A method for calculating phase transition points in the wellbore of CO2-enhanced oil reservoirs
By combining PVTsim and OLGA software, a method for calculating the phase transition point of CO2-driven oil wells was established, which solved the problem of inaccurate prediction results in existing technologies, and realized the rapid and accurate prediction of the phase transition point of the wellbore, providing a reliable basis for anti-wax measures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHWEST PETROLEUM UNIV
- Filing Date
- 2026-01-16
- Publication Date
- 2026-07-07
AI Technical Summary
Existing technologies struggle to quickly and accurately predict the gas-liquid phase transition point and wax deposition phase transition point in CO2-driven oil wells, leading to wax buildup in the wellbore that affects production. There is a lack of calculation methods that comprehensively consider multiple factors.
The PVTsim software was used for fluid blending, and the OLGA software was used to establish a multiphase flow model of the wellbore. The phase transition point of the wellbore was calculated by numerical simulation, and the calculation formula for the depth of the phase transition point was established, taking into account the effects of flow velocity, oil pressure and water cut.
It enables rapid and accurate prediction of phase transition points in wellbore, providing a direct basis for formulating anti-wax measures and improving the reliability and applicability of the prediction results.
Smart Images
Figure CN121854020B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of CO2 injection technology for oil reservoir development, and in particular to a method for calculating the phase transition point of a wellbore in a CO2-driven oil reservoir. Background Technology
[0002] Given the potential of CCUS technology to significantly improve reservoir recovery and the "dual carbon" context, CO2 flooding enhanced oil recovery technology, with its combined value in both efficiency enhancement and carbon sequestration, has become a crucial technology for oil and gas field development that urgently needs breakthroughs. However, during CO2 flooding development, changes in temperature and pressure within the wellbore cause complex phase transitions in the fluid, resulting in gas-liquid two-phase flow and even wax precipitation. This leads to wax buildup in the wellbore, reducing crude oil flowability and severely impacting normal well production. Accurately predicting the locations of gas-liquid phase transition points and wax precipitation phase transition points in the wellbore is key to developing effective wax prevention and removal measures.
[0003] Currently, the prediction of wellbore phase transitions largely relies on case-by-case calculations using numerical simulation software or estimations based on semi-empirical formulas. The former involves complex calculations, making rapid field application difficult; the latter often ignores the coupled effects of multiple factors such as flow velocity, oil pressure, and water cut, resulting in poor predictive universality and insufficient accuracy. Particularly for CO2-driven reservoirs with complex physical properties, such as tight conglomerate, a method that can comprehensively consider multiple factors and rapidly and quantitatively calculate wellbore phase transition points is lacking. Therefore, there is an urgent need to propose a wellbore phase transition point calculation method that is clear in its calculation process, reliable in its results, and easy to apply in the field. Summary of the Invention
[0004] To address the problems of poor predictive universality, insufficient accuracy, and complex prediction processes in existing wellbore phase change prediction methods, this invention provides a method for calculating phase transition points in CO2-driven oil reservoirs, which can accurately predict the depth and location of gas-liquid phase transitions and wax precipitation phase transitions in the wellbore.
[0005] The method for calculating the phase transition point of a CO2-driven oil wellbore provided by this invention mainly includes the following steps:
[0006] (1) Based on the formation fluid of the target well, the active oil was compounded using PVTsim software, and the bubble point temperature-pressure relationship curve and the wax precipitation temperature-pressure relationship curve were calculated.
[0007] (2) An accurate wellbore multiphase flow model was established using the professional multiphase flow simulation software OLGA, and numerical simulations were performed by changing the flow velocity. Oil pressure P, water content Three parameters were used to calculate the temperature-well depth curves and pressure-well depth curves of the target well under different operating conditions;
[0008] (3) Using pressure as an intermediate variable, the relationship curves of bubble point temperature-well depth and wax precipitation temperature-well depth under different working conditions were calculated;
[0009] (4) Calculate the intersection of the temperature-depth curve of the target well with the bubble point temperature-depth curve, and the intersection of the temperature-depth curve of the target well with the wax precipitation temperature-depth curve, so as to obtain the phase change point depth (the gas-liquid phase change point depth and the wax precipitation phase change point depth, respectively).
