Geological, Hydrogeological and Technological Conditions of the Use of Production-Injection Systems in the Lower Jurassic (Liassic) Reservoir Horizons of the Polish Lowland

Abstract

The paper tackles the problems related to the assessment of the possibility of exploitation of identified geothermal resources. The conditions of geothermal waters extraction in the Lower Jurassic complex (formation) in Polish Lowland have been determined. Utilization of identified geothermal water resources is conditioned by the cost of completion of a geothermal installation, amount of recovered heat and efficiency of its exploitation. The specificity of the variations in the geological setting of the given study area required sound analysis of structural, lithological, petrophysical, hydrogeological and hydrochemical conditions in order to appropriately select a geothermal system both in its underground and aboveground parts. A geothermal installation based on a two-well geothermal system (the so-called geothermal doublet), in which the first well operates as a production well and the other as an injection well, was presented. A concept of a single-well geothermal installation with production-injection technological systems was proposed as a competitive solution that significantly reduces installation costs. Technological schemes of the aboveground and underground parts were presented with regard to doublet systems and single-well systems. The specific character of the technology of thermal water extraction from the Lower Jurassic complex was taken into account. In the discussed complex there is usually observed subartesian pressure, which negatively affects the wells and aboveground part of the geothermal installation and, as a consequence, creating unfavourable hydrochemical phenomena that have an impact on the water flow process. Based on the available data, the ranges of the basic values of geological parameters which can be related to the basic technical parameters of geothermal wells are listed.