Shaft temperature and pressure prediction method and system for pressure control drilling

Abstract

The invention discloses a shaft temperature and pressure prediction method and system for pressure control drilling. The method comprises the steps that initial basic parameters used for predicting the shaft temperature and pressure are configured for a specified time step; according to the initial volume fraction of the free gas in the to-be-predicted shaft, firstly analyzing the fluid flow state change characteristics to obtain the predicted volume fraction of the free gas in the next time step, and then analyzing the precision of the current predicted volume fraction according to the initial volume fraction to obtain a first volume fraction meeting the precision requirement; predicted pressure is obtained through the first volume fraction, the precision of the current predicted pressure is analyzed according to the initial pressure, and first pressure meeting the precision requirement is obtained; and obtaining physical property parameters of each phase of fluid according to the first pressure so as to obtain a predicted temperature, analyzing the precision of the current predicted temperature according to the initial temperature so as to obtain a first temperature meeting the precision requirement, and obtaining a shaft temperature and pressure prediction result based on the first temperature. According to the method, the temperature and the pressure of the deepwater variable gradient pressure control drilling shaft are accurately predicted.

Description

Technical Field

[0001] The invention belongs to the field of petroleum drilling engineering, and in particular relates to a wellbore temperature and pressure prediction method and system for controlled pressure drilling. Background Art

[0002] With the continuous exploitation of high-quality oil and gas resources in shallow strata, deep strata and deep-sea oil and gas resources have become the key targets of future exploration and development. Due to the large changes in seawater depth and special temperature environment, the drilling process faces difficulties such as narrow safety density window and difficulty in wellbore pressure control. Complex underground conditions such as overflow, leakage, and coexistence of overflow and leakage have brought challenges to deepwater safe and efficient drilling.

[0003] At present, the pressure-controlled drilling technology is usually used to solve the problem of drilling in a narrow safety density window. The pressure-controlled drilling technology is centered on wellbore pressure control, and mainly includes bottom hole constant pressure controlled drilling technology and dual gradient drilling technology. The above two technologies have good application effects in the narrow safety density window of shallow sea and semi-deep water formations, but their applicability in deepwater drilling is still poor. In addition, when the above two technologies are implemented in deepwater drilling, the wellbore of deepwater drilling also has a complex wellbore structure.

[0004] Accurately predicting wellbore pressure is the basis of variable gradient controlled pressure drilling. Although the deepwater variable gradient controlled pressure drilling method can well adapt to the narrow safety density window of deepwater formations, the wellbore fluid flow law and wellbore pressure control method during implementation are very different from traditional controlled pressure drilling technology. Therefore, applying the traditional wellbore pressure calculation model and control method to deepwater variable gradient controlled pressure drilling will produce large errors. First, based on the problem that the flow conditions and flow laws of deepwater variable gradient controlled pressure drilling method are very different from those of conventional controlled pressure drilling, it is difficult to accurately predict the wellbore pressure during the implementation of deepwater variable gradient controlled pressure drilling method. Secondly, under normal working conditions, variable gradient controlled pressure drilling will cause variable mass flow of annular fluid and cause changes in annular temperature. The physical properties of drilling fluid are affected by the mutual coupling of wellbore temperature and pressure, resulting in complex flow conditions in the wellbore of variable gradient controlled pressure drilling, which greatly increases the difficulty of accurately predicting wellbore temperature and pressure. Finally, under gas invasion conditions, gas-liquid two-phase flow will occur in the wellbore. The complex flow conditions in the wellbore of variable gradient controlled pressure drilling add more boundary conditions to the gas-liquid two-phase flow problem, making the mechanism of gas-liquid two-phase flow more complicated. Unclear understanding of the mechanism of gas-liquid two-phase flow will directly affect the accurate prediction of wellbore pressure during gas invasion. Summary of the invention

[0005] In order to solve the above problems, an embodiment of the present invention provides a method for predicting wellbore temperature and pressure for managed pressure drilling, comprising: configuring initial basic parameters for predicting wellbore temperature and pressure for a specified time step; first analyzing the change characteristics of the fluid flow state according to the initial volume fraction of free gas in the wellbore to be predicted to obtain the predicted volume fraction of free gas in the next time step, and then analyzing the accuracy of the current predicted volume fraction according to the initial volume fraction, thereby adjusting the current initial volume fraction according to the analysis result, and re-obtaining the predicted volume fraction to obtain a first volume fraction that meets the accuracy requirement; using the first volume fraction to obtain a predicted pressure, and analyzing the current predicted pressure according to the initial pressure. The accuracy of the current predicted temperature is analyzed according to the initial temperature, and the current initial temperature is adjusted according to the analysis result, and then the current initial volume fraction is updated by using the first volume fraction, and the first volume fraction is re-obtained to obtain the first pressure that meets the accuracy requirement; the physical properties of the fluids of each phase are obtained according to the first pressure, and then the predicted temperature is obtained, and the accuracy of the current predicted temperature is analyzed according to the initial temperature, and then the current initial temperature is adjusted according to the analysis result, and then the current initial volume fraction is updated by using the re-obtained first volume fraction, and the current initial pressure is updated by using the first pressure, and the first pressure is re-obtained to obtain the first temperature that meets the accuracy requirement, based on which the wellbore temperature and pressure prediction result is obtained.

[0006] Preferably, the step of obtaining the predicted pressure using the first volume fraction includes: gridding the wellbore to be predicted to obtain a node combination, and obtaining the predicted pressure value of each node at different heights in sequence from the bottom of the well to the wellhead, thereby forming the predicted pressure using the set of predicted pressure values ​​corresponding to the node combination, wherein, in the grid division process, a dynamic hierarchical grid update method is used to determine whether the current division method matches the corresponding time step, and if it does not match, re-gridding.

[0007] Preferably, before obtaining the physical properties of each phase fluid according to the first pressure and then obtaining the predicted temperature, the wellbore temperature and pressure prediction method also includes: extracting the predicted pressure value of the node at the wellhead, and analyzing the accuracy of the current predicted pressure value according to the initial wellhead pressure value, so as to verify whether the current first pressure meets the accuracy requirement according to the analysis result, so as to obtain the physical properties of the each phase fluid and the predicted temperature using the verified first pressure, wherein, if the current first pressure fails to pass the verification, the initial basic parameters are reconfigured and the first pressure is obtained again to obtain a first pressure that has the ability to pass the verification.

