CN102778418A - Crude oil pipeline initial condensation probability quantitative evaluation method - Google Patents

Abstract

Relating to the technical field of pipeline systems, the invention relates to a crude oil pipeline initial condensation probability quantitative evaluation method. According to the method, after obtaining a pipeline initial condensation probability calculation result, the initial condensation probability of a pipeline can be obtained, and evaluation about flow security related risks is carried out. When the initial condensation probability is less than 0.001 and a current minimum secure delivery amount is greater than 1.1 times of a critical delivery amount, the pipeline can be considered as secure in initial condensation evaluation; when the initial condensation probability is greater than 0.001 and the current minimum secure delivery amount is smaller than 1.1 times of the critical delivery amount, the pipeline can be considered as unsecure; and if the initial condensation probability is others, the pipeline can be considered to have risks. For the pipelines considered to be unsecure or have risks, evaluation needs to be carried out again under a virtual working situation, and on the basis, on-site production and operation suggestions can be provided. The invention is precise and reliable.

Description

Crude oil pipeline initial set probability method for quantitatively evaluating

Technical field

The present invention is a kind of crude oil pipeline initial set probability method for quantitatively evaluating.Relate to the piping system technical field.

Background technology

Flow Influence on security factor more (like buried depth of pipeline, the soil moisture, crude oil property rheological parameter, throughput rate, out-station temperature etc.) and have uncertainty of waxy crude oil; Owing to reasons such as the variation of the adjustment of the defeated technological parameter of pipe, pipeline environment condition and the variations of oil product through pipelines rheological characteristics; Pipeline transportation often is in unstable working state, makes the mobile safe condition of pipeline also constantly change.If the working point of waxy crude oil run duration gets into the unstable operation district; The situation that throughput rate reduces, frictional resistance increases on the contrary appears; If do not take safeguard timely; The initial set accident of pipeline very likely taking place, and can cause pipeline to develop into the final ultimate limit state of coagulating pipe by the adaptability ultimate limit state of initial set, produces massive losses.But the flow evaluation of security of waxy crude oil so far still mainly is that the operations staff judges according to the experience directly perceived of oneself and analyzes; To also be that single factor or single aspect in numerous influence factors and the aspect studied; Thereby the result who obtains is comprehensive inadequately, system; And be result qualitatively, be difficult to ensure the security of pipeline operation.

" oil gas accumulating " the 26th the 5th phase of volume " burying the mobile Research on Safety Assessment of ground wax-containing oil pipe " discloses a kind of crude oil pipeline initial set probability method for quantitatively evaluating.It comprises that calculating parameter extracts and analyzes; The DATA DISTRIBUTION property probability statistics of influence factor; Confirm critical throughput rate calculating; Uncertain critical throughput rate is calculated; Statistics unstable operation district; Draw pipeline initial set probability calculation result.But also the grab sample step of confirming to reach parameter of unexposed evaluation number of times also discloses the numerical value of initial set probability and the concrete corresponding relation of security.So it is imperfection also.

Summary of the invention

The objective of the invention is to invent a kind of accurate, reliable crude oil pipeline initial set probability method for quantitatively evaluating.

For given hot oil pipeline; The curve that total frictional resistance of pipeline changes with throughput rate generally can be divided into three different zones and (see Fig. 1; Curve among the figure is classified with the susceptibility property of the viscosity temperature variation of waxy crude oil) be low discharge district (I district): along with reducing of throughput rate, frictional resistance sharply reduces; Intermediate flow district (II district): along with reducing of throughput rate, frictional resistance increases on the contrary; Big flow district (III district): along with reducing of throughput rate, frictional resistance also reduces gradually.

Wherein the II district is commonly referred to the unstable operation district, and the III district is commonly referred to stable work area.The hot oil pipeline working point is in the II district time, and Chang Keneng is prone to cause pipeline to arrhea, coagulate accidents such as pipe because the influence of some extraneous factor the situation that frictional resistance sharply increases on the contrary occurs when throughput rate is reduced.Throughput rate when the pipeline working point gets into the II district by the III district is called critical throughput rate; For guaranteeing the safe operation of pipeline; The working point of hot oil pipeline operation should remain in the III district; Throughput rate when being the operation of pipeline normal and stable should avoid pipeline to be in adaptability flow limit state greater than critical throughput rate.The critical throughput rate of wax-containing oil pipe is all relevant with its flow characteristics, waterpower and thermal condition etc.

