CN110377879B - Method for calculating normal-temperature gathering and transporting radius of oil-gas-water mixed transportation pipeline - Google Patents
Method for calculating normal-temperature gathering and transporting radius of oil-gas-water mixed transportation pipeline Download PDFInfo
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Abstract
The invention relates to a method for calculating the normal-temperature gathering and transporting radius of an oil-gas-water mixed transportation pipeline, which comprises the following steps: measuring physical parameters of the crude oil, and establishing mathematical models of different physical parameters; calculating the thermal radius of normal-temperature gathering and transportation; calculating the radius of the normal-temperature gathering and transportation hydraulic power; aiming at an oil field production block, establishing a thermal constraint array, and determining a thermal constraint radius; and establishing a hydraulic power constraint array, determining a hydraulic power constraint radius, and calculating to obtain a normal-temperature gathering and transportation radius. The method can comprehensively consider the thermal characteristics and hydraulic characteristics of the oil-gas-water mixed transportation pipeline according to the related physical parameters of the crude oil and the actual operation conditions of the pipeline, establish a temperature drop and pressure drop mathematical model of the oil-gas-water mixed transportation pipeline, determine the normal-temperature gathering and transportation radius, has scientificity and comprehensiveness, can be applied to different production blocks of different oil fields to determine the normal-temperature gathering and transportation radius, has strong adaptability, and can provide reference for the normal-temperature gathering and transportation work of the oil field ground engineering.
Description
Technical Field
The invention belongs to the technical field of oil and gas storage and transportation, and particularly relates to a method for calculating the normal-temperature gathering and transportation radius of an oil-gas-water mixed transportation pipeline.
Background
As one of the main processes of oil field ground production, the oil-gas-water mixed transportation technology is generally used to transport crude oil, associated gas and produced water produced from an oil well to related processing sites such as a metering station, a transfer station, a combination station and an oil refinery by laying the oil-gas-water mixed transportation technology underground, on the ground or in an overhead pipeline. The crude oil produced in most oil fields in China is 'three-high' crude oil with high wax content, high condensation point and high viscosity, and the oil needs to be heated and conveyed in order to prevent the oil from condensing in a pipeline and reduce the friction loss in the oil conveying process, and the heat energy consumption of the oil can account for 50-70% of the total energy consumption of a gathering and conveying system, so that the oil has a dominant position. On the other hand, as the oil field enters the later stage of exploitation, the comprehensive water content is gradually increased, so that the heating energy consumption is further increased. Therefore, how to carry out normal temperature gathering and transportation to reduce heat energy consumption is a key and difficult problem faced by oil field sites.
The determination of the normal-temperature gathering and transporting radius is the key of the normal-temperature gathering and transporting operation management, and particularly aims at an oil-gas-water multiphase mixed transportation pipeline, so that not only the thermal constraint condition but also the hydraulic constraint condition need to be met. The thermal constraint condition means that the temperature of the mixed transportation fluid in the transportation process is above the freezing point, so that safety accidents such as pipe condensation and the like are avoided; the hydraulic constraint condition means that under a certain pipe conveying pressure, the mixed conveying fluid can overcome the flow resistance and can be conveyed to the oil transfer station. So far, in the oil field single well pipeline gathering and transportation process, field technicians generally determine the single well normal temperature gathering and transportation radius through practice groping and operation management experience, and the hydraulic and thermal characteristics of the gathering and transportation radius are not comprehensively considered, so that the feasibility of normal temperature gathering and transportation cannot be scientifically and comprehensively analyzed. Generally, the boundary condition of normal-temperature gathering and transportation is still in the summary stage of on-site experience exploration, and the guidance in the theoretical aspect is lacked, so that the workload of on-site technicians is large, the universality is not realized, and the reference value is low.
In summary, the conventional method for determining the normal-temperature gathering and transporting radius of the oil-gas-water mixed transportation pipeline has certain limitations, and the corresponding normal-temperature gathering and transporting radius is difficult to set for different blocks of different oil fields, so that difficulty is brought to popularization of normal-temperature gathering and transporting.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a method for calculating the normal-temperature gathering and transporting radius of an oil-gas-water mixed transportation pipeline, which can avoid the technical defects.
In order to achieve the above object, the present invention provides the following technical solutions:
a method for calculating the normal-temperature gathering and transporting radius of an oil-gas-water mixed transportation pipeline comprises the following steps:
step 1) measuring physical parameters of crude oil, and establishing mathematical models of different physical parameters;
step 2), calculating the radius of the normal-temperature gathering and transportation heat power;
step 3) calculating the hydraulic radius of normal-temperature gathering and transportation;
step 4), establishing a thermodynamic constraint array, and determining a thermodynamic constraint radius; establishing a hydraulic constraint array, and determining a hydraulic constraint radius; and calculating by combining the thermal constraint radius and the hydraulic constraint radius to obtain the normal-temperature gathering and transportation radius.
Further, the method comprises:
step 1) measuring various physical parameters of crude oil at different temperatures aiming at an oil field production block, and establishing a physical parameter model of the crude oil by using a linear or nonlinear regression method;
step 2) taking an oil-gas-water mixed transportation pipeline as a research object, determining the qualitative temperature of the fluid in the transportation process by using the lowest allowable station-entering temperature of the starting point temperature and the terminal point of the pipeline, obtaining the related physical property parameters of crude oil and an oil-water liquid phase at the temperature, and further obtaining the heat transfer coefficient from the fluid to the inner wall of the pipe, the heat transfer coefficient from the outer wall of the pipe to soil and the total heat transfer coefficient from crude oil, the pipeline and the soil; calculating absolute average pressure and gas phase critical parameters of the pipeline at the same time, obtaining a Joule-Thomson effect coefficient on the basis, determining the mass specific heat capacity of the oil-gas-water mixture through the gas phase mass specific heat capacity and the gas phase mass fraction, establishing an oil-gas-water mixed transportation pipeline temperature drop mathematical model by combining the mass flow of the oil-gas-water mixture, and obtaining the normal temperature gathering and transportation thermal radius through an iterative calculation method;
step 3) determining the average flow velocity of the gas-liquid mixture according to the volume flow of the oil-liquid phase and the gas phase in the pipeline, obtaining the dynamic viscosity of the gas-liquid mixture by utilizing the physical parameters of crude oil, simultaneously calculating the density of the gas-liquid mixture and the Reynolds number and the liquid holdup rate in a mixed transportation pipeline by adopting a circulation iteration method, further determining a mixed transportation resistance coefficient, establishing an oil-gas-water mixed transportation pipeline pressure drop model, determining the maximum pressure drop of the pipeline according to the lowest allowable station-entering pressure of the starting point pressure and the end point of the pipeline, and substituting the maximum pressure drop of the pipeline into the model to obtain the normal-temperature hydraulic power collection and transportation radius;
and 4) establishing a thermal constraint array of the production block, determining the thermal constraint radius of the block, establishing a hydraulic constraint array according to the hydraulic radius, determining the hydraulic constraint radius of the block, and obtaining the normal-temperature gathering and transportation radius of the production block by combining thermal constraint and hydraulic constraint conditions.
Further, in the step 1),
the crude oil density-temperature relation calculation formula is as follows: rho o ＝ρ 20 -ξ(T-20)
ρ o 、ρ 20 Crude oil densities at T ℃ and 20 ℃ respectively; xi is temperature coefficient, 1.825-0.001315 rho 20 ；
The formula for performing nonlinear regression on the viscosity-temperature curve of the crude oil is as follows:
crude oil exhibits properties of newtonian fluids:
crude oil is a non-newtonian fluid:
μ o is the dynamic viscosity of crude oil at T ℃; t is the crude oil temperature; a. the 1 、A 2 、B 1 、B 2 、C 1 、C 2 Is a coefficient;
dividing a specific heat capacity-temperature curve into three regions according to the wax precipitation point temperature and the maximum specific heat capacity temperature to perform nonlinear regression;
when the oil temperature is higher than the wax precipitation point temperature: c. C o ＝H 1 T 2 +E 1 T+F 1 ；
When the oil temperature is less than the wax precipitation point temperature and greater than the maximum specific heat capacity temperature: c. C o ＝H 2 T 2 +E 2 T+F 2 ；
When the oil temperature is less than the maximum specific heat capacity temperature: c. C o ＝H 3 T 2 +E 3 T+F 3 ；
c o Crude oil specific heat capacity at T; t is the crude oil temperature; h 1 、H 2 、H 3 、E 1 、E 2 、E 3 、F 1 、F 2 、F 3 Is a coefficient;
the heat conductivity of the crude oil is calculated according to the following formula:
λ o the heat conductivity coefficient of the oil product when the oil temperature is T; t is the oil temperature; rho 15 Is the density of the oil product at 15 ℃.
