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The document discusses the use of formate brines, specifically cesium formate brine, as drilling, completion and suspension fluids for deep, high pressure high temperature (HPHT) gas wells. Cesium formate brine provides benefits such as stability at high temperatures, compatibility with reservoirs, and less corrosion and damage compared to other brines. It has been used successfully in over 50 HPHT gas field developments worldwide, enabling improved well construction methods like open hole completions.
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- 4. Formate brines Important applicational niche in deep HPHT work Low-solids fluids for deep HPHT gas well constructions Reservoir drill-in Completions Workovers Packer and long-term well suspensions A mature field proven technology used in deep gas fields since 1995
- 5. 13Cr tubular from BP High Island well : 6 years exposure to 11.5 ppg formate brine packer fluid @175 o C
- 6. Conventional formate drilling fluid formulation - in field use since 1993 and good to 160 oC Simple, effective, non-damaging reservoir drill-in fluid Used to drill entire wells, top to bottom, in sensitive environments (e.g. Barents Sea) Component Function Concentration Formate brine Density Lubricity Polymer protection Biocide 1 bbl Xanthan Viscosity Fluid loss control 0.75 - 1 ppb Ultralow vis PAC and modified starch Fluid loss control 3 or 4 ppb of each Sized calcium carbonate Filter cake agent 20 ppb K 2 CO 3 /KHCO 3 Buffer Acid gas corrosion control 0 – 6 ppb
- 8. 1995 – Formate brines used for first time by Mobil to drill and work over deep gas wells, onshore , northern Germany Walsrode field – onshore, high-angle slim hole wells Z1, Z5, Z6 and Z7 TVD : 4,450-5,547 metres Reservoir: Sandstone 0.1-125 mD BHST : 315 o F (157 o C) Section length: 345-650 metres
- 9. 42 d eep HPHT gas fields developed using potassium and cesium formate brines, 1995-2011 Country Fields Reservoir Description Matrix type Depth, TVD (metres) Permeability (mD) Temperature ( o C) Germany (7) Walsrode,Sohlingen Voelkersen,I dsingen, Kalle, Weissenmoor, Simonswolde Sandstone 4,450-6,500 0.1-150 150-165 Hungary (2) Mako , Vetyem Sandstone 5,692 - 235 Kazakhstan (1) Kashagan Carbonate 4,595-5,088 - 100 Norway (10) Huldra ,Njord Kristin,Kvitebjoern Tune, Valemon Victoria, Morvin, Vega, Asgard Sandstone 4,090-7,380 50-1,000 121-200 Pakistan (2) Miano, Sawan Sandstone 3,400 10-5,000 175 Saudi Arabia (7) Andar,Shedgum Uthmaniyah Hawiyah,Haradh Tinat, Midrikah Sandstone and carbonate 3,963-4,572 0.1-40 132-154 UK (12) Braemar,Devenick Dunbar,Elgin Franklin,Glenelg Judy, Jura, Kessog Rhum, Shearwater West Franklin Sandstone 4,500-7,353 0.01-1,000 123-207 USA (1) High Island Sandstone 4,833 - 177
- 10. Cesium formate brine : Drill-in, completion, workover and suspension fluid for HPHT gas wells Density up to 19.2 ppg/SG 2.3 Drill-in and completion fluid Non-toxic, non-hazardous – safe to handle Little or no risk to the environment Compatible with all reservoirs Extends the thermal stability of polymers Less corrosive than bromide brines Stabilises shales Inhibits hydrates
- 11. Cesium formate brine produced by Cabot Specialty Fluids in Canada from pollucite ore Pollucite ore Cs 0.7 Na 0.2 Rb 0.04 Al 0.9 Si 2.1 O 6 ·(H 2 0) Mined at Bernic Lake, Manitoba Processed on site to Cs formate brine Cs formate brine production 8,000 bbl p.a. of 19.2 ppg Brine stocks > 30,000 bbl @ 19.2 ppg Brine supplied on leasing terms (i.e. per bbl per day) Currently manage 30-40 jobs per year
- 12. Leasing cesium formate brine Green and sustainable model – recognised by United Nations Conservation ( i.e. minimisation of cesium formate brine losses during transport, use and reclamation) is a key and essential feature of Cabot’s Chemical Leasing business model
