A method and system for identifying large pores in offshore loose sandstone reservoirs

Abstract

This invention belongs to the field of petroleum development technology and relates to a method and system for identifying large channels in offshore loose sandstone oil reservoirs. The method includes: collecting static data of production wells and injection wells within a target block, as well as dynamic production data over a period of time; calculating the control volume and inter-well conductivity based on the static and dynamic data; calculating permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient based on the control volume and inter-well conductivity; weighting and normalizing the permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient to obtain a comprehensive evaluation factor; and determining whether the comprehensive evaluation factor is greater than a threshold. If so, the loose sandstone oil reservoir is considered to have large channels. This method can accurately identify large channels and dominant pathways in offshore loose sandstone oil reservoirs, enabling targeted adjustments and remediation measures for various dominant pathways.

Description

Technical Field

[0001] This invention relates to a method and system for identifying large pores in offshore loose sandstone oil reservoirs, belonging to the field of petroleum development technology. Background Technology

[0002] Offshore oilfields often experience long-term, high-intensity combined injection and production, which frequently leads to the stripping and migration of reservoir microparticles during development. This results in the development of mainstream lines between wells, the formation of large channels in certain areas, uneven planar utilization, and increasingly prominent inter- and intra-layer conflicts. Profile control and flood control operations can effectively improve the vertical profile and expand the swept volume, making them an effective way to stabilize oil production and control water in high-yield, high-volume offshore oilfields. Currently, onshore oilfields have accumulated some mature experience and methods in profile control and flood control, but most of them rely on water absorption profile test data. Offshore oilfields are limited by platform conditions and economic requirements, resulting in relatively less water absorption profile test data. Furthermore, after separate injection, water absorption profile tests can only obtain the water absorption situation within a certain sand control zone, making it difficult to ascertain the development of large channels in each sand control zone or even smaller layers. Therefore, it is not advisable to directly apply onshore oilfield methods to offshore oilfields. Currently, methods for identifying large channels mainly include well logging data inversion, observation well coring data identification, inter-well tracer monitoring, and well test analysis. However, each method has limitations in field implementation, such as long construction cycles, high operating costs, and restrictions imposed by platform conditions. Summary of the Invention

[0003] To address the aforementioned problems, the purpose of this invention is to provide a method and system for identifying large pores in offshore loose sandstone reservoirs. This method can accurately identify large pores and dominant channels in offshore loose sandstone reservoirs, enabling targeted adjustments and remediation measures to be implemented for various dominant channels.

[0004] To achieve the above objectives, the present invention proposes the following technical solution: a method for identifying large-pore reservoirs in offshore loose sandstone oil reservoirs, comprising: collecting static data of production wells and injection wells within a target block, as well as dynamic production data over a period of time; calculating control volume and inter-well conductivity based on the static data and dynamic production data; calculating permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient based on the control volume and inter-well conductivity; performing weighted normalization on the permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient to obtain a comprehensive evaluation factor; determining whether the comprehensive evaluation factor is greater than a threshold, and if so, considering the loose sandstone oil reservoir as having large-pore reservoirs.

[0005] Furthermore, the static data includes well location, bottom hole pressure, porosity, initial permeability, water saturation, and perforation information; the dynamic production data includes daily fluid production, daily oil production, cumulative fluid production, cumulative oil production, and water cut.

[0006] Furthermore, the control volume V ij The calculation formula is:

[0007]

[0008] Among them, L ij h is the distance between well i and well j; ij φ is the average reservoir thickness between well i and well j. ij N represents the average reservoir porosity between wells i and j. W V represents the total number of water injection wells and oil production wells in the oilfield; F This represents the total pore volume of the reservoir.

[0009] Furthermore, the inter-well conductivity T ij The calculation formula is:

[0010]

[0011] Where α is the unit conversion factor; V represents the average reservoir permeability between well i and well j; ij φ represents the control volume between well i and well j. ij The average reservoir porosity between wells i and j; μ0 is the oil phase viscosity; L ij Let i be the distance between well i and well j.

