A method for evaluating the effect of offshore oilfield water injection well measures

Abstract

The application provides a kind of offshore oilfield injection well measure effect evaluation method, belongs to oilfield development technical field.The core step includes: collecting the basic parameters of injection well, effective oil well, injection-production relationship data and production decline law before measures;Identify the measure type;According to the characteristics of different types, set quantitative standard, judge whether the measure is effective and determine the effective period of injection well measure;Based on the decline law before measures, predict the oil production under the condition of no measures, compare with the actual oil production, and deduct the contribution of other oil well measures, calculate the oil increment;For composite measures, the effect is divided by using the dominant factor contribution weighted method;Combined with the total measure cost and oil increment, calculate the barrel oil production cost, complete the economic evaluation.The application realizes the whole process, quantification and refinement evaluation of injection well measures from technical effectiveness to economic feasibility, especially suitable for offshore oilfield, and provides a reliable basis for optimizing measure decision and improving development efficiency.

Description

Technical Field

[0001] This invention relates to the field of offshore oilfield development technology, and in particular to a method for evaluating the effectiveness of water injection well measures in offshore oilfields. Background Technology

[0002] Water injection is a key technology for maintaining formation pressure and improving oil recovery in offshore oilfields. In actual production, measures such as stratified allocation, acidizing and unblocking, profile control and displacement adjustment, well workover operations, injection / separate injection, and water injection pressure optimization are required to improve injection-production efficiency. However, current evaluations of the effectiveness of water injection measures suffer from the following problems: evaluation indicators are singular, focusing primarily on changes in water injection volume, lacking a systematic and comprehensive evaluation framework; there is a lack of targeted evaluation standards for different types of measures, resulting in poor comparability of evaluation results; calculations of oil enhancement effects do not consider the impact of well measures, leading to insufficient accuracy; and economic evaluations do not consider full costs, making it difficult to accurately reflect the economic benefits of the measures. Therefore, there is an urgent need for a method for evaluating the effectiveness of water injection measures in offshore oilfields. Summary of the Invention

[0003] In view of this, the present invention aims to propose a systematic, accurate, highly operable, and characteristic method for evaluating the effectiveness of water injection well measures in offshore oilfields. This method aims to solve the problems of unsystematic and imprecise evaluation of water injection well measures in existing technologies. It can comprehensively integrate technical and economic indicators to achieve an objective and quantitative evaluation of the effectiveness of different water injection well measures, providing a scientific basis for the refined management and decision-making of offshore oilfields.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: a method for evaluating the effectiveness of water injection well measures in offshore oil fields, comprising the following steps: Step S1: Collect the basic parameters of the target injection well and the effective oil wells with corresponding injection-production relationships, the corresponding injection-production relationship data, and the production decline pattern of the oil wells before the measures. Step S2: Determine the type of water injection well measure; Step S3: Determine whether the implemented water injection well measures are effective according to the quantitative standards corresponding to the measure type. If they are determined to be effective, then determine the validity period of the implemented water injection well measures. Step S4: Calculate the predicted oil production of the effective well under the condition of no measures, and compare it with the actual oil production to calculate the increase in oil production; Step S5: Combine the total cost of the measures with the increased oil production to calculate the cost of increased oil production per barrel and complete the economic evaluation.

[0005] Furthermore, in step S1, the basic parameters of the water injection well and the oil well include the production data of the water injection well, the production data of the oil well, the operation design of the measure, and the implementation report of the measure; the correspondence between the water injection well and the oil well affected by the measure is clarified through reservoir engineering analysis methods; the monthly average daily oil production data of the oil well affected by the measure are collected from the first to the sixth month before the water injection well measure, and the natural decline law of the oil well production before the measure is obtained by using the exponential decline method in the Arps model.

[0006] Furthermore, in step S2, the water injection well measures include six categories: stratified allocation, acidizing and unblocking, profile control and displacement, well workover operations, conversion / division injection, and water injection pressure optimization.

