NE Versus SW Quartersphere Lacustrine Source Rocks: Case Study from Northeastern Asian and South American Basins
Southwestern and northeastern quarterspheres contain a vast portion of the world’s petroleum reserves that originated from lacustrine source rocks. For instance, lacustrine oils in China and Brazil amount to 90% and 95% of their total reserves, respectively, and in the latter the number may rise even higher due to the recent super-giant offshore discoveries linked to lacustrine sources.
Studied lacustrine rocks range from Carboniferous to Holocene in age; however, most of them belong to the Cretaceous and Tertiary. These Cretaceous to Tertiary lacustrine source rocks were deposited in diverse basin types.
The objective of this study is to investigate the differences and similarities between lacustrine source rocks deposited in diverse paleolatitudes and paleolongitudes as well as in contrast hydrological conditions (freshwater vs. saline lakes). Special attention is also paid to the organic matter production and preservation. Such a complex approach helps to establish relationships of lakes’ paleogeography, hydrology, organic matter production and preservation with source rocks quality and reserves produced.
Comparative analysis demonstrates that most prolific lacustrine source rocks from South American basins were accumulated under more arid conditions than those from Northeastern Asia (mostly tropical-subtropical). In Latin America, most productive lacustrine source rocks were deposited in the Lower Cretaceous brackish-saline lakes of contemporary Brazil. Those in present China were deposited in the Cretaceous freshwater lakes and Tertiary freshwater to hypersaline lakes.
Considered lacustrine source rocks from NE and SW quarterspheres are distinguished mainly with regards to their depositional settings, TOC contents, kerogen types and compositions of generated hydrocarbons.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009