CNRL Presentation Feb 19

Thermal Wells: Abandonment & Remediation

Will Butler, P.EngTeam Lead - Engineering

Topics Brief overview of Directives, Regulations & IRP’s

Common Compliance Issues

Well Case Studies

4 wells located within thermal development area

1 well located outside thermal development area

1 with a liquid SCVF

1 with a potential gas migration

FundamentalsUnderstand current directives, regulations and IRP’s

AER Directive 009 – Minimum Casing Cementing Requirements Sec. 3.2 – Surface Casing

Sec. 3.3 – Production, Intermediate & Liner Casing

Sec. 4.2 – Thermal Cement

Sec. 5 – Method of Determining Required Cement Top

AER Directive 010 – Minimum Casing Design Requirements


AER Directive 020 – Well Abandonment Sec. 4.2 – Open-Hole Abandonment in Penetrated Oil Sands Zones

Sec. 4.6 – Oil Sands Evaluation Wells & Test Hole Wells

Sec. 5.4 – Cased Wells Penetrating Oil Sands Zones

Sec. 5.5 – Groundwater Protection

Sec. 7.0 – Testing & Inspection Requirements for GM & SCVF

ID 2003-01 Sec. 2 – SCVF/GM Testing, Reporting & Repair Requirements

Sec. 3 – Casing Failure Reporting & Requirements


IRP Volume 03 – In Situ Heavy Oil Operations

Required assessment of offset, abandoned/vintage well & neighbouring operator wells for compatibility to thermal operations:

Within 300m of SAGD & 1000m of CSS developments.

Wells which operator deems a risk factor or by request of landowner

Describes mechanical considerations due to thermal & pressure cycling:

Casing loads (stress & strain)

Corrosion considerations

Coupling suitability


IRP Volume 03 – In Situ Heavy Oil Operations

Describes cementing considerations:

Hydraulic Isolation (Porous & Groundwater)

Caprock/primary seal integrity

Cement type & integrity evaluation

Strength retrogression at operating temperature

Common Compliance Issues Well is not properly isolated with thermal cement across oil sands

formations

• Primary cement

• Wellbore cement plugs (openhole or cased)

Existing primary cement integrity is unknown or in question

• Unsuitable for expected temperature & pressure cycling?

• Temperature degradation of non-thermal cement?

• AER generally requires a CBL run before further approval of operations

Casing failure/corrosion issues present

Common Compliance Issues Abandonment was not to current D020 standards

Casing/connections not suitable for potential thermal and pressure cycling stresses

• Non-premium connections

• Mechanical properties deemed unsuitable by engineering assessment or physical testing

SCVF/GM exists• Liquid SCVF’s are usually “severe” due to high salinities & trace hydrocarbons

• Gas SCVF’s are usually “non-severe” due to flow rate less than 300 m3/d

• GM’s are rare, but observed from time to time

Case 1: Background Vertical well east of Fort McMurray

Rig Release: February 1981

Zonally abandoned and well cut and capped

Compliant in 1981

Currently within 100m of a proposed steam injection well

Max. temperature = 235oC

Max. Pressure = 4MPa

Case 1: Compliance ConsiderationsSurface cement plug

Prod. casing/connections are inadequate for expected temperatures

Cemented with Class G with no returns to surface

BP capped with Class G

Non-routine waiver submitted to leave wellbore as is and operate as an observation well

Approval rejected, well must be made thermally compliant due to steam chamber proximity

Case 1: OperationsStep 1: Drill out surface plug & BP


Step 2: Run CBL/VDL to verify cement top and integrity across non-

thermal formations to 109mKB

TOC 25m above sfc. csg shoe

Cement bond is good throughout


Step 2: Run CBL/VDL to verify cement top and integrity across non-thermal formations to 109mKB

Step 3: Section mill & under-ream casing & cement from 109mKB to below shoe @ 298mKB

AER Oilsands interval requiring thermal isolation


Step 2: Run CBL/VDL to verify cement top and integrity across non-

thermal formations to 109mKB

Step 3: Section mill & under-ream casing & cement from 109mKB to

prod. csg. Shoe @ 298mKB

Step 4: Spot continuous thermal cement plug from TD to min. 15m

above sfc. csg. shoe

Estimated Cost = $450,000.00

Case 2: Background Vertical well NW of Cold Lake

Rig Release: March 1965

Perfs just below the Grand Rapids formation top

Openhole section abandoned in 1965

Grand Rapids perfs abandoned in 2001

Well within 200m of proposed steam chamber targeting the Clearwater Group

Max. Temperature = 180oC

Case 2: Compliance ConsiderationsCasing cemented to surface with thermal cement with good returns to surface (verified by CBL)

Bridge plug set within 15m of Grand Rapids perfs & capped with 10m of thermal cement

Thermal cement plug set in OH section and across shoe from 434.0-372.2mKB in 2001

Non-thermal cement plug set in OH section from TD to 434.0mKB in 1965

Case 2: Operations AER non-routine waiver to leave wellbore “as

is”, approved on the grounds that:

1. Above 434.0mKB, well is essentially thermally compliant

2. Clearwater formation (target zone) is isolated with thermal cement and well above non-thermal cement plug from TD to 434.0mKB

No remedial operations required

Cut & cap well

Estimated cost = $8,000.00

Case 3: Background Vertical well North of Cold Lake

Rig Release: November 1985

Corehole well with no surface casing

Cement plugs placed before rig release in 1985.

