Ocean drilling: Digging in
A new ship and a wave of funding will let scientists drill where they have never been able to drill before, from near the North Pole to the rocks lying beneath Earth's crust. Rex Dalton and David Cyranoski report.
Ocean drilling: in the zone.
The world's biggest, best-equipped research drilling vessel is about to set off on its first scientific voyage. David Cyranoski previews its quest to catch a formidable earthquake in the act.
Natural gamma-ray spectrometry in hydrocarbon-bearing sandstones from the Norwegian Continental Shelf
Abstract 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.