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Open access

Barbara Tomaszewska and Leszek Pająk

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.

Open access

Barbara Tomaszewska and Leszek Pająk

Streszczenie

Woda obiegowa w instalacjach ciepłowniczych musi posiadać odpowiednie parametry fizykochemiczne, uzależnione od wymagań technicznych producentów urządzeń, przez które przypływa. Nie powinna powodować powstawania kamienia kotłowego, pienić się oraz korozyjnie oddziaływać na elementy instalacji.

W pracy przedstawiono badania dotyczące oceny możliwości wykorzystania odpadowych wód termalnych w celu uzupełnienia ubytków wody sieciowej w największym polskim geotermalnym systemie ciepłowniczym zlokalizowanym w obrębie niecki podhalańskiej. Obszar ten cechuje się dużymi zasobami wód termalnych, a jednocześnie deficytem wód zwykłych. Odpadowe wody termalne ze względu na wykazywane parametry fizykochemiczne mogą być wykorzystane w systemie dopiero po uzdatnieniu. Podczas badań zagospodarowana i uzdatniana była jedynie część całkowitego strumienia wody geotermalnej (do 5 m3/h), odpowiadająca mniej więcej zapotrzebowaniu systemu ciepłowniczego na świeżą uzdatnioną wodę obiegową (ok. 550 m3/miesiąc). Ubytki wody sieciowej wynikają z nieszczelności sieci, prowadzenia remontów, modernizacji lub obsługi sieci. Oczyszczanie przeprowadzone zostało z wykorzystaniem procesów membranowych w zintegrowanym systemie złożonym z ultrafiltracji (UF) i dwóch niezależnych stopni odwróconej osmozy (RO-1 i RO-2) połączonych szeregowo. Uzdatnianie prowadzone było przy częściowym wykorzystaniu artezyjskiego ciśnienia złożowego, co pozwoliło zredukować moc pomp obiegowych eliminując zużycie energii o około 0,7-0,9 kW. Dzięki pod­wyższonej temperaturze wody uzdatnionej zredukowana została moc cieplna o około 30 kW oraz efektywniej prowadzone były procesy oczyszczania i odgazowania wody. Uzyskano redukcję: zawartości żelaza ze stężenia około 4 do 0,013 g/m3, twardości ogólnej z 13,5 val/m3 do <0,02 val/m3, zasadowości z 4,45 val/m3 do <0,01 val/m3, fosforanów z 0,03 do <0,006 g/m3, uzyskując spełnienie wymagań określonych w normach, co po korekcie pH i odgazowaniu pozwala wykorzystać uzdatnione wody geotermalne dla uzupełnienia ubytków wody sieciowej w systemie ciepłowniczym.

Polska Norma PN-85/C-04601 nie specyfikuje wymagań w zakresie dopuszczalnego stężenia m.in. chlorków i siarczanów w wodzie obiegowej, a więc anionów wpływających nakorozyjność wody, głównie wżerową. Jony te tworzą rozpuszczalne związki z metalami, utrudniając powstawanie i wytrącanie tlenków metali. Zastosowanie przedstawionej technologii membranowej w odsalaniu wód termalnych pozwoliło na uzyskanie wysokiego stopnia retencji. Wynosi on dla chlorków 97% po RO-1 i 99 % po RO-2, natomiast dla siarczanów 99% już po RO-1.

Open access

Wioleta Olszewska, Agnieszka Miśkiewicz, Grażyna Zakrzewska-Kołtuniewicz, Leszek Lankof and Leszek Pająk

Abstract

Safety of radioactive waste repositories operation is associated with a multibarrier system designed and constructed to isolate and contain the waste from the biosphere. Each of radioactive waste repositories is equipped with system of barriers, which reduces the possibility of release of radionuclides from the storage site. Safety systems may differ from each other depending on the type of repository. They consist of the natural geological barrier provided by host rocks of the repository and its surroundings, and an engineered barrier system (EBS). The EBS may itself comprise a variety of sub-systems or components, such as waste forms, canisters, buffers, backfills, seals and plugs. The EBS plays a major role in providing the required disposal system performance. It is assumed that the metal canisters and system of barriers adequately isolate waste from the biosphere. The evaluation of the multibarrier system is carried out after detailed tests to determine its parameters, and after analysis including mathematical modeling of migration of contaminants. To provide an assurance of safety of radioactive waste repository multibarrier system, detailed long term safety assessments are developed. Usually they comprise modeling of EBS stability, corrosion rate and radionuclide migration in near field in geosphere and biosphere. The principal goal of radionuclide migration modeling is assessment of the radionuclides release paths and rate from the repository, radionuclides concentration in geosphere in time and human exposure to ionizing radiation

