A method and system for dynamically predicting sand deposition in an oil and gas gathering pipeline

Abstract

The application discloses a kind of oil and gas gathering pipeline sand deposition dynamic prediction method and system, it is related to oil and gas gathering system simulation prediction technical field, comprising: establishing pipeline structure model, and the discretization of pipeline structure model is carried out to divide calculation unit;Hydraulic and thermodynamic parameters of whole pipeline are calculated by using transient flow model coupling thermodynamics model to carry out space iteration;Sand deposition critical flow velocity model is used, the critical flow velocity of sand deposition along the line of pipeline is calculated, and the migration state of sand particle is judged;According to sand particle migration state, the height of deposited sand bed along the line of pipeline is calculated, and pipeline structure parameters and sand particle attribute parameters are updated;The above steps are repeated to output hydraulic and thermodynamic parameters, sand deposition critical flow velocity and deposited sand bed height under each time, space as prediction result;The application can be suitable for different types of conveying medium gathering pipeline, can reflect the dynamic influence of conveying flow, sand-carrying attribute and medium physical property on sand deposition characteristics in real time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas gathering and transportation system simulation and prediction, and particularly relates to a method and system for dynamically predicting sand deposition in an oil and gas gathering and transportation pipeline. BACKGROUND

[0002] In the process of oil and gas field development, the reservoir structure is inevitably damaged, which in turn induces sand production, resulting in the common presence of sand entrainment in gathering and transportation pipelines. When the fluid velocity in the pipeline is lower than the critical sand-carrying velocity, sand particles will deposit to form a sand bed, causing a reduction in the flow area of the pipeline, an increase in the transportation friction, and an intensification of internal corrosion, etc., which seriously threatens the safety and operational efficiency of the oil and gas pipeline. In order to ensure the safe and stable operation of the gathering and transportation pipeline, it is necessary to accurately predict the distribution of the deposited sand bed in the pipeline, the accumulation height of the sand bed, and other related deposition characteristics.

[0003] At present, domestic and foreign scholars have carried out a large number of experimental studies and established a series of sand deposition critical flow velocity models. However, the existing sand deposition prediction methods are mostly based on the steady-state assumption, can only determine whether the sand particles are deposited, and cannot accurately describe the deposition height and dynamic change characteristics of the sand bed, and at the same time, the coupling relationship between the fluid properties, transient flow parameters, sand deposition critical flow velocity, and sand bed characteristics is not systematically considered. In the actual operation process of the gathering and transportation pipeline, the flow parameters frequently fluctuate, and the sand particles exhibit complex dynamic migration and deposition behavior, which makes it difficult for the existing sand deposition prediction methods to accurately characterize the transient flow characteristics and dynamic migration law of the sand particles in the pipeline, thereby affecting the prediction accuracy of the sand deposition risk. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a method and system for dynamically predicting sand deposition in an oil and gas gathering and transportation pipeline, which can be applied to gathering and transportation pipelines of different types of transportation medium, can reflect the dynamic influence of transportation flow, sand-carrying properties, and medium properties on sand deposition characteristics in real time, and can realize coupled calculation through the interaction of transient flow and sand deposition, thereby providing key technical support for the sand-carrying control of pipeline fluid and the prediction of sand deposition risk.

[0005] The technical solution of the present application is as follows:

[0006] In the first aspect of the present application, a method for dynamically predicting sand deposition in an oil and gas gathering and transportation pipeline is provided, comprising the following steps:

[0007] Step one, obtaining pipeline structure parameters, establishing a pipeline structure model according to the pipeline structure parameters, and discretizing the pipeline structure model to divide calculation units;

[0008] Step two, obtaining the basic physical parameters of the fluid medium in the pipeline and the sand attribute parameters, defining the flow boundary conditions of the pipeline structure model, and combining the pipeline structure parameters, using the transient flow model coupled with the thermodynamic model to perform spatial iterative calculation of the hydraulic and thermal parameters of the whole pipeline;

[0009] Step three, based on the pipeline structure parameters, the basic physical parameters of the fluid medium, the sand attribute parameters and the hydraulic and thermal parameters, using the sand deposition critical flow velocity model to calculate the sand deposition critical flow velocity along the pipeline, comparing the sand deposition critical flow velocity along the pipeline with the fluid medium flow velocity in the hydraulic and thermal parameters to determine the sand migration state;

[0010] Step four, calculating the deposited sand bed height along the pipeline according to the sand migration state and updating the pipeline structure parameters and the sand attribute parameters;

[0011] Step five, repeating steps two to four to perform time step iterative calculation, and outputting the hydraulic and thermal parameters, the sand deposition critical flow velocity and the sand bed height at each time and space as the prediction results after the iteration is completed.

[0012] In some embodiments of the present application, in step three, when determining the sand migration state, it is considered that the sand is mainly carried by the liquid phase, and the gas phase indirectly acts on the sand migration state by affecting the liquid phase flow parameters, and the specific determination method is as follows:

[0013] When the liquid phase real velocity is equal to the sand deposition critical flow velocity, it is in a balanced state;

[0014] When the liquid phase real velocity is less than the sand deposition critical flow velocity, it is in a deposition state;

[0015] When the liquid phase real velocity is greater than the sand deposition critical flow velocity, if no deposited sand bed is formed, it is in a non-deposition state, and if there is a sand bed and the fluid carries sand again, it is in a restart state.

