Reaction Front Fingering in Anhydrite Cemented Sandstone

Abstract

A geothermal bore at Allermone (Germany) tapped unintentionally and unexpectedly a reservoir almost totally cemented with anhydrite. Laboratory core flooding experiments were conducted to determine the potential to stimulate the geothermal aquifer. During these experiments sudden permeability increases, due to dissolution of anhydrite, were observed. Preferential flow paths were detected in the cores by X-ray tomography and are here simulated numerically. The numerical code SHEMAT a simulation system for coupled flow, heat transfer, species transport, and chemical reactions is used. Data of the core flooding experiments and the numerical studies coincide. A feasibility study to stimulate the geothermal aquifer at AllermcShe shows that the development of preferential flow paths within the vicinity of the bore can be expected. Hence, gentle stimulation of the bore seems possible.