Alberta has historically been the home to much of Canada’s hydrocarbon production. New technologies are unlocking resources from shale and siltstone formations that have the potential to dramatically increase Alberta’s resource base beyond conventional pool-based reservoirs. The Energy Resource Appraisal group of the Alberta Energy Regulator has developed a methodology for quantifying the resources in shale, siltstone, or tight sandstone reservoirs that are characterized by continuous hydrocarbon saturation rather than discrete pools. This methodology is data-driven and incorporates the quantification of uncertainty at every step.
A wide variety of data sources are used for resource quantification, including geological picks, log analysis, adsorption isotherm analysis, XRD mineralogy, organic petrography, Rock Eval, reservoir tests, and Dean Stark testing. The geological variables that have sufficiently dense sampling are mapped using geostatistical simulation. Secondary variables that are correlated to the mapped variables can be determined by modelling the bivariate relationships. Other variables that are sparsely sampled or have large uncertainty are assigned values based on univariate distributions. The uncertain distributions for all variables are simulated 1000 times and the results used to calculate potential resource endowment. The results of the 1000 iterations represent the range of uncertainty in the resources.
Recent work has produced hydrocarbon resource estimates for previously unassessed units, including the lower Doig siltstone and the middle portion of the Colorado Group. The application of porosity and net thickness cutoffs has been used to estimate technically recoverable resources in the Duvernay Formation. Other assessments are in progress to better understand the quantity of gas, NGL, and oil resources in Alberta.
The Alberta Energy Regulator / Alberta Geological Survey is continuing work to quantify the hydrocarbon resources in shale and siltstone units. This work includes many formations, members, and units. The initial assessments look at all hydrocarbons initially in place but will eventually include cutoffs to quantify technically recoverable resources.
Recent but as-yet-unreleased assessments include
- The middle Colorado shale from the top of the Second White Specks Formation to the base of the Fish Scales Zone and
- The lower Doig siltstone, which is equivalent to the upper Montney Formation in British Columbia.
Assessments of these units take into account uncertainty at every step and produce estimates of gas, oil, and natural gas liquids in place.