[0016] In some embodiments of the present application, in step four, when calculating the deposited sand bed height along the pipeline according to the sand migration state, the deposited sand bed height in the pipeline is iteratively calculated based on the steady flow model according to the sand migration state:

[0017] If the sand is in a sand deposition balanced state, the deposited sand bed height remains unchanged;

[0018] If the sand is in a sand deposition state, the balanced deposited sand bed height is iteratively calculated between the current deposited sand bed height and the completely deposited height of the suspended sand;

[0019] If the sand is in a continuous migration and non-deposition state, the deposited sand bed height is zero;

[0020] If the sand grains are in a sand-carrying restart state, the equilibrium sedimentary sand bed height is iteratively calculated between the height of the sand-free bed and the current sedimentary sand bed.

[0021] In some embodiments of the present invention, when iteratively calculating the height of the sand bed in the pipeline based on the steady-state flow model, a relationship between the height of the sand bed and the volume of deposited sand particles is established through geometric relationships for iterative calculation. The established relationship is as follows:

[0022]

[0023] In the formula, A bi For the first i The cross-sectional area of ​​the sedimentary sand grains in the section, V bi For the first i The volume of sedimentary sand grains in the section, φ For the porosity of the sand bed, Δ L i For the first i The length of the segment D i For the first i The inner diameter of the section of pipe, h bi For the first i The height of the sedimentary sand bed in the section.

[0024] In some embodiments of the present invention, step four, updating the pipe structure parameters, includes calculating the equivalent diameter in the pipe structure parameters based on the sand bed height, and further calculating the thermal conductivity in the pipe structure parameters based on the equivalent diameter.

[0025] In some embodiments of the present invention, the equivalent diameter is calculated using the following formula:

[0026]

[0027] In the formula, D Ei For the first i Equivalent pipe diameter of the section A i For the first i The cross-sectional area of ​​the segment V bi Let be the volume of the sedimentary sand grains in the i-th segment. φ For the porosity of the sand bed, Δ L i For the first i The length of the segment.

[0028] In some embodiments of the present invention, the formula for calculating the thermal conductivity is as follows:

[0029] ;

[0030] ;

[0031] ;

[0032] ;

[0033] In the formula, U Ei For the first i The thermal conductivity of the section R sandi , R walli , R insi The first i The thermal resistance of the sand particles, the thermal resistance of the pipe wall, and the thermal resistance of the insulation layer in the section. k sand , k walli , k insi These are the thermal conductivity of sand particles, respectively. i The thermal conductivity of the pipe wall and the thermal conductivity of the insulation layer of the section, δ walli δ walli The first i The thickness of the pipe wall and the thickness of the insulation layer in the section.

[0034] In some embodiments of the present invention, updating the sand grain property parameters includes updating the sand grain mass concentration in the sand grain property parameters, and the calculation formula for updating is as follows:

[0035] ;

[0036] ;

[0037] ;

[0038] ;

[0039] In the formula, C Mi For the first i The mass concentration of suspended sand particles after each step of the segment's propulsion. M i For the first i The original suspended sand particles in the section, M in , M out These represent the input and output sand particle masses during time-step propulsion, Δ L i For the first i The length of the segmentA i For the first i The cross-sectional area of ​​the segment, Δ t For time step, C M(i-1) , Q (i-1) The first i The suspended sand particle mass concentration and fluid volumetric flow rate of the front-end unit of the section. C Mi0 , Q i The first i The initial suspended sand particle mass concentration and fluid volumetric flow rate of the segment, D i For the first i The inner diameter of the pipe section.

[0040] In some embodiments of the present invention, the sand deposition distribution of the entire pipeline is obtained based on the height of the sand bed along the pipeline to predict the sand deposition risk. When the height of the sand bed is greater than zero, it indicates that there is a sand deposition risk in the pipeline. When the height of the sand bed is equal to zero, it indicates that there is no sand deposition risk in the pipeline.

[0041] In a second aspect of the invention, a dynamic prediction system for sand deposition in oil and gas gathering and transportation pipelines is provided, comprising:

[0042] The pipeline structure model building module is configured to: obtain pipeline structure parameters, build a pipeline structure model based on the pipeline structure parameters, and discretize the pipeline structure model to divide it into computational units;

[0043] The transient flow calculation module is configured to: obtain the basic physical property parameters of the fluid medium and the sand particle property parameters in the pipeline, define the flow boundary conditions of the pipeline structure model, and combine the pipeline structure parameters to perform spatial iterative calculation of the hydraulic and thermal parameters of the entire pipeline using a transient flow model coupled with a thermodynamic model.

[0044] The sand particle transport state determination module is configured to: calculate the critical flow velocity of sand deposition along the pipeline using the critical flow velocity model of sand deposition, based on the pipeline structure parameters, the basic physical property parameters of the fluid medium, the sand particle property parameters, and the hydraulic and thermal parameters; compare the critical flow velocity of sand deposition along the pipeline with the fluid medium flow velocity in the hydraulic and thermal parameters to determine the sand particle transport state.

[0045] The parameter update module is configured to: calculate the height of the sedimentary sand bed along the pipeline based on the sand grain migration state, and update the pipeline structural parameters and sand grain property parameters;

[0046] The prediction result output module is configured to: repeat the time step iteration calculation of steps two to four, and output the hydraulic and thermal parameters, the sand deposition critical flow velocity and the sand bed height at each time and space as the prediction result after the iteration is completed.

[0047] The one or more technical solutions of the present application have the following beneficial effects:

[0048] (1) The prediction method provided by the present application can depict the interaction between transient flow and sand deposition through the coupling calculation of transient flow and sand deposition in the gathering pipeline, realize real-time prediction of the sand particle migration state, sand bed distribution and accumulation height in the pipeline, and quantitatively reflect the dynamic evolution law of the sand deposition characteristics with the changes of flow, sand properties and medium physical properties and other parameters, thereby providing reliable technical support for the fluid sand-carrying control and sand deposition risk warning of the pipeline, and improving the safety and stability of the gathering pipeline operation.

