Selection and Application of Chemical Foamers for … · Selection and Application of Chemical Foamers for Offshore, North Sea ... Assessing Well Suitability • ... Selection and

Gas Well Deliquification WorkshopSheraton Hotel, Denver, Colorado

February 23 - 26, 2009

Selection and Application of Chemical Foamers for Offshore, North Sea

Johannes Visser - Britannia Operator Limited

Martin J. Willis* - Nalco Limited

Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado

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Summary• Chemical foamer, Sci-Foam EC7007A, has been

successfully applied offshore North Sea in a condensate loaded well

• Performance has demonstrated clear benefits to well production;– Gas rates, liquids production and flowing time

• Product selection was a result of the robust Nalco 5 step lift process;– Extensive laboratory testing– Well specific modeling– Liaising with the operators to fully understand the issues and

concerns

• Utilising surfactant technology developed specifically for addressing liquid loading


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Contents

• Background

• Assessing Well Suitability

• Product Selection & Recommendation

• Field Trials

• The Future

• Summary


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Background• Britannia Gas Condensate Wells

– Located in UK sector of the North Sea• Block UK 16/26

– Packed completions fitted with SSVs

– Depth circa. 14,000ft

– Numerous wells showing signs of loading • >10 wells were submitted • Some already on intermittent production

– Previous attempts to use artificial lift deemed unsuccessful

– Approach to Nalco for a “Best In Class” foamer


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Rate / Mscf/d A B C D E F GWell

Tubing regim

e Water critical rate 3,208 2,208 2,276 1,866 3,186 3,175 3,383Water + Condensate critical rate 2,636 1,826 1,889 1,287 2,635 2,617 2,781Water + Foam critical rate 2,218 1,512 1,565 1,072 2,189 2,184 2,347Production rate* 11,400 6,000 5,100 5,200 6,000 5,000 9,600% above Critical 255 172 124 179 88 57 184Tubing re

gime

Casing re

gime Water critical rate 5,375 5,234 5,557 4,555 5,183 10,130 10,652

Water + Condensate critical rate 4,416 4,328 4,611 3,770 4,286 8,352 8,758Water + Foam critical rate 3,716 3,585 3,821 2,618 3,561 6,968 7,389Production rate* 11,400 6,000 5,100 5,200 6,000 5,000 9,600% above Critical 112 15 -8 14 16 -51 -10Cas

ing regim

e

* Production rates are recorded from low pressure system, not standard conditions

Assessing Well Suitability

• Nalco’s managed foamer program

• Gathered well data to run the model

• Output inferred loading in the casing region

.


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Product Selection (1 of 2)• Products available

• Key parameter was foamer testing

Water / g 5BOL Condensate / g 95N2 Flowrate / LPM 2Temperature / °C 24

Unloading conditions

Commercial Product Name

Lo Temp Stability

Hi Temp Stability

Flash Point

CEFAS Registered

EC7005A -10°C 140°C >65°C Green Gold

EC7007A -10°C 140°C >65°C Green Gold

EC7008A -15°C 130°C >65°C Red, Sub-list Gold

To be tested if green products unsuccessful


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Product Selection (2 of 2)

• Also completed additional testing;

– Viscosity profiles• Across wide temperature

range viscosity remained low

– Defoamer compatibility• Product identified to work at

levels <10% of foamer treat rate

– Chemical compatibility• Static tests showed

compatibility with majority of other system chemicals

• Only incompatibility was with an oil based product

– Material compatibility• Compatible with a range of

metals, elastomers and packing materials

– Emulsification tendency• No significant tendency

– Partitioning study• Demonstrated the foamer

will favour the water phase

– Core flood study• Various tests were

conducted reporting no impact on gas flow


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Product Recommendation

Selecting the right product is key to prevent topside upsets


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– Excellent foaming performance evident– Meets other product requirements– Sub-free and gold HQ banding to meet “green” North Sea target

Product Recommendation – Sci-Foam EC7007A

0

10

20

30

40

50

60

70

80

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

Time (min)

Upl

oad

Wei

ght (

g)

