Application of acid oil-displacing composition in a well with hydraulic fracturing crack and in naturally fractured carbonate reservoir

The paper uses a mathematical model of hydraulic fracturing, obtained by the methods of the elastic filtration theory of oil-displacing fluid injected into the formation, which is a heterogeneous, fractured-porous medium. The rock formation undergoes elastoplastic destruction with the generation of cracks when the pressure difference in the fluid reaches a critical value. An increase in the volume of the system of fractures in the cracking zone leads to a decrease in the porosity of the blocks in accordance with the pore volume strain compatibility condition. Engineering formulas are obtained for the radius of cracking and crack opening. The flow rate of a well with a hydraulic fracture decreases over time. This phenomenon, which is also characteristic of carbonate formations with natural jointing, is explained by the increasing effect of capillary locking of the formation water accumulating near the walls of the cracks. Laboratory studies on the flat micromodel of the reservoir showed the possibility of restoring the well production rate with a fracture by injection of an acidic oil-displacing composition based on surfactants, inorganic acid adduct and polyhydric alcohol. The results of successful field tests of the composition on the Permian-Carboniferous deposit of high-viscosity oil from the Usinsk oilfield with fractured-porous reservoir rock are presented.