[0007] Furthermore, in step S3, the evaluation methods for determining the effectiveness of water injection well measures include the following six types: Effectiveness assessment method for stratified water injection measures: if the water injection volume of each layer in the whole well is qualified after the injection, the measures are considered effective. The effectiveness of acid-based declogging is assessed as follows: the measure is considered effective if the initial increase in the water absorption index is greater than 0 after the measure is taken. The effectiveness evaluation method for profile control and flood control is as follows: if at least one of the following four indicators is met for more than one month, the measures are considered effective. Method for evaluating the effectiveness of well workover operations: If the measures simultaneously meet the three requirements of tubing strength and corrosion resistance standards, tubing seal inspection and approval, and elimination of safety hazards, then the measures are considered effective. Method for evaluating the effectiveness of transfer / splitting: If the measures simultaneously meet the three requirements of pipe string strength and corrosion protection standards, qualified pipe string sealing, and elimination of safety hazards, then the measures are considered effective; Effectiveness assessment method for water injection pressure optimization: The measure is considered effective if the initial increase in water absorption index is greater than 0 after the measure is taken.

[0008] Furthermore, in step S3, after determining that the measures are effective, the effective period of the measures is determined by dynamic analysis: taking the date on which the measures are determined to be effective as the starting point, the key indicators for the most recent 10 days are determined according to different types of measures. If the time for the key indicators to break through the invalidity threshold is greater than 8 days, then the last day is the end point. The invalid critical point is defined as follows: for stratified allocation, it is when the injection volume is lower than the lower limit of the injection requirement; for acidizing and unblocking and water injection pressure optimization, it is when the water absorption index falls back to the level before the measure; for profile control and drive adjustment, it is when the oil production of the effective well falls back to the level before the measure; for well workover operations and transfer / division injection, it is when the tubing string fails again or the injection volume range requirement cannot be met.

[0009] Furthermore, in step S4, the increase in oil production is determined by the following model: the actual total oil production of the effective oil wells during the effective period of the water injection well measures, minus the natural decline in production predicted based on the production decline law before the measures, and minus the increase in oil production generated by the oil well measures during the same period, thereby calculating the net increase in oil production brought about by the water injection well measures.

[0010] Furthermore, the method for determining the effective period of the water injection well measures is as follows: based on the effective period of the water injection well measures, and compared and corrected with the dynamic analysis results based on the oil production curve. Specifically, within the effective period of the measures, if the monthly oil production curve with the measures intersects with the predicted monthly oil production curve without the measures, and the intersection occurs before the effective period of the water injection well measures, then the month corresponding to the intersection is taken as the end point of the effective period of the water injection well measures; if the intersection occurs after the effective period of the water injection well measures, then the month corresponding to the effective period of the water injection well measures is taken as the end point of the effective period of the water injection well measures; if no intersection occurs, for measures such as stratified allocation, acidizing and unblocking, profile control and displacement, and water injection pressure optimization, the effective period of the water injection well measures is consistent with the effective period of the water injection well measures; for well workover operations and transfer / division injection measures, the effective period of the water injection well measures is taken as the remaining production years after the effective measures.

[0011] Furthermore, in the oil increase calculation step, for cases where multiple measures are implemented in combination and the oil increase effect is difficult to divide, the following principles shall be followed: the weighted division method based on the contribution of the dominant factor shall be given priority, that is, the technical injection increase, the radius of action, and the connectivity with the affected oil well shall be weighted and divided according to each measure; if weighted division cannot be achieved, the overall effect shall be evaluated with one of the main measures as the core.

[0012] Furthermore, when the effective period of water injection well measures spans multiple years, the oil increase calculated within the effective period of the water injection well measures is statistically analyzed by time period.

[0013] Furthermore, in step S5, when conducting the economic evaluation, the cost of increased oil production per barrel during the predicted period of increased oil production is calculated using the following formula: C = T / (6.29 × Q) Where C represents the projected cost per barrel of increased oil production during the projected period, in US dollars; T represents the total cost of the measures, in US dollars; and Q represents the projected increase in oil production during the projected period, in m³. 3 6.29 represents the conversion factor for converting one cubic meter of crude oil to one barrel of oil, in barrels / m³. 3 ; The total cost of the measures includes operating costs, equipment depreciation costs, labor and management costs, and production loss costs caused by the operations.

[0014] Compared with existing technologies, the method for evaluating the effectiveness of water injection well measures in offshore oilfields described in this invention has the following advantages: This invention integrates relevant technical and economic indicators of water injection well measures, and realizes a full-process, quantitative, and refined evaluation of water injection well measures from technical effectiveness to economic feasibility. It is particularly suitable for offshore oilfields and can provide a reliable basis for optimizing measure decisions and improving development efficiency.

