Method for predicting blowout rate of oil and gas well

Abstract

The invention discloses an oil and gas well blowout rate prediction method, which belongs to the field of petroleum and natural gas industry, and comprises the following steps: establishing a finite element model according to working conditions near a well site; carrying out a blowout ignition experiment, and measuring the heights of multiple groups of wellhead flames; a finite element model is set according to the ignition experiment working condition, a temperature cloud picture under the ignition experiment working condition is obtained, and an actual flame contour line is determined; according to well site operation conditions, orthogonal factors influencing the blowout rate and the calculation range of the orthogonal factors are determined, an orthogonal test table is designed, the same initial environment conditions are taken for numerical simulation calculation, and an orthogonal database of the actual flame height is obtained; and according to a least square method, considering the interaction between factors, and fitting to form a nonlinear equation for predicting the blowout rate. According to the method, numerical simulation is adopted to predict the real blowout condition, the influence of multiple factors such as wellhead deformation, wind speed and oil and gas components is comprehensively considered, and the oil and gas injection quantity prediction accuracy is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas industry, and particularly to a method for predicting the blowout volume of oil and gas wells. Background Art

[0002] Blowout out-of-control and catching fire is different from general petrochemical fires. Due to excessive formation pressure, the oil and gas jet of the out-of-control well can reach a position dozens of meters above the ground. Once on fire, the oil and gas jet burns rapidly to form a huge combustion fire column, which can generally be as high as 50 meters or even more than 100 meters. Under high pressure, the combustion temperature of the out-of-control oil and gas and air is extremely high, and the thermal radiation is strong. After a high-pressure and high-yield well catches fire, the derrick often collapses, the drill rig base deforms, and the rotary table tilts; the high combustion temperature will cause the wellhead to deform and the device to fail. The complex well site environment will change the jet direction of the out-of-control oil and gas, resulting in multi-directional fires and forming irregular combustion. The high-pressure oil and gas jet speed in the blowout wellbore is extremely fast, bringing huge noise. Oil well leakage will cause damage to the biological environment. During the rescue process, wells with large oil and gas production have stronger impact force. The demand for the positions and quantities of water guns and water cannons increases, and the wellhead and equipment need to be sprayed with water for cooling and protection; personnel need to be equipped with appropriate protective measures to enter high-risk areas for emergency rescue. The blowout volume, as an important judgment basis for the leakage degree and damage consequences of oil and gas wells, can provide timely and reliable well site information for rescue work. Therefore, timely mastering the out-of-control blowout volume in blowout accidents is of great significance for guiding the rescue work of blowout accidents and dividing the safety protection distance.

[0003] Due to the complex and changeable internal environment of oil and gas wells, it is impossible to install measuring instruments at the wellhead and place reference objects in the high-speed jet after blowout out-of-control, so the blowout volume data can only be obtained indirectly. At present, those skilled in the art mostly use the Bernoulli equation to analyze and deduce the relationship between the blowout volume of oil and gas wells and the flame height. To ensure the stability of the calculation results, the relationship derivation generally includes multiple simplified assumptions, and it is difficult to consider the complex changes in the well site, so the accuracy is low and it is difficult to apply to actual operations. Summary of the Invention

[0004] In order to overcome the problems that the traditional method has a large amount of calculation and low accuracy, resulting in difficulty in accurately mastering the out-of-control blowout volume in blowout accidents, the present invention proposes a method for predicting the blowout volume of oil and gas wells. This method uses numerical simulation to predict the real situation of blowout, comprehensively considers the influence of many factors such as wellhead deformation, wind speed, and oil and gas components, and greatly improves the accuracy of oil and gas blowout volume prediction.

