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鄂尔多斯盆地上三叠统延长组裂隙充填的方解石脉中含有大量多相态烃类包裹体,包括固体沥青+液态油+气态烃3相包裹体、气/液比差别很大(最小仅为5%,最大超过70%)的液态油+气态烃二相包裹体以及纯液态油包裹体、盐水+液态油+气态烃3相包裹体等。岩相学观察表明,这些不同相态烃类包裹体是被同时捕获形成的共生不混溶包裹体,气/液比不同的烃类包裹体具有相近的均一温度,分布范围较小(74℃~117℃),综合分析认为它们是在沸腾状态下被同时捕获的。不同相态烃类包裹体显微傅里叶红外光谱和荧光光谱不同,表明其烃类成分的差异。油/源对比研究表明烃类包裹体与长8油层的原油均来源于长7烃源岩。结合盆地区域构造演化分析认为,延长组长7油层组厚层烃源岩层在埋藏热演化和油气形成过程中出现的过剩压力,在早白垩世油气形成高峰阶段达到顶峰;鄂尔多斯盆地在晚白垩世抬升和剥蚀产生的卸载作用导致延长组长7烃源岩层在超高压下破裂,其中积聚的石油因压力突降而沸腾并沿裂隙排出并运移进入特低渗致密砂岩储层成藏。
The fractured-filled calcite veins of the Upper Triassic Yanchang Formation in the Ordos Basin contain a large number of multiphase hydrocarbon inclusions, including solid bitumen + liquid oil + gaseous hydrocarbon 3-phase inclusions with very different gas / liquid ratios (only a minimum of 5 %, Up to over 70%) of liquid oil + gaseous hydrocarbon two-phase inclusions and pure liquid oil inclusions, brine + liquid oil + gaseous hydrocarbon 3-phase inclusions and the like. Petrographic observation shows that these hydrocarbon inclusions in different phases are intergrowth immiscible inclusions captured at the same time. The gas / liquid ratios are similar to those of different hydrocarbon inclusions, and their distribution ranges are small (74 ℃ ~ 117 ℃), a comprehensive analysis that they are captured at the same time under the condition of boiling. Different phase hydrocarbon inclusions have different FTIR and fluorescence spectra, indicating the difference of hydrocarbon composition. Oil / source correlation studies show that hydrocarbon inclusions and Chang 8 oil are derived from Chang 7 source rock. According to tectonic evolution analysis of the basin, it is considered that the overpressure occurred during the thermal evolution of burial and formation of oil and gas during the formation of the Upper Cretaceous during the Cretaceous in the Early Cretaceous. The unloading caused by uplift and erosion led to the rupture of Chang 7 Changyuan source rock under ultra-high pressure. The accumulated oil boiled due to pressure drop and discharged along the fracture and migrated into the reservoir of tight sandstone of low-permeability.