The hydrodynamic behavior of water–polyethylene oxide (PEO) solutions under model flow conditions in hydroperforator jet-forming nozzles was investigated. Experimental results confirmed that, in the nozzle inlet region, PEO macromolecular coils can transition into a highly extended conformation. The ratio of the measured birefringence to its theoretical maximum reached 0.33, corresponding to approximately 60% uncoiling of macromolecular chains. The energy potential of high-velocity jets formed from water–PEO solutions was studied at various polymer concentrations and nozzle discssharge pressures. Evaluation was conducted based on the penetration depth of the jet into a model casing string of an oil and gas well, the cement sheath, and the surrounding rock formation. Additional assessment was performed by measuring the impact force of the jet on a metal target mounted on a physical pendulum. A comprehensive investigation of the perforation process confirmed the mechanism underlying the high destructive capacity of polymer solution jets. It was shown that the exceptional cutting efficiency is due to the dynamic pressure exerted by the water–polymer jet, structurally “reinforced” by the highly stretched macromolecular chains formed in the nozzle inlet region. The assessment was carried out by measuring the impact force of the jet on a metal plate fixed to a physical pendulum.