 1: Using the water injection well as the center, determine the corresponding oil well;

[0015] Step 2: Calculate the area of ​​the swept zone between wells;

[0016] Step 3: Calculate the regional parameters of the inter-well sweep zone;

[0017] Step 4: Calculate the seepage resistance between injection and production wells;

[0018] Step 5: Establish the relationship between inter-well injection time and plugging depth;

[0019] Step 6: Establish the relationship between seepage resistance and sealing time;

[0020] Step 7: Determine the optimal plugging distance under the maximum oil production constraint.

[0021] Furthermore, in step one, the central well is numbered 0, and the oil wells are numbered sequentially in a clockwise direction as 1, 2, 3, ...

[0022] Furthermore, the area A of the inter-well sweep zone C The calculation formula is as follows:

[0023] A C =A 1A0 +A 1B0 .

[0024] Furthermore, the aforementioned

[0025] Furthermore, the aforementioned

[0026] Furthermore, the aforementioned

[0027] Furthermore, the aforementioned

[0028] Furthermore, the regional parameters of the inter-well swept zone include average permeability, average thickness, and average oil saturation.

[0029] Furthermore, the average permeability is:

[0030] The average thickness is:

[0031] The average oil saturation is:

[0032] Furthermore, the optimal blocking distance is calculated through the following steps:

[0033] Calculate the time required for sealing in each direction and determine the minimum sealing time Tmin;

[0034] Divide the minimum plugging time Tmin into several equal parts, and obtain the optimal plugging time t under the lowest water content technology;

[0035] Calculate the inter-well fluid volume contribution between the central water injection well and the surrounding oil wells;

[0036] The fluid distribution between injection and production wells in a single direction is as follows:

[0037]

[0038]

[0039] The average seepage velocity between injection and production wells is:

[0040]

[0041] This allows us to calculate the average injection-production fluid flow velocity between well layers:

[0042]

[0043] The beneficial effects of this invention are as follows:

[0044] This invention has very practical engineering theoretical application value for improving oil recovery through hydrodynamic flow field optimization, especially for improving the flow field of solidified well networks in offshore oilfields to expand the water injection wave. Attached Figure Description

[0045] Figure 1 This is a flowchart illustrating a novel flow field optimization method for intelligently calculating blockage depth provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the well control zone of the central water injection well; Figure 3 This is the injection-production relationship diagram for well group 1C-3; Figure 4 It is the relationship between well saturation and the fluid volume coefficient after plugging. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0047] Example 1:

[0048] A novel flow field optimization method for intelligently calculating blockage depth, such as Figure 1 As shown, the method includes:

[0049] Step 1: Search for the oil well corresponding to the central water injection well.

[0050] (1) Using the injection well as the center, search and determine all oil wells corresponding to the injection well;

[0051] (2) The central water injection well is numbered 0, and the oil wells are numbered 1, 2, 3... in a clockwise direction;

[0052] Step 2: Calculate the area A of the swept zone between wells. C .

[0053] Calculate the controlled sweep area of ​​the central well and one oil well; well-controlled area calculation:

[0054] A C =A 1A0 +A 1B0

[0055] in:

[0056]

[0057]

[0058] Step 3: Calculate the parameters of the sweep area between wells.

[0059] The average parameters of the swept zone between injection and production wells mainly include:

[0060] The average penetration rate is:

[0061] The average thickness is:

[0062] The average oil saturation is:

[0063] Step 4: Calculate the seepage resistance between injection and production wells.

[0064] (1) According to Darcy's formula for radial flow in a plane:

[0065]

[0066]

[0067] (2) Total pressure drop between injection and production wells:

[0068] Δp=Δp1+Δp2

[0069] Substituting the formula into the equation, we obtain the specific formula for the total pressure drop:

[0070]

[0071] (3) The seepage resistance in the sealed area is:

[0072]

[0073] (4) The seepage resistance in the unsealed area is:

[0074]

[0075] (5) Oil drainage tunnel seepage resistance

[0076]

[0077] in:

[0078] (6) The total seepage resistance of the well network is:

[0079]

[0080] Step 5: Establish curves for injection time and plugging depth t~d between wells.

