Fernando Zúñiga-Rivero¹, Hugh Hay-Roe¹, Allen Lowrie²

(1) BPZ & Associates, Inc, Houston, TX
(2) CONSULTANT, Picayune, MS

ABSTRACT: Complex Hydrocarbon Reservoirs and Petroleum Systems of the Offshore Talara Basin, NW Peru

Multi-channel seismic data along the Peruvian margin permits development of geologic models using seismic and sequence-stratigraphic techniques. Models indicate two separate thermal maturation processes: subducted marine sediments with 0.5-2.0 % total organic carbon, and normal subsidence with burial under the continental shelf and upper slope.

The unique oceanographic-geologic conditions associated with "El Niño" phenomenon have been present at least since Campanian time. Sediment sources are of three types: (1) subducted deep-ocean sediments; (2) continent-derived mass-wasted debris descending across the slope; and (3) organic matter precipitated from the ancestral Humboldt Current, together forming a previously unexamined petroleum system.

Material from the three organic sources are incorporated into the subduction process and transported into the subsurface. Hydrocarbon generation occurs as sediments are subducted and undergo thermal maturation, to be emitted along that traverse-first as petroleum, then as natural gas. Thus, the petroleum system depends on (1) subsidence and burial of Tertiary and Mesozoic sediments along the shelf, and (2) the essential role of organic materials carried into the subsurface by plate subduction.

Buoyant liquid petroleum and gas would rise through shattered sediments and along normal faults cutting the slope margin. Potential fault-traps appear plentiful throughout the Tertiary. Thick Mesozoic sections also contain possible traps. Traps are both structural (normal faults) and stratigraphic (deltas across the mid-to outer shelf and shelf-break, as well as fluvial deposits throughout the entire Tertiary). Seaward from the Talara basin's prolific and well-explored onshore and inner shelf is the proper area to commence exploration.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado