Investigation of Shock Wave Interference in Low-Debris Perforating Gun System

Abstract

Abstract All perforating operations cause some debris. Perforating debris can damage surface equipment and completion tools and negatively impact production. In high-pressure deepwater wells, minimizing debris becomes more important because costs associated with debris accumulation might impact sensitive completion equipment or might not be realized until later in a well's life. This necessitates a new low-debris perforating system designed to significantly reduce debris associated with high-shot-density big-hole charges. Past solutions at low-shot densities have involved introducing materials into the perforator to retain debris. The close proximity of these materials to energetic components can introduce strong shock waves between individual charge detonation events. This phenomenon has an undesirable effect on perforator performance and should be minimized without compromising debris retention. Traditional gun designs are based on a trial-and-error approach, using very limited post-testing measurements as design verification tools. The extremely complicated interactions among different components of the gun during a test cannot be observed experimentally, and the detailed physical process is not well understood. Therefore, numerical models have been developed to simulate the detailed dynamic responses of gun systems subjected to multiple shaped-charge detonations. This paper describes the coupling of hydrocode-based three-dimensional (3D) numerical models with FEA and full- scale surface testing. High-fidelity modeling is employed to capture the dynamic response of the materials under shock loading. The model is then used to investigate shock wave interference among the major components of the gun system. The underlying mechanics dominating the gun performance are identified. Consequently, considerable insight is obtained into gun system design for effective shock wave mitigation without compromising low-debris characteristics Investigations are performed for the original baseline design and a modified design based on numerical simulation results. Numerical and experimental results are presented for both designs. By comparison, the modified design outperforms the baseline design, as predicted by the numerical model, thereby validating the numerical model and providing greater confidence to the design cycle. Numerical simulations combined with the traditional experiments facilitate effective decision making, thus making the overall design cycle much more efficient.