A method for solving plugging and injecting and mining in a bottom water thick oil reservoir

Abstract

This invention provides a method for unblocking and producing heavy oil reservoirs with bottom water, relating to the field of oil and gas field development technology. The method includes: first, calculating the total injection volume of the water displacement slug based on completion parameters and a fixed displacement radius; then, calculating the total injection volume of the water-soluble unblocking agent displacement slug using a quantitative index based on the second derivative of the planar radial flow velocity; second, establishing a calculation model for the unblocking radius based on the functional relationship between the radial flow velocity of the produced fluid and the radial distance from the bottom of the well, combined with a preset target unblocking cycle, to determine the total injection volume of the oil-soluble unblocking agent unblocking slug; finally, precisely controlling the on-site implementation of the unblocking operation according to a predetermined duration. This invention, through the combination of mathematical modeling and engineering practice, significantly improves the efficiency of unblocking measures, extends the production cycle after well unblocking, and provides an innovative solution and theoretical support for optimized injection and production of reservoir unblocking agents.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and in particular to a method for unblocking and injecting heavy oil reservoirs with bottom water. Background Technology

[0002] Chemical unblocking is a core technology for relieving reservoir blockage and restoring well productivity in oilfield development, and it is widely used to tap the potential and increase production in various oil reservoirs. Among them, bottom-water heavy oil reservoirs, as an important type of oil and gas reserves in my country, are characterized by high crude oil viscosity, high content of heavy components, active bottom water, and poor interlayer conditions. During the extraction process, reservoir pore throat blockage is easily caused by the precipitation of heavy components. Due to bottom water interference, improper design of injection and production parameters in conventional unblocking operations, or rapid discharge of injected chemicals that fail to achieve the expected unblocking radius, or excessive injection of chemicals into the bottom water that does not meet economic standards.

[0003] Steam unblocking is a widely used organic unblocking technology in heavy oil reservoirs. However, in these reservoirs, steam can easily and rapidly breach the oil-water interface, leading to steam waste and uncontrollable unblocking radius. Chemical unblocking has become a more effective method, but existing single unblocking systems cannot meet the needs of the entire process: water-soluble unblocking agents have good injectability and low cost, but cannot achieve targeted unblocking in bottom water reservoirs, and the unblocking radius is uncontrollable; oil-soluble unblocking agents have strong targeting, but are expensive. More importantly, existing chemical unblocking technologies do not fully consider the near-wellbore flow velocity characteristics, and the unblocking agent is easily washed away by high-speed produced fluids, resulting in a utilization rate of less than 30%. Furthermore, there is a lack of quantitative design methods for the unblocking radius and precise design systems for displacement slugs. All publicly available patented technologies, both domestically and internationally, have failed to systematically solve these bottlenecks. For example, the multi-segment injection process proposed in Chinese authorized patent CN202011099862.6 does not consider the severe impact of near-wellbore flow velocity on reagent retention, does not introduce the inflection point of seepage velocity change as the design boundary of the displacement segment, and does not establish a quantitative calculation method for the unblocking radius, resulting in reagents easily entering the bottom water and causing reagent waste. The plugging and unblocking composite system constructed in Chinese authorized patent CN202210152101.5 focuses on water-blocking agent sealing, but does not conduct precise quantitative design of unblocking agent dosage for the characteristics of bottom water heavy oil blockage, failing to solve the core problem of reagent loss at high speed under high production conditions, resulting in limited unblocking effect and high construction cost. The composite unblocking agent proposed in Chinese invention patent CN202110939072.2 does not establish a quantitative method for unblocking radius matching the reservoir's fluid supply capacity, and the displacement segment design is not based on the critical boundary determined by seepage law, making it impossible to achieve precise reagent retention, resulting in large ineffective losses and no guarantee of shelf life. The low-pressure acid injection process proposed in Chinese invention patent CN104653164A relies entirely on experience for unblocking parameters, making it unsuitable for oil wells with different fluid supply capacities and prone to bottom water breakthrough during construction. The oil-soluble unblocking system developed in US authorized patent US11434726B2 only focuses on reagent formulation and segmented injection process, failing to consider the formation radial seepage velocity distribution characteristics and establishing a quantitative correspondence between unblocking parameters and reservoir fluid supply capacity. This is particularly problematic for bottom water reservoirs, where precise reagent delivery is impossible.

[0004] In summary, existing technologies cannot solve the problems of rapid waste of reagents during unblocking in bottom-water heavy oil reservoirs, uncontrollable unblocking radius, and unsatisfactory economic performance of unblocking measures, thus hindering the efficient development of the reservoirs. Therefore, developing a targeted deployment method for unblocking slug combinations has significant practical implications and engineering application value. Summary of the Invention

[0005] The purpose of this invention is to provide a bottom-water heavy oil reservoir unblocking injection and production method to solve the problems of rapid and wasteful chemical re-flow, blind design of unblocking radius, and uneconomical unblocking measures in existing technologies. This method quantifies the formation fluid supply capacity and precisely designs the total injection volume of clear water displaced slugs, the total injection volume of water-soluble unblocking agents, and the total injection volume of oil-soluble unblocking agents. This achieves effective retention and long-term unblocking of the unblocking agents in the target formation, prevents chemicals from entering the bottom water, and controls construction costs.

[0006] This invention provides a method for unblocking and producing heavy oil reservoirs with bottom water, comprising the following steps: (1) Obtain the total daily fluid production and effective thickness of the oil layer, calculate the daily fluid production per meter of oil layer, establish the functional relationship between the radial flow velocity of fluid production and the radial distance from the bottom of the well based on the planar radial flow theory, and obtain the fluid production velocity coefficient used to characterize the reservoir's fluid supply capacity. (2) Based on the completion parameters and the fixed displacement radius of the water displacement slug, the total injection volume of the water displacement slug is calculated by applying the principle of conservation of wellbore and formation pore volume; (3) Using the second derivative of the radial flow velocity of the produced fluid as a quantitative criterion, calculate the optimal displacement radius of the water-soluble unblocking agent based on the produced fluid velocity coefficient; combine the fixed displacement radius of the clear water displacement slug, the effective porosity of the reservoir, the effective thickness of the oil layer and the comprehensive sweep efficiency to calculate the total injection volume of the water-soluble unblocking agent. (4) Based on the preset target unblocking cycle, establish an oil-soluble unblocking radius calculation model that matches the reservoir's fluid supply capacity based on the production rate coefficient, and obtain the unblocking radius of the oil-soluble unblocking agent; combine the displacement radius of the water-soluble unblocking agent, the effective porosity of the reservoir, the formation water cut, the effective thickness of the oil layer and the comprehensive sweep efficiency of the oil-soluble unblocking agent, and calculate the total injection dosage of the oil-soluble unblocking agent; (5) Based on the total injection volume of the water-displacement slug, the total injection volume of the water-soluble unblocking agent, and the total injection dosage of the oil-soluble unblocking agent, each slug is injected for a predetermined duration at a specific injection rate matching the oil-soluble unblocking agent unblocking slug, the water-soluble unblocking agent displacement slug, and the water-displacement slug. (6) After the above three slugs are injected for the predetermined time, the well is shut in. After the well is shut in, the well is opened for production at the predetermined daily production rate to complete the unblocking operation.

