Reference Logs for Cotton Valley and Louark Stratigraphic Groups, North Louisiana: A Pilot Study

Consistent and well constrained stratigraphic nomenclature as published in charts, maps, and atlases is crucial for successful exploration and management of natural resources. These kinds of references are typically issued and maintained by geological surveys and bureaus. However, at present much of north Louisiana subsurface stratigraphy is inadequately documented in the form of a comprehensive, easily accessible reference base.

The present study attempts to remedy this deficiency by compiling an atlas of reference stratigraphic logs for Louisiana oil & gas fields. In particular, it begins by designating reference localities for the Jurassic interval of the Louisiana subsurface. Attention is first focused upon the Cotton Valley and Louark stratigraphic groups in selected north Louisiana oil & gas fields, including Carterville, Cotton Valley, and Ivan.

The reference log for an individual field is constructed from geological and geophysical data from intra-field oil & gas wells and by correlation to neighboring fields. The kernel data are open-hole electrical logs and drill cuttings; these data are augmented by other geophysical profiles and drill cores, wherever available. Reference well selection is based upon data quality, well location and total depth (TD), and similarity of geophysical profiles to those of field mate wells. The result is a graphic representation of the reference log with lithostratigraphic tops picked according to nomenclature established in publications and by common use. Intra-field correlations and extension to neighboring fields permits refinement of the full stratigraphic nomenclature with respect to historical naming conventions while minimizing name revisions or additions.