Reconstructing geological systems involves more than plate tectonics alone, but changing trends in research and in company structures have led to this vital component of any regional analysis being neglected. Are the results of large-scale studies really so unimportant? Integrated tectonic analysis goes beyond describing how a basin looks, so that knowledge from one area can improve understanding elsewhere, telling us how and why a basin is the way it is. This article will discuss how we can apply plate tectonic results and palinspastic paleogeographic analysis, allowing prediction of hydrocarbon potential in poorly known areas, enabling us to understand mistakes made and reducing risk in exploration programmes.
Tectonic analysis allows us to define the geometric and temporal framework for block-scale basement evolution, enabling us to predict and assess the distribution of basement types and depths, the relationship of basin formation to crust type and basement faults, subsidence and heat flow histories, inversion geometries and modes of trap formation. We can predict paleowater depth where it is otherwise unknown, predict stratigraphic and structural traps and predict sandstone provenance and source/reservoir occurrence. To understand original basin geometry and sediment infill, we use palinspastic reconstruction (undoing subsequent deformations) to develop modified basemaps. Geological development of a basin can then be reconstructed in sufficient detail that it becomes a useful exploration tool, just like many other areas of geology.
Unfortunately, few data sets yield a unique interpretation. Wrestling with multiple hypotheses is common, and many models of crustal deformation can be made to fit the data. If optimum exploration strategy is driven by the chosen interpretation, mistakes can potentially be very costly. Integration of multiple and diverse data sets is one approach to reducing the range of interpretations, but too often the ‘best’ data cannot give a clear solution, and secondary data sets muddle the picture further.
Worse, this multifaceted picture may not be fully understood by anyone on the work team, and the full implications, the basis of an exploration model, might not be recognised. Plate tectonic and structural processes evolve over scales larger than most exploration blocks, and to ignore the larger scale can lead to serious misinterpretations. Unfortunately, broadening the scale of geological assessment beyond the limits of the block or field remains, in many cases, little more than a matter of description. This is a key part of a geologic analysis, but it is very important to take the next step and understand how and why a given set of features has developed, moving from static description into time-progressive kinematic analysis.
In this article, we outline some often-forgotten principles behind kinematic analysis and illustrate their application to the geologic history of one of the world’s most significant hydrocarbon provinces: the Gulf of Mexico.
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Geosciences
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