The application of whole-rock geochemistry and mineral chemistry to the correlation of mesozoic reservoirs within the Alwyn area, N. North Sea
Mesozoic reservoirs in the Alwyn Area, N. North Sea, contain ephemeral/perennial fluvial depositions and associated flood plain fines deposited in a semi-arid environment. Such successions are typically barren of fauna and monotonous in respect to t heir lithologies, which results in non-diagnostic wire-line log signatures. This study proves the application of whole-rock geochemistry and mineral chemistry as an additional correction tool for such successions in 13 wells in the Alwyn Area. The geological and sedimentological environments and conditions were established from sedimentological reports provide by TotalFinaElf Exploration UK (TFE) and from core studies undertaken during this study. Thirty-nine thin sections were analysed to investigate the mineral abundance in order to identify probable host minerals of the analysed chemical elements (ICP database provided by TFE and 202 XRF analyses in this study). Distinguishing between autochthonous and allochthonous mineral content enables one to establish the processes that have modified the entire mineralogical and geochemical composition of the source rock. The chemical elements themselves have been considered with particular regard to their mobility in aqueous fluids. It has been demonstrated that some of the immobile elements in this study are associated with particular heavy minerals. Some elements (though not attributed to particular minerals) show significant, correlatable geochemical signatures. The whole-rock geochemistry and the mineral chemistry of certain heavy minerals are used for provenance studies and chemostratigraphic correlation approaches. In combination with Sm-Nd provenance ages from other studies and available data from literature possible provenances are identified. Ratios between immobile elements are presented as down-hole logs. Twenty-five chemostratigraphic units are established on which basis 13 of 14 wells could be correlated in field wide correlation schemes.