Tech Focus Deltide

Dual String Casing Milling Challenges for the North Sea

CARY BOWMAN APRIL 2013

Deltide Energy Services 

60 + years operating history in GoM

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2012 began operations in North Sea, partnering with Halliburton

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ISO 9001 compliant

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Originator/Inventor of – Fit for Purpose applications – Best in Class tooling and equipment

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Focused provider of niche services in casing severing and section milling, including multi-string milling 2

Multiple String Section Milling Sustained Casing Pressure and Bubbling Wells

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Inflatable Packer

Multi-String Section Milling - Challenges 

Un-cemented casing strings

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Casing centralizers

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Severe casing eccentricity

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Corroded or damaged casing

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Debris left in the well

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Pressures and hydraulics

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Centralization & Stabilization Affecting - Milling times, Blade life, AND footage (collectively “ROP”) VARIABLE – WELL SPECIFIC

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Multi-String Section Milling - Challenges

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Dual String Section Milling – Proven success  Technology /Experience – Over 6 years milling multi-string windows – 150+ multiple string milled windows to date – K-55 to HCP-125 casings

 Design / Blade improvements – Optimum performance – Longevity / Increased footage / ROP – Customizable

 Bi-directional Section Milling  Simultaneous Under-reaming while Section Milling

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Dual String Section Milling – North Sea Challenges Transfer of Technology

Well Casing Profiles  7 5/8” inside 9 5/8” (13.5” UR) 

9 5/8” inside 13 3/8” (18.5” UR)

Desired Milling Windows  +100’ inner string

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~ 85’ dual string window

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~ 66’ under ream to formation

Dual String Section Milling – North Sea Challenges Transfer of Technology Gulf of Mexico

North Sea

20’ to 30’

100’+

Milling Depths

< 1000’

2000’ to 10,000’

Hole angle

straight

> 65°

20k to 50k

>200K

Shallow - stiff assemblies

Deep - tapered drill string

Shallow - Rat Hole

Deep - Mill swarf management program

N/A

Loss of hole issues

Accepted Practice

Developing

Window Lengths

Daily Spread Costs

Work string dynamics – WOB and Stabilization Hydraulics

Formation Issues Performance Benchmarks

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North Sea Dual String Section Milling – Results to Date 

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First Dual String SM – 7 5/8” x 9 5/8” (13.5” UR) – 18º Deviation – Cemented and Abandoned Second Dual String SM – 7 5/8” x 9 5/8” (13.5” UR) – 16º Deviation – Currently ongoing

Milling 9-5/8“ from inside 7-5/8"

12 10 8 # of Milling Trips

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Operational Challenges – Smaller casing, smaller tooling – Tool and blade longevity – Minimize trips – Customize blades to achieve performance objectives

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Under-reaming while milling successful

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9-5/8” x 13-3/8” (18.5”) upcoming

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Acknowledgements