二连盆地“三明治”电性结构特征及其对古生界的研究意义

由于长期以来东北地区晚古生代的构造属性一直被认为是海西期褶皱带或碰撞造山带,而一直被作为中、新生代盆地的变质结晶基底成为油气勘查的禁区,限制了古生界的油气勘探和开发."佳木斯—兴蒙地块"新认识及二连盆地赛51井取得的石炭纪碳酸盐岩油藏的发现,开辟了二连盆地古生界油气勘探的新领域.本文对二连盆地3条典型的CEMP电测量资料进行了二维电阻率反演,结合研究区地震反射资料、钻孔电测井资料、钻井岩芯资料、岩石露头资料,揭示了二连盆地具有"三明治"的电性结构特征,同时指出二连盆地古生界广泛分布,在古生界与中生界之间广泛分布一套以玄武岩、安山岩、凝灰岩等为主的火山岩.这种"三明治"电性结构特征不但给古生界的研究提供了线索和依据,而且火山岩(高阻层)与其下伏古生界地层(低阻层)之间可形成良好的储盖组合(或生储盖组合),其对于古生界油气勘探的研究具有重要的意义.同时,认为二连盆地中、新生界和古生界的构造沉积演化主要经历了4个重要阶段,即:泥盆纪的南北差异性升降阶段、石炭-二叠纪的地层稳定沉积阶段、三叠纪-晚侏罗世的古生代盆地被改造和中新生代盆地构造格架形成的重要演化阶段以及中新生代的地层沉积阶段.

The sandwich electrical structures in Erlian basin and its significance for Paleozoic erathom

The tectonic setting in Northeastern China during the late Palaeozoic is always referred to as a Variscan fold belt or orogenic belt. Therefore, late Palaeozoic rocks as the crystalline basement of Mesozoic-Cenozoic basins are regarded to be impossible for hydrocarbon exploration, and this viewpoint restricts Palaeozoic petroleum exploration and exploitation. The new cognition of Jiamusi-Xingmeng massif and discovery of Well Sai-51 Carboniferous carbonate reservoir in Erlian Basin opened up a new field of Palaeozoic oil and gas exploration in Erlian Basin. This paper conducts two-dimensional resistivity inversion of three typical CEMP electric survey data in Erlian Basin, and combines with the reflection seismic information, the borehole electrolog information, the borehole core information and rock outcrop information in the study area. Thereby, it is indicated that Erlian Basin has sandwich electrical structures, Paleozoic erathem is widely distributed in this area, and volcanic rock whose chief constituents include basalt, andesite and tuff is widely distributed between Paleozoic erathem and Mesozoic erathem. The sandwich electrical structures provide clues and bases for the study of Paleozoic. In addition the volcanic rock (high-resistance) and underlying Palaeozoic stratum (low-resistance) can form a good combination of gas reservoirs and seal rocks (or gas source reservoirs and seal rocks), the structures have an important significance for the study of oil and gas exploration of Palaeozoic erathem. Meanwhile, we regard that the tectono-sedimentary evolution in Palaeozoic, Mesozoic, and Cenozoic in Erlian Basin has mainly undergone four important stages: the differential lifting movement stage between north and south of Devonian period, the steady deposition stage of Permo-carboniferous period, the important evolution stage from Triassic to late Jurassic Period which reformed the late Paleozoic basins and formed the tectonic framework of Mesozoic-Cenozoic basins, and the deposition stage of Mesozoic-Cenozoic period.