伊通盆地莫里青断陷双一段油气成藏模式

    HYDROCARBON ACCUMULATION MODEL FOR THE 1ST MEMBER OF SHUANGYANG FORMATION IN MOLIQING RIFT, YITONG BASIN

    • 摘要: 莫里青断陷为伊通盆地最南端的一个二级构造单元,古近纪以来经历了张扭、热沉降、压扭和挤压构造演化阶段。通过对莫里青断陷双一段油气特征及分布的分析,厘清了高凝油、天然气的来源,分析了油气的输导体系和成藏过程,建立成藏模式,以指导油气勘探。双一段高凝油主要分布在凹陷的东西斜坡带,其成因与烃源岩的有机质类型和环境有关,分布与有机质低成熟及运移特征有一定关系;天然气主要分布在东南高部位,具有低熟特征。双一段油气主要来源于双阳组,凹陷斜坡带的扇三角洲、湖底扇砂岩体、断层及不整合面为油气侧向运移的良好通道。凹陷的远端则可能由于运移动力的不足或者输导体系不连通而难以到达。烃源岩分布、砂体展布、断层发育和不整合面结构分布是油气成藏主控因素。伊6区块晚期基底拱张,低熟气以断层和低渗储层为通道于高部位聚集成藏。

       

      Abstract: The Moliqing fault-depression is a sub-tectonic unit located in the southernmost of the Yitong Basin, which has experienced four stages of tectonic evolution since Paleogene, i.e. transtension, thermal subsidence, transpression and squeezing. In this paper, we described the characteristics and distribution pattern for the 1st member of Shuangyang Formation in the Moliqing rift, upon which the sources of high pour point crudes and gas, the migration paths and the formation of hydrocarbon accumulation are studied in order to build up the accumulation models for more successful exploration. The high condensate oil mainly occurs on the east and west slopes of the sag. The origin of high pour point crudes are related to organic matter types of the source rock and environment. The distribution depends upon the low maturity of organic matter and the migration. Gas is mainly distributed in the southeastern region where the organic matters are in low maturity. The oil and gas accumulated in the 1st member of Shuangyang Formation mainly come from the Shuangyang Formation. The fan delta and sublacustrine fan on the slope of the sag, faults and unconformities are the main channels for lateral migration. It is hard for the oil and gas to migrate to the distant end of the sag due to shortage of migration force and/or the disconnection of transport system. Therefore, the distribution of source rock, sand bodies, faults and unconformities are the main controlling factors of hydrocarbon accumulation. In the Yi6 area, however, the basement suffered from later tension, faults and low permeability reservoirs may provide channels for low matured gas to move to higher areas.

       

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