Numerical Simulation of the Atadei Geothermal Field: An Integrated Model Based on Updated Data

Abstract

Atadei geothermal system in southeastern Lembata remains unexploited due to insufficient subsurface constraints. This study formulates a calibrated three-dimensional reservoir model to address existing geological ambiguity and enable spatial delineation of productive zones. Multi-disciplinary inputs—comprising thermal logs, alteration mineralogy, resistivity cross-sections, and stratigraphic data—were synthesized and dynamically matched using VOLSUNG under natural-state conditions. The computational domain, exceeding 50 km², integrates deep convective boundaries, fault-aligned flow discontinuities, and phase transition indicators derived from synthetic wells. The simulation attained thermal convergence at log dt ≥ 11, reflecting hydrodynamic stabilization. Thermodynamic profiling indicates reservoir initiation at ~500 m depth, capped by a 600–1100 m thick low-permeability unit, with localized two-phase behavior observed at sub-vertical conduits. Peak reservoir temperatures exceed 240 °C, with steam saturation ranging from 0.2–0.65. Atypical vapor intrusion at shallow depth in ATS-4 indicates vertical migration through breached seal zones. The refined model reveals heterogeneity in phase distribution and offers a predictive basis for optimized well deployment.