Fildani, Andrea¹, ZhengZheng Chen¹, Michael Moldowan¹, Andrew Hanson², Stephan Graham¹
(1) Stanford University, Stanford, CA
(2) University of Nevada Las Vegas,

ABSTRACT: Talara Basin Petroleum System: Geochemical Characteristics of Oils and Correlation with Possible Source Rocks from NW Peru

The presence of petroleum in coastal northwest Peru has been known for centuries. Original inhabitants used oil from natural seeps for various tasks, and early Spanish colonists used pitch to caulk their ships and to waterproof ropes. The first well in the basin was drilled in 1874, making Talara one of the first producing petroleum basins of South America. Cumulative production from the basin exceeds 1.68 BBO and 1.95 trillion cubic feet of gas (TCFG) from forty-two oil and gas fields. Despite recoverable oil and gas estimates of 2.90 billion barrels of oil equivalent (BBOE), very little is known about the petroleum system. Twenty-eight oils from a selection of wells from throughout the basin were analyzed for biomarkers. Preliminary results suggest that the source rock was most probably a marine clay deposited in an oxic to sub-oxic environment. The petroleum shows a substantial amount of oleanane, indicating significant terrestrial influence. Our analyses suggest that the oils were generated from one source rock, probably deposited in the early Paleogene in a mixed marine/terrestrial environment (probably deltaic). The ratio of 24-nor to 27-norcholestane suggests upwelling components in the source rock. For comparison, possible source rocks were selected and analyzed from different outcrops and wells and compared with the oils. These data suggest that Upper Cretaceous limestone and marls previously believed to be an important source rock can be discounted as an important contributor to Talara basin oils.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.