--> Comparison of Geological Factors Affecting Production in the Cardium Tight Light Oil Play, Alberta, Canada

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Comparison of Geological Factors Affecting Production in the Cardium Tight Light Oil Play, Alberta, Canada

Abstract

Unconventional type hydrocarbon plays are often characterized by significant lateral variations in both initial rates and cumulative production, although their extensive hydrocarbon saturation and commonly relatively uniform lateral reservoir properties. While differences in drilling and completion between wells have a large impact on productivity, subtle changes in reservoir properties often have a large impact on production from unconventional type reservoirs. This study evaluated the geological controls on productivity sweet spots within the extensive Cardium Tight Light Oil Play in western Alberta, and will present a comparison of the several areas. Cardium shoreface sandstones and transgressive conglomerates hosts one of largest conventional oil accumulations within the Western Canada Sedimentary Basin with more than 5 billion barrels of conventional oil reserves plus large reserves of oil, condensate and gas within unconventional type reservoirs. Since 2008 multistage horizontal wells targeting low porosity and permeability muddy, intensely bioturbated sandstone reservoirs around the halo areas of the legacy pools has revitalized the play. The characteristics of the different areas within the Cardium halo play fairway will be presented and contrasted. Although many of the areas have similar sedimentary facies they have different reservoir properties due to differences in depositional conditions in the offshore environments, burial depth, timing of hydrocarbon charge and post-depositional faulting which resulted in slight differences in bedforms, mud content and type, tracefossil assemblages, diagenesis, compaction, cementation, pore types, and fluid content. Focus will on how these parameters affect productivity and how sweet spots often appear similar on well logs but detailed core examination and analysis reveal these subtle differences. Detailed core observations were complemented with thin sections, SEM analysis, and mercury (MICP) data of the various micro facies, i.e. muddy sandstones versus sandy borrow fill. Full core diameter CT scanning was used to characterize the 3-D connectivity of the sandstone beds and sandstone filled borrows for each reservoir facies. Due to the small scale and discontinuity of the sandstones beds and borrow fills, routine plug and full diameter core analysis often underestimate the flow capacity of such intensely bioturbated reservoirs, where sand filled borrows provide flow pathways in 3-D.