Thermal Evolution Patterns of the Sinian-Lower Paleozoic Petroleum System in Sichuan Basin, Southwest China

Abstract

The conversion of organic matter into oil and gas depends upon temperature and time, and the study of thermal evolution of source rocks is of importance for formation of a petroleum system. Using the Easy%Ro chemical kinetic model, we simulated the thermal evolution history of the Sinian-Lower Paleozoic source rocks in several representative boreholes located in different tectonic units based on the sedimentation process and thermal history reconstruction of Sichuan Basin. The results showed that the thermal evolution characteristics of the Lower Cambrian and Lower Silurian source rocks were dramaticlly different from each other in various tectonic locations. Then, four thermal evolution patterns were established. (1)The Lower Cambrian source rocks in Southern Sichuan Basin entered the oil-window and began primary hydrocarbon generation during Caledonian period, then stopped after rapid secondary thermal evolution in the beginning of Late Permian. (2)The Lower Cambrian source rocks in Southwestern Sichuan Basin and the Lower Silurian source rocks in Southern Sichuan Basin were characteristics of one-stage rapid evolution. (3)The Lower Cambrian source rocks in Eastern and Northern Sichuan Basin were characterized by typical two-stage evolution. (4)It it stayed continuous thermal evolution after Late Permian of the Lower Cambrian source rocks in Central Sichuan Basin, the Lower Silurian source rocks in Eastern and Northern Sichuan Basin. The primary thermal evolution controlling factors of the Sinian-Lower Paleozoic petroleum system in Sichuan Basin were studied on the basis of coupling relationship among sedimentation rate, heat flow and temperature increasing rate. Generally speaking, it was controlled almost completely by abnormal thermal effects of the Emeishan mantle plume and basalts in Southwestern and local Southern Sichuan Basin. While, it was influenced by both deep burial and heat flow evolution (the former dominated in temperature increasing) in other areas of the basin. Therefore, the thermal evolution patterns have a quite important effect on the formation and evolution of the Sinian-Lower Paleozoic petroleum system in Sichuan basin.

AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014