This crude oil pipeline initial set probability method for quantitatively evaluating is with the same (see figure 1) of prior art, and its flow process comprises:

The form robotization of calculating parameter is extracted and is analyzed;

The DATA DISTRIBUTION property probability statistics of influence factor;

The critical throughput rate of determinacy is calculated;

Estimate the setting of number of times and the grab sample of parameter;

Uncertain critical throughput rate is calculated;

Statistics gets into the calculation times in unstable operation district;

Draw pipeline initial set probability calculation result.

Because actual production pipeline throughput rate in service, out-station temperature, steady-state operation overall heat transfer coefficient, buried depth of pipeline, buried depth of pipeline place ground temperature, soil thermal conductivity etc. all have uncertainty, therefore in evaluation procedure, considered the uncertainty of these factors.And be the basis with the actual production form of estimating pipeline, the carrying out of estimating involved calculating parameter extracted automatically and analyze.Automatically extraction and analysis is accomplished by software, extracts the production related data automatically, like throughput rate, pressure, inlet temperature, out-station temperature etc., and the accuracy of these data is checked.

Wherein:

The form robotization of calculating parameter is extracted and analyzed is that automatic extraction and analysis is accomplished by software; Automatically extract the production related data; Throughput rate, pressure, inlet temperature, out-station temperature, operation overall heat transfer coefficient, buried depth of pipeline, buried depth of pipeline place ground temperature, soil thermal conductivity are arranged, and the accuracy of these data is checked;

DATA DISTRIBUTION property probability statistics and check are:

Based on ISO 16708, the pipe production service data of gathering is carried out uncertainty and value analysis; Pipeline flow DATA DISTRIBUTION rule is an example in the defeated process to manage, and has chosen the data on flows of a month (month 1) flowmeter statistics to certain east pipeline, and the result sees table 1:

The statistical law of table 1 pipeline throughput rate data

Table 1,2 result show that the kurtosis of throughput rate data approaches 3, and deviation approaches 0, can think the Normal Distribution rule; The uncertainty analysis process of other mobile security implication factor as above; Also promptly: to concrete a certain pipeline, add up this pipeline production run parameter of every month (like throughput rate, out-station temperature; Environment ground temperature; Buried depth of pipeline etc.) mean value, standard deviation, kurtosis, the degree of bias, uncertainty and probability distribution analysis are carried out to the pipe production service data of gathering in the back, and in numerical simulation calculation subsequently, give corresponding probability distribution function according to the result who analyzes;

The critical throughput rate of determinacy is calculated and is:

As previously mentioned; This evaluation method has been considered the uncertainty of pipe production service data, also considers on-the-spot demand simultaneously, and the scene often need be known; Do not considering under the fluctuation situation of production run; The security of existing production run condition how, if dangerous, how to propose effective safeguard; Therefore based on the demand at scene, (extensive numerical simulation) is preceding taking a sample on a large scale, carries out earlier the initial set probability of determinacy operating mode is analyzed, and confirms its whether safety, and proposes countermeasure; The determinacy operating mode is generally on-the-spot given production data, and is given as not, is default value with the typical condition of estimating in the flow process then; Typical condition refers to the maximum corresponding numerical value of probability that the production run data occur when probability sampling; Obey just too distribution like throughput rate, its average is 73.0, and variance is 2.0; Then under not specified situation, the numerical value of throughput rate under typical condition is 73.0.

It is characterized in that drawing pipeline initial set probability calculation result is:

After obtaining the result, can draw the probability of this pipeline initial set, and the relevant risk of security that flows is estimated;

As the initial set probability less than 0.001 and current minimum safe throughput rate greater than 1.1 times of critical throughput rates; Think that then this pipeline is safe in the initial set evaluation; As the initial set probability greater than 0.001 and current minimum safe throughput rate less than 1.1 times of critical throughput rates, think that then this pipeline is unsafe; As be other, think that then there is risk in this pipeline.Be noted that especially and estimate the pipeline of thinking unsafe pipeline or having risk, need to estimate with virtual operating mode once more, and provide on-the-spot production run suggestion based on this.

