Some controls on the aqueous geochemistry of the lower Cretaceous basal quartz of the southeastern Alberta Basin.

摘要

Regional patterns of flow and geochemical changes have been mapped within the Alberta Basin, and the regional scale shows general trends. Working at a smaller scale, the recharge zones are interpreted to occur along a regional system of fractures or faults with northeast-southwest and northwest-southeast trends. Recharge in turn creates zones of bacterial activity and concomitant geochemical changes. Oils of different families may also migrate along this fracture system.; Bacterial activity is associated with rapid changes in dissolved element concentrations; both occur around the edges of the interpreted recharge zones. The dissolution of silicates and precipitation of quartz cement is tied to bacterial activity and subsequent mixing of HCO3- and Na+-enriched waters with formation waters, a conclusion not observed in any of the literature. Deposition of carbonate cements is also thought to be tied to mixing. Thus spatial patterns in aqueous geochemistry could predict problem reservoirs, areas of secondary porosity, or the quality or type of oil.