A method for optimizing parameters of segmented fracturing of oil and gas horizontal well

Abstract

The application discloses a kind of oil and gas horizontal well segmented fracturing parameter optimization method, belong to the reservoir reconstruction technology field in oil exploitation, specifically includes the following steps: step 1: using reservoir numerical simulation method to optimize fracture half-length, fracture conductivity and fracture spacing;Step 2: using fracturing simulation method, fracture half-length and fracture conductivity under different fracturing parameter conditions are calculated;Step 3: according to the fracturing simulation result under different fracturing parameter conditions, fracture half-length and fracture conductivity box plot are drawn;Step 4: according to the result on box plot four digits, median and lower four digits, complete fracturing parameter optimization.The optimization method of the application can directly show the concentration degree and distribution of fracture half-length and fracture conductivity under different fracturing parameter conditions, so as to realize the reasonable optimization of horizontal well segmented fracturing parameter, lay a foundation for the technical personnel in the field to optimize process measures, obtain more reasonable fracture half-length and fracture conductivity, optimize development index.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas well reservoir reconstruction in oil exploitation, and particularly relates to a method for optimizing parameters of segmented fracturing of oil and gas horizontal wells. BACKGROUND

[0002] Segmented fracturing of horizontal wells is a key technology for development of low-permeability and ultra-low-permeability oil and gas reservoirs, tight oil and gas reservoirs and shale oil and gas reservoirs. It is of great significance to use reasonable fracturing parameters to improve single-well production, optimize development indexes and effectively develop unconventional oil and gas on a large scale.

[0003] For optimization of parameters of segmented fracturing of unconventional oil and gas horizontal wells, engineers usually use numerical simulation to simulate and optimize fracture half-length, flow conductivity and fracture spacing, compare post-fracturing production under different conditions, and optimize with production as the target. Then, with the optimized fracture half-length and flow conductivity as the target, the optimization of fracturing parameters such as construction discharge, sanding intensity, liquid intensity and proppant proportion is carried out. Generally, the optimization method with average fracture half-length or flow conductivity obtained under different fracturing parameter conditions as the optimization target has the following deficiencies: first, segmented fracturing of horizontal wells needs to form dozens or even hundreds of artificial fractures, and due to the influence of reservoir stress interference and reservoir heterogeneity, the parameters such as fracture half-length, fracture height and width, and flow conductivity of the artificial fractures formed by fracturing are quite different; second, the method using average parameters is difficult to take into account the optimization demand of different proppant grain size proportions for multi-scale fractures of unconventional reservoirs. SUMMARY

[0004] In view of the problems in the prior art, the present application aims to provide a method for optimizing parameters of segmented fracturing of oil and gas horizontal wells, which comprises the following steps:

[0005] Step 1: using a reservoir numerical simulation method to optimize fracture half-length, fracture flow conductivity and fracture spacing.

[0006] Fixing two of the optimized fracture half-length, fracture flow conductivity and fracture spacing, changing the other parameter, and taking the cumulative production in 1-5 years as the target to obtain the optimized value of the variable. The three parameters are optimized in turn.

[0007] Step 2: using a fracturing simulation method to calculate fracture half-length and fracture flow conductivity under different fracturing parameter conditions.

[0008] Step 2.1: inputting the well profile structure and casing program parameters of the horizontal well;

[0009] Step 2.2: inputting the well trajectory and perforation parameters;

[0010] Step 2.3: establishing a stress profile and geological parameter model of the oil and gas reservoir;

[0011] Step 2.4: Select the liquid and proppant type;

[0012] Step 2.5: Simulate the fracture half-length and fracture conductivity under different fracturing parameters.

[0013] Step 3: Based on the fracturing simulation results under different fracturing parameters, draw a box-and-whisker plot of fracture half-length and fracture conductivity.

[0014] Step 4: Complete the fracturing parameter optimization based on the upper quartile, median, and lower quartile results of the box-and-whisker plot.

