Updated June 2023
The AER has limited its reserves evaluation of low permeability and shale resources to horizontal multistage fractured wells that are licensed for production in the Cardium, Montney, and Duvernay Formations.
The producing wells were evaluated based on nonconfidential wells on stream in 2022. Forecasts extend 30 years to September 1, 2052. Some wells were not included in this analysis because of their limited extent of production.
Flow Regimes and Reserves for Low Permeability and Shale Resources
Dominant flow: In vertical wells, this kind of flow regime is radial. The pressure drawdown is localized at sandface, and the drainage area is unrelated to completions or horizontal multistage fracturing. In low permeability and shale resource wells, dominant flow regime is linear. The pressure drawdown is throughout the fracture and the drainage area is effectively created by completion or horizontal multistage fracturing.
Transient flow: Transient flow happens during the first few-to-several months after a well goes on production and while a pressure “pulse” is moving out into an infinite or semi-infinite acting reservoir.
Boundary-dominated flow: Boundary-dominated flow is a late-time flow behaviour. It typically dominates long-term production data. The reservoir is also in a state of pseudoequilibrium during this kind of flow. Some major factors affecting the time that it takes for a well to reach boundary-dominated flow include well spacing, fracture spacing, fracture propagation, fracture permeability, and matrix permeability.
Flow Regimes and Reserves Estimates
Based on the expectation of long-duration linear flow periods in these wells, traditional forecasting methods used for more conventional reservoirs are not appropriate for the Cardium, Montney, and Duvernay Formations.
Developed producing reserves were derived using a transient flow model. This helped characterize long-duration linear flow and validate production data points. Flow regime diagnostic plots were used to identify linear flow patterns and define the decline parameters for traditional decline equations. The diagnostic plots help
- assess production history by eliminating early-time data (where the well may have had insufficient time to establish a defined flow regime) and
- identify whether a well is still in transient flow or has transitioned to boundary dominated flow.
Undeveloped Reserves
Undeveloped reserves were assigned based on the reasonable assumption that undeveloped locations will be drilled in the next five years and that there are no physical restrictions to drilling the proposed locations.
The methodology for assigning undeveloped reserves for the Cardium has changed this year. The number of undeveloped locations was determined by well spacing in partially developed and adjacent undeveloped sections, whereas in previous years, it was determined by industry activity.
Formation Evaluation Methods
Cardium Formation:
- Decline method (modified Arps) for well-by-well reserves
Some early production data was affected by operator practices and early linear flow was followed by a long transition period. Linear flow was not observed in some wells because of varying bottomhole pressure and operating practices.
Montney and Duvernay Formations
- Decline method (modified Arps) for well-by-well reserves
- Yu method to determine liquids yields
- Oil wells (high gas yields) (a separate methodology developed by Yu )
Some gas wells in this formation also have a high liquids yield. Yu developed two methods: one for gas with high liquids yields (condensate), and a method for oil with high gas yields (volatile oil). Both Yu methods were used for these formations.