Integration of 3D Seismic and Advanced Structural Modeling in the Interpretation of Segmented Extensional Fault Systems in the Llanos Basin, Colombia

Abstract

Listen

Translate article

The most common hydrocarbons exploration target in the Llanos foreland basin of Colombia consists of three way footwall closures against east dipping normal faults. These faults are usually segmented along the strike separated by relay ramps that form at many different scales during the growth of normal fault systems as two or more offset faults propagate towards one another and overlap, forming an inclined relay ramp zone that accommodates further deformation until strain exceeds the strength of the relay zone and breaching occurs forming elongated sinuous faults with an apparent deficit in fault slip compared to the fault length. In recent years 3D seismic acquisition has increased in the Llanos basin of Colombia providing an extraordinary source of data that combined with advanced structural modeling techniques have yield better structural interpretations of these segmented normal fault systems, not only to produce better models of the real extension and integrity of the structural traps that can be targeted for hydrocarbons along these systems, but also to better understand the seismic pitfalls found in these complex structures. 3D models of both soft linked and breached relay ramps along a highly segmented trend of normal faults in the eastern portion of the Llanos basin are presented as well as 2D analogue models to illustrate the most common seismic pitfalls found in these systems. High resolution amplitude and semblance seismic attributes, as well as the geometry and distribution of hanging-wall faultrelated folds are used to constrain the displacement gradients along continuous fault segments, and that suggests fault growth by segment linkage. The strongly segmented southwest-northeast striking faults are interpreted to be the result of oblique Cenozoic extensional reactivation of underlying zones of weakness generated by preexisting northsouth trending Paleozoic to Early Cretaceous extensional and compressional faults forming characteristic strongly segmented en-echelon fault arrays. These highly segmented fault systems can produce a large variety of structural traps with a wide range of sizes that need to be considered during the exploration and production risk evaluations in this region.