[0008] Preferably, the step of analyzing the change characteristics of the fluid flow state according to the initial volume fraction of free gas in the wellbore to be predicted to obtain the predicted volume fraction of free gas in the next time step includes: determining the change characteristics of the fluid flow state based on the discretized dynamic model of the wellbore to be predicted in combination with the initial volume fraction; predicting the movement and dissolution characteristics of each phase of the fluid in the next time step according to the change characteristics of the fluid flow state, and then calculating the predicted volume fraction using a non-discretized dynamic model.

[0009] Preferably, the physical properties of the fluids of each phase include but are not limited to: density, viscosity, compressibility factor, surface tension, isobaric heat capacity and thermal conductivity; the movement and dissolution characteristics of the fluids of each phase include but are not limited to: apparent velocity of gas and liquid phases, interphase mass transfer rate, saturated solubility and actual solubility of the gas phase.

[0010] Preferably, in the step of analyzing the accuracy of the current predicted volume fraction according to the initial volume fraction of free gas in the wellbore to be predicted, and adjusting the current initial volume fraction according to the analysis result, it includes: calculating a first difference between the current predicted volume fraction and the initial volume fraction; comparing the first difference with a preset volume fraction threshold indicating that the volume fraction meets the accuracy requirement, thereby obtaining an analysis result of whether the current predicted volume fraction meets the accuracy requirement, wherein, if it does, the current predicted volume fraction is directly used as the first volume fraction; if it does not, the initial volume fraction is updated using the current predicted volume fraction, and the predicted volume fraction is re-obtained until a predicted volume fraction that meets the accuracy requirement is obtained and used as the first volume fraction.

[0011] Preferably, the step of obtaining the predicted pressure using the first volume fraction and analyzing the accuracy of the current predicted pressure, thereby adjusting the current initial pressure according to the analysis result, includes: calculating a second difference between the current predicted pressure and the initial pressure; comparing the second difference with a preset pressure threshold indicating that the pressure meets the accuracy requirement, thereby obtaining an analysis result of whether the current predicted pressure meets the accuracy requirement, wherein, if it does, the current predicted pressure is directly used as the first pressure; if it does not, the current predicted pressure is used to update the initial pressure, and the predicted pressure is obtained again until a predicted pressure that meets the accuracy requirement is obtained and used as the first pressure.

[0012] Preferably, in the step of obtaining the physical parameters of each phase fluid according to the first pressure, and then obtaining the predicted temperature, and analyzing the accuracy of the current predicted temperature, so as to adjust the current initial temperature according to the analysis result, it includes: calculating the third difference between the current predicted temperature and the initial temperature; comparing the third difference with a preset temperature threshold indicating that the temperature meets the accuracy requirement, so as to obtain an analysis result of whether the current predicted temperature meets the accuracy requirement, wherein, if it does, the current predicted temperature is directly used as the first temperature; if it does not, the initial temperature is updated using the current predicted temperature, and the predicted temperature is obtained again until a predicted temperature that meets the accuracy requirement is obtained and is used as the first temperature.

[0013] Preferably, the initial basic parameter is determined according to the parameter whose value change of the corresponding type reaches a stable state at the previous moment.

[0014] On the other hand, the present invention also provides a wellbore temperature and pressure prediction system for pressure-controlled drilling, the wellbore temperature and pressure prediction system comprising the following modules: an initial parameter configuration module, which is used to configure the initial basic parameters for predicting the wellbore temperature and pressure for a specified time step; a volume fraction acquisition module, which is used to first analyze the change characteristics of the fluid flow state according to the initial volume fraction of the free gas in the wellbore to be predicted, so as to obtain the predicted volume fraction of the free gas in the next time step, and then analyze the accuracy of the current predicted volume fraction according to the initial volume fraction, so as to adjust the current initial volume fraction according to the analysis result, and re-obtain the predicted volume fraction to obtain a first volume fraction that meets the accuracy requirements; a pressure acquisition module, which is used to obtain the predicted pressure using the first volume fraction. , and analyze the accuracy of the current predicted pressure according to the initial pressure, so as to adjust the current initial pressure according to the analysis result, and then update the current initial volume fraction using the first volume fraction, and re-obtain the first volume fraction to obtain the first pressure that meets the accuracy requirement; a temperature and pressure prediction module, which is used to obtain the physical properties of each phase fluid according to the first pressure, and then obtain the predicted temperature, and analyze the accuracy of the current predicted temperature according to the initial temperature, so as to adjust the current initial temperature according to the analysis result, and then update the current initial volume fraction using the re-obtained first volume fraction, and update the current initial pressure using the first pressure, and re-obtain the first pressure to obtain the first temperature that meets the accuracy requirement, based on which, the wellbore temperature and pressure prediction result is obtained.

[0015] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0016] The present invention discloses a method and system for predicting wellbore temperature and pressure for controlled pressure drilling. The method is based on the initial basic parameters (e.g., initial volume fraction, initial pressure, and initial temperature of free gas) configured for predicting wellbore temperature and pressure for the wellbore to be studied. The method adopts a cyclic iteration method to first analyze the characteristics of the change in fluid flow state to obtain the predicted volume fraction of free gas in the next time step, and then adjust the current initial volume fraction as needed to obtain the first volume fraction that meets the accuracy requirements; then, the predicted pressure is obtained using the first volume fraction, and the current initial pressure is adjusted as needed and the first volume fraction is obtained again to obtain the first pressure that meets the accuracy requirements; finally, the physical properties of each phase fluid are obtained according to the first pressure, and then the predicted temperature is obtained, and the current initial temperature is adjusted as needed and the first pressure is obtained again to obtain the first temperature that meets the accuracy requirements, based on which the wellbore temperature and pressure prediction results are obtained. The present invention realizes the accurate prediction of wellbore temperature and pressure under multiphase flow conditions of deepwater variable gradient controlled pressure drilling, and provides theoretical support for studying the changing laws of wellbore temperature, interphase mass transfer, and wellbore multiphase flow behavior during gas invasion in deepwater controlled pressure drilling, as well as early gas invasion detection and well control.

[0017] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 This is a step diagram of a method for predicting wellbore temperature and pressure for managed pressure drilling according to an embodiment of the present application.

[0020] Figure 2 It is an iterative analysis flow chart of a method for predicting wellbore temperature and pressure for managed pressure drilling according to an embodiment of the present application.

