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Methodology

Standing methodology for the WCSB S&D; model.

What this model is

A physical supply/demand balance for the Western Canadian Sedimentary Basin. It is not a differential forecast. Every number carries its publisher, vintage, and method; unknown values stay null, never fabricated.

Supply forecast

Forecast at the most granular public leaves, then aggregate: AER ST53 commercial-scheme leaves for SAGD/CSS, ST39 facility rows for mined bitumen and SCO, ST3 lines for conventional streams. Each leaf is a trailing-12-month mean times a seasonal factor from the last three complete years. Mapped ST53 projects cover 76.7% of ST3 in-situ; the balance is grossed up with an explicit coverage factor.

Maintenance

Maintenance offline counts only public-confirmed company guidance and transcript items, modeled at the project leaves. Seasonal-pattern indicators are shown as assumed and never enter the math. The forward calendar (2026-10-01 to 2027-09-30, compiled 2026-09-22) distinguishes public-confirmed, guidance-sourced, and pattern-indicated entries; unknown volumes stay null.

Grade layer

Supply is cut by grade as well as by source: SCO (upgraded production), marketable bitumen (dilbit), and bitumen sent for further processing. Grade conversion default: 0.87 SCO per barrel of bitumen feed (observed: fleet 0.865, Horizon 0.888, Syncrude 0.843). NFT mined bitumen (Suncor Base, Syncrude, Horizon) is upgrader-locked and cannot meet pipeline dilbit spec; PFT mines (Kearl, Fort Hills) sell dilbit directly; SAGD bitumen is flexible between dilbit sales and upgrader feed. See the dashboard grade-layer assumptions panel for the full leaf mapping.

Storage

Implied storage change = supply total minus maintenance offline plus diluent imports minus refinery demand minus removals (all kb/d). It is the simple physical balance, not the ST3 inventory print. Positive = builds into commercial storage; negative = draws.

Trading cycle

Injection-month barrels trade during the prior calendar month, before noms day. The tradable barrel is always past the current maintenance window, so the forward balance for the next tradable injection month is what prices barrels, not the current outage snapshot.

Sources

Sources
PublisherDatasetURLPublishedVintage / coverageRetrieved
Alberta Energy RegulatorST3: Alberta Energy Resource Industries Monthly Statisticshttps://www.aer.ca/data-and-performance/data-and-publications/statistical-reports/st3MonthlyActuals through 2026-07 (latest file vintage 2026-08-27)2026-09-22
Alberta Energy RegulatorST53: In-situ project data (BITUMEN sheet)https://www.aer.ca/data-and-performance/data-and-publications/statistical-reports/st53MonthlyActuals through 2026-072026-09-22
Alberta Energy RegulatorST39: Mine and upgrader facility dataURL not recorded in repoMonthlyActuals through 2026-052026-09-22
Canada Energy RegulatorPipeline throughput, capacity and apportionment (open data)https://www.cer-rec.gc.ca/open/energy/throughput-capacity/Monthly, ~3-month lagJan 2018 to Jun 20262026-09-22
Company disclosuresQuarterlies, budget releases, investor presentations, earnings callsURLs per record in annotations/maintenance_forward.yamlAs publishedForward maintenance calendar window 2026-10-01 to 2027-09-30, compiled 2026-09-222026-09-22
Heavy Reading modelWCSB S&D dashboard build (21 granular leaves, grade layer, maintenance math)No public URL (repo build)Per buildForecast built 2026-09-22; Aug-Sep 2026 nowcast built 2026-09-232026-09-23

Every number on this page traces to a row above. Anything missing its own source line is flagged in place; nothing ships with an unsourced number.

Heavy Reading · the WCSB supply letter.
Public information only: AER ST3/ST39/ST53 and company disclosures via the WCSB S&D model. Nothing here is licensed data, so this page renders the same with or without ?public=1.