Chemostratigraphy of Upper Carboniferous (Pennsylvanian) Sequences from the Southern North Sea (United Kingdom)

Abstract

Important gas reservoirs occur in the Upper Carboniferous coal measures and red beds of the Southern North Sea. The thick red beds of the Boulton and Ketch formations are difficult to correlate, due to poor internal seismic definition, repetitive e-log signatures, and their barren nature. Although the underlying coal measures of the Westoe, Cleaver, and Caister Formations have better seismic resolution and contain palynomorphs, coals that die out laterally and the lack of diagnostic taxa over certain intervals contribute to their correlation being problematical. However, the application of chemostratigraphy to more than sixty wells from numerous fields in UK Quadrants 44 and 49, as well as from Dutch sector Blocks E, F, and K, allows the establishment of an independent, robust, detailed correlation framework for the aforesaid red beds and coal measures.Presented in this paper are correlative chemostratigraphic reference sections for the Caister, Westoe, Cleaver, Ketch, Boulton, and Step Graben formations. The chemostratigraphic zonations erected for these formations are based on variations in silty claystone geochemistry that can be tied to changes in provenance, climate, and depositional environment. In addition, the zonations are supported by stratigraphic changes in sandstone and coal geochemistry, the geochemical correlation of tonsteins and marine bands, and the recognition of different types of paleosol in the above formations.The chemostratigraphic correlation framework enables specific broad intervals ("packages") to be correlated between fields and is also used to constrain seismic correlations with a view to highlighting potential exploration targets. Furthermore, the same framework allows much thinner intervals ("units" and "subunits") to be correlated within fields: these smaller-scale correlations enhance reservoir correlations with respect to the development of fields such as Boulton, Schooner, Tyne, Ketch, and Topaz. In addition to using inorganic geochemical data to characterize and correlate sedimentological packages, data can also used to identify and correlate marker horizons and surfaces (tonsteins, coals, marine bands, major paleosols), which may be highly correlative low-diachrony surfaces, which greatly enhance the overall validity of the stratigraphic correlation scheme.

Using Elemental Chemostratigraphy on Mid–Late Frasnian Platform-Top Successions from the Lennard Shelf Outcrops, Canning Basin, Western Australia

“…This, the authors argue, negates changes in elemental composition that reflect gross lithological changes, thereby allowing more subtle variations in elemental chemistry that reflect provenance, climate, etc., to be recognized in lithologically similar facies. Furthermore, authors commonly argue for normalization of elements against Al 2 O 3 to minimize the effect of changes in silt and clay contents of lithologies (Van der Weijden 2002; Pearce et al 2005Pearce et al , 2010Ratcliffe et al 2015), although the validity of this approach has recently been questioned (Lowey 2015). These approaches proved problematic within the intricately mixed carbonate and siliciclastic lithologies of this study.…”

Sedimentology and stratigraphy of an intra-cratonic basin coal seam gas play: Walloon Subgroup of the Surat Basin, eastern Australia

“…However, there is a marked disconnect in the Taroom Coal Measures. compared geochemical signatures in adjacent sections or wells (Jarvis & Jarvis 1992a, b;Pearce et al 2010). IEC is routinely used within the petroleum industry due to large datasets being acquired from small sample volumes either within the laboratory or at wellsite.…”

Tracing provenance and pathways of late Holocene fluvio-deltaic sediments by heavy-metal spatial distribution (Po Plain–Northern Apennines system, Italy)

“…Among the mutually interacting variables that may influence sediment composition, sediment provenance and grain size have been observed to represent the major controlling factors of spatial metal distribution in sediments (Salminen & Tarvainen 1997;Ruiz 2001;Pearce et al 2010a). The following sections document to what extent the spatial distribution of selected trace metals from crevasse, levee and floodplain sediments of the Po Plain can reveal information about the depositional facies and source areas.…”