3D Seismic interpretation and geologic evolution of an intraslope basin, Talara Basin, Deepwater Peru

FREDRICKS, J., P. WEIMER, S.P.J. COSSEY, G. FERNÁNDEZ, E.A. ROSSELLO, R. BOUROULLEC, G. DORN AND G. PECH

Houston

Congreso; 100º AAPG Anniversay ACE 2017; 2017

100º AAPG Anniversay ACE 2017

The middle slope of offshore Peru (500 to2000m water depth) consists of a series of intraslope basins filled with Eocene(?) deepwater deposits. The region has an especially complex structural andstratigraphic history during the Cenozoic. The basins vary in their structuralstyles, indicating complex tectonics likely associated with the Andean subduction.The Peruvian slope is a frontier exploration area with several major geologicstructures with seismic flat spots and amplitude anomalies, indicating goodexploration potential.  The study focuses on one instraslope basin inthe middle slope off northern Peru, which is an extension of the shallow-marineand continental world-class Talara Basin. Interpretation is based on 215 km2of 3-D seismic data. The area consists of an extensional intraslope basin thatforms a half graben, which is bounded to the east by a major north-striking normalgrowth fault and regional structural highs to the west and south. Threeprominent anticlines trend W/NW within the basin, and each anticline hasseismic flat spots, suggesting the presence of hydrocarbons in the area.The strata filling this basin representmid-slope turbidite systems deposited within a confined basin duringsyndepositional growth on different structures. Eight major depositionalsequences have been identified. Each sequence comprises a series of stackedchannel-levee and lobe deposits that vary in thickness, and onlap onto localgrowing structural highs. The local paleo-bathymetric highs and lows allshifted position through time, indicating the syndepositional growth of thestructures.The intraslope basin was primarily dextral(?) transtensional in nature during its evolution, but had, at least, twodiscrete phases of dextral (?) transpressional in movement causing thestructural inversion. Substantial deformation and complicated structuralgeometries result from the transpression. The three anticlines have stratalthickening at the apexes, indicative of inversion that occurred along listric décollementsurfaces that present at different depths. The later structural inversionplaced deepwater sands in the crest of the folds.