The Controlling Influence of Natural Joint Continuity of the Creation of HDR Systems-Experience and Modelling

Abstract

A brief outline of the development of conceptual designs in Hot Dry Rock geothermal reservoirs, based on heat extraction requirements, leads to todays favoured volumetric models, which depend on the stimulation of natural jointing. Evidence from field experiments is used to demonstrate that no new flow. paths have been created by stimulation, and that the nature, particularly continuity, of the natural jointing has a control 1 i ng influence on reservoir development. The paper goes on to show how fracture network models can play a significant role in understanding the develapment process, and presents a small study undertaken to illustrate the joint continuity problem. The study shows how only a very small number of the larger joints may be required to form a connection between two wells, and how under these circumstances a low area flow path may be created.