Monitoring inert gas stimulation with DAS: A low-cost field case study for fracture probing

Cost and operational complexity often prevent high-density geophysical monitoring during stimulation and other energy operations, particularly when conventional designs require a dedicated monitoring well or large geophone deployments. We present a field trial of an inert gas (liquid CO2) stimulation tool, which is being evaluated as a lower-cost alternative to hydraulic fracturing, monitored using distributed acoustic sensing (DAS) on a single fiber deployed at an onshore well site near Olean, New York. The continuous DAS recording captures the stimulation pulse with high signal-to-noise ratio as well as a structured post-stimulation record that includes both sustained changes in seismic energy and abundant impulsive signals likely tied to cracking events. Using a lightweight detection and first pass location workflow suitable for rapid turnaround, we identify 732 candidate events, track event-rate evolution through time, and estimate source locations for a subset of events that indicate cracking offset from the well. Following the treatment, reported oil production increased by approximately threefold, underscoring the operational significance of the monitored response. The results demonstrate that DAS can provide key stimulation-verification metrics using a smaller and cheaper deployment footprint than traditional approaches, supporting practical, scalable monitoring for stimulation, and more generally, emerging energy applications where low-cost repeatability is essential.