[0015] (1) A three-level comprehensive evaluation system of "technical effectiveness judgment → oil enhancement effect calculation → economic feasibility evaluation" was constructed, which overcame the shortcomings of the existing technical evaluation indicators being single and focusing on the change of water injection volume, and realized the whole process, quantitative and refined evaluation from technical effectiveness to economic feasibility; (2) Differentiated effectiveness judgment criteria were formulated for six categories of measures, namely, layered allocation, acidizing and unblocking, profile and drive adjustment, well workover, injection / splitting injection, and water injection pressure optimization. The classification and implementation of measures significantly improved the comparability and objectivity of evaluation results among different types of measures. (3) A net oil increase calculation model of “actual total oil production - natural decline production - oil increase from concurrent well measures” was proposed. By deducting the interference of oil increase from concurrent well measures in the evaluation of the effect of water injection well measures, the problem of artificially high oil increase effect was effectively solved, and the accuracy of oil increase calculation was significantly improved. (4) A dual oil production validity period determination mechanism of "water injection well measure validity period + oil production curve intersection correction" was proposed, which improved the oil production validity period from a single technical validity period to a precise result of joint correction of technical validity period and dynamic production curve, thus avoiding overestimation or underestimation of oil production validity period. (5) To address the difficulty in dividing the oil enhancement effect after multiple measures are implemented in combination, a weighted division method based on the contribution of dominant factors is proposed. This method comprehensively considers three dimensions: technical injection volume, radius of action, and injection-production connectivity, and performs quantitative division to achieve a reasonable distribution of the oil enhancement effect under the influence of multiple measures. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of the method for evaluating the effectiveness of water injection well measures in offshore oilfields as described in this invention.

[0017] Figure 2 This is a flowchart illustrating the determination of the validity period of water injection well measures as described in this invention.

[0018] Figure 3 This is a production curve diagram of the oil production curve with and without measures in Embodiment 1 of the present invention, where the intersection point is after the effective period of the measures.

[0019] Figure 4 This is a production curve diagram of the oil production curve with and without measures described in Embodiment 2 of the present invention, where the intersection point is before the effective period of the measures.

[0020] Figure 5 This is a production curve diagram of the oil production curve with and without measures described in Embodiment 2 of the present invention, where the oil production curves do not intersect. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] This invention relates to a method for evaluating the effectiveness of water injection well measures in offshore oilfields, such as... Figure 1 As shown, it includes the following steps: Step S1, Data Acquisition and Preprocessing: Basic parameters of the target water injection wells and the affected oil wells with a clear injection-production correspondence are collected. These basic parameters include production data of the water injection wells (e.g., daily water injection volume and pressure), production data of the oil wells (e.g., daily oil production and water cut), operational design of the intervention measures, and implementation reports. The correspondence between the water injection wells implementing the intervention and the affected oil wells is clarified using reservoir engineering analysis methods. Furthermore, monthly average daily oil production data of the affected oil wells from the first to the sixth month prior to the intervention are collected. The exponential decline method in the Arps model is used to fit the natural decline pattern of the oil well production before the intervention, laying a data foundation for subsequent comparative analysis.

[0024] Step S2, Identification of Measure Type (Determining the Measure Type of Injection Well): Based on the content of the measures, the specific type of measures to be implemented in the injection well is determined. The types of measures mainly include: stratified allocation, acidizing and unblocking, profile control and displacement, well workover operations, injection transfer / division injection, and injection pressure optimization, totaling six categories.

