A method for predicting and regulating the effect of acidizing and stimulation of low-permeability reservoir oil wells

Abstract

The application discloses a low-permeability reservoir oil well acidification stimulation effect prediction and regulation method, which comprises the following steps: S1, using a core to carry out an acid rock dissolution experiment to obtain a dissolution rate η of different acid liquid systems on reservoir rocks; S2, calculating an average original porosity and an average porosity of a reservoir in a to-be-acidized oilfield block; S3, calculating an effective average acidification radius ref of each block when considering non-uniform acid distribution caused by reservoir heterogeneity; S4, calculating an acidification stimulation multiple, drawing a three-dimensional model chart of oilfield different block oil well acidification stimulation effect prediction and regulation according to the dissolution rate η, the effective average acidification radius ref and the acidification stimulation multiple; and S5, using the three-dimensional model chart and combining the dissolution rate of different acid liquid systems on reservoir rocks obtained in the step S1 to obtain a stimulation effect comparison graph of different acid liquid systems on different blocks, and quickly identifying an oilfield acidification favorable block and recommending an acid liquid system. The application can realize efficient optimization of an acid liquid system, optimization of an acidification process and quick identification of an oilfield acidification favorable block.

Description

Technical Field

[0001] This invention relates to the field of low-permeability oilfield reservoir stimulation and well completion technology, specifically to a method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells. Background Technology

[0002] Deep matrix acidizing is a key technology for reservoir stimulation and well production enhancement in low-permeability sandstone oil reservoirs, and it holds immense potential for economical and efficient exploitation in offshore low-permeability oilfields where platform space is limited and construction safety risks are high. The key to efficient production enhancement through matrix acidizing lies in two aspects: first, selecting an acid system with a high dissolution rate compatible with the reservoir; and second, increasing the effective acidizing distance and achieving uniform acid distribution as much as possible. However, the combined influence of factors such as reservoir rock properties, reservoir heterogeneity, fluid properties, and clay mineral content in different blocks and oil groups within the oilfield makes the selection of acid systems and the evaluation of the applicability of acidizing processes extremely difficult. Field practice shows that even when using the same acid system and the same acidizing process, the production enhancement effects of wells can vary significantly across different oilfield areas within the same oilfield. Therefore, a method for rapidly, economically, and reliably predicting and controlling the production enhancement effects of acidizing in low-permeability reservoirs is crucial for selecting the optimal acid system, optimizing construction techniques, and quickly identifying favorable acidizing blocks in the oilfield.

[0003] Currently, the main method used is to indirectly evaluate the production enhancement effect of matrix acidizing in low-permeability sandstone reservoirs and to select the optimal acid solution by obtaining the permeability improvement ratio before and after acidizing through laboratory experiments using acid core flow. However, this method requires obtaining a large number of core samples from oil wells, resulting in high costs. Acid core flow experiments are also prone to sample damage, have low reliability in predicting acidizing effects, and are complex and time-consuming. Numerical simulation can also predict the acidizing effect of oil wells, but this method is greatly affected by human factors in parameter settings, and there are often significant differences between the theoretical model and the actual physical processes of reservoir acidizing stimulation, leading to large discrepancies between the predicted results and the actual situation. Therefore, existing methods are difficult to quickly, economically, and reliably predict and control the production enhancement effect of oil well acidizing, and cannot be adapted to the efficient selection of acid solution systems, the optimization of acidizing processes, and the rapid identification of favorable acidizing blocks in low-permeability oilfields. Summary of the Invention

[0004] This invention provides a method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells. It solves the problems of existing experiments based on acid core flow laboratory experiments to evaluate the acidizing effect of oil wells, which are complex, costly, inefficient, and unreliable. It can achieve efficient optimization of acid system, optimization of acidizing process, and rapid identification of favorable blocks for acidizing in oil fields.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells, comprising the following steps:

[0006] S1: Select the core of the reservoir in the oilfield block to be acidized, and use the core to carry out acid rock dissolution experiments to obtain the dissolution rate η of the reservoir rock by different acid systems;

[0007] S2: Calculate the average original porosity φ0 and the average porosity φ greater than the average original porosity φ0 in the reservoir of the oilfield block to be acidized. h ;

[0008] S3: Based on the average original porosity φ0 and average porosity φ obtained in step S2 h Calculate the effective average acidification radius r of the acid solution in each block when considering the non-uniform acid distribution caused by reservoir heterogeneity. ef ;

[0009] S4: Calculate the acidification yield increase ratio based on the dissolution rate η and the effective average acidification radius r. ef And a three-dimensional model of the acidizing production increase ratio for predicting and controlling the acidizing production increase effect of oil wells in different blocks of the oilfield;

[0010] S5: Using the 3D model and the dissolution rate η of different acid systems on reservoir rocks obtained in step S1, a comparison chart of the production enhancement effects of different acid systems on different blocks is obtained, which can quickly identify oilfield acidification favorable blocks and recommend acid systems.

