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SUBPRO SUBSEA PRODUCTION AND PROCESSING
Analysis of Influence of Sensor Degradation on Flowrate Estimates by Virtual Flow Metering Systems PhD candidate: Timur Bikmukhametov Supervisor: Associate Professor Johannes Jäschke
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Virtual Flow Metering system
Mass conservation Momentum equation Energy equation
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Influence of sensor degradation Heat transfer modelling It does!
Topics Influence of sensor degradation Heat transfer modelling It does! Simple doesn’t mean bad
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Pressure/temperature sensor degradation
± 0.1 % uncertainty ± 0.5 % uncertainty ± 1 % uncertainty
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VFM software
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Monte Carlo Simulations 98% confidence 40 - 130 simulations per case
Simulation setup Twh, Pwh Twf, Pwf Pwh_meas = 0.99·Pwh ·Pwh Twh_meas = 0.99·Twh ·Twh 1 % uncertainty Monte Carlo Simulations 98% confidence simulations per case Optimizer min ∑ ( 𝑋 𝑚𝑒𝑎𝑠 – 𝑋 𝑂𝐿𝐺𝐴 ) 2 𝑚 1 % uncertainty Pwf_meas = 0.99·Pwf ·Pwf Twf_meas = 0.99·Twf ·Twf
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System Parameter Value Pwh 40 bar Pwf 160 bar Twh 57 ⁰C Twf 70 ⁰C
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Standard deviation, bbl/day
Pressure/temperature sensor degradation Case Mean, bbl/day Standard deviation, bbl/day 0.1% 16073 23.03 0.5% 16069 110.03 1% 16079 212.7
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Standard deviation, SCM/day
Pressure/temperature sensor degradation Case Mean, SCM/day Standard deviation, SCM/day 0.1% 393991 565.67 0.5% 393906 1% 394149
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Temperature sensor failure
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Temperature sensor failure
Study 2 Temperature sensor failure True Twf does not change True Twf changes +5% drop - 5% drop
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Standard deviation, bbl/day
Temperature sensor failure, Twf does not change Case Mean, bbl/day Standard deviation, bbl/day No failure 212.68 Sensor failure 242.66
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Temperature sensor failure, Twf changes
160 105
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Heat transfer modeling
𝑄=𝑈( 𝑇 𝑓 − 𝑇 𝑎𝑚𝑏 )
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Total (unique) U-value
Multiple U-value method Heat transfer modeling Total (unique) U-value method Twh U1 U2 U total U3 U4 U5 Twf
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+ 2𝛑𝑅𝐿 𝐾 𝑓𝑜𝑟𝑚 𝑇 𝑐𝑒𝑚 − 𝑇 𝑤𝑎𝑙𝑙 𝑇 𝐷 +
𝑄=𝑈 𝑇 𝑓 − 𝑇 𝑎𝑚𝑏 = 2𝛑𝑅𝐿 ℎ 𝑖𝑛𝑛𝑒𝑟 𝑇 𝑓 − 𝑇 𝑤𝑎𝑙𝑙 + + 2𝛑𝑅𝐿 𝐾 𝑓𝑜𝑟𝑚 𝑇 𝑐𝑒𝑚 − 𝑇 𝑤𝑎𝑙𝑙 𝑇 𝐷 + 2𝛑𝑅𝐿 𝐾 𝑖 𝑇 𝑖+1 − 𝑇 𝑖 𝑙𝑛 𝑅 𝑖 𝑅 𝑖+1
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Well structure 57 ⁰C 70 ⁰C
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Temperature profile
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Sensitivity study m = ; 4; 6 … kg/s T = 57; …; …; … ⁰C 𝚫𝑇 𝚫𝑚 = ?
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Conclusions Sensor degradation has an impact on flowrate estimates Failure of temperature sensors makes estimates less accurate Segmented approach does not give an advantage if Twh is known Segmented approach might be better if Twh is unknown or T is measured along the wellbore
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Further work Perform the analysis for different GOR values and a gas well Identify the most critical points in the system
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Order of magnitude analysis
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𝑈2 𝑈1 =1.5 Matching the wellhead temperature = 20 𝑊 𝑚 2 𝐾 21 𝑊 𝑚 2 𝐾
= 20 𝑊 𝑚 2 𝐾 21 𝑊 𝑚 2 𝐾 22 𝑊 𝑚 2 𝐾 𝑈2 𝑈1 =1.5 = 30 𝑊 𝑚 2 𝐾 31.5 𝑊 𝑚 2 𝐾 33 𝑊 𝑚 2 𝐾 Uunique= 24 𝑊 𝑚 2 𝐾
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