Method for improving recovery efficiency between oil wells of high-water-content oil reservoir injection-production well pattern
By temporarily shutting down high water-cut oil wells and adjusting the pressure distribution of the injection-production well network, the problems of water waste and reservoir damage were solved, achieving efficient water drive and improved recovery rate.
Patent Information
- Application Number
- CN202410990254.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-23
- Publication Date
- 2026-01-23
AI Technical Summary
Existing technologies increase injection pressure and suction pressure differential by simply increasing the injection rate of water wells, which leads to water waste and damage to reservoir rock structure, as well as inefficient circulation of injected water.
By temporarily shutting down high water-cut oil wells in the injection-production well network, the water injection pressure is increased to the reservoir rock fracture pressure. The well with the greatest impact is then shut down, adjusting the pressure distribution of the injection-production well network, expanding the water drive sweep volume, and improving the driving capacity of the injected water.
It improves water drive efficiency, reduces water waste and reservoir damage, lowers the cost of artificial lift and surface oil-water separation, and enhances recovery rate by 2%-5%.
Smart Images
Figure CN121382136A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of water-drive oil reservoir production technology, and in particular to a method for enhancing oil recovery between wells in a high water-cut reservoir injection-production well network. Background Technology
[0002] Major domestic oilfields such as Daqing, Shengli, and Bohai are all continental sedimentary reservoirs, characterized by complex formation conditions, diverse sedimentary types, and significant temporal and spatial variations in rock properties. During waterflooding development of continental reservoirs, the macroscopic and microscopic heterogeneity of the reservoirs leads to differences in permeability across different regions, resulting in varying initiation pressures for fluid absorption. This, in turn, causes differences in fluid absorption pressure and volume, leaving some areas unaffected and resulting in residual oil. Furthermore, in the waterflooded areas, factors such as oil-water interfacial tension prevent the residual oil saturation from decreasing to the level of residual oil saturation.
[0003] In China's continental sedimentary oilfields, chemical flooding has been industrially promoted and applied, or tested in open fields, achieving significant oil production and water reduction effects. In oilfields such as Daqing, chemical flooding blocks have completed the injection of polymer-containing flooding agents and entered the water injection development stage. During the water flooding stage, the permeability of high-permeability reservoirs recovers as the flooding agent is produced, leading to a decrease in injection pressure; while low-permeability reservoirs experience reduced permeability and weakened fluid absorption capacity due to the flooding agent absorbed during chemical flooding. Therefore, to maintain development effectiveness, a relatively high injection pressure should be maintained during subsequent water flooding stages. Summary of the Invention
[0004] (a) Technical problems to be solved This invention provides a method for enhancing oil recovery between wells in a high water-cut reservoir injection-production network. This method overcomes the problems of existing technologies that rely on simply increasing the injection rate of water wells to increase injection pressure and increase suction pressure differential, which leads to excessive waste of water resources and exacerbates reservoir rock structure damage caused by water scouring, further aggravating the problems of inefficient injection and ineffective water circulation.
[0005] (II) Technical Solution To achieve the above objectives, the present invention provides a method for enhancing oil recovery between wells in a high water-cut reservoir injection-production well network, comprising the following steps: Step S1: Collect reservoir information in the application area and water cut information of oil wells in the injection-production well network. Temporarily shut down the high water cut oil wells in the injection-production well network to increase the water injection pressure to the reservoir rock fracture pressure. After reaching the required pressure value, open the temporarily shut oil wells to resume production. Step S2: When the water injection pressure drops to the initial pressure level before shutting in, the oil wells in the injection-production well network that have not participated in the shut-in operation are temporarily shut in, so that the water injection pressure reaches the reservoir rock fracture pressure again, until all oil wells in the injection-production well network complete the shut-in operation and resume production. Step S3: Compare the changes in the production rate and water cut within the injection-production well network before and after each well shutdown in Step S2, and select the well with the highest impact on the changes in the production rate and water cut of the injection-production well network for the next round of well shutdown operation.
[0006] Preferably, in step S1, the collected regional reservoir information includes: reservoir properties, injection-production well network type, and oil-water well connectivity.
[0007] Preferably, the reservoir properties include: permeability, porosity, oil-water affinity, reservoir heterogeneity, and pressure conductivity.
