Injection of Thermal Water into Porous Reservoirs

Abstract

The injection of heat-depleted brines into clastic sedimentary reservoirs with clay, sand and sandstone sequences has long been reported as a sensitive matter by petroleum and geothermal operators (Ungemach, 2003). The safe reinjection of low-enthalpy geothermal fluids into sandstone has posed a very serious professional problem impeding the utilization of geothermal energy. As stressed by various authors, the precise mechanisms that cause injectivity indexes to drop are not entirely understood. Although both international and domestic examples demonstrate that the injection of thermal waters into porous reservoirs is technically manageable, neither practical knowledge nor a professionally grounded and formalized policy is available at the moment that guarantees the success of reinjection into sandstone. Researchers at the University of Szeged aim to obtain uniform technological knowledge of the economic, safe and standardized procedure of reinjection of used thermal water into Pannonian sandstone.
The results of the first year of a 3 year study are presented, dealing mainly with test measurements of existing reinjection wells and modelling of sustainable operation of production-reinjection well pairs.