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ABSTRACT: The Peru Continental Margin: High Petroleum Potential in a Modern Fore-Arc Setting

James K. Crouch, Steven B. Bachman, Claire L. Zucker

Strata within modern fore-arc basins commonly are characterized as (1) containing little or no oil-prone source rocks and poor, volcaniclastic-rich reservoir rocks and (2) being submature due to low geothermal gradients. Hence, many explorationists may view modern fore-arc basin settings as having little oil potential or, at best, as only marginally prospective.

The Talara fore-arc basin of Peru is a striking exception to this generally held belief. Situated along the northwestern part of Peru's active convergent margin, it extends offshore to within 50 km of the Peru-Chile Trench. Unlike the typical modern fore arc, the Talara basin is a prolific oil producer. From onshore and offshore fields, it has already produced over 1.3 billion bbl of oil averaging 38° API gravity. Moreover, the lightly explored offshore, which constitutes more than half of the Talara basin, probably holds an additional 2 billion bbl of undiscovered recoverable reserves.

The Talara basin encloses an area of about 17,000 km2, yet 70% of the production ( >900 million bbl) has come from coastal onshore fields that encompass an area about one-tenth this total size (1750 km2). Production has come chiefly from Paleocene and Eocene sandstones enclosed within a thick (composite thickness of 10,000 m) lower Tertiary marine clastic section. Pervasive normal block faulting has persisted across this and other fore-arc basins situated along the Peru margin from the Late Cretaceous through much of the Tertiary. This distinctive structural style, along with younger detachment faults, provides numerous structural traps whose complexities will, no doubt, challenge explorationists for years to come.

A number of other Peru fore-arc basins, which are both geomorphically and structurally on trend with the Talara basin, also contain thick lower Tertiary sections and exhibit similar extensional histories. For these reasons, we believe that at least some of these on-trend basins may have an exploration potential that is similar to the Talara fore-arc basin.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990