[0025] Step S3: Determining the effectiveness and validity period of the measures: The effectiveness of the implemented water injection well measures is determined based on the quantitative standards corresponding to the type of measures. If the measures are deemed effective, the technical validity period of the measures is further determined. The specific criteria for judging the effectiveness vary depending on the type of measure and the corresponding key indicators. Effectiveness assessment method for stratified water allocation measures: If the water injection volume of each layer in the well meets the allocation requirements after the implementation of the measures, the measures are deemed effective. Method for evaluating the effectiveness of acid-based deblocking: After implementing the measures, if the initial increase in water absorption index is greater than 0, the measures are considered effective. The effectiveness evaluation method for profile control and flood control is as follows: After the implementation of the measures, if at least one of the four indicators—the slope of the Hall curve increases, the apparent water absorption index decreases, the relative water absorption of the high-permeability section decreases, and the injection pressure increases—can continue to improve and remain so for more than one month (including one month), then the measures are deemed effective. Method for evaluating the effectiveness of well workover operations: After the measures are implemented, the following three requirements must be met simultaneously: the strength and corrosion resistance of the tubing string must meet the standards, the tubing string must pass the inspection and sealing, and the original safety hazards must be eliminated. In this case, the measures are considered effective. Method for evaluating the effectiveness of transfer / splitting: After the measures are implemented, the measures are considered effective if the following three requirements are met simultaneously: the strength and corrosion resistance of the tubing meet the standards, the tubing is successfully sealed, and the safety hazards are eliminated. The effectiveness evaluation method for water injection pressure optimization is as follows: after the implementation of the measures, if the initial increase in the water absorption index is greater than 0, the measures are considered effective.

[0026] After determining the effectiveness of the measures, a dynamic analysis method is used to determine the technical validity period of the measures, such as... Figure 2 As shown: Starting from the date the measure is deemed effective, key indicators (KPIs) are determined for the most recent 10 days according to different measure types. If the time it takes for a KPI to exceed the ineffectiveness threshold is greater than 8 days, then the last day of that period is taken as the end of the measure's effective period. The KPIs for different measure types are shown below: Layered allocation measures: water injection volume for each section of the entire well; Acidification to dissolve blockages and optimization of water injection pressure: depending on the initial increase in water absorption index; Profile and drive adjustment: The slope of the Hall curve, apparent water absorption index, relative water absorption of high-permeability sections, and injection pressure increase; Well workover operations, injection transfer / diversion: whether the strength and corrosion protection of the tubing string meet the standards, whether the tubing string sealing is qualified, and whether the original safety hazards have been eliminated.

[0027] The invalid critical point is specifically: Layered allocation: The water injection volume is lower than the lower limit of the required allocation.

[0028] Acidification to remove blockages and optimization of water injection pressure: The water absorption index will return to the level before the measures were taken.

[0029] Profile and displacement adjustment: The oil production of the affected wells has fallen back to the level before the measures were taken.

[0030] Well workover operations, injection transfer / division injection: situations where tubing string failure occurs again or injection volume requirements cannot be met.

[0031] Step S4, Calculation of oil enhancement effect: Calculate the predicted oil production of the effective well under no-treatment conditions, compare it with the actual oil production, and calculate the increase in oil production; specifically: Calculate the increased oil production resulting from the water injection well measure. The increased oil production is determined using the following model: the actual total oil production of the affected wells during the effective period of the water injection well measure, minus the predicted natural decline production based on the pre-measure production decline law, and further minus the increased oil production generated by the oil well measure during the same period, thus calculating the net increased oil production effect brought about by the water injection well measure. First, based on the pre-measure production decline law determined in step S1, predict the oil production of the affected wells during the effective period of the measure (i.e., the natural decline production) under the condition of no water injection well measure; then, obtain the actual total oil production of the affected wells during the effective period of the measure; finally, subtract the predicted natural decline production from the actual total oil production, and further deduct the increased oil production generated by the oil well measure during the same period, thus obtaining the increased oil production attributed to this water injection well measure.

[0032] The method for determining the effective period of the oil production enhancement measures is as follows: Based on the effective period of the water injection well measures determined in step S3, compare it with the actual oil production curve of the affected well. Within the effective period of the water injection well measures, if the actual monthly oil production curve intersects with the predicted monthly oil production curve without measures, and the intersection occurs before the effective period of the water injection well measures, then the month corresponding to that intersection is taken as the end point of the effective period of the oil production enhancement; if the intersection occurs after the effective period of the water injection well measures, then the month corresponding to the effective period of the water injection well measures is taken as the end point of the effective period of the oil production enhancement; if no intersection occurs, then for stratified blending, acidizing and unblocking, profile control and displacement, and water injection pressure optimization measures, the effective period of the oil production enhancement measures is consistent with the effective period of the water injection well measures; for well workover operations and transfer / division injection measures, the effective period of the oil production enhancement measures is taken as the remaining economic production years after the effective measures for the affected well.