[0012] Furthermore, the penetration rate K ii The calculation formula is:

[0013]

[0014] Where μ is the actual oilfield phase viscosity; T ij φ represents the inter-well conductivity between injection well i and production well j; φ represents the porosity of the selected perforated section of the injection well; l ij V is the distance between injection well i and production well j; ij The control volume between injection well i and production well j.

[0015] Furthermore, the Lorentz flux coefficient is calculated as follows: based on the inter-well conductivity T ij Calculate the cumulative seepage capacity and cumulative storage capacity, and plot the cumulative seepage capacity as the ordinate and the cumulative storage capacity as the abscissa to generate a line graph. Calculate the first area of ​​the graph formed by the line graph and y=x. Obtain the intersection points of the line graph and y=x except for the origin. Draw a horizontal line parallel to the X-axis through the intersection points. The horizontal line intersects the Y-axis at point D. The area of ​​the triangle formed by the Y-axis, the horizontal line, and y=x is the second area. Divide the first area by the second area to obtain the Lorentz crossflow coefficient.

[0016] Furthermore, the water injection efficiency is... i The calculation formula is:

[0017]

[0018] Among them, Q ij f is the water injection volume in the ij direction, n is the number of all corresponding splitting directions, and f is the injection volume in the ij direction. wji It represents the water content in the ij direction.

[0019] Furthermore, the water injection splitting coefficient λ ij The calculation formula is:

[0020]

[0021] Where NJ represents the number of directions in which the injection well splits into the production well.

[0022] Furthermore, the comprehensive evaluation factor M ij The calculation formula is:

[0023] M ij =K ij ·W1+L ij ·W2+M efi ·W3+λ ij ·W4

[0024] Among them, W1, W2, W3, and Q4 are all weighting coefficients, and K ij For penetration rate, L ij It is the Lorentz clogging coefficient, W efi For water injection efficiency, λ ij This is the water injection splitting coefficient.

[0025] This invention also discloses a large-pore identification system for offshore loose sandstone reservoirs, comprising: a data acquisition module for acquiring static data of production wells and injection wells within a target block, as well as dynamic production data over a period of time; a control volume and inter-well conductivity calculation module for calculating control volume and inter-well conductivity based on the static data and dynamic production data; a coefficient calculation module for calculating permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient based on the control volume and inter-well conductivity; a comprehensive evaluation factor calculation module for weighted normalization of the permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient to obtain a comprehensive evaluation factor; and a large-pore identification module for determining whether the comprehensive evaluation factor is greater than a threshold, and if so, considering the loose sandstone reservoir as having large pores.

[0026] This invention, by adopting the above technical solutions, has the following advantages: 1. This invention provides a method for identifying large channels in offshore loose sandstone reservoirs based on inter-well connectivity, which can accurately identify large channels and dominant passages in offshore loose sandstone reservoirs. This method is not only simple and feasible to operate, but also significantly reduces costs and is easy to promote and apply. 2. This invention directly utilizes static and production dynamic data for inter-well large channel identification, which is simple, convenient, and easy to implement. The calculation results are used for subsequent adjustment and treatment measures for large channels with different development levels, thereby improving the profile, expanding the swept volume, and increasing production. 3. This invention does not require additional on-site operations and testing, reducing construction costs and shortening the operation cycle, thus achieving the goal of cost reduction and efficiency improvement. In summary, this invention can be widely applied to the research on the identification and investigation of large channels in offshore loose sandstone reservoirs. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for identifying large pores in offshore loose sandstone reservoirs according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the calculation of the Lorentz crossflow coefficient in one embodiment of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for a better understanding of the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] To address the limitations of existing large-channel identification methods in offshore oilfields, which cannot be directly applied to onshore oilfields and suffer from long construction cycles, high operating costs, and platform constraints, this invention proposes a large-channel identification method for offshore loose sandstone reservoirs based on inter-well connectivity. This method comprehensively considers the static characteristic parameter "Lorentz channeling coefficient" and the dynamic characteristic parameters "water injection splitting coefficient" and "water injection efficiency" to investigate the development of large-channels and dominant channels between wells, enabling targeted adjustments and remediation measures for various types of large-channels. By combining static data such as permeability and Lorentz channeling coefficient with dynamic data such as water injection splitting coefficient and water injection efficiency, a comprehensive decision factor is calculated based on the weights of each indicator. This invention features simple parameter construction, low operational difficulty, and low testing costs, enabling accurate identification of large-channels and dominant channels in offshore loose sandstone reservoirs, facilitating targeted adjustments and remediation measures for various dominant channels. The following detailed description of the invention, with reference to the accompanying drawings and embodiments, illustrates the solution in detail.

