Five 3rd-order depositional sequences are interpreted from the early Albian to late Campanian interval in the Potiguar Basin. An integrated analysis of seismic interpretations, well logs, cores and biostratigraphic data provides a stratigraphic framework composed by stratigraphic surfaces, systems tracts and sequences. Depositional Sequence 1 and 2 are, respectively, Albian and early to mid-Cenomanian aged and are composed by the falling stage, low stand, transgressive and high stand systems tracts. Depositional Sequence 3 is late Cenomanian to mid-Turonian aged and is composed by the transgressive and high stand systems tracts. Depositional sequences 4 and 5 are, respectively, late Turonian to mid-Santonian and late Santonian to mid-Campanian aged and are composed only by transgressive and high stand systems tracts. The lack of falling stage and low stand systems tracts in depositional sequences 3, 4 and 5, as well the increasing in transgressive and highstand systems tracts thickness as depositional sequences get younger, are reflection of an overall transgressive trend of a 2nd-order sequence. The interpretation proposed in this paper correlates onshore with offshore deposits within a seismic scale (3rd-order) sequence stratigraphy framework. This approach allows a better understanding of the Açu Formation, the primary oil-bearing formation of the Potiguar Basin. The Açu Formation is part of depositional sequences 1, 2 and 3 and is characterized by lateral and vertical variations of depositional systems instead of being associated to a specific depositional system. This sequence stratigraphy analysis can be used as a low-resolution framework for future high-resolution (4th-order scale) studies.
Sequence stratigraphy is a method that unravels the evolution of sedimentation through time and space within sedimentary basins. Nowadays, the exploration and production of natural resources generated by or related to sedimentary processes depend on constructing a chronostratigraphic framework to identify sequences of distinct hierarchies. In clastic and carbonate successions, exploratory studies focus on higher-rank sequences to evaluate the potential of natural resources and to make discoveries. Conversely, lower-rank (i.e. high-frequency) sequences characterize and highlight the spatial and temporal occurrence of natural resource deposits and heterogeneities, necessary for optimizing production. For instance, high-resolution sequence stratigraphic surfaces may indicate the location of placer deposits or coal seams. In the petroleum industry, high-resolution sequence stratigraphy is applied in reservoir zonation and characterization, which are the stratigraphic essence of 3D geological and fluid flow models. Thus, this methodology can guide reservoir management, forecast and optimize production, and increase the ultimate recovery factor. Recent technological innovations such as virtual outcrop models and Ground Penetration Radar have promoted a significant advance in the visualization of surfaces and stacking patterns, making stratigraphic analysis more accurate and efficient than the traditional use of analogs.
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