The setting of said evaluation number of times and the grab sample of parameter are:

Accomplished after the deterministic parsing, just can carry out large-scale probability sampling, the sampling number of times is defaulted as 100000 times; About confirming of sampling number of times; Selecting according to 100/ (acceptable failure probability), is 0.001 like the scene to the actual effect the accepted probability of initial set, and the number of times of then taking a sample is 100000 times; As can accept the actual effect probability be 0.01 the sampling number of times be 10000 times, by that analogy; By its regularity of distribution function generate relevant numerical when the production run parameter is taken a sample at every turn, but in numerical simulation, must set the bound of production run parameter; What reason was the generation of regularity of distribution function is the numerical value that meets the mathematical distribution rule, but must not have physical significance; Under the situation that does not have the production scene appointment, the bound of system default is following, and throughput rate is between 3 times of variances of its average plus-minus, and turnover station temperature is between 0 ℃-90 ℃, and ground temperature is between negative 20 ℃-50 ℃;

The number of times that the unstable operation district was calculated and got into to the critical throughput rate of said uncertainty is:

The calculating of uncertain critical throughput rate is to analyze initial set according to the production run parameter of the evaluation number of times of having set and each evaluation number of times generation whether to take place; Then be recorded as 1 as taking place, the number of times that then can write down total entering unstable operation district after 0. evaluation is accomplished does not take place then to write down;

In whole evaluation procedure, relate to waterpower heating power during certainty and uncertain critical throughput rate are calculated and calculate, the basic ideas of calculating are to confirm temperature along the line earlier, calculate total frictional resistance based on the slight compressive characteristics of temperature along the line and crude oil.This partial content is because relatively independent, and it is a module in the evaluation method that waterpower heating power calculates, and is similar to the black box in the method for black box, and evaluation personnel and user only need be concerned about the input and output of black box, need not be concerned about the particular content of black box.Certainly, it must be noted that diverse ways relates to the accuracy of calculating, this paper has adopted waterpower heating power computing module commonly used: Su Huofu formula and corresponding to the flow resistance computing formula of different fluid.

The heating power of evaluation procedure, waterpower are calculated;

For the calculating of hot oil pipeline under given operating mode, the temperature drop situation that palpus consideration pipeline is along the line and the viscosity-temperature characteristics of oil product, influencing each other between these two factors is the coupled problem of a complicacy.Make heating power earlier and calculate, confirm that temperature variation and viscosity that pipeline is along the line change, then carry out frictional resistance and calculate and the pipeline Analysis of Working Performance, confirm the pipeline working point by the III district to the critical throughput rate of II district transition and the evaluation of follow-up initial set probability.

The calculating of the axial temperature drop of hot oil pipeline

Under the condition of stable feed, the coefficient of heat conductivity of rerum natura (specific heat capacity, density etc.), delivery technology parameter (out-station temperature, throughput rate etc.) and the buried depth of pipeline and the surrounding medium thereof of the temperature drop rate of oil stream and crude oil, temperature etc. are closely related in the hot oil pipeline.Oil stream can be described with the Su Huofu formula along the journey Temperature Distribution approx in the pipe:

T _L＝(T ₀+b)+(T _R-T ₀-b)e ^-aL (1)

In the formula: B=ig/Ca; G is the mass rate of oil product, kg/s; C is the specific heat capacity of oil product under the oil transportation medial temperature, J/ (kg ℃); D _oBe outer diameter tube, m; L is the distance apart from heating station, m; K is the pipeline overall heat transfer coefficient, W/ (m ²℃); T _RBe the oil temperature that sets off, ℃; T _LFor warm for the oil at L place apart from the heating station distance, ℃; T ₀Be ambient temperature, buried pipeline is got tube hub buried depth place nature ground temperature, ℃.

The frictional resistance of hot oil pipeline calculates

The pressure gradient of fluid in horizontal pipe is:

$i=\mathrm{\λ}\·\frac{{\mathrm{\ρV}}^2}{2D}=4f\·\frac{{\mathrm{\ρV}}^2}{2D}---\left(2\right)$

Wherein, i is a pressure gradient, Pa/m; V is the mean flow rate of pipeline inner fluid, m/s; ρ is the density of fluid, kg/m ³D is a round tube inside diameter, m; λ is the darcy coefficient of friction resistance; F is the peaceful coefficient of friction resistance of model.

The coefficient of friction resistance computing formula of newton's body laminar flow is:

$\mathrm{\λ}=\frac{64}{\mathrm{Re}}---\left(3\right)$

In the formula; μ is the kinetic viscosity of fluid, Pas.

The coefficient of friction resistance computing method of newton's body turbulent flow are more, but in turbulent hydraulically smooth region (3000＜Re＜5 * 10 ⁴) in, the coefficient of friction resistance is calculated Blasius formula commonly used.

$\mathrm{\λ}=\frac{0.3164}{{\mathrm{Re}}^{0.25}}---\left(4\right)$

Re is between 2000 to 3000, and the flow state of oil stream is generally unstable, and the coefficient of friction resistance does not still have desirable computing formula, generally calculates by formula (4).

