A method and system for predicting wellbore temperature and pressure field of deep sea ultra-shallow gas layer under gas invasion condition

Abstract

The present application relates to the technical field of oil and gas drilling engineering, and in particular to a method and system for predicting wellbore temperature and pressure field of deep-sea ultra-shallow gas layer under gas invasion condition. The method comprises the following steps: obtaining drilling parameters, wherein the drilling parameters include wellbore geometric parameters, drilling fluid parameters, working condition parameters and gas invasion parameters; based on the drilling parameters, establishing a temperature field model and a pressure field model of the wellbore, wherein the temperature field model couples the energy conservation of drill string fluid, annular fluid and pipe wall, the pressure field model is established based on mass conservation and momentum conservation, and the drill string single-phase flow region and the annular multiphase flow region are distinguished; solving the temperature field model and the pressure field model to obtain the temperature distribution and pressure distribution of the wellbore along the depth direction. The present application improves the accuracy of temperature and pressure field prediction under complex drilling conditions by finely coupling the heat exchange process and distinguishing different flow regions.

Description

Technical Field

[0001] This invention relates to the field of oil and gas drilling engineering technology, specifically to a method and system for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas invasion conditions. Background Technology

[0002] In oil and gas drilling engineering, accurately predicting the temperature and pressure distribution along the depth direction of the wellbore is crucial for drilling design, safety control, and risk assessment. Existing wellbore temperature and pressure field prediction technologies are typically based on simplified physical models, which have limited accuracy under complex drilling conditions.

[0003] While some existing methods have established temperature and pressure field models for the wellbore, these temperature field models may not adequately couple the energy conservation of the drill string fluid, annular fluid, and tubing wall, leading to inaccurate simulations of heat exchange processes. Furthermore, these pressure field models often fail to clearly distinguish the flow characteristics of the drill string's single-phase flow region from the annular multiphase flow region, and do not fully consider the influence of gas intrusion parameters. This results in significant deviations between predicted results and actual operating conditions in drilling scenarios with gas intrusion risks, such as deep-sea ultra-shallow gas layers. These technical deficiencies limit the effective application of wellbore temperature and pressure field prediction methods in complex, high-risk drilling operations. Summary of the Invention

[0004] To address the shortcomings of existing methods and the needs of practical applications, this invention provides a method for predicting the temperature and pressure field of deep-sea ultra-shallow gas layer wellbores under gas intrusion conditions, comprising the following steps: Drilling parameters are obtained, including wellbore geometry parameters, drilling fluid parameters, operating condition parameters, and gas intrusion parameters. Based on these drilling parameters, a temperature field model and a pressure field model of the wellbore are established. The temperature field model couples the energy conservation of the drill string fluid, the annular fluid, and the pipe wall. The pressure field model is established based on the conservation of mass and momentum, and distinguishes between the single-phase flow region of the drill string and the multiphase flow region of the annulus. The temperature field model and the pressure field model are solved to obtain the temperature and pressure distribution of the wellbore along the depth direction.

[0005] Optionally, the wellbore geometry parameters include at least well depth, seawater depth, and tubing diameter; the drilling fluid parameters include at least drilling fluid density and drilling fluid specific heat capacity; the operating condition parameters include at least drilling fluid discharge rate, circulation time, and inlet temperature; and the gas intrusion parameters include at least gas intrusion location and gas intrusion volumetric flow rate.

[0006] Optionally, the temperature field model is established, including: Based on the wellbore geometry parameters and the seawater depth in the operating parameters, the temperature gradient of the external environment along the depth direction is determined, and the external environment includes the seawater section and the formation section; based on the temperature gradient and the drilling parameters, energy conservation control equations for the drill string fluid, the annular fluid, and the pipe wall are constructed respectively.

[0007] Optionally, determining the temperature gradient of the external environment of the wellbore along the depth direction includes: For the depth range of the seawater section, the temperature is calculated using a preset seawater temperature distribution function; for the depth range of the strata section, the temperature is calculated using a linear geothermal gradient formula.

[0008] Optionally, the energy conservation governing equations are constructed as follows: The drill string fluid energy control items include heat storage items, axial convection items, and pipe wall heat exchange items; the annular fluid energy control items include heat storage items, backflow convection items, pipe wall heat exchange items, and external environment heat exchange items; the pipe wall energy control items include heat storage items, axial heat conduction items, and convective heat exchange items with the drill string fluid and annular fluid, respectively.

