The Ground Investigation for a Storage Cavern in Metamorphic Rock at 600m Depth

Synopsis

This presentation outlines the investigation works for a deep compressed air storage cavern located in a complex metamorphic environment. The ground investigation combined HQ‑3 coring from surface and from an adjacent underground mine, including two sub‑horizontal 460m boreholes drilled across the planned cavern. Core was logged for structural features and tested for rock properties, with several methods adapted to address significant rock anisotropy, including modified point load, triaxial, and shear tests.

A major focus was the assessment of groundwater inflow and potential air leakage. Pore pressure and permeability were measured using staged testing along the horizontal boreholes with a straddle packer system, downhole valves, and precision pressure monitoring, following adapted oilfield practice.

Rock stress conditions were evaluated using three‑dimensional overcore tools, and both vertical and horizontal holes were logged with acoustic televiewer and full‑wave sonic sondes. The study concluded the heterogeneous rock mass was suitable provided appropriate design measures…