关键词: 塔里木盆地, 志留系, 沥青砂岩, 成因类型, 特征

Abstract:

By using geological and geochemical data,the genetic type of the Silurian asphaltic sandstones in Tarim Basin is investigated and divided as the following:(1)Oxidized asphalt on surface or in shallow-layer is the heavy asphalt crude and solid,oxidized asphalt or gilsonite formed by volatilization,oxidization,water washing and biodegradation in oil-layer outcrop area or near earth surface.(2)Asphalt differentiated by reservoir bed is formed through differentiation by reservoir bed in the hydrocarbon gathering area of secondary migration.The differentiation is caused by change of reservoir physical properties when hydrocarbons migrating through and gathering in the reservoir bed,and light composition is lost and heavy one stays to form asphalt or heavy oil.(3)Asphalt fractionated by evaporation results from the mixing of light paraffin series generated in the later stage and normal or heavy oils generated in the earlier,resulting in the precipitation of asphalt from liquid oil because of the unstable state.(4)Asphalt formed by water washing is found at the bottom of oil bed or reservoir(water-oil transition zone,asphalt or heavy oil).(5)Asphalt formed by thermal metamorphism found in Tarim Basin so far is caused from heating of igneous activity.

Key words: Tarim Basin, Silurian, asphaltic sandstone, genetic type