A method for identifying high water consumption layer zone of an oil reservoir based on limit displacement

Abstract

This invention belongs to the field of petroleum development technology and relates to a method for identifying high water-consuming zones in oil reservoirs based on extreme displacement. The method includes the following steps: obtaining the full-process curve of relative permeability; obtaining the water saturation field and liquid phase flow field; determining the water saturation index and liquid phase flow rate index; and identifying the high water-consuming zones in the oil reservoir. This invention comprehensively considers the oil-water flow characteristics of high water-consuming zones, the actual geological conditions of the oil reservoir, and potential interference factors during development. For the first time, it proposes using both water saturation and liquid phase flow rate as dual indicators to identify high water-consuming zones in oil reservoirs, avoiding misjudgments and providing an accurate basis for actual development adjustments in reservoirs with extremely high water cut.

Description

Technical Field

[0001] This invention belongs to the field of petroleum development technology and relates to a method for identifying high water-consuming zones in oil reservoirs based on extreme displacement. Background Technology

[0002] Water injection is currently the main development method for oil reservoirs both domestically and internationally. After years of development, most oil reservoirs have entered the high water-cut or ultra-high water-cut stage. Compared with the medium and low water-cut stage, the high water-cut stage has lower single-well oil production, higher water cut, and scattered remaining oil distribution, resulting in poor development benefits from continuous water injection.

[0003] In actual oil reservoirs, due to reservoir heterogeneity, injected water will surge into high-permeability zones, causing uneven displacement. As water injection development progresses, dominant channels for injected water gradually form in the formation, further increasing the degree of displacement imbalance. Entering the ultra-high water-cut stage, most of the injected water flows directly into production wells along fixed channels, resulting in an inefficient and ineffective cycle of water injection at the injection end and high water cut at the production end—the formation of a high water-consuming zone. The formation of this high water-consuming zone significantly restricts the efficient development of the reservoir. Therefore, accurately identifying and describing the high water-consuming zone and effectively managing it are crucial for improving the development effect of ultra-high water-cut oil reservoirs and increasing oil recovery.

[0004] The applicant previously disclosed a method for identifying high water-consuming channels in ultra-high water-cut reservoirs in application CN109441437A. This method includes: drawing a permeability gradient distribution map and a cumulative production and injection map of oil and water wells; determining, based on the cumulative production and injection map, that a high water-consuming zone exists between oil wells and injection wells where the ratio of cumulative water production to cumulative water injection is greater than a set value d; and using the production and water absorption profile data of oil wells and injection wells with high water-consuming zones, identifying layers where the ratio of water production to total water production of the oil well is greater than a set value e and the ratio of water absorption to total water absorption of the injection well is greater than a set value f. The portion of this layer located between the oil well and the injection well is considered a high water-consuming channel. This method is a qualitative identification of high water-consuming zones based on actual reservoir dynamic data and monitoring data, enabling rapid assessment of high water consumption in the reservoir and allowing for adjustments to avoid high water-consuming zones. However, it is difficult to characterize the internal oil-water flow relationship and the remaining oil content within the reservoir, thus providing insufficient support for future development potential.

[0005] Chinese patent application CN111911135A discloses a method for dynamically describing high water-consuming zones in water-drive reservoirs. The method includes the following steps: Step 1, collecting and organizing geological and development data of the target reservoir, and constructing a streamline simulation model of the target reservoir using a streamline simulator; Step 2, calling the streamline simulator to conduct streamline numerical simulation of water-drive development of the target reservoir, and obtaining the streamline distribution results of the target reservoir at different times; Step 3, extracting the characteristic parameter values ​​of each streamline at different times, and calculating the pseudo-water cut of each streamline; Step 4, identifying the location and range of streamlines with a pseudo-water cut >98% at different times, and outputting the dynamic description results of high water-consuming zones in the target reservoir. This method is applicable to situations where the flow lines of injection and production wells are fixed and long-term water injection scouring occurs. However, the actual reservoir development process is complex. If the reservoir has edge and bottom water intrusion, or if the reservoir has undergone measures such as adjustment of the injection and production well network, adjustment of working system, or development by chemical agents, using the pseudo-water cut as an identification indicator is very likely to cause misjudgment of high water-consuming zones. It is difficult to cope with the complex situation in the actual reservoir development process in the later stage of ultra-high water cut.