[0010] (5) Based on the calculated phase change point depth data, establish a formula for calculating the phase change point depth, which can be used to quickly predict the phase change point location of the target wellbore.
[0011] (6) Substitute the measured production conditions of the target well into the formula for calculating the phase transition point depth to calculate the location of the phase transition point depth of the target well under the production conditions.
[0012] Compared with the prior art, the advantages of the present invention are:
[0013] (1) This invention establishes an efficient and accurate formula for calculating the phase change point of CO2-driven oil wells, realizing the transformation from "numerical simulation" to "rapid on-site calculation", which greatly improves the calculation speed of the gas-liquid phase change point depth and the wax phase change point depth, and realizes the rapid prediction of the phase change point of CO2-driven oil reservoir wells.
[0014] (2) The calculation method provided by the present invention is based on the accurate simulation results of OLGA software. It fully considers the coupling effect of three key production parameters, namely flow rate, oil pressure and water content, on the gas-liquid phase change point and the wax precipitation phase change point. The prediction results are more accurate, providing a direct basis for predicting the gas-liquid phase change point and the wax precipitation phase change point and for formulating precise wax prevention and removal measures.
[0015] (3) This invention uses the fluid simulation software PVTsim to perform live oil blending and the professional multiphase flow simulation software OLGA to perform wellbore modeling and numerical simulation, ensuring the reliability and authority of the numerical simulation.
[0016] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the calculation method for phase transition points in the wellbore of a CO2-driven oil reservoir according to the present invention.
[0018] Figure 2 This is the bubble point temperature-pressure relationship curve obtained in the example.
[0019] Figure 3The curve showing the temperature-pressure relationship of wax precipitation obtained in the examples is shown.
[0020] Figure 4 These are the pressure-well depth curves and temperature-well depth curves obtained at different flow rates in the examples.
[0021] Figure 5 These are the pressure-well depth curves and temperature-well depth curves obtained in the examples under different oil pressures.
[0022] Figure 6 These are the pressure-well depth curves and temperature-well depth curves obtained in the examples at different water cuts.
[0023] Figure 7 These are the bubble point temperature-well depth relationship curves and wax precipitation temperature-well depth relationship curves obtained in the examples at different flow rates.
[0024] Figure 8 These are the bubble point temperature-well depth relationship curves and wax precipitation temperature-well depth relationship curves obtained in the examples under different oil pressures.
[0025] Figure 9 The bubble point temperature-well depth relationship curves and wax precipitation temperature-well depth relationship curves obtained in the examples are shown. Detailed Implementation
[0026] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0027] This embodiment selects an oil well in Block X of an oilfield as the target well to illustrate in detail the method for calculating the phase transition point of a CO2-driven oil reservoir wellbore according to the present invention. Figure 1 As shown, the specific steps are as follows:
[0028] S1: Calculate the bubble point temperature-pressure relationship curve and the wax precipitation temperature-pressure relationship curve.
[0029] S11: Based on the composition data of the degassed crude oil and associated gas samples from the target well, the fluid numerical simulation software PVTsim was used to perform live oil recombination according to the production gas-oil ratio. The oil phase and gas phase composition data are shown in Tables 1 and 2. Using the Recombine function module in PVTsim software, the gas-oil ratio was set to 251.68 to perform live oil recombination and obtain the phase model of the formation fluid in the target well. The formation fluid composition data after recombination are shown in Table 3.
[0030] Table 1 Oil phase composition data
[0031]
[0032] Table 2 Gas phase component data
[0033]
[0034] Table 3. Formation fluid composition data after compounding
[0035]
[0036] S12: Using the Wax Simulations module in the Flow Assurance function of the PVTsim software, set the mole fraction of wax component in the formation fluid of the target well, and set the temperature and pressure range from the bottom of the well to the wellhead based on the measured data. Perform three-phase flash evaporation calculation to obtain the bubble point temperature-pressure relationship curve and the wax precipitation temperature-pressure relationship curve of the target well under the production gas-oil ratio.
[0037] In this embodiment, based on the measured production data of the target well, C 7+ The component is a pseudo-component of wax precipitation, and its mole fraction of wax component is set to 0.7. The production gas-oil ratio of this well is 251.68, the temperature range from the bottom of the well to the wellhead is 120~-20℃, and the pressure range from the bottom of the well to the wellhead is 500~10 bar. These values are input into the calculation module for three-phase flash evaporation calculation to obtain the bubble point temperature-pressure relationship curve of the target well under the production gas-oil ratio. Figure 2 ) and the wax precipitation temperature-pressure relationship curve ( Figure 3 ).