[0009] Optionally, solving the temperature field model includes: The energy conservation control equations for the drill string fluid, annular fluid, and pipe wall are discretized using a fully implicit differential discretization method, with the axial convection term discretized using an upwind discretization method. The discretized equations are then constructed into a sparse linear system of equations and solved.

[0010] Optionally, establishing the pressure field model includes: For the single-phase flow region of the drill string, the pressure gradient is calculated based on the momentum conservation equation of the single-phase fluid, which consists of a gravity term and a friction term; for the multiphase flow region of the annulus, the pressure gradient is calculated based on the mass conservation equation and the momentum conservation equation of the gas-liquid two-phase flow.

[0011] Optionally, the temperature field model and the pressure field model are solved using an iterative coupled solution method, including: The temperature field is solved based on the initial pressure field; the fluid properties are corrected using the updated temperature field and the pressure field is solved again until the changes in the temperature distribution and the pressure distribution are less than a preset convergence threshold.

[0012] Optionally, the temperature and pressure distribution along the depth direction of the wellbore can be obtained in at least one of the following ways: Generate temperature-depth and pressure-depth curves along the well depth; output a data file containing temperature and pressure values ​​at different depth points; trigger a drilling risk warning signal when the predicted pressure value exceeds the safety threshold.

[0013] Secondly, to efficiently execute the method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions provided by this invention, this invention also provides a system for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions, comprising: an input device, an output device, a processor, and a memory, wherein the input device, output device, processor, and memory are interconnected, and the memory stores program instructions used for the method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions. The system for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions provided by this invention has a compact structure and stable performance, and can stably execute the method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions provided by this invention, further improving the overall applicability and practical application capability of this invention.

[0014] Because the temperature field model, by constructing and coupling the energy conservation control equations for the drill string fluid, annular fluid, and casing wall respectively, can precisely simulate the heat exchange process between different components within the wellbore, including axial convection, axial heat conduction, and heat exchange with the external environment, it can more accurately reflect the thermodynamic behavior during actual drilling, thereby improving the accuracy of temperature field prediction. Simultaneously, because the pressure field model clearly distinguishes between the single-phase flow region of the drill string and the multiphase flow region of the annulus, and establishes models based on the conservation equations for single-phase and two-phase fluids respectively, especially by integrating the gas intrusion model and using the ideal gas equation of state to update gas properties in real time, it can accurately simulate the expansion behavior of gas after intrusion with varying well depth and its impact on pressure distribution. This allows the model to more realistically characterize the pressure change characteristics of the wellbore under gas intrusion conditions, significantly improving the accuracy of pressure field prediction. By employing an iterative coupled solution method, the temperature field and pressure field models can mutually correct each other, further ensuring the consistency of the physical field simulation. The system ultimately outputs high-precision temperature and pressure distribution data, providing reliable data support for safety assessment and risk warning in complex drilling scenarios such as deep-sea ultra-shallow gas layers. Attached Figure Description

[0015] Figure 1 A flowchart illustrating a method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions, provided in an embodiment of the present invention; Figure 2 This is a framework diagram of a deep-sea ultra-shallow gas layer wellbore temperature and pressure field prediction system under gas intrusion conditions, provided as an embodiment of the present invention. Detailed Implementation

[0016] Specific embodiments of the present invention will now be described in detail. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other instances, well-known circuits, software, or methods have not been specifically described to avoid obscuring the invention.

[0017] Throughout this specification, references to "an embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "in an embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale.

[0018] Please see Figure 1 This invention provides a method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas invasion conditions. By coupling the energy conservation of the drill string, annulus and pipe wall, and accurately distinguishing between single-phase and multi-phase flow pressure calculation models, the method can finely characterize the thermodynamic and hydrodynamic processes in the wellbore. Combined with the real-time property updates of the gas invasion model, the method significantly improves the accuracy of wellbore temperature and pressure field prediction under complex working conditions, especially when gas invasion is present.

[0019] Specifically, it includes the following steps: S1. Obtain drilling parameters, including wellbore geometry parameters, drilling fluid parameters, operating condition parameters, and gas intrusion parameters.

