Development of Predictive Stratigraphy—Sequences, Source-to-Sink, and Back to Seismic
Ole J. Martinsen, Tor O. Sømme, Audun Groth, "Development of Predictive Stratigraphy—Sequences, Source-to-Sink, and Back to Seismic", Sequence Stratigraphy: The Future Defined, Bruce Hart, Norman C. Rosen, Dorene West, Anthony D’Agostino, Carlo Messina, Michael Hoffman, Richard Wild
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Predictive stratigraphy developed in the 1950s and 60s through the breakthrough work of Larry Sloss and Harry Wheeler. The major change from previous work was an understanding of time stratigraphy and major breaks in stratigraphic sequences. With the advent of new technology, such as high-resolution logging, coring, seismic, and remote sensing, succeeding decades were dominated by drastic progress of new methods and geological understanding, namely facies analysis and seismic and sequence stratigraphy. Offshore exploration required predictive methods to be developed because wells in these basins had very high costs in contrast to onshore basins and were technically very challenging to drill, so that offshore basins and plays were best investigated using “remote” methods.
Seismic and sequence stratigraphy are extremely powerful techniques for understanding the fill of sedimentary basins but have been incorporated to a lesser degree in onshore sediment source areas. A common theme for breakthroughs in geology has been the development of new technology. Many new concepts have developed in the wake of new geophysical methods.
Remote sensing technology using satellites came into the public domain in the 1990s after the large military campaigns during the 1980s. This was a quantum leap in the ability to retrieve quantitative geomorphic and topographic data efficiently from onshore regions. While classic geomorphological techniques had been in use for decades, they were largely analog and constrained to analysis of topographic maps. Digital onshore data allowed for breakthrough analysis of onshore geomorphology, drainage, bedrock, and water and sediment flux to offshore basins.
The ability to combine the quantitative onshore data with offshore data (such as seismic) allowed for a new predictive methodology to develop based on semiquantitative and integrated analysis of entire, linked onshore and offshore systems. The technique, termed source-to-sink, built on studies from the early 1980s regarding sediment flux to modern offshore basins. The early techniques, however, did not consider stratigraphy and had little predictive power. Various source-to-sink methods developed, both experimental computer-based modeling, and geomorphic-based, but initial methods were not tuned to be used in exploration due to using data and methods not suited and aligned to conventional exploration data. A simpler more morphological approach thus developed that allowed for predictive analysis based on onshore remote sensing data and conventional offshore seismic. Source-to-sink analysis complements sequence stratigraphy rather than replacing it. Detailed analysis of basin fill sequences based on seismic and well data requires sequence stratigraphic analysis, but this analysis is augmented by a wider view including the onshore sediment-generating area. A new development with source-to-sink analysis was the ability to use the methodology on outcrop data. This required the ability to measure, calculate, and/or interpret critical data from the outcrop sequences, such as slope lengths.
Extensive offshore exploration in some basins has allowed for almost basin-wide coverage of 3D seismic data. Merging these data sets lifts predictive stratigraphy and source-to-sink to a new level. It is now possible to visualize entire source-to-sink systems, also including antecedent onshore drainage systems as well as their offshore complementary sequences. Increased efficiency and precision in subsurface and seismic interpretation allow for incisive perspectives on quantitative aspects of these source-to-sink systems. Thus, new understanding of complete systems will likely develop as a response to these extremely extensive seismic data sets where “everything” can be seen.