Dynamics of clogging processes in injection wells used to pump highly mineralized thermal waters into the sandstone structures lying under the polish lowlands

Abstract

When identifying the conditions required for the sustainable and long-term exploitation of geothermal resources it is very important to assess the dynamics of processes linked to the formation, migration and deposition of particles in geothermal systems. Such particles often cause clogging and damage to the boreholes and source reservoirs. Solid particles: products of corrosion processes, secondary precipitation from geothermal water or particles from the rock formations holding the source reservoir, may settle in the surface installations and lead to clogging of the injection wells. The paper proposes a mathematical model for changes in the absorbance index and the water injection pressure required over time. This was determined from the operating conditions for a model system consisting of a doublet of geothermal wells (extraction and injection well) and using the water occurring in Liassic sandstone structures in the Polish Lowland. Calculations were based on real data and conditions found in the Skierniewice GT-2 source reservoir intake. The main product of secondary mineral precipitation is calcium carbonate in the form of aragonite and calcite. It has been demonstrated that clogging of the active zone causes a particularly high surge in injection pressure during the fi rst 24 hours of pumping. In subsequent hours, pressure increases are close to linear and gradually grow to a level of ~2.2 MPa after 120 hours. The absorbance index decreases at a particularly fast rate during the fi rst six hours (Figure 4). Over the period of time analysed, its value decreases from over 42 to approximately 18 m3/h/MPa after 120 hours from initiation of the injection. These estimated results have been confi rmed in practice by real-life investigation of an injection well. The absorbance index recorded during the hydrodynamic tests decreased to approximately 20 m3/h/MPa after 120 hours.

Modelling geothermal conditions in part of the Szczecin Trough – the Chociwel area

“…The model does not consider chemical processes occurring in the aquifer, i.e. precipitation and dissolution of rock-forming minerals either, which can have a significant impact on doublet performance (Tomaszewska & Pająk, 2012). Cooling of the reservoir layers will only take place in the zone adjacent to the injection well and the zone defined by the groundwater flow between the wells (Fig.…”

“…In many parts of the world both basic research, in order to understand geological structures better (Chowaniec, 2009;Zuber & Chowaniec, 2009;Sowiżdżał, 2010Sowiżdżał, , 2012Stankowski, 2012;Özgür & Çalışkan, 2013;Sowiżdżał et al, 2013;Pussak et al, 2014), but also works aimed at optimisation of geothermal systems in terms of their operation have been carried out (Tomaszewska & Pająk, 2012;Żbikows-ka et al, 2013;Demir et al, 2014;Baba et al, 2015). Fundamental issues are, for instance, geothermal potential estimates assisted by numerical modelling (Szczepański & Szklarczyk, 2006) and analysis of geochemical composition of groundwaters in the context of scaling and corrosion prediction in geothermal systems.…”

A Structural-Thermal Model of the Karkonosze Pluton (Sudetes Mountains, SW Poland) for Hot Dry Rock (HDR) Geothermal Use

“…The operation of HDR systems is often associated with the clogging of injection wells (particulary in Enhanced Geothermal Systems using natural hot brine). Although this process is not the subject of the present investigations, the increase in the injection pressure required creates serious issues during system operation (Bujakowski et al, 2008, Tomaszewska, 2008Tomaszewska & Pająk, 2012;2013a, b). However, owing to the low mineralisation of water in the area of the Sudetes region investigated, these problems should not significantly obstruct the operation of HDR systems located there.…”

Assessment of possibilities of electricity production in flash geothermal system in Poland

“…Systems based on deep hydrothermal resources as well as on shallow groundwater and rock formations (heat pumps) have successfully been exploited [2,3,5,16,19].…”