[0015] In the above method, in step 1, the reservoir numerical simulation is performed using one or more simulation software such as Eclipse, CMG, etc., preferably, Eclipse reservoir numerical simulation software is used.

[0016] In the above method, in step 2, the fracturing simulation is performed using one or more fracturing simulation software such as FracproPT, Gohfer, and Stimplan. Preferably, FracproPT fracturing simulation software is used.

[0017] In the above method, in step 2, the fracturing parameters are different construction displacement, sand addition intensity, fluid intensity, and proppant ratio.

[0018] In the above method, in step 3, the box-and-whisker plot of the fracturing simulation results includes 6 parameters, namely, lower limit, lower quartile, median, upper quartile, upper limit and outlier.

[0019] In the above method, in step 3, the box-and-whisker plot can represent the distribution concentration of a set of discrete data. The center line of the box is the median of the data, the upper and lower quartiles of the box contain 50% of the data, and the upper and lower limits are 1.5 times the difference between the upper and lower quartiles. The flatter the box, that is, the smaller the difference between the upper and lower quartiles of the box-and-whisker plot, the more concentrated the data.

[0020] In the above method, in step 4, the method for optimizing the fracturing parameters is to select as the optimization result the result whose median of the box-and-whisker plot is closest to the preferred fracture half-length or conductivity obtained by reservoir numerical simulation, or the result with the smallest difference between the upper quartile and the lower quartile of the box-and-whisker plot.

[0021] Compared with existing technologies, the present invention has the following advantages: Through reservoir numerical simulation and fracturing simulation, a box-and-whisker plot of fracturing parameters is generated, which is then used to optimize parameters. This optimization method can intuitively display the concentration and distribution of fracture half-lengths and fracture conductivity under different fracturing parameters, thereby achieving reasonable optimization of staged fracturing parameters for horizontal wells. This lays a foundation for those skilled in the art to optimize process measures, obtain more reasonable fracture half-lengths and fracture conductivity, and optimize development indicators, and is of great significance to the efficient and large-scale development of unconventional oil and gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an illustration of the box-and-whisker diagram of the present invention;

[0023] Figure 2 Schematic diagram of the stress and geological parameter model of Example 1 of the present invention;

[0024] Figure 3 is the box-whisker diagram of crack half-length under different displacement conditions;

[0025] Figure 4 The box-whisker diagram of crack half-length under different liquid strength conditions;

[0026] Figure 5 The box-whisker plot of half length of crack under different sand addition strength conditions;

[0027] Figure 6 Box-whisker plot of fracture conductivity under different proppant particle size combinations. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and examples, which are intended to illustrate and explain the present invention, but not to limit the scope of the present invention.

[0029] Example 1

[0030] A method for optimizing staged fracturing parameters for oil and gas horizontal wells is provided. This embodiment takes the horizontal well H21-20X after drilling as an example and specifically includes the following steps:

[0031] Step 1: Use Eclipse reservoir numerical simulation software to optimize fracture half-length, fracture conductivity, and fracture spacing.

[0032] Step 1.1: Optimize fracture half-length using Eclipse reservoir numerical simulation.

[0033] Simulation conditions: fixed fracture spacing of 10 m, fracture conductivity of 15 D·cm, fracture half-length of 80-240 m, and each fracture half-length increment of 10 m.

[0034] Simulation results: The three-year cumulative production is optimal when the fracture half-length is 170m. Therefore, the optimized fracture half-length is 170m.

[0035] Step 1.2: Optimize fracture conductivity through numerical simulation of Eclipse reservoir.

[0036] Simulation conditions: fixed fracture spacing of 10 m, fracture half-length of 170 m, fracture conductivity of 6-28 D·cm, and the conductivity increment of each fracture of 2 D·cm.

[0037] Simulation results show that the three-year cumulative production is optimal when the fracture conductivity is 16D·cm. Therefore, the optimized fracture conductivity is 16D·cm.

[0038] Step 1.3: Optimize fracture spacing using Eclipse reservoir numerical simulation.

