The 2009 Issue of the The 2009 Issue of the

Oil & Gas UK Guidelines for the Oil & Gas UK Guidelines for the

Suspension and Abandonment of WellsSuspension and Abandonment of Wells

By Jules Schoenmakers,Shell EP Europe on behalf of

Oil & Gas UK Decommissioning Work Group 4b

SPE Well Abandonment 2009 Conference

30th June 2009, Aberdeen Exhibition and Conference Centre

• Jules Schoenmakers (Shell), Workgroup Chair

• Colin McDonald Smith, Phil Keeble (BP)

• Jean Marie Prieur, Peter Irvine (ConocoPhillips UK Ltd)

• Max Baumert, Richard Cutt (ExxonMobil International Ltd)

• Iain Sutherland, Giancarlo Pia (Talisman Energy (UK) Ltd)

• Garry Skelly (Sigma Wellservice Ltd)

• Donald Dobson (Health and Safety Executive)

• David Soden, Francois Rodot, Michel Bouillet (Total E&P UK)

• Frank Calder, Bob Beagrie (Schlumberger UK)

• Colin Wight (Halliburton UK)

• Steve Kirby (Sasok Ltd), Technical Author

Oil & Gas UK Workgroup 4b membersOil & Gas UK Workgroup 4b members

The contributions of the members and numerous external review parties are very much acknowledged.

• Guidelines assist compliance with the UK Offshore Installations and Wells Design and Construction Regulations, DCR 13, 15 and 16.

• DCR requires Operators to prevent, on a permanent basis, escape of fluids from the well.

• The Guidelines provide minimum criteria to ensure isolation of formation fluids both within the wellbore and from surface or seabed.

• It is accepted that reducing risk to As Low As Reasonably Practicable (ALARP), as required by Regulations, can be demonstrated by best practice.

• Operators expected to develop ‘in-house rules’ for their own operations.

The context of the GuidelinesThe context of the Guidelines

Key changes to GuidelinesKey changes to Guidelines

� Improved structure, streamlined & improved graphics

� Barrier principle and best practices highlighted

� Combination barrier introduced

� Annulus cement requirements clarified

� Liner lap, Cut casing requirements clarified

� Verification: Pressure testing in relation to a leak path below the cement.

� Established list of data for abandonment design

� Excluded Carbon Dioxide sequestration issues since experience is too sparse to define Guidelines.

� Declined to define guidelines for surface plugs, fluid injection, NORM treatment , explosives, well construction.

Permanent Abandonment Barrier schematicPermanent Abandonment Barrier schematic““Restoring the Cap RockRestoring the Cap Rock””

Barrier Elements

Height of 500ft MD, containing at least 100ft MD of Good Cement.

Plug Depth determined by formation (impermeability and strength) and primary cementation

Best Practices

Pipe stand-off

Good bond, clean surfaces, water wet

Support to prevent cement movement, slumping and gas migration while setting

Sealing Abandonment plug

Casings, tubing embedded in cement

Sealing primary cementations

Formation:Impermeable &adequate strength to contain future pressures

Tubing sealed with cement, in cement

Barrier Elements

Height of 500ft MD, containing at least 100ft MD of Good Cement.

Plug Depth determined by formation (impermeability and strength) and primary cementation

Best Practices

Pipe stand-off

Good bond, clean surfaces, water wet

Support to prevent cement movement, slumping and gas migration while setting

Sealing Abandonment plug

Casings, tubing embedded in cement

Sealing primary cementations

Formation:Impermeable &adequate strength to contain future pressures

Tubing sealed with cement, in cement

Need for cement plug support Need for cement plug support

Thin mud Thick mud Vertical hole (helix)

Mud rheology typically cannot support a cement slurry with significant density

difference; moving and contaminated cement will not provide a proper barrier

Slurry

SlumpingResults in

poor plug

Materials for Permanent barriersMaterials for Permanent barriers

� Very low permeability

� Long term integrity

� Non-shrinking� Ductile, not brittle

� Able to bond to casing or formation� Resistant to downhole fluids and gasses,

e.g. CO2, H2S

Cement is accepted as the prime material, but does not preclude others.

Materials in packers, bridge plugs, electrical cables, hydraulic lines are not acceptable as permanent barrier.

Minimum number of barriers requiredMinimum number of barriers required

One permanent barrier above a distinct permeable formation, as a minimum.

Two barriers if a permeable formation is - overpressured, or

- hydrocarbon bearing. Placement of two barriers may be combined; next

slide.

Open-hole needs barrier across the last shoe,

and open-hole barriers if shoe strength inadequate

Dual or Combination barriers, Cased holeDual or Combination barriers, Cased hole

Dual Barrier Solution

Plug should each contain >100ft of Good Cement. Each

typically 500ft long.

