INTEGRATED WHOLE-ROCK TRACE-ELEMENT GEOCHEMISTRY AND HEAVY MINERAL CHEMISTRY STUDIES - AIDS TO THE CORRELATION OF CONTINENTAL RED-BED RESERVOIRS IN THE BERYL FIELD, UK NORTH-SEA

Correlating continental red-bed successions in the sub-surface is a co mmon problem for the hydrocarbon industry. These successions are typic ally barren of fauna and often monotonous, leading to non-diagnostic w ire-line log signatures. A high-resolution, high precision study of de trital garnet chemistry within Triassic reservoir sandstones from the Beryl Field of the North Sea failed to subdivide the sequence satisfac torily. However, the whole-rock concentrations of immobile trace eleme nts such as Zr, Nb and Cr can be shown to be controlled primarily by t he abundances of the heavy minerals zircon, rutile and chrome-spinel, respectively. The chemistry of detrital rutile and chrome spinel varie s widely within any one sample, implying that the whole-rock concentra tions of Nb and Cr are also a function of the chemistry of these heavy minerals. Having calibrated a type well with a detailed mineralogical and geochemical study, it was possible to correlate between wells usi ng whole-rock geochemical cross-plots.