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

摘要：

通过对地质、地球化学等资料的研究,认为塔里木盆地志留系沥青砂岩有5种成因类型:①表生-浅层氧化沥青是指在油层露头区或油层位于近地表处,由于挥发、氧化、水洗和生物降解等作用而形成的一些焦油状沥青质重油以及固体浅层氧化沥青或硬质沥青.②储层分异沥青系指在油气二次运移的汇聚区,呈珠状或链状的烃类在运移和聚集过程中因储层物性变化重质组分滞留和轻质组分散失而形成的沥青或稠油.③蒸发分馏沥青是指晚期生成的轻质石腊族烃与早期生成的正常原油或稠油相混,造成不稳定状态,造成沥青从液态石油中析出.④水洗沥青系指油层或油气藏底(油水过渡带)因水洗作用而形成沥青或稠油.⑤热变质沥青目前在该盆地确认为热突变沥青,即由火成岩活动热烘烤而形成的沥青.

关键词: 塔里木盆地, 志留系, 沥青砂岩, 成因类型, 特征