[0038] S2: Calculate the temperature and pressure profile of the target well; including the following sub-steps:
[0039] S21: Based on the measured well inclination data and well structure data of the target well, an accurate wellbore model is established using OLGA software.
[0040] In this embodiment, the wellbore modeling was performed using the multiphase flow simulation software OLGA. Parameters for various casing and tubing types were input into the OLGA software: tubing hanger × 0.33m; 208 N80 grade Ф73mm flat tubing pieces × 1985.29m; Ф38mm full-bore pump (heavy ball) × 8.24m, H = 2003.73m; double male short section × 0.5m; 2 Φ73mm tailpipes × 1 9.19m, 1 unit of Φ89mm combined eccentric gas anchor × 4.46m, H=2027.88m; 3 Φ73mm sand-absorbing pipes with dead plugs × 28.89m, H=2056.77m; perforation layer top boundary: 3376.5m, bottom boundary: 3424.0m; artificial well bottom is 3457.63m, and the completed well depth is 3470.00m. Based on the above parameters, a wellbore model is established.
[0041] S22: Based on the measured water cut data, set the water cut in the formation fluid phase model established in step S1 and import it into the wellbore model. Then, set the production parameters of the wellbore model based on the measured production data to establish a wellbore multiphase flow model.
[0042] In this embodiment, the water content W of the formation fluid established in step S1 is set based on the measured water content data. c The production conditions were set based on the measured production data of the well, with the wellhead pressure P1 set to 6.56 MPa and temperature T1 set to 28℃; the bottom hole pressure P2 set to 28.8 MPa and temperature T2 set to 90℃; the fluid velocity set to 6.19 t / d; and the ambient temperature set to 5~90℃. A multiphase flow model of the target well under these production conditions was established.
[0043] S23: Based on the established wellbore multiphase flow model, numerical simulation is performed using the controlled variable method. Other parameters are fixed, and the flow velocity, oil pressure, and water cut are changed respectively to calculate the temperature and pressure profile of the target well under different operating conditions.
[0044] In this embodiment, the controlled variable method was used. With other production conditions remaining constant, the flow rate was set to 2-10 t / d, the oil pressure was fixed at 6.56 MPa, and the water cut was fixed at 46.17%; the oil pressure was set to 2-10 MPa, the flow rate was fixed at 6.19 t / d, and the water cut was fixed at 46.17%; and the water cut was set to 15-60%, the flow rate was fixed at 6.19 t / d, and the oil pressure was fixed at 6.56 MPa. Wellbore multiphase flow simulations were performed to obtain the pressure and temperature variation curves with well depth under different operating conditions. The pressure and temperature variation curves with well depth under different flow rates, oil pressures, and water cuts are shown below. Figure 4 , Figure 5 and Figure 6 .
[0045] S3: Using pressure as an intermediate variable, substitute the pressure values from the pressure-well depth curves calculated in step S2 under different operating conditions into the bubble point temperature-pressure curve and the wax precipitation temperature-pressure curve from step S1, respectively, to calculate the bubble point temperature-well depth curve and the wax precipitation temperature-well depth curve under different operating conditions. See [link to relevant documentation] for the bubble point temperature-well depth curve and the wax precipitation temperature-well depth curve under different flow rates, different oil pressures, and different water cuts. Figure 7 , Figure 8 and Figure 9 .
[0046] S4: The intersection of the temperature-well depth relationship curve with the bubble point temperature-well depth and wax precipitation temperature-well depth curves is the phase transition point.
[0047] S41: The intersection of the temperature-well depth curve obtained in step S2 and the bubble point temperature-well depth curve is obtained, which is the gas-liquid phase transition point. In this embodiment, the intersection of the temperature-well depth curve and the bubble point temperature-well depth curve of the target well under different flow rates, oil pressures and water cuts is calculated to obtain the gas-liquid phase transition point under different flow rates, oil pressures and water cuts.
