Geochemical assessment and petroleum systems in the Sinú-San Jacinto Basin, northwestern Colombia

The Sinú-San Jacinto Basin (SSJB), onshore and offshore, has abundant oil and gas manifestations, evidencing the existence of various petroleum systems. The onshore oils can be separated into at least two families. The first one (Oil Family I) is derived from source rocks deposited in anoxic marine platform, and the other one (Oil Family II) is derived from source rocks deposited in deltaic marine environment with high input of terrestrial organic matter. Also there are heavy biodegrated oil seeps as well as oil seeps possibly derived from others organic facies, a troublesome to classify with the available data. Regarding source rock correlations, Cansona Formation bitumens exhibit good correlation with the Oil Family I, and Cienaga de Oro Formation extracts exhibit some correlation with oils from the Oil Family II. There are also some oils seeps (onshore and offshore) on which there is no conclusive information about its origin. About the gases, their isotopic and molecular composition, indicate that some are biogenic and others thermogenic, as well as others are mixtures biogenic/thermogenic. Onshore and offshore SSJB were recognized three (3) kitchens or pods of generation with oil generation and expulsion determined by geochemical modeling at depths greater than 12000 feet. Associated with each one of the three kitchens, have been postulated the petroleum systems Cansona – San Cayetano (.), and Ciénaga de Oro – Ciénaga de Oro (.). Additionally in the southern onshore pod could be postulated a speculative petroleum system, the Precansona – Precansona (?) Petroleum System. •The SSJB has numerous seeps; however is an under-explored basin.•In the basin exists at least two oil families.•In the basin have been occurring refreshing processes in different areas.•There are three petroleum systems associated to three pods of generation.