Improved calculation method for reasonable formation pressure maintaining level of water-drive reservoir

Abstract

The invention discloses an improved calculation method for a reasonable formation pressure maintaining level of a water-drive reservoir. The method comprises the following steps: acquiring a target region formation comprehensive compression coefficient and an influence parameter of invalid water injection on pressure recovery; according to the obtained influence parameters of invalid water injection on pressure recovery, the target area invalid water injection rate is determined through an injection-production ratio calculation method; on the basis of the determined invalid water injection ratio, the effective annual water injection rate of the target area since the actually measured formation pressure is calculated, and the effective accumulated water injection rate of the target area since the actually measured formation pressure is calculated by taking the effective annual water injection rate of the second year with the actually measured formation pressure as a substrate; based on the effective accumulated water injection rate, the accumulated oil production rate and the accumulated water production rate, the first-year numerical value of the actually-measured formation pressure of the target area is set as an initial value according to the material balance principle, the reasonable formation pressure over the years is calculated, and whether the formation pressure of the target area is reasonably kept is judged by combining the actually-measured formation pressure numerical value over the years of the target area. Therefore, specific adjustment countermeasures of the next step target area are formulated.

Description

Technical Field

[0001] The invention belongs to the technical field of oil reservoir development, and in particular relates to an improved method for calculating a reasonable formation pressure maintenance level in a water-driven oil reservoir. Background Art

[0002] More than 90% of my country's onshore oil fields are developed by water injection, and the crude oil production from water injection development accounts for more than 85% of the total crude oil production. How to maintain a reasonable formation pressure level is the key to ensuring the crude oil production of water-driven oil reservoirs.

[0003] The maintenance level of formation pressure in an oil reservoir has a significant impact on its development effectiveness. If the formation pressure is too high, waterlogging and other phenomena will occur, rapidly increasing the water cut and impacting the reservoir's recovery rate. This will also lead to increased injection pressure and water injection volume, which in turn increases costs. This will also underutilize the performance of oilfield equipment, increasing energy consumption and production costs. If the formation pressure is too low, the production pressure differential sufficient to drive crude oil to the bottom of the wellbore cannot be generated. Natural gas may even precipitate from the crude oil, forming a three-phase flow pattern and impairing the fluidity of the formation crude oil, leading to a series of negative impacts. Therefore, during the development process, it is crucial to systematically determine the optimal formation pressure, tailored to the geological conditions, development stage, and production technology level of each reservoir. This is crucial for improving oilfield efficiency.

[0004] Current research methods for maintaining formation pressure primarily include the hydrostatic column pressure method, the method for determining formation pressure based on the principle of no degassing, the injection-production balance method, the minimum flow pressure method, the material balance method, the waterflooding effect method, and the relationship curve between formation pressure and the cumulative injection-production ratio. The basic principles of most of these methods have been recognized by the industry and widely applied in field operations. However, these methods rely heavily on extensive dynamic and static reservoir data and development experience to determine the appropriate maintenance level for formation pressure. For oilfields with limited dynamic and static reservoir data, the calculation of the appropriate maintenance level for formation pressure requires reference to relevant data from similar reservoirs, resulting in unreliable evaluation results. Furthermore, for structurally complex reservoirs, ineffective water injection is inevitable during waterflooding development. However, most current methods fail to consider the impact of ineffective water injection on the appropriate maintenance level when evaluating the appropriate maintenance level for formation pressure, resulting in inaccurate calculations and an inability to effectively guide field adjustments.

[0005] Through the above analysis, taking the material balance method as an example, the existing technology does not consider the impact of ineffective water injection on the reasonable formation pressure maintenance level and the lack of core reservoir static parameters such as the reservoir comprehensive compressibility coefficient in the evaluation model, which seriously restricts the accuracy and reliability of the evaluation results of the reasonable formation pressure maintenance level.

[0006] There are the following difficulties in solving the above problems and defects:

[0007] (1) The comprehensive reservoir compression coefficient directly determines the accuracy and reliability of the calculation results of the reasonable formation pressure maintenance level in the target block. The comprehensive reservoir compression coefficient obtained by conventional methods such as reference to similar reservoirs and empirical parameters has a large deviation from the actual target reservoir. How to obtain the comprehensive reservoir compression coefficient in different reservoirs is the key to evaluating the reasonable formation pressure maintenance level of water-drive reservoirs.