- 13. Key applications for cesium formate brine Drill-in and completion fluids for enhancing the safety and economics of HPHT gas field developments
- 14. Cesium formate brine - Field applications 277 jobs in 50 field developments* (see website for list) Drill-in - 33 Completions - 156 (131 WB and 25 OB) - as a brine and in LSOBM formulations (up to 1.60 SG) - outstanding as HPHT perforating kill pill (Visund, Braemar, Judy, Rhum) Workovers (27) and miscellaneous (61) Includes diverse uses: - Well suspension - Well testing - Stuck-pipe release pill (OBM drilling) - Melting hydrate plugs - Also now being used in deep shale gas wells in USA * not all HPHT
- 15. Shell UK was the first user of cesium formate brine – Shearwater field, September 1999 17.20 – 18.86 ppg completion and workover fluid Shearwater field – UK North Sea Gas condensate reservoir 15,000 psi BHST 365 o F 10 cesium formate jobs to date
- 16. Use of cesium formate by Total as HPHT completion and workover fluid Initial use as18.2 ppg completion fluid in 8 Elgin/Franklin wells World’s largest HPHT field Gas condensate reservoir 16,000 psi @ 20,000ft BHST 200 oC 140,000 bbl/day of condensate 13 million m 3 gas /day Cesium formate brine has now been used by TOTAL in 34 HPHT well construction operations in 8 deep gas fields over the period 1999-2010
- 17. Some HPHT perforating jobs Glenelg 22/30c-GLA - 195 o C - No perforating pill. - Losses 2m 3 on perf, 15.7m 3 seepage after Kessog 30/1c-09 - 170 o C - 200m blocking pill column above perforation zone - 45min – 0.36m 3 lost - Next hour – 0.22m 3 lost - Next 7.5 hours – 0.6m 3 lost Jura 1 3/15-10 - 127 o C - Blocking pill over perfs - 1.5 m 3 lost over 15 hours post perforation Braemar 16/3b-8z - 135 o C - No perforating pill - Perf losses 14.5 bbl
- 18. Cesium formate brine Where does it provide the highest value ? As a combined drill-in and completion fluid - enabling operators to construct high-angle open hole screen completions in HPHT tight gas reservoirs Combined drilling and completion fluid (“one filtrate”) Non-damaging to reservoir and screens Cleans-up naturally during start-up (10-20 hours) Low skins No well stimulation required Perhaps the only fluid that can do this in an HPHT environment
- 19. Advantages of open hole screen completions in high-angle HPHT wells* Improved economics and lower risk Maximise reservoir contact and production - Larger inflow areas in contact with reserves - Allow higher flow rates with lower flow resistance - Good results (low skins) with stand-alone screens Lower cost - Quicker and easier to install, less NPT - 10% lower tangibles cost More robust than cased holes - Less affected by formation compaction over time Lower HSE risk than cased holes - No explosives , no live well work, fewer lifts, etc * From “HPHT Wells Best Practices Course” by Think Well Ltd
- 20. Cesium formate brine used by BP and Statoil as combined HPHT drill-in and completion fluid in N. Sea 28 high-angle development* wells drilled and completed in 6 HPHT offshore gas fields Huldra (6 ) Devenick (1) Kvitebjoern (8 O/B and 5 MPD) Valemon (1) Kristin (2) Vega (5) * Except Devenick and Valemon (appraisal wells ) Mostly open hole stand-alone sand screen completions Also Tune field : drilled with 13.3 ppg K formate brine , completed in K/Cs formate brine and suspended in K/Cs formate brine for 6-12 months
- 21. Tune field – semi-HP/HT gas reservoir in the North Sea drilled and completed with formate brines 4 wells : 1,100-2,950 ft (350-900 m) horizontal reservoir sections. Suspended for 6-12 months in K/Cs formate brine after completion
- 22. HPHT gas fields in northern North Sea drilled and completed with cesium formate brine Almost every field development (oil and gas) on this map has used formate brines as well construction fluids . Zinc bromide brine no longer used in Europe – too hazardous and damaging
