5 5 deepwater overview

• Deepwater provinces - regional differences • Deepwater riser • Deepwater rigs and operations • High deepwater drilling costs and deepwater alternatives slim hole, dual mud gradient sy

Introduction to Deepwater

Drilling Technology

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

– 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)

Deepwater Basins in 2000

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

– Indonesia (confirmed-UNOCAL), Australia

– Israel, Egypt (exploration on-going)

– Plans in India, Pakistan, Tanzania

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

0 1000 2000 3000 4000 5000 6000 7000 8000

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

Projected Deepwater

Expenditure Per Region

Deepwater Activity Forecast

Courtesy of Oilfield Review

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

• Formation characteristics and

operating conditions (limits)

• Wellbore stability

• Wellbore quality

• People, multidisciplinary skill set.

• Operating procedures, guidelines

• Loss, risk, performance management

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

shut-in)

• 13-3/8” casing acting as surface casing

• Very low fracture gradients

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)

Temp Gradient in sea water

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

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

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

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.

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

EQUIPMENT & annular pressure while drilling

(APWD)

• Prevention: importance of pore pressure prediction

conditions are favorable in

deepwater for formation of

Deepwater Well Testing

• Use of Sen Tree 3 (E-H control)

• Use of Sen Tree 7 (MUX) for large bore

surface)

• Only samples required? Cost effective

solution is low-shock MDT sampler (save

costly DST)

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

Deepwater Rig & Operations

• Mooring/Station keeping capability

– 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

• High daily rate …

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)

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

PERSONNEL

Why is Deepwater So Special ?

• Seismic Acquisition and Interpretation

• Geology and Reservoir Characterization