[0008] (2) Due to complex reservoir structure, mismatch between injection and production and other reservoir process factors, ineffective water injection occurs during water injection development. How to effectively quantify and evaluate the ineffective water injection rate of oil reservoirs is the key to the accuracy of the material balance method calculation results.

[0009] (3) Historical production data spans a long period of time and is numerous and complex. If all of it is used to calculate the appropriate formation pressure maintenance level, it will result in a large workload and the accuracy of the calculation results cannot be guaranteed. How to select appropriate production data for calculation is the key to ensuring the reliability of the calculation results. Summary of the Invention

[0010] In response to the above problems and defects, the purpose of the present invention is to provide an improved method for calculating the reasonable formation pressure maintenance level of water-drive oil reservoirs, improve the adaptability of the model and the reliability of the evaluation results, solve the problem of accurate calculation of the reasonable formation pressure maintenance level of water-drive oil reservoirs, realize the quantitative evaluation of the formation energy maintenance level of water-drive oil reservoirs, and provide a theoretical basis for the selection of the next reservoir adjustment direction.

[0011] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0012] An improved method for calculating the reasonable formation pressure maintenance level of a water-flooding reservoir comprises the following steps:

[0013] S1. Obtain the comprehensive compressibility coefficient of the target formation and the parameters affecting pressure recovery due to ineffective water injection;

[0014] Collect high-pressure physical properties of reservoir fluids in the target area and historical production data, including: reservoir geological reserves, degassed crude oil density, original volume coefficient of formation crude oil, formation water volume coefficient under current formation pressure conditions, crude oil volume coefficient under current formation pressure conditions, annual oil production, cumulative oil production, annual water production, cumulative water production, annual water injection rate, cumulative water production, and historical formation pressure since the measured formation pressure in the target area;

[0015] Calculate the cumulative injection and production volume difference and the difference between the original formation pressure and the current year's formation pressure in the target area since the measured formation pressure, and use the multivariate linear regression method to fit the relationship between the formation pressure change difference, the cumulative injection and production volume difference and the measured formation pressure years.

[0016] The relevant physical property parameters of the target area reservoir are brought into the fitting coefficients to calculate the comprehensive compressibility coefficient of the target area formation and the parameters affecting the pressure recovery due to ineffective water injection;

[0017] S2. Obtaining the ineffective water injection ratio of the target reservoir;

[0018] In the late stage of high water-cut development of water-driven oil reservoirs, the ratio of ineffective water injection is close to a constant value. Based on the ineffective water injection pressure recovery parameters obtained by fitting in step S1, the ineffective water injection rate of the target area is determined using the injection-production ratio calculation method.

[0019] S3. Obtain the effective cumulative water injection volume of the target area;

[0020] Based on the ineffective water injection ratio determined in step S2, the effective annual water injection volume of the target area since the measured formation pressure was obtained is calculated, and based on the effective annual water injection volume in the second year since the measured formation pressure was obtained, the effective cumulative water injection volume of the target area since the measured formation pressure was obtained is calculated;

[0021] S4. Evaluation of reasonable formation pressure maintenance level based on material balance;

[0022] Based on the effective cumulative water injection volume, cumulative oil production, and cumulative water production in step S3, and using the principle of material balance, the first-year value of the measured formation pressure in the target area is set as the initial value, and the reasonable formation pressure over the years is calculated. Combined with the measured formation pressure values ​​of the target area over the years, it is determined whether the target area formation pressure is maintained at a reasonable level, so as to formulate specific adjustment measures for the next target area.

[0023] According to the above scheme, step S1 includes:

[0024] (1) Convert the surface production data of the target area's cumulative oil production, cumulative water production, and cumulative water injection into the volume of fluid in the formation;

[0025] (2) Calculate the difference in the cumulative injection and production volume since the measured formation pressure in the target area, the difference between the formation pressure test value and the original formation pressure in the target area over the years, and arrange the target area data values ​​over the years in order from the most recent to the most recent year;

[0026] (3) According to the material balance equation The data of the number of years, the difference of the cumulative injection and production volume, and the formation pressure difference in step (2) are fitted using the multivariate linear regression method to obtain the constant and the value of the constant b;

[0027] Where ΔP is the formation pressure difference, MPa; ρ o is the density of crude oil, g / cm 3 ; N is the target area's geological reserves, 10 4 t; B oi is the volume coefficient of the formation crude oil in the original state, m 3 / m3 ; is the comprehensive compressibility coefficient of the target reservoir, MPa -1 ;ΔL p is the difference in the amount of injected and produced fluid, 10 4 m 3 ; t is the number of years; is the comprehensive compression coefficient of the target formation; b is the parameter affecting the pressure recovery due to ineffective water injection, MPa / a.

[0028] According to the above scheme, in step S2, the conversion model between the invalid water injection rate of the target area and the parameter considering the influence of invalid water injection on the pressure recovery rate is:

[0029] Where Q i is the annual water injection volume, 10 4 m 3 ;Q w is the annual water production, 10 4 m 3 ;Q o is the annual oil production, 10 4 t; B w is the volume coefficient of formation water, m 3 / m 3 ; B o is the volume coefficient of crude oil, m 3 / m 3 ρ o is the density of crude oil, g / cm 3 ; IPR is the injection-production ratio of the target area s is the invalid water injection rate of the target area; Z is the comprehensive compression coefficient of the target formation b is the parameter affecting the pressure recovery due to ineffective water injection, MPa / a.

[0030] According to the above scheme, in step S4, based on the material balance equation, the reasonable formation pressure evaluation model of the water flooding reservoir is expressed as:

[0031] Where: p is the reasonable formation pressure, MPa; B w is the volume coefficient of formation water, m 3 / m 3 ; B o is the volume coefficient of crude oil, m 3 / m 3 ρ o is the density of crude oil, g / cm 3 ; is the comprehensive compression coefficient of the target formation; W pm is the cumulative water production in the target area since the second year of measured formation pressure, 10 4 m 3 ; Npm is the cumulative oil production in the target area since the second year of measured formation pressure, 10 4 t;W im The cumulative water injection volume since the second year when the formation pressure in the target area was measured, 10 4 m 3 ;P m-1 It is the measured formation pressure value in the target area in the first year.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The technical solution of the present invention realizes the quantitative evaluation of the reasonable formation pressure maintenance level of water-drive oil reservoirs and promotes the field application of the calculation model of the reasonable formation pressure maintenance level of water-drive oil reservoirs by improving the comprehensive compression coefficient characterization model of the target oil reservoir, introducing the invalid water injection rate and optimizing the historical production data, which are three key innovative methods. The quantitative evaluation of the comprehensive compression coefficient of the target oil reservoir realizes the pertinence of the model evaluation and ensures the reliability of the evaluation results; the invalid water injection rate fully considers the problems such as the effectiveness of water injection caused by the structural characteristics of the reservoir and ensures the accuracy of the model evaluation results; the optimization of historical production data ensures the timeliness of the model evaluation results. This method realizes the quantitative evaluation of the reasonable formation pressure maintenance level of water-drive oil reservoirs and provides a theoretical basis for formulating the next adjustment direction of water-drive oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the implementation methods of the present application, the following is a brief introduction to the drawings required for use in the implementation methods. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a flow chart of the improved method for calculating the reasonable formation pressure maintenance level of a water-flooding oil reservoir according to the present invention;

[0036] Figure 2 is the fitting curve of the comprehensive compressibility coefficient and the influencing parameters of invalid water injection on pressure recovery based on multiple linear regression;

[0037] Figure 3 This is a chart showing the invalid water injection rate of the target area over the years;

[0038] Figure 4 A chart showing the effective cumulative water injection volume of the target area over the years;

[0039] Figure 5 This is a chart for determining the rationality of formation pressure levels over the years based on the principle of material balance. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without making any creative efforts shall fall within the scope of protection of the present application.

[0042] The specific embodiment provides an improved method for calculating the reasonable formation pressure maintenance level of a water drive reservoir. Figure 1 The specific steps are as follows:

[0043] S1. Determine the comprehensive compression coefficient of the target formation and the parameters affecting pressure recovery by ineffective water injection. Collect high-pressure physical properties of the target reservoir fluid and historical production data, including: geological reserves of the reservoir, density of degassed crude oil, original volume coefficient of formation crude oil, volume coefficient of formation water under current formation pressure, volume coefficient of crude oil under current formation pressure, annual oil production, cumulative oil production, annual water production, cumulative water production, annual water injection, cumulative water production, and formation pressure over the years since the measured formation pressure in the target area. Calculate the difference in cumulative injection and production volume over the years since the measured formation pressure in the target area and the difference between the original formation pressure and the current year's formation pressure, and use multiple linear regression to fit the relationship data between the formation pressure change difference, the cumulative injection and production volume difference, and the number of years of measured formation pressure, such as Figure 2 Then, the relevant physical property parameters of the target area reservoir are brought into the fitting coefficients to calculate the comprehensive compression coefficient of the target area formation and the parameters affecting the pressure recovery by ineffective water injection;