[0021] Figure 3 This is an example diagram of grid division for a method for predicting wellbore temperature and pressure for managed pressure drilling according to an embodiment of the present application.

[0022] Figure 4 This is a module block diagram of a wellbore temperature and pressure prediction system for managed pressure drilling according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0024] In addition, the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be performed in an order different from that shown here.

[0025] Accurately predicting wellbore pressure is the basis of variable gradient managed pressure drilling, but in the process of implementing deepwater variable gradient managed pressure drilling, the wellbore fluid flow law and wellbore pressure control method are very different from traditional managed pressure drilling technology. Therefore, applying traditional wellbore pressure calculation models and control methods to deepwater variable gradient managed pressure drilling will result in large errors.

[0026] Therefore, in order to solve the above problems, an embodiment of the present invention proposes a method and system for predicting wellbore temperature and pressure for controlled pressure drilling. The method is based on the initial basic parameters for predicting wellbore temperature and pressure configured for the wellbore to be studied (for example: the initial volume fraction of free gas, the initial pressure and the initial temperature), and adopts a cyclic iteration method. The method first analyzes the change characteristics of the fluid flow state to obtain the predicted volume fraction of free gas in the next time step, and then adjusts the current initial volume fraction as needed to obtain a first volume fraction that meets the accuracy requirements; then, the predicted pressure is obtained using the first volume fraction, and the current initial pressure is adjusted as needed and the first volume fraction is obtained again to obtain the first pressure that meets the accuracy requirements; finally, the physical properties of each phase fluid are obtained according to the first pressure, and then the predicted temperature is obtained, and the current initial temperature is adjusted as needed and the first pressure is obtained again to obtain the first temperature that meets the accuracy requirements, based on which, the wellbore temperature and pressure prediction result is obtained. The present invention realizes the accurate prediction of wellbore temperature and pressure under multiphase flow conditions of deepwater variable gradient controlled pressure drilling, and provides theoretical support for studying the changing laws of wellbore temperature, interphase mass transfer and wellbore multiphase flow behavior during gas invasion in deepwater controlled pressure drilling, as well as early gas invasion detection and well control.

[0027] Embodiment 1

[0028] Figure 1 This is a step diagram of the wellbore temperature and pressure prediction method for pressure-controlled drilling in an embodiment of the present application. Figure 1 To illustrate the various steps of this method.

[0029] like Figure 1As shown, in step S110, the initial basic parameters for predicting the wellbore temperature and pressure are configured for the specified time step. In the embodiment of the present application, the distribution characteristics of the free gas volume fraction, pressure and temperature of the wellbore to be predicted are specified for the initial time step at the time to be predicted, and the data of the free gas volume fraction, pressure and temperature at the corresponding position in the specified wellbore to be predicted are configured as the initial basic parameters for predicting the wellbore temperature and pressure.

[0030] In an embodiment of the present application, the initial basic parameters are determined according to the parameters (volume fraction, pressure and temperature) whose numerical changes of the corresponding type at the previous moment reach a stable state. That is to say, the parameters of the corresponding type that are stable at the previous moment are usually used as the initial volume fraction, initial pressure and initial temperature of the free gas at the current initial time step.

[0031] Figure 2 This is an iterative analysis flow chart of the wellbore temperature and pressure prediction method for managed pressure drilling in an embodiment of the present application. Figure 2 The iterative analysis process of the present invention is described in detail.

[0032] This embodiment adopts a cyclic iteration method to realize the temperature and pressure prediction of the wellbore to be predicted. First, the thermophysical parameters of the fluid in the wellbore at each time step are regarded as steady-state, and the temperature field and pressure field of each time step are solved separately; then, the wellbore temperature and pressure in different time steps are coupled through the thermophysical parameters of the gas phase and the liquid phase, thereby realizing the coupled acquisition of the wellbore temperature and pressure.

[0033] In step S120, based on the initial volume fraction of free gas in the wellbore to be predicted, the changing characteristics of the fluid flow state are first analyzed to obtain the predicted volume fraction of free gas in the next time step, and then the accuracy of the current predicted volume fraction is analyzed based on the initial volume fraction, so as to adjust the current initial volume fraction according to the analysis results, and re-obtain the predicted volume fraction to obtain a first volume fraction that meets the accuracy requirements.

[0034] Specifically, this embodiment uses the first volume fraction of free gas in the wellbore to be predicted at the current moment (moment t) as the initial volume fraction of free gas at the spatial node j in the wellbore to be predicted at the initial time step at the next moment (moment t+1). Among them, the initial volume fraction is related to the initial temperature and initial pressure below. The initial volume fraction can be obtained by calculating the physical properties of the gas and liquid phase fluids using the initial temperature and initial pressure. Afterwards, according to the initial volume fraction of the free gas, the discretized dynamic model (discretized hydrodynamic model and discretized thermodynamic model) used to analyze the change in the free gas flow state is combined to analyze the characteristics of the fluid flow state change, and the apparent velocity of each gas and liquid phase, the interphase mass transfer rate, the saturated solubility of the gas phase and the actual solubility are calculated. Further, the above calculation results are applied to the gas slip relationship model and the mass conservation equation (before discretization) to obtain the predicted volume fraction of free gas in the next time step. Next, the accuracy of the current predicted volume fraction is analyzed according to the initial volume fraction to check whether the current predicted volume fraction meets the prediction accuracy requirement. If it does, the current predicted volume fraction is directly used as the first volume fraction, or if it does not, the predicted volume fraction is re-obtained until the first volume fraction that meets the prediction accuracy requirement is obtained.

[0035] In the step of analyzing the accuracy of the current predicted volume fraction according to the initial volume fraction of free gas in the wellbore to be predicted, and adjusting the current initial volume fraction according to the analysis result, first calculate the first difference between the current predicted volume fraction and the initial volume fraction; then, compare the first difference with a preset volume fraction threshold indicating that the volume fraction meets the accuracy requirement, so as to obtain an analysis result of whether the current predicted volume fraction meets the accuracy requirement, wherein if it does, the current predicted volume fraction is directly used as the first volume fraction; if it does not, the initial volume fraction is updated using the current predicted volume fraction, and the predicted volume fraction is re-obtained until a predicted volume fraction that meets the accuracy requirement is obtained and is used as the first volume fraction.

