Metoda zpracovani teplotnich udaju zvrtu, jeji limity amoznosti zpresneni

One of the methods of processing temperature measurements in boreholes is the extrapolation procedure, developed and applied by J. Polášek as apart of the geothermal evaluation of the Všebořice area near Ústí nad Labem. This procedure is based on adivison of the measured temperature profile into sections (regions) based on its course and geological profile of the borehole. Using alinear regression, the best-fit lines through the measured temperature depth profiles are calculated for each of the regions. Subsequently, pair combinations of the best-fit lines of the individual regions of the measured temperature curve are generated, depending on the temperature depth profile of the particular borehole, and parameters of their extrapolation function are calculated. Based on the assessment and evaluation of the results of the calculation for each pair of regions of the measured temperature curves and the assessment of the geological structure at the borehole area, the appropriate pair combinations of the measured temperature curve regions are selected, for which the average of the extrapolation function values is calculated. This procedure is repeated for several other suitable pair combinations of the measured temperature curve regions. Values that show the lowest root mean square deviation from the measured temperatures, while respecting the geological structure in the borehole area, are considered the most suitable for extrapolating temperature to agreater depth.

Some temperature curves in boreholes processed using this procedure show aclose temperature gradient in all selected regions of the curve. In such boreholes, the total extrapolation function is astraight line. Common case is apresence of several successive regions of the curve with alinear pattern whose gradient gradually increases. The extrapolation function of such borehole temperature curve is represented by asecond degree polynomial.In some cases, however, several successive regions of the curve, each with alinear pattern, showed agradually decreasing gradient. Such extrapolation gives meaningless outputs and the causes of such aresult need to be searched for. This extrapolation can be in some cases and to acertain extent explained by the geological structure of the area. Due to the very limited knowledge of the deeper geological structure in the Czech Republic and also as the change of the temperature curve does not always have obvious geological causes, the risk of considerable inaccuracies in temperature determination at depth is high and definitely increases with extrapolation depth (length). Results of the extrapolation of temperature curves in boreholes are therefore only approximate.

Significant refinement of extrapolation of temperature measure-ments in boreholes deeper than 1km can be achieved, for example, by electromagnetic geophysical measurements with along reach, and by use of special methods of their geothermal inter- pretation.

References

Genter, A. et al. (2009): The EGS Soultz project (France): from reservoir development to electricity production. – 12 str. Annual Meeting of the Geothermal Resources Council, Reno, Nevada, USA.

Kirevichev, V. K. (2009): Predlozhenie po provedeniu rabot VRE-VP s celyu izucenia geotermalnoi zony vblizi g. Liberec (Chekhia). – 10 str. Interní materiál zpracovaný pro CVEVL, Geoněftěgaz. Moskva.

Kloz, M. – Hochm anová, A. – Petržílek, P. – Polášek, J. – Pošmourný, K. – Rybář, Z. – Schenk, V. – Šebek, V. (2016): Výzkum využití geotermální energie v lokalitě Všebořice. Studie pro ČEZ. – 468 str. MS Centrum pro výzkum energetického využití litosféry, v. v. i. Liberec.

Kloz, M. – Pošmourný, K. (2012): Revize geotermických map ČR pro vyčlenění geotermicky vhodných oblastí v hloubkové úrovni kolem 5 km. Podkladová studie pro projekt ReStEP. – 35 str., přílohy. MS ČZU. Praha.

Kloz, M. – Málek, J. – Pošmourný, K. (2019: Vstupní geologická a geotermická analýza možností využití hlubinné geotermální energie v Pardubickém kraji. Studie pro Krajský úřad Pardubického kraje. – 468 str. MS Centrum pro výzkum energetického využití litosféry, v. v. i. Liberec.

Kořalka S. (2007): Karotážní měření na vrtu PVGT-LT-1. Zpráva. Části 1, 2. – 80 str. MS Aquatest a Geomedia. Praha.

Lahodný, P. – Vašinová, J. – Šrámek, J. (1984): Gravimetrické měření v měřítku 1 : 25 000 mezi Louny, Lovosicemi a Děčínem – MS Čes. geol. služba. Praha.

Myslil, V. – Karous, M. – Pačes, T. – Motlík, J. – Pošmourný, K. (2011): Geotermální energie. Zdroje, využití, technologie. – 185 str. Geoterm CZ. Liberec.

Pošmourný, K. – Coubal, M. – Valenta, J. (2018): Utilization of deep geothermal energy in the Czech Republic: possibilities, present state and prospects. – Geotechnika 1, 10–18.

Procházka, M. (2009): Contribution of well logging for exploitation of geothermal energy. – 35 str. MS Referát na semináři CVEVL. Liberec.

Spichak, V. – Zakharova, O. (2012): The subsurface temperature assessment by means of an indirect electromagnetic geothermometer. – Geophysics 77, 4, 179–190.

Spichak, V. V. – Zakharova, O. K (2013): Elektromagnitnyi geotermometr. – 172 str. Naučnyj mir. Moskva.

Žáček, V. – Škoda, R. (2009): Petrology of crystalline rocks in the geothermal borehole GTPV-LT1 in Litoměřice. – Geosci. Res. Rep. for 2008, 205–212. (in Czech).