Low Surface Tension Hydrochloric - Hydrofluoric Acid Mixtures in Low Porosity, Low Permeability Sandstones

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Abstract Hydrochloric - Hydrofluoric acid mixtures have long been topics of investigation with respect to the optimum requirements of concentrations necessary for effectiveness in the stimulation of low Porosity, low permeability sandstone reservoirs. Low permeability sandstone reservoirs. Low concentrations of hydrochloric and hydrofluoric acid in combination with one another (i.e., 3 per cent HCl - 0.6 per cent HF) provide a highly efficient system whereby less damaging reactions occur in the sandstone matrix or fracture system, thus reducing the damage caused by migrating and sloughing fines produced when conventional HCl-HF systems (i.e., produced when conventional HCl-HF systems (i.e., 12 per cent HCl - 3 per cent HF) are used. In addition, the ability of the low concentration HCl-HF system to overcome the capillary imbibition effects, which tend to reduce the efficiency of load fluid recovery following stimulation of a low porosity, low permeability sandstone reservoir, is permeability sandstone reservoir, is enhanced by using ultra low surface tension reduction via the application of a low adsorption, cationic, fluorocarbon surfactant. Coreflow studies illustrate the above nontioned principles. Introduction A significant mechanism for stimulation of low permeability, low porosity, well consolidated sandstone reservoirs is the efficiency and effectiveness of utilizing low concentrations of both HCl and HF acid coupled with fluorosurfactants which can be gel ed with low residue polymers for fracture - acidization with proppant incorporation. Two-thirds of the world's oil is found in sandstone formations. Problems with regard to treatment technique and type range from saturation and clay swelling to regarding clay particle migration, fluid-formation compatibility, shale sloughing, and fluid recovery. Reactions and reaction products have been extensively researched, and it is not within the scope of this paper to dwell upon or challenge them.