基于地球物理方法预测二连盆地及邻区晚古生代潜在烃源岩分布

二连盆地及邻区是我国油气勘探的重点区域之一,普遍认为烃源岩层主要分布在中生代地层,对其晚古生代地层的烃源岩潜力研究较少,本文对研究区内晚古生代碳酸盐岩及泥岩进行了有机地球化学实验并分析其烃源岩潜力,评价结果表明二连盆地及邻区内晚古生代地层具有一定的生烃潜力,受高成熟度的影响,剩余潜力以生气能力为主.依据研究区内电法剖面、布格重力异常特征及磁性资料认为晚古生代潜在烃源岩层具有"低电阻、高密度、弱磁性"的地球物理性质,并初步预测了二连盆地及邻区晚古生代的深度大致分布在3～5km的范围内,进一步利用优化后的小子域滤波重力异常分离技术对晚古生代地层进行了厚度预测,刻画其平面分布特征,认为研究区内的晚古生代地层具有两个分布中心,其中心区厚度范围为1000～2000m之间,与野外地质剖面的厚度基本一致,晚古生代潜在烃源岩的平面预测可以为二连盆地油气勘探工作提供新方向.

Prediction of Late Paleozoic potential hydrocarbon source rocks in Erlian Basin and adjacent areas based on geophysical methods

The Erlian Basin is an important area of oil and gas exploration in our country.The known hydrocarbon source rocks are mainly distributed in Mesozoic strata,while the study on Late Paleozoic potential hydrocarbon source rocks remains little.In this paper,the organic geochemistry experiment results show that the carbonate and mudstone layers of the Late Paleozoic in the Erlian Basin and its adjacent areas have a certain hydrocarbon source rocks potential.The residual potential of source rocks is dominated by gas generation due to the high mature.Research of electrical survey,Bouguer gravity anomaly and magnetic data suggests that the Late Paleozoic potential hydrocarbon source rocks in this region are characterized by low resistivity,high density and weak magnetism.Moreover,the depths of these rocks are predicted to range 3~5 km roughly.Using the improved technique of gravity anomaly separation based on sub-region filtering, this work predicts the thickness of the Late Paleozoic source rocks.The results show that two centers of Late Paleozoic strata are presented in Erlian Basin and adjacent areas, of which the thickness ranges 1000~2000 m, largely consistent with geological cross sections in the field.Such distribution prediction of Late Paleozoic potential source rocks can provide a new direction for oil and gas exploration in the Erlian Basin.