Thermal dynamics and economic parametric analysis of repurposed abandoned wells: Field evidence from full-well section temperature monitor

• A pioneering field trial of wellbore heat exchanger from an abandoned well with entire well section circulation water dynamic temperature profiling was conducted. • The heat performance of the test well matched that of the well with higher bottom-hole temperatures in the same region remarkably. • The spatiotemporal thermal dynamics characteristic from the field data was revealed firstly, identifying controlling mechanism on temporal-spatial heterogeneity in thermal recover across heating and recovery phases. • Thermo-economic parameters quantitative optimization based on abandoned well repurposing system was investigated. Wellbore heat exchangers (WHEs) have gained attention for eco-friendly and sustainability. Addressing the gaps in full-well section temperature monitoring and thermo-economic parametric analysis on abandoned well retrofit, this study presented pioneering field trial of abandoned well retrofitted for geothermal in Beijing. We revealed the first quantitative characterization of water temperature dynamics throughout heating-recovery phases, enabled by full-well section distributed profiling. Finally, thermo-economic parameters optimization were investigated combining FEM modeling. The key findings showed that: (1) The test well achieved sustained thermal power of 156.8kW, comparable to the well with higher well bottom temperature in the same region, due to wellbore size, rock thermal conductivity and inner tube insulation. (2) Thermal recovery exhibited stage-wise and vertical variation characteristics. During the initial month, recovery proceeded rapidly(max 0.067 °C/day) under dominant control of ΔT between the wellbore and formation. Subsequently, recovery decelerated as rock thermal conductivity became the dominant factor, with carbonate strata demonstrated approximately four-times higher recovery rate than the sandstone and mudstone section. (3) The flow rate range of 400–600 m³/d demonstrated a 3.3–8.0 % enhancement in life-cycle economic performance compared to other comparison flow rates. The application of PE-RT as the inner tube material yielded a 2.7–20.6 % improvement in economic efficiency relative to double-layer adiabatic steel tubes(DLAST). Each 1 °C increment in inlet temperature corresponded to a 4.5 % decrease in economic. This work provides critical insights for WHEs design and abandoned well repurposing.