Well is located within 50m of a proposed steam chamber targeting the Clearwater formation

Case 3: Compliance ConsiderationsThermal cement plug top is located 17.4m above Grand Rapids formation top

Formations above the Mannville Group require isolation

• Joli Fou

• Viking

Case 3: Operations AER non-routine waiver to leave

wellbore “as is”, approved on the grounds that:

1. Clearwater formation (target zone) is isolated with thermal cement

2. OH logs indicate absence of porosity across the Joli Fou & Viking formations

3. Difficulty associated with attempting to drill out surface OH cement plug

No remedial operations required

Estimated cost = $0.00

Case 4: Background Vertical well south of Fort McMurray

Rig Release: January 2000

Perfs @ McMurray, Wabiskaw & Clearwater formations

Well is within proposed steam chamber targeting the McMurray

Client concerned casing may part due to thermal stress created by possible steam chamber contact

Case 4: Compliance Considerations

Prod. casing/connections are inadequate

Casing cemented to surface with non-thermal thixotropic cement with good returns to surface (verified by CBL)

Non-routine waiver submitted to AER with an engineering assessment of casing stress/strain and cement integrity from expected steam chamber operations

AER approved the following operations

Case 4: OperationsStep 1: Remove 38.1mm coil tubing

strings and retrieve Packer @ 407mKB



Step 2: Retrieve WR plug @ 416mKB




Step 3: Chemically cut casing in the McMurray formation

@ 460mKB





@ 460mKB

Step 4: Run & set BP @ 459mKB





@ 460mKB

Step 4: Run & set BP @ 459mKB

Step 5: Spot continuous thermal cement plug from TD to min. 15m

above sfc. csg. shoe

Estimated Cost = $90,000.00

Case 5: Background Vertical well north of Red Earth Creek


Openhole section penetrates the Bluesky Formation

Well is not located within, or near, a proposed thermal development

Very little bitumen present in formations in this area

Case 5: Compliance ConsiderationsProd. casing/connections inadequate?

Casing cemented to surface with Class G cement with good returns to surface (verified by CBL)

AER non-routine procedure was approved based on the following:

1. Very little to no bitumen in formations from OH logs

2. Unlikelihood of a thermal project developing in the area

Condition: Should thermal operations develop within vicinity of the well, it must be remediated to a state that AER deems “thermally compatible”

Case 5: OperationsStep 1: Retrieve 60.3mm tubing

Case 5: OperationsStep 1: Retrieve 60.3mm tubing

Step 2: Spot continuous thermal cement plug from TD to surface


Case 6: Background Vertical well north of Cold Lake


Well has an existing liquid SCVF issue (~500ml/day)

From offset activity, likely source from the 2nd White Specks

Two cement squeeze attempts at 2WS were unsuccessful

Previous logs indicate excellent caprock at the surface casing shoe

Case 6: Compliance Considerations Casing designed with premium connections

Production casing cemented to surface with thermal cement (Verified with CBL)

Only 10m between squeezed abrasive slots and surface casing shoe with no caprock

2WS source is well above the Grand Rapids formation

Non-thermal cement may be used

Non-routine waiver submitted to AER to access caprock at surface casing shoe & perform remedial cement squeeze

AER approved the following operations:

Case 6: Operations Drill out cement plug to ~5m below surface

casing shoe


casing shoe

Perform six 120o Abrasive cuts from 172-174mKB

Establish feed rate into abrasive slots at a maximum of 3.1MPa (fracture gradient)


casing shoe

Perform six 120o Abrasive cuts from 172-174mKB

Spot a Non-thermal cement plug from 178mKB to surface

Squeeze cement to a maximum of 3.5MPa


Case 7: Background Vertical well east of Christina Lake


Well has an existing GM issue

Drilling reports indicated significant gas at the McMurray formation top

Confirmed by original OH & neutron logs

Review of nearby wells revealed a gas injector belonging to another operator

Injector was maintaining a gas cap in the Wabiskaw/McMurray formation

Case 7: Compliance Considerations Openhole cemented to surface with thermal

cement, but placement method is unknown

Balanced, staged, layered, etc.?

Openhole caliper log indicates significant wellbore deviation from McMurray formation to surface

Cement to formation bond is likely very poor

Proposed intervention interval is 50m above the Grand Rapids formation

Non-thermal cement may be used

High risk in attempting to drill out OH cement plug in order to target McMurray source

AER waiver required for well re-entry

Case 7: Operations Install new wellhead and SCVF assembly &

confirm if leak is a SCVF or GM



If possible, shut in injector well & allow stored gas to migrate & dissipate



If possible shut in injector well & allow stored gas to migrate & dissipate

Drill out cement in surface casing to 25m below the shoe





Under-ream a minimum of OH diameter (or greater) to within 1-2m of casing shoe





Under-ream a minimum of OH diameter (or greater) to within 1-2m of casing shoe

Spot continuous thixotropic or expanding cement blend from PBD to min. 15m above the sfc. csg shoe (no squeeze)


In Conclusion

Know and understand applicable regulations & IRP’s for oilsands & thermal development areas

Confirm status & condition of wells, including proximal & those of offset operators, near thermal development areas

300m from SAGD operations

1000m from CSS operations

Generally, a well is not thermally compliant unless all requirements in the directives are met

In Conclusion

Wells may receive AER approval to abandon with alternative methods, if an engineering assessment supports long term integrity of the well

Physical Testing

Numerical Analysis

Computer simulation of temperature & pressure effects

Historical case studies in comparable areas

Questions

CNRL Presentation Feb 19

Documents