Realistic core testing improves sandstone acid treatment ///

Core flow testing has long been an accepted method for assessing formation sensitivity to treatment fluids and evaluating sandstone matrix response to acidizing treatments. However, core flow tests are often conducted with standard core material like Berea sandstone, rather than the actual formation core. Furthermore, test procedures typically use undamaged cores.1, 2, 3 Studies with undamaged cores can be meaningful in assessing rock's sensitivity to particular acid formulations, including the severity of acid/ formation reaction-product re-precipitation. However, in evaluating effectiveness of specific hydrofluoric (HF) acid systems for removing permeability damage and limiting formation acid sensitivities, testing undamaged cores is not sufficient. A systematic approach to core flow testing uses procedures that damage cores in a manner representing realistic damage mechanisms, then remove damage with appropriately selected HF treatment systems (and non-acid, pre-acidizing treatment systems, if necessary). The degree of damage removal and stimulation is measured after each treatment step.

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