- 23. HPHT gas fields in the Norwegian Sea drilled and completed with cesium formate brine Formate brines also used as well construction fluids in Asgard, Draugen, Morvin and Njord fields
- 24. Offshore Norway Gas condensate field 6 wells BHST: 297 o F (147 o C) TVD : 12,795 ft (3,900 m) Fluid density: 15.76- 16.34 ppg (SG1.89-1.96) 754-1,125 ft (230-343 m) x 8 1 / 2 ” reservoir sections Hole angle : 45-55 o 1–2 Darcy sandstone Open hole completions, 6 5 /8 ” wire wrapped screens Cesium formate brine first used as a combined drill-in and completion fluid in the Huldra field, 2001
- 25. Huldra – drill-in, logging and completion times (days) with cesium formate brine in well Drill, log and run lower completion in drilling fluid. Then displace to clean cesium formate brine and run upper completion. Finally displace to packer fluid A-4 (189 m ) A-5 (263 m) A-6 (344 m) A-8 (257 m) A-9 (230 m) A-11 (336 m) Average (231 m) Drill-in 5 8 20 15 7 11 11 Logging 0 3 1 7 3 2 2.7 Lower completion 11 6 5 6 5 5 6.3 Upper completion 4 5 4 4 9 4 5 Total 20 22 30 32 24 22 25
- 26. Huldra – Fluid losses while drilling (cubic metres) A-4 (189 m ) A-5 (263 m) A-6 (344 m) A-8 (257 m) A-9 (230 m) A-11 (336 m) Average (231 m) With cuttings 2.6 16.4 48 9.6 23.8 17.7 19.7 Other surface 1.5 3.3 10.1 2.2 12 17.1 7.7 Downhole 7.6 10.8 46.4 0 0 0 10.8 Well displacements 5.6 28.3 12.8 24.3 11 15.7 16.3 Tripping 6.5 7.2 6.3 3.6 1.6 2.8 4.7 TOTAL 23.8 66 123.6 39.7 48.4 53.3 59.1
- 27. Huldra – Production of recoverable gas and condensate reserves since 2001 (NPD data) Plateau production from first 3 wells - 10 MM m 3 gas /day - 30,000 bbl/day condensate 80% of hydrocarbon reserves produced by Year 6
- 28. Gas production from Tune and Huldra fields drilled and completed with K/Cs formate brine 90% recovery of gas reserves (16-18 billion m 3 ) produced in 7 to 8 years Source : Norwegian Petroleum Directorate- Fact Pages - November 2009
- 29. Condensate production from Tune and Huldra fields drilled and completed with K/Cs formate brine 90% recovery of condensate reserves (3-5 million m 3 ) produced in 5 to 7 years Source : Norwegian Petroleum Directorate- Fact Pages - November 2009
- 30. Offshore Norway, 190 m water depth Gas condensate field, 775 bar 13 wells to date – 8 O/B, 5 in MPD BHST: 311 o F (155 o C) TVD : 13,120 ft (4,000 m) Fluid density: 16.8 ppg (SG 2.02) for O/B 914 -1,910 ft (279-583 m) x 8 1 /2” reservoir sections Hole angle : 20-40 o 100 mD sandstone, long interbedded shale and coal sequences 6 wells completed in open hole : 300-micron single wire-wrapped screens. Remainder cased Seven years of cesium formate brine use as combined drill-in and completion fluid in Kvitebjoern field, 2004 -present
- 31. A few of the highlights from Kvitebjoern Fastest HPHT well completion in the North Sea “ The target well PI was 51,000 Sm 3 /day/bar This target would have had a skin of 7” “ A skin of 0 would have given a PI of 100,000” “ THE WELL A-04 GAVE A PI OF 90,000 Sm 3 /day/bar (ANOTHER FANTASTIC PI)” Operator comments after well testing (Q3 2004 ) The Well PI was almost double the target Kvitebjoern well Completion time (days) A-4 17.5 A-5 17.8 A-15 14.8 A-10 15.9 A-6 12.7 *
- 32. Economic benefits from the use of cesium formate brine in HPHT gas field developments Improved HPHT well control and safety No well control incidents in 28 HPHT drilling and completion ops over 10 years (maybe 800 days in HPHT high-angle open hole ?) Factors contributing to improved well security and safety: - Elimination of barite and its sagging problems - Elimination of oil and its gas solubility problem - Low solids brine Low ECD* and swab pressures - Inhibition of hydrates - Ready/rapid surface detection of well influx - No hazardous zinc bromide ! * ECD in Huldra, Kvitebjoern and Kristin wells : 0.33-0.50 ppg (SG 0.04-0.06)
