well testing – an evaluation of test separators and ... · pdf filewell testing –...

Well Testing – An Evaluation of Test Separators and Multiphase Flow Metersp

Oil & Gas Focus GroupWednesday 14th September 2011

Amy Ross, NEL

Wednesday 14 September 2011

y ,

Contents

• Why are you well testing?

• Test Separators– Metering

Utili ti– Utilization

• What makes a good well test?

• Multiphase Meters– Performance– Utilization

• Conclusions• Conclusions

Why are you well testing?

• Determination of fluid flow rates

D t i ti f h h i fl id fl• Determination of when changes in fluid flow rates/composition occur

• Identification of mechanical integrity issue• Identification of mechanical integrity issue

• Because the Regulator has told you to...

Contents







How do you well test?

gas

oilwater

The gold standard

Works well if...

• Separator is sized correctly

I t f l l it bl i t i d• Interface levels are suitably maintained

• Flow meters are adequately sized

• Flow meters installed in recommended orientation with required upstream and downstream straight lengthsdo s ea s a g e g s

• Flow meters are regularly inspected and calibrated

• Secondary instrumentation are regularly calibrated

Test Separator - Metering

Test Separator – Other issues

Test Separator – Metering Uncertainties

Gas UncertaintiesB t ±2%• Best ±2%

• More likely ±3% to ±6%• Extreme ±10% to ±15%

Liquid UncertaintiesBest ±1% to ±2%• Best ±1% to ±2%

• More likely ±2% to ±5%• Extreme ±5% to ±10%

Test Separator - Utilization • Regular well testing

• Other well testsOther well tests

• Separator use during well service operations

• Other uses• Other uses

– Start up of low pressure wells after shut down

Test a multiphase flow meter– Test a multiphase flow meter

• Separator maintenance & inspection

PSV’ f t t– PSV’s, safety systems

– Removal of solids

– Instrument calibration

Contents







What makes a good well test?

• One which follows the previous well tests, therefore demonstrating repeatabilitydemonstrating repeatability

• One which is within the stipulated period of 30 days

• Identification of mechanical integrity issue• Identification of mechanical integrity issue

• One which has been carried out for the stipulated length of time (12 or 24 hours)o e ( o ou s)

Just ticking the boxes – need to look at the bigger pictureJust ticking the boxes need to look at the bigger picture

GVF > 90%, WC ≈ 60%

Flow Rates

Fluids – Green - Oil,Blue – Water, Yellow - Gas

Flow Rates

5

10

Liqu

id [m

3/h]

Flow Rates

300

400

Gas

[m3/

h]

0 50 100 150 200 2500

0 50 100 150 200 250200

4000

5000Venturi dPVenturi dP

0 50 100 150 200 2500

1000

2000

3000

mB

ar

GVF & WLRGVF and WLR

50

100

[%]

GVF & WLR

WLRGVF

GVF and WLR

0 50 100 150 200 2500

Time [Minutes]

Slugging, WC ≈ 0 to 70%

40Flow Rates

400

Liquids – Green - Oil ,Blue – Water, Yellow - GasFlow Rates

10

20

30

40

Liqu

id [m

3/h]

100

200

300

400

Gas

[m3/

h]

0 20 40 60 80 100 1200

0 20 40 60 80 100 1200

4000


0 20 40 60 80 100 1200

1000

2000

3000

mB

ar

GVF and WLR

50

100

[%]

GVF & WLR

WLRGVF

GVF and WLR

0 20 40 60 80 100 1200

Time [Minutes]

GVF > 90%, WC > 90%

Flow Rates

Liquids – Green - Oil ,Blue – Water, Yellow - GasFlow Rates

10

20

30

40

Liqu

id [m

3/h]

Flow Rates

100

200

300

Gas

[m3/

h]

0 50 100 150 200 250 300 350 400 4500

0 50 100 150 200 250 300 350 400 4500

4000


0 50 100 150 200 250 300 350 400 4500

1000

2000

3000

mB

ar

GVF and WLR

50

100

[%]

GVF & WLR

WLRGVF

GVF and WLR

0 50 100 150 200 250 300 350 400 4500

Time [Minutes]

Contents







Multiphase Flow Meters

• Capable of continuous measurementp

• Stabilise their process conditions much more quickly that a test separator

• Key to economic development of smaller, more marginal fields

However....

• Have performance claims been met?

• What steps are necessary to achieve success?

• Successes are aired but what about the failures?

Multiphase Flow Meter Performance

Uncertainties of ±10% to ± 25%

Cut

(%)

(%)

Wat

er C

GVF (%)

Multiphase Flow Meter PerformanceNow....

•Auto-switchable between multiphase and wet gasp g

•Wet gas uncertainties

o Better than ±5% for liquid flow rateo Better than ±5% for liquid flow rate

o ±2% to ±5% for gas flow rate

o Better than ±2% (abs) for water detectiono Better than ±2% (abs) for water detection

•Multiphase uncertainties

o ±2% to ±5% for liquid flow rateo ±2% to ±5% for liquid flow rate

o ±2% to ±5% for gas flow rate

±1% t ±8% f t to ±1% to ±8% for water cut

Multiphase Flow Meter Performance

How have these improvements been achieved?

• Competition between vendors• Open and independent Joint Industry Projectsp p y j• Significant R&D expenditure by vendors, operators,

universities, etc• Innovative alliances by vendors and operators• Innovative alliances by vendors and operators• Users becoming MPFM aware• Improvements in flow models• Improvements in computing power• Some very awkward individuals asking very

awkward questionsawkward questions

Test Separator - Utilization

• Regular well testing

• Other well tests

Could be achieved by MPFM

Could be achieved by MPFMOther well tests

• Separator use during well service operations

• Other uses

Could be achieved by MPFM

• Other uses

– Start up of low pressure wells after shut down

Test a multiphase flow meter– Test a multiphase flow meter

• Separator maintenance & inspection

PSV’ f t t– PSV’s, safety systems

– Removal of solids

– Instrument calibration

Multiphase Flow Meter Utilization

Test Separator

FM gas

Test Manifold 1

FM

FM

oil

waterMultiphase /

Test Manifold 2

1st Stage

gas

waterMultiphase / Wet Gas Meter

1st Stage Separator

oilProduction M if ld waterManifold

From wells

Multiphase Meters

How do you reconcile a multiphase flow meter i t th t t t ?against the test separator?

gas

MPFM

oilwater

MPFM

oilwater

Contents







Conclusions

• Well testing must be done

• Test separators are seen as the gold standard

– Often not suitably maintained or operatedy p

– Over utilized

• Multiphase meter technology has improved greatly over u t p ase ete tec o ogy as p o ed g eat y o ethe past 20 years

• Multiphase meter performance will continue to improve IF vendors and operators work together

• Opportunity for multiphase meters to compliment test tseparators

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