[0049] (2) The prediction method provided by the present application can flexibly select the physical property calculation model, flow calculation model and sand deposition critical flow velocity model according to the differences in working conditions such as the conveying medium and sand particle properties, has strong engineering applicability, can realize accurate sand deposition prediction under complex flow conditions, and meets the safety monitoring and early warning needs under different working conditions.

[0050] (3) The prediction method provided by the present application can help the operator to identify the potential sand deposition risk in the pipeline in advance, take effective preventive measures (such as adjusting the flow, pigging operation, etc.) in time, reduce the shutdown and maintenance frequency caused by sand deposition, and reduce the occurrence rate of pipeline blockage and equipment damage, thereby reducing the operating cost, improving the operation efficiency and economy of the gathering pipeline. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 It is a flow chart of the oil and gas gathering pipeline sand deposition dynamic prediction method of the present application;

[0052] Figure 2 It is a calculation process diagram of the oil and gas gathering pipeline sand deposition dynamic prediction method of the present application;

[0053] Figure 3 It is a sand deposition prediction effect schematic diagram of the present application;

[0054] Figure 4 It is a sand bed balance state calculation flow chart of the present application;

[0055] Figure 5 It is a prediction result schematic diagram of one specific embodiment of the present application; wherein (a) is the established pipeline route, (b) is the predicted pressure and temperature, (c) is the predicted critical flow velocity and liquid phase flow velocity, and (d) is the predicted sand deposition state;

[0056] Figure 6 A sand dynamic deposition prediction result schematic diagram of one specific embodiment of the present application;

[0057] Figure 7 A sand carrying restart prediction result schematic diagram of one specific embodiment of the present application;

[0058] Figure 8 A structure diagram of the sand deposition dynamic prediction system of the oil and gas gathering pipeline of the present application. DETAILED DESCRIPTION

[0059] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0060] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of a feature, step, operation, device, component and / or combinations thereof.

[0061] Example 1

[0062] In a typical embodiment of the present application, a sand deposition dynamic prediction method for an oil and gas gathering pipeline is proposed, as shown in Figure 1 The method comprises the following steps:

[0063] Step 1, obtain the pipeline structure parameters, establish a pipeline structure model according to the pipeline structure parameters, and discretize the pipeline structure model to divide the calculation units;

[0064] Step 2, obtain the basic physical property parameters of the fluid medium in the pipeline and the sand particle attribute parameters, define the flow boundary conditions of the pipeline structure model, and combine the pipeline structure parameters to perform spatial iterative calculation of the hydraulic and thermal parameters of the whole pipeline by using the transient flow model coupled with the thermodynamic model;

[0065] Step 3, based on the pipeline structure parameters, the basic physical property parameters of the fluid medium, the sand particle attribute parameters and the hydraulic and thermal parameters, a sand deposition critical flow velocity model is used to calculate the sand deposition critical flow velocity along the pipeline, and the sand deposition critical flow velocity along the pipeline is compared with the fluid medium flow velocity in the hydraulic and thermal parameters to determine the sand particle migration state;

[0066] Step 4, calculate the deposition sand bed height along the pipeline according to the sand particle migration state, and update the pipeline structure parameters and the sand particle attribute parameters;

[0067] Step five, repeat steps two to four when the step iteration calculation is performed, and output the hydraulic and thermal parameters, sand deposition critical flow velocity and sand bed height at each time and space as the prediction result after the iteration is completed.

[0068] The specific steps of the oil and gas gathering pipeline sand deposition dynamic prediction method are described in detail as follows, as shown in Figure 2

[0069] Step one, obtain the pipeline structure parameters, establish a pipeline structure model according to the pipeline structure parameters, and discretize the pipeline structure model to divide the calculation unit.

[0070] Specifically, the obtained pipeline structure parameters include: pipeline route X coordinate, pipeline route Y coordinate, pipeline inclination angle, pipeline diameter, pipeline roughness, pipeline wall thickness, pipeline thermal conductivity, insulation layer thickness, insulation layer thermal conductivity, pipeline external environment temperature, etc.

[0071] Step two, obtain the basic physical property parameters of the fluid medium in the pipeline and the sand particle attribute parameters, define the flow boundary conditions of the pipeline structure model, and combine the pipeline structure parameters to perform spatial iteration calculation of the hydraulic and thermal parameters of the whole pipeline by coupling the transient flow model and the thermodynamic model.

[0072] The obtained basic physical property parameters of the fluid medium in the pipeline include: density, viscosity, interfacial tension, enthalpy, thermal conductivity, specific heat capacity at constant pressure, specific heat capacity at constant volume, etc. of the fluid medium (gas-liquid two-phase) at different temperatures and pressures. When obtaining the basic physical property parameters of the fluid medium, the applicable physical property calculation model can be selected according to the specific working condition and calculation requirement to calculate the density, viscosity, etc. of the fluid medium at different pressures and temperatures, or directly read the physical property file generated by the commercial oil and gas simulation software to establish a fluid property database, ensuring the applicability and accuracy requirement of different types of fluid property calculation.

[0073] The obtained sand particle attribute parameters include: sand particle size, sand density, sand bed porosity, inlet sand particle mass concentration, inlet sand particle mass concentration change time, sand particle thermal conductivity. The defined flow boundary condition parameters include: inlet temperature, inlet temperature change time, inlet mass flow rate, inlet mass flow rate change time, outlet pressure, outlet pressure change time.