Further, in step 2),
c L ＝c w σ+c o (1-σ)
c L the specific heat capacity of oil-water-liquid phase; c. C w Is the specific heat capacity of water; c. C o Is the specific heat capacity of the crude oil; sigma is the mass water content;
q L ＝q w +q o
G L the mass flow of the oil-water liquid phase; q. q.s w Is the water volume flow; sigma is the mass water content; q. q.s o Is the crude oil volumetric flow rate; rho o Is the crude oil density; q. q.s L Is the oil-water liquid phase volume flow;
the water content is the volume water content;
heat transfer coefficient alpha of oil flowing to inner wall of pipe 1 ，
In the case of a laminar flow of fluid,
λ y is the heat conductivity coefficient of crude oil; upsilon is y Is the kinematic viscosity of the crude oil; c. C y The specific heat capacity of the crude oil; beta is a y The volume expansion coefficient of the crude oil; g is the acceleration of gravity; re y Is Reynolds number; rho y Is the crude oil density; d 1 Is the inner diameter of the pipeline;
determining the temperature of the pipeline; t is bi Determining the temperature of the tube wall; t is t 0 The ambient temperature of the pipeline; n is a radical of hydrogen y Parameters determined by using the physical properties of the crude oil at the oil flow-determining temperature, N bi The parameters are obtained by using the physical property parameters of the crude oil at the qualitative temperature of the pipe wall;
in the case of a turbulent flow of the fluid,
when the flow regime is in the transition region,
heat transfer coefficient alpha from outer wall of pipe to soil 2 Calculated as follows:
λ t is the soil thermal conductivity; h is t Burying the center of the tube deeply; d w The outer diameter of the pipe contacted with the soil, namely the outer diameter formed by an outer anticorrosive layer or a heat-insulating layer of the steel pipe;
α 1 the heat transfer coefficient of oil flowing to the inner wall of the tube; alpha is alpha 2 The heat transfer coefficient from the outer wall of the tube to the soil; d is the calculated diameter; d i 、D (i+1) The inner diameter and the outer diameter of the steel pipe and the heat-insulating layer; lambda [ alpha ] i Is the coefficient of thermal conductivity; k is the total heat transfer coefficient of crude oil-pipeline-soil.
Further, in step 2), the average pressure is determined by using the pipeline starting point pressure and the lowest allowable arrival pressure of the end point according to the following formula:
p pj1 is the gas phase average pressure; p is a radical of Q Is the starting pressure; p is a radical of Z Lowest permissible inbound pressure for the terminal;
in the formula, p pj2 Is the gas phase mean absolute pressure;
the critical pressure and critical temperature of the gas phase were calculated as follows:
in the formula, p c Critical pressure in the gas phase; t is c Critical temperature in the gas phase; n is the natural gas component number; y is i Is the mole fraction of the i component; p is a radical of ci And T ci Critical pressure and critical temperature for the pure i component;
the comparison pressure and the comparison temperature were found by the following formula:
in the formula, p r 、T r Comparing pressure and temperature; p is a radical of c 、p pj2 Critical pressure and absolute mean pressure of the gas; t is c 、
The critical temperature of the gas and the qualitative temperature of the pipeline.
Further, in step 2), the gas phase average relative molecular mass is calculated as follows:
M g ＝∑M i y i
in the formula, y i Is the mole fraction of the i component; m i Is the relative molecular mass of the i component;
the gas phase constant pressure molar heat capacity was calculated as follows:
in the formula, c p Gas phase constant pressure molar heat capacity;
determining the temperature of the pipeline; m g Is the gas phase average relative molecular mass; p is a radical of formula pj1 Is the average pressure;
the joule-thomson effect coefficient is calculated as follows:
f(p r ,T r )＝2.343T r -2.04 -0.071p r +0.0568
in the formula, D jt Is the joule-thomson effect coefficient; c. C p Is a constant pressure molar heat capacity; p is a radical of c A critical pressure; t is a unit of c A critical temperature; p is a radical of r And T r Comparing pressure and temperature;
gas phase mass specific heat capacity:
c g is gas phase mass specific heat capacity; c. C p Is a constant pressure molar heat capacity; m g Is the gas phase average relative molecular mass;
G g ＝ρ g q g
x is the mass fraction of the gas phase; g g Is the gas phase mass flow rate; ρ is a unit of a gradient g Is the gas phase density; q. q of g Is a gas phase volume flow rate; g L The mass flow of the oil-water liquid phase;
c m ＝c g x+c L (1-x)
c m the specific heat capacity of the oil-gas-water mixture; x is gas phase mass fraction; c. C g The gas phase mass specific heat capacity; c. C L The specific heat capacity of oil-water-liquid phase;
G m ＝G L +G g
G m the mass flow rate of the oil-gas-water mixture; g L The mass flow of the oil-water liquid phase; g g Is the gas phase mass flow rate.
Further, in step 2), assume L T The initial value of the temperature difference is 0.1, and an axial temperature drop model of the oil-gas-water mixed transportation pipeline is established as follows:
L T the length from the starting point of the pipeline to any point along the line; t is t L Is a starting point L of the distance from the pipeline T Oil flow temperature at rice; t is t 0 Is an outer ring of a tubeAmbient temperature; t is a unit of R The starting temperature of the pipeline is shown, and e is a natural logarithm base number; k is the total heat transfer coefficient; d jt Is the joule-thomson effect coefficient; c. C g The gas phase mass specific heat capacity; d is the calculated diameter; p is a radical of formula Q Is the starting pressure; p is a radical of formula Z The lowest allowable inbound pressure for the terminal;
calculating the length of the tube as L T End point temperature t of the pipeline L Judging whether the relative error between the temperature value and the lowest allowable temperature of the pipeline end point is less than 5%; if less than 5%, L at this time T Namely the gathering and transmission radius under the thermal constraint; if not less than 5%, adopting iterative calculation method, and using 0.1 as step length to make L T Are accumulated to respectively calculate different L T T is L Until the relative error between the temperature value and the lowest allowable temperature of the end point of the pipeline is less than 5%, then L at the moment T Namely the gathering and transporting radius under the thermal constraint.
Further, in the step 3),
q m ＝q L +q g
q m is the volume flow of the gas-liquid mixture; q. q of L The volume flow of oil-water liquid phase; q. q.s g A volume flow in the gas phase;
the average flow rate of the gas-liquid mixture can be calculated as follows:
v m is the average flow rate of the gas-liquid mixture; q. q.s m Is the volume flow of the gas-liquid mixture; d 1 Is the inner diameter of the pipeline;
R L ＝q L /q m
μ m ＝μ L R L +μ g (1-R L )
μ L 、μ g the dynamic viscosity of oil-water liquid phase and gas phase;
the water content is the volume water content; μ o is the kinematic viscosity of the crude oil; mu.s w Is the kinetic viscosity of water; r L Is the volume liquid content; q. q of L The volume flow of oil-water liquid phase; q. q of m Is the volume flow of the gas-liquid mixture.
