Publications

Most of the essential elements and processes that create a petroleum system are controlled by the lithology and stratigraphy of the rock package involved. The vertical and lateral distribution of source, carrierheservoir, and migrational-barrier/trapseal rocks generally reflects an orderly pattern of lithoiogic and environmental facies that represent sequences of transgressive-regressive or deepeningshallowing water sedimentation. In cross section, these seuuences are commonly represented by unconformity-boundeC& wedge-shaped bodies of sediment that thin from depositional basin centers toward edges of non-deposition and erosion on bordering highlands.An ",ideal", depositional sequence contains an internal distribution of source rock, carrier/reservoir, and seal units. Overburden depths that cause source rock maturity may be produced by the thickness of overlying beds within the sequence itself or in an overlying sequence. Migration paths may be either upward and cross-stratal or lateral and updip within a given carrierlreservoir unit. Migrahon may continue until either a site of entrapment is reached within a reservoir indigenous to the sequence or a ",leak", is encountered into an overlying sequence or to the Earth's surface. Stratigraphic and structural traps may be present within a sequence as a result of depositional complexity and syn-depositional deform ation. Po st-depo sitional structural trap configurations may also be superimposed on a sequence.Not all sequences contain the stratigraphic elements that make petroleum systems, nor do they have the same lithologic geometries. Sequences may be barren of hydrocarbons due to source rock immaturity or leakage. Understanding how required elements of a petroleum system are represented within a depositional sequence should aid in explaining and predicting where oil and gas accumulations are found.Examples of petroleum systems related to depositional sequences will be presented.