[0005] In order to achieve the above invention purpose, the technical solution of the present invention is as follows:

[0006] A method for predicting the blowout volume of oil and gas wells, characterized by comprising the following steps:

[0007] Step a: Establish a finite element model of blowout fire according to the working conditions near the well site;

[0008] Step b: Conduct a blowout ignition experiment and measure multiple groups of wellhead flame heights;

[0009] Step c: Set the finite element model according to the ignition experiment conditions, obtain the temperature contour map under the ignition experiment conditions, and determine the actual flame contour line in combination with the flame height data of the ignition experiment;

[0010] Step d: Determine the orthogonal factors affecting the blowout volume and their calculation ranges according to the well site operation conditions, design an orthogonal test table, conduct numerical simulation calculations under the same initial environmental conditions, and obtain an orthogonal database of actual flame heights in combination with the actual flame contour line;

[0011] Step e: Based on the least squares method and considering the interaction between factors, fit and form a nonlinear equation that can be used for blowout volume prediction.

[0012] Furthermore, the specific steps for establishing the finite element model of blowout fire include:

[0013] Step a1: Use 3D software to draw a blowout fire solid model and perform finite element meshing to form a number of grids;

[0014] Step a2: Select a combustion model, an energy model, and a turbulence model;

[0015] Step a3: Set boundary conditions.

[0016] Furthermore, in the finite element model, the blowout inlet adopts a mass inlet boundary condition, the initial total temperature of the computational domain is 300K, the outer field watershed plane adopts a pressure outlet boundary, and the initial pressure is 0.1MPa.

[0017] Furthermore, in step b, the specific steps for conducting a blowout ignition experiment and measuring multiple groups of wellhead flame heights include:

[0018] Step b1: Arrange three groups of reference objects with different heights around the wellhead as the center, and arrange a visible light camera on the extension line of the connection between the wellhead and each group of reference objects to ensure that the wellhead, the reference objects, and the visible light camera are on the same straight line;

[0019] Step b2: Obtain the distances between the wellhead and each group of reference objects and the visible light camera through a ranging sensor;

[0020] Step b3: According to the flame images recorded by the visible light camera, calculate the corresponding flame height under each group of reference objects using the principle of similar triangles, and take the average value of the three heights as the actual flame height.

[0021] Further, in step b3, the flame height is calculated by the following formula:

[0022]

[0023] In the formula, i = 1, 2, 3, representing the reference objects; Q i is the flame height of the reference object i; L i represents the distance between the wellhead and the reference object i; N i represents the distance between the wellhead and the visible light camera corresponding to the reference object i; H i represents the actual height of the reference object i, Q * and H * are respectively the flame height and the reference object height in the image recorded by the visible light camera.

[0024] Further, in step c, multiple groups of isotherms in the temperature cloud map are taken as the flame contour lines, and the flame height corresponding to each group of isotherms is calculated; by comparing the flame height obtained from the numerical simulation calculation with that measured in the ignition experiment, the isotherm with the smallest deviation from the flame height measured in the ignition experiment is the actual flame contour line.

[0025] Further, in step b1, the lens of the visible light camera is kept horizontal and the use of a wide-angle lens is avoided.

[0026] Further, in step d, the determined orthogonal factors include the blowout volume, wellhead diameter, wellhead deformation degree, wind speed, and oil content.

[0027] Further, in step b2, the ranging sensor is a laser ranging sensor.

[0028] In summary, the present invention has the following advantages:

[0029] 1. The present invention uses engineering software for numerical simulation calculation and fitting, and only non-professionals can complete the operation process on the premise of understanding the basic parameter settings. It has strong applicability and simple operation; 2. The numerical simulation method adopted by the present invention has powerful computing ability, can comprehensively consider the influence of many factors such as wellhead deformation, wind speed, and oil and gas components, and the calculation accuracy is significantly improved compared with the traditional theoretical calculation. Brief Description of the Drawings

[0030] Figure 1 is a flowchart for implementing a method for predicting the blowout volume of an oil and gas well;

[0031] Figure 2 is a schematic diagram for measuring the ground flame height;

[0032] Figure 3 is an isotherm diagram of the flame contour;

[0033] In the figure:

[0034] 1. First visible light camera, 2. First reference object, 3. Second visible light camera, 4. Second reference object, 5. Third visible light camera, 6. Third reference object, 7. Wellhead flame. Detailed implementation manners

[0035] To more clearly illustrate the present invention, the present invention will be further described below in conjunction with preferred embodiments and the accompanying drawings. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0036] The present invention provides a method for predicting the blowout volume of an oil and gas well, including the following steps:

[0037] Step 1: Establish a finite element model according to the working conditions near the well site.

