Capacity Enhancement in Gas Storage Reservoirs via Pulse Fracturing and Acid Pre-Treatment: Mechanisms, Modeling, and Field Applications

This study tackles the challenges of enhancing gas-bearing underground storage reservoirs, which face issues such as poor reservoir quality, undefined process parameters, and high operational risks. It introduces a novel integrated approach combining laboratory experiments, numerical simulations, and field applications to optimize fracturing technology and working fluid systems, improving injection–production performance and operational reliability. Using rock mechanics data obtained under in-situ conditions, elastic modulus and Poisson’s ratio correction models were developed via radial basis function networks, achieving high predictive accuracy (mean squared errors of 2.14 and 2.57). A self-propping fracture formation mechanism was identified, alongside the development of high-performance acid systems optimized for dissolution rate, permeability damage, and fracture surface friction. A 3D dynamic fracture propagation model was developed, incorporating cohesive zone and perforation elements, enabling the optimization of pump rates (4–12 m3/min) and pulse fracturing modes. Field trials showed that pulse fracturing extended fractures by 17.3% compared to constant-rate injection, and acid pre-treatment enhanced gas injection intensity by 20.9%. Numerical simulations indicated a critical relationship between pump rate and cement sheath failure risk, highlighting the importance of managing pump rates to maintain structural integrity. The study’s innovations, including a fracture control strategy based on fracture surface friction and an optimized acid system, provide scalable solutions for low-permeability gas storage reservoirs. These findings contribute significantly to improving the operational efficiency and sustainability of underground gas/energy storage, offering valuable insights for the integration of renewable energy and energy security.