Projekt nr LIFE11 ENV/PL/000447/1

Projekt współfinansowany przez Unię Europejską ze środków Instrumentu Finansowego
dla Środowiska LIFE+ oraz Narodowy Fundusz Ochrony Środowiska i Gospodarki Wodnej

Introduction

Background of the project

Pyrzyce Geothermy is a high temperature heating plant – the temperature of extracted  brine is 64º C, facilitating direct use of the earth heat, which source is deposit geothermal water, filling the pores and crevices of rocks as brines of various degree of concentration. The heat from extracted thermal water is taken, and then after given the heat to water in heat exchanger, thermal water flow the pipeline to alloted  injection  wells GT-2 and GT-4 and there is cooled to a lower temperature. The depth of wells is 1640 m. Thermal water near Pyrzyce is highly mineralized (121 g/l, mainly NaCL).

Pyrzyce Geothermy, like most of Geothermal Heating Plants has problem with holding high productivity exploitation of thermal water. The basic problems of injection wells are progressive loss of productivity and efficiency of pumping and fast corrosion.

Four out of five Geothermal Heating Plants of high enthalpy water, functioning in the area of Poland, struggle with problem of assurance appropriate productivity assuring smoothness their action. Decrease of productivity and efficiency of the pumping and fast corrosion are related to injection wells problem.

The problems with pumping cooled thermal water back into indigenous ground water by injection wells are not only problems of polish Geothermal Heating Plants. These problems are in Europe and in the world in all Heating Plants pumping cooled thermal water back into indigenous aquifers and especially to pore collectors.

The problems in other countries

  • Germany

In Germany just like in Pyrzyce thermal water have very high mineralization. Mineralization in Neustadt-Gleve is 227 g/l and in Unterhaching about 100 g/l. The geothermal system in Neustadt-Glewe is an example of research on the soft acidizing method in order to repair the well and restore the absorbtion, which has decreased as a result of usage in the effect of the development of corrosion and precipitation. Similar problems also have other German Geothermal Heating Plants.

  • Austria

In Bad-Blumau, due to anxiety about colmatation of the injection well, inhibitors with cooled thermal water are injected. Utilized thermal water is injected back into the depth of 3000 m and its mineralization is 17,9 g/l.

  • France

Beeing the subject of the demonstration, the method of super soft acididizing is the modification of the soft acidizing method, which was tested in Paris basin.

It may also point to problems with pumping cooled thermal water in French Geothermal Heating  Plants. The heating plants exploiting here mainly Doggerian limestones (Middle Jurassic). Mineralization of these water oscillated in the range of 5-35 g/l. Exploitation of seams for heating purposes is run with doublets (in some cases with triplets ) relatively deep (1,5 - 2,5 km) wells, with the injection of cooled thermal water back into the reservoir). Due to the chemical composition of geothermal water, they have highly corrosive properties what escalating problems connected with exploatation the French Geothermal Heating. 

  • United States

The problem with injection cooled thermal water is in the geothermal fields in the Geysers in USA, where in the deposit layer are located geothermal steam. To make it available, it was made 400 geothermal wells to 3200 m depth.

 After give its energy the turbine the geothermal steam is condensed and again pumped to formation by 70 injection wells. In this case it can only pumped only 25 percent all condensed geothermal water.

At present there are leading intensive work, associated with improvement of absorption of the injection wells. Increasing the efficiency of injection condensates is necessary due to preservation of renewable the source.   

Previous researches and gained experience include:

Pyrzyce Geothermy to improve the absorption of the geothermal deposit layer introduced following methods of cleaning the injection wells:

  • In 2008 implemented the soft acidizing method (SA), which enables to remove the effects of colmatation, i.a. calcium carbonate (CaCO3) – likewise the standard acidity. Through injection to filter, zone, rock formation and aquifer a little concentration of injected hydrochloric acid – 0,1 – 0,2% it is not necessary to take the acid away and its neutralized. Dissolves in aquifer carbonates precipitating to filter and rock formation. This method improves the work of injection wells but its disadvantage was not rhytmic systematic applying endeavours – removal the causes and not prevention of incrustation.
  • Since 2009 the method of the soft acidizing has been enhancing in cooperation with MARCOR company – as the method of super soft acidizing (SSA) relaying on the constant dosage of significantly lower than defined in programme of the soft acidiacidization dosages of 30% deoxygenated hydrochloric acid with the addition of antiscale or dispersant to flowing brine before the filters and heat exchangers. Its aim is to prevention of developing and precipitating sediments from exploitation of geothermal water, thus, prevention of colmatation of reservoir zone in the injection wells. The method was designed to stabilize the pH of the brine and maintain of appropriate concentration of dissolved CO2 in the brine, by forcing the appropriate concentration of CO2 in the gas phase (as a result of the imbalance CaCO3 – CO2). In the method of SSA amount of dosed deoxygenated hydrochloric acid on the concentration of 30% is several dozen of grams of the acid per 1 m3 the brain. This method should be assisted by dosage of small doses of antiscale and/or dispersant, what allow to reduce the dose of the hydrochloric acid. In the method of SMK the process of degradation of the hydrochloric acid occurs only in the injecting pump (fast reaction) and not in the injection well or geothermal deposit layer.
  •  In 2010, based on the research on (SA) and (SSA), POLGEOL S.A. Company completed work on the project of geological work, leading up to the improvement of absorption of the geothermal deposit layer by performing techniques and dosing preparations conditioning for geothermal wells of  Pyrzyce Geothermia. This project along with instructions prepared by MARCOR represents the technical documentation necessary for realization of the objective project.