Fluid-Rock Interactions in a Paleo-Geothermal Reservoir (Noble Hills Granite, California, USA). Part 2: The Influence of Fracturing on Granite Alteration Processes and Fluid Circulation at Low to Moderate Regional Strain

Geosciences

Sébastien Potel¹  Arezki Chabani¹  Ghislain Trullenque¹  Johanne Klee¹  Béatrice A. Ledésert²  Ronan L. Hébert² 

[1] B2R, Geosciences Department, Institut Polytechnique UniLaSalle Beauvais, 19 Rue Pierre Waguet, F-60026 Beauvais, France;Geosciences and Environment Cergy, CY Cergy Paris Université, 1 Rue Descartes, F-95000 Neuville-sur-Oise, France;

关键词: fracturing processes;    fluid circulation;    granite alteration;    low to moderate regional strain;    geothermal reservoir;   

DOI  :  10.3390/geosciences11110433

来源: DOAJ

【 摘 要 】

Fracture connectivity within fractured granitic basement geothermal reservoirs is an important factor controlling their permeability. This study aims to improve the understanding of fluid–rock interaction processes at low to moderate regional strain. The Noble Hills range (Death Valley, CA, USA) was chosen as a naturally exhumed paleo geothermal reservoir. A series of petrographic, petrophysical, and geochemical investigations, combined with a fracture distribution analysis, were carried out on samples collected across fracture zones. Our results indicate that several generations of fluids have percolated through the reservoir. An increase of (1) the alteration degree; (2) the porosity values; and (3) the calcite content was observed when approaching fracture zones. No correlation was identified among the alteration degree, the porosity, or the calcite content. At a local scale, samples showed that the degree of alteration does not necessarily depend on the fracture density or on the amount of the strain. It is concluded that the combined influence of strain and coeval fluid–rock interaction processes drastically influence the petrophysical properties of fracture zones, which in turn impact geothermal production potential.

【 授权许可】

Unknown