[0011] Preferably, in step S2, the original porosity data distribution of the reservoir in the oilfield block to be acidized is obtained, and then the average original porosity φ0 and average porosity φ are calculated according to the following formula. h

[0012]

[0013]

[0014] Where, a is the total number of porosity data points, in integer form; b is the total number of porosity data points greater than the average original porosity φ0, in integer form; i = 1, 2, ..., a, in integer form; j = 1, 2, ..., b, in integer form; φ i φ j These are the original porosity data points, in dimensionless units.

[0015] Preferably, obtaining the original porosity data distribution of the reservoir in the oilfield block to be acidized includes at least the following two methods: obtaining the reservoir rock porosity at each depth through well logging; and taking core samples at different well depths and then testing the porosity.

[0016] Preferably, in step S3, the effective average acidification radius r ef The calculation formula is as follows:

[0017] r ef =refd (φ h / φ0) 5

[0018] Where, r efd The average radius of action of the acid solution is defined in meters.

[0019] Preferably, in step S4, the formula for calculating the acidification yield increase ratio is as follows:

[0020]

[0021] In the formula, J0 and J are the oil production indices before and after acidizing, respectively, in m3 / d·MPa-1; re is the oil supply edge radius of the oil well, in m; rw is the wellbore radius, in m; and η is the acid dissolution rate of the rock, in dimensionless units.

[0022] Preferably, in step S4, the x-axis is the dissolution rate η and the effective average acidification radius r is... ef A three-dimensional model of the prediction and control of the acidizing effect on oil wells in different blocks of the oilfield is plotted with the Y-axis as the Y-axis and the acidizing production increase ratio as the Z-axis.

[0023] Preferably, in step S5, given the known dissolution rate and designed acidizing radius, if the value corresponding to the z-axis is higher than the minimum acidizing production increase ratio required by the oilfield company, then... J Therefore, this area is a favorable block for oilfield acidification in terms of this acid system.

[0024] Preferably, in step S5, if the production increase ratio corresponding to the acid solution's dissolution rate η of the target reservoir and the average acidification radius of the target reservoir is greater than the minimum production increase ratio, then the acid solution system is a recommended acid solution system for the target reservoir.

[0025] Preferably, in step S1, acid rock dissolution experiments are conducted according to "QSYXJ0040-2001-Evaluation Method for Performance of Acidizing Fluids for Oilfields".

[0026] Preferably, the method further includes step S6: obtaining the minimum acidification production increase ratio requirement value R for the oilfield. J For step S5, where the acidification yield increase ratio is less than the minimum acidification yield increase ratio requirement value R J The block is used to obtain the minimum acidification yield increase ratio requirement R under different acid systems using the 3D model drawing in step S4. J The design of the average minimum acidification radius r of the acid solution efdm

[0027] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention overcomes the limitations of existing experiments based on acid core flow laboratory experiments to evaluate the acidizing effect of oil wells, which are complex, costly, inefficient, and unreliable, and the large discrepancies between numerical simulation predictions of the acidizing effect and actual conditions. This invention calculates the production increase ratio of oil well acidizing based on the acid dissolution rate of rock and rock porosity parameters, and draws a prediction and control chart of the production increase effect of acidizing in low-permeability reservoir oil wells. Through the experimental data of the acid dissolution rate of rock, it is possible to quickly and economically achieve efficient optimization of acid systems in low-permeability oilfields, optimize acidizing processes, and identify favorable blocks for acidizing in oilfields, with high reliability. Attached Figure Description

[0028] Figure 1 This is a flowchart of the method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells according to the present invention;

[0029] Figure 2 These are the original porosity data of the reservoir in the oilfield block to be acidized;

[0030] Figure 3 This is a chart showing the prediction and control effects of acidizing on oil wells in Block L1.

[0031] Figure 4 This is a chart showing the prediction and control effects of acidizing on oil wells in Block L2.

[0032] Figure 5 This is a chart showing the prediction and control effects of acidizing on oil wells in Block L3.