Open access

Barbara Tomaszewska, Leszek Pająk and Michał Bodzek

Abstract

M embrane-based water desalination processes and hybrid technologies are often considered as a technologically and economically viable alternative for desalination of geothermal waters. This has been confirmed by the results of pilot studies concerning the UF-RO desalination of geothermal waters extracted from various geological structures in Poland. The assessment of the feasibility of implementing the water desalination process analysed on an industrial scale is largely dependent on the method and possibility of disposing or utilising the concentrate. The analyses conducted in this respect have demonstrated that it is possible to use the solution obtained as a balneological product owing to its elevated metasilicic acid, fluorides and iodides ions content. Due to environmental considerations, injecting the concentrate back into the formation is the preferable solution. The energy efficiency and economic analysis conducted demonstrated that the cost effectiveness of implementing the UF-RO process in a geothermal system on an industrial scale largely depends on the factors related to its operation, including without limitation the amount of geothermal water extracted, water salinity, the absorption parameters of the wells used to inject water back into the formation, the scale of problems related to the disposal of cooled water, local demand for drinking and household water, etc. The decrease in the pressure required to inject water into the formation as well as the reduction in the stream of the water injected are among the key cost-effectiveness factors. Ensuring favourable desalinated water sale terms (price/quantity) is also a very important consideration owing to the electrical power required to conduct the UF-RO process.

Open access

Maciej Miecznik, Anna Sowiżdżał, Barbara Tomaszewska and Leszek Pająk

Abstract

The Chociwel region is part of the Szczecin Trough and constitutes the northeastern segment of the extended Szczecin-Gorzów Synclinorium. Lower Jurassic reservoirs of high permeability of up to 1145 mD can discharge geothermal waters with a rate exceeding 250 m3/h and temperatures reach over 90°C in the lowermost part of the reservoirs. These conditions provide an opportunity to generate electricity from heat accumulated in geothermal waters using binary ORC (Organic Rankine Cycle) systems. A numerical model of the natural state and exploitation conditions was created for the Chociwel area with the use of TOUGH2 geothermal simulator (i.e., integral finite-difference method). An analysis of geological and hydrogeothermal data indicates that the best conditions are found to the southeast of the town of Chociwel, where the bottom part of the reservoir reaches 3 km below ground. This would require drilling two new wells, namely one production and one injection. Simulated production with a flow rate of 275 m3/h, a temperature of 89°C at the wellhead, 30°C injection temperature and wells being 1.2 km separated from each other leads to a small temperature drop and moderate requirements for pumping power over a 50 years’ time span. The ORC binary system can produce at maximum 592.5 kW gross power with the R227ea found as the most suitable working fluid. Geothermal brine leaving the ORC system with a temperature c. 53°C can be used for other purposes, namely mushroom growing, balneology, swimming pools, soil warming, de-icing, fish farming and for heat pumps.

Open access

Wiesław Bujakowski, Antoni Barbacki, Maciej Miecznik, Leszek Pająk and Robert Skrzypczak

Abstract

The main objective of this study was to develop a spatial temperature distribution of the Karkonosze Pluton to indicate optimum locations for HDR systems at drillable depth.

HDR geothermal technology makes it possible to extract heat from the Earth in areas where no hydro-geothermal resources are present. To produce electricity in a binary cycle, system temperatures of > 100°C are usually required. In this paper, the authors have analysed the potential opportunities for applying HDR technology in the area of the Karkonosze Pluton, which is regarded as an optimum location for the application of the HDR concept (due to the potential for stimulation offered by the mechanical properties of the granites, radiogenic heat production, modern tectonic activity, and the thickness of the pluton). The model used in the analysis, which takes into account a hypothetical assessment of the manner and paths of fluid migration within the pluton, provides an insight into the spatial distribution of subsurface temperatures. It thus allows the location of relatively shallow high-temperature zones, which are optimal for the efficient application of HDR technology, to be identified. With respect to this technology, the Szklarska Poręba area and the NE part of the pluton seem to be better targets than the Cieplice central area, where the model indicated much lower temperatures (e.g. at a depth of 5,000 m, estimated temperatures in the vicinity of Szklarska Poręba were about 185°C and in the vicinity of Cieplice they were about 140°C).

Open access

Marta Dendys, Barbara Tomaszewska and Leszek Pająk

Abstract

Nowadays, numerical modelling is a common tool for supporting the research of geothermal systems. Due to the development of computer sciences and access to software dedicated to numerical modelling of hydrogeological processes this is possible. Research can schematise hydrogeological conditions and simulate the work of geothermal systems and thermal water intakes. Research creates numerical models of geothermal systems at the regional and local scale for simulating work of specific thermal waters for example.

In connection with the economic development of the use of thermal waters in Poland there are many research projects where numerical modelling occurs as a primary tool. This paper provides an overview of research issues where the solution to the problem was found by using computer applications and numerical simulators.