Quantifying Perforation Damage: A Comprehensive Study Using API RP19B Section 4 Perforation-Flow Testing

Abstract This paper presents a comprehensive experimental and analytical study on core flow efficiency (CFE) and single-shot perforation skin in sandstone cores, with a focus on deriving crushed-zone permeability and thickness. A novel experimental method for determining the theoretical ideal tunnel rate index (RIth) is introduced and benchmarked against the two established methods outlined in API RP 19B (2021): analytical approximation and numerical modeling. The new method eliminates the need for prior knowledge of the core's virgin permeability and accounts for core heterogeneity, offering a more physically representative assessment of perforation performance. The study incorporates three-dimensional tensor characterization of both permeability and inertial resistivity, providing a detailed understanding of anisotropic flow behavior in sedimentary rock. Laboratory tests were conducted under realistic downhole conditions using San Saba sandstone, with post-shot flow testing and CT imaging used to quantify effective flowing perforation tunnel length and geometry. Key findings include: The experimental RIth method produced results consistent with established methods in homogeneous cores, but revealed significant discrepancies in heterogeneous samples, highlighting the limitations of conventional assumptions.Negative skin values observed in some tests using established methods were resolved through the experimental approach, which yielded physically consistent results without post hoc adjustments.A two-by-two matrix of inflow modeling parameters was developed based on core permeability and peak dynamic underbalance (DUB), enabling practical application in well performance simulations. This work advances the state of perforation analysis by integrating rigorous experimental design, advanced flow modeling, and full-tensor core characterization. It provides a robust framework for evaluating perforation damage and cleanup, with direct implications for optimizing well completions and improving reservoir inflow performance.