[0044] S2. Determine the invalid water injection ratio of the target reservoir. In the late stage of high water content development of water drive oil reservoir, the invalid water injection ratio is close to a constant value. According to the parameters of invalid water injection on pressure recovery obtained by fitting in step S1, the invalid water injection ratio of the target area is determined by using the injection-production ratio calculation method, such as Figure 3 As shown in the figure, the ineffective water injection rate is basically maintained at around 0.35, indicating that only about 65% of the injected water volume is used to maintain the formation pressure in the target area. This is the main reason why the actual injection-production ratio in the target area is greater than 1 but the formation pressure continues to decline.

[0045] S3. Determination of the effective cumulative water injection volume of the target area. Based on the invalid water injection ratio determined in step S2, calculate the effective annual water injection volume of the target area since the measured formation pressure, and use the effective annual water injection volume of the second year with the measured formation pressure as the basis to calculate the effective cumulative water injection volume of the target area since the measured formation pressure, such as Figure 4 shown.

[0046] S4. Evaluation of Reasonable Formation Pressure Maintenance Level Based on Material Balance. Based on the effective cumulative water injection volume, cumulative oil production, cumulative water production, and other relevant data from step S3, and utilizing the material balance principle, the first-year measured formation pressure value of the target area is set as the initial value. The reasonable formation pressure over the years is calculated. Combined with the measured formation pressure values ​​over the years in the target area, the reasonableness of the target area's formation pressure maintenance level is determined, thereby formulating specific adjustment measures for the next target area.

[0047] It should be noted that step S1 includes the following steps:

[0048] (1) Convert the surface production data of fluids such as cumulative oil production (10,000 tons), cumulative water production (10,000 cubic meters), and cumulative water injection volume (10,000 cubic meters) in the target area into the volume of fluids in the formation.

[0049] (1.1) The cumulative oil production (10,000 tons) of the target area is converted into the volume of crude oil (10,000 cubic meters) under formation conditions using physical parameters such as the density of degassed crude oil and the crude oil volume coefficient.

[0050] (1.2) The cumulative water production (10,000 cubic meters) and cumulative water injection (10,000 cubic meters) of the target area are converted into the cumulative water production (10,000 cubic meters) and cumulative water injection (10,000 cubic meters) under formation conditions using the target area formation water volume coefficient.

[0051] (2) Calculate the difference in cumulative injected and produced fluid volume (in ten thousand cubic meters) since the measured formation pressure in the target area and the difference between the target area's historical formation pressure test values ​​and the original formation pressure. Arrange the historical data values ​​in the target area in order from the most recent year. For example, since the complete pressure measurement data for a certain water-flooded reservoir can only be traced back to 2010, the year corresponding to the 2010 data is marked as year 1, the year corresponding to the 2011 data is marked as year 2, and so on until the most recent year with complete pressure measurement data. The sorted data is shown in Table 2.

[0052] Table 2 Target area production data statistics

[0053]

[0054] (3) According to the material balance equation The three sets of data in step (2), namely, the number of years, the difference in the cumulative injection and production volume, and the difference in formation pressure, were fitted using the multivariate linear regression method to obtain the constant and the value of constant b. Where ΔP is the formation pressure difference, MPa; ρ ois the density of crude oil, g / cm 3 ; N is the target area's geological reserves, 10 4 t; B oi is the volume coefficient of the formation crude oil in the original state, m 3 / m 3 ; is the comprehensive compressibility coefficient of the target reservoir, MPa -1 ;ΔL p is the cumulative injection and production volume difference, 10 4 m 3 b is the effect of ineffective water injection on the pressure recovery rate, MPa / a; t is years. The comprehensive compressibility of the target reservoir is calculated based on physical parameters such as the target reservoir's geological reserves, crude oil density, and the original formation crude oil volume coefficient.