[0031] Example 1

[0032] This embodiment discloses a method for identifying large pores in offshore loose sandstone oil reservoirs, such as... Figure 1 As shown, it includes:

[0033] S1 collects static data of production wells and injection wells within the target block, as well as dynamic production data over a period of time.

[0034] Static data includes well location, bottom hole pressure, porosity, initial permeability, water saturation, and perforation information; dynamic production data includes daily fluid production, daily oil production, cumulative fluid production, cumulative oil production, and water cut.

[0035] The daily fluid production, daily oil production, cumulative fluid production, cumulative oil production, and water cut of all production wells and injection wells within the target block are measured over a period of time. Data collected during a specific production period is analyzed to determine if there are any anomalies. If anomalies are found, the next step is to calculate the control volume and inter-well conductivity. If no anomalies are found, data collected during different time periods is selected again until anomalies are found.

[0036] S2 calculates the control volume and inter-well conductivity based on static data and production dynamic data;

[0037] Control volume V ij The calculation formula is:

[0038]

[0039] Among them, L ij h is the distance between well i and well j; ij φ is the average reservoir thickness between well i and well j. ij N represents the average reservoir porosity between wells i and j. W V represents the total number of water injection wells and oil production wells in the oilfield; F This represents the total pore volume of the reservoir.

[0040] Inter-well conductivity T ij The calculation formula is:

[0041]

[0042] Where α is the unit conversion factor; V represents the average reservoir permeability between well i and well j; ij φ represents the control volume between well i and well j. ij The average reservoir porosity between wells i and j; μ0 is the oil phase viscosity; L ij Let i be the distance between well i and well j.

[0043] S3 calculates permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient based on the control volume and inter-well conductivity; and obtains a comprehensive evaluation factor by weighting and normalizing the permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient.

[0044] Penetration rate K ij The calculation formula is:

[0045]

[0046] Where μ is the actual oilfield phase viscosity; T ij φ represents the inter-well conductivity between injection well i and production well j; φ represents the porosity of the selected perforated section of the injection well; l ij V is the distance between injection well i and production well j; ij The control volume between injection well i and production well j.

[0047] like Figure 2 As shown, the Lorentz flux coefficient is calculated as follows: based on the inter-well conductivity T ij Calculate the cumulative seepage capacity and cumulative storage capacity, where the cumulative seepage capacity is F. mj The calculation formula is:

[0048]

[0049] Where m is the index of the connected element, I is the total number of connected elements, and ω ij It is the connectivity coefficient.

[0050]

[0051] Cumulative storage capacity C mj The calculation formula is:

[0052]

[0053] in,

[0054]

[0055] Where, τ ij It is the time constant, C tij It is the overall compression coefficient.

[0056] Plotting cumulative seepage capacity on the ordinate and cumulative storage capacity on the abscissa generates a line graph. Figure 2 Given the broken line ABC, calculate the first area S of the figure formed by the broken line graph and the corresponding straight line y = x on the homogeneous base layer, which is the area of ​​triangle ABC. ABCObtain the intersection points of the line graph ABC and the corresponding straight line y = x in the homogeneous base layer, namely intersection points A and B. Intersection point A is the origin. Draw a horizontal line parallel to the x-axis through intersection point B. This horizontal line intersects the y-axis at point D. The area of ​​the triangle formed by the y-axis, the horizontal line, and y = x, i.e., triangle ABD, is the second area S. ABD , the first area S ABC Divide by the second area S ABD The Lorentz churn coefficient is obtained, and the formula for calculating the Lorentz churn coefficient is as follows:

[0057]

[0058] Water injection efficiency wef i The calculation formula is:

[0059]

[0060] Among them, Q ij It is the water injection volume in the ij direction, m 3 / d, where n is the number of all corresponding splitting directions, f wji It represents the water content in the ij direction.

