No Slide Title - Aker Solutions

Snøhvit experience with
low flow rate operation
Flow Assurance and
Dynamic simulations seminar
Aker Solutions 21.10.2010
PHOTO: Even Edland / Statoil

Contents
• Introduction
• Field experience and model tuning
• Model vs. field measurements
Initial start-up
High and low production rates
Liquid surges
• Summary

Introduction – Snøhvit field
143 km
28 “ OD
E
D
F
N
PHOTO: Even Edland / StatoilHydro

Snøhvit initial start-up
• Initial start-up from gas filled pipeline
MEG/water
Condensate
• Three planned steps:
1. Gas sweeping at low pressure
2. Low rate operation (time limited)
3. Production ramp-up
Low rate – high uncertainty
High rate – low uncertainty

Field experience and measurements
• Assess and improve uncertainty in simulations
− Need for high quality data
• Pressure drop
• Flow rates (all phases)
• Liquid content (all liquid phases)
• Liquid content measured by:
− Pigging operations
− Tracer technique
Tracer
response
t = 0
t = T

Use of field data for new projects
TOOLS
MULTIPHASE
MODELS
OLGA
Field experience
and measurements
TUNED MODELS ARE
SYSTEM/FIELD
DEPENDENT!
Combine knowledge
and tune models
Standard OLGA
Tuned OLGA

Multiphase model tuning
Hydraulic similar field case
Resulting Snøhvit models
Midgard field
measurements and tuning
TOTAL LIQUID
MEG/WATER

Initial start-up and total liquid content
TOTAL LIQUID
Estimated accuracy:
15-20% too low

Initial start-up and MEG/water content
MEG/WATER
Estimated accuracy:

Initial start-up and pressure drop
Consistent with
too low total
liquid content
Difference caused
by MEG/water
predictions
Estimated accuracy:

Pressure drop at various flow rates
within 2%

Liquid surges during start-up
(after shut-down)
Condensate
MEG/water

Measured liquid surges (high flowrate)
CONDENSATE
NOT predicted correctly by
multiphase flow simulator!
MEG/WATER

Summary
• Field experience and measurements are important for evaluation and tuning of
multiphase flow models
− improved accuracy for pressure drop and liquid content
− the tuned Snøhvit model is superior to the standard model and simulation results can
be used in prediction and planning of operations with good accuracy
• Low flow rate operation (gravity dominated flow) is challenging
− liquid control
− inaccurate models
− minor pressure/rate variations has large inpact on liquid content
• Flow instabilities are hard to predict
− unstable flow at both low and high flow rates (unexpected)
• Further analyses and field experience from Snøhvit will be used for improving the
multiphase flow models and for prediction uncertainty assessments

Thank you
Snøhvit experience with low flow rate operation
Geir Stian Landsverk
Principal Engineer, Multiphase Flow and Flow Assurance
gsla@statoil.com
www.statoil.com