Decision Risk Management
Review of Through-Tubing
Drilling Uptake on UKCS
C. Cranfield (DTI), L. Wickens
(AEAT), G. Maitland (LEA)
Outline
• Background
• Objectives
• Workshops
– Format
– Results
– Conclusions
– Recommendations
• Follow-up
Background
• OGITF in Sept. 1999 reported CTD and TTRD
– potentially important
– currently available
– not widely used on UKCS
– could significantly raise recovery
• However, in early-2000
– Lack of CTD and TTRD activity
• Why?
– DTI initiated a review to find out
No. of recent UK CTD wells, to mid-2000
Number of CTD wells drilled, as of mid-2000
6
5
Onshore (UB)
Offshore
4
3
2
1
0
1992
•
1993
1994
1995
1996
Widely used on-land;
Alaska, Oman
1997
1998
1999
2000
2001
•
Few UKCS CTD wells
•
More TTRD wells in 2000
Objectives
• Review situations in which TTD is viable on UKCS
• Understand decision-making factors
• Disseminate best-practices
• Raise awareness
• Hopefully stimulate TTD activity
Specialists: L. Wickens, AEA and G. Maitland, LEA
Format of Workshops
• Met with five operating companies
– February - July 2000
– Two majors with previous UKCS TTD experience
– Three intermediates
• Structured for open debate
– Drilling objectives network
– Mind map
– Ranking exercise
• CTD vs. TTRD
• Specific field situations
Drilling objectives network
Accelerate
production
Improve
NPV
Increase
reserves
Reduce
costs
Drilling objectives network
Accelerate
production
Improve
NPV
Drill new
wells
Conventional
sidetrack
Increase
reserves
Reduce
costs
Less
downtime
Faster
drilling
Drilling objectives network
Improve
NPV
Accelerate
production
Drill new
wells
Less
downtime
Conventional
sidetrack
Less
formation
damage
Increase
reserves
Reduce
costs
TTD
CTD
Faster
drilling
TTRD
Underbalanced
Mind map
IMPACT
WHY
Prolong field life
<1mmstb targets
3rd party satellites
SNS
Lower day-rate
Depleted reservoirs
Unswept reserves
ECONOMICS
Cost uncertainty
Needs to be cheaper
WHEN
CTD
ALTERNATIVES
Conv. sidetrack Casing drilling
TTRD
Hybrid rigs
WHAT’S NEEDED
Good pre-planning
Dedicated crews
Multiple wells
Bigger cranes
Lighter coil
Enabling technologies
Common alignment
Buy-in from management
Manpower resources
Sufficient confidence
Enough wells
WHERE
SNS
Idle rig
Concurrent ops
Ranking Results - CTD vs. TTRD
Drilling performance / Capex
Pressure transitions, UB
Pressure transitions, OB
Technical maturity
HSE
Well productivity
Lead time (topsides, wells)
Upfront Capex
Lithology selection
• Attributes from mind map were
ranked and weighted
• Neither option strongly favoured
– Depends on opportunities
• TTRD wells planned for 2000 and
2001
• Companies will monitor next 2-3
years
Balance of Forces
Company 1
Company 3
Company 4
-80%
-60%
-40%
-20%
CTD Favoured
0%
20%
40%
60%
80%
TTRD Favoured
Past TTD experiences
• Lack of success
– Stuck-pipe / hole collapse
• Swelling shales
– Cost over-runs
– Lack of continuity between jobs
– Equipment not fit-for-purpose
• Obstacles
– Insufficient crane capabilities
– Effect of low SNS pressures on cuttings transport
– Lack of well candidates
– Lack of SNS specialist vessel
• CTD problems provided learning opportunity
Current developments
• Light-weight coil
– Composite re-usable
– Titanium high-strength
• Reliable BHA’s
• Precise and reliable window-cutting
• Whip-stock
• Software
Could accelerate uptake of CTD and TTRD on UKCS
Recommendations
• Companies and service / technology providers:
– Joint-industry campaigns
– Collaborate on CTD technology, logistics, equipment
– Peer reviews, sharing of information
– Risk-reward arrangements
– Funding for R&D, specialist training
• DTI:
– Address negative perceptions of regulatory approval process
– Advocate collaboration in SNS, to develop specialist vessel
– Quantify benefits of UBD on UKCS
Need for Specialist Vessel
• UBD is required to drill low-pressure SNS formations
• SNS platforms do not have
– Drilling rig
– Pumping / fluid handling capacity
– Accommodation / space
• Solution would be mobile unit
– Operate alongside platform
– Move between operators
• Mobile unit also valuable for CNS / NNS
– Targeting small reservoirs, that deplete rapidly
– Providing concurrent drilling for platforms with own rigs
Conclusions
• CTD and TTRD considered potentially important, low cost
• Need to overcome associated difficulties
– Lack of continuous, integrated programmes
– Crane capacity, rig space
– Risk to mother-bore
– Up-front costs
– Lack of confidence
• Step-out distances, equipment, expertise
– Perceptions
• Aim to reduce CTD side-track from > £ 2.2 mm to < £ 1.0 mm
– Encouraging 2H 2000 results
• Under-balanced CTD of particular interest in SNS
Follow-up
• Workshops effective in sharing information
• ITF projects ongoing
• DTI
– Continual promotion and support of improved recovery
– PILOT initiative on undeveloped discoveries
– Participation in ITF coiled tubing UBD JIP
• Suggestions on regulatory approval process to:
[email protected]
01224 254066