Casing in WCSB Well Construction: Steel Pipe Grades, Casing String Design, Burst and Collapse Ratings, Cementing, and AER Well Integrity Requirements for Cardium, Viking, and Montney Wells

Key Takeaways

• API casing grade and weight selection for WCSB Cardium, Viking, Montney, and Duvernay well programs based on burst, collapse, and tension triaxial load analysis using wellbore pressure profiles and geomechanical parameters: Casing design in WCSB wells begins with the expected wellbore pressure profile: maximum internal pressure (burst load) during a worst-case influx or stimulation, maximum external pressure (collapse load) from formation pressure on evacuated casing, and axial tension from the string weight and cementing or completion operations. The minimum required casing wall thickness and grade is selected to provide a safety factor above the burst pressure (typically 1.0-1.1 on API rated burst for WCSB production casing), collapse pressure (safety factor 1.0-1.1 on API rated collapse for production casing in typical WCSB formations), and tension (safety factor 1.6-2.0 on body yield for WCSB surface and intermediate casing accounting for dynamic loads during running and cementing). For WCSB Montney horizontal wells (production casing in 5-1/2 inch, 17 lb/ft wall thickness, L-80 grade): burst rating 53.8 MPa; typical WCSB Montney stimulation maximum wellhead pressure 55-70 MPa requires upgrading to P-110 grade (burst rating 75.4 MPa) or adding a heavier wall 20 lb/ft weight to achieve adequate burst safety factor for multistage fracturing operations where wellhead treating pressure can approach 80 MPa in deep northeastern BC Montney wells.
• Surface casing depth determination for WCSB freshwater aquifer protection under AER Directive 008 and BC Oil and Gas Activities Act requirements including casing seat selection relative to the base of groundwater protection, cementing to surface, and pressure testing requirements before drilling below the surface casing shoe: AER Directive 008 (Surface Casing Depth Requirements) specifies that WCSB surface casing must be set at a depth equal to the greater of the base of groundwater protection (BGP, defined as the deepest potable aquifer in the area, determined from baseline water well records in AER's well licensing system) plus a minimum standoff distance (15 m below the BGP in most WCSB areas), or the minimum surface casing depth tabulated by Directive 008 for the specific township. After cementing surface casing, AER requires a pressure test at 70% of internal yield for 30 minutes before drilling below the shoe; a casing leak test confirming no annular flow is also required in WCSB sour gas areas under AER Directive 036. Surface casing violations (insufficient setting depth, incomplete cement to surface, or failure to pressure test before drilling) are among the most frequently cited WCSB AER non-compliances, carrying mandatory reporting obligations and potential well suspension under the Oil and Gas Conservation Act.
• Cementing of WCSB production casing for zone isolation in multistage fracture-stimulated Cardium, Viking, and Montney horizontal wells including cement slurry design, displacement procedure, and AER Directive 009 well integrity requirements for zone isolation confirmation: Primary cementing of production casing in WCSB horizontal wells is performed after running the casing string to total depth, with cement slurry pumped down the casing bore and displaced up the annulus between the casing and borehole wall using a two-stage cement job (surface to liner top for the vertical section, separate stage tool or through-drillout cementing for the horizontal lateral). WCSB multistage fracture completion design requires cement isolation between each perforation cluster or sliding sleeve port to prevent inter-zone communication during fracturing; AER Directive 009 requires that the annular seal be verified by a cement bond log (CBL) run after cementing and before perforating or fracturing, with the CBL showing at least a minimum acceptable bond index (typically 0.3 or greater on a scale of 0 to 1.0, where 1.0 represents full cement fill) across every perforated interval to be fractured. Inadequate cement coverage (channels, voids, or free pipe in the CBL between target perforation clusters) must be remedied by a squeeze cement treatment before fracturing or by adjusting the fracturing cluster spacing to exclude the uncovered intervals, preventing inter-zone hydraulic communication during stimulation that would reduce multi-zone completion effectiveness. The AER's WCSB cement verification program has increased the proportion of horizontal wells receiving CBL surveys from approximately 30% in 2010 to greater than 80% by 2020, driven by AER Bulletin 2014-01 cement verification requirements for multistage completions.
• H2S sour service casing metallurgy requirements for WCSB Foothills and Devonian sour gas wells including NACE MR0175 compliant grades, hardness limits, heat treatment specifications, and the distinction between standard API grades and sour service grades for wells with H2S above threshold partial pressure: WCSB sour gas wells with H2S partial pressure above 0.0003 MPa require casing to NACE MR0175/ISO 15156 specifications, restricting maximum hardness to HRC 22 and specifying controlled heat treatment to prevent sulfide stress cracking. Standard API J-55 and K-55 grades meet NACE sour service requirements; N-80, L-80, and C-90 grades require specific heat treatment (Q&T for L-80, normalized for N-80) to meet the hardness requirements; P-110 and Q-125 grades are generally not accepted for WCSB sour service without special manufacturer qualification because their high yield strength requires hardness above the NACE limit that makes them susceptible to SSC in H2S-containing wellbore fluids. WCSB Foothills wells with bottom hole H2S concentrations above 1% (partial pressure above 0.7 MPa at 70 MPa BHFP) are designed with L-80 or C-90 sour service casing in all production string sections and with 13Cr or 25Cr alloy production tubing where H2S combined with CO2 creates a corrosive environment that carbon steel cannot withstand without accelerated corrosion.
• Casing inspection, corrosion assessment, and integrity management programs for aging WCSB Cardium and Viking production casing under AER Directive 009 well integrity requirements for wells approaching end of productive life or scheduled for abandonment: AER Directive 009 (Well Integrity) requires WCSB operators to assess casing integrity for all wells scheduled for abandonment or for which a well integrity concern has been identified (sustained casing pressure, casinghead gas emissions, surface casing vent flow). Casing inspection in aging WCSB wells uses three methods: electromagnetic inspection logs (multi-finger caliper or flux leakage tools) that measure casing wall thickness and detect pitting corrosion, perforation damage, or mechanical deformation without fluid contact with the casing interior; pressure testing by pressuring the annular space between production tubing and casing to a specified test pressure (typically 70% of rated collapse pressure for the casing grade and size) for 30 minutes to confirm integrity of the casing as a pressure vessel; and cement evaluation by running a CBL to identify zones of annular communication behind casing that could provide a migration pathway for formation fluids to the surface or to shallow aquifers. Wells failing AER Directive 009 integrity assessment criteria (sustained casing pressure above 0.5% of rated working pressure, or confirmed communication between the production zone and any protected interval) are subject to remediation (squeeze cementing, packer repair, or tubing replacement) or, if remediation is not technically or economically feasible, to suspension and abandonment under AER Directive 020.