[0038] (1) Use 3D software to draw a blowout and fire solid model, and perform finite element meshing to form a number of grids.

[0039] (2) Select the correct combustion model, energy model and turbulence model.

[0040] (3) The mass inlet boundary condition is adopted at the blowout inlet, the initial total temperature of the computational domain is 300K, and the pressure outlet boundary is adopted for the outer field flow domain plane, and the initial pressure is 0.1MPa.

[0041] Step 2: Conduct a blowout ignition experiment to measure multiple groups of wellhead flame heights for comparison with the subsequent numerical simulation calculation results.

[0042] (1) With the wellhead as the center, arrange three groups of reference objects with heights of H1, H2, and H3 around, and arrange three groups of visible light cameras on the extension lines of the straight lines between the wellhead and the reference objects. Preferably, the lenses of the visible light cameras should be kept horizontal and avoid using wide angles to prevent image distortion and thus affect the measured height.

[0043] (2) Use a ranging sensor to obtain the distances between the wellhead and the reference objects and the visible light cameras as L1, L2, L3 and N1, N2, N3 respectively. Preferably, the ranging sensor is a laser ranging sensor.

[0044] (3) Calculate the flame height based on the flame images recorded by the visible light cameras. Using the principle of similar triangles, three groups of flame heights can be calculated:

[0045]

[0046] In the formula Q i is the flame height, i = 1, 2, 3, Q* and H* are the flame height and the reference object height in the recorded image.

[0047] Take the average value of three groups of heights as the actual flame height Q:

[0048]

[0049] Step 3: Set up the finite element model according to the ignition experiment conditions to obtain the temperature contour map under the ignition experiment conditions. Take multiple groups of isotherms as the flame contour lines and calculate the flame height. The isotherm with the smallest deviation from the flame height obtained from the ignition experiment is the actual flame contour line.

[0050] Step 4: According to the wellsite conditions, select the well blowout volume, wellhead diameter, wellhead deformation degree, wind speed, and oil content as orthogonal factors, and determine the calculation ranges of the orthogonal factors based on the daily gas production volume, oil casing diameter, wellhead deformation, environmental wind grade, and oil content of the regional wells. Design an orthogonal experiment table, and perform numerical simulation calculations under the same initial environmental conditions to obtain the orthogonal database of the actual flame height. Preferably, the determined orthogonal factors include.

[0051] Step 5: Based on the least squares method, considering the interaction between factors, use the wellhead diameter, wellhead deformation degree, wind speed, oil content, and flame height as independent variables and the well blowout volume as the dependent variable for non-linear fitting to form a non-linear equation that can be used for predicting the well blowout volume.

[0052] Example 1

[0053] The following uses a specific application example to illustrate a method for predicting the well blowout volume of an oil and gas well of the present invention. The specific implementation process is as follows:

[0054] Step 1: According to the conditions of the wellsite near the well, construct a three-dimensional solid model of well blowout and fire, and complete grid division, model selection, and boundary setting.

[0055] Step 2: Conduct a well blowout ignition experiment and measure multiple groups of wellhead flame heights. With the wellhead as the center, arrange three groups of reference objects with a height H of 1.5 m and three groups of visible light cameras, and ensure that the wellhead, reference objects, and visible light cameras are on the same straight line ( Figure 2 as shown). The distances L1, L2, L3 and N1, N2, N3 between the reference objects and the visible light cameras and the wellhead are shown in Table 1.

