The Analysis of Tectonic Controls on the Shale Distribution and Its Resource Potential in Lacustrine Basins in East China
The shale gas and shale oil potentials in the Meso-Cenozoic lacustrine basins are worth investigating since China produces most oil from the lacustrine basins. The organic-rich semi-deep to deep lacustrine shales are widely distributed in East China, North China, Northwest China and Southwest China with an area of nearly (23-33) ×104 km2. The shale gas and shale oil potentials in these lacustrine basins could be significant since almost more than 50% generated hydrocarbons are still trapped in the source shales. This study mainly focuses on the most important lacustrine shales from rifted basins in East China, e.g., Paleogene Bohai Bay basin, Cretaceous Songliao Basin, etc. Compared with marine shale, the lacustrine shale has some similarities regarding to the extensive distribution within the basin and some similar geochemical parameters. However, for lacustrine basins in East China, there are many unique features in the aspects of tectonic activities, depositional environment, thermal evolution, etc. Generally, the lacustrine shale in East China is characterized by high content of organic matter (up to 30%), lower maturity (usually less than1.5%), high clay mineral content, complex tectonic setting, rapid lateral shale facies changes and interbedded sandstones or carbonates within shale. The shale gas potential is mainly distributed in the areas of high maturity shales and shale oil potential is mainly located in areas with low maturity shales for lacustrine basins in East China. For the Mesozoic-Cenozoic lacustrine basins in East China, the sequence stratigraphic architecture, sedimentary environment, space-time distribution of shales and the fracture orientation of shales were strictly controlled by episodic tectonic activities. The geochemical properties of shales deposited in different stages also vary. The hydrocarbon generation potentials and shale distribution extent are the largest during the stable subsidence or high lake level periods.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California