[0008] Preferably, the injection-production well pattern types include: five-point method, seven-point method, nine-point method, reverse seven-point method, reverse nine-point method, and row-column well pattern.
[0009] Preferably, in step S1, if the water well injection pressure cannot rise to the reservoir rock fracture pressure within a predetermined time after temporarily shutting down the oil wells in the injection-production well network, the water well injection pressure is further increased by increasing the number of temporarily shut-down oil wells until the water well injection pressure rises to the reservoir rock fracture pressure.
[0010] Preferably, step S2 includes: Step S21: Confirm that the water well injection pressure has dropped to the initial stable level and there is no further downward trend; Step S22: Select an oil well that has not been closed and temporarily shut it down; Step S23: Observe the change in water well injection pressure after the oil well is shut down. If the water well pressure rises to the reservoir rock fracture pressure, it means that the operation is effective. If the water well injection pressure fails to rise to the reservoir rock fracture pressure, more oil wells that have not been shut down need to be shut down until the water well injection pressure rises to the reservoir rock fracture pressure. Step S24: After the water injection pressure rises to the reservoir rock fracturing pressure, the shut-down water well is reopened to resume production. Step S25: Repeat the above steps until all wells have been shut down and then restarted to resume production.
[0011] Preferably, the process of increasing the water well injection pressure to the reservoir rock fracture pressure can improve the fluidity and reach of the injected water, thereby expanding the water drive reach and driving more crude oil to move towards the production well.
[0012] Preferably, the liquid recovery rate is the total amount of liquid extracted by the injection-production well network, and the water cut rate is the total amount of water in the liquid extracted by the injection-production well network.
[0013] (III) Beneficial Effects This invention provides a method for enhancing oil recovery between wells in a high water-cut reservoir injection-production well network. It allows for the temporary closure of some high water-cut wells in the network, increasing the injection pressure of water wells and thus expanding the water-drive swept volume, thereby enhancing the ability of injected water to drive crude oil. By analyzing the shut-in operations and effects of different wells, the most affected wells can be selected for the next round of shut-in operations, achieving refined well management. This method improves water drive efficiency, eliminating the need for additional water injection to maintain recovery. Furthermore, this method does not require large-scale equipment investment; it utilizes existing equipment in the injection-production well network and can be implemented without affecting normal oil production. This achieves increased injection pressure and expanded water-drive swept volume while reducing the need for additional water injection, thereby alleviating the costs of artificial lift and surface oil-water separation. Attached Figure Description
[0014] Figure 1 This diagram illustrates a method for enhancing oil recovery between wells in a high water-cut oil reservoir injection-production network according to the present invention. Figure 2 A geological model diagram of a four-stage injection site is shown. Detailed Implementation
[0015] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0016] In the description of this invention, it is necessary to understand that the orientations or positional relationships indicated by terms such as "upper," "lower," "left," "right," "inner," "outer," "top," and "bottom" are based on the orientations or positional relationships shown in the accompanying drawings. They are intended only to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the components referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0017] like Figure 1 As shown, this invention provides a method for enhancing oil recovery between wells in a high water-cut oil reservoir injection-production network, comprising the following steps: Step S1: Collect reservoir information in the application area and water cut information of oil wells in the injection-production well network. Temporarily shut down the high water cut oil wells in the injection-production well network to increase the water injection pressure to the reservoir rock fracture pressure. After reaching the required pressure value, open the temporarily shut oil wells to resume production. Once the injection pressure of the well is increased to the reservoir rock fracture pressure, the injected water is more likely to be effectively utilized, with fewer instances of ineffective water injection. This helps to improve the ability of the injected water to drive crude oil, thereby increasing the well's production. The information collected in step S1 regarding the application area of the reservoir includes: reservoir properties, injection-production well network type, and oil-water well connectivity. The reservoir properties include: permeability, porosity, oil-water affinity, reservoir heterogeneity, and pressure transmission capacity. The injection-production well network type includes: five-point method, seven-point method, nine-point method, reverse seven-point method, reverse nine-point method, and row-and-column well network. Permeability is a physical quantity describing the resistance of fluid flow in rock. It is a key factor affecting oil well production and reservoir recovery. High permeability means that fluid can flow more easily in rock, while low permeability makes it difficult to flow. Porosity is the proportion of the volume of voids in rock to the total volume