- 33. Economic benefits from the use of cesium formate brine in HPHT gas field developments Improved well performance and recovery of reserves “ High production rates with low skin” * “ We selected cesium formate to minimise well control problems and maximise well productivity”* * Quotes by Statoil relating to Kvitebjoern wells (SPE 105733)
- 34. Economic benefits from use of cesium formate brine in HPHT gas field developments Faster completions - Drill-in and completing with cesium formate allows open hole completion with screens - Clean well bores mean no tool/seal failures or blocked screens - Completion time 50% lower than wells drilled with OBM Time saved per well: 25 days Quote by operator: “ fastest HPHT completion operation ever performed in North Sea (12.7 days)”
- 35. Economic benefits from use of cesium formate brine in deep gas field developments Operational efficiencies Lower NPT Lower costs No differential sticking No well bore instability* Pipe and casing running speeds are fast Mud conditioning and flow-check times are short Displacements simplified, sometimes eliminated Formate drilling fluid = formate completion fluid * Quote by operator : “ No washouts were experienced in any of the wells during drilling through long sections of interbedded shales in the Kvitebjoern reservoir (50/50 shale and sand ) with cesium/potassium formate fluid” Flow check fingerprint for a Huldra well Duration of flow back (minutes) Fluid Gain (bbl) 30 0.8 15 0.56 20 0.44 30 0.56
- 36. Cesium formate drilling fluids – some important features that impact on nuclear logging The extreme photoelectric effect of the cesium formate filtrate provides the log interpreter with valuable information regarding invasion, thus porosity and net reservoir.
- 37. Cesium formate drilling fluids – some important features that impact on nuclear logging Filtrate is mobile : gravity segregation over time and replacement by hydrocarbon phases Effect of invasion and time lapse : From left to right, formation density (ROBB), medium deep resistivity (P16) and deep resistivity (P40). LWD drill pass data represented by red curves and ream pass represented by black curves.
- 38. Logged Pef and observation of filtrate movement can be used to define permeable sands in gas reservoirs (SPE 105733) “ Using the photoelectric factor and bulk density data, combined with resistivity measurements from both the LWD drill pass and the ream pass, produces a very reliable and consistent net reservoir definition” Berg et al , SPE 105773 Log responses from drill-pass (P16_1) and ream-pass (P16_2) provide a powerful technique for defining permeable intervals (SAND_FLAG ).
- 39. Economic benefits from the use of cesium formate brine in HPHT gas field developments Good reservoir definition High density filtrate and no barite Filtrate Pe up to 259 barns/electron Unique Cs feature - makes filtrate invasion highly visible against formation Pe of 2-3 b/e Ideal for defining permeable sands Consistent and reliable net reservoir definition from LWD “ Using photoelectric factor and bulk density data, combined with resistivity measurements from both the LWD drill pass and the ream pass, produces a very reliable and consistent net reservoir definition .” ( SPE 105733)
- 40. Economic benefits from the use of cesium formate brine in HPHT gas field developments Good reservoir definition Highly conductive fluid Clear resistivity images Information provided: - structural dip - depositional environment - geological correlations
- 41. Summary 10 years of drilling with cesium formate brine has shown that it can improve the economics of HPHT gas field developments by: Enabling long high-angle well constructions completed in open hole with screens Making the well construction process faster and easier Improving well/operational safety and reducing risk Delivering unimpaired wells with high production rates Enhancing reservoir definition