[0007] Furthermore, in step (1), the formula for calculating the daily liquid production per meter of oil layer is as follows: The formula for calculating the radial seepage velocity of the product fluid is: In the formula This refers to the daily liquid production per meter of oil layer, expressed in cubic meters per day per meter. The total daily fluid production of the target well is expressed in cubic meters per day. The effective thickness of the oil layer in the target well, in meters; Radial distance from the bottom of the well Radial flow velocity of the product fluid at the location, in meters per day; This represents the radial distance from a point in the formation to the bottom of the well, expressed in meters. The product rate coefficient is expressed in square meters per day. The effective porosity of the reservoir is dimensionless.

[0008] Furthermore, in step (2), the displacement radius is fixed to match the total injection volume of the water displacement slug. The formula for calculating the total injection volume of water replacing the slug is as follows: In the formula The total volume of clean water injected for the unblocking construction, in cubic meters; This refers to the wellbore volume, expressed in cubic meters. The radius of the well shaft is in meters. The effective thickness of the oil layer in the target well, in meters; The effective porosity of the reservoir is dimensionless.

[0009] Furthermore, in step (3), the second derivative of the radial seepage velocity of the product liquid is used. As a criterion, the second derivative of the radial flow velocity of the produced fluid characterizes the degree of change in the rate of change of the radial flow velocity of the produced fluid. The smaller the value, the more gradual the change of the produced fluid velocity with radial distance, and the slower the rate at which the unblocking agent is returned from the formation. The formula for calculating the optimal displacement radius of the water-soluble unblocking agent is as follows: In the formula, R is the displacement radius of the water-soluble unblocking agent, in meters; K is the production rate coefficient, in square meters per day, and the total injection volume of the water-soluble unblocking agent is calculated based on the optimal displacement radius.

[0010] Furthermore, the formula for calculating the total injection volume of the water-soluble unblocking agent is as follows: In the formula The total injection volume of the water-soluble unblocking agent for the target well is expressed in cubic meters. R is the comprehensive sweep efficiency of the water-soluble unblocking agent, with a value of 0.5; R is the displacement radius of the water-soluble unblocking agent, in meters. The radius of water displacement is in meters; ρ represents the effective porosity of the reservoir, dimensionless; h represents the effective thickness of the oil layer, in meters.

[0011] Furthermore, in step (4), the formula for calculating the unblocking radius of the oil-soluble unblocking agent is as follows: In the formula, K is the liquid production rate coefficient, with the unit being square meters per day; The target unblocking cycle is preset, in days; the unblocking radius of the oil-soluble unblocking agent is calculated based on the calculated K value and the given T value, and the dosage of the oil-soluble unblocking agent is further calculated.

[0012] Furthermore, the formula for calculating the total dosage of the oil-soluble unblocking agent is as follows: In the formula The dosage of oil-soluble unblocking agent required for the oil layer, in cubic meters; The water content of the formation is dimensionless. The comprehensive sweep efficiency of the oil-soluble unblocking agent is 0.075, which is dimensionless. R represents the unblocking radius of the oil-soluble unblocking agent, in meters; R represents the displacement radius of the water-soluble unblocking agent, in meters. ρ represents the effective porosity of the reservoir, dimensionless; h represents the effective thickness of the oil layer, in meters.

[0013] Furthermore, in step (5), the injection rate of the oil-soluble unblocking agent into the unblocked slug is 8. 10 cubic meters / hour, water-soluble unblocking agent displacement slug injection rate is 2 At a rate of 3 cubic meters per hour, water is injected at a rate of 3 to 5 cubic meters per hour to replace the slugs. The predetermined injection duration for the three slugs is the injection volume corresponding to each slug divided by the injection rate.

[0014] Furthermore, in step (6), the well shut-in process lasts for 2 to 3 days, and then the well is opened for production.

[0015] Furthermore, the predetermined daily fluid production per meter of oil layer produced during well opening is 1.1 to 1.2 times the daily fluid production before unblocking. The present invention has at least the following beneficial effects: This invention specifically addresses the problems of rapid waste of reagents during unblocking of heavy oil reservoirs with bottom water, blind design of unblocking radius, waste of reagents entering bottom water, and short effective period of unblocking. It is adapted to the reservoir and development characteristics of this type of reservoir, taking into account the unblocking effect, construction economy and reservoir development safety.

[0016] This invention is based on the quantification of reservoir fluid supply capacity and combines the planar radial seepage theory to achieve the scientific quantification design of plug parameters in each section. It abandons the traditional experience-based design mode and accurately adapts to the personalized unblocking needs of oil wells with different fluid supply capacities.

[0017] This invention designs a fixed-radius clean water displacement slug to fill near-wellbore formation pores with low-cost clean water, significantly reducing reagent usage costs, while providing stable hydrodynamic support for directional slug propulsion.

[0018] This invention accurately determines the optimal displacement radius of the water-soluble unblocking agent and forms a barrier by combining its construction and sweep characteristics. This effectively pushes the oil-soluble unblocking agent to the deep formation, avoiding the loss of the oil-soluble unblocking agent due to backflow of high-speed produced fluid. It also simultaneously prevents the risk of the oil-soluble unblocking agent being wasted by entering the bottom water. Furthermore, the water-soluble agent has an auxiliary viscosity-reducing effect, which helps the oil-soluble unblocking agent to quickly unblock.

[0019] This invention achieves precise matching between the unblocking radius of the oil-soluble unblocking agent and the reservoir's fluid supply capacity and target unblocking cycle, allowing the oil-soluble unblocking agent to target deep within the formation, effectively exerting its demulsification and viscosity-reducing effects. At the same time, it precisely quantifies the dosage of the agent, avoiding ineffective waste and effectively extending the unblocking period.

[0020] This invention constructs a three-stage plug synergistic unblocking system, matching the specific injection rate and injection sequence of each plug stage to achieve synergistic effects of deep unblocking, intermediate promotion, and near-wellbore propulsion, significantly improving the utilization rate of unblocking agents.

[0021] The construction process of this invention is simple and controllable, and all parameters have clear quantitative basis. The shut-in and production design are compatible with the reaction characteristics of the unblocking agent, which can quickly restore the oil well production capacity. The process is simple and easy to promote on site, ensuring the efficient and sustainable development of bottom water heavy oil reservoirs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the injection and production process for unblocking heavy oil reservoirs in bottom water as described in this invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of this invention, it should be understood that "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] The present invention will now be further illustrated with specific examples. The following embodiments are only for explaining the present invention and do not constitute a limitation thereof. The test samples and test procedures used in the following embodiments include the following: If the specific experimental conditions are not specified in the embodiments, they are generally performed according to conventional conditions or the conditions recommended by the reagent company; unless otherwise specified, the reagents, consumables, etc. used in the following embodiments can be obtained commercially.