of rock. Porosity is directly related to the oil storage capacity of reservoir and the production capacity of oil well. Reservoirs with high porosity can store more fluid. Oil-water affinity is the degree to which oil and water mix in the reservoir. Pressure transmission capacity is the sensitivity of the reservoir to pressure wave propagation. When temporarily shutting down oil wells in the injection-production well network, priority should be given to oil wells with poor oil-water well connectivity and those located on the edge of the network, based on the connectivity status of the oil and water wells. Poor oil-water well connectivity means that the communication between these oil wells and water wells is not smooth or the connection is not tight. Oil wells with poor oil-water well connectivity cannot effectively receive injected water during the water injection process, resulting in the injected water volume not being able to effectively push the crude oil forward, thus causing ineffective loss. By temporarily shutting down these oil wells, unnecessary waste of water resources can be reduced, and the risk of surface equipment failure caused by excessive water injection pressure can also be reduced. Oil wells located on the periphery of the injection-production well network are more prone to boundary effects during injection due to their geographical location. This causes injected water to bypass the well and flow to more distant areas. Temporarily shutting down these oil wells on the periphery of the injection-production well network helps to concentrate injected water in other more promising areas, thereby improving overall water injection efficiency and oil production. In step S1, if oil wells in the injection-production well network are temporarily shut down, but the injection pressure of the water wells fails to rise to the reservoir rock fracture pressure within the subsequent predetermined observation period, it indicates that there is too much ineffective water injection in the injection-production well network. It is necessary to increase the number of oil wells that are temporarily shut down to reduce the resistance in the water injection process, so that more injected water flows to other oil wells, thereby helping to concentrate the water injection pressure to reach the reservoir rock fracture pressure, and thus more effectively drive crude oil production. In step S1, the planned observation period for the injection pressure of the water well is 30 days. The 30-day time span can provide a relatively sufficient data sample, which is conducive to more accurate analysis of the water injection effect and pressure changes, thereby making reasonable decisions.
[0018] It is important to note that when increasing the number of temporarily closed oil wells, the connection between oil and water wells should be considered. Priority should be given to oil wells with poor connection between oil and water wells and those located on the edge of the injection-production well network. When closing wells, it is necessary to do so gradually, closing only one well at a time. After each adjustment, the change in water well injection pressure should be observed to prevent the pressure from being too high and exceeding the reservoir rock fracturing pressure, which could cause formation fracturing.
[0019] Step S2: When the water injection pressure drops to the initial pressure level before shutting in, the oil wells in the injection-production well network that have not participated in the shut-in operation are temporarily shut in, so that the water injection pressure reaches the reservoir rock fracture pressure again, until all oil wells in the injection-production well network complete the shut-in operation and resume production. The specific operational procedures in step S2 include: Step S21: Confirm that the water well injection pressure has dropped to the initial stable level and there is no further downward trend; Step S22: Select an oil well that has not been closed and temporarily shut it down; Step S23: Observe the change in water well injection pressure after the oil well is shut down. If the water well pressure rises to the reservoir rock fracture pressure, it means that the operation is effective. If the water well injection pressure fails to rise to the reservoir rock fracture pressure, more oil wells that have not been shut down need to be shut down until the water well injection pressure rises to the reservoir rock fracture pressure. Step S24: After the water injection pressure rises to the reservoir rock fracture pressure, the closed water well is reopened to resume production; Step S25: Repeat the above steps until all wells have been shut down and then reopened to resume production; Step S2 involves rotating the shutdown of wells that have not participated in the shutdown operation to adjust the pressure distribution in the injection-production well network to make it more balanced, thereby improving the overall oil production efficiency.
[0020] Step S3: Compare the changes in the production rate and water cut within the injection-production well network before and after each well shutdown in Step S2, and select the well with the highest impact on the changes in the production rate and water cut of the injection-production well network for the next round of well shutdown operation. In step S3, before each well is shut down and after production is resumed, the fluid production rate and water cut of the injection-production well network are measured and recorded. By comparing the data before and after shutdown, the actual impact of each well on the change range of fluid production rate and water cut of the injection-production well network is calculated. The well with the greatest impact on the change range of fluid production rate and water cut of the injection-production well network is selected as the target for the next round of well shut-down operations.