[0048] S42: The intersection of the temperature-well depth curve obtained in step S2 and the wax precipitation temperature-well depth curve is obtained, which is the wax precipitation phase transition point. In this embodiment, the intersection of the temperature-well depth curve and the wax precipitation temperature-well depth curve of the target well under different flow rates, oil pressures, and water cuts is calculated to obtain the wax precipitation phase transition point under different flow rates, oil pressures, and water cuts.
[0049] Based on the above steps, the gas-liquid phase transition point and wax precipitation phase transition point were calculated under different flow rates, oil pressures, and water contents. When the flow rates were 2, 4, 6, 8, and 10 t / d, the oil pressure was fixed at 6.56 MPa, and the water content was fixed at 46.17%, the calculated gas-liquid phase transition point depths were 1618.81, 1646.25, 1688.68, 1725.29, and 1753.9 m, respectively, and the calculated wax precipitation phase transition point depths were 1218.56, 1190.64, 1160.96, 1132.69, and 1098.52 m, respectively. When the oil pressure is 2, 4, 6, 8, and 10 MPa, the flow rate is fixed at 6.19 t / d, and the water content is fixed at 46.17%, the calculated gas-liquid phase transition point depths are 2532.83, 2165.4, 1703.02, 1269.42, and 850.52 m, respectively, and the calculated wax precipitation phase transition point depths are 1098.52, 1098.52, 1098.52, 1118.58, and 1118.58 m, respectively. When the water content is 15%, 25%, 35%, 45%, and 60%, the flow rate is fixed at 6.19 t / d, and the oil pressure is fixed at 6.56 MPa. The calculated gas-liquid phase transition point depths are 2050.15, 1975.09, 1866.85, 1735.98, and 1532 m, respectively, and the calculated wax precipitation phase transition point depths are 1132.69, 1118.58, 1098.52, 1098.52, and 1070.38 m, respectively.
[0050] S5: Establish the formula for calculating the phase transition point and perform parameter regression calculations; specifically, this includes the following sub-steps:
[0051] S51: Integrate the data on the gas-liquid phase transition point depth and the wax precipitation phase transition point depth under different flow rates, oil pressures, and water contents calculated in step S4 to obtain a data table (Table 4) of gas-liquid phase transition point depth and wax precipitation phase transition point depth under different operating conditions. Analysis of the data in Table 4 shows that the gas-liquid phase transition point depth is mainly affected by three parameters: flow rate, water content, and oil pressure; the wax precipitation phase transition point depth is mainly affected by flow rate and water content, with little correlation to oil pressure. Furthermore, the integrated data shows that the gas-liquid phase transition point depth has a linear relationship with flow rate, oil pressure, and water content: as flow rate increases, the gas-liquid phase transition point depth increases; as oil pressure increases, the gas-liquid phase transition point depth decreases; as water content increases, the gas-liquid phase transition point depth decreases. The wax precipitation phase transition point depth has a linear relationship with flow rate and water content: as flow rate increases, the wax precipitation phase transition point depth decreases; as water content increases, the gas-liquid phase transition point depth increases. Therefore, in subsequent steps, a formula for calculating the phase transition point is established using a multivariate linear equation.
[0052] Table 4. Depth of gas-liquid phase transition and depth of wax precipitation phase transition under different operating conditions
[0053]
[0054] S52: Establish a formula for calculating the phase transition point using the form of multivariate linear equations;
[0055] Selecting flow velocity, oil pressure, and water content as independent variables, and the depth of the gas-liquid phase transition point as the dependent variable, the following multivariate linear equation for calculating the gas-liquid phase transition point is established:
[0056]
[0057] In the formula, The depth of the gas-liquid phase transition point, in meters (m). Flow rate, t / d; P is oil pressure, MPa; The moisture content is %.
[0058] Since the depth of the wax phase transition point is mainly affected by flow velocity and water content, and has little correlation with oil pressure, flow velocity and water content are selected as independent variables, and the depth of the wax phase transition point is selected as the dependent variable. The following multivariate linear equation is established to calculate the depth of the wax phase transition point:
[0059]
[0060] In the formula, The depth of the wax phase transition point, in meters (m). The velocity is t / d; The moisture content is %.
[0061] S53: Use the fitlm function in MATLAB to perform multiple linear regression and obtain the formula for calculating the phase transition point.