[0026] A bottom-water heavy oil reservoir unblocking injection and production method is implemented through the following steps: Step 1: Obtain basic reservoir parameters, calculate daily fluid production per meter of oil layer, establish the radial flow velocity function of the produced fluid, and determine the fluid production velocity coefficient.

[0027] The daily fluid production per meter of oil layer is taken as the core quantitative indicator of reservoir fluid supply capacity, and its calculation formula is as follows:

[0028] In the formula: Daily fluid production per meter of oil layer, in units of ; The target well's total daily fluid production, in units of... ; The effective thickness of the target well oil layer, in units of .

[0029] Based on the planar radial flow theory of oil and gas reservoir engineering, during oil well production, the formation fluids flow radially towards the bottom of the well. Combining reservoir porosity, oil layer thickness, and daily fluid production capacity, a fundamental calculation formula for the radial flow velocity of the produced fluids is derived. The radial seepage velocity of the product fluid is expressed by the following formula:

[0030] In the formula: Radial distance from the bottom of the well Radial percolation velocity of the product fluid at the location, in units of ; The radial distance (injection radius) from a point in the formation to the bottom of the well, in units of... ; The effective porosity of the reservoir is dimensionless. Step 2: Set a fixed displacement radius for the water displacement slug and calculate the total injection volume of the water displacement slug based on the conservation of formation pore volume.

[0031] Because all reservoir fluid within a 1-meter radius is discharged on the same day, to reduce the injection volume and construction cost of water-soluble unblocking agent, this step involves setting up a water displacement slug. The radial displacement radius of the water displacement slug is fixed at 1 meter. Based on the principle of formation pore volume conservation, a precise calculation model for the total injection volume of the water displacement slug is established. This model uses low-cost water to fill the formation pore space near the wellbore, replacing the need for expensive water-soluble unblocking agent in this area, thereby reducing the total amount of unblocking agent used. Simultaneously, it provides pre-flush fluid dynamics to ensure the directional radial propulsion of the water-soluble unblocking agent.

[0032] During the pre-installed water displacement slug injection process, the injected water first fills the wellbore space, then enters the formation, forming a stable water displacement slug with a radial range of 0-1m around the wellbore, filling the formation pores within this range. Water-soluble unblocking agents will then not need to fill the near-wellbore 0-1m pores, thus achieving the core objective of replacing unblocking agents with water and reducing reagent costs.

[0033] Based on the formation pore volume conservation relationship, a core formula for calculating the total injection volume of the clear water displacement slug is established:

[0034] In the formula, the displacement radius is fixed to match the total injection volume of the water displacement slug. ; The total volume of clean water injected for the unblocking construction is expressed in units of... ; The volume is the total wellbore volume, in units of ; The radius of the wellbore is given in units of 1. ; The definitions of the remaining parameters are the same as those described above.

[0035] Based on the on-site construction requirements of a fixed displacement radius, this model achieves precise quantitative design of the injection volume of the pre-positioned water displacement slug. It replaces the high-priced unblocking agent filling volume in the near-wellbore area with low-cost water, significantly reducing the agent cost of unblocking construction. At the same time, it can ensure that the water displacement slug completely covers the designed radial range, providing a stable driving force for the precise advancement of the unblocking agent.

[0036] Step 3: Using the second derivative of the radial seepage velocity of the produced fluid as a quantitative criterion, determine the optimal displacement radius of the water-soluble unblocking agent and calculate the total injection volume.

[0037] Based on the functional positioning of displacement slugs and considering the reservoir characteristics and development challenges of bottom-water heavy oil reservoirs, this invention selects a water-soluble unblocking agent as the displacement slug medium. The core selection criteria and suitability advantages are as follows: In terms of barrier stability and compatibility with bottom water control, water-soluble unblocking agents have a high degree of compatibility with formation water density and viscosity during the development of heavy oil reservoirs with bottom water. After injection, they can advance uniformly to form a complete and continuous barrier, which can stably prevent the high-speed migration of oil-soluble unblocking agent plugs towards the near-wellbore during production. In terms of construction economy and reservoir protection effect, water-soluble unblocking agents have a wide range of raw materials, simple preparation process, and cost more than 90% lower than oil-soluble agents, which can reduce the cost of unblocking per well.

[0038] Based on the above logic, this invention uses the near-wellbore formation velocity inflection point as the design endpoint of the displacement slug. By precisely advancing the water-soluble unblocking agent displacement slug, the oil-soluble unblocking agent unblocking slug is pushed to the low-velocity deep region, avoiding the oil-soluble unblocking agent from remaining in the near-wellbore high-velocity region or spreading to the ineffective region far from the wellbore, thus ensuring that the unblocking agent remains stably in the target area and reacts fully.

[0039] For construction conditions where water-soluble unblocking agents are slowly injected at a rate of 2~3 m³ / h, based on the aforementioned variation law of radial seepage velocity of the produced liquid, and using the second derivative of the seepage velocity as a quantitative judgment index, a calculation model for the displacement radius of the water-soluble unblocking agent is established to accurately determine the optimal radial distance for injection of the unblocking agent, ensuring that the unblocking agent remains stably in the formation and fully exerts its unblocking effect.

[0040] Based on the aforementioned planar radial seepage theory, the general formula for the radial seepage velocity of the product liquid is:

[0041] In the formula, This is the liquid production rate coefficient, with units of m² / d. The definitions of other parameters are the same as described above.

[0042] Differentiating the formula for the radial seepage velocity of the product fluid, we get: First derivative:

[0043] Second derivative:

[0044] The second derivative in the formula characterizes the degree of change in the radial seepage velocity of the produced fluid. The smaller the value, the more gradual the change in the produced fluid velocity with radial distance, the weaker the erosive effect of the formation fluid on the unblocking agent, and the better the retention stability of the unblocking agent in the formation. Considering the construction characteristics of slowly injecting water-soluble unblocking agents at a rate of 2~3 m³ / h (longitudinal sweep efficiency 70%, lateral sweep efficiency 70%, overall sweep efficiency 0.49), and through indoor experiments and field verification, it was determined that when the second derivative value of the radial seepage velocity of the produced fluid is ≤0.05 (unit: When ), the corresponding radial distance is the optimal displacement radius of the water-soluble unblocking agent.

[0045] By applying the above criterion to an identical transformation, we obtain the general formula for calculating the displacement radius of water-soluble unblocking agents:

[0046] In the formula, The displacement radius of the water-soluble unblocking agent is given in units of [missing information]. .

[0047] Combining the displacement radius matched with the 1m fixed total injection volume of the water displacement slug determined in step two, the actual injection radial range of the water-soluble unblocking agent is from 1m to the optimal displacement radius calculated in this step. This allows for more precise quantification of the amount of unblocking agent injected, achieving synergistic optimization of unblocking effect and construction cost.