[0033] When multiple measures are implemented comprehensively during the evaluation period and their oil production increases are difficult to distinguish directly, the following principles shall apply: Priority shall be given to the weighted scoring method based on the contribution of the dominant factor, i.e., weighting and scoring shall be performed according to the technical injection increase, radius of effect, and connectivity with the affected oil wells of each measure; if weighted scoring is not feasible, then the overall effect shall be evaluated based on one of the main measures. The specific implementation steps are as follows: (1) Based on the importance of each parameter to the oil production increase effect, assign weight coefficients to them, such as the weight of the injection increase amount α, the weight of the effective radius of action β, and the weight of the connectivity coefficient between injection and production wells γ, and satisfy α+β+γ=1. The weights can be determined by expert scoring or historical data regression analysis.

[0034] (2) By normalizing each parameter, the influence of dimensions was eliminated, and the relative contribution score of each measure was calculated. The calculation formula is: contribution score of measure 1 = α × (increased injection amount of measure 1 / total increased injection amount of all measures) + β × (effective radius of action of measure 1 / maximum effective radius of action of all measures) + γ × (connectivity coefficient between the water injection well where measure 1 is located and the oil well that is affected / maximum connectivity coefficient between the injection and production wells of all measures).

[0035] (3) After obtaining the contribution scores of all N measures, calculate the total score and divide the total increase in oil volume according to the score ratio of each measure.

[0036] If the above weighted splitting cannot be implemented due to incomplete data, difficulty in quantifying parameters, or other technical reasons, then the overall effect will be evaluated based on the measure that plays a leading role.

[0037] When the effective period of a water injection well measure spans multiple years, the calculated increase in oil production within the effective period of the measure should be statistically analyzed in time periods to meet the needs of phased economic evaluation. If the measure does not span multiple years, then time-period statistical analysis is not necessary. For example, the increase in oil production can be calculated separately from the effective date of the measure to the end of that calendar year, and from the beginning of the next year to the end of the predicted effective period, as the basis for calculating the increase in oil production within the predicted effective period and the average increase in oil production per well.

[0038] Step S5, Economic Effect Evaluation: An economic evaluation is conducted by combining the total cost of the measures with the increased oil production calculated in step S4. The core evaluation indicator is the cost per barrel of increased oil production. The calculation formula is as follows: C = T / (6.29 × Q) Where C represents the projected cost per barrel of increased oil production during the projected period, in US dollars; T represents the total cost of the measures, in US dollars; and Q represents the projected increase in oil production during the projected period, in m³. 3 6.29 represents the conversion factor (i.e., 1 cubic meter of crude oil to a barrel of oil) for converting crude oil into a barrel of oil. 3 =6.29 barrels), barrels / m 3 ; The total cost of the measures is a comprehensive cost, including operating costs, equipment depreciation costs, labor and management costs, and production loss costs caused by the operations.

[0039] Example 1

[0040] This embodiment uses a water injection well W1 and its only effective oil well P1 on platform A of an offshore oil field as the evaluation objects. Well W1 experienced increased water injection pressure and decreased water injection volume due to near-wellbore contamination, and acidizing and deblocking measures were implemented.

[0041] S1. Data Acquisition and Preprocessing: Basic parameter collection: Daily injection pressure and daily injection volume for well W1 were collected for the six months prior to and after the acidizing treatment; daily oil production and water cut for well P1 during the corresponding period were also collected. The work design document and construction summary report for this acidizing treatment were obtained.

[0042] Injection-production relationship confirmation: Through reservoir connectivity analysis, it was confirmed that well W1 and well P1 have a single injection-production correspondence, with no interference from other wells.

[0043] Production decline pattern determined: Monthly average daily oil production data of well P1 from month 1 to month 6 before the intervention were selected, and the Arps exponential decline model was used for fitting. The natural decline law equation of well P1 before the intervention was obtained as: Q1=Q0×e (-6×d) Where Q1 is the average daily oil production (cubic meters / day) in the first month before the measure; Q0 is the average daily oil production (cubic meters / day) in the sixth month before the measure; d is the monthly decline rate, dimensionless; and t is the month. P1 The average daily oil production in the sixth month before the measure was 55 cubic meters / day, and the average daily oil production in the first month before the measure was 50 cubic meters / day, with a monthly decline rate of 1.59%.