[0033] Figure 6 This is a comparison chart showing the production increase effects of different acid solutions on different blocks. Detailed Implementation

[0034] The accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0035] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "long," and "short" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0036] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings:

[0037] Example 1

[0038] like Figure 1 As shown, a method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells includes the following steps:

[0039] S1: Select the core of the reservoir in the oilfield block to be acidized, and use the core to carry out acid rock dissolution experiments to obtain the dissolution rate η of the reservoir rock by different acid systems;

[0040] S2: Calculate the average original porosity φ0 and the average porosity φ greater than the average original porosity φ0 in the reservoir of the oilfield block to be acidized. h ;

[0041] S3: Based on the average original porosity φ0 and average porosity φ obtained in step S2 h Calculate the effective average acidification radius r of the acid solution in each block when considering the non-uniform acid distribution caused by reservoir heterogeneity. ef ;

[0042] S4: Calculate the acidification yield increase ratio based on the dissolution rate η and the effective average acidification radius r. ef And a three-dimensional model of the acidizing production increase ratio for predicting and controlling the acidizing production increase effect of oil wells in different blocks of the oilfield;

[0043] S5: Using the 3D model and the dissolution rate η of different acid systems on reservoir rocks obtained in step S1, a comparison chart of the production enhancement effects of different acid systems on different blocks is obtained, which can quickly identify oilfield acidification favorable blocks and recommend acid systems.

[0044] Example 2

[0045] The difference from Example 1 is that, based on Example 1, step S6 is also included. More specifically, a method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells includes the following steps:

[0046] S1: Select the core of the reservoir in the oilfield block to be acidized, and use the core to carry out acid rock dissolution experiments to obtain the dissolution rate η of the reservoir rock by different acid systems;

[0047] S2: Calculate the average original porosity φ0 and the average porosity φ greater than the average original porosity φ0 in the reservoir of the oilfield block to be acidized. h ;

[0048] S3: Based on the average original porosity φ0 and average porosity φ obtained in step S2 h Calculate the effective average acidification radius r of the acid solution in each block when considering the non-uniform acid distribution caused by reservoir heterogeneity. ef ;

[0049] S4: Calculate the acidification yield increase ratio based on the dissolution rate η and the effective average acidification radius r. ef And a three-dimensional model of the acidizing production increase ratio for predicting and controlling the acidizing production increase effect of oil wells in different blocks of the oilfield;

[0050] S5: Using the three-dimensional model and combined with the dissolution rate η of different acid systems on reservoir rocks obtained in step S1, obtain a comparison chart of the production enhancement effect of different acid systems on different blocks, quickly identify oilfield acidification favorable blocks and recommend acid systems.

[0051] S6: Obtain the minimum acidization production increase ratio requirement value R for the oilfield. J For step S5, where the acidification yield increase ratio is less than the minimum acidification yield increase ratio requirement value R J The block is used to obtain the minimum acidification yield increase ratio requirement R under different acid systems using the 3D model drawing in step S4. J The design of the average minimum acidification radius r of the acid solution efdm .

[0052] Example 3

[0053] The difference from Examples 1 and 2 is that, in step S2, the original porosity data distribution of the reservoir in the oilfield block to be acidized is obtained, and then the average original porosity φ0 and average porosity φ are calculated according to the following formula. h

[0054]

[0055]

[0056] Where, a is the total number of porosity data points, in integer form; b is the total number of porosity data points greater than the average original porosity φ0, in integer form; i = 1, 2, ..., a, in integer form; j = 1, 2, ..., b, in integer form; φ i φ jThese are the original porosity data points, in dimensionless units.

[0057] Among them, obtaining the original porosity data distribution of the reservoir in the oilfield block to be acidized includes at least the following two methods: obtaining the reservoir rock porosity at each depth through well logging; and taking core samples at different well depths and then testing the porosity.

[0058] Additionally, in step S3, the effective average acidification radius r ef The calculation formula is as follows:

[0059] r ef =r efd (φ h / φ0) 5

[0060] Where, r efd The average radius of action of the acid solution is defined in meters.

[0061] In step S4, the formula for calculating the acidification yield increase ratio is as follows:

[0062]

[0063] In the formula, J0 and J are the oil production indices before and after acidizing, respectively, in m3 / d·MPa-1; re is the oil supply edge radius of the oil well, in m; rw is the wellbore radius, in m; and η is the acid dissolution rate of the rock, in dimensionless units.

[0064] Furthermore, in step S4, with the dissolution rate η as the X-axis and the effective average acidification radius r... ef A three-dimensional model of the prediction and control of the acidizing effect on oil wells in different blocks of the oilfield is plotted with the Y-axis as the Y-axis and the acidizing production increase ratio as the Z-axis.

