Use of Deep Slimhole Drilling for Geothermal Exploration

Abstract

Deep slimholes were used very effectively in Indonesia in the 1990’s for geothermal resource delineation and potentially again have a major role in assisting early exploration of geothermal prospects that are increasingly challenging because of ambiguous surface indications and more remote and difficult terrain. The use of deep slimholes can improve the success rate of subsequent appraisal drilling using conventional or large diameter wells and so it can provide cost savings on the total project cost. The use of deep slimholes for exploration reduces the early capital spend on a project, and therefore improves the success-weighted Net Present Value (NPV) of a project, particularly where there is a reduced probability of successfully finding a resource. In combination, the reduced capital and improved scheduling of expenditure plus reduced cost of failure for a project (or for a portfolio of projects), has the ability to reduce the tariff required for geothermal projects in Indonesia.