[0039] Simulation conditions: fixed crack half-length 170m, crack conductivity 16D·cm, crack spacing 6-30m, and each crack spacing increment of 2m.

[0040] Simulation results: The three-year cumulative production is optimal when the seam spacing is 12m. Therefore, the optimal seam spacing is 12m.

[0041] Step 2: Use the "Fracturing Design" module of FracproPT fracturing simulation software for optimization. The specific steps are:

[0042] Step 2.1: Input the wellbore structure and casing program parameters of the H21-20X horizontal well, as shown in Table 1;

[0043] Table 1: Wellbore configuration and casing program input parameters

[0044] Drill bit size (mm×m) Casing size (mm×m) Cement return height (m) 346.0mm×452m 273.05mm×450.56m ground 215.9m×3065m 139.7mm×3055.91m ground

[0045] Step 2.2: Input the wellbore trajectory and perforation parameters. The wellbore trajectory is detailed in Table 2. The perforation parameters are: 60° phase perforation and 16 holes / m perforation density.

[0046] Table 2 Wellbore trajectory parameters

[0047]

[0048]

[0049]

[0050] Step 2.3: Build a stress and geological parameter model of the oil and gas reservoir;

[0051] The minimum ground stress, Young's modulus, Poisson's ratio, permeability and other parameters obtained by logging are input into the stress and geological parameter module of the fracturing simulation software to establish a stress and geological parameter model. The model diagram is shown in the figure below. Figure 2 shown.

[0052] Step 2.4: Select the liquid and proppant type;

[0053] The liquid selected was slick water with a viscosity of 9.0 mPa·s, and the proppant type selected was quartz sand.

[0054] Step 2.5: Simulate the fracture half-length and fracture conductivity under different fracturing parameters (operation displacement, fluid intensity, sand addition intensity, and proppant particle size combination). The fracturing software simulation uses the following fracturing parameters:

[0055] Construction displacement: 12m 3 / min, 14m 3 / min, 16m 3 / min, 18m 3 / min, 20m 3 / min;

[0056] Liquid strength: 23m 3 / m, 25m 3 / m, 27m 3 / m,29m 3 / m, 31m 3 / m;

[0057] Sand adding strength: 2.0t / m, 2.5t / m, 3.0t / m, 3.5t / m, 4.0t / m;

[0058] Proppant particle size: 70 / 140 mesh 100%, 40 / 70 mesh 100%, 30 / 50 mesh 100%, 70 / 140:40 / 70:30 / 50=2:5:3, 40 / 70:30 / 50=5:5;

[0059] Step 3: Based on the fracturing simulation results under different fracturing parameters, draw a box-and-whisker diagram of the fracture half-length and conductivity, such as Figures 3 to 6 shown.

[0060] Step 4: Complete the fracturing parameter optimization based on the upper quartile, median, and lower quartile results of the box-and-whisker plot.

[0061] Figure 3is the fracture half-length box plot under different displacement conditions obtained by fracturing simulation. The range interval of the box plot box indicates the fracture half-length range obtained by fracturing simulation, the upper limit of the graph is the maximum fracture half-length value obtained by simulation, the lower limit is the minimum fracture half-length value obtained by simulation, the entire box is the range of upper and lower quartiles, and the horizontal line in the box is the median line. It can be seen from Figure 3 that when the displacement is 16 m 3 / min, the median line is closest to the optimal fracture half-length value 170 m obtained by Eclipse reservoir numerical simulation, and the difference between the upper and lower quartiles of the box plot is the smallest, and the data is the most concentrated, so 16 m 3 / min is the preferred construction displacement.

[0062] Figure 4 is the fracture half-length box plot under different fluid intensity conditions obtained by fracturing simulation. It can be seen from Figure 4 that the median lines of fluid intensity of 27 m 3 / m and 29 m 3 / m are relatively close to the optimal fracture half-length value 170 m obtained by Eclipse reservoir numerical simulation, and the difference between the upper and lower quartiles of the box plot of fluid intensity of 27 m 3 / m is the smallest, and the data is the most concentrated, so 27 m 3 / m is the preferred fluid intensity.