[0065] In step S5, given the known dissolution rate and designed acidizing radius, if the z-axis value is higher than the minimum acidizing production increase ratio required by the oilfield company, then... J Therefore, this area is a favorable block for oilfield acidification in terms of this acid system.

[0066] In addition, in step S5, if the production increase ratio corresponding to the acid solution's dissolution rate η of the target reservoir and the average acidification radius of the target reservoir is greater than the minimum production increase ratio, then the acid solution system is a recommended acid solution system for the target reservoir.

[0067] In step S1, acid rock karstification experiments are conducted in accordance with the "QSYXJ0040-2001-Evaluation Method for Performance of Acidizing Fluids for Oilfields".

[0068] Example 4

[0069] This embodiment illustrates the process of predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells through an example. The examples involve oilfield blocks L1, L2, and L3 to be acidized, and acid systems S1 and S2 to be evaluated. The original porosity data of the reservoirs in blocks L1, L2, and L3 to be acidized were obtained by consulting relevant technical documents, such as... Figure 2 As shown. The original porosity data (a) of blocks L1, L2, and L3 are 31, 31, and 25, respectively, and the (b) values ​​are 18, 13, and 10, respectively. The designed average radius of action of the acid solution (r) is... efd The oil well supply edge radius is 200m; the wellbore radius rw is 0.10795m; and the minimum production increase ratio requirement RJ for the oilfield is 1.5.

[0070] A1: According to "QSYXJ0040-2001-Performance Evaluation Method of Acidizing Fluids for Oilfields", the average dissolution rates η of acid system S1 on the reservoir rocks of blocks L1, L2, and L3 were 12.5%, 12.6%, and 12.2%, respectively, and the average dissolution rates η of acid system S2 on the reservoir rocks of blocks L1, L2, and L3 were 26.5%, 26.7%, and 26.1%, respectively.

[0071] A2: From equation (1) Where 'a' represents the total number of porosity data points, in integer form; 'b' represents the total number of porosity data points greater than the average original porosity φ0, in integer form; 'i' = 1, 2, ..., a, in integer form; 'j' = 1, 2, ..., b, in integer form; 'φ' i φ j The original porosity data points are dimensionless. The average original porosity φ0 of the reservoirs in blocks L1, L2, and L3 are 13.8%, 13.8%, and 5.1%, respectively, and the average porosity data points greater than φ0, φh, are 16.2%, 18.5%, and 6.8%, respectively. A3: From equation (2)r ef =r efd (φ h / φ0) 5 Calculate the effective average acidification radius r of the acid solution in each block when considering the non-uniform acid distribution caused by reservoir heterogeneity. ef The measurements are 1.11m, 2.16m, and 2.10m respectively.

[0072] S4: Formula (3) In the formula, J0 and J are the oil production indices before and after acidizing, respectively, in m3 / d·MPa-1; re is the oil supply edge radius of the oil well, in m; rw is the wellbore radius, in m; and η is the acid solution's dissolution rate on the rock, in dimensionless units. Based on formula (3), the acidizing production increase ratio was calculated, and prediction and control charts of the acidizing production increase effect of oil wells in blocks L1, L2, and L3 were plotted. The results are shown in […]. Figure 3 , Figure 4 and Figure 5 .

[0073] A5: Using the chart in step A4 and combining it with the acid karstification experiment results in A1, obtain a comparison chart of the production enhancement effects of different acid systems on different blocks, such as... Figure 6 As shown. By Figure 6 It can quickly identify blocks L2 and L3 as favorable blocks for oilfield acidizing. For L2, acid system S2 is recommended, and for L3, acid system S1 or S2 is recommended.

[0074] A6: For block L1 where the acidification yield increase ratio in step A5 is less than 1.5, utilize... Figure 3 To obtain the design average minimum effective radius r of the acid solution for acid systems S1 and S2 when RJ≥1.5. efdm The measurements are 1.03m and 0.69m respectively.