[0048] Combined with the displacement radius matching the total injection volume of the 1m fixed water displacement slug determined in step two. The actual radial injection range of the water-soluble unblocking agent is The optimal replacement radius calculated in this step. Based on the principle of formation pore volume conservation, the effective volume of the water-soluble unblocking agent displacing the slug is equal to the product of the effective formation pore volume within its injected radial range and the comprehensive sweep efficiency. Therefore, a formula for calculating the required volume of water-soluble unblocking agent displacing the slug per meter of oil reservoir is established:

[0049] In the formula: The volume of water-soluble unblocking agent required to replace the slug per meter of oil layer, in units of ; The comprehensive sweep efficiency of the water-soluble unblocking agent is specified in this step as 0.5 for the slow injection condition at a rate of 2~3 m³ / h. The definitions of the remaining parameters are the same as those described above.

[0050] Combined with the effective thickness of the target well oil layer determined in step one The formula for calculating the total injection volume of the water-soluble unblocking agent in the target well can be further obtained:

[0051] In the formula: The total injected volume of the water-soluble unblocking agent for the target well, in units of ; The effective thickness of the target well oil layer, in units of Step one has been clearly defined.

[0052] This model first accurately determines the optimal injection range of the unblocking agent by using the second derivative of the seepage velocity, and then accurately quantifies the agent dosage by using the volume conservation formula. This ensures that the oil-soluble unblocking agent can stably remain and play its role in the formation, while avoiding ineffective waste of the agent, thus achieving synergistic optimization of unblocking effect and construction cost.

[0053] Step 4: Establish a calculation model for the unblocking radius based on the preset target unblocking cycle, determine the unblocking radius of the oil-soluble unblocking agent, and calculate the total injected dosage.

[0054] This invention addresses the differences in fluid supply capacity in bottom-water heavy oil reservoirs by establishing a quantitative design method for unblocking radius that precisely matches reservoir characteristics. The main unblocking slug uses an oil-soluble unblocking agent, leveraging its efficient contact and miscibility with formation emulsions and asphaltene plugging materials to improve the system's demulsification and viscosity reduction efficiency. This solves the technical problems of traditional water-soluble unblocking agents preferentially entering the aqueous phase channel in reservoirs, failing to target oil-bearing plugging materials, and easily entering the bottom water layer, resulting in ineffective waste. Addressing the industry pain points of short effective periods and poor stability of conventional unblocking technologies, based on the radial seepage law of produced fluid established in step one and combined with the definition of fluid particle transport velocity, a general calculation model for the unblocking radius is established through definite integral calculation of formation fluid radial seepage transport.

[0055] Based on the planar radial seepage theory established in step one, the general expression for the radial seepage velocity of the formation produced fluid is:

[0056] In the formula, The radial seepage velocity coefficient of the product fluid, in units of Alternatively, the parameters can be determined by fitting the on-site production data of the target well; the definitions of the remaining parameters are the same as in step one.

[0057] The radial seepage velocity of oil phase fluid particles in a formation is its radial migration velocity within the formation, combined with the differential definition of migration velocity. Combining this with the above seepage velocity equation, we obtain the differential governing equation for the migration of the oil-soluble unblocking agent front in the formation:

[0058] In the formula, The effective action time of the unblocking agent in the formation, in units of The definitions of the remaining parameters are the same as those described above.

[0059] Separating the variables from the above differential control equations, we obtain:

[0060] Define the conditions for the engineering boundary value: initial time At that time, the unblocking agent front is located at the bottom of the well, corresponding to a radial distance. When the effective action time of the unblocking agent reaches the preset target unblocking cycle. At that time, the maximum radial distance that the unblocking agent front travels in the formation is the design unblocking radius. .

[0061] Based on the above boundary value conditions, take definite integrals on both sides of the equation after separating the variables:

[0062] Solve the definite integrals on both sides of the equation: The result of the integration on the left side:

[0063] The integral result on the right side:

[0064] By combining the results of the simultaneous integration, we obtain the identity:

[0065] By performing an equivalent transformation on the above identity, we obtain a general formula for calculating the design unblocking radius that precisely matches the reservoir's fluid supply capacity and the target unblocking cycle:

[0066] In the formula: The unblocking radius of the oil-soluble unblocking agent is given in units of [missing information]. ; The preset target unblocking cycle, in units of To address the short effective period of conventional unblocking technologies for bottom water heavy oil reservoirs, the target unblocking cycle can be set at 70 days, but can also be flexibly adjusted according to on-site construction needs. The definitions of the remaining parameters are the same as those described above.

[0067] Based on the calculated unblocking radius of the oil-soluble unblocking agent Based on the principle of formation pore volume conservation and the characteristics of the construction sweep effect of rapid injection of oil-soluble unblocking agents at a rate of 8~10 m³ / h, a quantitative calculation formula for the injection dosage of oil-soluble unblocking agents is established: The oil-soluble unblocking agent was injected rapidly at a rate of 8-10 m³ / h, with both longitudinal and lateral sweep efficiency coefficients of 27.38%. The overall sweep efficiency was calculated. .

[0068] Based on the conservation of formation pore volume and combined with the comprehensive sweep efficiency, a formula for calculating the required dosage of oil-soluble unblocking agent per meter of oil layer is derived.

[0069]

[0070] In the formula: The required dosage of oil-soluble unblocking agent to be injected per meter of oil layer, in units of... ; The unblocking radius of the oil-soluble unblocking agent is given in units of [missing information]. ; The displacement radius of the water-soluble unblocking agent is given in units of [missing information]. ; The effective porosity of the reservoir is dimensionless and has been clearly defined in step one; The comprehensive sweep efficiency of the oil-soluble unblocking agent is 0.075, which is taken as the value for rapid injection at a rate of 8~10 m³ / h. The water cut of the target well formation is dimensionless; it is taken as 50% for typical field conditions. Subsequent embodiments may adjust the water cut value according to actual formation development conditions.

[0071] The definitions of the remaining parameters are the same as those described above.

[0072] Combined with the effective thickness of the target well oil layer determined in step one The formula for calculating the total injection dosage of the oil-soluble unblocking agent in the target well can be further obtained as follows:

[0073] In the formula: The total injected dosage of the oil-soluble unblocking agent for the target well, in units of... ; The effective thickness of the target well oil layer, in units of Step one has been clearly defined.

[0074] This formula can accurately match the dosage design of oil-soluble unblocking agents for wells with different fluid supply capacities and oil layer thicknesses. It forms a complete parameter design system with the unblocking radius calculation model, which can not only ensure that the unblocking agent can fully play its deep unblocking role in the target formation, but also avoid ineffective excessive injection of the agent, thus achieving a balance between the effective period of unblocking and the economic efficiency of construction.

[0075] Step 5: Consider the spillover coefficient, match the specific injection rate of each segment plug, inject each segment plug in sequence, and control the predetermined injection time.

