5 5 deepwater overview

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Introduction to Deepwater Drilling Technology COPYRIGHT © 2002, All Rights Reserved Topics to be covered • • • • • What is deepwater drilling? Deepwater provinces - regional differences Deepwater riser Deepwater rigs and operations High deepwater drilling costs and deepwater alternatives slim hole, dual mud gradient systems • Evolving deepwater drilling technology – Deepwater field development concepts deep draft caisson vessel (DDCV-SPAR) vs TLP (tension leg platforms) • Challenges of deepwater technology Conclusions COPYRIGHT â 2002, All Rights Reserved Introduction • What is “Deepwater?” – This is an evolving notion – Presently considered to be water depth deeper than 1500 ft, ultra-deepwater meaning > 5000 ft of water • Where is deepwater drilling taking place? – Present water depth drilling record: 9111 ft (Brazil 2000); 6592 ft 1998; 5700 1982) – World water depth record for a producing well: 6080 ft (Roncador field, Brazil, 1999) COPYRIGHT © 2002, All Rights Reserved Deepwater Basins in 2000 COPYRIGHT © 2002, All Rights Reserved Deepwater Discoveries in the US Gulf of Mexico (Water depth > 1500 ft) • History: Jolliet (1722 ft, 1981), Tahoe (1500 ft, 1984), Auger (2864 ft, 1987), … • 112 deepwater discoveries at the end of 1999: 17 in 1999, 10 in 1998, 16 in 1997 COPYRIGHT © 2002, All Rights Reserved Deepwater Provinces • Brazil • Gulf of Mexico (GOM) • West Africa (Angola, Nigeria, Equatorial Guinea, Gabon) • Others – West of Shetland, Western Approaches, Norway – Trinidad (1 discovery) – Indonesia (confirmed-UNOCAL), Australia – Israel, Egypt (exploration on-going) – Plans in India, Pakistan, Tanzania COPYRIGHT © 2002, All Rights Reserved Differences Between the Deepwater Provinces Gulf of Mexico - Extremely high drilling cost - Shallow water flows - Very deep reservoirs (multiple casing strings, ECD problems, odd casing/hole sizes) - Sub-salt drilling - Slender well concept applicable - Loop eddy currents, hurricanes - Direct application of dual gradient drilling Angola - Shorter well duration - Shallow reservoirs BML (leading to near horizontal /high reach wells, shallow kick-offs in unconsolidated formations) - well reach limited by ECD problems (impact on development scheme, i.e subsea vs surfaceWHP) - Slender well concept applicable COPYRIGHT © 2002, All Rights Reserved Projected Deepwater Expenditure Per Region North America 8000 Middle East $ million 7000 Latin America 6000 Europe 5000 Australasia Asia 4000 Africa 3000 2000 1000 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Courtesy of World Deepwater Report 2000-2004, John Westwood Associates & Infield Systems Ltd COPYRIGHT © 2002, All Rights Reserved Deepwater Activity Forecast Courtesy of Oilfield Review COPYRIGHT © 2002, All Rights Reserved Business Challenges! • New ventures and exposure to organization • 1st deepwater licenses for operator, drilling contractor & service company personnel • Water depths > 150m  3000 m • Remote and demanding environment(s) • New process and technology requirements • New skills sets for personnel • How to succeed first time ! COPYRIGHT © 2002, All Rights Reserved Unconsolidated Shallow Sediments • 30” pipe is jetted in (with drill-ahead tool) • 30” pipe is structural, not conductor Usually 80 to 100 m long • 20” pipe is conductor, not surface casing It is run in open water (26” hole drilled riserless) • On mobile offshore drilling units (MODU), BOPs and marine risers are run on top, but no use of BOPs in 17-1/2” hole (No shutin) • 13-3/8” casing acting as surface casing • Very low fracture gradients COPYRIGHT © 2002, All Rights Reserved Narrow Margin Between Fracture and Pore Pressure • • • Well control issue: reduced kick tolerance Leads to multiple casing strings (especially with deep below mud level (BML) reservoirs) Solutions: – Very close monitoring of mud weight (equivalent circulating density (ECD) management) – Use of abnormal pressure while drilling (APWD) tools to know ECD & kick detection – Requirement for pore pressure prediction – Highly sensitive kick detection equipment – Procedures (breaking mud gel) COPYRIGHT © 2002, All Rights Reserved Sea Ttemperature Profile Temp Gradient in sea water Treturn Tinjection Temperature drop in drill pipe Temperature drop in annulus Tcasing Geothermal Profile Tannulus COPYRIGHT â 2002, All Rights Reserved Drilling Fluids Low fracture gradients (hole cleaning, ECD, lost circulation) • Low temperatures (high viscosity, gel, impact on ECD, and swab and surge) • Key issue: very close mud weight monitoring • Solutions – ECD control solutions: by design & use of bi-center bits – Prevention: APWD, virtual hydraulics (ECD modeling accounting for temperature, solids, surge) – Procedures: limitation of tripping speed, breaking mud gel while tipping • Wellbore stability: inherent problem • Possibility of gas hydrates (gas, water, T, P, mud type inhibitors prediction