AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Chemical Stratigraphy: Feasibility of High Resolution Correlation - Outcrop Case Study of a Submarine Slope Channel Complex (Tabernas Basin, Spain)
(1) Department of Earth and Ocean Sciences, Liverpool, United Kingdom.
(2) Integrated Reservoir Solutions Ltd. (IReS), Ellesmere Port, United Kingdom.
Chemical stratigraphy is the application of whole-rock inorganic geochemical analyses to characterize and correlate strata, based on the recognition and interpretation of subtle variations in the bulk chemical composition of sedimentary rocks. In recent years it has become an important tool in enhancing correlation in subsurface reservoir successions in exploration industry. However this technique widely lacks integration with sedimentological-based stratigraphic correlation methods, e.g. lithostratigraphy, sequence stratigraphy. This study set out to examine the validity, accuracy and limitations of the chemostratigraphic technique as correlation tool with the aid of outcrop studies testing chemical stratigraphic correlations against sequence stratigraphic correlations.
An outcrop analogue study was undertaken in a Miocene submarine slope channel complex in the Tabernas Basin of southern Spain. The channel complex consists of several individual channel units and exhibits an overall thickness of >40m. Channel fill facies is composed of sandy conglomerates, coarse and medium grained sandstone, and sandy mudstones deposited by debris flows and high and low density turbidity currents respectively. The complex can be traced over several kilometres down the paleoflow, where it becomes less confined.
In order to investigate the relationships between chemical and mineral stratigraphy and the known physically mapped correlation of logged profiles; vertical sections have been sampled with a sampling density of 1-2 feet. ED-XRF and XRD-analyses of over 700 sandstone and mudstone samples were performed and complemented by optical microscopic, BSEM-, EDAX-, and CL-SEM analyses of a subset of samples.
The results are used to test if individual channel units can be distinguished from the chemical data. Comparison of elemental concentrations to mineral and petrographic data is aimed to link variations in geochemistry with changes in the bulk mineralogy and the heavy mineral assemblage. This, in turn, enables to assess chemical variations in the context of subtle provenance changes and variations in the depositional pattern. Furthermore the hypothesis has been tested that a chemostratigraphic continuity or profile is maintained down the palaeoflow direction within the channel system, based on the notion that the channel confines the higher density parts of the turbidity current and so might capture a correlatable geochemical profile at different points down the channel.