Further, in step 3), a trial algorithm is used to determine the liquid holdup H L The method comprises the following steps:
first, suppose the liquid holdup H L Calculating the average density of the gas-liquid mixture:
ρ m is the average density of the gas-liquid mixture; rho L 、ρ g The density of oil-water liquid phase and gas phase; r L Is the volume liquid content; h L Is the cross-sectional liquid content;
calculating mixed transport Reynolds number
Re m Is the mixed transportation Reynolds number; d 1 Is the inner diameter of the pipeline;
then, according to different mixed transportation Reynolds numbers Re m Calculating H by the following relation L ：β＝lg R L +3，
R L Is the volume liquid content;
when Re m When R is 1, R L And H L The mathematical expression of the relationship is:
lgH L ＝1.98975289+0.4192759β-0.3517347β 2 +0.0627002β 3 +0.00611271β 4 -0.001097β 5 -2
when Re m When R is 100, R L And H L The mathematical expression of the relationship is:
lgH L ＝1.53077259+0.4562775β-0.3097665β 2 +0.0718006β 3 +0.01101236β 4 -0.003875β 5 -2
when Re m When R is 500, R L And H L The mathematical expression of the relationship is:
lgH L ＝1.15927438+0.5157858β-0.0104859β 2 -0.1975919β 3 +0.10033697β 4 -0.01400916β 5 -2
when Re m When R is 1000 L And H L The mathematical expression of the relationship is:
lgH L ＝0.86228039+0.7941742β-0.0414958β 2 -0.3076484β 3 +0.16093553β 4 -0.0230459β 5 -2
when Re m When equal to 2500, R L And H L The mathematical expression of the relationship is:
lgH L ＝0.61121528+0.8219817β+0.2450638β 2 -0.591696β 3 +0.26550666β 4 -0.03627456β 5 -2
when Re m When 5000, R L And H L The mathematical expression of the relationship is:
lgH L ＝0.37037426+1.1458724β-0.1024697β 2 -0.3317119β 3 +0.17193205β 4 -0.02410223β 5 -2
when Re m When 10000, R L And H L The mathematical expression of the relationship is:
lgH L ＝0.21324017+0.9846183β+0.4538199β 2 -0.7934965β 3 +0.32817872β 4 -0.04284162β 5 -2
when Re m When 25000, R L And H L The mathematical expression of the relationship is:
lgH L ＝-0.040313231+0.94664475β+0.7145845β 2 -0.9824665β 3 +0.3845391β 4 -0.048779381β 5 -2
when Re m R is 50000 L And H L The mathematical expression of the relationship is:
lgH L ＝-0.22287976+0.8475579β+0.7621021β 2 -0.9112905β 3 +0.3433659β 4 -0.042773693β 5 -2
when Re m When 100000, R L And H L The mathematical expression of the relationship is:
lgH L ＝-0.3672887+0.437131β+1.266505β 2 -1.157105β 3 +0.4060284β 4 -0.04932038β 5 -2
when Re m When 200000, R L And H L The mathematical expression of the relationship is:
lgH L ＝-1.272218+2.227224β-0.86396β 2 +0.092496β 3 +0.067676β 4 -0.0149087β 5 -2
reynolds number Re of oil-gas-water mixed conveying pipeline m If the value of (A) is not any of the Reynolds numbers mentioned above, two Reynolds numbers Re are selected from the Reynolds numbers mentioned above m1 And Re m2 The liquid holdup is determined by interpolation, and H is calculated as follows L ：
In the formula, H L1 When Reynolds number equals Re m1 Calculated liquid holdup H L2 When Reynolds number equals Re m2 Calculating the obtained liquid holding rate; [ Re ] m1 ,Re m2 ]Satisfies Re in the range of all Reynolds numbers m1 <Re m <Re m2 The minimum interval of this condition;
finally, the recalculated H is judged L Whether the relative error between the value and its assumed value is less than 5%, e.g. not less than the re-assumed H L And repeating the above steps until H L Assuming that the relative error between the value and the calculated value is less than 5%;
the mixed transportation resistance coefficient calculation formula is as follows:
S＝1.281-0.478(-lnR L )+0.444(-lnR L ) 2 -0.094(-lnR L ) 3 +0.00843(-lnR L ) 4
phi is the ratio of the mixed transportation resistance coefficient to the oil-water liquid phase resistance coefficient,
the pressure drop model of the oil-gas-water mixed transportation pipeline is established as follows:
delta p is the pressure drop of the oil-gas-water mixed transportation pipeline; lambda [ alpha ] m The mixed transportation resistance coefficient; rho m Is the average density of the gas-liquid mixture; v. of m Is the average flow rate of the gas-liquid mixture; l is the length of the pipeline; d 1 Is the inner diameter of the pipeline;
the gathering and transportation radius under hydraulic constraint is as follows:
further, in step 4),
L T ＝min(L T1 ,L T2 ,L T3 ,…,L Tk )
L P ＝min(L P1 ,L P2 ,L P3 ,…,L Pk )
L＝min(L T ,L P )
in the formula, L T The gathering and transmitting radius of the block under the thermal constraint condition; l is T1 ,L T2 ,L T3 ,…,L Tk Respectively numbering 1-k pipelines, and collecting and transmitting radiuses under thermal constraint; l is P The normal temperature gathering and transporting radius of the block under the hydraulic constraint condition; l is P1 ,L P2 ,L P3 ,…,L Pn Are respectively numbered 1 to k tubesGathering and transporting radius under hydraulic constraint of the road; l is the normal temperature gathering and transporting radius of the block.
The method for calculating the normal-temperature gathering and transporting radius of the oil-gas-water mixed transporting pipeline provided by the invention can be used for establishing a temperature drop and pressure drop mathematical model of the oil-gas-water mixed transporting pipeline according to related physical property parameters of crude oil and actual operating conditions of the pipeline and comprehensively considering the thermodynamic and hydraulic properties of the oil-gas-water mixed transporting pipeline aiming at an oil field production block, and determining the normal-temperature gathering and transporting radius, is different from the normal-temperature gathering and transporting radius summarized by field technicians of an oil field according to operation management experience in the prior art, and has scientificity and comprehensiveness; meanwhile, different production blocks of different oil fields can be determined by the method to determine the normal-temperature gathering and transporting radius, so that the method has strong adaptability, can provide guiding reference for normal-temperature gathering and transporting work of oil field ground engineering, and can well meet the requirements of practical application.
Drawings
FIG. 1 is a graph of crude oil variation density-temperature parameters.
FIG. 2 is a graph of crude oil rheology viscosity versus temperature parameters.
FIG. 3 is a graph of crude oil denatured specific heat capacity versus temperature parameter.
FIG. 4 is a graph of thermal conductivity versus temperature parameters for crude oil with varying physical properties.
Fig. 5 is a flow chart of calculation of the thermal radius of the normal-temperature gathering and transportation under the thermal constraint condition.
FIG. 6 is a flow chart of calculation of hydraulic radius of normal-temperature gathering and transportation under hydraulic constraint conditions.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A method for calculating the normal-temperature gathering and transportation radius of a crude oil pipeline comprises the following steps:
the method comprises the following steps: the physical parameters of the crude oil, such as density, viscosity, specific heat capacity, heat conductivity coefficient and the like, are measured by using an indoor experimental instrument at different temperatures. Summarizing the change rules of the physical property parameters, performing linear and nonlinear regression on the measured data, and establishing mathematical models of different physical property parameters. Wherein, the crude oil density decreases along with the increase of the oil temperature, and a crude oil density-temperature relation curve can be calculated according to the following formula:
ρ o ＝ρ 20 -ξ(T-20)
in the formula, ρ o 、ρ 20 Is the crude oil density at T ℃ and 20 ℃, kg/m 3 (ii) a Xi is temperature coefficient, 1.825-0.001315 rho 20 。
The viscosity of the crude oil also decreases with increasing oil temperature, the crude oil exhibits properties of a non-Newtonian fluid when the oil temperature is below an abnormal point, and the crude oil exhibits properties of a Newtonian fluid when the oil temperature is above the abnormal point, and the viscosity-temperature curve of the crude oil can be subjected to a non-linear regression using the following formula:
newtonian fluids:
non-Newtonian fluids:
in the formula, mu o Is the dynamic viscosity of the crude oil at T ℃, Pa s; t is the crude oil temperature; a. the 1 、A 2 、B 1 、B 2 、C 1 、C 2 Are coefficients.
The specific heat capacity of the crude oil has different change rules in different temperature ranges, and a specific heat capacity-temperature curve can be divided into three regions according to the wax precipitation point temperature and the maximum specific heat capacity temperature to perform nonlinear regression.
When the oil temperature is higher than the wax precipitation point temperature:
c o ＝H 1 T 2 +E 1 T+F 1
when the oil temperature is less than the wax precipitation point temperature and greater than the maximum specific heat capacity temperature:
c o ＝H 2 T 2 +E 2 T+F 2
when the oil temperature is less than the maximum specific heat capacity temperature:
c o ＝H 3 T 2 +E 3 T+F 3
in the formula, c o Is the specific heat capacity of crude oil at T ℃, J/(kg. DEG C); t is the crude oil temperature, DEG C; h 1 、H 2 、H 3 、E 1 、E 2 、E 3 、F 1 、F 2 、F 3 Are coefficients.