[0076] Based on the differences in the sweep characteristics of each slug during construction, and according to the design dosages calculated in steps two, three, and four, oil-soluble unblocking agent slugs, water-soluble unblocking agent displacement slugs, and water displacement slugs were injected sequentially. During injection, the injection rate and sweep efficiency of each slug were matched. The oil-soluble unblocking agent slugs were injected rapidly at a rate of 8-10 m³ / h (longitudinal and lateral sweep efficiency both 27.38%, overall sweep efficiency 0.075), the water-soluble unblocking agent displacement slugs were injected slowly at a rate of 2-3 m³ / h (longitudinal and lateral sweep efficiency both 70%, overall sweep efficiency 0.49), and the water displacement slugs were injected at a rate of 3-5 m³ / h. Each slug was pushed layer by layer to achieve a synergistic effect of deep unblocking, intermediate promotion, and near-wellbore advancement. The predetermined injection duration for the three slugs was calculated by dividing the corresponding injection volume of the slug by the injection rate.

[0077] Step six: After injection is completed, shut in the well. After shutting in the well, start production at the predetermined daily fluid production rate to complete the unblocking operation.

[0078] After the injection is completed, the well should be shut in for 2-3 days to ensure that the oil-soluble unblocking agent reacts fully with the formation blockage and improve the unblocking efficiency. The planned daily fluid production rate for well opening should be controlled at 1.1-1.2 times the daily fluid production rate before unblocking per meter of oil layer. The purpose is to control the fluid production rate to prevent the agent from being discharged too quickly and to extend the unblocking cycle.

[0079] Example The following examples illustrate the technical solution of the present invention. All quantitative parameters are derived from the supporting basic data table. The core construction process, slug usage calculation formula and values ​​strictly follow the full-process quantitative design method of the present invention.

[0080] Example 1 This embodiment targets a typical production well in a bottom-water heavy oil reservoir. The reservoir is characterized by high crude oil viscosity, high content of asphaltenes and waxes, active bottom water, and thin interlayers. During production, the precipitation of heavy components causes pore and throat blockage, leading to a decrease in fluid production capacity. The bottom-water heavy oil reservoir unblocking injection-production method described in this invention is used for unblocking design and construction. In this embodiment, the formation water cut is initially set at 50%, which can be flexibly adjusted according to the actual development conditions of the target well. The initial basic parameters are as follows: well depth 800m, dynamic fluid level 400m, and total daily fluid production. Effective thickness of oil layer , wellbore radius Wellbore volume reservoir effective porosity Preset target unblocking cycle The fixed radial displacement radius of the water displacement slug Comprehensive sweep efficiency of water-soluble unblocking agents Comprehensive sweep efficiency of oil-soluble unblocking agents The unit price of both oil-soluble and water-soluble unblocking agents is RMB 15,000 / ton. The designed additional dosage of oil-soluble unblocking agent is 2% (i.e., the actual dosage is 102% of the theoretical calculation). The water-soluble unblocking agent is a dry powder type agent, and the designed addition of water-soluble unblocking agent in each cubic meter of displacement slug working fluid is 0.02 tons (2%). The agent density is calculated as 1 ton / m³.

[0081] First, according to the formula The daily liquid production per meter of oil layer was calculated. Based on the planar radial seepage theory of oil and gas reservoir engineering, according to the formula Calculate the product flow rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced fluid and the radial distance from the bottom of the well. This allows for the quantitative characterization of the reservoir's fluid supply capacity.

[0082] Based on the principle of formation pore volume conservation, according to the formula The total injection volume of the target well's clear water displacement slug was calculated. After injection, the slug can fill the formation pores in the near-wellbore 0-1m, providing stable hydrodynamic support for directional slug propulsion.

[0083] With the second derivative of the radial seepage velocity of the product fluid ≤ 0.05 To quantify the judgment indicators, according to the formula The optimal displacement radius of the water-soluble unblocking agent was calculated. Then follow the formula , The theoretical total injection volume of the water-soluble unblocking agent was calculated. The corresponding cost of the reagent is approximately 13,200 yuan, and this segment uses 2-3 [units of something - likely referring to a specific type of plug]. The injection rate is slow, matching its 70% longitudinal and lateral sweep characteristics.

[0084] The formula for calculating the unblocking radius is based on the reservoir's fluid supply capacity and the target unblocking cycle. The unblocking radius of the oil-soluble unblocking agent was calculated. Then, follow the modified formula for the dosage of the oil-soluble unblocking agent according to this invention. (in the formula) The target well formation water cut is taken as 0.5 in this embodiment. The theoretical total injection dosage of the oil-soluble unblocking agent was calculated. Based on the 2% additional chemical dosage, the actual usage of the oil-soluble unblocking agent is calculated to be 44.73 m³ (44.73 tons), corresponding to a chemical cost of approximately 671,000 yuan. This slug uses 8-10... The injection rate is fast, matching its 27.38% sweep characteristics in both directions.

[0085] Based on the parameters of this embodiment, the injection rates are calculated as follows: the injection rate for water displacing the slug is 4 m³ / h, and the predetermined injection time is approximately 3.94 h; the injection rate for water-soluble unblocking agent displacing the slug is 2.5 m³ / h, and the predetermined injection time is approximately 16.96 h; the injection rate for oil-soluble unblocking agent unblocking the slug is 9 m³ / h, and the predetermined injection time is approximately 4.87 h.

[0086] Based on the differences in the construction sweep characteristics of each slug and the design dosage calculated above, each slug is injected into the formation of the target well in the order of oil-soluble unblocking agent unblocking slug, water-soluble unblocking agent displacement slug, and water displacement slug. During the injection process, the injection rate of each slug is matched, and each slug is pushed layer by layer to achieve the synergistic effect of deep unblocking, intermediate advancement, and near-well filling.

[0087] After all slug injections are completed, the target well is shut in for 2-3 days to ensure that the unblocking agent fully contacts and reacts with the formation plugs, thereby improving unblocking efficiency. After the well is shut in, blowout production is carried out on the target well to gradually remove the unblocking reaction residue and the stripped and dissolved plugs from the formation. The well production parameters are continuously monitored until the production capacity stabilizes, thus completing the entire deep unblocking operation process.

[0088] The total cost of the oil-soluble and water-soluble unblocking agents used in this unblocking operation was approximately RMB 684,200. This invention effectively reduces the cost of unblocking agents per well by replacing the ineffective near-wellbore filling with clean water instead of expensive unblocking agents.

[0089] Example 2 The core difference between this embodiment and Embodiment 1 is the target well's reservoir fluid supply capacity. In this embodiment, the total daily fluid production of the target well is different. Daily liquid production per meter of oil layer All other basic parameters, construction techniques, reagent performance parameters, and slug design calculation methods are completely consistent with those in Example 1.

