Authors: Matolin, M.; Abraham, M.¹; Hanak, J.²; Kasparec, I.³; Stranik, Z.²

Source: Journal of Petroleum Geology, Volume 31, Number 1, January 2008 , pp. 97-108(12)

Publisher: Wiley-Blackwell

Abstract:

Oil at the Zdanice field in the SE Czech Republic is reservoired at a depth of 900 m in weathered Precambrian granitoids and Lower Miocene sandstones and conglomerates. Tertiary claystones, siltstones and sandstones form the top seal. Surface gamma-ray spectrometry carried out along two profiles across the field (6,880 m and 8,335 m in length, respectively) found perceptible decreases of K, U, and Th concentrations relative to background values. This can be explained in terms of enhanced leaching of these radionuclides by groundwater acids derived from hydrocarbons. Observed increases in radon and thoron in soil gas above the oil-producing zone at Zdanice may be caused by enhanced gas emanation from U- and Th-bearing minerals decomposed by groundwater acids. Laboratory analyses of 444 samples collected from 18 shallow boreholes (20 m deep) pointed to a trend of decreasing K, U and Th concentrations above the oil-producing zone at Zdanice. Decreases in rock porosity and organic carbon content were also noted together with an increase in mineralogical density, magnetic susceptibility and sulphur content. Petrophysical analyses of 330 samples from deep boreholes showed lower values of K and U in samples from oil-producing wells. These observations of minor petrophysical alterations in rocks overlying the Zdanice oilfield may be characteristic and may be applicable to hydrocarbon exploration operations elsewhere.

Keywords: Zdanice oilfield; Czech Republic; hydrocarbon fluids; radioactivity; geochemical and petrophysical profiles; hydrocarbon exploration

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1747-5457.2008.00408.x

Affiliations: 1: Geomin Cooperative Jihlava, Znojemská 78, 586 56 Jihlava, Czech Republic. 2: Czech Geological Survey, Leitnerova 22, 602 00 Brno, Czech Republic. 3: Exploranium CZ, Hudcova 56b, 621 00 Brno, Czech Republic.

Publication date: 2008-01-01

More about this publication?

• Editorial Board
• Information for Authors
• Subscribe to this Title
• ingentaconnect is not responsible for the content or availability of external websites

Related content

• In this: publication
• By this: publisher
• In this Subject: Geology ,  Mining & Metallurgy
• By this author: Matolin, M. ;  Abraham, M. ;  Hanak, J. ;  Kasparec, I. ;  Stranik, Z.

Website © Publishing Technology. Article copyright remains with the publisher, society or author(s) as specified within the article.

• Terms and conditions
• Privacy policy
• Information for advertisers