[0074] ​Further, the hydraulic and thermodynamic parameters calculated by coupling the transient flow model with the thermodynamic model include: gas phase velocity, liquid phase flow rate, liquid holdup, gas-liquid flow pattern, pressure, temperature, pressure gradient, temperature gradient, etc. In the calculation of the hydraulic and thermodynamic parameters, according to the specific working conditions and the calculation requirements, the applicable transient flow model is selected, the hydraulic and thermodynamic parameters of the pipeline are calculated by coupling the thermodynamic model, and the accurate calculation of the transient flow parameters under different working conditions is realized. Among them, the transient flow model can select the hydraulic model of single phase, oil-water two-phase or gas-liquid two-phase according to the difference of the pipeline conveying medium (such as pure gas, oil-water, oil-gas, etc.).

[0075] The transient flow calculation starts from the boundary element, transmits the mass flow rate between each pipe section to ensure the system mass conservation, and recursively calculates the hydraulic and thermodynamic parameters of the next element based on the hydraulic and thermodynamic parameters of the previous element, so as to realize the collaborative calculation of momentum conservation and energy conservation. Through repeated transient flow calculation, the iterative solution of the hydraulic and thermodynamic parameters of the whole pipeline is realized, and the transient flow process in the pipeline is accurately described. Taking the calculation of pressure and temperature as an example, the specific calculation formula is as follows:

[0076] The formula for calculating the pressure of the next element is:

[0077] ;

[0078] The formula for calculating the temperature of the next element is:

[0079] ;

[0080] In the formula, i represents the pipeline calculation element, P i 、 T i are the pressure and temperature of the first i section, respectively, P i+1 、 T i+1 are the pressure and temperature of the first i +1 section, respectively, P i , Δ T i are the pressure drop and temperature drop of the first i section, respectively, L i is the length of the first i section.

[0081] Step three, based on the pipe structure parameters, the basic physical parameters of the fluid medium, the sand attribute parameters and the hydraulic and thermal parameters, the sand deposition critical flow velocity model is used to calculate the sand deposition critical flow velocity along the pipeline, and the sand deposition critical flow velocity along the pipeline is compared with the fluid medium flow velocity in the hydraulic and thermal parameters to determine the sand migration state.

[0082] Specifically, according to the engineering background and the difference of the conveying medium, the sand deposition critical flow velocity model is optimized, or multiple critical flow velocity models are combined to realize accurate calculation of the sand deposition critical flow velocity along the pipeline under different working conditions, and the sand deposition critical flow velocity along the pipeline is compared with the fluid medium flow velocity in the hydraulic and thermal parameters

[0083] The sand migration state is dynamically determined. Specifically, the sand deposition critical flow velocity model can select the critical flow velocity model established for liquid phase, gas phase or gas-liquid two-phase according to different application engineering backgrounds, and can be optimized according to the application range, simplified conditions and other characteristics of the model, and can be combined with multiple models to adapt to the sand deposition prediction requirements under different working conditions, thereby improving the sand deposition prediction accuracy and engineering applicability.

[0084] Further, when determining the sand migration state, it is considered that the sand particles are mainly carried by the liquid phase, and the gas phase indirectly acts on the sand migration state by affecting the liquid phase flow parameters, such as Figure 3 As shown in the specific determination method as follows:

[0085] When the liquid phase flow velocity is equal to the sand deposition critical flow velocity, it is in a balanced state; at this time, the sand deposition reaches a dynamic balance state, and the suspended sand particles continuously migrate with the fluid, and the deposited sand particles remain in a piled-up state.

[0086] When the liquid phase flow velocity is less than the sand deposition critical flow velocity, it is in a deposition state; at this time, the suspended sand particles are deposited, resulting in an increase in the local pipe section sand bed height.

[0087] When the liquid phase flow velocity is greater than the sand deposition critical flow velocity, if no deposition sand bed is formed, it is in a non-deposition state, at this time the sand particles continuously migrate with the fluid; if there is a sand bed and the fluid carries sand again, it is in a restart state, at this time the fluid carries sand again, and the deposited sand particles are resuspended.

[0088] Step four, calculating the sand bed height along the pipeline according to the sand migration state, and updating the pipe structure parameters and the sand attribute parameters.

[0089] Specifically, when calculating the sand bed height along the pipeline according to the sand migration state, the sand bed height in the pipeline is iteratively calculated based on the steady flow model according to the sand migration state:

[0090] If the sand particles are in a sand deposition balance state, the sand bed height remains unchanged;

[0091] If the sand grains are in a sand deposition state, then the equilibrium sedimentary sand bed height is iteratively calculated between the current sedimentary sand bed height and the height of the suspended sand grains after complete deposition.

[0092] If the sand grains are in a state of continuous movement and no deposition, then the height of the sedimentary sand bed is zero;

[0093] If the sand grains are in a sand-carrying restart state, the equilibrium sedimentary sand bed height is iteratively calculated between the height of the sand-free bed and the current sedimentary sand bed.

[0094] In the above iterative calculation of sand bed height, the equality of the liquid phase velocity and the critical velocity for sand deposition in the hydraulic and thermal parameters is used as the criterion for determining sand bed equilibrium. If sand deposition occurs, the sand bed rises, leading to a decrease in the pipe flow area, an increase in the liquid phase velocity, and a decrease in the suspended sand concentration, thus lowering the critical velocity for sand deposition. If the liquid phase velocity can be increased to the critical velocity for sand deposition, the sand bed height reaches equilibrium; otherwise, the suspended sand particles are completely deposited. If sand-carrying restart occurs, the sand bed lowers, leading to an increase in the pipe flow area, a decrease in the liquid phase velocity, and an increase in the suspended sand concentration, thus raising the critical velocity for sand deposition. If the liquid phase velocity can be reduced to the critical velocity for sand deposition, the sand bed height reaches equilibrium; otherwise, the deposited sand particles are completely suspended.