[0020] In this embodiment, drilling parameters specifically include wellbore geometric parameters, drilling fluid parameters, operating condition parameters, and gas intrusion parameters. Wellbore geometric parameters include at least well depth, seawater depth, and tubing diameter; drilling fluid parameters include at least drilling fluid density and specific heat capacity; operating condition parameters include at least drilling fluid flow rate, circulation time, and inlet temperature; and gas intrusion parameters include at least gas intrusion location and gas intrusion volumetric flow rate.

[0021] These parameters are used as input data for subsequent modeling calculations by calling preset input interfaces or reading from stored data files.

[0022] S2. Based on the drilling parameters, establish a temperature field model and a pressure field model for the wellbore.

[0023] First, the temperature field model is established by determining the temperature gradient of the external environment along the depth direction based on the seawater depth in the wellbore geometry and operating parameters. The external environment includes the seawater section and the formation section. Then, based on the temperature gradient and the obtained drilling parameters, the energy conservation control equations for the drill string fluid, the annular fluid, and the pipe wall are constructed respectively.

[0024] Specifically, determining the ambient temperature gradient includes: for the depth range of the seawater section, calculating the temperature using a preset seawater temperature distribution function, which has the following form: in, Depth of seawater section The temperature at that location These are adjustment factors used to fit the actual seawater temperature profile. This is the temperature correction factor.

[0025] For the depth range of the strata, the temperature is calculated using the linear geothermal gradient formula, which is: in, For the depth of the stratigraphic section The temperature at that location For seabed temperature, Seawater depth This represents the geothermal gradient.

[0026] When constructing the energy conservation control equations, the drill string fluid energy control terms include heat storage terms, axial convection terms, and pipe wall heat transfer terms; the annular fluid energy control terms include heat storage terms, backflow convection terms, pipe wall heat transfer terms, and external environment heat transfer terms; the pipe wall energy control terms include heat storage terms, axial heat conduction terms, and convective heat transfer terms with the drill string fluid and annular fluid, respectively.

[0027] In the embodiment, the drill string fluid energy control term satisfies: in, Indicates the drill string heat source term. Indicates volumetric flow rate, Indicates the density of drilling fluid. This indicates the specific heat capacity of the drilling fluid. This indicates the temperature of the fluid inside the drill string. Indicates the inner diameter of the drill string. Indicates the internal convection heat transfer coefficient. Indicates the pipe wall temperature. Indicates time.

[0028] The annular fluid energy control term satisfies: in, Indicates the temperature of the annular fluid. This represents the seawater heat transfer coefficient as a function of time. Indicates seawater temperature, Indicates the outer diameter of the drill string. Indicates the convective heat transfer coefficient on the annulus side. Indicates the annular heat source term. This indicates the inner diameter of the riser pipe.

[0029] Pipe wall energy control terms, satisfying: in, Indicates the thermal conductivity of the pipe wall. Indicates the density of the pipe wall. This indicates the specific heat capacity of the pipe wall.

[0030] The specific mathematical expressions for these terms can be constructed by those skilled in the art based on the fundamental laws of heat transfer (such as Fourier's law of heat conduction and Newton's law of cooling). Together, they constitute a closed set of equations describing the downward flow of fluid in the drill string, the upward flow of fluid in the annulus, and the heat exchange between the wellbore and the casing.

[0031] Secondly, establishing the pressure field model includes: for the single-phase flow region of the drill string, calculating the pressure gradient based on the momentum conservation equation of the single-phase fluid. This pressure gradient consists of a gravity term and a friction term. The friction term is calculated based on the Darcy-Weisbach formula, and the pressure increment... The calculation formula is: in, For fluid density, It is the acceleration due to gravity. For depth increment, The Darcy friction coefficient (can be solved iteratively using equations such as the Colebrook-White equation). For apparent flow rate, It is the hydraulic diameter.

[0032] For the annular multiphase flow region, the pressure gradient is calculated based on the mass conservation equation and momentum conservation equation for gas-liquid two-phase flow.

[0033] In one embodiment, the liquid phase continuity equation is: in, Indicates the liquid volume fraction. Represents the cross-sectional area of ​​the annulus. Indicates the liquid phase velocity. This indicates the annular flow area.

