Abstract:
This paper is the result of geothermal survey engineering.
Objective The Qiabuqia area within China's Gonghe Basin represents a key research zone for granite−hosted hot dry rock (HDR) systems. This study systematically investigates the caprock thickness variation and granite basement topography while elucidating the spatial configuration of granitic bodies to establish predictive models for HDR reservoir distribution.
Methods Innovatively applying the Time−Frequency Electromagnetic (TFEM) method−traditionally employed in deep hydrocarbon exploration − to HDR characterization, we implemented a comprehensive workflow encompassing advanced data preprocessing, electrical parameter optimization, and constrained inversion modeling. Integrated interpretation of resistivity profiles with multi−source datasets (geological mapping, borehole logs, and auxiliary geophysical surveys) enabled three−dimensional reconstruction of stratigraphic architecture, granitic intrusion geometry, and HDR reservoir characteristics.
Results (1) TFEM demonstrates exceptional capability in resolving electrical stratigraphy within 10 km depth. Resistivity profiles reveal a tripartite H−type structure comprising a sub−high−resistivity superficial layer (900−1,400 m thickness, eastward−thinning), an intermediate conductive zone, and a high−resistivity basement. Granitic bodies exhibit A−type resistivity progression with depth, featuring westward−deepening top surfaces (−900 to −2900 m elevation). (2) Thermal logging−constrained models delineate distinct spatial configurations of the Qiabuqia and Dalianhai HDR reservoirs, demonstrating strong correlation with structural highs.
Conclusions (1)Thermo−structural analysis identifies competent batholiths and stocks as preferential heat flow conduits, serving as prime HDR exploration targets. (2)Magmatic emplacement heterogeneity drives vertical zonation: deep−seated batholiths transition upward through intermediate stocks to shallow sills. (3)Resistivity anomalies within granitic masses reflect structural integrity gradients, with batholiths and stocks exhibiting superior mechanical continuity compared to fractured sill complexes.
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