[0095] Furthermore, when iteratively calculating the sand bed height within the pipeline based on the steady-state flow model, a relationship between the sand bed height and the volume of deposited sand grains is established through geometric relationships for iterative calculation. The established relationship is as follows:

[0096]

[0097] In the formula, A bi For the first i The cross-sectional area of ​​the sedimentary sand grains in the section, V bi For the first i The volume of sedimentary sand grains in the section, φ For the porosity of the sand bed, Δ L i For the first i The length of the segment D i For the first i The inner diameter of the section of pipe, h bi For the first i The height of the sedimentary sand bed in the section.

[0098] Specifically, the iterative calculation process for the height of the sand bed inside the pipe is as follows: Figure 4 As shown, when sand grains are in a sand deposition state, at the current sand bed height h b0 and total sediment height h b2Iterative solution of equilibrium sand bed height h b1 , assuming all sand is deposited, h b1 = h b2 , calculate and pass the equivalent pipe diameter at this time D E , then use the steady state solution module to call the steady state flow model to update the liquid phase flow rate U L , calculate the sand concentration taking into account the dynamic behavior of the sand, calculate the critical sand deposition velocity after deposition U C , determine if the sand is fully deposited ( U L ≤ U C ), if so, output the sand bed height at this time, calculate the equivalent pipe diameter and thermal conductivity at the equilibrium state of sand deposition, if not, assume a sand bed height within the iteration range h b1 , then use the steady state solution module to call the steady state flow model to update the liquid phase flow rate U L , calculate the sand concentration taking into account the dynamic behavior of the sand, calculate the critical sand deposition velocity after deposition U C , determine if the sand bed is at equilibrium ( U L - U C | / U L <0.1%>, if so, output the sand bed height at this time, calculate the equivalent pipe diameter and thermal conductivity at the equilibrium state of sand deposition, if not, repeat the above process until the sand bed is at equilibrium.

[0099] When the sand is in the re-entrained state, at the current sand bed height h b0 and no sand bed iterative solution of equilibrium sand bed height h b1 , assuming all sand is suspended, h b1 = 0, calculate and pass the equivalent pipe diameter at this time D E , then use the steady state solution module to call the steady state flow model to update the liquid phase flow rate U L , calculate the sand concentration taking into account the dynamic behavior of the sand, calculate the critical sand deposition velocity after deposition U C , determine if the sand is fully entrained ( U L ≥ U CIf yes, output the current sand bed height and calculate the equivalent pipe diameter and thermal conductivity of the sand deposition equilibrium state; otherwise, assume a sand bed height within the iteration range. h b1 Then, the steady-state solution module is used to call the steady-state flow model to update the liquid phase velocity. U L The sand concentration was calculated considering the dynamic behavior of sand grains, and the critical flow velocity for sand deposition after initiation was calculated. U C Determine whether the sand bed is in a balanced state (| U L - U C | / U L If the sand bed height is less than 0.1%, output the current sand bed height and calculate the equivalent pipe diameter and thermal conductivity of the sand deposition equilibrium state. If not, repeat the above process until the sand bed is in equilibrium.

[0100] Furthermore, updating the pipe structure parameters includes calculating the equivalent diameter in the pipe structure parameters based on the sand bed height, and further calculating the thermal conductivity in the pipe structure parameters based on the equivalent diameter.

[0101] Specifically, the equivalent pipe diameter is calculated based on the reduction in pipe flow area caused by sand deposition. The equivalent pipe diameter is calculated using the following formula:

[0102]

[0103] In the formula, D Ei For the first i Equivalent pipe diameter of the section A i For the first i The cross-sectional area of ​​the segment V bi Let be the volume of the sedimentary sand grains in the i-th segment. φ For the porosity of the sand bed, Δ L i For the first i The length of the segment.

[0104] Furthermore, assuming that a thermally insulating layer composed of deposited sand particles is added to the inner wall of the pipe, the thermal conductivity of the pipe is corrected by combining the thermal conductivity of the sand particles. The formula for calculating the thermal conductivity is as follows:

[0105] ;

[0106] ;

[0107] ;

[0108] ;

[0109] wherein, U Ei is the thermal conductivity of the i section, R sandi , R walli , R insi are the sand grain thermal resistance, the pipe wall thermal resistance and the insulation layer thermal resistance of the i section, respectively, k sand , k walli , k insi are the sand grain thermal conductivity, the pipe wall thermal conductivity and the insulation layer thermal conductivity of the i section, respectively, δ walli , δ walli are the pipe wall thickness and the insulation layer thickness of the i section, respectively.

[0110] Further, updating the sand grain property parameters includes updating the sand grain mass concentration in the sand grain property parameters, and the calculation formula in the updating is as follows:

[0111] ;

[0112] ;

[0113] ;

[0114] ;

[0115] wherein, C Mi is the suspended sand grain mass concentration after the time step advancing of the i section, M i is the original suspended sand grain mass in the i section, M in , M out are the input and output sand grain masses in the time step advancing, respectively, Δ L i is the length of the i section, A i is the cross-sectional area of the i section, Δ t is the time step, C M(i-1) , Q (i-1)respectively the initial suspended sand mass concentration and fluid volume flow rate of the i suspended sand mass concentration and fluid volume flow rate of the front end unit of the segment, C Mi0 , Q i respectively the initial suspended sand mass concentration and fluid volume flow rate of the i suspended sand mass concentration and fluid volume flow rate of the front end unit of the segment, D i the inner diameter of the pipe of the segment. i

[0116] Step five, repeat steps two to four to perform time iteration calculation, and output the hydraulic and thermal parameters, sand deposition critical flow rate and sand bed height at each time and space as the prediction result after the iteration is completed.