[0090] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The total injection volume of water replacing the plug segment Optimal displacement radius of water-soluble unblocking agent Theoretical total injection volume The corresponding chemical cost is approximately 11,300 yuan, and the unblocking radius of the oil-soluble unblocking agent is... Theoretical total injected drug dose Combined with the 2% additional dosage of the agent, the actual usage was 34.50 m³ (34.50 tons), corresponding to a agent usage cost of approximately 517,500 yuan. The total usage cost of the oil-soluble and water-soluble unblocking agents in this unblocking operation was approximately 528,800 yuan. The calculation method for the predetermined injection time of each block was the same as in Example 1.

[0091] This invention effectively reduces the cost of unblocking agents per well by replacing the ineffective near-wellbore filling with clean water instead of expensive unblocking agents.

[0092] Example 3 The core difference between this embodiment and Embodiment 1 is the target well's reservoir fluid supply capacity. In this embodiment, the total daily fluid production of the target well is different. Daily liquid production per meter of oil layer All other basic parameters, construction techniques, reagent performance parameters, and slug design calculation methods are completely consistent with those in Example 1.

[0093] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The total injection volume of water replacing the plug segment Optimal displacement radius of water-soluble unblocking agent Theoretical total injection volume The corresponding chemical cost is approximately 8,700 yuan, and the unblocking radius of the oil-soluble unblocking agent is... Theoretical total injected drug dose Combined with the 2% additional dosage of the agent, the actual usage was 24.43 m³ (24.43 tons), corresponding to a agent usage cost of approximately 366,500 yuan. The total usage cost of the oil-soluble and water-soluble unblocking agents in this unblocking operation was approximately 375,200 yuan. The calculation method for the predetermined injection time of each block was the same as in Example 1.

[0094] This invention effectively reduces the cost of unblocking agents per well by replacing the ineffective near-wellbore filling with clean water instead of expensive unblocking agents.

[0095] Example 4 The core difference between this embodiment and Embodiment 1 is the target well's reservoir fluid supply capacity. In this embodiment, the total daily fluid production of the target well is different. Daily liquid production per meter of oil layer All other basic parameters, construction techniques, reagent performance parameters, and slug design calculation methods are completely consistent with those in Example 1.

[0096] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The total injection volume of water replacing the plug segment Optimal displacement radius of water-soluble unblocking agent Theoretical total injection volume The corresponding chemical cost is approximately 0.60 million yuan, and the unblocking radius of the oil-soluble unblocking agent is... Theoretical total injected drug dose Combined with the 2% additional dosage of the agent, the actual usage was 14.37 m³ (14.37 tons), corresponding to a agent usage cost of approximately 215,600 yuan. The total usage cost of the oil-soluble and water-soluble unblocking agents in this unblocking operation was approximately 221,600 yuan. The calculation method for the predetermined injection time of each blockage was the same as in Example 1.

[0097] This invention effectively reduces the cost of unblocking agents per well by replacing the ineffective near-wellbore filling with clean water instead of expensive unblocking agents.

[0098] Example 5 The core difference between this embodiment and Embodiment 1 is that the original scheme completely replaces the water-displaced slug with an equal volume of water-soluble unblocking agent working fluid; all other basic parameters remain the same. reservoir fluid supply capacity slug design calculation method Construction process The performance parameters of the drug are completely consistent with those of Example 1.

[0099] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The theoretical volume after replacing the original water-based slug plug with a water-soluble unblocking agent working fluid is: With an additional 2% reagent dosage, the actual working fluid usage is 16.08 m³, corresponding to an actual usage of 0.33 tons of water-soluble unblocking agent, and a reagent cost of approximately 0.50 million yuan. The water-soluble unblocking agent replaces the theoretical total injection volume of the slug working fluid. With an additional 2% reagent dosage, the actual working fluid volume is 43.25 m³, corresponding to an actual usage of 0.88 tons of water-soluble unblocking agent, and a reagent cost of approximately 13,200 yuan; the unblocking radius of the oil-soluble unblocking agent... Theoretical total injected drug dose With an additional 2% dosage of chemicals, the actual usage was 44.73 m³ (44.73 tons), corresponding to a chemical cost of approximately 671,000 yuan. The total cost of the oil-soluble and water-soluble unblocking agents used in this unblocking operation was approximately 689,200 yuan. The calculation method for the predetermined injection time of each slug was the same as in Example 1.

[0100] Example 6 The core difference between this embodiment and Embodiment 2 is that the original scheme completely replaces the water-displaced slug with an equal volume of water-soluble unblocking agent working fluid; all other basic parameters remain the same. reservoir fluid supply capacity slug design calculation method Construction process The performance parameters of the drug are completely consistent with those of Example 2.

[0101] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The theoretical volume after replacing the original water-based slug plug with a water-soluble unblocking agent working fluid is: With an additional 2% reagent dosage, the actual working fluid usage is 16.08 m³, corresponding to an actual usage of 0.33 tons of water-soluble unblocking agent, and a reagent cost of approximately 0.50 million yuan. The water-soluble unblocking agent replaces the theoretical total injection volume of the slug working fluid. With an additional 2% reagent dosage, the actual working fluid volume is 36.59 m³, corresponding to an actual usage of 0.75 tons of water-soluble unblocking agent, and a reagent cost of approximately 11,300 yuan; the unblocking radius of the oil-soluble unblocking agent... Theoretical total injected drug dose With an additional 2% dosage of chemicals, the actual usage was 34.50 m³ (34.50 tons), corresponding to a chemical cost of approximately 517,500 yuan. The total cost of the oil-soluble and water-soluble unblocking agents used in this unblocking operation was approximately 533,800 yuan. The calculation method for the predetermined injection time of each blockage segment was the same as in Example 1.

[0102] Example 7 The core difference between this embodiment and Embodiment 3 is that the original scheme completely replaces the water-displaced slug with an equal volume of water-soluble unblocking agent working fluid; all other basic parameters remain the same. reservoir fluid supply capacity slug design calculation method Construction process The performance parameters of the drug are completely consistent with those of Example 3.

[0103] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The theoretical volume after replacing the original water-based slug plug with a water-soluble unblocking agent working fluid is: With an additional 2% reagent dosage, the actual working fluid usage is 16.08 m³, corresponding to an actual usage of 0.33 tons of water-soluble unblocking agent, and a reagent cost of approximately 0.50 million yuan. The water-soluble unblocking agent replaces the theoretical total injection volume of the slug working fluid. With an additional 2% reagent dosage, the actual working fluid volume is 28.52 m³, corresponding to an actual usage of 0.58 tons of water-soluble unblocking agent, and a reagent cost of approximately 8,700 yuan; the unblocking radius of the oil-soluble unblocking agent... Theoretical total injected drug dose With an additional 2% dosage of chemicals, the actual usage was 24.43 m³ (24.43 tons), corresponding to a chemical cost of approximately 366,500 yuan. The total cost of the oil-soluble and water-soluble unblocking agents used in this unblocking operation was approximately 380,200 yuan. The calculation method for the predetermined injection time of each slug was the same as in Example 1.