[0036] Specifically, this embodiment first calculates the current predicted volume fraction With the initial volume fraction Next, compare whether the first difference is less than a preset volume fraction threshold ε indicating that the volume fraction meets the accuracy requirement. α If so, the current predicted volume fraction meets the accuracy requirement, and the current predicted volume fraction is directly used as the first volume fraction; if not, the current predicted volume fraction does not meet the accuracy requirement, and the current initial volume fraction is updated with the current predicted volume fraction, and then the predicted volume fraction is re-obtained and the prediction accuracy is determined, until the first volume fraction that meets the prediction accuracy requirement is obtained, and the first round of iterative prediction of the first volume fraction is ended.

[0037] In the step of analyzing the change characteristics of the fluid flow state according to the initial volume fraction of free gas in the wellbore to be predicted to obtain the predicted volume fraction of free gas in the next time step, the change characteristics of the fluid flow state are first determined based on the discretized dynamic model of the wellbore to be predicted in combination with the initial volume fraction; then, based on the change characteristics of the fluid flow state, the movement and dissolution characteristics of each phase of the fluid in the next time step are predicted, and then the predicted volume fraction is calculated using the non-discretized dynamic model, that is, the dynamic model before discretization.

[0038] The present invention is based on the interfacial mass transfer theory of sliding rising bubbles, and considers the annular variable mass flow caused by variable gradient parameters, and the heat transfer between the wellbore multiphase flow and the surrounding environment. The finite volume method is used to form the discretized dynamic model of the wellbore to be predicted, so as to analyze the thermodynamic behavior, interphase mass transfer rate and gas-liquid two-phase flow law of the deepwater variable gradient controlled pressure drilling wellbore based on the discretized dynamic model. Further, combined with the initial volume fraction, the purpose of determining the change characteristics of the fluid flow state is achieved. Therefore, this embodiment uses the finite volume method to numerically discretize the hydrodynamic model and thermodynamic model in the full transient non-isothermal multiphase flow model related to controlled pressure drilling, and obtains the discretized dynamic model of the wellbore to be predicted. Afterwards, the initial volume fraction is substituted into the discretized dynamic model of the wellbore to be predicted to analyze the change characteristics of the fluid flow state, thereby obtaining the fluid flow state of the next time step, and thus obtaining the motion and dissolution characteristics prediction results of each phase fluid. Next, the motion and dissolution characteristics prediction results of each phase fluid are substituted into the hydrodynamic model and thermodynamic model (non-discretized dynamic model) before numerical discretization to calculate the predicted volume fraction.

[0039] Further, in step S130, the predicted pressure is obtained using the first volume fraction, and the accuracy of the current predicted pressure is analyzed based on the initial pressure, so that the current initial pressure is adjusted according to the analysis result, and then the current initial volume fraction is updated using the first volume fraction, and the first volume fraction is obtained again to obtain a first pressure that meets the accuracy requirements.

[0040] Specifically, this embodiment uses the first pressure in the wellbore to be predicted at the current moment (t moment) as the initial pressure at the spatial node j in the wellbore to be predicted at the initial time step at the next moment (t+1 moment). Afterwards, based on the hybrid momentum conservation equation, the predicted pressure of the next time step is calculated using the first volume fraction. Next, the accuracy of the current predicted pressure is analyzed according to the initial pressure to check whether the current predicted pressure meets the prediction accuracy requirements, and if it meets the requirements, the current predicted pressure is directly used as the first pressure, or if it does not meet the requirements, the initial volume fraction at the end of the first round of first volume fraction iterative prediction is updated using the current first volume fraction, and the predicted pressure is obtained again until the first pressure that meets the prediction accuracy requirements is obtained.

[0041] In the step of obtaining the predicted pressure using the first volume fraction and analyzing the accuracy of the current predicted pressure, thereby adjusting the current initial pressure according to the analysis result, firstly calculate the second difference between the current predicted pressure and the initial pressure; then, compare the second difference with a preset pressure threshold indicating that the pressure meets the accuracy requirement, thereby obtaining an analysis result of whether the current predicted pressure meets the accuracy requirement, wherein, if it does, the current predicted pressure is directly used as the first pressure; if it does not, the initial pressure is updated using the current predicted pressure, and the predicted pressure is re-obtained until the predicted pressure that meets the accuracy requirement is obtained and is used as the first pressure.

[0042] Specifically, this embodiment first calculates the current predicted pressure With initial pressure Next, compare whether the second difference is less than the preset pressure threshold ε indicating that the pressure meets the accuracy requirement. P (For example: wellbore pressure under the coupling of temperature and pressure). If yes, the current predicted pressure meets the accuracy requirement, and the current predicted pressure is directly used as the first pressure; if no, the current predicted pressure does not meet the accuracy requirement, and the current initial pressure is updated with the current predicted pressure, and the initial volume fraction at the end of the first round of iterative prediction of the first volume fraction is updated with the current first volume fraction, and the second round of iterative prediction of the first volume fraction is completed. Then, according to the first volume fraction obtained by the iterative prediction of the first volume fraction in the second round, the predicted pressure is obtained again and the prediction accuracy is determined, until the first pressure that meets the prediction accuracy requirement is obtained, and the first round of iterative prediction of the first pressure is ended.

[0043] Further, in step S140, the physical properties of the fluids of each phase are obtained according to the first pressure, and then the predicted temperature is obtained, and the accuracy of the current predicted temperature is analyzed according to the initial temperature, so that the current initial temperature is adjusted according to the analysis result, and then the current initial volume fraction is updated using the regained first volume fraction, and the current initial pressure is updated using the first pressure, and the first pressure is regained to obtain a first temperature that meets the accuracy requirements, based on which the wellbore temperature and pressure prediction result is obtained.

