Petroleum geologists interpret sequence-stratigraphic architecture of prospective strata from several types of data, including well logs, 2-D and 3-D seismic records, cores, and outcrop analogs. Although this effort is most effective when they apply all data sets, well logs commonly compose the primary available data. The objective of this module is to impart a basic understanding of how to define sequences, systems tracts, and the key sequence-stratigraphic surfaces that divide them, using well logs. This exercise will give the user experience in identifying systems tracts and key sequence-stratigraphic surfaces within an upper Miocene, on-shelf interval in the Vermilion Block 50 gas field of offshore Louisiana. These Miocene rocks comprise lowstand (incised-valley fill), transgressive, and highstand systems tracts. Key stratigraphic surfaces that bound these systems tracts are erosional and/or nondepositional sequence boundaries, transgressive surfaces, and maximum flooding surfaces.

In this module, you will base your interpretations on spontaneous potential (SP), gamma-ray (GR), and deep-resistivity (ILD) log curves from five wells aligned approximately parallel to the Miocene shoreline. Using these well logs, you will learn to identify diagnostic stratal stacking patterns that record the major depositional processes involved in the cyclic rise and fall of relative sea level: aggradation, progradation, retrogradation, condensed sedimentation during maximum flooding of the shelf, and regional incision and erosion.