[0044] S2, Measure Type Identification: Based on the scope of the work, the type of measure to be taken is acid removal and deblocking.

[0045] S3. Determination of the effectiveness and validity period of measures: Effectiveness assessment: The apparent water absorption index of well W1 after the treatment was calculated, from 8.5m before the treatment. 3 / (d·MPa) rose to 11.2m 3 The initial increase factor is (11.2-8.5) / 8.5≈0.32>0. Therefore, the acidification measure is deemed effective.

[0046] Effective period determined: Apparent water absorption index was continuously monitored starting from the effective date of the measure. Monitoring revealed that, beginning on the 201st day after the measure, the apparent water absorption index remained consistently lower than the pre-measure level (8.5m) for 9 out of 10 consecutive days (>8 days). 3 / (d·MPa)). Therefore, the technical validity period of this acidification measure is determined to be 211 days (approximately 7 months).

[0047] S4. Calculation of Oil Enhancement Effect: The validity period of the fuel-enhancing product is determined: The actual monthly oil production of well P1 after the treatment was compared with the monthly oil production without the treatment, predicted based on the S1 decline pattern. The two production curves intersected at the end of the 8th month after the treatment. (See...) Figure 3 Therefore, the effective period for increasing oil production under this measure is determined to be consistent with the effective period for water injection well measures, which is 7 months.

[0048] Calculation of fuel consumption increase: During the 7-month validity period, the actual total oil production of well P1 was 11,000 m³. 3 .

[0049] Based on the natural decline law, without any measures, the predicted oil production for the same period is 8,700 m³. 3 .

[0050] Upon verification, no other production enhancement measures were implemented in well P1 during this period, and there is no need to deduct any additional oil production.

[0051] Therefore, the increase in oil production from this acidizing measure is 11,000 m³. 3 -8,700m 3 =2,300m 3 .

[0052] S5. Economic Performance Evaluation: Total cost of the measure: including acidification operation fees, chemical costs, equipment depreciation, labor management and related production losses during the operation, totaling US$100,000.

[0053] Cost calculation for increased oil production per barrel: Cost of increased oil production per barrel = US$100,000 / (6.29 barrels / m³) 3 ×2,300m 3 ≈6.9 USD / barrel.

[0054] The evaluation results can provide an important reference for decision-making on similar measures in the future, suggesting the need to further optimize construction parameters or cost control.

[0055] Example 2

[0056] This embodiment takes a water injection well W2 and its three corresponding effective oil wells P2, P3 and P4 on a B platform of an offshore oil field as the evaluation object, among which well W2 has implemented a control and drive measure.

[0057] S1. Data Acquisition and Preprocessing: Basic parameter acquisition: Injection pressure and daily injection volume were collected for well W2 for the six months prior to and after the intervention; daily oil production and water cut were collected for wells P2, P3, and P4 during the corresponding periods. The design document and construction summary report for this adjustment and drive operation were obtained.

[0058] Injection-production relationship confirmation: Through dynamic analysis and well location deployment map, it was confirmed that well W2 has a clear injection-production correspondence with wells P2, P3 and P4, forming an injection-production well group.

[0059] The law of diminishing returns has been established: The monthly average daily oil production of wells P2, P3, and P4 in the six months prior to the intervention was fitted with an exponential decline model to obtain their respective natural decline equations.

[0060] The natural decline law equation for well P2 before treatment is: Q2 = 40 × e (-0.0114×t) .

[0061] The equation for the natural decline law of well P3 before the treatment is: Q3 = 74 × e (-0.0191×t) .

[0062] The natural decline law equation before the treatment of well P4 is: Q4 = 56 × e (-0.0204×t) .

[0063] S2, Measure Type Identification: Based on the scope of the work, the type of measure for this operation is determined to be profile / drive adjustment.

[0064] S3. Determination of the effectiveness and validity period of measures: Effectiveness determination: The injection pressure of well W2 increased after the adjustment and drive measures were implemented and remained so for 3 months, indicating that the adjustment and drive measures were effective.

[0065] Validity period determination: According to the provisions of this invention, the measures will be deemed invalid when the total oil production of the affected wells falls back to the level before the measures were implemented. The validity period of this adjustment and drive measures is 6 months.