[0117] The hydraulic and thermal parameters at each time and space can reflect the dynamic influence of sand deposition on the hydraulic and thermal characteristics of transient flow in the pipeline; the sand deposition critical flow rate and sand bed height at each time and space can reflect the dynamic process of the change of sand deposition characteristics along the line with time. After the sand deposition prediction calculation is completed, the calculation results at each time and space are stored in the calculator, and the calculation results of adjacent calculation units are transitioned through linear interpolation or smoothing processing method, the dynamic process of the change of sand deposition characteristics along the line with time can be output, and the change process of sand deposition characteristics of any pipe segment within a specified time can also be output, which can provide comprehensive sand deposition prediction analysis and risk warning for the gathering pipeline; for example, the sand deposition distribution of the entire pipeline can be obtained according to the sand bed height along the line to predict the sand deposition risk, when the sand bed height is greater than zero, it indicates that there is a sand deposition risk in the pipeline, and when the sand bed height is equal to zero, it indicates that there is no sand deposition risk in the pipeline.

[0118] To verify the prediction method of the embodiment, a gathering pipeline in a western oilfield is taken as the research object, and the sand deposition risk prediction research is carried out for the typical working condition, and the specific steps are as follows:

[0119] Firstly, the typical working condition information is obtained, the gathering pipeline is a undulating pipe with a diameter of 0.114 m and a length of 16 km, the conveying medium is oil, gas and water three-phase, the liquid phase flow rate is 320 m 3 / d, the gas phase flow rate is 8400 m 3 / d, the inlet temperature is 30℃, the outlet pressure is 1MPa, the sand mass concentration is 0.05%, and the sand particle size is 150 μm.

[0120] ​For oil-gas-water multiphase medium, the RKS component model is selected to compile the property calculation module to accurately describe the basic properties such as fluid density and viscosity under different temperatures and pressures; the Xiao double-fluid hydraulic model and the Dittus-Boelter thermodynamic model are selected to compile the transient flow calculation module to realize the coupled calculation of the hydraulic and thermal parameters along the pipeline; the Oroskar&Turian and Danielson sand deposition critical flow velocity models are combined to compile the sand deposition calculation module to accurately predict the sand deposition critical flow velocity and realize the prediction of the sand particle migration state.

[0121] In the sand deposition prediction and calculation process, the pipeline structure parameters are input and the pipeline is discretized to divide the calculation unit, the flow boundary condition parameters and sand property parameters and other calculation constants are input, the sand deposition prediction software is developed based on the compiled sand deposition prediction software, and the flow parameters such as temperature, pressure, gas-liquid flow rate of the gathering pipeline under stable flow conditions and the sand deposition critical flow velocity and sand deposition distribution are analyzed.

[0122] As shown in Figure 5 , the established pipeline route is as shown in Figure 5 , the predicted pressure and temperature are as shown in Figure 5 (b), the predicted critical flow velocity and liquid phase flow rate are as shown in Figure 5 (c), and the predicted sand deposition state is as shown in Figure 5 (d), through the analysis of Figure 5 , it can be seen that in the medium conveying process in the gathering pipeline, the pressure and temperature are continuously reduced due to the influence of hydraulic friction and environmental heat dissipation, the gas volume flow rate is increased to cause the fluid velocity to be increased, the fluid sand carrying capacity is enhanced. In the upward inclined pipe, the fluid kinetic energy is converted into gravitational potential energy, the fluid velocity is reduced, the sand carrying capacity is limited, and at the same time, the gravity component of the sand particles in the upward inclined pipe is opposite to the migration direction, the liquid phase drag force required for sand particle migration is large, the sand deposition critical flow velocity is increased, and the sand deposition risk exists in the operation of the gathering pipeline, which is mainly concentrated in the inlet upward inclined pipe section.

[0123] The prediction method of the embodiment is used to simulate and analyze the dynamic sand deposition process of a 3km horizontal pipe as a typical pipeline structure. The calculation results are shown in Figure 6 , the sand particles start to accumulate from the inlet section, the sand bed height is continuously increased with time, and when the sand bed reaches the equilibrium height, the suspended sand particles are transported to the next unit with the fluid, and the dynamic updating of the sand bed along the pipeline is realized. The results clearly show the dynamic deposition process of the sand particles in the pipeline and the sand bed evolution law, which shows that the present application can provide a quantitative reference for sand deposition risk prediction.

[0124] The prediction method of the embodiment is used to simulate and analyze the sand-carrying restart process for a 3km horizontal pipe as a typical pipe structure. The calculation results are shown in Figure 7 As shown in the figure, after the pipe conveying flow rate is increased, the high-speed fluid is gradually transmitted from the inlet to the rear at 0s, 20s and 40s, the sand particles start to restart from the inlet section, the sand bed height gradually decreases with time, until the sand particles are completely suspended, the sand bed height is reduced to zero, and then the dynamic updating of the sand bed along the pipe is realized. The results clearly show that the carrying effect of the high-speed fluid on the sand particles makes the sand bed dissipate from the inlet to the rear section of the pipe, reflecting the dynamic restart process of the sand particles in the pipe and the evolution law of the sand bed, and indicating that the present application can provide a quantitative reference for the sand control of the pipe.

