The Iceland Deep Drilling Project: Fluid Handling, Evaluation, and Utilization

Abstract

The prospect of producing geothermal fluids from deep wells drilled into a reservoir at super-critical temperatures and pressures is examined. Since these fluids, which would be drawn from a depth of 4000 - 5000 m, may prove to be chemically hostile, the wellbore and casing must be protected while the fluid properties are being evaluated. A scheme to achieve this by extracting the fluids through a narrow, retrievable liner is described. For the fluids thus produced to be superheated at the wellhead rather than existing in two phases, the reservoir temperature at 5000 m must be above 420 ?C. If the wellhead enthalpy is to exceed that of conventionally produced geothermal steam, the reservoir temperature must be higher than 450 ?C. A deep well producing from a reservoir with a temperature significantly above 450 ?C might, under favorable conditions, yield enough high-enthalpy steam to generate 40 - 50 MW of electric power. This exceeds by an order of magnitude the power typically obtained from a conventional geothermal well. At this time, the extraction of chemicals from the thermal fluids is considered unlikely to be economically feasible. The cost of the fluid handling and evaluation program is estimated to be USD 5.5 million.