塔河油田塔深3井区奥陶系深层油气成藏的地球化学证据

Geochemical evidence for hydrocarbon accumulation in deep Ordovician in TS3 well block,Tahe oil field

塔深3井是塔河油田首次在奥陶系深层获得油气突破的探井,在奥陶系中—下统鹰山组上段获得高产油流。塔深3井区奥陶系深层的原油物性和该区顶部风化壳型油藏一致,均为高凝固点、高硫、高蜡、高黏度的超重质原油。原油中正构烷烃系列分布完整,但色谱基线出现不同程度的抬升;原油中普遍含有25-降藿烷系列;饱和烃和沥青质的碳同位素出现明显的"倒转"现象,这些特征均表明该区至少经历了2期油气充注成藏作用。同时,在塔深3井鹰山组的储层方解石中检测到发黄色、黄绿色、蓝色荧光的油包裹体和气包裹体,根据包裹体的均一温度判断存在3期油气充注,分别为:加里东晚期—海西早期、海西晚期及喜马拉雅晚期。结合井区原油现今的物性(超重质油)及成熟度(成熟油)分析,应以第一期原油充注为主。

Well TS3 is the first discovery well in the deep Ordovician of Tahe oil field. Commercial oils were tested in the Yingshan Formation of the Middle-Lower Ordovician. The physical characteristics of oils from TS3 well block are similar to those from nearby near-surface reservoirs, which both are super heavy oils with high freezing point, high sulfur content, high wax content and high viscosity. The n-alkane series are complete with a variable hump in the chromatographic baselines and widespread 25-norhopane series. The carbon isotopes of saturate hydrocarbons and asphaltenes are partly reversed. These features indicate that the reservoirs in TS3 well block underwent at least 2 periods of hydrocarbon filling and forming. In addition, oil inclusions with yellow, yellow-green and blue fluorescence and gas inclusions were tested in calcites of the Yingshan Formation reservoir. The homogenization temperature of inclusions suggests three periods of hydrocarbon filling：Late Caledonian-Early Hercynian, Late Hercynian and Late Himalayan. Combined with physical properties （super heavy oils） and maturity （mature oils） of the present oils, the first period of oil and gas filling was dominant in the TS3 well block.