[0055] At the same time, it should be noted that in step S2, the ineffective water injection ratio of the target reservoir is determined based on the injection-production ratio calculation model. The parameter b determined by fitting in step S1 is used to establish a conversion model between the ineffective water injection ratio and the parameter considering the impact of ineffective water injection on the pressure recovery rate. The model establishment method takes a water-flooding reservoir without considering edge water intrusion as an example. Considering the impact of ineffective water injection on the pressure recovery rate, the material balance equation of the water-flooding reservoir can be expressed as: If the effect of ineffective water injection on the material balance of water-flooded reservoirs is considered, the material balance equation of water-flooded reservoirs can be expressed as: Because the research is about the conversion relationship between the effect of invalid water injection on pressure recovery speed and invalid water injection rate, the formula can be made In addition, according to the actual injection-production ratio calculation formula under the mining conditions, the formula is: Combining the two formulas, we can obtain the conversion model between the invalid water injection rate s and the parameter b that considers the impact of invalid water injection on the pressure recovery rate: Where, is the pressure recovery rate, MPa / a; Q i is the annual water injection volume, 10 4 m 3 ;Q w is the annual water production, 10 4 m 3 ;Q o is the annual oil production, 10 4 t; IPR is the injection-production ratio of the target area; s is the ineffective water injection rate of the target area.

[0056] At the same time, it should be noted that in step S3, the calculation of the effective cumulative water injection volume of the target area is first calculated based on the invalid water injection rate in step S2 to determine the effective annual water injection volume of the target area. Since the invalid water injection rate of the target area is only obtained by fitting the data since the target area reservoir has measured formation pressure, the invalid water injection rate can only be used to calculate the effective annual water injection volume since the target area reservoir has measured formation pressure. Because the measured formation pressure of the target area in the first year is used as the initial value, the effective cumulative water injection volume is accumulated based on the effective annual water injection volume of the second year after the target area has measured formation pressure.

[0057] At the same time, it should be noted that in step S4, the calculation of reasonable formation pressure is mainly based on the construction of an evaluation model based on the material balance equation. Taking the water-flooding reservoir without considering edge water intrusion as an example, the evaluation model of reasonable formation pressure in the water-flooding reservoir can be expressed as follows according to the material balance equation: Where: p is the reasonable formation pressure, MPa; W pm is the cumulative water production in the target area since the second year of measured formation pressure, 10 4 m 3 ; N pm is the cumulative oil production in the target area since the second year of measured formation pressure, 10 4 t;W im The cumulative water injection volume since the second year when the formation pressure in the target area was measured, 10 4 m 3 ;P m-1 The first-year measured formation pressure value of the target area. Comparing the calculated reasonable formation pressure value in recent years with the measured formation pressure value in the target area in recent years determines whether the current reservoir energy retention level is reasonable, providing a theoretical basis for determining whether the reservoir needs energy replenishment in the next step.

[0058] Attachment Figure 5 A comparison of the target area's reasonable and actual formation pressure retention levels over the years revealed that the target area's pressure retention levels over the years were consistently lower than reasonable, indicating an intensified reservoir deficit and a further decrease in formation energy retention. The reservoir urgently needs to adjust its injection-production relationship, intensify water injection, and replenish formation energy.

[0059] In summary, this application provides an improved method for calculating the optimal formation pressure maintenance level in water-flooding reservoirs. By employing three key innovative approaches—improving the target reservoir's comprehensive compressibility characterization model, introducing ineffective water injection rates, and optimizing historical production data—this method achieves a quantitative evaluation of the optimal formation pressure maintenance level in water-flooding reservoirs, promoting their field application.