[0056] Table 1 Position parameters of the measurement device

[0057]

[0058] Calculate the flame height based on the flame images recorded by the visible light cameras. Using the principle of similar triangles, three groups of flame heights can be calculated:

[0059]

[0060] In the formula, Q i is the flame height, i = 1, 2, 3, Q* and H* are the flame height and the reference object height in the recorded image.

[0061] Take the average value of the three groups of heights as the actual flame height Q:

[0062]

[0063] The flame height obtained through experimental measurement is shown in Table 2.

[0064] Table 2 Flame height measured in the experiment

[0065]

[0066]

[0067] Step 3: Complete the finite element model setting according to the experimental conditions in Step 2, and calculate the temperature contour map under the ignition experimental conditions. As Figure 3 shown, take multiple groups of isotherms as the flame contour line and calculate the flame height. The flame height corresponding to the 800K isotherm has the smallest deviation from the experimental value. Therefore, the 800K isotherm is used as the actual flame contour line.

[0068] Step 4: According to the wellsite operation conditions, select the well blowout volume, wellhead diameter, wellhead deformation degree, environmental wind speed, and oil content as the orthogonal factors. Determine the calculation range of the orthogonal factors based on the daily gas production, oil casing diameter, wellhead deformation, environmental wind level, and oil content of the regional wells. As shown in Table 3, the factors and ranges selected in this example are applicable to high-pressure gas wells with a well blowout volume of 1.5 - 15 million cubic meters per day, a wellhead diameter of 127 - 180 mm, a wellhead deformation degree of 1 - 2, an environmental wind speed of 0 - 13.8 m / s, and an oil content of 0 - 1000 tons per 10 million cubic meters.

[0069] Table 3 Orthogonal factors and calculation ranges

[0070]

[0071] According to the number of orthogonal factors and the number of levels, a five-factor five-level design is adopted to conduct 25 numerical simulation calculations in total. The calculated flame height F is extracted according to the actual flame contour line (800K isotherm) determined in Step 3. The specific design scheme and calculation results are shown in Table 4.

[0072] Table 4 Orthogonal table

[0073]

[0074]

[0075] Step 5: According to the least squares method and considering the interaction between factors, taking the wellhead diameter B, wellhead deformation degree C, wind speed D, oil content E, and flame height F as independent variables and the wellhead spray volume A as the dependent variable, perform non-linear fitting.

[0076] The non-linear formula obtained by fitting is:

[0077] A = -4464 + 11.53B + 1738C - 173D + 0.33E + 55.7F - 0.00157B*B + 2C*C + 8.12D*D + 0.000221E*E - 0.0271F*F - 3.64B*C + 0.050B*D - 0.00074B*E - 0.0673B*F + 4.6C*D - 0.013C*E - 12.10C*F + 0.0504D*E + 1.109D*F - 0.01216E*F

[0078] Through fitting analysis, a regression analysis table and an analysis of variance table can be obtained.

[0079] Table 5 Regression analysis table

[0080]

[0081] Table 6 Analysis of variance table

[0082]

[0083] In the regression analysis table, the Adjusted R square is the adjusted fitting coefficient, which can be used to explain the degree to which the independent variable explains the variation of the dependent variable. Table 5 shows that the independent variable can explain 97.61% of the dependent variable, indicating a very high correlation.

[0084] In the analysis of variance table, the regression effect is determined through the F test, where F = 49.98, which is much larger than F0.05(20,4) = 5.80, indicating a significant regression effect.

[0085] Taking the blowout of Well Boz BZ3-1X in 2020 as an example, the initial unchoked flow rate during the blowout was 12.72 million m³ / day, the wellhead diameter was 280 mm, and the flame height was 80 m under windless conditions. Substituting these values into the calculation, the predicted blowout volume was 11.6915 million m³ / day, with a difference of 8.09% between the two, which can illustrate the feasibility and accuracy of the method for predicting blowout volume based on numerical simulation of the present invention.