The heat conductivity of crude oil also changes with temperature and can be calculated according to the following formula:
in the formula, λ o Is the heat conductivity coefficient of the oil product at T ℃, W/(m DEG C); t is the oil temperature, DEG C; ρ is a unit of a gradient 15 The density of the oil product at 15 ℃, kg/m 3 。
Step two: the method comprises the following steps of taking an oil-gas-water mixed transportation pipeline as a research object, and calculating the qualitative temperature of the pipeline according to the following formula by utilizing the lowest allowable station-entering temperature of the starting point temperature and the terminal point of the pipeline:
in the formula (I), the compound is shown in the specification,
the qualitative temperature of the pipeline is measured at DEG C; t is a unit of R The starting temperature of the pipeline is DEG C; t is L The lowest allowable station entering temperature of the terminal point of the pipeline is DEG C.
After the physical property parameters of the crude oil at the qualitative temperature are obtained, the specific heat capacity of the oil-water liquid phase is calculated according to the following formula:
c L ＝c w σ+c o (1-σ)
in the formula: c. C L The specific heat capacity of oil-water liquid phase, J/(kg. DEG C); c. C w The specific heat capacity of water is adopted, the influence of temperature on the specific heat capacity of water is small, and the value is generally 4120; c. C o Is the specific heat capacity of crude oil, J/(kg. DEG C); and sigma is the mass water content.
Calculating the volume flow and volume water content of the oil-water liquid phase by the following formula:
q L ＝q w +q o
in the formula, G L The mass flow of the oil-water liquid phase is kg/s; q. q.s w Is the volume flow of water, m 3 S; sigma is the mass water content; q. q.s o Is the volume flow of crude oil, m 3 /s；ρ o Is crude oil density, kg/m 3 ；q L Is the volume flow of oil-water liquid phase, m 3 /s；
The water content is the volume water content.
The density of the oil-water liquid phase was calculated as follows:
in the formula: ρ is a unit of a gradient L Is the density of oil-water liquid phase, kg/m 3 The other symbols are as defined above.
Heat transfer coefficient alpha of oil flowing to inner wall of pipe 1 Related to the flow state of fluid in the pipeline, can pass through the lower partThe column calculation method determines:
in the case of a laminar flow of fluid,
in the formula of lambda y Is the heat conductivity coefficient of crude oil, W/(m.DEG C); upsilon is y As kinematic viscosity (dynamic viscosity to density ratio), m, of crude oil 2 /s；c y Is the specific heat capacity of crude oil, J/(kg. DEG C); beta is a y The volume expansion coefficient of crude oil is 1/DEG C, and is generally 0.00085; g is the acceleration of gravity, m/s 2 ；Re y Is Reynolds number; rho y Is crude oil density, kg/m 3 ；D 1 Is the inner diameter of the pipe, m;
the qualitative temperature of the pipeline is measured at DEG C; t is bi The qualitative temperature of the tube wall, DEG C; t is t 0 The temperature of the environment where the pipeline is located is DEG C, and other symbols have the same meanings as above. N is a radical of hydrogen y Parameters determined by using the physical properties of the crude oil at the oil flow-determining temperature, N bi The parameters are obtained by using the physical property parameters of the crude oil at the qualitative temperature of the pipe wall.
In the case of a turbulent flow of fluid,
when the flow regime is in the transition region,
the subscript "y" indicates that the parameters are taken from the qualitative temperature of the oil stream
The corner note "bi" indicates the qualitative temperature T of each parameter taken from the wall of the tube bi 。N y The parameter obtained from the physical property parameter of the crude oil at the oil flow qualitative temperature, N bi The parameter is obtained by using the physical property parameter of the crude oil at the qualitative temperature of the pipe wall.
Heat transfer coefficient alpha from outer wall of pipe to soil 2 Calculated as follows:
in the formula, λ t Is the soil thermal conductivity, W/(m.DEG C); h is t M is the center buried depth of the tube; d w The outer diameter of the pipe contacted with the soil, namely the outer diameter formed by an outer anti-corrosion layer or an insulating layer of the steel pipe, m.
The overall heat transfer coefficient K of the crude oil-pipeline-soil can be determined by the following equation:
in the formula, alpha 1 W/(m) is the heat transfer coefficient of oil flowing to the inner wall of the tube 2 ·℃)；α 2 Is the heat transfer coefficient from the outer wall of the tube to the soil, W/(m) 2 DEG C.); d is the calculated diameter, for a non-heat-insulation pipeline, the outer diameter of the steel pipe is taken, and for a heat-insulation pipeline, the average value m of the inner diameter and the outer diameter of the heat-insulation layer is taken; d i 、D (i+1) The inner diameter and the outer diameter of the steel pipe and the heat insulation layer are m; lambda [ alpha ] i The thermal conductivity corresponding to each layer is W/(m.cndot.), and the other symbols have the same meanings as those in the above formula.
The average pressure is determined by using the pipeline starting point pressure and the lowest allowable station entering pressure of the end point according to the following formula:
in the formula, p pj1 Is the gas phase average pressure, MPa; p is a radical of Q Is the starting pressure, MPa; p is a radical of Z The lowest permissible inbound pressure at the end point, MPa.
The absolute average pressure was determined as follows:
in the formula, p pj2 The other symbols in MPa are the same as those in the above formula.
The critical pressure and critical temperature of the gas phase were calculated as follows:
in the formula, p c Critical pressure of gas phase, MPa; t is a unit of c Critical temperature of gas phase, DEG C; n is the natural gas component number; y is i Is the mole fraction of the i component; p is a radical of ci And T ci Critical pressure (MPa) and critical temperature (K) for the pure i component.
The comparison pressure and the comparison temperature were found by the following formula:
in the formula, p r 、T r Comparing pressure and temperature; p is a radical of formula c 、p pj2 Critical pressure (MPa) and absolute average pressure (MPa) of the gas; t is c 、
The critical temperature (K) of the gas and the qualitative temperature (K) of the pipeline.
The gas phase average relative molecular mass was calculated as follows:
M g ＝∑M i y i
in the formula, y i Is the molar fraction of the component i; m is a group of i Relative molecular mass of component i.
The gas phase constant pressure molar heat capacity was calculated as follows:
in the formula, c p The gas phase constant pressure molar heat capacity is kJ/(kmol. K);
the qualitative temperature of the pipeline, K; m g Is the gas phase average relative molecular mass; p is a radical of pj1 Mean pressure, MPa.
The joule-thomson effect coefficient is related to the natural gas temperature, pressure, critical parameters and heat capacity, etc., and can be calculated according to the following formula:
f(p r ,T r )＝2.343T r -2.04 -0.071p r +0.0568
in the formula, D jt Is the Joule-Thomson effect coefficient, K/MPa; c. C p The constant-pressure molar heat capacity is kJ/(kmol. K); p is a radical of c Critical pressure, MPa; t is a unit of c Apparent critical temperature, K; p is a radical of r And T r Comparative pressure and comparative temperature.
The gas phase mass to specific heat capacity was calculated as follows:
in the formula: c. C g The gas phase mass specific heat capacity is J/(kg DEG C); c. C p The constant-pressure molar heat capacity is kJ/(kmol. K); m g Is the gas phase average relative molecular mass.
Determining the mass fraction of the gas phase according to the following formula:
G g ＝ρ g q g
in the formula: x is the mass fraction of the gas phase; g g Gas phase mass flow, kg/s; rho g Is gas phase density, kg/m 3 ；q g Is the gas phase volume flow rate, m 3 /s；G L Is the mass flow of oil-water liquid phase, kg/s.
The specific heat capacity of the oil-gas-water mixture can be calculated according to the following formula:
c m ＝c g x+c L (1-x)
in the formula: c. C m The specific heat capacity of the oil-gas-water mixture, J/(kg DEG C); x is gas phase mass fraction; c. C g The gas phase mass specific heat capacity is J/(kg DEG C); c. C L The specific heat capacity of oil-water-liquid phase is J/(kg DEG C).