[0081] (1) Establishing a sealing radius model based on the principle of material balance

[0082]

[0083] Cumulative injection amount:

[0084] Among them, distance is used The velocity at that time represents the average velocity, that is:

[0085]

[0086] (2) Establish the curve of injection time versus plugging depth t~d.

[0087] Therefore, by inputting different values ​​of d, we can obtain the corresponding blocking time t for each blocking radius d:

[0088]

[0089] Step 6: Establish a graph showing the relationship between the seepage resistance R in all directions and the plugging time.

[0090] (1) Using the distance di between the injection well and the surrounding production wells, divide di into several equal parts. Using the above formula, substitute dij into each part to obtain the blocking time tij in each direction, and thus establish the relationship between dij and tij.

[0091] (2) Using dij, substitute the values ​​into the calculation of the seepage resistance R under each sealing radius dij. ij This establishes the correspondence between tij and Rij among injection and production wells.

[0092]

[0093] Step 7: Determine the optimal sealing distance based on maximum oil production

[0094] (1) Calculate the time required for sealing in each direction and determine the minimum sealing time Tmin.

[0095] Using the equations, calculate the sealing time *ti* from the central injection well in each direction. Then, determine the minimum sealing time *Tmin*.

[0096] (2) Maximum oil production constrains the optimal plugging distance

[0097] Divide the minimum plugging time Tmin into several equal parts to obtain the optimal plugging time t under the lowest water cut technology. The subsequent water drive at this time is the result of optimal flow field optimization. Calculate the production rate of the well in each direction at different plugging times t:

[0098]

[0099] when When, corresponding to time t max Calculate the seepage resistance corresponding to d in each direction. maxi The corresponding seepage resistance R in each direction i This allows us to determine the depth of the blockage in each direction.

[0100] (3) Calculate the inter-layer fluid volume contribution between the central injection well and the surrounding oil wells.

[0101] The fluid distribution between injection and production wells in a single direction is as follows:

[0102]

[0103]

[0104] The average seepage velocity between injection and production wells is:

[0105]

[0106] This allows us to calculate the average injection-production fluid flow velocity between well layers:

[0107]

[0108] Example 2:

[0109] To provide a more intuitive understanding of the application effect of the novel flow field optimization method for intelligent calculation of blockage depth provided in Example 1, the specific implementation of the present invention will now be illustrated using the calculation process of the above method as an example.

[0110] Optimization calculations for deep flow field regulation and plugging were performed on the 1C-3 water injection well group in a certain oilfield.

[0111] (1) Search center water injection wells corresponding to oil wells

[0112] Searching for the corresponding production wells around injection well 1C-3 revealed a total of 5 production wells across 12 sub-layers: 1B-7, 1GB-1, 1HB-P2, 273-P2, and 6FB-7, as shown in the figure below.

[0113] (2) Calculate the seepage resistance between injection and production wells in each small layer before and after the plugging.

[0114] The current seepage resistance between injection and production wells in each sub-layer before and after the plugging was calculated, and the seepage resistance after the plugging was calculated. The results are shown in the table below. It can be seen that due to the injection of plugging agent in each sub-layer, the seepage resistance of each sub-layer after the plugging was increased, indicating that a certain degree of sealing was carried out between the well layers.

[0115] Table 1. Changes in inter-well seepage resistance before and after plugging.

[0116]

[0117]

[0118] (3) Optimal sealing and displacement depth between each sub-layer well

[0119] The sealing depth between each sub-layer was calculated, and the results are shown in the table below. It can be seen that each sub-layer achieved sealing to different depths.

[0120] Table 2. Interlayer plugging depth of injection and production wells

[0121]

[0122]

[0123] (4) Relationship between scheduling depth and well saturation

[0124] The relationship between the plugging depth and the inter-well saturation shows that after plugging, the smaller the inter-well saturation, the smaller the oil well contribution fluid volume coefficient. This indicates that the establishment of this method can effectively achieve the optimization and adjustment of the inter-well flow field.

