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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.
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Authors and Affiliations

Barbara Tomaszewska
Leszek Pająk
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Abstract

Geothermal waters are a source of clean energy. They should be used in a rational manner especially in energyand economic terms.

Key factors that determine the conditions in which geothermal waters are used, the amount of energy obtainedand the manner in which cooled water is utilised include water salinity. Elevated salinity levels and the presence oftoxic microelements may often lead to difficulties related to the utilisation of spent waters. Only a few Polishgeothermal facilities operate in a closed system, where the water is injected back into the formation after havingbeen used. Open (with water dumped into surface waterways or sewerage systems) or mixed (only part of the wateris re-injected into the formation via absorption wells while the rest is dumped into rivers) arrangements are morefrequently used. In certain circumstances, the use of desalinated geothermal water may constitute an alternativeenabling local needs for fresh water to be met (e.g. drinking water).

The assessment of the feasibility of implementing the water desalination process on an industrial scale islargely dependent on the method and possibility of disposing of, or utilising, the concentrate. Due to environmentalconsiderations, 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 desalinationprocess 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 ofthe 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 theformation 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 tothe electrical power required to conduct the desalination process

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Authors and Affiliations

Barbara Tomaszewska
ORCID: ORCID
Leszek Pająk
ORCID: ORCID
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Abstract

Direct applications in agriculture are among the most prospective development lines of geothermal water and energy. In many countries such uses have already been ongoing. Poland also has suitable natural conditions and geothermal waters’ potential for agricultural development as well as for applications related to agriculture. Moreover, such applications in agriculture – if taking place after earlier use of geothermal waters e.g. for energetic or other purposes – would be the realization of the idea of the closed cycle economy. The first research and development works on geothermal waters and energy applications in agriculture in Poland were carried out in the early 1990s. In recent years this subject has once again sparked a growing interest. The paper presents geothermal water resources potential as well as circumstances, rationale, selected relevant estimations and proposed zones in the country for their uses (as raw material and heat source) in the agricultural sector of the country. The use of geothermal waters in agriculture would be an important element in the chain of agricultural production and agri-food processing, contributing to the increase in the use of locally available natural resources, as well as reducing emissions when using these resources for energetic purposes. The topic is presented against the background of a brief review of the state of geothermal water applications in agriculture in the world and in Europe, which convinces the legitimacy and need for the development of such use of geothermal water as a raw material for agriculture also in Poland.

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Authors and Affiliations

Robert Skrzypczak
Beata Kępińska
ORCID: ORCID
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Abstract

Poland belongs to the countries with limited waters intended for drinking resources. To meet this problem, the Management Board of Geotermia Mazowiecka SA carries out activities to determine the possibilities of using exploited geothermal waters other than energy purposes. In addition to energy, the geothermal water is used for recreation and balneotherapy in “Termy Mszczonów” and for the production of drinking water for the local water supply system. Some water needs to be discharged into surface watercourses due to a lack of coherence of heating and water supply needs. For recognizing this problem innovative research project entitled: “The development of a method for injecting after energy-used geothermal waters into selected geological structures” was prepared and implemented as part of the Regional Operational Program of the Mazowieckie Voivodship for 2014–2020 (Priority Axis: Research and development activities of enterprises). This project has resulted in the launch of the installation pumping excess water to the quaternary sandy leyer. Based on the results from the first year of operation of the project, it can be assumed that it is possible to achieve nearly 100% reduction of water discharge and, consequently, the full use of producted geothermal waters. In summary, it can be stated that the geothermal plant in Mszczonów is a unique installation not only on the Polish but also international scale. The proof of this is not only the scale of rational use of water for energy purposes (cooling from 41°C to about 17°C), but also their development in other areas, for example in “Termy Mszczonów” and for the production of waters intended for drinking. The article presents the results of the first year (2019) of operation of the water injection system. During this period, in cooled water discharged into surface watercourse nearly 50% reduction was achieved.

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Authors and Affiliations

Wiesław Bujakowski
ORCID: ORCID
Bogusław Bielec
ORCID: ORCID
Marek Balcer
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Abstract

This study aimed to indicate the variability range of parameter values describing the geomechanical properties of Carboniferous rocks depending on the moisture content of the laboratory sample. We assumed that the moisture content in the tested rock samples corresponds to various water saturation states in the rock mass. The states could be caused by complete and long-term drainage, water inflow, or the position of the rock sample to the ventilation ducts or the water table in flooded mine workings. In line with this assumption, measurements were made on samples of accompanying rock using two water saturation states of rock pores – moisture of samples, i.e., air-dried and capillary saturation states. Laboratory surveys were also made for the state of moisture of the coals obtained in the process of immersion of the sample in water. The air-dried state of rocks as standard in geomechanical tests in laboratories was compared with the surroundings of mining excavations, mostly ventilated ones, located within a long-term preserved depression cone, especially in hydrogeological covered areas. We used the capillary saturation state to demonstrate significant changes in the values of basic geomechanical parameters under the influence of the water from the surface and higher aquifers, circulating in the rock mass near groundwater reservoirs. Capillary saturation was the closest to natural moisture in the rock mass drained from free water. The coefficient of changes in the geomechanical properties of rocks associated with the change in moisture content and the transition of rocks from the air-dried state to the capillary saturation state was determined. The parameter was suitable for simulating probable changes in the values of geomechanical parameters of rocks and approximating the laboratory moisture content to the conditions occurring in the rock mass. Linear relationships were also developed with very good or good, and sometimes satisfactory coefficient determinations.
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Authors and Affiliations

Mirosława Bukowska
1
ORCID: ORCID
Przemysław Bukowski
1
ORCID: ORCID

  1. GIG Research Institute, 1 Gwarków Sq., 40-166 Katowice, Poland

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