新疆北部石炭纪盆地构造演化与油气成藏

Carboniferous basin evolution and its hydrocarbon accumulation in the north of Xinjiang

根据油田近期勘探资料及前人研究成果,在新疆北部地区石炭系沉积前构造背景分析的基础上,对石炭纪盆地沉积构造演化进行了研究,该区具有微地块、多拼合、弱固结、构造活跃等盆地形成背景,经历了早石炭世、晚石炭世两期盆地的形成、发展与消亡过程,二叠纪—新生代是石炭纪盆地的改造演化期。石炭纪火山岩广泛发育,结合前人研究成果,通过盆地覆盖区钻井样品的地球化学综合分析,认为该区石炭纪整体处于拉张的构造环境。通过石炭系的沉积与分布特征,认为早石炭世和晚石炭世盆地演化受早期构造的控制,具有继承性、方向性和新生性的特点。石炭纪末期的构造事件基本结束了该区的海相盆地的演化,进入陆内盆地演化期,石炭纪盆地遭受埋藏或隆升改造,经历了海西晚期、印支期、燕山期以及喜马拉雅期的构造改造作用,存在埋藏、隆升剥蚀、岩浆热改造、断裂、褶皱变形等多类型的改造作用,各地区的改造特点存在差异。油气勘探成果证实,石炭系是新疆北部重要的勘探层系,在早石炭世和晚石炭世盆地演化期都形成了优质的烃源岩,火山岩系既是油气的储集层,也是重要的盖层,盆地的多期改造事件不仅有利于火山岩储层物性改善,也形成了石炭系有利的油气圈闭,目前已经发现了石炭系自生自储和上生下储的油气藏类型,油气的分布特征显示了石炭系自生自储油气藏具有近源分布特征。因此,加强盆地形成演化研究,圈定沉降中心和烃源岩的分布对于油气勘探具有重要意义。

The tectonic evolution of the Carboniferous sedimentary basins was researched based on recent exploration data and previous research results in the north of Xinjiang. The basins were developed with the geological setting of micro-block, muhi-collision, weak consolidation and tectonic activation. During the Carboniferous, the region had undergone two stages of superposed basin evolution. The Carboniferous basins were strongly transformed from the Permian to the Cenozoic. The Carboniferous volcanic rocks were widely developed~ they were formed in the Carboniferous extensional tectonic setting according to comprehensive analysis of drilling geochemical samples. Based on the deposition and distribution of the Carboniferous, the Early and Late Carboniferous basin development was controlled by the early structures, which possessed inheritance, directionality and newborn characteristics. The evolution of the marine basin ended basically because of the tectonic events in the end of the Carboniferous, and large continental basin began to form. The Carboniferous basins were buried, uplifted, eroded, magmatic thermal reworked, and deformed or folded during the late Hercynian, Indosinian, Yanshan and Himalayan. There are differences in the transformation of each region. Oil and gas exploration results confirmed that the Carboniferous in northern Xinjiang is important exploration strata. The high-quality source rocks formed both in the Early and Late Carboniferous basin evolutiorL Volcanic rocks are important cap rocks and reservoirs of oil and gas. Multi-transformation events not only benefitted volcanic reservoir properties, but also formed favorable hydrocarbon traps. Self-generated and injected reservoirs have been found in the Carboniferous. The distribution of oil and gas shows that the self-generated reservoirs distribute near the source. Therefore, it is of significance to strengthen the research of the evolution of basin formation, of subsidenee centers and the distribution of hydrocarbon source rocks.