CLASSIFICATION OF ONE-DIMENSIONAL STEADY-STATE 2-PHASE GEOTHERMAL FLOWS INCLUDING PERMEABILITY VARIATIONS - I - THEORY AND SPECIAL CASES

This paper describes a graphical method for classifying reservoir mode ls of the above type, and for clarifying the connection between permea bility (and permeability gradients) and saturation. The theory behind the method is reviewed, and then the technique is applied to the examp le of a bottom-heated geothermal heatpipe, which is shown to have a ma ximum length, beyond which the only possible stable continuation (down wards) is into single-phase vapour. A permeability increase (downwards ) always acts to induce a liquid saturation increase. A similar conclu sion holds for non-zero net mass flow but with no conduction. Our theo retical results agree with those obtained by numerical simulation. (C) 1998 Elsevier Science Ltd. All rights reserved.