To the power-law fluid laminar flow:

$\mathrm{\λ}=\frac{64}{{\mathrm{Re}}_{\mathrm{MR}}}---\left(5\right)$

In the formula, Re _MRBe the Metzner-Reed Reynolds number,

Wherein n is the rheological behavior index of power-law fluid; K is a consistency index, Pas ⁿ

During the power-law fluid turbulent flow, coefficient of friction resistance calculating formula commonly used is the Dodge-Metzner formula:

$\frac{1}{f^{1/2}}=\frac{4.0}{n^{0.75}}1g\left[{\mathrm{Re}}_{\mathrm{MR}}{f}^{(1-n/2)}\right]-\frac{0.4}{n^{1.2}}---\left(6\right)$

To Newtonian fluid, generally get the reynolds number Re of laminar flow when turbulent transition _C=2000.To non-Newtonian fluid, relevant with the rheological characteristics of fluid by the Reynolds number of laminar flow when the turbulent transition, the critical Reynolds number of power-law fluid can be used computes.

${\left({\mathrm{Re}}_{\mathrm{MR}}\right)}_C=\frac{{6464n(2+n)}^{(2+n)/(1+n)}}{{(1+3n)}^2}---\left(7\right)$

Frictional resistance in hot oil pipeline dl section along the line is:

${\mathrm{dh}}_R=\mathrm{\β}\frac{Q^{2-m}{v}^m}{D^{5-m}}\mathrm{dl}---\left(8\right)$

In the formula, Q is that oil product is at ducted volumetric flow rate, m ³/ s; V is a mean motion viscosity, m ²/ s; M and β are the exponential sum coefficient in the row guest ancestor formula.If ignore the effect of heat of friction, the differential relationship that can get hot oil pipeline temperature drop along the line is:

$\mathrm{dl}=-\frac{\mathrm{GC}}{{\mathrm{K\πD}}_o}\frac{\mathrm{dT}}{T-T_0}=-\frac{L}{A_R}\frac{\mathrm{dT}}{T-T_0}---\left(9\right)$

Wherein,

G=ρ Q is a mass rate, kg/s; D _oBe outer diameter tube, m; L is a station spacing, m; T ₀Be mean ground temperature between the station, ℃.

If the difference of external diameter in ignoring; With the sticking kelvin relation

and formula (9) the substitution formula (8) of crude oil, put in order through integration:

$h_R=\frac{h_{T0}}{A_R}[F\left(T_Z\right)-F\left(T_R\right)]---\left(10\right)$

Wherein, $h_{T0}=\frac{\mathrm{\β}{Q}^{2-m}{v}_{T0}^m{l}_R}{D^{5-m}};$

$F\left(T_R\right)=\exp (-\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_0})\mathrm{Ei}\left(\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_R}\right)-\mathrm{Ei}(\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_R}-\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_0});$

$F\left(T_Z\right)=\exp (-\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_0})\mathrm{Ei}\left(\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_Z}\right)-\mathrm{Ei}(\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_Z}-\frac{{\mathrm{mE}}_a}{{\mathrm{RT}}_0}).$

Equally; If wherein A, B and C are constant for

to establish the sticking kelvin relation of crude oil; Then can obtain and the consistent result of formula (10) form, wherein:

$F\left(T_R\right)=\exp (-\frac{\mathrm{mB}}{T_0-C})\mathrm{Ei}\left(\frac{\mathrm{mB}}{T_R-C}\right)-\mathrm{Ei}(\frac{\mathrm{mB}}{T_R-C}-\frac{\mathrm{mB}}{T_0-C})$

$F\left(T_Z\right)=\exp (-\frac{\mathrm{mB}}{T_0-C})\mathrm{Ei}\left(\frac{\mathrm{mB}}{T_Z-C}\right)-\mathrm{Ei}(\frac{\mathrm{mB}}{T_Z-C}-\frac{\mathrm{mB}}{T_0-C})$

No matter from any sticking kelvin relation, the throughput rate of hot oil pipeline and the relation of frictional resistance all can use formula (10) to represent.The method can with unified form describe crude oil pipe under the stream mode along the journey pressure drop.

The invention enables pipeline economical operation under the condition that guarantees security; Application through evaluation method; Make pipeline operation personnel and researchist quantitative understanding arranged to the security of pipeline; The excessive pipeline of safety allowance is formulated more economical operating scheme, and be used for the quantitative evaluation of crude oil pipeline initial set probability precisely, reliability is high.

Description of drawings

Fig. 1 pipeline initial set probability assessment process flow diagram

Fig. 2 hot oil pipeline characteristic working curve figure (u is a viscosity-temperature index)

Embodiment

Embodiment. embodiment of the present invention is described and the present invention is further described with this example.This example is a test method, and its flow process is as shown in Figure 1.

