Abstract: With the continuous discovery of shallow offshore oil and gas reservoirs and increasing demands for old well stimulation, certain pay zones are sealed within the overlapping section of 9⅝″ and 13⅜″ dual casings, making traditional perforation techniques ineffective in establishing communication with the formation. This paper presents a systematic feasibility study on dual-casing perforation technology. A multi-medium coupled dynamic model was established using ANSYS/LS-DYNA to simluate the dynamic process of shaped charge jets penetrating through inner casing, cement sheath, and outer casing. Full-scale surface simulation tests were conducted to verify penetration performance, culminating in successful field application in the DST1 test of Well X. Results show that under identical charge conditions, compared to single-casing perforation, penetration depth decreases by up to 31% in dual-casing scenarios, while the average hole diameter in the outer casing reduces to 5.88 mm. Nevertheless, both laboratory tests and field operations achieved complete penetration of both casing layers, yielding high-quality gas samples and reliable formation data. The study demonstrates that with optimized ultra-deep penetration charges, phase arrangement, and charge structure, dual-casing perforation is technically viable and the result provides critical technical support for deepwater high-temperature high-pressure (HTHP) gas field development, reinjection well construction, and completion of complex structure wells.