Blank

EC7007A5000ppm

EC7007A10000ppm

EC7007A15000ppm

EC7005A5000ppm

EC7005A10000ppm

EC7005A15000ppm


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Trial Proposal

• Topside squirt trial– Ensure no impact on separation performance or oil in

water levels• OiW regulated at 30 mg/l for overboard discharge in the

North Sea

• Downhole batch treatment

• Continuous application


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Topside Squirt Test• Applied volume of

foamer and anti-foam across the test separator in live well fluids

– Foamer volumes where between 5-50 l/hour

– Defoamer at 0.1 l/hour

• Results show no negative impact on OiW and maintained standard overboard discharge

0

10

20

30

40

50

60

70

80

90

100

23/0

8/20

08, 1

3:20

, bas

elin

e

23/0

8/20

08, 1

7:00

, bas

elin

e

24/0

8/20

08, 0

6:00

, bas

elin

e

24/0

8/20

08, 0

9:00

, bas

elin

e

24/0

8/20

08, 1

2:25

, 0.1

/ 5

L pe

r hr

24/0

8/20

08, 1

4:00

, 0.1

/ 10

L pe

r hr

24/0

8/20

08, 1

5:40

, 0.1

/ 15

L pe

r hr

24/0

8/20

08, 1

7:15

, 0 /

15L

per h

r

24/0

8/20

08, 1

8:00

, 0.1

/ 20

L pe

r hr

24/0

8/20

08, 2

0:00

, 0.1

/ 20

L pe

r hr

24/0

8/20

08, 2

0:45

, 0.1

/ 20

L pe

r hr

25/0

8/20

08, 0

6:00

, bas

elin

e

25/0

8/20

08, 0

8:30

, 0.1

/ 25

L pe

r hr

25/0

8/20

08, 0

8:55

, 0.1

/ 25

L pe

r hr

25/0

8/20

08, 1

0:20

, 0.1

/ 30

L pe

r hr

25/0

8/20

08, 1

2:10

, 0 /

30L

per h

r

25/0

8/20

08, 1

3:05

, 0 /

30L

per h

r

25/0

8/20

08, 1

4:30

, 0.1

/ 35

L pe

r hr

25/0

8/20

08, 1

4:55

, 0.1

/ 35

L pe

r hr

25/0

8/20

08, 1

6:30

, 0.1

/ 40

L pe

r hr

25/0

8/20

08, 1

8:40

, 0.1

/ 50

L pe

r hr

Oil

in w

ater

con

tent

(mg/

l)

Oil in water content at Degasser and MP Separator Outlets

DegasserMP

Separator


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Downhole Batch Treatment (1 of 2)• 320 litres / 84 gals (~30,000ppm of calculated liquid volume) of

foamer was pumped down the production tubing of well G

• Well shut-in for 20 hours and allowed to build up to a wellhead pressure of 56 bar / 812 psi

• Well flowed back into HP separator– Only initial surge observed, well did not kick

• Shut-in again for 1.5 hour until the wellhead pressure reached 56 bar / 812 psi

• Well flowed into MP separator– significant kick observed


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Downhole Batch Treatment (2 of 2)C

umul

ativ

e co

nden

sate

/ B

PD

Gas

rate

/ m

msc

f/d

Oct 08 Chemical clean up

Jul 08 Clean up

Oct 08 Gas rate

Jul 08 Gas rate

Variable Previous flow back

Trial results % Gain

Condensate within 30mins / bbls 5 40 700Gas rate after 30mins / mmscfd 5 6.5 30

Condensate after 12 hours / bbls 50 81 62Well uptime / days 6-8 63 >685

North Sea Field Trial - DH Batch


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The Future

• Britannia is considering additional batch treatments – Condensate dominant wells– Water loaded wells

• Britannia is currently reviewing potential for continuous foamer application– Capillary string material and performance compatibility

completed• Passed all the material compatibilities• Showed product stability at 200°C, 7000psi for ~4 hours


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Summary• Chemical foamer, Sci-Foam EC7007A, has been

successfully applied offshore North Sea in a condensate loaded well

• Performance has demonstrated clear benefits to well production;– Gas rates, liquids production and flowing time

• Product selection was a result of the robust Nalco 5 step lift process;– Extensive laboratory testing– Well specific modeling– Liaising with the operators to fully understand the issues and

concerns

• Utilising surfactant technology developed specifically for addressing liquid loading


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Acknowledgements

• The authors wish to thank;– Britannia Operator Limited and their Co-Venturers– Nalco Company


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Selection and Application of Chemical Foamers for … · Selection and Application of Chemical Foamers for Offshore, North Sea ... Assessing Well Suitability • ... Selection and