[0044] Specifically, this embodiment uses the first temperature in the wellbore to be predicted at the current moment (t moment) as the initial temperature at the spatial node j of the position node in the wellbore to be predicted at the initial time step at the next moment (t+1 moment). Afterwards, the physical properties of the gas and liquid phase fluids are calculated using the first pressure combined with the initial temperature, thereby updating the physical properties of the gas and liquid phase fluids with respect to the initial temperature and initial pressure, and then obtaining the predicted temperature for the next time step. Next, the accuracy of the current predicted temperature is analyzed according to the initial temperature to check whether the current predicted temperature meets the prediction accuracy requirements, and if it does, the current predicted temperature is directly used as the first temperature, or if it does not, the current first volume fraction is used to update the initial volume fraction at the end of the second round of first volume fraction iterative prediction, and the current first pressure is used to update the initial pressure at the end of the first round of first pressure iterative prediction, and the predicted temperature is obtained again until the first temperature that meets the prediction accuracy requirements is obtained. Based on this, the thermophysical properties of the fluid at each time step are regarded as steady-state, so that the first temperature that meets the prediction accuracy requirements and the latest first pressure that meets the prediction accuracy requirements used to obtain the first temperature are used as the temperature and pressure of the initial time step at the time to be predicted, so as to obtain the temperature field and pressure field of each time step separately. Based on this, the temperature and pressure of subsequent time steps are continued, and finally the temperatures and pressures corresponding to different time steps at the time to be predicted are integrated respectively to obtain the wellbore temperature and pressure prediction results.

[0045] In the step of obtaining the physical parameters of each phase fluid according to the first pressure, and then obtaining the predicted temperature, and analyzing the accuracy of the current predicted temperature, so as to adjust the current initial temperature according to the analysis result, first calculate the third difference between the current predicted temperature and the initial temperature; then, compare the third difference with the preset temperature threshold indicating that the temperature meets the accuracy requirement, so as to obtain the analysis result of whether the current predicted temperature meets the accuracy requirement, wherein, if it does, directly use the current predicted temperature as the first temperature; if it does not, use the current predicted temperature to update the initial temperature, and re-obtain the predicted temperature until the predicted temperature that meets the accuracy requirement is obtained and used as the first temperature.

[0046] Specifically, this embodiment first calculates the current predicted temperature With initial temperature Next, compare whether the third difference is less than a preset temperature threshold ε indicating that the temperature meets the accuracy requirement. T(For example: the fluid temperature at the inlet of the drill string). If so, the current predicted temperature meets the accuracy requirements, and the current predicted temperature is directly used as the first temperature; if not, the current predicted temperature does not meet the accuracy requirements, the current initial temperature is updated with the current predicted temperature, and the current first volume fraction is used to update the initial volume fraction at the end of the second round of iterative prediction of the first volume fraction, and the third round of iterative prediction of the first volume fraction is completed, and the current first pressure is used to update the initial pressure at the end of the first round of iterative prediction of the first pressure, and the second round of iterative prediction of the first pressure is completed. Then, according to the first volume fraction obtained by the third round of iterative prediction of the first volume fraction and the first pressure obtained by the second round of iterative prediction of the first pressure, the predicted temperature is re-obtained and the prediction accuracy is determined, until the first temperature that meets the prediction accuracy requirements is obtained, and the first round of iterative prediction of the first temperature is ended.

[0047] In the step of obtaining the predicted pressure using the first volume fraction, the wellbore to be predicted is gridded to obtain a node combination, and the predicted pressure value of each node at different heights is obtained in sequence from the bottom of the well to the wellhead, thereby forming the predicted pressure using the set of predicted pressure values ​​of the corresponding node combination. In the gridding process, a dynamic hierarchical grid updating method is used to determine whether the current division method matches the corresponding time step, and if it does not match, the grid is re-divided.

[0048] In the embodiment of the present application, the wellbore to be predicted and its surrounding environment are gridded and discretized in time and space to achieve independent acquisition of transient temperature and pressure of the wellbore. In the gridding process, a uniform gridding method is used in the axial direction of the wellbore, and a non-uniform gridding method is used in the radial direction around the wellbore wall. At the same time, a dynamic hierarchical grid updating method is used to determine whether the current division method matches the corresponding time step (i.e., whether the grid distribution state can meet the requirements of calculating transient temperature and pressure in the corresponding time step), so as to determine whether the axial grid of each time step needs to be re-divided, and if it does not match, the grid is re-divided to obtain a grid distribution state that can meet the requirements of calculating transient temperature and pressure in the corresponding time step.

[0049] Figure 3 This is an example diagram of the grid division of the wellbore temperature and pressure prediction method for pressure-controlled drilling in the embodiment of the present application. Figure 3 The meshing method shown in the figure is used to implement meshing. Figure 3 In the formula, i and j represent directions, z and r represent distances, P, W, N, E, and S represent nodes of the control volumes, w, n, e, and s represent interfaces between control volumes, Δr and Δz represent the lengths of each control volume in the i and j directions, and δz represents the lengths of each control volume in the i and j directions. n ,δz s ,δr w,δr e They represent the distances between node P and node N, between node P and node S, between node P and node W, and between node P and node E respectively.

[0050] Next, after completing the grid division of the wellbore to be predicted, a node combination consisting of all grids is obtained. After that, the bottom of the wellbore is recorded as the spatial node j=0, and the first pressure is divided into the bottom hole pressure and the remaining pressures. In this way, the bottom hole pressure in the wellbore to be predicted at the current moment (t moment) is used as the initial pressure at the spatial node j=0 in the wellbore to be predicted at the initial time step of the next moment (t+1 moment). After that, the gas invasion rate and the thermal physical parameters of each phase of gas and liquid are calculated based on the gas invasion rate model and the gas-liquid physical parameter model, and the predicted pressure of the node at the next time step is calculated. Next, in order from the bottom of the well to the wellhead, the initial pressures at the spatial nodes j = 0, 1, 2, ..., N are obtained in sequence, and in a prediction method similar to the aforementioned first pressure, first temperature or first volume fraction, the wellhead back pressure is used as the preset wellhead pressure threshold indicating that the wellhead pressure meets the accuracy requirement, and the preset bottom hole pressure threshold indicating that the bottom hole pressure meets the accuracy requirement is determined with the axial gradient of the bottom hole annulus temperature as 0. The pressure is iteratively predicted for each spatial node from a spatial perspective to obtain the predicted pressure value corresponding to each spatial node, thereby obtaining a set of predicted pressure values ​​to form a predicted pressure.

[0051] Before obtaining the physical properties of each phase fluid according to the first pressure and then obtaining the predicted temperature, the present embodiment further extracts the predicted pressure value of the node at the wellhead, and analyzes the accuracy of the current predicted pressure value according to the initial wellhead pressure value, thereby verifying whether the current first pressure meets the accuracy requirement based on the analysis result, so as to obtain the physical properties and predicted temperature of each phase fluid using the verified first pressure, wherein, if the current first pressure fails to pass the verification, the initial basic parameters are reconfigured and the first pressure is obtained again to obtain a first pressure capable of passing the verification.