[0061] Water injection splitting coefficient λ ij The calculation formula is:

[0062]

[0063] Where NJ represents the number of directions in which the injection well splits into the production well.

[0064] Comprehensive evaluation factor M ij The calculation formula is:

[0065] M ij =K ij ·W1+L ij ·W2+W efi ·W3+λ ij ·W4

[0066] Where W1, W2, W3, and W4 are all weighting coefficients, and K ij For penetration rate, L ij It is the Lorentz clogging coefficient, W efi For water injection efficiency, λ ij This is the water injection splitting coefficient.

[0067] S4 determines whether the comprehensive evaluation factor is greater than the threshold. If so, the loose sandstone reservoir is considered to be a large-pore reservoir.

[0068] Compared with existing technologies, the method for identifying large pores in offshore loose sandstone reservoirs provided in this embodiment has the following advantages:

[0069] 1. This invention provides a method for identifying large channels in offshore loose sandstone reservoirs based on well interconnection, which can accurately identify large channels and dominant passages in offshore loose sandstone reservoirs. This method is not only simple and feasible to operate, but also significantly reduces costs and is easy to promote and apply.

[0070] 2. This invention directly utilizes static and production dynamic data to identify large wellbore channels, which is simple, convenient, and easy to implement. The calculation results will guide the next step of adjustment and treatment measures for large wellbore channels with different development levels, thereby improving the profile, expanding the swept volume, and increasing production.

[0071] 3. This invention eliminates the need for additional on-site operations and testing, reducing construction costs and shortening the work cycle, thereby achieving cost reduction and efficiency improvement. In summary, this invention can be widely applied to the research of large-pore identification in offshore loose sandstone reservoirs.

[0072] Example 2

[0073] Based on the same inventive concept, this embodiment discloses a large-pore identification system for offshore loose sandstone oil reservoirs, including:

[0074] The data acquisition module is used to collect static data of production wells and injection wells within the target block, as well as dynamic production data over a period of time.

[0075] The control volume and inter-well conductivity calculation module is used to calculate the control volume and inter-well conductivity based on static data and production dynamic data.

[0076] The coefficient calculation module is used to calculate permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient based on the control volume and inter-well conductivity.

[0077] The comprehensive evaluation factor calculation module is used to calculate the comprehensive evaluation factor by weighting and normalizing the permeability, Lorentz crossflow coefficient, water injection efficiency and water injection splitting coefficient.

[0078] The large pore identification module is used to determine whether the comprehensive evaluation factor is greater than the threshold. If so, the loose sandstone reservoir is considered to be a large pore.

[0079] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0080] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0081] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0082] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A method for identifying large pores in offshore loose sandstone oil reservoirs, characterized in that, include: Collect static data of production wells and injection wells within the target block, as well as dynamic production data over a period of time; The daily fluid production, daily oil production, cumulative fluid production, cumulative oil production, and water cut of all production wells and injection wells in the target block are measured over a period of time. Data collected during a specific production period is selected for analysis to determine if there are any outliers in the data collected during that period. If there are outliers, the next step is taken. If there are no outliers, data collected during different time periods is selected again until an outlier is found. The control volume and inter-well conductivity are calculated based on the static data and production dynamic data. Based on the control volume and inter-well conductivity, calculate the permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient; The permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient are weighted and normalized to obtain a comprehensive evaluation factor. Determine whether the comprehensive evaluation factor is greater than the threshold; if so, the loose sandstone reservoir is considered to be a large-pore reservoir. The comprehensive evaluation factor M ij The calculation formula is: M ij =K ij ·W1+L ij ·W2+W efi ·W3+λ ij ·W4 Where W1, W2, W3, and W4 are all weighting coefficients, and K ij For penetration rate, L ij It is the Lorentz clogging coefficient, W efi For water injection efficiency, λ ij This is the water injection splitting coefficient.

2. The method for identifying large pores in offshore loose sandstone reservoirs as described in claim 1, characterized in that, The static data includes well location, bottom hole pressure, porosity, initial permeability, water saturation, and perforation information; the dynamic production data includes daily fluid production, daily oil production, cumulative fluid production, cumulative oil production, and water cut.

