Survival of an Optical Fiber Flatpack Due to Perforation

Abstract

Optical fiber flatpacks, which are cable-reinforced plastic-encased fiber bundles used for local temperature and acoustic measurements, can be stressed when near a perforating gun. The fiber itself is floated in metal tubes with gel. Understanding the behavior under severe shock causes the use of potential mitigation schemes. In this work, the flatpack containing optic fibers is simulated for survivability on the casing of a perforating gun system. Using a shock hydrocode in two-dimensions (2D), a flatpack is simulated on the 5 1/2-in. casing of a 3 3/8-in. gun with a 21-g shaped charge. Effects of concrete encasement, clamps, and off-angle shots are considered. The view is in the plane of one shaped charge. Quantitative results include pressure temporal profiles, velocity profiles, and g acceleration at the fibers. Pressure at the flatpack peak is in the hundreds to thousands of psi, and accelerations peak in the hundreds to thousands of g. Unconfined flatpacks tend to launch from the casing, while confined flatpacks tend to oscillate at their location. Pressure contour models show the shaped charge breaking into multiple pressure pulses. The primary shocks are in front of and behind the charge. Secondary pulses occur off-axis near the base of the charge and from the jet bow shock near the top of the charge. Overall comparative simulation results indicate optimum flatpack location and configuration. Novel mitigation schemes are identified and simulated. A fiber-optic flatpack has been simulated in a zero- degree loaded gun for the first time; this information helped with understanding survivability against shaped charge shocks.