[0021] This example provides a method for enhancing oil recovery among wells in a high water-cut reservoir injection-production well network. Specifically, taking a one-injection-four-production well network as an example, CMG reservoir numerical simulation software is used to establish a network as follows: Figure 2 The geological model of one injection and four extraction points shown was simulated and verified. The geological model with one injection and four extractions includes a water injection well: W1, and oil wells: O1, O2, O3, and O4, with O3 being a high water-cut well. The static parameters of the injection-production well network model with one injection and four production wells are shown in Table 1 below.
[0022] Table 1 Static parameters of the one-injection-four-production injection-production well network model The following schemes were used to validate an inter-well enhanced oil recovery method for a high water-cut reservoir injection-production well network, while controlling for variables: Option 1: Drive the water from well W1 to wells O1, O2, O3, and O4, so that the water cut of wells O1, O2, O3, and O4 reaches 98%; Option 2: Drive water from W1 well to O3 well. When the water cut of O3 well reaches 95%, apply the enhanced oil recovery method between oil wells in the high water-cut reservoir injection-production network to shut down O3 well. Continue to drive water from W1 well to O1, O2, and O4 wells, so that the water cut of O1, O2, and O4 wells reaches 98%. Option 3: Drive water from W1 well to O3 well. When the water cut of O3 well reaches 95%, perform polymer flooding at 0.1 PV. Continue water flooding from W1 well to O1, O2, and O4 wells, so that the water cut of O1, O2, and O4 wells reaches 98%. Option 4: Water drive W1 well to O3 well. When the water cut of O3 well reaches 95%, polymer flooding of 0.1 PV is applied. Using the enhanced oil recovery method between oil wells in the injection-production network of high water-cut reservoirs, O3 well is shut down. W1 well continues to water drive to O1, O2 and O4 wells, so that the water cut of O1, O2 and O4 wells reaches 98%. The effects of Scheme 1 and Scheme 2 on the water-driven oil production of a one-injection-four-production injection-production well network are shown in Table 2 below.
[0023] Table 2. Waterflooding effect of a one-injection-four-production well network to increase oil production. Scheme number Way Cumulative oil production Increased fuel consumption Recovery rate Recovery rate increase 1 Water drive <![CDATA[243374m 3 ]]> 43.48% 2 Water drive + shut-in <![CDATA[255770m 3 ]]> <![CDATA[12396m 3 ]]> 45.69% 2.21% The oil production increase effect of Scheme 3 and Scheme 4 on the polymer flooding network of injection and production wells is shown in Table 3 below.
[0024] Table 3. Oil Enhancement Effect of Polymer Flooding in One-Injection-Four-Production Well Network Scheme number Way Cumulative oil production Increased fuel consumption Recovery rate Recovery rate increase 3 Juqu <![CDATA[404888m 3 ]]> 72.33% 4 Polymer drive + shut-in <![CDATA[418998m 3 ]]> <![CDATA[175624m 3 ]]> 74.86% 2.53% Table 2 shows that: Scheme 1, using pure water drive, produced a total of 243,374 cubic meters of oil with a recovery rate of 43.48%. Scheme 2, based on water drive, applied a method to enhance the recovery rate between oil wells in a high water-cut reservoir injection-production network, increasing the total oil production to 255,770 cubic meters, an increase of 12,396 cubic meters, and the recovery rate to 45.69%, an increase of 2.21 percentage points. Table 3 shows that: Scheme 3, using polymer flooding, produced a cumulative oil volume of 404,888 cubic meters with a recovery rate of 72.33%. Scheme 4, based on polymer flooding, applied an enhanced oil recovery method between wells in a high water-cut reservoir injection-production network, increasing the cumulative oil production to 418,998 cubic meters, an increase of 175,624 cubic meters, and improving the recovery rate to 74.86%, an increase of 2.53 percentage points. Therefore, this method of enhancing oil recovery between injection and production wells in a high water-cut reservoir can increase injection pressure and expand the swept volume, and is expected to increase the recovery rate of the injection and production well network by 2%-5%. At the same time, it can save 15%-30% of the artificial lift cost and the cost of oil-water separation at the surface of produced fluid caused by the traditional method of injecting a large amount of water into the injection well.