The mass flow of the oil-gas-water mixture is as follows:
G m ＝G L +G g
in the formula, G m The mass flow of the oil-gas-water mixture is kg/s; g L The mass flow of the oil-water liquid phase is kg/s; g g The gas phase mass flow is kg/s.
Suppose L T If the initial value of the temperature difference is 0.1, establishing an axial temperature drop model of the oil-gas-water mixed transportation pipeline as follows:
in the formula, L T The length m from the starting point of the pipeline to any point along the pipeline; t is t L Is the starting point L of the distance of the pipeline T Oil flow temperature at rice, deg.C; t is t 0 The temperature of the environment outside the pipe (the temperature of the buried pipeline in the depth of the center of the pipe) is measured at DEG C; t is R Taking the starting temperature of the pipeline, wherein the temperature is DEG C, and the e is a natural logarithm base number, and taking the temperature to be 2.718; k is the total heat transfer coefficient, W/(m) 2 ·℃)；D jt Is the Joule-Thomson effect coefficient, K/MPa; c. C g Gas phase mass specific heat capacity, J/(kg. DEG C); d is the calculated diameter, for a non-heat-insulation pipeline, the outer diameter of the steel pipe is taken, and for a heat-insulation pipeline, the average value m of the inner diameter and the outer diameter of the heat-insulation layer is taken; p is a radical of Q Is the starting pressure, MPa; p is a radical of formula Z The lowest allowable station entering pressure of the terminal point, MPa, and other symbols have the same meanings as the above formula.
Substituting the relevant parameters into the above formula to obtain the tube length L T End point temperature t of the pipeline L And judging whether the relative error between the temperature value and the lowest allowable temperature of the pipeline end point is less than 5%. If less than, then L at this time T Namely the gathering and transmission radius under the thermal constraint; if not, an iterative calculation method can be adopted, and the step size of 0.1 is used for L T Are accumulated to respectively calculate different L T T at L Until the relative error between the temperature value and the lowest allowable temperature of the end point of the pipeline is less than 5%, then L at the moment T Namely the gathering and transporting radius under the thermal constraint.
The flow chart of the calculation of the gathering radius under the thermodynamic constraint condition is shown in fig. 5.
Step three: taking an oil-gas-water mixed transportation pipeline as a research object, and calculating the volume flow of a gas-liquid mixture according to the following formula:
q m ＝q L +q g
in the formula, q m Volume flow rate of gas-liquid mixture, m 3 /s；q L Volume flow of oil-water liquid phase, m 3 /s；q g Volume flow in the gas phase, m 3 /s。
The average flow rate of the gas-liquid mixture can be calculated as follows:
in the formula, v m Is the average flow velocity of the gas-liquid mixture, m/s; q. q.s m Volume flow rate of gas-liquid mixture, m 3 /s；D 1 Is the inner diameter of the pipe, m.
And substituting the qualitative temperature of the pipeline in the step two into the model of the physical property parameter in the step one to obtain the specific physical property parameter of the crude oil at the qualitative temperature, wherein the influence of the temperature on the physical property parameter of the water is small, so that the change of the physical property parameter of the water caused by the temperature is ignored in the calculation process of the gathering and transportation radius.
The kinematic viscosity of the gas-liquid mixture can be determined by the following calculation method:
R L ＝q L /q m
μ m ＝μ L R L +μ g (1-R L )
in the formula: mu.s L 、μ g The dynamic viscosity of oil-water liquid phase and gas phase, Pa.s;
the water content is the volume water content; mu.s o Is the dynamic viscosity of the crude oil, Pa.s; mu.s w The dynamic viscosity of water, Pa.s, generally takes 0.001; r L Is a bodyLiquid retention rate; q. q.s L Volume flow of oil-water liquid phase, m 3 /s；q m Volume flow rate of gas-liquid mixture, m 3 /s。
Determination of the liquid holdup H by means of a trial algorithm L The method comprises the following specific steps:
first, assume a liquid holdup H L Calculating the average density of the gas-liquid mixture:
in the formula: ρ is a unit of a gradient m Is the average density of the gas-liquid mixture; rho L 、ρ g The density of oil-water liquid phase and gas phase is kg/m 3 ；
R L Is the volume liquid content; h L The cross-sectional liquid content (liquid holdup), i.e. the liquid content when the gas-liquid phase slips, can be determined according to R L And Re m (mixed transport Reynolds number) is determined by calculation.
Calculating the mixed transmission Reynolds number according to the following formula:
in the formula, Re m The Reynolds number of mixed transmission is dimensionless; d 1 The meaning of m, the inner diameter of the pipe, and other symbols are the same as described above.
Secondly, according to different mixed transportation Reynolds numbers Re m Calculating H by the following relation L ：
β＝lgR L +3
In the formula, R L Is the volume liquid content;
when Re m When R is 1, R L And H L The mathematical expression of the relationship is:
lgH L ＝1.98975289+0.4192759β-0.3517347β 2 +0.0627002β 3 +0.00611271β 4 -0.001097β 5 -2
when Re m When R is 100, R L And H L The mathematical expression of the relationship is:
lgH L ＝1.53077259+0.4562775β-0.3097665β 2 +0.0718006β 3 +0.01101236β 4 -0.003875β 5 -2
when Re m When R is 500, R L And H L The mathematical expression of the relationship is:
lgH L ＝1.15927438+0.5157858β-0.0104859β 2 -0.1975919β 3 +0.10033697β 4 -0.01400916β 5 -2
when Re m When it is 1000, R L And H L The mathematical expression of the relationship is:
lgH L ＝0.86228039+0.7941742β-0.0414958β 2 -0.3076484β 3 +0.16093553β 4 -0.0230459β 5 -2
when Re m When equal to 2500, R L And H L The mathematical expression of the relationship is:
lgH L ＝0.61121528+0.8219817β+0.2450638β 2 -0.591696β 3 +0.26550666β 4 -0.03627456β 5 -2
when Re m When R is 5000, R L And H L The mathematical expression of the relationship is:
lgH L ＝0.37037426+1.1458724β-0.1024697β 2 -0.3317119β 3 +0.17193205β 4 -0.02410223β 5 -2
when Re m When 10000, R L And H L The mathematical expression of the relationship is:
lgH L ＝0.21324017+0.9846183β+0.4538199β 2 -0.7934965β 3 +0.32817872β 4 -0.04284162β 5 -2
when Re m When 25000, R L And H L The mathematical expression of the relationship is:
lgH L ＝-0.040313231+0.94664475β+0.7145845β 2 -0.9824665β 3 +0.3845391β 4 -0.048779381β 5 -2
when Re m R is 50000 L And H L The mathematical expression of the relationship is:
lgH L ＝-0.22287976+0.8475579β+0.7621021β 2 -0.9112905β 3 +0.3433659β 4 -0.042773693β 5 -2
when Re m When 100000, R L And H L The mathematical expression of the relationship is:
lgH L ＝-0.3672887+0.437131β+1.266505β 2 -1.157105β 3 +0.4060284β 4 -0.04932038β 5 -2
when Re m When 200000, R L And H L The mathematical expression of the relationship is:
lgH L ＝-1.272218+2.227224β-0.86396β 2 +0.092496β 3 +0.067676β 4 -0.0149087β 5 -2
reynolds number Re of oil-gas-water mixed transportation pipeline m The case of exactly equal Reynolds number is rare if it is at the above two Reynolds numbers Re m1 And Re m2 (Re m1 <Re m2 ) In between, the liquid holdup is determined by interpolation, and H can be calculated by the following formula L ：
In the formula, H L1 When Reynolds number equals Re m1 The liquid holdup H determined by the time calculation L2 When Reynolds number equals Re m2 Calculating the obtained liquid holding rate; [ Re ] m1 ,Re m2 ]Satisfies Re in the range of all Reynolds numbers m1 <Re m <Re m2 The minimum interval for this condition.
Finally, the recalculated H is judged L Whether the relative error between the value and its assumed value is less than 5%, for example, not less than the re-assumed H L And repeating the above steps until H L Of assumed and calculated valuesUntil the relative error is less than 5%.