3. The method for identifying large pores in offshore loose sandstone reservoirs as described in claim 1, characterized in that, The control volume V ij The calculation formula is: Among them, L ij h is the distance between well i and well j; ij φ is the average reservoir thickness between well i and well j. ij N represents the average reservoir porosity between wells i and j. W V represents the total number of water injection wells and oil production wells in the oilfield; F This represents the total pore volume of the reservoir.

4. The method for identifying large pores in offshore loose sandstone reservoirs as described in claim 3, characterized in that, The inter-well conductivity T ij The calculation formula is: Where α is the unit conversion factor; V represents the average reservoir permeability between well i and well j; ij φ represents the control volume between well i and well j. ij The average reservoir porosity between wells i and j; μ0 is the oil phase viscosity; L ij Let i be the distance between well i and well j.

5. The method for identifying large pores in offshore loose sandstone reservoirs as described in claim 3, characterized in that, The permeability K ij The calculation formula is: Where μ is the actual oilfield phase viscosity; T ij φ represents the inter-well conductivity between injection well i and production well j; φ represents the porosity of the selected perforated section of the injection well; l ij V is the distance between injection well i and production well j; ij The control volume between injection well i and production well j.

6. The method for identifying large pores in offshore loose sandstone reservoirs as described in claim 3, characterized in that, The Lorentz flux coefficient is calculated as follows: based on the inter-well conductivity T ij Calculate the cumulative seepage capacity and cumulative storage capacity, and plot the cumulative seepage capacity as the ordinate and the cumulative storage capacity as the abscissa to generate a line graph. Calculate the first area of ​​the graph formed by the line graph and y=x. Obtain the intersection points of the line graph and y=x except for the origin. Draw a horizontal line parallel to the X-axis through the intersection points. The horizontal line intersects the Y-axis at point D. The area of ​​the triangle formed by the Y-axis, the horizontal line, and y=x is the second area. Divide the first area by the second area to obtain the Lorentz crossflow coefficient.

7. The method for identifying large pores in offshore loose sandstone reservoirs as described in claim 3, characterized in that, The water injection efficiency wef i The calculation formula is: Among them, Q ij f is the water injection volume in the ij direction, n is the number of all corresponding splitting directions, and f is the injection volume in the ij direction. wji It represents the water content in the ij direction.

8. The method for identifying large pores in offshore loose sandstone reservoirs as described in claim 7, characterized in that, The water injection splitting coefficient λ ij The calculation formula is: Where NJ represents the number of directions in which the injection well splits into the production well.

9. A system for identifying large pores in offshore loose sandstone oil reservoirs, characterized in that, include: The data acquisition module is used to collect static data of production wells and injection wells within the target block, as well as dynamic production data over a period of time. The daily fluid production, daily oil production, cumulative fluid production, cumulative oil production, and water cut of all production wells and injection wells in the target block are measured over a period of time. Data collected during a specific production period is selected for analysis to determine if there are any outliers in the data collected during that period. If there are outliers, the next step is taken. If there are no outliers, data collected during different time periods is selected again until an outlier is found. A control volume and inter-well conductivity calculation module is used to calculate the control volume and inter-well conductivity based on the static data and production dynamic data. The coefficient calculation module is used to calculate the permeability, Lorentz crossflow coefficient, water injection efficiency, and water injection splitting coefficient based on the control volume and inter-well conductivity. The comprehensive evaluation factor calculation module is used to perform weighted normalization on the permeability, Lorentz crossflow coefficient, water injection efficiency and water injection splitting coefficient to obtain the comprehensive evaluation factor. The large-pore identification module is used to determine whether the comprehensive evaluation factor is greater than the threshold. If so, the loose sandstone reservoir is considered to be a large-pore reservoir. The comprehensive evaluation factor M ij The calculation formula is: M ij =K ij ·W1+L ij ·W2+W efi ·W3+λ ij ·W4 Where W1, W2, W3, and W4 are all weighting coefficients, and K ij For penetration rate, L ij It is the Lorentz clogging coefficient, W efi For water injection efficiency, λ ij This is the water injection splitting coefficient.

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