[0104] Example 8 The core difference between this embodiment and Embodiment 4 is that the original scheme completely replaces the water-displaced slug with an equal volume of water-soluble unblocking agent working fluid; all other basic parameters remain the same. reservoir fluid supply capacity slug design calculation method Construction process The performance parameters of the drug are completely consistent with those of Example 4.

[0105] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The theoretical volume after replacing the original water-based slug plug with a water-soluble unblocking agent working fluid is: With an additional 2% reagent dosage, the actual working fluid usage is 16.08 m³, corresponding to an actual usage of 0.33 tons of water-soluble unblocking agent, and a reagent cost of approximately 0.50 million yuan. The water-soluble unblocking agent replaces the theoretical total injection volume of the slug working fluid. With an additional 2% reagent dosage, the actual working fluid volume is 19.73 m³, corresponding to an actual usage of 0.40 tons of water-soluble unblocking agent, and a reagent cost of approximately 0.60 million yuan; the unblocking radius of the oil-soluble unblocking agent... Theoretical total injected drug dose With an additional 2% dosage of chemicals, the actual usage was 14.37 m³ (14.37 tons), corresponding to a chemical cost of approximately 215,600 yuan. The total cost of the oil-soluble and water-soluble unblocking agents used in this unblocking operation was approximately 226,600 yuan. The calculation method for the predetermined injection time of each slug was the same as in Example 1.

[0106] Example 9 The core difference between this embodiment and Embodiment 1 is that the original scheme replaces the water-displaced slugs and water-soluble unblocking agents with the same volume of oil-soluble unblocking agents. All other basic parameters, reservoir fluid supply capacity, slug design calculation method, construction technology, agent performance parameters, and main unblocking slug design are completely consistent with Embodiment 1.

[0107] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The total theoretical volume of the original water-displaced plug and the water-soluble unblocking agent replaced with the oil-soluble unblocking agent is 58.16 m³. With an additional 2% dosage, the actual usage is 59.32 m³ (i.e., 59.32 tons), corresponding to a cost of approximately RMB 889,800. The theoretical total injection dosage of the oil-soluble unblocking agent for unblocking the plug is 43.85 m³. With an additional 2% dosage, the actual usage is 44.73 m³ (i.e., 44.73 tons), corresponding to a cost of approximately RMB 671,000. The total cost of the oil-soluble unblocking agent used in this unblocking operation is approximately RMB 1,560,800. The calculation method for the predetermined injection time of each plug is the same as in Example 1.

[0108] Example 10 The core difference between this embodiment and Embodiment 2 is that the original scheme replaces the water-displaced slugs and water-soluble unblocking agents with the same volume of oil-soluble unblocking agents. All other basic parameters, reservoir fluid supply capacity, slug design calculation method, construction technology, agent performance parameters, and main unblocking slug design are completely consistent with Embodiment 2.

[0109] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The total theoretical volume of the original water-displaced plug and the water-soluble unblocking agent replaced with the oil-soluble unblocking agent is 51.63 m³. With an additional 2% dosage, the actual usage is 52.66 m³ (52.66 tons), corresponding to a cost of approximately RMB 789,900. The theoretical total injection dosage of the oil-soluble unblocking agent for unblocking the plug is 33.82 m³. With an additional 2% dosage, the actual usage is 34.50 m³ (34.50 tons), corresponding to a cost of approximately RMB 517,500. The total cost of the oil-soluble unblocking agent used in this unblocking operation is approximately RMB 1,307,400. The calculation method for the predetermined injection time of each plug is the same as in Example 1.

[0110] Example 11 The core difference between this embodiment and Embodiment 3 is that the original scheme replaces the water-displaced slugs and water-soluble unblocking agents with the same volume of oil-soluble unblocking agents. All other basic parameters, reservoir fluid supply capacity, slug design calculation method, construction technology, agent performance parameters, and main unblocking slug design are completely consistent with Embodiment 3.

[0111] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The total theoretical volume of the original water-displaced plug and the water-soluble unblocking agent replaced with the oil-soluble unblocking agent is 43.72 m³. With an additional 2% dosage, the actual usage is 44.59 m³ (44.59 tons), corresponding to a cost of approximately RMB 668,900. The theoretical total injection dosage of the oil-soluble unblocking agent for unblocking the plug is 23.95 m³. With an additional 2% dosage, the actual usage is 24.43 m³ (24.43 tons), corresponding to a cost of approximately RMB 366,500. The total cost of the oil-soluble unblocking agent used in this unblocking operation is approximately RMB 1,035,400. The calculation method for the predetermined injection time of each plug is the same as in Example 1.

[0112] Example 12 The core difference between this embodiment and Embodiment 4 is that the original scheme replaces the water-displaced slugs and water-soluble unblocking agents with the same volume of oil-soluble unblocking agents. All other basic parameters, reservoir fluid supply capacity, slug design calculation method, construction technology, agent performance parameters, and main unblocking slug design are completely consistent with Embodiment 4.

[0113] The key calculation results of this embodiment are as follows: liquid production rate coefficient Establish the corresponding functional relationship between the radial seepage velocity of the produced liquid. The total theoretical volume of the original water-displaced plug and the water-soluble unblocking agent replaced with the oil-soluble unblocking agent is 35.1 m³. With an additional 2% dosage, the actual usage is 35.80 m³ (35.80 tons), corresponding to a cost of approximately 537,000 yuan. The theoretical total injection dosage of the oil-soluble unblocking agent for unblocking the plug is 14.09 m³. With an additional 2% dosage, the actual usage is 14.37 m³ (14.37 tons), corresponding to a cost of approximately 215,600 yuan. The total cost of the oil-soluble unblocking agent used in this unblocking operation is approximately 752,600 yuan. The calculation method for the predetermined injection time of each plug is the same as in Example 1.

[0114] To further verify the economic advantages of the technical solution of the present invention, under the premise that the preset target unblocking cycle is 70 days and the unblocking effect is consistent, the total cost of the unblocking agents in Examples 1 to 12 above is compared in groups, and the comparison results are shown in Table 1.

[0115] Based on the above comparative analysis, the following conclusions can be drawn: Under the premise of the same production volume, the same unblocking cycle and unblocking effect, the total cost of the unblocking agent in the core technical solution of this invention (Examples 1-4) is always the lowest in the same group. The cost reduction is more than 55% compared with the replacement scheme of fully oil-soluble unblocking agent, which fully verifies the significant cost reduction effect achieved by this invention by replacing the high-priced agent near-wellbore ineffective filling with clean water to replace the slug.

[0116] The cost difference between the water-soluble unblocking agent replacement scheme (Examples 5-8) and the core scheme of this invention is minimal. Under the same production volume, the cost increase per well does not exceed 10,000 yuan, and the cost increase is controllable. It can be used as an alternative implementation scheme under special on-site construction conditions.

[0117] The cost of the oil-soluble unblocking agent replacement scheme (Examples 9-12) was significantly higher than the other two schemes under all production flow conditions. It did not have the cost reduction advantage of low-cost media and had the worst economic performance in engineering applications.

