Assessing shale gas potential through classification of geochemical and mechanical properties of reservoir facies in the Upper Devonian shale succession, Liard Basin, Canada

A comprehensive estimation of shale generation/storage capacity (original generative organic carbon (GOCo)) and hydraulic fracturing characteristics (brittleness index (BI)) was conducted in the Upper Devonian shale sequence of the Liard Basin.GOCo was calculated from fraction of type II kerogen inferred from biogenic silica concentrations.BI was estimated from mechanical properties calculated from well-log data.Without well-log data, BI was converted from the relative contribution of biogenic and detrital silica concentrations.Based on GOCo and BI, the shale sequences were divided into four resource facies (RFs): RF1 (GOCo <1 wt%, BI 20-40), RF2 (GOCo 1-3 wt%, BI 20-60), RF3 (GOCo 2-5 wt%, BI 60-95), and RF4 (GOCo 5-14 wt%, BI 60-95).Shale with RF3 and RF4 characteristics were determined to have high hydraulic fracturing efficiency, high organic porosity, and capability to generate large amounts of gas.Considering the vertical variation of RFs, the Patry and Lower Exshaw formations are estimated as favorable shale gas reservoirs with abundant gas content and high hydraulic fracturing efficiency.If 30% of the total gas generation potential estimated from GOCo remains in the shale gas reservoir, the sum of residual gas volume of both formations in the study wells exceeds 280 bcf/section.