Lyell Collection
Geological Society, London, Special Publications
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hurst, A.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Geological Society, London, Special Publications; 1990; v. 48; p. 211-222;
DOI: 10.1144/GSL.SP.1990.048.01.18
© 1990 Geological Society of London

Mineralogy and Geochemistry

Natural gamma-ray spectrometry in hydrocarbon-bearing sandstones from the Norwegian Continental Shelf

Andrew Hurst

Statoil, Postboks 300 Forus, 4001 Stavanger, Norway

Concentrations of thorium (Th), uranium (U) and potassium (K) are measured using natural gamma-ray spectrometry (NGS) logs. The precision of NGS measurements in sandstones varies: K measurement is in general moderately good; Th measurement varies with the service company involved; U measurement is unreliable. Concentrations of Th, U and K in standard tables of minerals used commonly in log evaluation are not representative of the actual elemental concentrations found in sandstone minerals. Th/K cross-plots are shown to be unsuitable for the identification of clay minerals in sandstones. Illite cement cannot under normal geological circumstances be identified from the K content of the rock. Authigenic kaolinite has no particular affinity for concentration of Th. Th in sandstones is concentrated predominantly in detrital heavy minerals with up to 200f the total Th present in silt-sized and finer authigenic REE-phosphates and Th salts. Variation in the K content of micas from some Jurassic sandstones demonstrates the need for using formation-specific chemical data for the minerals of interest (micas, feldspars, clay minerals) as input parameters in normative calculations. Appropriate statistical control of the validity of Th, U and K contents for specific minerals is required.





This article has been cited by other articles:


Home page
 Geological Society, London, Special PublicationsHome page
D. N. Parkinson
Gamma-ray spectrometry as a tool for stratigraphical interpretation: examples from the western European Lower Jurassic
Geological Society, London, Special Publications, 1996; 103: 231 - 255.
[Abstract] [PDF]