About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract

AAPG Bulletin, V. 96, No. 10 (October 2012), P. 19811996.

Copyright copy2012. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/04021211142

Thermal effects of Zechstein salt and the Early to Middle Jurassic hydrothermal event in the central Polish Basin

Gary W. Zielinski,1 Pawel Poprawa,2 Jan Szewczyk,3 Izabella Grotek,4 Hubert Kiersnowski,5 Robyn L. B. Zielinski6

1Omegalink International Ltd., P.O. Box 2152, Campton, New Hampshire; [email protected]
2Polish Geological Institute, Polish Geological Survey, 4 Rakowiecka Street, Warsaw, Poland; [email protected]
3Polish Geological Institute, 4 Rakowiecka Street, Warsaw, Poland; [email protected]
4Polish Geological Institute, Polish Geological Survey, 4 Rakowiecka Street, Warsaw, Poland; [email protected]
5Polish Geological Institute, Polish Geological Survey, 4 Rakowiecka Street, Warsaw, Poland; [email protected]
6Omegalink International Ltd., P.O. Box 2152, Campton, New Hampshire; [email protected]

ABSTRACT

Deep gas potential in the Polish Basin may factor significantly in European geopolitics, and thermal effects can influence that outcome there and elsewhere. Deep (gt3 km [9843 ft]) well data from the Kujawy area of the central Polish Basin reveal average geothermal gradient (36degC/km), thermal conductivity of Mesozoic strata (k = 2.29 W/m K), and present-day heat flow (Q = 82.4 mW/m2) that is 3% less than that obtained using the entire borehole. The extrapolated surface temperature (–6.2degC) is in good agreement with temperatures during the Weichselian glaciation. The thermal conductivity of the Upper Permian Zechstein (4.89 W/m K) is in good agreement with values from the North Sea and northern Germany. Steady-state heat-flow theory (one-dimensional [1-D]) predicts present-day temperature (199degC) at the base of Zechstein cap rock at 6-km (19,685-ft) depth in Kujawy. This is reduced just more than 10degC by low Zechstein thermal gradients (16.8degC/km). Because of thermal refraction, two-dimensional and three-dimensional models of Zechstein salt pillows can significantly negate this cooling effect; however, such effects appear absent in the Kujawy wells studied.

A widespread Early to Middle Jurassic (sim195–175 Ma) hydrothermal event appears to have reached maximum in the Kujawy area. A 455degC paleotemperature at 7-km (22,966-ft) depth (Carboniferous) is predicted by 1-D conductive heat transfer; however, geologic evidence does not support this result. The discrepancy is reconciled by convective heat transfer with upward fluid flow (3.3 times 10–10 m/s [10.8 times 10–10 ft/s]), resulting in a maximum paleotemperature of 273degC at 7-km (22,966-ft) depth, despite a paleoheat flow of 142 mW/m2. The trend of intensity of the hydrothermal event correlates with the present-day heat-flow trend. Hydrothermal event sites are subparallel to the major northwest-southeast structural and regional heat-flow trend, whereas other sites as close as 14 km (45,932 ft) and without hydrothermal event are not. The decay of the hydrothermal event is consistent with localized cylindrical plumes (10-km [32,808-ft] radius) that cool by conduction. Results suggest a long-term (sim185 m.y.) structural control on heat flow. Linear regression to vitrinite paleotemperatures yields a 185-Ma Jurassic surface temperature of approximately 21.3degC that is approximately 13degC higher than the present-day temperature for Warsaw, Poland. The duration of maximum reservoir and source rock paleotemperature (lt50 m.y.) is contrary to the kinetics of nitrogen and CO2-producing wells. Equilibrium thermodynamics predicts approximately 60% methane for present-day Kujawy reservoirs, with considerable uncertainty that should be removed by anticipated new deep drilling.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24

AAPG Member?

Please login with your Member username and password.

Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].