Annulus should

contain >100ft Good Cement opposite each internal plug.

Combination Barrier Solution

Plug should contain

>200ft of Good Cement. Typically 800ft long.

Annulus should contain

>200ft Good Cement opposite the internal plug

Figure 3 Comparison of Length of Dual or Combination Barriers

Dual Barrier Solution

Plug should each contain >100ft of Good Cement. Each

typically 500ft long.

Annulus should

contain >100ft Good Cement opposite each internal plug.

Combination Barrier Solution

Plug should contain

>200ft of Good Cement. Typically 800ft long.

Annulus should contain

>200ft Good Cement opposite the internal plug

Figure 3 Comparison of Length of Dual or Combination Barriers

>1000 ft if not logged

>1000 ft if not logged

Strengths and WeaknessesStrengths and Weaknesses

More operational & safety risk

Higher costIf plug fails, more remedial work

1st plug can affect the placement of

the 2nd (thru-tbg case stringers)

Higher risk of swabbing in small hole

(stinger set plug)

Smaller volumes, higher risk of

contamination

Higher risk of slumping and/or losses

WeaknessesWeaknesses

If plug fails less remedial workLower cost

More flexibility with positioningLower contamination, larger volume

1st plug can provide support for 2ndMore good cement in plug

Redundancy, independence

(although errors can be reproduced)

Reduced operational & safety risk

StrengthsStrengths

Two distinct barriersTwo distinct barriersCombination barrierCombination barrier

Open hole abandonmentOpen hole abandonment

Primary Barrier to Zone A, if Potential Internal Pressure exceeds

shoe fracture pressure.

Minimum100ft Good Cement,

typically 500ft MD

Figure 4A Example Open Hole Permanent Barriers

(If Potential Internal Pressure exceeds the casing shoe fracture pressure)

Zone A Zone A

SecondaryPermanent

Barrier to Zone A required

to fully seal the open hole

section.

Minimum 100ft Good

Cement, typically 500ft MD

Primary Barrier to Zone A, if Potential Internal Pressure exceeds

shoe fracture pressure.

Minimum100ft Good Cement,

typically 500ft MD

Figure 4A Example Open Hole Permanent Barriers

(If Potential Internal Pressure exceeds the casing shoe fracture pressure)

Zone A Zone AZone A Zone A

SecondaryPermanent

Barrier to Zone A required

to fully seal the open hole

section.

Minimum 100ft Good

Cement, typically 500ft MD

Primary Barrier to Zone A

At least 100ft MD of Good Cement into casing shoe, typically 500ft MD

Secondary Barrier to Zone AAt least 100ft MD of Good Cement into casing shoe, typically 500ft MD Single Barrier to Zone A

Minimum 200ft of Good Cement into casing shoe, typically 800ft MD

Dual Barrier SolutionCombination Barrier Solution

Figure 4B Example Open Hole Permanent Barriers

(IfPotential Internal Pressure does notexceed the casing shoe fracture pressure)

Zone A Zone A

Primary Barrier to Zone A

At least 100ft MD of Good Cement into casing shoe, typically 500ft MD

Secondary Barrier to Zone AAt least 100ft MD of Good Cement into casing shoe, typically 500ft MD Single Barrier to Zone A

Minimum 200ft of Good Cement into casing shoe, typically 800ft MD

Dual Barrier SolutionCombination Barrier Solution

Figure 4B Example Open Hole Permanent Barriers

(IfPotential Internal Pressure does notexceed the casing shoe fracture pressure)

Zone A Zone AZone A Zone A

Weak zone

Verification of permanent barriersVerification of permanent barriers

• Verification requirements are highly dependent on individual well and job design, but any permanent barrier should be verified forrequired depth and sealing capability.

• Methods: Slurry strength development, job records, tagging, weight testing, pressure testing, inflow testing.

• Tagging and pressure testing is the standard approach. Test pressure at least 500 psi over injection pressure below barrier, however without damage to casing or primary cementation.

• No pressure test is required if cement plug placed on a tagged and pressure-tested mechanical plug or on a cement plug, provided no job anomalies.

• Annulus cement: log, original job records, absence of sustainedcasing pressure, initial formation strength test

DocumentationDocumentation

• Statutory Notifications DECC, HSE, DEAL, Hydrographic Office, Oil & Gas UK, Kingfisher

• Record keeping Job records, verification, status diagrams, wellheads, Upload toCDA database

Final remarksFinal remarks

• An effective and efficient well abandonment starts at a

sound well design (e.g. casing setting depths, top of cements, packer setting depth, control lines, no annulus

top-ups, overburden gas coverage, etc)

• Next update of the Guidelines scheduled for 2012. Workgroup will work a number of long-lead issues in the

mean time.

Thank you for your attention