olympic dam project, page-23

dexterbland - that paragraph is directly relevant to Hot Dry Rocks - these systems generally lack fluid and permeability - hence the need to engineer permeability by fracturing hot rocks (HFR) at depth (it's probably the Tester et al 2006 paper?). You are creating a permeable underground heat exchange; in 'conventional' Hot Wet Rock systems (eg nth island New Zealand volcanic related systems) the set up is already in place.