[0060] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. An improved method for calculating the reasonable formation pressure maintenance level of a water-flooded oil reservoir, characterized in that The following steps are involved: S1. Obtain the comprehensive compressibility coefficient of the target formation and the parameters affecting the pressure recovery by ineffective water injection; Collect high-pressure physical properties of reservoir fluids in the target area and historical production data, including: reservoir geological reserves, degassed crude oil density, original volume coefficient of formation crude oil, formation water volume coefficient under current formation pressure conditions, crude oil volume coefficient under current formation pressure conditions, annual oil production, cumulative oil production, annual water production, cumulative water production, annual water injection rate, cumulative water production, and historical formation pressure since the measured formation pressure in the target area; Calculate the cumulative injection and production volume difference over the years since the measured formation pressure in the target area and the difference between the original formation pressure and the current year's formation pressure, and use the multivariate linear regression method to fit the relationship data between the formation pressure change difference, the cumulative injection and production volume difference and the measured formation pressure years; The relevant physical property parameters of the target area reservoir are brought into the fitting coefficients to calculate the comprehensive compressibility coefficient of the target area formation and the parameters affecting the pressure recovery due to ineffective water injection; S2. Obtaining the ineffective water injection ratio of the target reservoir; In the late stage of high water-cut development of water-driven oil reservoirs, the ratio of ineffective water injection is close to a constant value. Based on the ineffective water injection pressure recovery parameters obtained by fitting in step S1, the ineffective water injection rate of the target area is determined using the injection-production ratio calculation method. S3. Obtain the effective cumulative water injection volume of the target area; Based on the ineffective water injection ratio determined in step S2, the effective annual water injection volume of the target area since the measured formation pressure was obtained is calculated, and based on the effective annual water injection volume in the second year since the measured formation pressure was obtained, the effective cumulative water injection volume of the target area since the measured formation pressure was obtained is calculated; S4. Evaluation of reasonable formation pressure maintenance level based on material balance; Based on the effective cumulative water injection volume, cumulative oil production, and cumulative water production in step S3, and using the principle of material balance, the first-year value of the measured formation pressure in the target area is set as the initial value, and the reasonable formation pressure over the years is calculated. Combined with the measured formation pressure values ​​of the target area over the years, it is determined whether the target area formation pressure is maintained at a reasonable level, so as to formulate specific adjustment measures for the next target area.

2. The improved method for calculating the reasonable formation pressure maintenance level of a water-flooding reservoir as claimed in claim 1 is characterized in that The step S1 comprises: (1) Convert the surface production data of the target area's cumulative oil production, cumulative water production, and cumulative water injection into the volume of fluid in the formation; (2) Calculate the difference in the cumulative injection and production volume since the measured formation pressure in the target area, the difference between the formation pressure test value and the original formation pressure in the target area over the years, and arrange the target area data values ​​over the years in order from the most recent to the most recent year; (3) According to the material balance equation The data of the number of years, the difference of the cumulative injection and production volume, and the formation pressure difference in step (2) are fitted using the multivariate linear regression method to obtain the constant and the value of the constant b; Where ΔP is the formation pressure difference, MPa; ρ o is the density of crude oil, g / cm 3 ; N is the target area's geological reserves, 10 4 t; B oi is the volume coefficient of the formation crude oil in the original state, m 3 / m 3 ; is the comprehensive compressibility coefficient of the target reservoir, MPa -1 ;ΔL p is the difference in the amount of injected and produced fluid, 10 4 m 3 ; t is the number of years; is the comprehensive compression coefficient of the target formation; b is the parameter affecting the pressure recovery due to ineffective water injection, MPa / a.

3. The improved method for calculating the reasonable formation pressure maintenance level of a water-flooding reservoir as claimed in claim 1 is characterized in that In step S2, the conversion model between the target area invalid water injection rate and the parameter considering the influence of invalid water injection on the pressure recovery rate is: Where Q i is the annual water injection volume, 10 4 m 3 ;Q w is the annual water production, 10 4 m 3 ;Q o is the annual oil production, 10 4 t; B w is the volume coefficient of formation water, m 3 / m 3 ; B o is the volume coefficient of crude oil, m 3 / m 3 ; ρ o is the density of crude oil, g / cm 3 ; IPR is the injection-production ratio of the target area s is the invalid water injection rate of the target area; Z is the comprehensive compression coefficient of the target formation b is the parameter affecting the pressure recovery due to ineffective water injection, MPa / a.

4. The improved method for calculating the reasonable formation pressure maintenance level of a water-flooding reservoir as claimed in claim 1 is characterized in that In step S4, according to the material balance equation, the reasonable formation pressure evaluation model of the water flooding reservoir is expressed as: Where: p is the reasonable formation pressure, MPa; B w is the volume coefficient of formation water, m 3 / m 3 ; B o is the volume coefficient of crude oil, m 3 / m 3 ; ρ o is the density of crude oil, g / cm 3 ; is the comprehensive compression coefficient of the target formation; W pm is the cumulative water production in the target area since the second year of measured formation pressure, 10 4 m 3 ; N pm is the cumulative oil production in the target area since the second year of measured formation pressure, 10 4 t;W im The cumulative water injection volume since the second year when the formation pressure in the target area was measured, 10 4 m 3 ;P m-1 It is the measured formation pressure value in the target area in the first year.

Images