摘要
国内外不同时代砂岩漂白现象的研究表明,漂白砂岩形成均与有机流体的参与有一定联系。因而,可将其作为烃类曾经运移、聚散的线索,预测在其附近可能有(古)油、气藏存在或遭改造破坏。鄂尔多斯盆地在后期改造过程中油气赋存状态发生了重新调整。通过对鄂尔多斯盆地东北部中生界漂白砂岩的主量元素、稀土元素分析和岩石学特征研究,初步确定该区漂白砂岩形成于酸性还原环境。其岩石学特征主要表现为较高的高岭石含量及黄铁矿含量,同时氧化铁边部颜色较中心浅;主量分析结果证实漂白砂岩的A l2O3含量较高,Fe3+/Fe2+较低;稀土元素分析结果显示,无论是岩心样品还是露头样品,都存在Eu负异常,均指示了还原环境的特征。综合研究表明,鄂尔多斯盆地东北部中生界砂岩漂白现象指示了天然气的逸散作用。
Study on bleaching of sandstone of different ages in the world indicates that the formation of bleached sandstone is relevant to organic fluid flows. It can provide some clues to hydrocarbon migration, accumulation and dissipation, thus can be used as an evidence for predicting the existence or destruction of oil/gas reservoirs （ or fossil oil/gas reservoirs） in nearby areas. The occurrence of oil and gas in Ordos basin would have been altered during the later reconstruction of the basin. Based on analysis of the major elements, rare-earth elements and petrologic characteristics of Mesozoic bleached sandstone in the northeastern Ordos basin, it is preliminarily believed that the bleached sandstone in the study area would have been formed in an acidic and reducing environment. The bleached sandstone is characterized by its relatively high content of kaolinite and pyrite, and the color of ferric oxide minerals on the edge is lighter than that in the center. The major element analysis of sand- stone samples shows that they have relatively high Al2O3 content and low Fe^3＋/Fe^2＋ ratio; the REE analysis shows that the Eu contents in both core and outcrop samples are negative; all these indicate a reducing environment. At the same time, the geochemical characteristics of oil sand in the northern part of the basin indicate that the oil is exactly condensate as a result of the migration and dissipation of Permo-Carboniferous humic gas in the south to the surface. In a word, the comprehensive study suggests that the bleaching of Mesozoic sandstone in the study area indicates dissipation of natural gas.
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2006年第2期233-238,243,共7页
Oil & Gas Geology
基金
国家重点基础研究发展规划(973)项目(2003CB214607)
长江学者和创新团队发展计划资助项目(IRT0559)
