Current Development of Ultra High Temperature Aqueous and Non-Aqueous Drilling Fluids

2

Outlines

IntroductionKey issueWeighting material affects ECDDevelopmental work and findings:

Emulsifiers Rheological modifiers and filtration control additives

Non-aqueous drilling fluid tested in HTHP viscometerSummary on non-aqueous drilling fluidAqueous drilling fluidSummary on aqueous drilling fluidQ&A

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Introduction

UHTHP = 200 to 250C with mud density > 1.75 SG.In 2007, Scomi Oiltools has consistently encountered high angle wells with bottom hole static temperature between 200 to 210C in the Gulf of Thailand.

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Key issue

When drilling reached TD, fluid in static condition

= more likely to cause problem.

When drilling to TD, fluid in dynamic condition

= less likely to cause problem.

Problems related to:Pressure management Induced factureBarite sag NPT during POOH

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Key issueFigure 2 – YP Response to Temperature in Dynamic

Condition with baseline YP at 49°C; BHST 210C

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Key issue

Figure 3 – YP Response to Temperature in Static Condition with baseline YP at 49°C; BHST 210C

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Weighting material affects ECD

Earlier lab work is based on API grade barite (4.2 SG).We are seeing the following weighing materials improve the rheology stability of the drilling fluid:

99.5% hematite. 98% ilmenite. 4.4+ SG barite.

Lower SG materials = higher impurities

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Weighting material affects ECD

Barite SG4.54.44.34.24.14.0

% Volume by SG % Weight by SGTable 1 - % of HGS and LGS in field barite

100%95%89%84%79%74%

HGS100%97%94%90%87%83%

HGSLGS LGS0% 0%5% 3%

11% 6%16% 10%21% 13%26% 17%

HGS = 4.5 SG

LGS = 2.6 SG

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Weighting material affects ECD

Barite TotalSG lb/bbl

4.5 6254.4 6294.3 6324.2 6364.1 6404.0 644

Table 2 – HGS and LGS in barite - 2.3 SG mud

HGSlb/bbl

625609592574555534

LGSlb/bbl

020406285110

HGS = 4.5 SG

LGS = 2.6 SG

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Selection of emulsifiers

Traditional emulsifiers package offered. Primary and secondary emulsifiers. Tall Oil Fatty Acid (TOFA) based.

Improvements in current available emulsifiers. Citric acid replaces fumaric/maleic acid. Tricarboxylic acid substituting a

dicarboxylic acid chain.Advantages of new emulsifiers.

Higher temperature stability. Improve rheological properties.

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Selection of emulsifiers

Table 3 - Emulsifier performance

Emulsifier DesignationP-S Pair

A B C D

Mud density, SG using API barite

2.1 to 2.2 to 2.2 to 2.2 1.5

Maximum stability - extended exposure, C

160 221 to 250 250+ 300

Termination - maleic anhydride or citric acid

maleic maleic maleic citric NA

Additive requirement for acid gas

Excess lime

Excess lime

Excess lime

Excess lime

None – stable

Control of progressive viscosity

Poor Good Good Excellen

tGood

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Rheological modifiers and filtration control additives

Table 4 - Viscosifiers and filtration control materials performance

Emulsifier DesignationP-S Pair

A B C D

Organophyllic hectorite - rheological additive, also improves filtration control. Extended temperature stability, to C

175 221221+

221+ Poor

Organophyllic bentonite - rheological additive, also improves filtration control. Temperature stability, to C

160 175 175 175 Poor

Liquid polymeric filtration control additive, C (often significant rheological effect)

175 221<25

0250+ 300

Synthetic copolymer filtration control additive, C

not useful

221<25

0250+ 300

Gilsonite - 450F version, lb/bbl   16+ 16+ 16+  

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Non-aqueous drilling fluid tested in HTHP viscometerFigure 4 – Standard formulation synthetic based

mud1.92 SG 80/20 SBM Formulated with P&S, post 24h hot roll @ 200°CRheological Properties Reported by HTHP Viscometer

0

10

20

30

40

50

60

70

40 60 80 100 120 140 160 180 200 220 240Temperature - °C

Rheolo

gic

al valu

es -

cP

, lb

/100ft2 YP, lb/100ft2 6 RPM, ° 10min gel, lb/100ft2 100 RPM, °

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Non-aqueous drilling fluid tested in HTHP viscometer

Figure 5 – Special UHT Non-sag mud formulation 1.92 SG SBM Formulated with Emulsifier B, post 24h hot roll @ 200°C

Rheological Properties Reported by HTHP Viscometer

0

10

20

30

40

50

60

70

40 60 80 100 120 140 160 180 200 220 240Temperature - °C

Rheolo

gic

al valu

es -

cP

, lb

/100ft

2

YP, lb/100ft2 6 RPM, ° 10min gel, lb/100ft2 100 RPM, °

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Non-aqueous drilling fluid tested in HTHP viscometer

Figure 6 – Rheologically optimized mud formulation1.92 SG SBM Formulated with Emulsifier B1, post 24h hot roll @ 200°C

Rheological Properties Reported by HTHP Viscometer

0

10

20

30

40

50

60

70

40 60 80 100 120 140 160 180 200 220 240Temperature - °C

Rheolo

gic

al valu

es -

cP

, lb

/100ft

2

YP, lb/100ft2 6 RPM, ° 10min gel, lb/100ft2 100 RPM, °

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Summary on non-aqueous fluid

Weighting material Important to source quality material to

reduce contaminants.New improved emulsifier

Higher temperature stability. Better control of progressive rheology. Enhances temperature stability of other

mud components.

Aqueous Drilling Fluid

Better pressure management and prevention sag

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Aqueous drilling fluid

UHTHP aqueous drilling fluidSimilar problems associated with barite sag and pressure management.Limitations:

Degradation of polymer. Flocculation of drill solids.

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Aqueous drilling fluid – Degradation of polymer

Figure 7 – Thermal degradation of two polymeric UHTHP filtration control materials for aqueous

drilling fluid

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Aqueous drilling fluid – Flocculation of drill solids

Available low molecular weight dispersants are effective.

Start fresh drilling fluid with low LGS. Maintain minimum drill solids contamination.

Flocculation of drill solids

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Summary on aqueous drilling fluid

UHT polymeric viscosifier Capable to function as viscosifier and

filtration control additive. Higher temperature stability.

Low molecular weight dispersant Effective at low LGS contamination.

Contamination Start drilling fluid with minimum LGS. Maintain minimum drill solids in fluid.