High-Pressure High-Temperature Laboratory Micro to Nano seismic Comparison of GEIOS Nitrogen Hybrid Gas Nanofoam and Conventional Water-Proppant EGS

Abstract

Laboratory validation of a nitrogen hybrid gas nanofoam integrated with engineered conductive geocasing demonstrates maintained fracture support and enhanced conductive heat transfer under simulated geothermal reservoir conditions of 80–140 MPa and up to 300 °C. A nitrogen-dominant working fluid with embedded Al₂O₃ (0.6–0.8 vol%) and silica (0.3–0.5 vol%) nanoparticles (~95% N₂ by volume) was evaluated in an Inconel 718 high-pressure, high-temperature vessel. Over a 15-week programme, an initial 3 mm fracture aperture showed 12% total degradation, while bulk thermal conductivity remained significantly elevated—a 166–336% improvement relative to typical rock and fluid baselines.

Wideband acoustic emission monitoring at core scale (8 sensors, 100–900 kHz, 5 MHz sampling) recorded a shift toward lower-energy, higher-frequency micro-failures, with total events reduced by 49% (52 vs. 102), average event energy reduced by 59% (2.34 vs. 5.73 aJ), and characteristic frequency increased by 83% (6.55 vs. 3.57 kHz) relative to water-fractured controls; the apparent b-value reached 1.52, consistent with distributed microcracking. Probabilistic uncertainty and risk analysis identified stress-gradient thresholds separating acceptable operation from potentially unacceptable regimes. Pressure decay to 50% of initial overpressure occurred in 3.2 min, and post-test material recovery exceeded 98% with a biodegradation index of 0.94.

Results support a conduction-dominated extraction strategy combined with continuous microseismic monitoring and adaptive pressure control, while field-scale validation is required to confirm reservoir-scale seismic behaviour.