[0125] Table 3. Well Saturation - Fluid Volume Coefficient After Plugging

[0126] Serial Number Water injection well name Small layer Corresponding oil well Inter-well oil saturation Liquid volume coefficient multiple 1 1C-3 21 1HB-P2 0.614 2.868 2 1C-3 21 1B-7 0.63 3.372 3 1C-3 21 6FB-7 0.613 2.755 4 1C-3 22 1HB-P2 0.559 1.164 5 1C-3 22 1B-7 0.558 1.098 6 1C-3 22 6FB-7 0.588 1.933 7 1C-3 23 1HB-P2 0.445 0.212 8 1C-3 23 1B-7 0.455 0.242 9 1C-3 23 6FB-7 0.519 0.587 10 1C-3 24 1HB-P2 0.432 0.182 11 1C-3 24 1B-7 0.447 0.222 12 1C-3 24 6FB-7 0.504 0.457 13 1C-3 28 1GB-1 0.538 0.736 14 1C-3 28 1HB-P2 0.591 1.916 15 1C-3 28 1B-7 0.607 2.479 16 1C-3 29 1GB-1 0.561 1.114 17 1C-3 29 1HB-P2 0.617 2.72 18 1C-3 29 1B-7 0.645 4.006 19 1C-3 30 1GB-1 0.452 0.224 20 1C-3 30 1HB-P2 0.495 0.349 21 1C-3 30 1B-7 0.567 1.273 22 1C-3 35 1GB-1 0.659 6.117 23 1C-3 35 1HB-P2 0.658 5.915 24 1C-3 35 273-P2 0.659 5.929 25 1C-3 36 1GB-1 0.63 3.444 26 1C-3 36 1HB-P2 0.63 3.524 27 1C-3 36 273-P2 0.639 3.538 28 1C-3 37 1GB-1 0.659 6.098 29 1C-3 37 273-P2 0.659 6.034 30 1C-3 38 1GB-1 0.656 5.459 31 1C-3 38 1HB-P2 0.657 5.553 32 1C-3 39 1GB-1 0.631 3.286 33 1C-3 39 1HB-P2 0.627 3.118

[0127] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An interwell flow field optimization method including a barrier distance calculation, comprising: The method comprises the following steps: S1, determining the corresponding oil well of the center well with the water injection well as the center; S2, calculating the swept area between the wells; S3, calculating the area parameter of the swept area between the wells; S4, calculating the injection-production well interwell seepage resistance; S5, establishing the relationship between the injection time and the depth of adjustment and plugging; S6, establishing the relationship between the seepage resistance and the plugging time; S7, determining the optimal plugging distance under the maximum oil production constraint.

2. The interwell flow field optimization method of claim 1, wherein, The step S2 further comprises the calculation of the injection-production well interwell control area region of the heterogeneous area: constructing a center water injection well control area with the water injection well as the center and one-line oil well as the boundary on the plane, and the oil well control distance between adjacent oil wells has a linear relationship with the permeability of the oil well point.

3. The interwell flow field optimization method of claim 2, wherein, The interwell swept area A C The calculation is as follows: A C = A 1A0 + A 1B0 .

4. The interwell flow field optimization method of claim 3, wherein, The 5. The interwell flow field optimization method of claim 4, wherein, The 6. The interwell flow field optimization method of claim 3, wherein, The 7. The interwell flow field optimization method of claim 6, wherein, The 8. An interwell flow field optimization method according to any one of claims 3 to 6, characterized by, The interwell swept area region parameter comprises the average permeability, the average thickness and the average oil saturation.

9. The interwell flow field optimization method of claim 8, wherein, The average permeability is: The average thickness is: the average oil saturation is:

10. The interwell flow field optimization method of claim 9, wherein, The optimal plugging distance is calculated by the following steps: calculating the required time for plugging in each direction to determine the minimum plugging time Tmin; dividing the minimum plugging time Tmin into several parts to obtain the optimal plugging time t under the lowest water cut technology; calculating the liquid contribution between the center water injection well and the surrounding oil well layers; the one-way interwell layer liquid distribution between the injection-production wells is: the average seepage velocity between the injection-production wells is: From this the average injection-production fluid flow rate between the well layers can be calculated:

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