Cardium Fm. wells are - at present - drilled in reservoirs around legacy areas of oil fields. However, studies summarizing the geological characteristics of such reservoirs are scarce. A central issue is that as fields expand elemental parameters of the formation become unpredictable. As a contribution to solve this problem, “Cardium A” intervals at the halo (Brazeau T44-47R9-12W5) of the Pembina field are explored to reveal successions that clean upwards to very-fine grained litharenites and bioturbated wackes with abundant deformation features. Permeability (PDPK) and porosity measurements reveal that reservoirs are not uniformly tight but consist of mixtures of conventional (>0.01mD) and unconventional (<0.01mD) zones. Petrological and geochemical (XRD, XRF, SEM, BSE, EDX, and CL) studies suggest that resource recovery may be affected by the presence of swelling clays (smectite, mixed-layer illite/smectite, illite, chlorite, sericite, and kaolinite). Nonetheless, a practical method - based on production data- is presented to assess exploration risk and to expose the areal distribution of high gas-to-oil ratios.