[0052] Specifically, in this embodiment, the wellhead pressure value P of the preset spatial node j=N is c , first extract the predicted pressure value at the spatial node j=N in the current first pressure Next, according to the accuracy analysis method similar to the aforementioned first pressure, first temperature or first volume fraction, it is determined whether the predicted pressure value at the current spatial node j=N meets the accuracy requirements. Combined with the characteristics of the first pressure obtained based on the iterative prediction of the bottom hole pressure, it is possible to achieve the purpose of verifying whether the current first pressure meets the accuracy requirements. Accordingly, the physical parameters and predicted temperature of each phase fluid are obtained by using the verified first pressure, which effectively guarantees the accuracy of the obtained wellbore temperature and pressure prediction results. If the current first pressure fails to pass the verification, it is necessary to reconfigure the initial basic parameters and repeat the first pressure acquisition steps until the first pressure with the ability to pass the verification is obtained. The physical parameters and predicted temperature of the corresponding phase fluid can be calculated. It can be seen that this embodiment adopts a double-loop iteration method, which iterates the first pressure, the first temperature and the first volume fraction on the one hand, and iterates the pressure of each spatial node on the other hand, which effectively improves the accuracy of the wellbore temperature and pressure prediction results.

[0053] In a specific embodiment of the present application, the physical parameters of each phase fluid include but are not limited to: density, viscosity, compressibility, surface tension, isobaric heat capacity and thermal conductivity. The movement and dissolution characteristics of each phase fluid include but are not limited to: the apparent velocity of each phase of gas and liquid, the interphase mass transfer rate, the saturated solubility and actual solubility of the gas phase.

[0054] In a specific embodiment of the present application, by obtaining the actual basic multiphase flow parameters of the construction site in the wellbore pressure-controlled drilling calculation to be predicted, and utilizing the full transient non-isothermal multiphase flow model related to pressure-controlled drilling, the calculation of the basic multiphase flow parameters (intermediate parameters) used to predict the wellbore temperature and pressure is realized.

[0055] In a specific embodiment of the present application, the full transient non-isothermal multiphase flow model includes, but is not limited to: a gas-liquid phase mass transfer rate model, a hydrodynamic model including a mass conservation equation and a momentum conservation equation, and a thermodynamic model. Intermediate parameters include, but are not limited to: water depth, well depth, drilling fluid density, drilling fluid viscosity, pump speed, temperature, reservoir permeability, mechanical drilling speed, wellbore structure parameters, seawater density, rock density, and thermal conductivity and specific heat of drilling fluid, seawater, rock, steel pipe, cement sheath and gas.

[0056] Next, the calculation model involved in this embodiment is described with examples.

[0057] First, the gas-liquid interphase mass transfer rate model includes the interphase mass transfer rate under laminar flow conditions and the interphase mass transfer rate under turbulent flow conditions. The interphase mass transfer rate under laminar flow conditions and the interphase mass transfer rate under turbulent flow conditions are respectively expressed by the following expressions:

[0058]

[0059]

[0060] in, represents the mass transfer rate between gas and liquid phases, N b It represents the number density of bubbles per unit volume in the wellbore, M g Denotes the mass transfer coefficient, D go represents the gas diffusion coefficient, C inf represents the gas concentration at the gas-liquid interface, C b represents the gas concentration in the oil-based drilling fluid, θ b It represents the angle of the bubble moving clockwise from the vertical diameter upward to the vertical diameter downward, v ∞ represents the slip rate, R b represents the bubble radius, f b-b represents the interaction coefficient between bubbles, β represents the coefficient, ε represents the energy dissipation per unit mass, and ν L represents kinematic viscosity, λ1 represents turbulence scale, λ 0 represents the Kolmogorov turbulence scale.

[0061] Next, the mass conservation equations in the hydrodynamic model (before discretization) use the following expressions to represent the free gas, liquid, and dissolved gas in the control volume unit:

[0062]

[0063]

[0064]

[0065] Wherein, t represents the operation time, z represents the spatial length, A represents the cross-sectional area, ρ represents the density, α represents the volume fraction, v represents the flow velocity, and the subscripts g, L, and s represent the mixed fluid of free gas, drilling fluid and hollow sphere, and hollow sphere, respectively. Indicates the gas intrusion rate, represents the hollow ball transfer rate, x sol Indicates the mass fraction of dissolved gas in drilling fluid.

[0066] The momentum conservation equation hydrodynamic model (before discretization) is expressed as follows:

[0067]

[0068] Where P represents the wellbore pressure, i represents different components, f represents the friction coefficient, d c represents the equivalent diameter, G represents the acceleration due to gravity, θ jx Indicates the well inclination angle.

[0069] The thermodynamic model (before discretization) includes the transient heat transfer model in the annulus and the transient heat transfer model in the drill string. The transient heat transfer model in the annulus and the transient heat transfer model in the drill string are respectively expressed by the following expressions:

[0070]

[0071]

[0072] Among them, λ m represents the thermal conductivity of the mixed fluid, C pi represents the specific heat of component i, C pg , C pL , C ps represents the specific heat of free gas, liquid, and dissolved gas, T represents temperature, and r represents the radius of the drill string. represents the average temperature of the formation gas, Indicates the average pressure of formation gas, C J represents the Joule Thomson coefficient, T p represents the fluid temperature in the drill string, A p represents the cross-sectional area of ​​the drill string, P p represents the pressure in the drill string, λ L It represents the thermal conductivity of the mixed fluid of drilling fluid and hollow sphere.

[0073] In addition, the full transient non-isothermal multiphase flow model also includes the interphase slip relationship (gas slip relationship model), flow friction coefficient, gas invasion rate, overflow rate, convection heat transfer coefficient, fluid PVT equation, gas critical temperature equation, gas critical pressure equation and formation temperature field equation, which are expressed by the following expressions:

[0074] v g =c 0 (α g v g +α L v L )+v ∞ (9)

[0075]

[0076]

[0077]

[0078]

[0079] ρ=f(P,T,i) (14)

[0080] T gTc =f(P,T,i) (15)

[0081] P gPc =f(P,T,i) (16)

[0082] T e =f(T 0 ,h,ΔT) (17)

[0083] Among them, c 0 Re represents the gas distribution coefficient, Re m represents the Reynolds number of the mixed fluid, Δ represents the roughness, Λ represents the correction coefficient, and d bo Indicates the outer diameter of the annulus, d po represents the outer diameter of the drill string, K represents the reservoir permeability, h represents the reservoir opening thickness, P e Reservoir pressure, P b represents the bottom hole pressure, j represents the grid number, Z represents the gas compression factor under ground conditions, and Z e represents the gas compressibility factor under reservoir conditions, C t represents the total compressibility, μ represents the viscosity, and μ g represents the free gas viscosity, T e Reservoir temperature, C T Represents the temperature correction coefficient, V pg Indicates the overflow volume, B m Denotes the mixture volume factor, B L represents the liquid volume coefficient, H represents the well depth, Nu represents the Nusselt number, Pr represents the Prandtl number, Re represents the Reynolds number, r w represents the radius, T gPe represents the free gas temperature, P gPe represents the free air pressure, T e represents the formation temperature, T 0 represents the initial temperature, and ΔT represents the temperature change.

