A power producing system includes a source of geothermally heated fluid having inorganic salts dissolved therein. The fluid is directed through a first direct contact heat exchanger in heat transfer relation with a working fluid of a type insoluble in a liquid including inorganic salts. The vaporous working fluid thus produced is expanded through a prime mover and then directed through a second direct contact heat exchanger. The vaporous fluid is condensed in said second direct contact heat exchanger by passing in heat transfer relation with a relatively cold heat exchange medium comprising a liquid brine solution. The condensed working fluid is thereafter returned to the first direct contact heat exchanger for repeated reuse in the cycle. Inorganic salts are mixed with either the geothermal heated fluid or the relatively cold heat exchange medium to maintain the percentage by weight of inorganic salt in each of the fluids above a predetermined value to prevent the working fluid from being absorbed therein.