The mixed transportation resistance coefficient can be calculated according to the following formula:
S＝1.281-0.478(-lnR L )+0.444(-lnR L ) 2 -0.094(-lnR L ) 3 +0.00843(-lnR L ) 4
wherein phi is the ratio of the mixed transport resistance coefficient to the oil-water liquid phase resistance coefficient, and can be determined from the liquid content R without slippage L And (4) calculating and determining that other symbols have the same meaning as in the formula.
Then an oil-gas-water mixed transportation pipeline pressure drop model can be established as follows:
in the formula, delta p is the pressure drop, MPa, of the oil-gas-water mixed transportation pipeline and can be obtained by subtracting the pressure allowed to enter the station from the pressure at the starting point of the oil-gas-water mixed transportation pipeline and the pressure at the finishing point of the oil-gas-water mixed transportation pipeline; lambda [ alpha ] m The mixed transportation resistance coefficient; rho m Is the average density of gas-liquid mixture, kg/m 3 ；v m The average flow velocity of the gas-liquid mixture is m/s; l is the length of the pipeline, km; d 1 Is the inner diameter of the pipe, m.
The gathering radius under hydraulic restraint is thus obtained:
in the formula, L P The meaning of the other symbols, m, is the gathering and transportation radius under the hydraulic constraint.
The flow chart of the calculation of the gathering radius under the thermodynamic constraint condition is shown in fig. 6.
Step four: comprehensively considering the thermodynamic radius of each pipeline in a production block, establishing a thermodynamic constraint array of the block aiming at the oil field production block, determining the thermodynamic constraint radius of the block, establishing a hydraulic constraint array according to the hydraulic radius in the same way, determining the hydraulic constraint radius of the block, and finally obtaining the normal-temperature gathering and transporting radius of the production block by combining the thermodynamic constraint radius and the hydraulic constraint radius, wherein the specific calculation formula of the normal-temperature gathering and transporting radius is as follows:
L T ＝min(L T1 ,L T2 ,L T3 ,…,L Tk )
L P ＝min(L P1 ,L P2 ,L P3 ,…,L Pk )
L＝min(L T ,L P )
in the formula, L T Is the gathering and transporting radius, m, of the block under the thermal constraint condition; l is T1 ,L T2 ,L T3 ,…,L Tk Respectively numbering 1-k pipelines, and collecting and transmitting radius m under thermal constraint; l is P The normal-temperature gathering and transportation radius m of the block under the hydraulic constraint condition; l is a radical of an alcohol P1 ,L P2 ,L P3 ,…,L Pn The collection and transportation radiuses m under the hydraulic constraint of pipelines numbered 1-k respectively; l is the normal temperature gathering and transporting radius of the block, m.
In order to make the above contents of the present invention more obvious and understandable, the following description will be made in detail by taking the gathering and transporting pipeline of a certain block in the oil field of Jiangsu province as a research object and calculating the normal temperature gathering and transporting radius of the block:
the length of the pipeline, the liquid production amount (oil-water liquid phase mass flow), the gas production rate, the starting point temperature and the pressure are shown in table 1. The outer diameter is 108mm, the wall thickness is 4.5mm, the heat conductivity coefficient of the steel pipe is 49.8W/(m.DEG C), the burial depth of the upper surface of the pipeline is 0.8m, the environmental temperature of the pipeline is 1.9 ℃, the heat conductivity coefficient of the soil is 1.5W/(m.DEG C), and the density of the oil product at 20 ℃ is 882.6kg/m 3 The viscosity is 59.8 pas, the heat conductivity coefficient is 0.153W/(m.DEG C), the specific heat capacity is 3032J/(kg.DEG C), the pipeline heat-insulating material is rock wool, the thickness is 0.01m, the heat conductivity coefficient is 0.039W/m.DEG C, the mass water content is 09, gas density of 0.72kg/m 3 Viscosity of 0.0001 pas, gas phase composition and critical parameters are shown in table 2, the endpoint minimum allowed entry pressure is 0.4MPa, and the minimum allowed entry temperature is 27 ℃.
TABLE 1 different pipeline running parameters
TABLE 2 Natural gas composition and Critical parameters thereof
The normal-temperature gathering and transporting radius of the pipeline is calculated, and the specific method comprises the following steps:
step one, testing the density, viscosity and specific heat of crude oil at different temperatures by using an indoor testing instrument as shown in table 3.
TABLE 3 crude oil Change physical Properties parameters
The measured data are subjected to linear or nonlinear fitting to obtain a physical property parameter mathematical model of the crude oil as follows:
crude oil density:
ρ o ＝882.6-0.664(T-20)
in the formula, ρ o Is the density of oil product, kg/m 3 (ii) a T is the temperature of the oil product, DEG C;
viscosity of crude oil:
when 33.2< T <70 ℃, the oil viscosity is:
when T is more than 20 and less than or equal to 33.2 ℃, the viscosity of the oil product is as follows:
in the formula, mu o Is the dynamic viscosity of the oil, mPa.s; t is the temperature of the oil product, DEG C;
specific heat capacity:
when T is more than 0 and less than or equal to 33 ℃, the specific heat capacity of the oil product is as follows:
c o ＝-0.00006T 2 +0.0318T+2.4237
when T is more than 33 and less than or equal to 54 ℃, the specific heat capacity of the oil product is as follows:
c o ＝0.00286T 2 -0.2887T+9.9903
when 54< T <63 ℃, the specific heat capacity of the oil is as follows:
c o ＝-0.0001T 2 +0.0143T+2.0898
in the formula, c o The specific heat capacity of the oil product, j/(g ℃); t is the temperature of the oil product, DEG C.
Coefficient of thermal conductivity:
λ o ＝0.1546(1-0.00054T)
the crude oil variation property parameter curves are shown in figures 1-4.
Determining the qualitative temperature of the medium in the pipeline by using the starting point temperature and the end point allowable temperature of the pipeline to obtain relevant parameters of the oil-gas-water mixed transportation pipeline, wherein the relevant parameters are as shown in a table:
TABLE 4 physical Properties of crude oil at pipeline operating temperature
TABLE 5 oil-water phase related parameters
TABLE 6 correlation of heat transfer coefficients
TABLE 7 mean pressure of the pipeline and critical parameters of the gas phase
TABLE 8 gas phase related parameters
TABLE 9 parameters related to oil, gas and water mixtures
Substituting the parameters into a temperature drop model, combining the starting point temperature and the lowest allowable temperature of the pipeline end point, and calculating the gathering and transporting radius of each gathering and transporting pipeline of the block under the thermal constraint condition by adopting an iterative calculation method as follows:
L T1 ＝4336.5m，L T2 ＝4727.8m，L T3 ＝3315.3m，L T4 ＝4075.5m
and step three, determining the specific physical property parameters of the medium in the pipeline according to the physical property parameters of the crude oil in the step two, and obtaining the related parameters as shown in the table.
TABLE 10 parameters relating to oil, gas and water mixtures
TABLE 11 parameters relating to the medium in the tubes
Substituting the above parameters into the following formula:
in the formula, delta p is the pressure drop of the oil-gas-water mixed transportation pipeline, and is MPa; lambda m The mixed transportation resistance coefficient; ρ is a unit of a gradient m Is the average density of gas-liquid mixture, kg/m 3 ；v m The average flow velocity of the gas-liquid mixture is m/s; d 1 Is the inner diameter of the pipe, m. The normal-temperature gathering and transporting radius of each oil collecting pipeline in the block under the hydraulic constraint condition can be obtained as follows:
L P1 ＝1841.2m，L P2 ＝2024.2m，L P3 ＝2089.9m，L P4 ＝1735m
step four, calculating the normal-temperature gathering and transporting radius according to the following method:
the gathering and transporting radius of the block under the thermal constraint condition is as follows:
L T ＝min(L T1 ,L T2 ,L T3 ,…,L Tk )＝min(4336.5,4727.8,3315.3,4075.5)＝3315.3m
the gathering and transporting radius of the block under the hydraulic constraint condition is as follows:
L P ＝min(L P1 ,L P2 ,L P3 ,…,L Pk )＝min(1841.2,2024.2,2089.9,1735)＝1735m
and determining the normal-temperature gathering and transporting radius of the pipeline in the block as follows by combining the hydraulic constraint condition and the thermal constraint condition of each pipeline:
L＝min(L T ,L P )＝min(3315.3,1735)＝1735m。
the method can determine the maximum safe distance for the mixed fluid in the pipeline to flow under the conditions of meeting the lowest station entering temperature and pressure when the pipeline is not heated.