[0118] Under the same slug combination scheme, the total daily fluid production of the oil well is positively correlated with the total cost of the unblocking agent. The lower the reservoir fluid supply capacity, the lower the agent usage and the lower the total cost. The unblocking agent optimized injection and production scheme of the present invention can be adapted to the personalized unblocking design needs of oil wells with different production capacities.

[0119] Table 1. Different Implementation Methods and Cost Estimates

[0120] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A method for unblocking and producing heavy oil reservoirs with bottom water, characterized in that, Includes the following steps: (1) Obtain the total daily fluid production and effective thickness of the oil layer, calculate the daily fluid production per meter of oil layer, establish the functional relationship between the radial flow velocity of fluid production and the radial distance from the bottom of the well based on the planar radial flow theory, and obtain the fluid production velocity coefficient used to characterize the reservoir's fluid supply capacity. (2) Based on the completion parameters and the fixed displacement radius of the water displacement slug, the total injection volume of the water displacement slug is calculated by applying the principle of conservation of wellbore and formation pore volume; (3) Using the second derivative of the radial flow velocity of the produced fluid as a quantitative criterion, calculate the optimal displacement radius of the water-soluble unblocking agent based on the produced fluid velocity coefficient; combine the fixed displacement radius of the clear water displacement slug, the effective porosity of the reservoir, the effective thickness of the oil layer and the comprehensive sweep efficiency to calculate the total injection volume of the water-soluble unblocking agent. (4) Based on the preset target unblocking cycle, establish an oil-soluble unblocking radius calculation model that matches the reservoir's fluid supply capacity based on the production rate coefficient, and obtain the unblocking radius of the oil-soluble unblocking agent; combine the displacement radius of the water-soluble unblocking agent, the effective porosity of the reservoir, the formation water cut, the effective thickness of the oil layer and the comprehensive sweep efficiency of the oil-soluble unblocking agent, and calculate the total injection dosage of the oil-soluble unblocking agent; (5) Based on the total injection volume of the water-displacement slug, the total injection volume of the water-soluble unblocking agent, and the total injection dosage of the oil-soluble unblocking agent, each slug is injected for a predetermined duration at a specific injection rate matching the oil-soluble unblocking agent unblocking slug, the water-soluble unblocking agent displacement slug, and the water-displacement slug. (6) After the above three slugs are injected for the predetermined time, the well is shut in. After the well is shut in, the well is opened for production at the predetermined daily production rate to complete the unblocking operation.

2. The bottom water heavy oil reservoir unblocking injection and production method according to claim 1, characterized in that, In step (1), the formula for calculating the daily liquid production per meter of oil layer is as follows: The formula for calculating the radial seepage velocity of the product fluid is: In the formula This refers to the daily liquid production per meter of oil layer, expressed in cubic meters per day per meter. The total daily fluid production of the target well is expressed in cubic meters per day. The effective thickness of the oil layer in the target well, in meters; Radial distance from the bottom of the well Radial flow velocity of the product fluid at the location, in meters per day; This represents the radial distance from a point in the formation to the bottom of the well, expressed in meters. The product rate coefficient is expressed in square meters per day. The effective porosity of the reservoir is dimensionless.

3. The bottom water heavy oil reservoir unblocking injection and production method according to claim 1, characterized in that, In step (2), the displacement radius is fixed to match the total injection volume of the water displacement slug. The formula for calculating the total injection volume of water replacing the slug is as follows: In the formula The total volume of clean water injected for the unblocking construction, in cubic meters; This refers to the wellbore volume, expressed in cubic meters. The radius of the well shaft is in meters. The effective thickness of the oil layer in the target well, in meters; The effective porosity of the reservoir is dimensionless.

4. The bottom water heavy oil reservoir unblocking injection and production method according to claim 1, characterized in that, In step (3), the second derivative of the radial seepage velocity of the product liquid is used. As a criterion, the second derivative of the radial flow velocity of the produced fluid characterizes the degree of change in the rate of change of the radial flow velocity of the produced fluid. The smaller the value, the more gradual the change of the produced fluid velocity with radial distance, and the slower the rate at which the unblocking agent is returned from the formation. The formula for calculating the optimal displacement radius of the water-soluble unblocking agent is as follows: In the formula, R is the displacement radius of the water-soluble unblocking agent, in meters; K is the production rate coefficient, in square meters per day, and the total injection volume of the water-soluble unblocking agent is calculated based on the optimal displacement radius.

5. The bottom water heavy oil reservoir unblocking injection and production method according to claim 4, characterized in that, The formula for calculating the total injection volume of the water-soluble unblocking agent is as follows: In the formula The total injection volume of the water-soluble unblocking agent for the target well is expressed in cubic meters. R is the comprehensive sweep efficiency of the water-soluble unblocking agent, with a value of 0.5; R is the displacement radius of the water-soluble unblocking agent, in meters. The radius of water displacement is in meters; ρ represents the effective porosity of the reservoir, dimensionless; h represents the effective thickness of the oil layer, in meters.

6. The bottom water heavy oil reservoir unblocking injection and production method according to claim 1, characterized in that, In step (4), the formula for calculating the unblocking radius of the oil-soluble unblocking agent is as follows: In the formula, K is the liquid production rate coefficient, with the unit being square meters per day; The target unblocking cycle is preset, in days; the unblocking radius of the oil-soluble unblocking agent is calculated based on the calculated K value and the given T value, and the dosage of the oil-soluble unblocking agent is further calculated.

7. The bottom water heavy oil reservoir unblocking injection and production method according to claim 6, characterized in that, The formula for calculating the total dosage of oil-soluble unblocking agent is as follows: In the formula The dosage of oil-soluble unblocking agent required for the oil layer, in cubic meters; The water content of the formation is dimensionless. The comprehensive sweep efficiency of the oil-soluble unblocking agent is 0.075, which is dimensionless. R represents the unblocking radius of the oil-soluble unblocking agent, in meters; R represents the displacement radius of the water-soluble unblocking agent, in meters. ρ represents the effective porosity of the reservoir, dimensionless; h represents the effective thickness of the oil layer, in meters.

8. The bottom water heavy oil reservoir unblocking injection and production method according to claim 1, characterized in that, In step (5), the injection rate of the oil-soluble unblocking agent into the unblocked slug is 8. 10 cubic meters / hour, water-soluble unblocking agent displacement slug injection rate is 2 At a rate of 3 cubic meters per hour, water is injected at a rate of 3 to 5 cubic meters per hour to replace the slugs. The predetermined injection duration for the three slugs is the injection volume corresponding to each slug divided by the injection rate.

9. The bottom water heavy oil reservoir unblocking injection and production method according to claim 1, characterized in that, In step (6), the well shut-in process takes 2 to 3 days, and then the well is opened for production.

10. The bottom water heavy oil reservoir unblocking injection and production method according to claim 9, characterized in that, The predetermined daily fluid production per meter of oil layer produced during well opening is 1.1 to 1.2 times the daily fluid production before unblocking.

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