Lab-Scale Permeability Enhancement by Chemical Treatment in Fractured Granite (Cornubian Batholith) for the United Downs Deep Geothermal Power Project, Cornwall (UK)

A hydrothermal doublet system was drilled in a fault-related granitic reservoir Cornwall. It targets the Porthtowan Fault Zone (PTF), which transects Carnmenellis granite, one of onshore plutons Cornubian Batholith SW England. At 5058 m depth (TVD, 5275 MD) up to 190 °C were reached dedicated production well. The injection well is aligned vertically above and reaches 2393 MD. As part design process for potential chemical stimulation open-hole sections doublet, lab-scale acidification experiments performed on outcrop analogue samples from Batholith, include mineralised veins. experimental setup comprised autoclave sample powder plugs, core flooding tests plugs investigate what degree permeability natural artificial (saw-cut) fractures can be enhanced. All petrologically petrophysically analysed before after track all changes resulting acidification. Based comparison mineralogical composition OAS with drill cuttings well, results transferred hydrothermally altered zones around faults PTF. Core Flooding Tests Autoclave Experiments result enhancement factors 4 >20 0.1 40, respectively. Mineral reprecipitation avoided stimulated by sufficient post-flushing.