[0062] Multiple linear regression was performed using MATLAB software. The gas-liquid phase transition point depths under different operating conditions in Table 4 were imported into the software, and the `fitlm` function was used for multiple linear regression. The obtained constants were A = 3492.1101, B = 17.0063, C = -208.0827, and D = -12.1656. Therefore, the formula for calculating the gas-liquid phase transition point depth is:
[0063]
[0064] In the formula, The depth of the gas-liquid phase transition point, in meters (m). Oil pressure, MPa; The moisture content is %.
[0065] Substituting the flow rate, oil pressure, and water content data from Table 4 into the above calculation formula to calculate the gas-liquid phase transition point depth, the error was less than 5%. The calculation results are shown in Table 5. This proves that the regression model fits the calculation results data well and has high accuracy.
[0066] Table 5. Errors in the calculation results of the gas-liquid phase transition point depth
[0067]
[0068] Multiple linear regression was performed using MATLAB software. The wax precipitation phase transition point depths under different operating conditions in Table 4 were imported into the software, and the `fitlm` function was used for multiple linear regression. The obtained constants a and b were 1238.0837, -15.7609, and -0.4208, respectively. Therefore, the formula for calculating the wax precipitation phase transition point depth is:
[0069]
[0070] In the formula, The depth of the wax phase transition point, in meters (m). Oil pressure, MPa; The moisture content is %.
[0071] Substituting the flow rate, oil pressure, and water content data from Table 4 into the above calculation formula, the wax phase transition point depth was calculated. The calculation results are shown in Table 6, and the errors are all less than 5%, which proves that the regression model fits the calculation results data well and has high accuracy.
[0072] Table 6. Errors in the calculation results of the wax phase transition point depth
[0073]
[0074] S6: Predict the phase transition point under different production conditions using measured data;
[0075] By substituting the measured flow velocity, oil pressure, and water cut parameters of the target well into the formulas for calculating the gas-liquid phase transition point depth and the wax precipitation phase transition point depth, respectively, the predicted gas-liquid phase transition point depth and wax precipitation phase transition point depth under the current production state of the well can be calculated. Table 7 shows several sets of measured production data for the target well. Substituting the flow velocity, oil pressure, and water cut parameters into the formulas for calculating the gas-liquid phase transition point depth and the wax precipitation phase transition point depth, the calculation results are shown in Table 8.
[0076] Table 7 Measured Production Data of the Target Well
[0077]
[0078] Table 8 Calculation results of gas-liquid phase transition depth and wax precipitation phase transition depth
[0079]
[0080] Error calculations were performed between the gas-liquid phase transition point depths calculated in Table 8 and the measured gas-liquid phase transition point depths in Table 7. The calculated errors for the five sets of results were 3.5%, 3.6%, 4.5%, 2.2%, and 3.3%, respectively. Error calculations were also performed between the wax precipitation phase transition point depths calculated in Table 8 and the measured wax precipitation phase transition point depths in Table 7. The calculated errors for the five sets of results were 3.5%, 4.4%, 3.3%, 4%, and 2.1%, respectively, all within 5%. This demonstrates that the calculation formulas for the gas-liquid phase transition point depth and the wax precipitation phase transition point depth of the present invention have high accuracy.
[0081] In summary, the method for calculating the phase transition point of a CO2-enhanced oil reservoir wellbore provided by this invention, based on the gas-oil ratio, degassed crude oil, and associated gas sample data of the target well, uses the fluid numerical simulation software PVTsim to establish a formation fluid model and performs three-phase flash evaporation calculations to obtain bubble point curves and wax precipitation curves. Then, combining the wellbore structure and production parameters of the target well, a multiphase flow numerical model of the wellbore is established using the wellbore multiphase flow simulation software OLGA, and numerical simulation is performed using the controlled variable method to obtain wellbore temperature and pressure profiles under different flow velocities, oil pressures, and water cuts. Interpolation calculations are then performed using the bubble point curves and wax precipitation curves to obtain the gas-liquid phase transition point depth and the wax precipitation phase transition point depth corresponding to different operating conditions. Furthermore, using flow velocity, oil pressure, and water cut as independent variables, and the gas-liquid phase transition point depth and the wax precipitation phase transition point depth as dependent variables, multiple linear regression analysis is performed to obtain the calculation formulas for the gas-liquid phase transition point depth and the wax precipitation phase transition point depth. Finally, by substituting the measured production parameters into the calculation formulas for the gas-liquid phase transition point depth and the wax precipitation phase transition point depth, the depths of these two phase transition points can be calculated. Comparing the calculated results with the measured depths of the gas-liquid phase transition point and the wax precipitation phase transition point, the error is within 5%, indicating that the calculation method of this invention has high accuracy. Therefore, this invention transforms the complex numerical simulation process into a simple calculation formula that can be directly used on-site, enabling rapid prediction of the phase transition point in the wellbore of CO2-driven oil wells and providing a reliable basis for accurately formulating anti-wax measures.