[0063] Figure 5 is the fracture half-length box plot under different sanding intensity conditions obtained by fracturing simulation. It can be seen from Figure 5 that the median lines of sanding intensity of 3.0 t / m, 3.5 t / m and 4.0 t / m are relatively close to the optimal fracture half-length value 170 m obtained by Eclipse reservoir numerical simulation, and the difference between the upper and lower quartiles of the box plot of sanding intensity of 3.5 t / m is the smallest, and the data is the most concentrated, so 3.5 t / m is the preferred sanding intensity.

[0064] Figure 6 is the fracture conductivity box plot under different proppant particle size combinations obtained by fracturing simulation. It can be seen from Figure 6 that the median line of the proppant particle size of 70 / 140:40 / 70:30 / 50=2:5:3 is closest to the optimal fracture conductivity 16 D·cm obtained by Eclipse reservoir numerical simulation, and the difference between the upper and lower quartiles of the box plot is the smallest, and the data is the most concentrated, so 70 / 140:40 / 70:30 / 50=2:5:3 is the preferred particle size combination result.

[0065] The above description is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for optimizing staged fracturing parameters for oil and gas horizontal wells, characterized in that: The method comprises the following steps: Step 1: Optimize fracture half-length, fracture conductivity, and fracture spacing using a reservoir numerical simulation method. The reservoir numerical simulation method involves fixing two of the optimized parameters, fracture half-length, fracture conductivity, and fracture spacing, while varying the other parameter. The cumulative production over 1-5 years is used as the target, and the optimized values ​​of the variable parameters are obtained. The three parameters are then optimized sequentially. Step 2: Using a fracturing simulation method, calculate the fracture half-length and fracture conductivity under different fracturing parameters. Fracturing parameters include operation displacement, sand injection intensity, fluid intensity, and proppant ratio. Step 2.1: Input the wellbore structure and casing program parameters of the horizontal well; Step 2.2: Input wellbore trajectory and perforation parameters; Step 2.3: Establish a stress profile and geological parameter model of the oil and gas reservoir; Step 2.4: Select the liquid and proppant type; Step 2.5: Simulate the fracture half-length and fracture conductivity under different fracturing parameters; Step 3: Based on the fracturing simulation results under different fracturing parameters, draw a box-and-whisker plot of fracture half-length and fracture conductivity; Step 4: Based on the upper quartile, median, and lower quartile results of the box-and-whisker plot, complete the fracturing parameter optimization. The method for optimizing fracturing parameters is to select the result with the median of the box-and-whisker plot closest to the preferred fracture half-length or fracture conductivity obtained from reservoir numerical simulation, or the result with the smallest difference between the upper quartile and the lower quartile of the box-and-whisker plot as the optimized result.

2. The method according to claim 1, characterized in that The oil and gas horizontal wells include shale oil and gas horizontal wells, tight oil and gas horizontal wells or low permeability and extra-low permeability oil and gas horizontal wells.

3. The method according to claim 1, characterized in that In step 1, the reservoir numerical simulation uses Eclipse simulation software.

4. The method according to claim 1, wherein In step 1, the fracture half-length is 170 m, the fracture conductivity is 16 D·cm, and the fracture spacing is 12 m.

5. The method according to claim 1, wherein In step 2, the fracturing simulation uses FracproPT simulation software.

6. The method according to claim 1, characterized in that In step 3, the box-and-whisker plot of the fracturing simulation results includes six parameters, namely, lower limit, lower quartile, median, upper quartile, upper limit and outlier.

7. The method according to claim 1, characterized in that In step 4, the optimized fracturing parameters are: construction displacement of 16 m³ / min, liquid intensity of 27 m³ / m, sand addition intensity of 3.5 t / m, and proppant particle size combination of 70 / 140:40 / 70:30 / 50=2:5:3.

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