[0084] Embodiment 2

[0085] Based on the wellbore temperature and pressure prediction method for managed pressure drilling described in the first embodiment, an embodiment of the present invention further provides a wellbore temperature and pressure prediction system for managed pressure drilling. Figure 4 This is a module block diagram of a wellbore temperature and pressure prediction system for managed pressure drilling according to an embodiment of the present application.

[0086] like Figure 4As shown, the wellbore temperature and pressure prediction system for pressure-controlled drilling in the embodiment of the present invention includes: an initial parameter configuration module 41, a volume fraction acquisition module 42, a pressure acquisition module 43 and a temperature and pressure prediction module 44. Specifically, the initial parameter configuration module 41 is implemented according to the method described in the above step S110, and is configured to configure the initial basic parameters for predicting the wellbore temperature and pressure for a specified time step; the volume fraction acquisition module 42 is implemented according to the method described in the above step S120, and is configured to first analyze the change characteristics of the fluid flow state according to the initial volume fraction of the free gas in the wellbore to be predicted, so as to obtain the predicted volume fraction of the free gas in the next time step, and then analyze the accuracy of the current predicted volume fraction according to the initial volume fraction, so as to adjust the current initial volume fraction according to the analysis result, and re-obtain the predicted volume fraction to obtain a first volume fraction that meets the accuracy requirement; the pressure acquisition module 43 is implemented according to the method described in the above step S130, and is configured to obtain the predicted pressure using the first volume fraction, and The accuracy of the current predicted pressure is analyzed according to the initial pressure, and the current initial pressure is adjusted according to the analysis result. Then, the current initial volume fraction is updated using the first volume fraction, and the first volume fraction is re-obtained to obtain the first pressure that meets the accuracy requirement. The temperature and pressure prediction module 44 is implemented according to the method described in the above step S140, and is configured to obtain the physical properties of each phase fluid according to the first pressure, and then obtain the predicted temperature, and analyze the accuracy of the current predicted temperature according to the initial temperature, so as to adjust the current initial temperature according to the analysis result, and then the current initial volume fraction is updated using the re-obtained first volume fraction, and the current initial pressure is updated using the first pressure, and the first pressure is re-obtained to obtain the first temperature that meets the accuracy requirement, based on which the wellbore temperature and pressure prediction result is obtained.

[0087] The present invention proposes a method and system for predicting wellbore temperature and pressure for controlled pressure drilling. The method is based on the initial basic parameters (e.g., initial volume fraction, initial pressure, and initial temperature of free gas) configured for the wellbore to be studied, and adopts a cyclic iteration method to first analyze the characteristics of the change in fluid flow state to obtain the predicted volume fraction of free gas in the next time step, and then adjust the current initial volume fraction as needed to obtain the first volume fraction that meets the accuracy requirements; then, the predicted pressure is obtained using the first volume fraction, and the current initial pressure is adjusted as needed and the first volume fraction is obtained again to obtain the first pressure that meets the accuracy requirements; finally, the physical properties of each phase fluid are obtained according to the first pressure, and then the predicted temperature is obtained, and the current initial temperature is adjusted as needed and the first pressure is obtained again to obtain the first temperature that meets the accuracy requirements, based on which the prediction result of wellbore temperature and pressure is obtained. The present invention realizes the accurate prediction of wellbore temperature and pressure under multiphase flow conditions of deepwater variable gradient controlled pressure drilling, and provides theoretical support for studying the changing laws of wellbore temperature, interphase mass transfer, and wellbore multiphase flow behavior during gas invasion in deepwater controlled pressure drilling, as well as early gas invasion detection and well control. The present invention also promotes the understanding of the evolution law of multiphase flow in variable gradient controlled pressure drilling wells and the law of change of wellbore pressure, and lays a theoretical foundation for the optimization design of hydraulic parameters for gas invasion control. Therefore, by accurately predicting the wellbore gas-liquid two-phase flow behavior and the law of change of wellbore pressure, gas invasion can be discovered earlier, thereby reasonably controlling the wellbore pressure and effectively avoiding the occurrence of serious accidents such as blowouts.

[0088] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0089] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0090] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0091] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for predicting wellbore temperature and pressure for managed pressure drilling, It is characterized in that include: Configure the initial basic parameters for predicting wellbore temperature and pressure for a specified time step; According to the initial volume fraction of free gas in the wellbore to be predicted, the fluid flow state change characteristics are first analyzed to obtain the predicted volume fraction of free gas in the next time step, and then the accuracy of the current predicted volume fraction is analyzed according to the initial volume fraction, so as to adjust the current initial volume fraction according to the analysis result, and re-obtain the predicted volume fraction to obtain a first volume fraction that meets the accuracy requirement; Obtaining a predicted pressure using the first volume fraction, and analyzing the accuracy of the current predicted pressure according to the initial pressure, thereby adjusting the current initial pressure according to the analysis result, and then updating the current initial volume fraction using the first volume fraction, and re-obtaining the first volume fraction to obtain a first pressure that meets the accuracy requirement; The physical properties of each phase fluid are obtained according to the first pressure, and then the predicted temperature is obtained. The accuracy of the current predicted temperature is analyzed according to the initial temperature, so that the current initial temperature is adjusted according to the analysis result. Thereafter, the current initial volume fraction is updated using the regained first volume fraction, and the current initial pressure is updated using the first pressure, and the first pressure is regained to obtain a first temperature that meets the accuracy requirements. Based on this, the wellbore temperature and pressure prediction result is obtained.