[0034] The gas-phase continuity equation is: in, Indicates gas density, Indicates the gas phase volume fraction. Indicates gas phase velocity, Indicates the gas source term. This represents the gas loss term.

[0035] The momentum conservation equation is: In another embodiment, establishing the pressure field model also includes an integrated gas intrusion model, specifically including: calculating the bottom hole gas mass flow rate based on the gas intrusion volume flow rate in the gas intrusion parameters and the pressure and temperature at the bottom of the well.

[0036] The gas density is calculated in real time based on the pressure and temperature at the current well depth, according to the ideal gas law. Then, the gas volumetric flow rate at the current well depth is updated based on the gas mass flow rate and the real-time calculated gas density.

[0037] In this way, the model can simulate the dynamic behavior of gas expanding as pressure decreases during ascent and feed its effects back into the continuity and momentum equations of the annular multiphase flow.

[0038] S3. Solve the temperature field model and the pressure field model to obtain the temperature distribution and pressure distribution along the depth direction of the wellbore.

[0039] First, based on an initial estimated pressure field (e.g., hydrostatic column pressure distribution) as input, solve the temperature field model.

[0040] When solving the temperature field model, the energy conservation control equations for the drill string fluid, annular fluid, and pipe wall are discretized using a fully implicit differential discretization (where the axial convection term is discretized using an upwind discretization to improve numerical stability). The discretized equations are then constructed into a sparse linear equation system, which is solved using a processor by methods such as the conjugate gradient method or a direct solution method to obtain the temperature distribution.

[0041] In one embodiment, the fully implicit differential discretization of the energy conservation equations for the drill string, annulus, and pipe wall is constructed, including: Drill string internal temperature θc (downward): Drill string internal temperature θa (upward): in, Indicates the cross-sectional area of ​​the drill string. Indicates volumetric flow rate, This represents the heat transfer coefficient between the drill string and the pipe wall. Indicates the current time step. Indicates the effective mass heat capacity flow rate. This represents the heat transfer coefficient between the annulus and the tube wall. Indicates the external heat transfer coefficient. Indicates the spatial node number.

[0042] Then, the updated temperature distribution is used to correct the physical properties of the fluids (especially gases and drilling fluids), such as density, viscosity, specific heat capacity, etc., and the pressure field model is solved again.

[0043] Pressure field solutions typically begin with the wellhead or bottom as boundary conditions, integrating along the depth direction to calculate the pressure gradient. For the drill string region, the single-phase flow pressure gradient formula is directly integrated; for the annulus region, the governing equations for gas-liquid two-phase flow must be solved simultaneously. This iterative process of mutual correction between the temperature and pressure fields continues until the changes in temperature and pressure distributions obtained from two consecutive iterations are both less than a preset convergence threshold (e.g., the maximum relative error is less than 0.1%). At this point, the model is considered to have reached convergence, yielding a self-consistent and stable temperature and pressure field prediction result.

[0044] In this embodiment, the output temperature and pressure distribution includes, but is not limited to, one or more of the following: generating temperature-depth and pressure-depth curves along the well depth through a graphical user interface or plotting library (such as Matplotlib) to visually display the prediction results; writing an array containing temperature and pressure values ​​at different depth points into a text file or database for subsequent analysis; when the predicted pressure value (such as wellhead pressure or annular pressure at a certain depth) exceeds a preset safety threshold based on the well structure and drilling fluid performance, the processor triggers a drilling risk warning signal, which can be manifested as a highlighted warning on the screen, an audible prompt, or sent to a remote monitoring center via a communication interface.

[0045] This invention is particularly applicable to the prediction of multiphase flow obstacle risks in wellbore drilling processes in deep-sea ultra-shallow gas formations. Through high-precision temperature and pressure field prediction, the risk of hydrate formation, wellbore stability, and pressure requirements of well control equipment can be assessed, thereby optimizing drilling design and real-time operational decisions.

[0046] It should be noted that the specific implementation methods described above, such as image processing, numerical simulation, and the construction and training of machine learning models, can all be accomplished by the processor by calling the corresponding computer program instructions stored in memory. Those skilled in the art can implement the above functions using algorithms and tools known in the prior art, according to actual needs.