[0006] Chinese patent application CN109209308A discloses a waterflooding development method for high water-cut reservoirs. This method includes the following steps: 1) identifying high water-consuming channels in ultra-high water-cut reservoirs where the waterflooding characteristic curve shows an upward inflection point; 2) avoiding the high water-consuming channels identified in step 1) during waterflooding development by adjusting the well network, oil-to-injection, and injection-to-oil methods. This method qualitatively identifies high water-consuming zones based on the inflection point of the waterflooding characteristic curve and avoids them by adjusting the injection-production well network and operating procedures. It is a method of formulating adjustment measures based on the current situation, but it cannot clearly define the historical evolution and current status of high water-consuming zones and remaining oil in the reservoir, thus its development potential is unclear.

[0007] In summary, existing technologies still suffer from problems such as misjudgment and incorrect identification of high water-consuming zones, and are unable to provide accurate basis for actual development adjustments of reservoirs in the ultra-high water-cut period. Summary of the Invention

[0008] The main objective of this invention is to provide a method for identifying high water-consuming zones in water-driven reservoirs based on extreme displacement. This method integrates the oil-water flow characteristics of high water-consuming zones, the actual geological conditions of the reservoir, and possible interference factors during development. For the first time, it proposes to identify high water-consuming zones in reservoirs using both water saturation and liquid phase velocity as dual indicators, avoiding misjudgment or incorrect identification of high water-consuming zones, and providing an accurate basis for actual development adjustments in reservoirs with ultra-high water cut.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] This invention provides a method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement, comprising the following steps:

[0011] Step 1. Obtain the full-process curve of relative permeation;

[0012] Step 2. Obtain the water saturation field and liquid phase flow field;

[0013] Step 3. Determine the water saturation index and liquid phase flow rate index;

[0014] Step 4. Identify the high water consumption zone of the reservoir.

[0015] Furthermore, in step 1, the residual oil saturation is predicted using the limit displacement model, and the end-point calibration method is used to obtain the full-process curve of oil-water interpenetration based on the limit displacement conditions.

[0016] Furthermore, step 1 specifically includes the following steps:

[0017] Step 101: Predict the residual oil saturation using the following limiting displacement model:

[0018] (1)

[0019] In the formula, f w —Moisture content, dimensionless; S w —Current water saturation, dimensionless; S wi —Bound water saturation, dimensionless; S orw —Water saturation corresponding to residual oil saturation, dimensionless; μ R —Oil-water viscosity ratio, dimensionless; m, n —fitting coefficients;

[0020] Step 102: After obtaining the residual oil saturation, the endpoint calibration method is used to calculate the full-process curve of relative permeation by fitting the relative permeation data. The calculation model used is as follows:

[0021] Water phase interpenetration: (2)

[0022] Oil phase interpenetration: (3)

[0023] In the formula, K rw —Water phase permeability value, dimensionless; K rw(Swmax) —Maximum water phase interperfusion, dimensionless; S w —Current water saturation, dimensionless; S wi —Bound water saturation, dimensionless; S or —Limiting residual oil saturation, dimensionless; C w —Water phase interpermeability index, dimensionless; K ro —Oil phase permeability value, dimensionless; μ o —Oil phase viscosity, mPa·s; μ w —Viscosity of aqueous phase, mPa·s; fw —Moisture content, dimensionless.

[0024] Furthermore, the specific method for obtaining the water saturation field and liquid phase flow field in step 2 is as follows:

[0025] Step 201. Obtain geological and development data based on mine production dynamics and indoor testing, and establish a reservoir numerical model;

[0026] Step 202. Based on the obtained full-process curve of relative permeation, a numerical simulator is used to fit the reservoir history to obtain the water saturation field and liquid flow field at different times in the block.

[0027] Furthermore, the geological and development data includes reservoir structure, stratification, well location, well trajectory, logging, sedimentary facies, core wells, physical property testing, fluid testing, single-well production data, and dynamic monitoring data.