[0075] The above embodiments are methods for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoirs by calculating the production enhancement ratio of wells based on the acid solution's dissolution rate and porosity parameters. Deep matrix acidizing is one of the key technologies for reservoir stimulation and well production enhancement in low-permeability sandstone oil reservoirs, and it has great potential for economical and efficient exploitation in offshore low-permeability oilfields with limited platform space and high construction safety risks. Because the rock properties, reservoir heterogeneity, fluid properties, and clay mineral content of reservoirs in different blocks and oil groups within an oilfield often vary significantly, the production enhancement effect of wells in different blocks can sometimes differ dramatically after using the same acid solution system and the same acidizing process. Therefore, establishing a method that can quickly, economically, and reliably predict and control the production enhancement effect of acidizing in low-permeability reservoirs is crucial for selecting the optimal acid solution system, optimizing construction technology, and rapidly identifying favorable blocks for acidizing in oilfields. Existing methods primarily rely on indirect evaluation of well acidizing effects through laboratory experiments using acid core flow. These methods suffer from drawbacks such as experimental complexity, high cost, low efficiency, and low reliability. Furthermore, existing numerical simulation-based predictions of well acidizing effects are significantly affected by human factors in parameter settings, and the limitations of theoretical models lead to substantial discrepancies between predicted and actual results. This embodiment proposes a new method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoirs. This method accurately assesses the production enhancement effect of acidizing using experimental data on the acid dissolution rate of the rock, enabling rapid and economical optimization of acid systems in low-permeability oilfields, improvement of acidizing processes, and identification of favorable acidizing blocks with high reliability.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells, characterized in that, Includes the following steps: S1: Select core samples from the reservoir of the oilfield block to be acidized, and conduct acid dissolution experiments using the core samples to obtain the dissolution rate of reservoir rocks by different acid systems. η; S2: Calculate the average original porosity of the reservoir in the oilfield block to be acidized. and greater than the average original porosity average porosity ; S3: Average original porosity obtained from step S2 and average porosity Calculate the effective average acidification radius of the acid solution in each block, considering the non-uniform acid distribution caused by reservoir heterogeneity. r ef ; S4: Calculate the acidification yield increase ratio based on the dissolution rate. rate η, Effective average acidification radius r ef And a three-dimensional model of the acidizing production increase ratio for predicting and controlling the acidizing production increase effect of oil wells in different blocks of the oilfield; S5: Using the 3D model and combined with the different acid systems obtained in step S1, the dissolution rate of the reservoir rock η To obtain comparative charts of the production enhancement effects of different acid systems on different blocks, quickly identify oilfield acidification favorable blocks and recommend acid systems; In step S2, the original porosity data distribution of the reservoir in the oilfield block to be acidized is obtained, and then the average original porosity is calculated according to the following formula. and average porosity Where a is the total number of porosity data points; b is the porosity greater than the average original porosity. The total number of porosity data points; i=1, 2, … , a; j=1, 2, …, b; These are the original porosity data points, in dimensionless units. In step S4, the formula for calculating the acidification yield increase ratio is as follows: In the formula, J 0 and J represent the oil well production index before and after acidizing, respectively, in units of... / ( d·MPa); r e The radius of the oil well's oil supply edge, in meters; r w η is the wellbore radius, in meters; η is the acid's dissolution rate on the rock, in dimensionless units; where, r efd The average radius of action of the acid solution is defined in meters.

2. The method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells according to claim 1, characterized in that, Obtaining the original porosity data distribution of the reservoir in the oilfield block to be acidized includes at least the following two methods: obtaining the reservoir rock porosity at each depth through well logging; and taking core samples at different well depths and then testing the porosity.

3. The method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells according to claim 1, characterized in that, In step S3, the effective average acidification radius r ef The calculation formula is as follows: 。 4. The method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells according to claim 1, characterized in that, In step S4, the dissolution rate η is taken as the X-axis. 、 Effective average acidification radius r ef A three-dimensional model of the prediction and control of the acidizing effect on oil wells in different blocks of the oilfield is plotted with the Y-axis as the Y-axis and the acidizing production increase ratio as the Z-axis.

5. The method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells according to claim 1, characterized in that, In step S5, given the known dissolution rate and designed acidification radius, if the corresponding value on the Z-axis is higher than the required minimum acidification yield increase ratio... R J Therefore, this area is a favorable block for oilfield acidification in terms of this acid system.

6. The method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells according to claim 1, characterized in that, In step S5, if the acid solution has a high dissolution rate on the target reservoir... η If the production increase ratio corresponding to the average acidization radius of the target reservoir is greater than the minimum production increase ratio, then the acid system is the recommended acid system for the target reservoir.

7. The method for predicting and controlling the production enhancement effect of acidizing in low-permeability reservoir oil wells according to any one of claims 1 to 6, characterized in that, It also includes step S6: obtaining the minimum acidization production increase ratio requirement for the oilfield. R J For step S5, where the acidification yield increase ratio is less than the minimum required acidification yield increase ratio value. R J The blocks are used to obtain the minimum acidification yield increase ratio requirements for different acid solutions using the 3D model diagram in step S4. R J The design of the average minimum acidification radius of the acid solution r efdm .

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