2. The method for predicting wellbore temperature and pressure according to claim 1, It is characterized in that The step of obtaining the predicted pressure by using the first volume fraction includes: The wellbore to be predicted is gridded to obtain a node combination, and the predicted pressure value of each node at different heights is obtained in sequence from the bottom of the well to the wellhead, thereby forming the predicted pressure using the predicted pressure value set corresponding to the node combination, wherein, During the meshing process, a dynamic hierarchical mesh updating method is used to determine whether the current meshing method matches the corresponding time step, and if it does not match, the meshing is re-performed.

3. The method for predicting wellbore temperature and pressure according to claim 2, It is characterized in that Before obtaining the physical property parameters of each phase fluid according to the first pressure and then obtaining the predicted temperature, the wellbore temperature and pressure prediction method further includes: The predicted pressure value of the node at the wellhead is extracted, and the accuracy of the current predicted pressure value is analyzed according to the initial wellhead pressure value, so as to verify whether the current first pressure meets the accuracy requirement according to the analysis result, so as to obtain the physical properties of the fluids of each phase and the predicted temperature by using the verified first pressure, wherein, if the current first pressure fails to pass the verification, the initial basic parameters are reconfigured and the first pressure is obtained again to obtain a first pressure capable of passing the verification.

4. The method for predicting wellbore temperature and pressure according to any one of claims 1 to 3, It is characterized in that The step of analyzing the change characteristics of the fluid flow state according to the initial volume fraction of free gas in the wellbore to be predicted to obtain the predicted volume fraction of free gas in the next time step includes: Based on the discretized dynamic model of the wellbore to be predicted and in combination with the initial volume fraction, determining the change characteristics of the fluid flow state; According to the change characteristics of the fluid flow state, the movement and dissolution characteristics of each phase of the fluid in the next time step are predicted, and then the predicted volume fraction is calculated using a non-discrete dynamic model.

5. The method for predicting wellbore temperature and pressure according to claim 4, It is characterized in that The physical properties of each phase fluid include but are not limited to: density, viscosity, compressibility, surface tension, isobaric heat capacity and thermal conductivity; The movement and dissolution characteristics of the fluids of each phase include, but are not limited to: the superficial velocity of the gas and liquid phases, the mass transfer rate between the phases, the saturated solubility and actual solubility of the gas phase.

6. The method for predicting wellbore temperature and pressure according to any one of claims 1 to 5, It is characterized in that The step of analyzing the accuracy of the current predicted volume fraction according to the initial volume fraction of free gas in the wellbore to be predicted, thereby adjusting the current initial volume fraction according to the analysis result, includes: Calculating a first difference between the current predicted volume fraction and the initial volume fraction; The first difference is compared with a preset volume fraction threshold indicating that the volume fraction meets the accuracy requirement, so as to obtain an analysis result of whether the current predicted volume fraction meets the accuracy requirement, wherein if it does, the current predicted volume fraction is directly used as the first volume fraction; if it does not, the initial volume fraction is updated using the current predicted volume fraction, and the predicted volume fraction is re-obtained until a predicted volume fraction that meets the accuracy requirement is obtained and is used as the first volume fraction.

7. The method for predicting wellbore temperature and pressure according to any one of claims 1 to 6, It is characterized in that The step of obtaining the predicted pressure by using the first volume fraction and analyzing the accuracy of the current predicted pressure, thereby adjusting the current initial pressure according to the analysis result, includes: calculating a second difference between the current predicted pressure and the initial pressure; The second difference is compared with a preset pressure threshold indicating that the pressure meets the accuracy requirement, so as to obtain an analysis result of whether the current predicted pressure meets the accuracy requirement, wherein, if it does, the current predicted pressure is directly used as the first pressure; if it does not, the initial pressure is updated using the current predicted pressure, and the predicted pressure is re-obtained until a predicted pressure that meets the accuracy requirement is obtained and is used as the first pressure.

8. The method for predicting wellbore temperature and pressure according to any one of claims 1 to 7, It is characterized in that The step of obtaining the physical property parameters of each phase fluid according to the first pressure, thereby obtaining the predicted temperature, and analyzing the accuracy of the current predicted temperature, thereby adjusting the current initial temperature according to the analysis result, includes: calculating a third difference between the current predicted temperature and the initial temperature; The third difference is compared with a preset temperature threshold indicating that the temperature meets the accuracy requirement, thereby obtaining an analysis result of whether the current predicted temperature meets the accuracy requirement, wherein, if it does, the current predicted temperature is directly used as the first temperature; if it does not, the initial temperature is updated using the current predicted temperature, and the predicted temperature is re-obtained until a predicted temperature that meets the accuracy requirement is obtained and is used as the first temperature.

9. The method for predicting wellbore temperature and pressure according to any one of claims 1 to 8, It is characterized in that The initial basic parameters are determined according to the parameters whose corresponding type value changes at the previous moment reach a stable state.

10. A wellbore temperature and pressure prediction system for managed pressure drilling, It is characterized in that The wellbore temperature and pressure prediction system includes the following modules: An initial parameter configuration module, which is used to configure the initial basic parameters for predicting wellbore temperature and pressure for a specified time step; A volume fraction acquisition module is used to first analyze the change characteristics of the fluid flow state according to the initial volume fraction of free gas in the wellbore to be predicted, so as to obtain the predicted volume fraction of free gas in the next time step, and then analyze the accuracy of the current predicted volume fraction according to the initial volume fraction, so as to adjust the current initial volume fraction according to the analysis result, and re-obtain the predicted volume fraction to obtain a first volume fraction that meets the accuracy requirement; a pressure acquisition module, configured to obtain a predicted pressure using the first volume fraction, and analyze the accuracy of the current predicted pressure according to the initial pressure, thereby adjusting the current initial pressure according to the analysis result, and then updating the current initial volume fraction using the first volume fraction, and re-obtaining the first volume fraction to obtain a first pressure that meets the accuracy requirement; The temperature and pressure prediction module is used to obtain the physical properties of each phase fluid according to the first pressure, and then obtain the predicted temperature, and analyze the accuracy of the current predicted temperature according to the initial temperature, so as to adjust the current initial temperature according to the analysis result, and then update the current initial volume fraction using the regained first volume fraction, and update the current initial pressure using the first pressure, and regain the first pressure to obtain the first temperature that meets the accuracy requirements, based on which, the wellbore temperature and pressure prediction result is obtained.

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