Through the method that this report proposes, the low throughput rate pipeline of domestic certain bar has been carried out the evaluation of initial set probability, the security of its operation is advised.

The statistical study of field data

Data to this pipeline Field Research obtains are carried out automatic statistical analysis, and partial results sees the following form:

Table 3 is based on the analysis of statistical data of hour form

Initial set probability calculation result and analysis

Critical throughput rate, scene are also referred to as the initial set throughput rate, and both along with the decline of pipeline throughput rate, discharge pressure raise on the contrary, at this moment pairing throughput rate.According to stopping the defeated time (seeing table 4) of this pipeline operating standard, chosen and represented different the estimating in month (March, May, July, September, November) under the defeated time of stopping.

Allow to stop the defeated time under certain pipeline scheduled overhaul of table 4 or the accident condition

The present ruuning situation analysis of certain pipeline of table 5

Through table 5, can find out that this some month of evaluation pipeline is a safety and some month is actually unsafe too, so can give the suggestion throughput rate that makes new advances based on estimating flow process in the following table.

The initial set probability of certain pipeline of table 6 under the suggestion throughput rate

According to following evaluation method: the initial set probability less than 0.001 and current minimum safe throughput rate greater than 1.1 times of critical throughput rates; Think that then this pipeline is safe in the initial set evaluation; As the initial set probability greater than 0.001 and current minimum safe throughput rate less than 1.1 times of critical throughput rates, think that then this pipeline is unsafe; As be other, think that then there is risk in this pipeline, need further to estimate.Consolidated statement 5 can find out with table 6, July with September throughput rate be (the noticing that average throughput rate is different with minimum throughput rate) that needs rise, but November and May throughput rate can reduce, and March, throughput rate can remain unchanged basically.

Be noted that especially and estimate the pipeline think unsafe pipeline or to have risk, need estimate with virtual operating mode once more, and be that the basis provides on-the-spot production run suggestion with new evaluation result.

Operation to this pipeline can propose following suggestion:

(1) the surplus adjustment can be carried out by suggestion throughput rate in the table in the scene, and concrete visible preamble is said.

(2) critical throughput rate receive oil quality characteristic influence with ruuning situation influence bigger, so as find that oil quality characteristic or production operation situation have change clearly, should reappraise.

This example is through test, to the quantitative evaluation of crude oil pipeline initial set probability precisely, reliability is high.

Claims (3)

1. a crude oil pipeline initial set probability method for quantitatively evaluating comprises: the form robotization extraction and the analysis of calculating parameter; The DATA DISTRIBUTION property probability statistics of influence factor; The critical throughput rate of determinacy is calculated; Estimate the setting of number of times and the grab sample of parameter; Uncertain critical throughput rate is calculated; Statistics gets into the calculation times in unstable operation district; Draw pipeline initial set probability calculation result; After it is characterized in that drawing pipeline initial set probability calculation result, can draw the probability of this pipeline initial set, and the relevant risk of security that flows is estimated; The initial set probability less than 0.001 and current minimum safe throughput rate greater than 1.1 times of critical throughput rates, think that then this pipeline is safe in the initial set evaluation; The initial set probability greater than 0.001 and current minimum safe throughput rate less than 1.1 times of critical throughput rates, think that then this pipeline is unsafe; As be other, think that then there is risk in this pipeline; Evaluation thought needs unsafe pipeline or have the pipeline of risk estimate with virtual operating mode once more, and provides on-the-spot production run suggestion based on this.

2. crude oil pipeline initial set probability method for quantitatively evaluating according to claim 1 is characterized in that it being that the setting of evaluation number of times and the grab sample of parameter are:

The sampling number of times is selected according to following formula, and promptly 100/ acceptable failure probability generates relevant numerical by its regularity of distribution function when the production run parameter is taken a sample at every turn, but in numerical simulation, must set the bound of production run parameter; Under the situation that does not have the production scene appointment, the bound of system default is following, and throughput rate is between 3 times of variances of its average plus-minus, and turnover station temperature is between 0 ℃-90 ℃, and ground temperature is between negative 20 ℃-50 ℃.

3. crude oil pipeline initial set probability method for quantitatively evaluating according to claim 1; It is characterized in that the number of times in unstable operation district is calculated and got into to the critical throughput rate of said uncertainty is to analyze initial set according to the production run parameter of the evaluation number of times of having set and each evaluation number of times generation whether to take place; Then be recorded as 1 as taking place, the number of times that then can write down total entering unstable operation district after 0. evaluation is accomplished does not take place then to write down.

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