[0047] Please see Figure 2In this embodiment, to efficiently execute the method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions provided by this invention, the present invention also provides a system for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions, comprising: an input device 1, an output device 2, a processor 3, and a memory 4, wherein the input device 1, output device 2, processor 3, and memory 4 are interconnected, and the memory 4 stores program instructions for executing the steps of the method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions. The system for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions provided by this invention has a compact structure and stable performance, and can stably execute the method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions provided by this invention, further enhancing the overall applicability and practical application capability of this invention.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A method for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions, characterized in that, Includes the following steps: Obtain drilling parameters, including wellbore geometry parameters, drilling fluid parameters, operating condition parameters, and gas intrusion parameters; Based on the drilling parameters, a temperature field model and a pressure field model of the wellbore are established. The temperature field model couples the energy conservation of the drill string fluid, the annular fluid, and the pipe wall. The pressure field model is established based on the conservation of mass and momentum, and distinguishes between the single-phase flow region of the drill string and the multiphase flow region of the annulus. Solve the temperature field model and the pressure field model to obtain the temperature and pressure distribution along the depth direction of the wellbore; The wellbore geometric parameters include at least well depth, seawater depth, and tubing diameter; the drilling fluid parameters include at least drilling fluid density and drilling fluid specific heat capacity; the operating condition parameters include at least drilling fluid discharge rate, circulation time, and inlet temperature; and the gas intrusion parameters include at least gas intrusion location and gas intrusion volumetric flow rate. Establishing the temperature field model includes: Based on the wellbore geometry parameters and the seawater depth in the operating parameters, the temperature gradient of the external environment along the depth direction of the wellbore is determined, and the external environment includes the seawater section and the formation section. Based on the temperature gradient and the drilling parameters, energy conservation control equations for drill string fluid, annular fluid and pipe wall are constructed respectively. Establishing the pressure field model includes: For the single-phase flow region of the drill string, the pressure gradient is calculated based on the momentum conservation equation of the single-phase fluid, and the pressure gradient consists of gravity terms and friction terms. For the annular multiphase flow region, the pressure gradient is calculated based on the mass conservation equation and momentum conservation equation for gas-liquid two-phase flow; The temperature field model and the pressure field model are solved using an iterative coupled solution method, including: Solving the temperature field based on the initial pressure field; The fluid properties are corrected using the updated temperature field and the pressure field is re-solved until the changes in the temperature distribution and the pressure distribution are less than a preset convergence threshold. Obtaining the temperature and pressure distribution along the depth direction of the wellbore can be achieved through at least one of the following methods: Generate temperature-depth and pressure-depth plots along the well depth; Output a data file containing temperature and pressure values ​​at different depth points; When the predicted pressure value exceeds the safety threshold, a drilling risk warning signal is triggered.

2. The method for predicting the temperature and pressure field of deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions according to claim 1, characterized in that, Determining the temperature gradient of the external environment along the depth direction of the wellbore includes: For the depth range of the seawater section, the temperature is calculated using a preset seawater temperature distribution function; For the depth range of the strata, the temperature is calculated using the linear geothermal gradient formula.

3. The method for predicting the temperature and pressure field of deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions according to claim 1, characterized in that, The energy conservation governing equations are constructed as follows: Drill string fluid energy control items include heat storage items, axial convection items, and pipe wall heat exchange items; The annular fluid energy control items include heat storage items, backflow convection items, pipe wall heat exchange items, and external environment heat exchange items; The tube wall energy control items include heat storage items, axial heat conduction items, and convective heat transfer items with drill string fluid and annular fluid, respectively.

4. The method for predicting the temperature and pressure field of deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions according to claim 1, characterized in that, Solving the temperature field model includes: The energy conservation control equations for the drill string fluid, annular fluid, and pipe wall are performed using fully implicit differential discretization, with the axial convection term discretized using an upwind discretization method. The discretized equations are constructed into a sparse linear system of equations and then solved.

5. A system for predicting the temperature and pressure field of a deep-sea ultra-shallow gas layer wellbore under gas intrusion conditions, characterized in that, The deep-sea ultra-shallow gas layer wellbore temperature and pressure field prediction system under gas invasion conditions includes: an input device, an output device, a processor, and a memory. The input device, output device, processor, and memory are interconnected. The memory stores program instructions, which are used to execute the deep-sea ultra-shallow gas layer wellbore temperature and pressure field prediction method under gas invasion conditions as described in any one of claims 1-4.

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