AAPG Bulletin, V. 82 (1998), No. 7 (July 1998), P. 1329-1352.

Source Rocks and Oil Families, Southwest Maracaibo Basin (Catatumbo Subbasin), Colombia¹

D. A. Yurewicz,² D. M. Advocate,² H. B. Lo,³ and E. A. Hernández⁴

©Copyright 1998.  The American Association of Petroleum Geologists.  All Rights Reserved

¹Manuscript received December 4, 1995; revised manuscript received May 30, 1997; final acceptance February 3, 1998.
²Exxon Exploration Company, P.O. Box 4778, Houston, Texas 77210-4778.
³Exxon Production Research Company, P.O. Box 2189, Houston, Texas, 77252-2189.
⁴Ecopetrol, Calle 37, No. 8-47, Piso 8, Santafé de Bogotá, Colombia.

Data and interpretations for this paper were obtained from a joint Exxon-Ecopetrol study of the Catatumbo subbasin. Many people participated or assisted in that study. J. J. Sequeira, P. C. Wellman, and V. J. McDermott (Exxon Exploration Company) interpreted the structural setting of this area. R. H. Young (Exxon Exploration Company) helped to develop the stratigraphic framework. Quinn Passey and V. A. Clark (Exxon Exploration Company) assisted in Delta Log-R analyses. M. B. Farley, T. C. Huang, and Y. Y. Chen (Exxon Exploration Company) provided biostratigraphic interpretations that helped constrain the stratigraphic framework. We extend special thanks to Ernesto Samper (Ecopetrol), who assisted in obtaining Ecopetrol reports and logs; Carlos Arce (Esso Colombiana), who coordinated and assisted in obtaining core, cuttings, and oil samples; and T. J. Frantes (Exxon Exploration Company), who facilitated the initiation and completion of this work. This paper benefited from the critical review of editors Kevin Biddle, Wallace Dow, Steven Schamel, and Geoffrey Newton. Finally, we would like to thank Exxon Exploration Company, Exxon Production Research Company, and Ecopetrol for their permission to publish the results of this study. 

ABSTRACT

An extensive evaluation of organic source facies, the application of hydrocarbon geochemistry, and integrated basin modeling of the southwest portion of the Maracaibo basin in Colombia (referred to as the Catatumbo subbasin) indicate (1) multiple organic-rich horizons occur within the Cretaceous and Paleocene sections, (2) most of the reservoired oil and gas was sourced locally from Cretaceous marine carbonate facies by means of lateral and vertical migration, (3) two subfamilies of Cretaceous oils are recognized that reflect different source facies within the Cretaceous section and different maturation and migration histories, (4) oil and gas present in the southern Catatumbo subbasin indicate a contribution from Paleocene terrestrial source facies that required westerly migration from a source area in Venezuela, possibly within the North Andean foredeep, and (5) oil generation from Cretaceous source rocks began in the Oligocene, and peak generation occurred in the late Miocene. These key conclusions are based on source rock analyses of 365 rock samples from eight wells, gas chromatography/mass spectrometry, and isotope and bulk composition analyses from nine rock extracts and seven oil samples.