software) COPYRIGHT © 2002, All Rights Reserved Deepwater Cementing • Possible lost circulation due to low fracture gradients: extremely ECD critical • Low temperature affecting the shallow casing strings (proprietary software for temperature prediction) • Light weight slurry with adequate compressive strength and acceptable setting time: solution = special/proprietary cement systems • ECD monitoring procedures for surge, circulation to break gel, and controlled slurry displacement COPYRIGHT © 2002, All Rights Reserved Deepwater Well Control Specifics • Low fracture gradients, low temperature (high swab and surge pressures) • No riser margin • Very low kick tolerance • High choke line friction losses, low MAASP • Hydrates • Trapped gas in the BOPs, handling gas in riser (OBM, …) • Training of personnel essential (Drilling Co & Oil Co.) COPYRIGHT © 2002, All Rights Reserved Riser Margin in Deepwater Assuming a 12 ppg equivalent pore pressure at 7000 ft drilling depth –In 1000 ft of water: MW with riser margin = 12.6 ppg –In 2000 ft of water: MW with riser margin = 13.4 ppg –In 3000 ft of water: MW with riser margin = 14.6 ppg • Riser margin: non-existing in deepwater • No real double barrier with a SWHP or a surface BOP COPYRIGHT © 2002, All Rights Reserved Low Kick Tolerance in Deepwater Assuming TD = 13000 ft, shoe @ 10000 ft MW = 13.0 ppg, pore pressure = 13.5 ppg eq –In 1000 ft of water: kick tolerance = 180 bbls –In 2000 ft of water: kick tolerance = 70 bbls –In 3000 ft of water: kick tolerance < 10 bbls • Kick circulated out likely to cause underground blowout & cratering • HIGHLY SENSITIVE KICK DETECTION EQUIPMENT & annular pressure while drilling (APWD) • Prevention: importance of pore pressure prediction COPYRIGHT © 2002, All Rights Reserved Hydrates Causes Prevention • High pressure • Pressure reduction (use the lowest safe mud weight) • Presence of natural gas and water • Low temperature • Primary well control, i.e no gas in wellbore conditions are favorable in • Increase temperature, or deepwater for formation of change fluid type or use gas inhibitors in the drilling fluid COPYRIGHT © 2002, All Rights Reserved Deepwater Well Testing • Use of Sen Tree (E-H control) • Use of Sen Tree (MUX) for large bore • Downhole DST (no hydrocarbons at surface) • Only samples required? Cost effective solution is low-shock MDT sampler (save costly DST) COPYRIGHT © 2002, All Rights Reserved Deepwater Risers • Marine riser (mobile offshore drilling unit (MODU)): 21” OD, 19” OD • Drilling risers - tension leg platform (TLP), deep draft caisson vessel (DDCV): several options (LP, HP, inner riser) • Riser wear monitoring is essential COPYRIGHT © 2002, All Rights Reserved Deepwater Rig & Operations • Mooring/Station keeping capability • BOPs – Enhanced BOP control system (MUX) – Larger subsea accumulator capacity • Riser with buoyancy material, high tensioning capacity • Much larger variable deck load (>5000 MT) – Extra mud and riser storage required • Guideliness system, ROV • High daily rate … COPYRIGHT © 2002, All Rights Reserved High Deepwater Drilling Costs • Daily spread rate of a deepwater rig: $300 K minimum (primarily due to rig cost and rig market) • How to reduce costs? • Saving on drilling time (parallel operations can lead to 20 to 35% savings) • Less wells (multilaterals, horizontals, optimized well placements, etc ) • Alternative rigs (use of 2nd and 3rd generation semi-subs • Alternative well design (slender well) • Alternative drilling concept (dual gradient drilling) COPYRIGHT â 2002, All Rights Reserved Environmental Challenges Existing guidelines designed for onshore, swamps, and shallow offshore activities must be modified • New environmental concerns such as effect of deep drilling activities on aquatic life and spill handling must be addressed • Monitoring operations and activities in deep terrain, turbulence, and adverse weather conditions • Needs precision equipment, MANPOWER, & SKILLED PERSONNEL COPYRIGHT © 2002, All Rights Reserved Summary Why is Deepwater So Special ? • • • • • • • • Seismic Acquisition and Interpretation Geology and Reservoir Characterization Operating Environment Drilling Equipment and Techniques Completion Techniques Production Technology Flow Assurance High Cost COPYRIGHT © 2002, All Rights Reserved ... covered • • • • • What is deepwater drilling? Deepwater provinces - regional differences Deepwater riser Deepwater rigs and operations High deepwater drilling costs and deepwater alternatives slim... systems • Evolving deepwater drilling technology – Deepwater field development concepts deep draft caisson vessel (DDCV-SPAR) vs TLP (tension leg platforms) • Challenges of deepwater technology... Introduction • What is Deepwater? ” – This is an evolving notion – Presently considered to be water depth deeper than 1500 ft, ultra -deepwater meaning > 5000 ft of water • Where is deepwater drilling
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