Rayleigh-Frequency-Shift Distributed Strain Sensing (RFS-DSS) of Huff-Puff Tests Conducted at Utah FORGE

Abstract

Huff-puff (cyclic injection/flowback) tests can provide comparatively rapid hydraulic and tracer responses without cross-well testing. In September 2025, we executed a huff-puff diagnostic test at the Utah FORGE well 16B(78)-32 and collected a rich multi-sensor dataset. Fiber optic cable housed in 4.4 cm diameter steel coiled tubing installed in the cased hole provided Rayleigh-based distributed strain sensing (RFS-DSS), together with distributed temperature sensing (DTS) and distributed acoustic sensing (DAS). Three rate steps (2.5, 5.0, 7.5 bpm) produced repeatable DSS responses concentrated near perforated intervals. DSS responses at perforations may be due to changes in temperature, strain, or both. Decoupling thermal and mechanical signatures requires joint analysis of DSS and DTS. In addition, the transfer of both heat and strain through the coiled tubing requires additional consideration. Nevertheless, these tests indicate that it is possible to identify flow exchange during huff-puff tests using an intervention fiber installation in coiled tubing. Quantitative analysis and workflow development are underway.