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5 5 deepwater overview

Introduction to Deepwater
Drilling Technology

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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
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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)

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Deepwater Basins in 2000

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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



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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
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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 7 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

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Projected Deepwater
Expenditure Per Region
North America

8000

Middle East

$ million .

7000

Latin America

6000

Europe

5000

Australasia
Asia

4000

Africa

3000
2000
1000
0
1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Courtesy of World Deepwater Report 2000-2004, John Westwood Associates & Infield Systems Ltd

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Deepwater Activity Forecast

Courtesy of Oilfield Review

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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 !

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Technical Challenges!











Water / depth
Pressure / temperatures
Geo-science demands
Operating environment
Formation characteristics and
operating conditions (limits)
Wellbore stability
Wellbore quality
People, multidisciplinary skill set.
Operating procedures, guidelines
Loss, risk, performance management

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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

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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)
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Sea Ttemperature Profile

Temp Gradient in sea water
Treturn

Tinjection

Temperature
drop in drill pipe

Temperature
drop in annulus
Tcasing

Geothermal Profile

Tannulus

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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)
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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

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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.)
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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.

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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
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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

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Deepwater Well Testing
• Use of Sen Tree 3 (E-H control)
• Use of Sen Tree 7 (MUX) for large bore
• Downhole DST (no hydrocarbons at
surface)
• Only samples required? Cost effective
solution is low-shock MDT sampler (save
costly DST)

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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

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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 …..
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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)
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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

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