[0125] The prediction method provided by the embodiment realizes the coupled calculation of the flow parameters and the sand deposition characteristics in the operation process of the gathering pipeline, can predict the sand deposition risk in the operation of the pipeline, provides a scientific basis for the sand control and risk avoidance of the pipeline, and effectively guarantees the safety and stability of the operation of the gathering pipeline.

[0126] Embodiment 2

[0127] In a typical embodiment of the present embodiment, an oil and gas gathering pipeline sand deposition dynamic prediction system is provided, as shown in Figure 8 The pipeline structure model construction module 100 is configured to: acquire pipeline structure parameters, establish a pipeline structure model according to the pipeline structure parameters, and discretize the pipeline structure model to divide calculation units;

[0128] The transient flow calculation module 200 is configured to: acquire the basic physical property parameters of the fluid medium and the sand particle attribute parameters in the pipeline, define the flow boundary conditions of the pipeline structure model, and combine the pipeline structure parameters to perform spatial iterative calculation of the hydraulic and thermal parameters of the whole pipeline by using a transient flow model coupled with a thermodynamic model;

[0129] The sand particle migration state determination module 300 is configured to: based on the pipeline structure parameters, the basic physical property parameters of the fluid medium, the sand particle attribute parameters and the hydraulic and thermal parameters, calculate the sand deposition critical flow velocity along the pipeline by using a sand deposition critical flow velocity model, compare the sand deposition critical flow velocity along the pipeline with the flow velocity of the fluid medium in the hydraulic and thermal parameters, and determine the sand particle migration state;

[0130] The parameter updating module 400 is configured to: calculate the deposition sand bed height along the pipeline according to the sand particle migration state, and update the pipeline structure parameters and the sand particle attribute parameters;

[0131] The parameter updating module 400 is configured to: calculate the deposition sand bed height along the pipeline according to the sand particle migration state, and update the pipeline structure parameters and the sand particle attribute parameters;

[0132] The prediction result output module 500 is configured to repeatedly perform the time step iteration calculation of steps two to four, and output the hydraulic and thermal parameters, the sand deposition critical flow velocity and the sand bed height at each time and space as the prediction results after the iteration is completed.

[0133] Although the specific embodiments of the present application are described above with reference to the drawings, the description is not a limitation on the scope of protection of the present application, and those skilled in the art should understand that various modifications or changes made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the scope of protection of the present application.

Claims

1. A method for predicting the dynamics of sand deposition in oil and gas gathering and transportation pipelines, characterized in that, Includes the following steps: Step 1: Obtain pipeline structure parameters, establish a pipeline structure model based on the pipeline structure parameters, and discretize the pipeline structure model to divide it into calculation units; Step 2: Obtain the basic physical property parameters of the fluid medium and the sand particle properties parameters in the pipeline, define the flow boundary conditions of the pipeline structure model, and combine the pipeline structure parameters to perform spatial iterative calculation of the hydraulic and thermal parameters of the entire pipeline using a transient flow model coupled with a thermodynamic model. Step 3: Based on the pipeline structure parameters, the basic physical properties of the fluid medium, the sand grain properties, and the hydraulic and thermal parameters, the critical velocity model for sand deposition is used to calculate the critical velocity for sand deposition along the pipeline. The critical velocity for sand deposition along the pipeline is then compared with the fluid medium velocity in the hydraulic and thermal parameters to determine the sand grain migration state. When the liquid phase flow rate is equal to the critical flow rate for sand deposition, the equilibrium state is reached. When the liquid phase flow velocity is less than the critical flow velocity for sand deposition, it is in the depositional state. When the liquid flow velocity is greater than the critical flow velocity for sand deposition, if no sand bed is formed, it is a non-deposition state; if a sand bed exists and the fluid carries sand and restarts, it is a restart state. Step 4: Calculate the height of the sedimentary sand bed along the pipeline based on the sand grain migration state, and update the pipeline structural parameters and sand grain property parameters; When calculating the height of the sedimentary sand bed along the pipeline based on the sand grain migration state, the height of the sedimentary sand bed inside the pipeline is iteratively calculated based on the steady-state flow model, according to the sand grain migration state: If the sand grains are in a state of sand deposition equilibrium, the height of the sedimentary sand bed remains unchanged; If the sand grains are in a sand deposition state, then the equilibrium sedimentary sand bed height is iteratively calculated between the current sedimentary sand bed height and the height of the suspended sand grains after complete deposition. If the sand grains are in a state of continuous movement and no deposition, then the height of the sedimentary sand bed is zero; If the sand grains are in a sand-carrying restart state, the equilibrium sedimentary sand bed height is iteratively calculated between the height of the sand-free bed and the current sedimentary sand bed height. Step 5: Repeat steps 2 to 4 to perform time-step iterative calculations. After the iteration is completed, output the hydraulic and thermal parameters, critical flow velocity for sand deposition, and sedimentary sand bed height for each time and space as the prediction results.

2. The method for dynamic prediction of sand deposition in oil and gas gathering and transportation pipelines as described in claim 1, characterized in that, When iteratively calculating the sand bed height in a pipeline based on a steady-state flow model, a relationship between the sand bed height and the volume of deposited sand grains is established through geometric relationships for iterative calculation. The established relationship is as follows: In the formula, A bi For the first i The cross-sectional area of ​​the sedimentary sand grains in the section, V bi For the first i The volume of sedimentary sand grains in the section, φ For the porosity of the sand bed, Δ L i For the first i The length of the segment D i For the first i The inner diameter of the section of pipe, h bi For the first i The height of the sedimentary sand bed in the section.