[0086] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modifications and equivalent changes made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the present invention.

Claims

1. A method for predicting the blowout volume of an oil and gas well, characterized in that, It includes the following steps: Step a: Establish a finite element model of blowout fire according to the working conditions near the well site; Step b: Conduct a blowout ignition experiment and measure multiple groups of wellhead flame heights; Step c: Set the finite element model according to the ignition experiment conditions, obtain the temperature contour map under the ignition experiment conditions, and determine the actual flame contour line in combination with the flame height data of the ignition experiment; Step d: Determine the orthogonal factors affecting the blowout volume and their calculation ranges according to the well site operation conditions, design an orthogonal experiment table, conduct numerical simulation calculations under the same initial environmental conditions, and obtain an orthogonal database of actual flame heights in combination with the actual flame contour line; Step e: Based on the least squares method and considering the interaction between factors, fit to form a non-linear equation for predicting the blowout volume.

2. The method for predicting the blowout volume of an oil and gas well according to claim 1, wherein For the establishment of the finite element model of blowout fire, the specific steps include: Step a1: Use 3D software to draw a solid model of blowout fire and conduct finite element division to form a certain number of meshes; Step a2: Select a combustion model, an energy model, and a turbulence model; Step a3: Set boundary conditions.

3. The method for predicting the blowout volume of an oil and gas well according to claim 2, characterized in that, In the finite element model, a mass inlet boundary condition is adopted for the blowout inlet, the initial total temperature of the calculation domain is 300K, a pressure outlet boundary is adopted for the outer field watershed plane, and the initial pressure is 0.1MPa.

4. A method for predicting the blowout volume of an oil and gas well according to claim 1, characterized in that, In step b, for the conduct of the blowout ignition experiment and the measurement of multiple groups of wellhead flame heights, it specifically includes: Step b1: Arrange three groups of reference objects with different heights around the wellhead as the center, and arrange a visible light camera on the extension line of the connection between the wellhead and each group of reference objects to ensure that the wellhead, the reference objects, and the visible light camera are on the same straight line; Step b2: Obtain the distances between the wellhead and each group of reference objects and the visible light camera through a distance measuring sensor; Step b3: According to the flame images recorded by the visible light camera, calculate the corresponding flame height under each group of reference objects using the principle of similar triangles, and take the average value of the three heights as the actual flame height.

5. The method for predicting the blowout volume of an oil and gas well according to claim 4, characterized in that, In step b3, the flame height is calculated by the following formula: wherein, i = 1, 2, 3, represents a reference object; Q i is the flame height of the reference object i; L i represents the distance between the wellhead and the reference object i; N i represents the distance between the wellhead and the visible light camera corresponding to the reference object i; H i represents the actual height of the reference object i, and Q* and H* are the flame height and the reference object height in the image recorded by the visible light camera, respectively.

6. The method for predicting the blowout volume of an oil and gas well according to claim 1, wherein In step c, take multiple groups of isotherms in the temperature contour map as the flame contour line, and calculate the flame height corresponding to each group of isotherms; compare the flame height measured by numerical simulation calculation with that of the ignition experiment, and the isotherm with the smallest deviation from the flame height measured by the ignition experiment is the actual flame contour line.

7. A method for predicting the blowout volume of an oil and gas well according to claim 4, characterized in that, In step b1, the lens of the visible light camera remains horizontal and avoid using a wide angle.

8. A method for predicting the blowout volume of an oil and gas well according to claim 1, characterized in that, In step d, the determined orthogonal factors include blowout volume, wellhead diameter, wellhead deformation degree, wind speed, and oil content.

9. A method for predicting the blowout volume of an oil and gas well according to claim 1, characterized in that, In step b2, the distance measuring sensor is a laser distance measuring sensor.

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