[0028] Furthermore, the accuracy of reservoir history fitting must meet the following requirements: the water cut fitting error at the end of the block's history is less than 2%, the relative error of cumulative oil production fitting is less than 1%, and the fitting rate of a single well is greater than 85%.

[0029] Furthermore, in step 3, the high water consumption zone identification indicators include the water saturation identification indicator and the liquid phase flow rate identification indicator of the high water consumption zone.

[0030] Furthermore, based on the full-process curve of relative permeation, the water saturation corresponding to a water content of 99.5% is selected as the water saturation identification index for high water consumption zones; based on the liquid phase flow field, the upper limit of the flow rate corresponding to a distribution probability of 0% or greater is selected as the liquid phase flow rate identification index for high water consumption zones.

[0031] Furthermore, in step 4, the method for identifying high water-consuming zones in the reservoir is as follows: the numerical simulation grid of the reservoir is judged according to the indicators in step 3. When the water saturation value and liquid phase flow rate value in the grid are both greater than the indicator parameters determined in step 3, the grid is judged to be a high water-consuming grid; if one or both do not meet the requirements, it is judged to be a non-high water-consuming grid.

[0032] Furthermore, by analyzing the simulated grids at different times, the contiguous areas of the high water-consuming grids represent the identification results of the high water-consuming zones in the reservoir at different times.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] The method of this invention takes into account the differences in the flow patterns of oil and water phases in reservoirs with ultra-high water cut, and the identification process can be implemented in both black oil simulators and streamline simulators.

[0035] This invention is based on reservoir engineering and seepage mechanics theory, and fully considers the special characteristics of oil-water flow differences in high water-consuming zones during ultra-high water-cut reservoirs. By using the water saturation field and liquid phase flow field as the basis for identifying high water-consuming zones, it can achieve accurate identification of these zones and avoid misjudgments in various special cases, such as natural edge and bottom water, the incomplete formation of high water-consuming zones in the early stages of displacement, and changes in the internal seepage field of the reservoir caused by changes in operating conditions or adjustment measures.

[0036] The method of this invention has the advantages of easy data acquisition, simple identification process, and reliable identification results. Moreover, the operation process is easy to learn and easy to promote. With the help of reservoir numerical simulation software, it can reproduce the entire process of dynamic evolution of high water-consuming zones during reservoir development, which has important guiding significance and technical support for the development and adjustment of reservoirs in the ultra-high water-cut period. Attached Figure Description

[0037] 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 improper limitation of the invention.

[0038] Figure 1 This is a flowchart illustrating the implementation of the method for identifying high water-consuming reservoir zones based on extreme displacement as described in Embodiment 1 of the present invention.

[0039] Figure 2 This is a graph showing the entire process of aqueous phase flow separation as described in Embodiment 1 of the present invention.

[0040] Figure 3 This is a graph showing the entire process of oil-water phase permeation as described in Embodiment 1 of the present invention;

[0041] Figure 4 This is a water saturation field diagram of the actual oil reservoir described in Embodiment 1 of the present invention;

[0042] Figure 5 This is a diagram of the actual reservoir liquid flow field described in Embodiment 1 of the present invention;

[0043] Figure 6 This is a statistical diagram of the probability distribution of liquid phase flow rate in an actual reservoir in Example 1 of the present invention;

[0044] Figure 7 The following are the results of the identification of high water-consuming zones in Embodiment 1 of the present invention: A is the distribution map of high water-consuming zones at time T1; B is the distribution map of high water-consuming zones at time T2 after injection and production adjustment. Detailed Implementation

[0045] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0046] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0047] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0048] Example 1

[0049] like Figure 1 As shown, the method for identifying high water-consuming zones in oil reservoirs based on extreme displacement includes the following steps:

[0050] Step 1, Obtain the full-process curve of relative permeation:

[0051] Specifically, the following steps are included:

[0052] Step 101: Based on reservoir engineering theory, calculate the limiting residual oil saturation using existing oil-water two-phase laboratory test data. The calculation model used in this embodiment is as follows:

[0053] (1)

[0054] In the formula, f w —Moisture content, dimensionless; S w —Current water saturation, dimensionless; S wi —Bound water saturation, dimensionless; S orw —Water saturation corresponding to residual oil saturation, dimensionless; μ R —Oil-water viscosity ratio, dimensionless; m, n —fitting coefficients.