The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (1)
1. A method for calculating the normal-temperature gathering and transporting radius of an oil-gas-water mixed transportation pipeline is characterized by comprising the following steps:
step 1): aiming at an oil field production block, various physical parameters of crude oil at different temperatures are measured, a physical parameter model of the crude oil is established by a linear or nonlinear regression method, and a crude oil density-temperature relation calculation formula is as follows: rho o ＝ρ 20 -ξ(T-20)
ρ o 、ρ 20 Crude oil densities at T ℃ and 20 ℃ respectively; xi is temperature coefficient, 1.825-0.001315 rho 20 ；
The formula for performing nonlinear regression on the viscosity-temperature curve of the crude oil is as follows:
crude oil exhibits properties of newtonian fluids:
crude oil is a non-newtonian fluid:
μ o is the dynamic viscosity of crude oil at T ℃; t is the crude oil temperature; a. the 1 、A 2 、B 1 、B 2 、C 1 、C 2 Is a coefficient;
dividing a specific heat capacity-temperature curve into three regions according to the wax precipitation point temperature and the maximum specific heat capacity temperature to perform nonlinear regression;
when the oil temperature is higher than the wax precipitation point temperature: c. C o ＝H 1 T 2 +E 1 T+F 1 ；
When the oil temperature is less than the wax precipitation point temperature and greater than the maximum specific heat capacity temperature: c. C o ＝H 2 T 2 +E 2 T+F 2 ；
When the oil temperature is less than the maximum specific heat capacity temperature: c. C o ＝H 3 T 2 +E 3 T+F 3 ；
c o Crude oil specific heat capacity at T; t is the crude oil temperature; h 1 、H 2 、H 3 、E 1 、E 2 、E 3 、F 1 、F 2 、F 3 Is a coefficient;
the heat conductivity of the crude oil is calculated according to the following formula:
λ o the heat conductivity coefficient of the oil product when the oil temperature is T; t is the oil temperature; ρ is a unit of a gradient 15 The density of the oil product at 15 ℃;
step 2): the method comprises the following steps of taking an oil-gas-water mixed transportation pipeline as a research object, determining the qualitative temperature of a fluid in the transportation process by utilizing the lowest allowable station-entering temperature of the starting point temperature and the terminal point of the pipeline, obtaining related physical property parameters of crude oil and an oil-water liquid phase at the temperature, and further obtaining the heat transfer coefficient from the fluid to the inner wall of a pipe, the heat transfer coefficient from the outer wall of the pipe to soil and the total heat transfer coefficient from the crude oil, the pipeline and the soil; calculating absolute average pressure and gas phase critical parameters of the pipeline at the same time, obtaining a Joule-Thomson effect coefficient on the basis, determining the mass specific heat capacity of the oil-gas-water mixture through the gas phase mass specific heat capacity and the gas phase mass fraction, establishing an oil-gas-water mixed transportation pipeline temperature drop mathematical model by combining the mass flow of the oil-gas-water mixture, and obtaining the normal temperature gathering and transportation thermal radius through an iterative calculation method; the qualitative temperature of the pipeline is as follows:
c L ＝c w σ+c o (1-σ)
c L the specific heat capacity of oil-water liquid phase; c. C w Is the specific heat capacity of water; c. C o Is the specific heat capacity of the crude oil; sigma is the mass water content;
q L ＝q w +q o
G L the mass flow of the oil-water liquid phase; q. q.s w Is the water volume flow; sigma is the mass water content; q. q.s o Is the crude oil volumetric flow rate; rho o Is the crude oil density; q. q.s L Is the oil-water liquid phase volume flow;
the water content is the volume water content;
heat transfer coefficient alpha of oil flowing to inner wall of tube 1 ，
In the case of a laminar flow of fluid,
λ y the heat conductivity coefficient of crude oil; upsilon is y Is the kinematic viscosity of the crude oil; c. C y The specific heat capacity of the crude oil; beta is a y The volume expansion coefficient of the crude oil; g is the acceleration of gravity; re y Is Reynolds number; rho y Is the crude oil density; d 1 Is the inner diameter of the pipeline;
determining the temperature of the pipeline; t is bi Determining the temperature of the tube wall; t is t 0 The ambient temperature of the pipeline;
in the case of a turbulent flow of the fluid,
when the flow regime is in the transition region,
heat transfer coefficient alpha from outer wall of pipe to soil 2 Calculated as follows:
λ t is the soil thermal conductivity; h is t Burying the center of the tube deeply; d w The outer diameter of the pipe which is contacted with the soil, namely the outer diameter formed by an outer anti-corrosion layer or an insulating layer of the steel pipe;
α 1 the heat transfer coefficient of oil flowing to the inner wall of the tube; alpha is alpha 2 The heat transfer coefficient from the outer wall of the tube to the soil; d is the calculated diameter; d i 、D (i+1) The inner diameter and the outer diameter of the steel pipe and the heat-insulating layer; lambda [ alpha ] i Is the coefficient of thermal conductivity; k is the total heat transfer coefficient of crude oil, pipeline and soil;
the average pressure is determined by using the pipeline starting point pressure and the lowest allowable station entering pressure of the end point according to the following formula:
p pj1 is the gas phase average pressure; p is a radical of Q Is the starting pressure; p is a radical of formula Z The lowest allowable inbound pressure for the terminal;
in the formula, p pj2 Is the gas phase mean absolute pressure;
the critical pressure and critical temperature of the gas phase were calculated as follows:
in the formula, p c Critical pressure in the gas phase; t is c Critical temperature in the gas phase; n is the natural gas component number; y is i Is the molar fraction of the component i; p is a radical of ci And T ci Critical pressure and critical temperature for the pure i component;
the comparison pressure and the comparison temperature were found by the following formula:
in the formula, p r 、T r Comparing pressure and temperature; p is a radical of c 、p pj2 Critical pressure and absolute mean pressure of the gas; t is c 、
The critical temperature of the gas and the qualitative temperature of the pipeline are adopted;
the gas phase average relative molecular mass was calculated as follows:
M g ＝∑M i y i
in the formula, y i Is the mole fraction of the i component; m i Is the relative molecular mass of the i component;
the gas phase constant pressure molar heat capacity was calculated as follows:
in the formula, c p The gas phase constant pressure molar heat capacity;
determining the temperature of the pipeline; m g Is the gas phase average relative molecular mass; p is a radical of pj1 Is the average pressure;
the joule-thomson effect coefficient is calculated as follows:
f(p r ,T r )＝2.343T r -2.04 -0.071p r +0.0568
in the formula, D jt Is the joule-thomson effect coefficient; c. C p Is a constant pressure molar heat capacity; p is a radical of formula c A critical pressure; t is a unit of c A critical temperature; p is a radical of r And T r Comparing pressure and temperature;
gas phase mass specific heat capacity:
c g the gas phase mass specific heat capacity; c. C p Is a constant pressure molar heat capacity; m g Is the gas phase average relative molecular mass;
G g ＝ρ g q g
x is the mass fraction of the gas phase; g g Is the gas phase mass flow rate; rho g Is the gas phase density; q. q.s g Is the gas phase volume flow; g L The mass flow of the oil-water liquid phase;
c m ＝c g x+c L (1-x)
c m the specific heat capacity of the oil-gas-water mixture; x is gas phase mass fraction; c. C g Is gas phase mass specific heat capacity; c. C L The specific heat capacity of oil-water liquid phase;
G m ＝G L +G g
G m the mass flow of the oil-gas-water mixture; g L The mass flow of the oil-water liquid phase; g g Is gas phase mass flow rate;
suppose L T The initial value of the temperature difference is 0.1, and an axial temperature drop model of the oil-gas-water mixed transportation pipeline is established as follows:
L T the length from the starting point of the pipeline to any point along the line; t is t L Is the starting point L of the distance of the pipeline T Oil flow temperature at rice; t is t 0 The ambient temperature outside the tube; t is a unit of R Is the starting temperature of the pipeline, and e is the natural logarithm base number; k is the total heat transfer coefficient; d jt Is the joule-thomson effect coefficient; c. C g Is gas phase mass specific heat capacity; d is the calculated diameter; p is a radical of formula Q Is the starting pressure; p is a radical of Z The lowest allowable inbound pressure for the terminal;
obtaining a tube length L T End temperature t of the pipeline L Judging whether the relative error between the temperature value and the lowest allowable temperature of the pipeline end point is less than 5%; if less than 5%, L at this time T Namely the gathering and transmission radius under the thermal constraint; if not less than 5%, adopting iterative calculation method, and using 0.1 as step length to make L T Are accumulated to respectively calculate different L T T is L Until the relative error between the temperature value and the lowest allowable temperature of the end point of the pipeline is less than 5%, then L at the moment T Namely the gathering and transmission radius under the thermal constraint;
step 3): determining the average flow velocity of a gas-liquid mixture according to the volume flow of an oil-liquid phase and a gas phase in a pipeline, obtaining the dynamic viscosity of the gas-liquid mixture by using the physical parameters of crude oil, calculating the density of the gas-liquid mixture and the Reynolds number and the liquid holdup in a mixed transportation pipeline by adopting a circulation iteration method, further determining a mixed transportation resistance coefficient, establishing an oil-gas-water mixed transportation pipeline pressure drop model, determining the maximum pressure drop of the pipeline according to the starting point pressure and the lowest allowable station-entering pressure of a terminal point of the pipeline, and substituting the maximum pressure drop of the pipeline into the model to obtain the normal-temperature hydraulic radius of the gathering and transportation;
q m ＝q L +q g
q m is the volume flow of the gas-liquid mixture; q. q.s L The volume flow of the oil-water liquid phase; q. q.s g A volume flow in the gas phase;
the average flow rate of the gas-liquid mixture can be calculated as follows:
v m is the average flow rate of the gas-liquid mixture; q. q.s m Is the volume flow of the gas-liquid mixture; d 1 Is the inner diameter of the pipeline;
R L ＝q L /q m
μ m ＝μ L R L +μ g (1-R L )
μ L 、μ g the dynamic viscosity of oil-water liquid phase and gas phase;
the water content is the volume water content; mu.s o Is the kinematic viscosity of the crude oil; mu.s w Is the kinetic viscosity of water; r L Is the volume liquid content; q. q.s L The volume flow of oil-water liquid phase; q. q.s m Is the volume flow of the gas-liquid mixture;
determination of the liquid holdup H by means of a trial algorithm L The method comprises the following steps:
first, suppose the liquid holdup H L Calculating the average density of the gas-liquid mixture:
ρ m is the average density of the gas-liquid mixture; rho L 、ρ g The density of oil-water liquid phase and gas phase; r L Is the volume liquid content; h L Is the cross-sectional liquid content;
calculating mixed transport Reynolds number
Re m Is the mixed transportation Reynolds number; d 1 Is the inner diameter of the pipeline;
then, according to different mixed transportation Reynolds numbers Re m Calculating H by the following relation L ：β＝lgR L +3，
R L Is the volume liquid content;
when Re m When R is 1, R L And H L The mathematical expression of the relationship is:
lg H L ＝1.98975289+0.4192759β-0.3517347β 2 +0.0627002β 3 +0.00611271β 4 -0.001097β 5 -2
when Re m When R is 100, R L And H L The mathematical expression of the relationship is:
lg H L ＝1.53077259+0.4562775β-0.3097665β 2 +0.0718006β 3 +0.01101236β 4 -0.003875β 5 -2
when Re m When R is 500, R L And H L The mathematical expression of the relationship is:
lg H L ＝1.15927438+0.5157858β-0.0104859β 2 -0.1975919β 3 +0.10033697β 4 -0.01400916β 5 -2
when Re m When R is 1000 L And H L The mathematical expression of the relationship is:
lg H L ＝0.86228039+0.7941742β-0.0414958β 2 -0.3076484β 3 +0.16093553β 4 -0.0230459β 5 -2
when Re m When R is 2500, R L And H L The mathematical expression of the relationship is:
lg H L ＝0.61121528+0.8219817β+0.2450638β 2 -0.591696β 3 +0.26550666β 4 -0.03627456β 5 -2
when Re m When 5000, R L And H L The mathematical expression of the relationship is:
lg H L ＝0.37037426+1.1458724β-0.1024697β 2 -0.3317119β 3 +0.17193205β 4 -0.02410223β 5 -2
when Re m When 10000, R L And H L The mathematical expression of the relationship is:
lg H L ＝0.21324017+0.9846183β+0.4538199β 2 -0.7934965β 3 +0.32817872β 4 -0.04284162β 5 -2
when Re m At 25000, R L And H L The mathematical expression of the relationship is:
lg H L ＝-0.040313231+0.94664475β+0.7145845β 2 -0.9824665β 3 +0.3845391β 4 -0.048779381β 5 -2
when Re m When R is 50000, R L And H L The mathematical expression of the relationship is:
lg H L ＝-0.22287976+0.8475579β+0.7621021β 2 -0.9112905β 3 +0.3433659β 4 -0.042773693β 5 -2
when Re m When 100000, R L And H L The mathematical expression of the relationship is:
lg H L ＝-0.3672887+0.437131β+1.266505β 2 -1.157105β 3 +0.4060284β 4 -0.04932038β 5 -2
when Re m When 200000, R L And H L The mathematical expression of the relationship is:
lg H L ＝-1.272218+2.227224β-0.86396β 2 +0.092496β 3 +0.067676β 4 -0.0149087β 5 -2
reynolds number Re of oil-gas-water mixed conveying pipeline m Is not any of the Reynolds numbers mentioned above
In the case of numerical value, two Reynolds numbers Re are selected from the above Reynolds numbers m1 And Re m2 The liquid holdup is determined by interpolation, and H is calculated as follows L ：
In the formula, H L1 When Reynolds number equals Re m1 The liquid holdup H determined by the time calculation L2 When Reynolds number equals Re m2 Calculating the obtained liquid holding rate; [ Re ] m1 ,Re m2 ]Satisfies Re in the range of all Reynolds numbers m1 <Re m <Re m2 The minimum interval of this condition;
finally, the recalculated H is judged L Whether the relative error between the value and its assumed value is less than 5%, e.g. not less than the re-assumed H L And repeating the above steps until H L Assuming that the relative error between the value and the calculated value is less than 5%;
the mixed transportation resistance coefficient calculation formula is as follows:
S＝1.281-0.478(-ln R L )+0.444(-ln R L ) 2 -0.094(-ln R L ) 3 +0.00843(-ln R L ) 4
phi is the ratio of the mixed transportation resistance coefficient to the oil-water liquid phase resistance coefficient,
the pressure drop model of the oil-gas-water mixed transportation pipeline is established as follows:
delta p is the pressure drop of the oil-gas-water mixed transportation pipeline; lambda [ alpha ] m The mixed transportation resistance coefficient; ρ is a unit of a gradient m Is the average density of the gas-liquid mixture; v. of m Is the average flow velocity of the gas-liquid mixture; l is the length of the pipeline; d 1 Is the inner diameter of the pipeline;
the gathering and transportation radius under hydraulic constraint is as follows:
step 4): establishing a thermodynamic constraint array of a production block, determining the thermodynamic constraint radius of the block, establishing a hydraulic constraint array according to the hydraulic radius, determining the hydraulic constraint radius of the block, obtaining the normal-temperature gathering and transporting radius of the production block by combining thermodynamic constraint and hydraulic constraint conditions,
L T ＝min(L T1 ,L T2 ,L T3 ,…,L Tk )
L P ＝min(L P1 ,L P2 ,L P3 ,…,L Pk )
L＝min(L T ,L P )
in the formula, L T The gathering and transmitting radius of the block under the thermal constraint condition; l is a radical of an alcohol T1 ,L T2 ,L T3 ,…,L Tk Respectively numbering 1-k pipelines, and collecting and transmitting radiuses under thermal constraint; l is a radical of an alcohol P The normal temperature gathering and transporting radius of the block under the hydraulic constraint condition; l is P1 ,L P2 ,L P3 ,…,L Pn The hydraulic constraint lower gathering and conveying radiuses of pipelines numbered 1-k respectively; l is the normal temperature gathering and transporting radius of the block.
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