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 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 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 Barite SG % Volume by SG% Weight by SG Table 1 - % of HGS and LGS in field barite 100% 95% 89% 84% 79% 74% HGS 100% 97% 94% 90% 87% 83% HGSLGS 0% 5%3% 11%6% 16%10% 21%13% 26%17% HGS = 4.5 SG LGS = 2.6 SG

9 Weighting material affects ECD BariteTotal SGlb/bbl Table 2 – HGS and LGS in barite SG mud HGS lb/bbl LGS lb/bbl 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 Table 3 - Emulsifier performance Emulsifier DesignationP-S PairABCD Mud density, SG using API barite2.1to Maximum stability - extended exposure,  C to Termination - maleic anhydride or citric acid maleic citricNA Additive requirement for acid gas Excess lime None – stable Control of progressive viscosityPoorGood ExcellentGood

12 Rheological modifiers and filtration control additives Table 4 - Viscosifiers and filtration control materials performance Emulsifier Designation P-S Pair ABCD Organophyllic hectorite - rheological additive, also improves filtration control. Extended temperature stability, to  C Poor Organophyllic bentonite - rheological additive, also improves filtration control. Temperature stability, to  C Poor Liquid polymeric filtration control additive,  C (often significant rheological effect) < Synthetic copolymer filtration control additive,  C not useful 221< Gilsonite  F version, lb/bbl 16+

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. Aqueous Drilling Fluid Better pressure management and prevention sag

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

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.