Normal Growth Fault Evolution in the Columbus Basin, Trinidad

Freitag, Ulrike A.¹, David J. Sanderson¹, Lidia Lonergan² (1) Imperial College London, London, United Kingdom (2) BP Exploration, Sunbury on Thames, United Kingdom

Normal growth faults record their displacement history in the stratigraphy of their wall rocks and hence yield essential information about fault evolution, including slip-rates, propagation history, and information on the linkage and displacement transfer on different fault segments. A series of normal growth faults in the Columbus Basin, offshore Trinidad, was investigated using a high-resolution commercial 3D seismic dataset. This, together with the rapid sedimentation rates, good well control and dating of key horizons, allows us to investigate the distribution and evolution of displacement, and address the fault growth mechanism.

The fault geometry, throw distribution and timing on two fault systems are presented: 1) a non-breached to breached relay fault interaction, 2) a fault showing en echelon splaying towards shallow levels from a continuous fault at depth. The displacement shows abrupt changes on different segments and for different horizons. Fault displacement back-stripping has been used to determine the amount of throw accumulated in various parts of these fault systems during several dated time intervals between 2.5 Ma and the present. Corrections for compaction have been applied to determine the initial throws and fault slip rates.

The evolution of fault slip rates is used to test models of fault growth and is therefore essential in exploration for oil and gas. Knowing the timing of fault activity in detail helps to constrain hydrocarbon trap formation, migration through active relay ramps and possible leakage or migration along faults.