[0055] The unknowns in Equation 1 include the fitting coefficients m, n, and S. orw By fitting the test results of water phase fraction flow and water saturation in the relative permeability test report, m, n, and S can be obtained. orw The value is used to obtain the residual oil saturation under the theoretical limit of displacement, such as Figure 2 As shown.

[0056] Step 102: After obtaining the residual oil saturation, the endpoint calibration method is used to calculate the full-process curve of relative permeability by fitting existing relative permeability data. The calculation model in this embodiment is as follows:

[0057] Water phase interpenetration: (2)

[0058] Oil phase interpenetration: (3)

[0059] In the formula, K rw —Water phase permeability value, dimensionless; K rw(Swmax) —Maximum water phase interperfusion, dimensionless; S w —Current water saturation, dimensionless; S wi —Bound water saturation, dimensionless; S or —Limiting residual oil saturation, dimensionless; C w —Water phase interpermeability index, dimensionless; K ro —Oil phase permeability value, dimensionless; μ o —Oil phase viscosity, mPa·s; μ w —Viscosity of aqueous phase, mPa·s; f w —Moisture content, dimensionless.

[0060] The unknowns in Equation 2 include K rw(Sorw) and C w By fitting existing test report data, and then using Equation 3 to calculate oil phase reperfusion, the final reperfusion curve for the entire process is obtained, as shown below. Figure 3 As shown.

[0061] Step 2: Obtain the water saturation field and liquid phase flow field.

[0062] This embodiment uses the E100 black oil simulator to construct a reservoir numerical model. Under the premise that the historical fitting meets the requirements: the water cut fitting error at the end of the block's history is less than 2%, the relative error of the cumulative oil production fitting is less than 1%, and the single-well fitting rate is greater than 85%. The water cut saturation field of the reservoir at different times is obtained, such as... Figure 4 As shown; liquid phase flow field, such as Figure 5 As shown.

[0063] Step 3, determine the identification indicators for high water consumption zones:

[0064] Step 301, according to the appendix Figure 2 The water saturation level at a moisture content of 99.5% is obtained as the water saturation identification index. In this embodiment, the water saturation level corresponding to a moisture content of 99.5% is 0.58, therefore the water saturation identification index is 0.58. Figure 2 As shown, when the water saturation value of the simulated grid is less than this parameter, it will not be identified as a high water-consuming zone.

[0065] Step 302: Statistically analyze the distribution range of the liquid phase flow field. Select the upper limit value of the liquid phase flow rate with a distribution probability greater than 80% starting from 0 as the identification index for the liquid phase flow rate in the high water consumption zone. In this embodiment, the upper limit value of the flow rate corresponding to a distribution probability greater than 80% for the liquid phase flow rate range is 1.8. Figure 6 As shown, the liquid phase flow rate identification index for high water consumption zones is therefore 1.8. When the grid liquid phase flow rate value is less than this index parameter, it will not be identified as a high water consumption zone.

[0066] Step 4: Identify high water-consuming zones in the reservoir.

[0067] The reservoir numerical simulation grid is evaluated according to the criteria in step 3. The evaluation statements and parameters in this embodiment are as follows:

[0068] HWC=if(S w >0.58 & Q t >1.8,1,0) (4)

[0069] In this statement, HWC characterizes whether the grid is a high water consumption grid, S w Q represents the water saturation level of the grid. t This represents the liquid phase flow rate in the grid.

[0070] If HWC=1, it is a high water-consuming layer; if HWC=0, it is a non-high water-consuming layer. When both the water saturation value and the liquid flow rate value within the grid are greater than the specified parameter, the grid is determined to be a high water-consuming grid, and HWC=1. If one or both parameters are not met, it is determined to be a non-high water-consuming grid, and HWC=0.