3. The method for dynamic prediction of sand deposition in oil and gas gathering and transportation pipelines as described in claim 1, characterized in that, In step four, updating the pipe structure parameters includes calculating the equivalent diameter in the pipe structure parameters based on the sand bed height, and further calculating the thermal conductivity in the pipe structure parameters based on the equivalent diameter.

4. The method for predicting the dynamic deposition of sand in oil and gas gathering and transportation pipelines as described in claim 3, characterized in that, The equivalent diameter is calculated using the following formula: In the formula, D Ei For the first i Equivalent pipe diameter of the section A i For the first i The cross-sectional area of ​​the segment V bi Let be the volume of the sedimentary sand grains in the i-th segment. φ For the porosity of the sand bed, Δ L i For the first i The length of the segment.

5. The method for dynamic prediction of sand deposition in oil and gas gathering and transportation pipelines as described in claim 3, characterized in that, The formula for calculating the thermal conductivity is as follows: ； ； ； ； In the formula, U Ei For the first i The thermal conductivity of the section R sandi , R walli , R insi The first i The thermal resistance of the sand particles, the thermal resistance of the pipe wall, and the thermal resistance of the insulation layer in the section. k sand , k walli , k insi These are the thermal conductivity of sand particles, respectively. i The thermal conductivity of the pipe wall and the thermal conductivity of the insulation layer of the section, δ walli δ walli The first i The thickness of the pipe wall and the thickness of the insulation layer of the section.

6. The method for dynamic prediction of sand deposition in oil and gas gathering and transportation pipelines as described in claim 3, characterized in that, Updating sand grain property parameters includes updating the sand grain mass concentration. The calculation formula for the update is as follows: ； ； ； ； In the formula, C Mi For the first i The mass concentration of suspended sand particles after each step of the segment's propulsion. M i For the first i The original suspended sand particles in the section, M in , M out These represent the input and output sand particle masses during time-step propulsion, Δ L i For the first i The length of the segment A i For the first i The cross-sectional area of ​​the segment, Δ t For time step, C M(i-1) , Q (i-1) The first i The suspended sand particle mass concentration and fluid volumetric flow rate of the front-end unit of the section. C Mi0 , Q i The first i The initial suspended sand particle mass concentration and fluid volumetric flow rate of the segment, D i For the first i The inner diameter of the pipe section.

7. The method for dynamic prediction of sand deposition in oil and gas gathering and transportation pipelines as described in claim 1, characterized in that, The sand deposition distribution of the entire pipeline is obtained by measuring the height of the sand bed along the pipeline to predict the sand deposition risk. When the height of the sand bed is greater than zero, it indicates that there is a sand deposition risk in the pipeline. When the height of the sand bed is equal to zero, it indicates that there is no sand deposition risk in the pipeline.

8. A dynamic prediction system for sand deposition in oil and gas gathering and transportation pipelines, characterized in that, include: The pipeline structure model building module is configured to: obtain pipeline structure parameters, build a pipeline structure model based on the pipeline structure parameters, and discretize the pipeline structure model to divide it into computational units; The transient flow calculation module is configured to: obtain the basic physical property parameters of the fluid medium and the sand particle property parameters in the pipeline, define the flow boundary conditions of the pipeline structure model, and combine the pipeline structure parameters to perform spatial iterative calculation of the hydraulic and thermal parameters of the entire pipeline using a transient flow model coupled with a thermodynamic model. The sand particle transport state determination module is configured to: calculate the critical flow velocity of sand deposition along the pipeline using the critical flow velocity model of sand deposition, based on the pipeline structure parameters, the basic physical property parameters of the fluid medium, the sand particle property parameters, and the hydraulic and thermal parameters; compare the critical flow velocity of sand deposition along the pipeline with the fluid medium flow velocity in the hydraulic and thermal parameters to determine the sand particle transport state. When the liquid phase flow rate is equal to the critical flow rate for sand deposition, the equilibrium state is reached. When the liquid phase flow velocity is less than the critical flow velocity for sand deposition, it is in the depositional state. When the liquid flow velocity is greater than the critical flow velocity for sand deposition, if no sand bed is formed, it is a non-deposition state; if a sand bed exists and the fluid carries sand and restarts, it is a restart state. The parameter update module is configured to: calculate the height of the sedimentary sand bed along the pipeline based on the sand grain migration state, and update the pipeline structural parameters and sand grain property parameters; When calculating the height of the sedimentary sand bed along the pipeline based on the sand grain migration state, the height of the sedimentary sand bed inside the pipeline is iteratively calculated based on the steady-state flow model, according to the sand grain migration state: If the sand grains are in a state of sand deposition equilibrium, the height of the sedimentary sand bed remains unchanged; If the sand grains are in a sand deposition state, then the equilibrium sedimentary sand bed height is iteratively calculated between the current sedimentary sand bed height and the height of the suspended sand grains after complete deposition. If the sand grains are in a state of continuous movement and no deposition, then the height of the sedimentary sand bed is zero; If the sand grains are in a sand-carrying restart state, the equilibrium sedimentary sand bed height is iteratively calculated between the height of the sand-free bed and the current sedimentary sand bed height. The prediction result output module is configured to repeat steps two through four to perform time-step iterative calculations, and after the iteration is completed, output the hydraulic and thermal parameters, critical flow velocity for sand deposition, and sedimentary sand bed height at each time and space as prediction results.

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