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

Current Development of Ultra High Temperature Aqueous and Non-Aqueous Drilling Fluids. Outlines. Introduction Key issue Weighting material affects ECD Developmental work and findings: Emulsifiers Rheological modifiers and filtration control additives

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

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

  2. Outlines • Introduction • Key issue • Weighting material affects ECD • Developmental work and findings: • Emulsifiers • Rheological modifiers and filtration control additives • Non-aqueous drilling fluid tested in HTHP viscometer • Summary on non-aqueous drilling fluid • Aqueous drilling fluid • Summary on aqueous drilling fluid • Q&A

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

  4. Key issue • When drilling to TD, fluid in dynamic condition = less likely to cause problem. • When drilling reached TD, fluid in static condition = more likely to causeproblem. Problems related to: Pressure management • Induced facture Barite sag • NPT during POOH

  5. Key issue Figure 2 – YP Response to Temperature in Dynamic Condition with baseline YP at 49°C; BHST 210C

  6. Key issue Figure 3 – YP Response to Temperature in Static Condition with baseline YP at 49°C; BHST 210C

  7. 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

  8. Weighting material affects ECD Table 1 - % of HGS and LGS in field barite Barite % Volume by SG % Weight by SG SG HGS LGS HGS LGS 4.5 100% 0% 100% 0% 4.4 95% 5% 97% 3% 4.3 89% 11% 94% 6% 4.2 84% 16% 90% 10% 4.1 79% 21% 87% 13% 4.0 74% 26% 83% 17% HGS = 4.5 SG LGS = 2.6 SG

  9. Weighting material affects ECD Table 2 – HGS and LGS in barite - 2.3 SG mud Barite Total HGS LGS SG lb/bbl lb/bbl lb/bbl 625 625 0 4.5 4.4 629 609 20 4.3 632 592 40 4.2 636 574 62 4.1 640 555 85 4.0 644 534 110 HGS = 4.5 SG LGS = 2.6 SG

  10. 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.

  11. Selection of emulsifiers

  12. Rheological modifiers and filtration control additives

  13. Non-aqueous drilling fluid tested in HTHP viscometer Figure 4 – Standard formulation synthetic based mud

  14. Non-aqueous drilling fluid tested in HTHP viscometer Figure 5 – Special UHT Non-sag mud formulation

  15. Non-aqueous drilling fluid tested in HTHP viscometer Figure 6 – Rheologically optimized mud formulation

  16. 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. Better pressure management and prevention sag Aqueous Drilling Fluid

  17. Aqueous drilling fluid UHTHP aqueous drilling fluid • Similar problems associated with barite sag and pressure management. • Limitations: • Degradation of polymer. • Flocculation of drill solids.

  18. Aqueous drilling fluid – Degradation of polymer Figure 7 – Thermal degradation of two polymeric UHTHP filtration control materials for aqueous drilling fluid

  19. Aqueous drilling fluid – Flocculation of drill solids • Flocculation of drill solids • Available low molecular weight dispersants are effective. • Start fresh drilling fluid with low LGS. • Maintain minimum drill solids contamination.

  20. 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.

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