[0071] By analyzing simulated grids at different times, the contiguous areas with HWC=1 represent the high water-consuming zones identified in the reservoir at different time points. Figure 7 As shown in the figure. This identification result can effectively avoid misjudgment caused by edge and bottom water, and at the same time, based on the production dynamics and measures adjustment at different times, it can effectively identify the dynamic evolution of high water consumption zones, avoid misjudgment caused by measures adjustment, and ensure the reliability of the identification result.

[0072] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement, characterized in that, It includes the following steps: Step 1. Obtain the full process curve of oil-water phase permeation; predict the residual oil saturation using the limit displacement model, and obtain the full process curve of oil-water phase permeation based on the limit displacement conditions using the endpoint calibration method; Step 1 specifically includes the following steps: Step 101: Predict the residual oil saturation using the following limiting displacement model: （1） In the formula f w —Moisture content, dimensionless; S w —Current water saturation, dimensionless; S wi —Bound water saturation, dimensionless; S orw —Water saturation corresponding to residual oil saturation, dimensionless; μ R —Oil-water viscosity ratio, dimensionless; m, n —fitting coefficients; Step 102: After obtaining the residual oil saturation, the endpoint calibration method is used to calculate the full-process curve of relative permeation by fitting the relative permeation data. The calculation model used is as follows: Water phase interpenetration: (2) Oil phase interpenetration: (3) In the formula, K rw —Water phase permeability value, dimensionless; K rw(Swmax) —Maximum water phase interperfusion, dimensionless; S w —Current water saturation, dimensionless; S wi —Bound water saturation, dimensionless; S or —Limiting residual oil saturation, dimensionless; C w —Water phase interpermeability index, dimensionless; K ro —Oil phase permeability value, dimensionless; μ o —Oil phase viscosity, mPa·s; μ w —Viscosity of aqueous phase, mPa·s; f w —Moisture content, dimensionless; Step 2. Obtain the water saturation field and liquid phase flow field; The specific method is as follows: Step 201. Obtain geological and development data based on mine production dynamics and indoor testing, and establish a reservoir numerical model; Step 202. Based on the obtained full-process curve of relative permeability, a numerical simulator is used to fit the reservoir history to obtain the water saturation field and liquid flow field at different times in the block. Step 3. Determine the water saturation index and liquid phase flow rate index; Step 4. Identify the high water consumption zone of the reservoir.

2. The method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement according to claim 1, characterized in that, The geological and development data include reservoir structure, stratification, well location, well trajectory, logging, sedimentary facies, core wells, physical property testing, fluid testing, single-well production data, and dynamic monitoring data.

3. The method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement according to claim 1, characterized in that, The accuracy of reservoir history fitting must meet the following requirements: the water cut fitting error at the end of the block history is less than 2%, the relative error of cumulative oil production fitting is less than 1%, and the single well fitting rate is greater than 85%.

4. The method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement according to claim 1, characterized in that, In step 3, the high water consumption zone identification indicators include the water saturation identification indicator and the liquid phase flow rate identification indicator.

5. The method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement according to claim 4, characterized in that, Based on the full-process curve of relative permeation, the water saturation corresponding to a water cut of 99.5% is selected as the water saturation identification index for high water consumption zones; based on the liquid phase flow field, the upper limit of the flow rate corresponding to an interval distribution probability of 0% or greater is selected as the liquid phase flow rate identification index for high water consumption zones.

6. The method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement according to claim 1, characterized in that, In step 4, the method for identifying high water-consuming zones in the reservoir is as follows: the numerical simulation grid of the reservoir is judged according to the indicators in step 3. When the water saturation value and liquid phase flow rate value in the grid are both greater than the indicator parameters determined in step 3, the grid is judged to be a high water-consuming grid; if one or both do not meet the requirements, it is judged to be a non-high water-consuming grid.

7. The method for identifying high water-consuming zones in water-drive reservoirs based on extreme displacement according to claim 6, characterized in that, By analyzing simulated grids at different times, the contiguous areas of high water-consuming grids represent the identification results of high water-consuming zones in the reservoir at different times.

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