The Main Factor Controlling Petroleum Migration Along Unconformity in the Junggar Basin
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摘要: 准噶尔盆地不整合上下发现了众多油气藏，表明不整合是油气运聚的有利通道。通过对不整合上下地层中含油气流体活动特点的分析，提出了不整合的垂向结构是控制油气沿不整合运移的主导要素。不整合从垂向上可划分为上(底砾岩)下(风化壳)两层结构，有时下层风化壳顶部也会发育一层厚度不均的粘土层，使得不整合表现为三层结构。其中，风化壳又包括风化破碎型(火山岩)和风化淋滤型(碎屑岩)两类。基于底砾岩的沉积特征和风化壳的类型，从垂向结构入手，进一步将不整合划分为基岩披覆、砂砾岩和砂泥岩对接等三大类型：基岩披覆型不整合在本区对油气运移最为有利，砂砾岩型不整合次之，而砂泥岩对接型不整合一般不能成为油气运移通道。Abstract: Many oil and gas pools have been found above or below the unconformity in the Junggar Basin, indicating that the unconformity is a good conduit for petroleum migration. Based on the petroleumbearing fluid activities in unconformity zones, we suggested that vertical structure of unconformity is the most key factor controlling the petroleum migration. Two layers of unconformity were divided, i.e. bottom conglomerate (upper layer) and weathered crust (lower layer). In addition, if some mudstone were developed on the top of weathered crust, the unconformity was threelayer structured. The weathered crust could be further divided into weathered fractured crust based on volcanic rocks, and weathered solution crust based on detrital rocks. Then, we defined three types of unconformity according to lithostratigraphic features of the bottom conglomerate and the weathered crust. They include overlapbase type, sandstoneconglomerate type, and sandstonemudstone type, among which the first one is the most favorable for petroleum migration, the second intermediate, and the last could generally not be considered as a conduit.
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Key words:
- unconformity /
- vertical structure /
- petroleum migration /
- Junggar Basin
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