[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for calculating the phase transition point of a wellbore in a CO2-driven oil reservoir, characterized in that, Includes the following steps: S1: Based on the formation fluid of the target well, calculate the bubble point temperature-pressure relationship curve and the wax precipitation temperature-pressure relationship curve; S2: Establish a multiphase flow model for the wellbore and perform numerical simulations, changing the flow velocity accordingly. Oil pressure P, water content Three parameters were used to calculate the temperature-depth and pressure-depth curves of the target well under different operating conditions; these different operating conditions included different flow velocities. Different oil pressures P and different water contents ; S3: Using pressure as an intermediate variable, substitute the pressure value of the pressure-well depth relationship curve in step S2 into the bubble point temperature-pressure relationship curve and the wax precipitation temperature-pressure relationship curve obtained in step S1 to obtain the bubble point temperature-well depth relationship curve and the wax precipitation temperature-well depth relationship curve under different working conditions. S4: The intersection of the temperature-well depth relationship curve in step S2 and the bubble point temperature-well depth relationship curve in step S3 is the gas-liquid phase transition point depth; the intersection of the temperature-well depth relationship curve in step S2 and the wax precipitation temperature-well depth relationship curve in step S3 is the wax precipitation phase transition point depth; finally, the gas-liquid phase transition point depth and the wax precipitation phase transition point depth under different operating conditions are obtained. S5: Using flow rate, oil pressure, and water content as independent variables, and the depth of gas-liquid phase transition point or the depth of wax precipitation phase transition point as dependent variables, establish multivariate linear equations for calculating the depth of gas-liquid phase transition point and the depth of wax precipitation phase transition point respectively. Specifically, based on the gas-liquid phase transition point depth data under different operating conditions, a gas-liquid phase transition point depth is established. With flow rate Oil pressure P, water content The functional relationship is used to obtain the depth of the gas-liquid phase transition point. Calculation formula; similarly, based on the wax phase transition point depth data under different working conditions, establish the wax phase transition point depth. With flow rate Oil pressure P, water content The functional relationship is used to obtain the depth of the wax phase transition point. Calculation formula; S6: Substitute the measured production condition parameters of the target well into the gas-liquid phase transition point depth. Calculation formula and wax phase transition point depth The calculation formula yields the depth of the gas-liquid phase transition point of the target well under the given production conditions. and wax phase transition point depth .
2. The method for calculating the phase transition point of a CO2-enhanced oil wellbore as described in claim 1, characterized in that, Step S1 specifically involves: establishing a formation fluid phase model for the target well, then setting the temperature and pressure range from the bottom of the well to the wellhead based on measured data to perform three-phase flash evaporation calculations, and obtaining the bubble point temperature-pressure relationship curve and wax precipitation temperature-pressure relationship curve of the target well under the production gas-oil ratio.
3. The method for calculating the phase transition point of a CO2-driven oil wellbore as described in claim 2, characterized in that, In step S1, the method for establishing the formation fluid phase model of the target well is as follows: based on the component data of the degassed crude oil and associated gas samples of the target well, the formation fluid phase model is obtained by using PVTsim software to reconstitute the active oil according to the gas-oil ratio.
4. The method for calculating the phase transition point of a CO2-driven oil wellbore as described in claim 3, characterized in that, In step S2, the method for establishing the wellbore multiphase flow model is as follows: First, a wellbore model is established based on the measured well inclination data and wellbore structure data of the target well. Then, based on the measured water cut data, the water cut is set in the formation fluid phase model established in step S1 and imported into the wellbore model. The production parameters of the wellbore model are set according to the measured production data to establish a multiphase flow model of the wellbore.