Thermal Gradient Signatures of Fault-Controlled Hydrothermal System: Insights from Conceptual Models and Field Data

Abstract

Geothermal exploration in structurally controlled systems requires careful assessment of well placement relative to permeable fault zones and associated upflows. This study investigates multiple drilling scenarios that reflect different locations of temperature gradient holes (TGH) with respect to a fault-hosted hydrothermal reservoir and its upflow plume. Using a combination of conceptual models and field data, we compare thermal profiles from wells that (1) completely miss the reservoir, (2) encounter distal upflow from the heat source, (3) intersect the isothermal reservoir, and (4) capture shallow or proximal upflow at varying locations. We also evaluate these scenarios under different fault dip angles and rock thermal conductivities. The comparative analysis highlights diagnostic temperature-depth trends, including shallow isothermal zones, steep conductive gradients, and deep upflow signals. By integrating field observations with modeled profiles, we demonstrate how variations in well location influence both the apparent subsurface temperature structure and the inferred reservoir potential. These findings provide practical guidance for geothermal exploration strategies, emphasizing the importance of structural context, hydrothermal upflow geometry, and well trajectory when targeting economically viable resources.