塔中Ⅰ号带奥陶系烃包裹体荧光特征与成藏期

Fluorescence characteristics of the Ordovician hydrocarbon inclusions in the Tazhong-Ⅰ slope-break zone and the timing of hydrocarbon accumulation

根据显微镜下烃包裹体的荧光特征、与方解石脉的穿插关系以及均一温度等特征,将塔中Ⅰ号坡折带奥陶系储层中发育的烃包裹体划分为4个期次;结合塔中地区区域构造演化特点,研究区四期烃包裹体分别对应着4个油气成藏期次,即志留纪末低成熟油形成时期,海西晚期生油期,早喜马拉雅期凝析油-湿气形成期,喜马拉雅期后期干气阶段。这4期烃包裹体在塔中Ⅰ号带奥陶系储层中具有明显的分带性,由东南浅埋藏油区向西北深埋油区将塔中Ⅰ号带奥陶系储层包裹体分布情况分成4个区域,其中第Ⅲ,Ⅳ期烃包裹体古油对现在油气藏起决定作用。

Hydrocarbon inclusions in the Ordovician in the Tazhong- Ⅰ slope-break zone can be divided into four episodes of development according to their fluorescence characteristics, intercalating relationship with calcite vein, and homogeneous temperature, and so on. Based on the tectonic evolution of the area, it is believed these episodes correspond to four episodes of hydrocarbon pooling： low maturity oil accumulation at the end of Silurian, oil generation in the late Hercynian, condensate oil and wet gas accumulation in the early Himalaya, and dry gas accumulation in the late Himalayan. The distribution of these four episodes of inclusions presents clear zonation in the Ordovician reservoirs in the Tazhong- Ⅰ belt. Four zones are recognized from the shallow oil reservoir in the southeast to the deep oil reservoirs in the northwest. It is suggested that the fossil oil from the episode Ⅲ and Ⅳ played a dominant role in the formation of present hydrocarbon accumulations.