WU MAOBING, Lanzhou Institute of Geology, Chinese Academy of Sciences, Lanzhou, P.R. China
ABSTRACT: Volcanic Rocks and Their Effects on Hydrocarbon Generation
Many oil reservoirs are often related with volcanic activities in the rift basins of eastern China. In order to evaluate how great potential effects of volcanic products on hydrocarbon generation of immature source rocks, I collected some lacustrine shales and volcanic rocks which interbed with shales and sandstones from Jurassic Xiaoling Formation in Kuandian Basin, east of Liaoning Province, and measured separately the volatile contents (especially H2, CH4) of source rock, volcanic rock, and a mixture of the source rock and volcanic rock with a MAT-271 mass spectrometer by step-heating process. Experimental results reveal that volcanic rocks could provide H2 and CH4 to source rocks for hydrocarbon generation, especially fresh basic volcanic rocks (H2 15 ~ 40µl STP/g), neutral and altered basic volcanic rocks have H2 less than 18µl STP/g. The volatile contents of H2 and CH4 in the Mixture of source rock and volcanic rock both increase sharply with the increase of pyrolysis temperature from 200 degrees C to 400 degrees C , but have an inverse relation when the heating temperature is over 400 degrees Cwith a decrease of H2 content and an increase of CH4 36 times higher than the CH4 products of source rock and volcanic rock separately. So it can be deduced that volcanic activity not only provides heat and H2 but also may induce some catalysis reactions by volcanic material to promote hydrocarbon generation.
AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid