Casing Collar Log in WCSB Completion Operations: CCL Record Interpretation, Depth Correlation Workflow, Tally Pattern Matching, and Quality Control for Perforating and Plug-Setting Depth Verification in Cardium, Viking, and Montney Wells

Key Takeaways

• CCL log quality control in WCSB wireline operations: how collar spike amplitude, width, and spacing are interpreted to confirm a valid depth correlation before the completion engineer accepts the collar log as an accurate depth reference for perforating gun placement in Cardium and Viking horizontal wells: The field quality control criteria for a WCSB casing collar log begin with the collar spike amplitude: a minimum detectable spike amplitude of 15-20 millivolts (for standard API long-thread LTC collars in 5-1/2 inch casing run at typical wireline logging speeds of 10-20 m/min) is generally required for confident depth correlation. Spikes significantly below this amplitude suggest tool standoff from the casing wall (due to wireline tool centralizers, debris accumulation, or eccentricity in a horizontal section) or reduced collar mass from premium connections with minimal upset. Collar spike width (the depth interval over which the deflection exceeds half its maximum amplitude) provides a secondary quality indicator: standard LTC couplings produce spikes 0.3-0.5 m wide, while shorter STC couplings produce narrower spikes and long-collar designs may show broader spikes up to 0.8 m. Spike width consistency across the log identifies sections where the tool was run at non-uniform speed (variable spike widths indicate cable speed variations that can affect depth accuracy). Pattern matching involves selecting the collar with the strongest identifiable spike as a reference point, counting collar spacings uphole and downhole from that reference to build a 3-5 collar window, then comparing the observed spacing sequence (e.g. 12.8, 13.1, 12.5, 13.4 m) to the running tally sequence at the expected depth; a match within 0.3 m per spacing interval confirms the correlation.
• Depth correction procedure from the WCSB casing collar log: calculating the cable stretch correction by comparing observed collar depths to the running tally, applying the correction to the gun or plug position, and documenting the corrected perforation depth in the AER completion report: The depth correction workflow from the collar log begins with the engineer selecting a reference collar (a collar whose tally depth is certain, typically within 100-200 m of the target perforation depth to minimize error accumulation from variable tally measurement precision) and recording the difference between the CCL-measured depth of that collar's spike centre and the tally depth. This difference is the depth correction to apply to the cable counter reading: if the CCL shows the reference collar at 1,837.2 m cable depth but the tally records it at 1,840.5 m, the depth correction is +3.3 m (cable counter is under-reading by 3.3 m, typical for thermal elongation in a warm wellbore). The corrected position of the perforating gun is the cable counter reading plus the depth correction; the gun is moved to the corrected position before firing. WCSB completion operations using coiled tubing instead of wireline apply the same collar-tally correction to the CT depth counter; CT has lower thermal elongation than wireline but is subject to mechanical compression in long horizontals that also contributes depth error. AER Directive 065 completion reporting requires that the CCL correlation methodology and the applied correction be documented for each perforating interval.
• Cased-hole gamma ray correlation with the CCL log for fine-scale formation depth confirmation in WCSB Cardium and Viking horizontal perforating operations, and the relative depth accuracy of the CCL-tally correlation versus the GR-to-openhole log correlation: The CCL log is almost always run simultaneously with a natural gamma ray tool in WCSB completion operations because the CCL provides coarse depth control (collar-to-collar accuracy of 0.3-0.5 m over the collar spacing) while the gamma ray provides fine-scale formation depth control (lithology boundary resolution of 0.3-0.5 m based on the GR tool's vertical resolution). After correcting the CCL log depth to the tally, the cased-hole GR log is shifted by the same depth correction and compared to the original open-hole LWD or wireline GR log run before casing was set; the cased-hole GR response through the 5-1/2 inch casing and cement is attenuated by 30-60% relative to the open-hole log but preserves the formation gamma ray contrast, allowing shale-sand boundaries to be correlated with 0.3-0.5 m relative accuracy. In WCSB Cardium horizontal wells, the combination of CCL tally correlation (confirming depth to within one collar length) and GR-to-LWD correlation (confirming depth to within the GR resolution) provides a two-stage verification that the gun is within the productive Cardium A or B sand rather than in the bounding Colorado shale. This combined CCL-GR correlation is standard practice in WCSB plug-and-perf completions with 15-25 stages where each stage depth must be confirmed independently.
• Reduced-amplitude CCL log interpretation in WCSB wells with premium connections, corroded collars, or severe horizontal eccentricity, and the alternative depth reference methods used when the standard collar log cannot provide adequate depth control: WCSB wells using premium flush-joint connections (Vam Top, Tenaris Hydra, or equivalent) for Montney or Duvernay horizontal production casing have minimal collar protrusion (the flush-joint design eliminates or minimizes the external upset), producing CCL spikes with amplitudes only 20-40% of standard LTC collar amplitudes. In 1970s and 1980s-vintage Cardium and Viking vertical producers with corroded couplings, the iron oxide products of corrosion alter the magnetic permeability of the collar body, reducing spike amplitude while irregularly changing spike shape and width. In both cases, pattern-matching remains the primary depth correlation technique if the spikes are still identifiable, but the confidence interval widens from 0.3 m to 1.0-2.0 m. When spike identification is impossible, WCSB operators have used three alternatives: radioactive marker collars (a slightly radioactive metal sleeve installed on a known collar during the original casing run, detected by the GR tool as a strong positive spike at the marker location); memory acoustic depth markers (an acoustic pulse transmitted from a known reference point and timed to a downhole receiver); and direct cased-hole GR correlation to the open-hole LWD log without CCL depth control, accepting 1-3 m depth uncertainty from cable stretch alone.
• CCL log archiving and AER depth verification requirements for WCSB multi-stage fracture completion wells: how the collar log record supports regulatory depth compliance documentation and resolves depth disputes in production allocation and spacing unit boundary cases: AER Directive 065 (Completion, Workover, and Abandonment) requires that the CCL log be retained in the well file for all WCSB perforating operations and that the measured depth of each perforation interval, corrected using the CCL correlation methodology, be reported in the well completion report submitted to AER within 30 days of completion. For WCSB Montney and Duvernay horizontal wells with 20-25 frac stages, the CCL log is run on every perforation wireline run (25 separate log segments per well) and the corrected depths of all 25 sets of perforations must be documented. AER uses the reported perforation depths to verify that perforations are within the licensed spacing unit and do not penetrate a licensed boundary or the base of groundwater protection zone. In spacing unit boundary disputes, the collar log is the primary perforation depth evidence; discrepancies between CCL-corrected and open-hole LWD depths exceeding 3 m are referred to AER for adjudication under the Oil and Gas Conservation Act.