Perforation of Casing Strings in Oil and Gas Wells with a Polymer Solution Jet: Scientific and Practical Aspects 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...