[0066] S4. Calculation of Oil Enhancement Effect: Determination of the effective period for increased oil production: Actual and predicted oil production curves were plotted for the three wells. It was found that the curve for well P3 intersected in the 5th month; therefore, its effective period for increased oil production was adjusted to 5 months. (See below) Figure 4 The curves for wells P2 and P4 did not intersect within the sixth month after the intervention. Figure 5 Therefore, its oil enhancement period is consistent with the water injection well measure, which is 6 months.

[0067] Calculation of increased oil production: Calculate the increased oil production of each oil well separately.

[0068] P2 Well (6 months): Actual oil production - Predicted oil production = 6,900 m 3 -6,500m 3 =400m 3 .

[0069] P3 well (5 months): Actual oil production - predicted oil production = 9,900 m 3 -9,700m 3 =200m 3 .

[0070] P4 Well (6 months): Actual oil production - Predicted oil production = 10,200 m 3 -8,400m 3 =1,800m 3 .

[0071] Upon verification, only well P4 underwent acidizing and unblocking operations once during the fourth month of this period, and the increased oil production determined by the well acidizing and unblocking measures evaluation report was 1,500 m³. 3 This amount needs to be deducted from the increased oil production of well P4.

[0072] Therefore, the increased oil production from well P4 is corrected to 1,800 - 1,500 = 300 m³. 3 .

[0073] The total increase in fuel consumption from this drive adjustment measure = 400 + 200 + 300 = 900m 3 .

[0074] S5. Economic Performance Evaluation: Total cost of the measure: The total cost of the driving agent, injection operation fee, monitoring fee, and comprehensive management is US$150,000.

[0075] Cost calculation for increased oil production per barrel: Cost of increased oil production per barrel = US$150,000 / (6.29 barrels / m³) 3 ×900m 3 ≈26.5 USD / barrel.

[0076] Evaluation conclusion: The quantitative evaluation results reveal the current cost-effectiveness of the control measures in this block, suggesting that future efforts should focus on reducing the cost of chemical agents or optimizing the injection strategy. It may also be necessary to evaluate its application value from a longer-term perspective of enhanced oil recovery (EOR).

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for evaluating the effectiveness of water injection well measures in offshore oilfields, characterized in that, Includes the following steps: Step S1: Collect the basic parameters of the target injection well and the effective oil wells with corresponding injection-production relationships, the corresponding injection-production relationship data, and the production decline pattern of the oil wells before the measures. Step S2: Determine the type of water injection well measure; Step S3: Determine whether the implemented water injection well measures are effective according to the quantitative standards corresponding to the measure type. If they are determined to be effective, then determine the validity period of the implemented water injection well measures. Step S4: Calculate the predicted oil production of the effective well under the condition of no measures, and compare it with the actual oil production to calculate the increase in oil production; Step S5: Combine the total cost of the measures with the increased oil production to calculate the cost of increased oil production per barrel and complete the economic evaluation.

2. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 1, characterized in that: In step S1, the basic parameters of the water injection well and the oil well include the production data of the water injection well, the production data of the oil well, the operation design of the measure, and the implementation report of the measure. Through reservoir engineering analysis methods, the correspondence between the water injection wells implementing the measure and the oil wells affected by the measure is clarified. The monthly average daily oil production data of the oil wells affected by the measure are collected from the first to the sixth month before the water injection well measure, and the natural decline law of the oil well production before the measure is obtained by using the exponential decline method in the Arps model.

3. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 1, characterized in that: In step S2, the water injection well measures include six categories: stratified allocation, acidizing and unblocking, profile control and drive adjustment, well workover operations, conversion / division injection, and water injection pressure optimization.

4. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 1, characterized in that: In step S3, the evaluation methods for determining whether the water injection well measures are effective include the following six methods: Effectiveness assessment method for stratified water allocation measures: If the water injection volume of each layer in the well meets the allocation requirements after the measures are implemented, the measures are deemed effective. Method for evaluating the effectiveness of acid-based deblocking: After implementing the measures, if the initial increase in water absorption index is greater than 0, the measures are considered effective. Effectiveness evaluation method for profile control and flood control: After the implementation of the measures, if at least one of the four indicators—the slope of the Hall curve increases, the apparent water absorption index decreases, the relative water absorption of the high-permeability section decreases, and the injection pressure increases—can continue to improve and remain so for more than one month, then the measures are deemed effective. Method for evaluating the effectiveness of well workover operations: After the measures are implemented, the following three requirements must be met simultaneously: the strength and corrosion resistance of the tubing string must meet the standards, the tubing string must pass the inspection and sealing, and the original safety hazards must be eliminated. In this case, the measures are considered effective. Method for evaluating the effectiveness of transfer / splitting: After the measures are implemented, the measures are considered effective if the following three requirements are met simultaneously: the strength and corrosion resistance of the tubing meet the standards, the tubing is successfully sealed, and the safety hazards are eliminated. The effectiveness evaluation method for water injection pressure optimization is as follows: after the implementation of the measures, if the initial increase in the water absorption index is greater than 0, the measures are considered effective.

5. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 1, characterized in that: In step S3, after determining that the measures are effective, the dynamic analysis method is used to determine the effective period of the measures: taking the date on which the measures are determined to be effective as the starting point, the key indicators for the most recent 10 days are determined according to different types of measures. If the time for the key indicators to break through the invalidity threshold is greater than 8 days, then the last day is the end point. The invalid critical point is defined as follows: for stratified allocation, it is when the injection volume is lower than the lower limit of the injection requirement; for acidizing and unblocking and water injection pressure optimization, it is when the water absorption index falls back to the level before the measure; for profile control and drive adjustment, it is when the oil production of the effective well falls back to the level before the measure; for well workover operations and transfer / division injection, it is when the tubing string fails again or the injection volume range requirement cannot be met.

6. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 1, characterized in that: In step S4, the increase in oil production is determined by the following model: the actual total oil production of the effective oil wells during the effective period of the water injection well measures, minus the natural decline in production predicted based on the production decline law before the measures, and minus the increase in oil production generated by the oil well measures during the same period, thereby calculating the net increase in oil production brought about by the water injection well measures.

7. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 6, characterized in that: The method for determining the effective period of oil production enhancement measures for water injection wells is as follows: The effective period of water injection well measures is used as a basis, and compared and corrected with the dynamic analysis results based on the oil production curve. Specifically, within the effective period of the measures, if the monthly oil production curve with the measures intersects with the predicted monthly oil production curve without the measures, and the intersection occurs before the effective period of the water injection well measures, then the month corresponding to that intersection is taken as the end point of the effective period of oil production enhancement. If the intersection occurs after the effective period of the water injection well measures, then the month corresponding to the effective period of the water injection well measures is taken as the end point of the effective period of oil production enhancement. If no intersection occurs, for measures such as stratified allocation, acidizing and unblocking, profile control and displacement, and water injection pressure optimization, the effective period of oil production enhancement is consistent with the effective period of the water injection well measures. For well workover operations and transfer / division injection measures, the effective period of oil production enhancement is taken as the remaining production years after the effective oil well measures.

8. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 6, characterized in that: In the process of calculating the increase in oil production, for cases where multiple measures are implemented in combination and the effect of increasing oil production is difficult to divide, the following principles shall be followed: the weighted division method based on the contribution of the dominant factor shall be given priority, that is, the technical injection volume, the radius of action and the connectivity with the affected oil well of each measure shall be weighted and divided; if the weighted division cannot be achieved, the overall effect shall be evaluated with one of the main measures as the core.

9. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 6, characterized in that: When the effective period of water injection well measures spans multiple years, the oil increase calculated within the effective period of the water injection well measures is statistically analyzed by time period.

10. The method for evaluating the effectiveness of water injection well measures in offshore oilfields according to claim 1, characterized in that: In step S5, when conducting the economic evaluation, the cost of increased oil production per barrel during the predicted period of increased oil production is calculated using the following formula: C = T / (6.29 × Q) Where C represents the projected cost per barrel of increased oil production during the projected period, in US dollars; T represents the total cost of the measures, in US dollars; and Q represents the projected increase in oil production during the projected period, in m³. 3 6.29 represents the conversion factor for converting one cubic meter of crude oil to one barrel of oil, in barrels / m³. 3 ; The total cost of the measures includes operating costs, equipment depreciation costs, labor and management costs, and production loss costs caused by the operations.

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