[0025] It is understood that the various embodiments mentioned above in this invention can be combined with each other to form combined embodiments without violating the principle and logic. Due to space limitations, this invention will not elaborate further.
[0026] Those skilled in the art will understand that, in the above-described method of the specific implementation, the order in which each step is written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.
[0027] This invention provides a method for enhancing oil recovery between wells in a high water-cut reservoir injection-production well network. By temporarily shutting down some high water-cut wells in the network, the injection pressure of the water wells in the network increases, thereby expanding the water-drive swept volume and improving the ability of injected water to drive crude oil. Through analysis of the shut-in operations and effects of different wells, the wells with the greatest impact can be selected for the next round of shut-in operations, achieving refined management of the wells. This method for enhancing oil recovery between wells in a high water-cut reservoir injection-production well network improves water drive efficiency and eliminates the need for additional water injection to maintain the recovery rate. This method does not require large-scale equipment investment; it can be implemented using only the existing equipment in the injection-production well network without affecting the normal oil production of the network. This achieves the goal of increasing injection pressure and expanding the water-drive swept volume while reducing the need for additional water injection, thus alleviating the costs of artificial lift and surface oil-water separation.
[0028] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A method for enhanced recovery between oil wells of a high water cut reservoir injection pattern, characterized in that, It comprises the following steps: Step S1, collecting oil reservoir information and water cut information of the injection-production well pattern, temporarily closing high water cut oil wells in the injection-production well pattern, increasing the water injection pressure to the reservoir rock fracture pressure, opening the temporarily closed oil wells to resume production when the water injection pressure reaches the required pressure value; Step S2, when the water injection pressure decreases to the initial pressure level before the well was closed, temporarily closing the oil wells in the injection-production well pattern that have not been involved in the well closure operation, so that the water injection pressure reaches the reservoir rock fracture pressure again, until all the oil wells in the injection-production well pattern complete the well closure operation and resume production; Step S3, comparing the change range of the liquid production rate and water cut of the injection-production well pattern before and after each well closure in step S2, selecting the oil well with the highest influence on the change range of the liquid production rate and water cut of the injection-production well pattern for the next round of well closure operation.
2. The method of claim 1, wherein, In step S1, the collection of oil reservoir information includes: reservoir physical properties, injection-production well pattern types, and oil-water well connectivity.
3. The method of claim 2, wherein, The reservoir physical properties include: permeability, porosity, oil-water affinity, reservoir heterogeneity, and pressure transmission capacity.
4. The method of claim 2, wherein, The injection-production well pattern types include: five-point method, seven-point method, nine-point method, reverse seven-point method, reverse nine-point method, and row-column well pattern.
5. The method of claim 1, wherein, In step S1, if the water injection pressure cannot be increased to the reservoir rock fracture pressure within a predetermined time after temporarily closing the oil wells in the injection-production well pattern, the number of temporarily closed oil wells is increased to further increase the water injection pressure until the water injection pressure reaches the reservoir rock fracture pressure.
6. The method of claim 1, wherein, The step S2 comprises: Step S21: confirming that the water injection pressure has decreased to the initial stable level and there is no downward trend; Step S22: selecting an oil well that has not been closed for temporary closure operation; Step S23: observing the change of water injection pressure after closing the oil well, if the water injection pressure rises to the reservoir rock fracture pressure, it means that the operation is effective, if the water injection pressure fails to rise to the reservoir rock fracture pressure, more oil wells that have not been closed need to be further closed until the water injection pressure rises to the reservoir rock fracture pressure; Step S24: after the water injection pressure rises to the reservoir rock fracture pressure, the closed water well is opened again to resume production Step S25: repeat the above steps until all the oil wells have completed the well closure operation and resumed production.
7. The method of claim 1, wherein, The process of increasing the water injection pressure to the reservoir rock fracture pressure can improve the flowability and sweep range of injected water, expand the water drive sweep range, and drive more crude oil to the production well.
8. The method of enhanced recovery between oil wells of a high water cut reservoir injection pattern well network of claim 1, wherein, The liquid production rate is the total amount of liquid extracted from the injection-production well pattern, and the water cut is the total amount of water extracted from the injection-production well pattern.