库车克拉2气田多期油气充注的古流体证据

Palaeo-fluid evidence for the multi-stage hydrocarbon charges in Kela-2 gas field, Kuqa foreland basin,Tarim Basin

对库车前陆盆地克拉2气田储集层进行流体包裹体分析、荧光光谱分析、场发射扫描电镜观察、岩心显微CT扫描及油气地球化学分析,从古流体证据的角度综合研究克拉2气田多阶段油气充注过程。克拉2气田经历了中新世早中期(N1)原油充注、上新世库车组沉积期(N2)高成熟油气充注与破坏、第四系(Q1以来)高—过成熟煤成气充注的3期成藏过程。储集层中广泛分布的残余干沥青、较发育的气液两相烃包裹体、纳米孔中的残余油、现今气层和水层中较高的颗粒(抽提物)荧光指数、储集层岩石较大的热解值等均是早期原油充注的证据;残余干沥青、含沥青的3相烃包裹体、凝析油轻质正构烷烃大量损失、石蜡质和芳烃等重组分含量相对较高、金刚烷含量异常高等均是早期原油遭受气洗发生脱沥青作用的有力证据。

The multi-stage hydrocarbon charge process of Kela-2 gas field in the Kuqa foreland basin was studied from the perspective of palaeo-fluid evidence by the analyses of fluid inclusions, fluorescence spectroscopy, FE-SEM （field emission scanning electron microscopy） observation, core micro-CT scanning, and hydrocarbon geochemistry. The result shows that the Kela-2 gas field has experienced three periods of hydrocarbon charge process： （1） charged with oil at the early-middle period of the Miocence （N~）, （2） charged with high maturity oil ＆ gas at the sedimentary period of the Pliocence Kuqa Formation （N2） and then destroyed by intense tectonic compression, and （3） charged with high-over maturity coal-derived gas since the Quaternary. The widely distributed residual dry bitumen, the occurrence of gas-liquid two-phase hydrocarbon inclusions, the residual oils observed in the nanopores, the higher QGF and QGF-E index, and the higher S], $2 values of rock pyrolysis detected in both current gas zone and water zone, are the evidence of early oil charges. The residual dry bitumen, the occurrence of gas-oil-solid （bitumen） three-phase hydrocarbon inclusions, the loss of light n-alkanes and the relatively high content of aromatic hydrocarbons in the condense oil, and the abnormally high content of diamondoid hydrocarbons, are the strong evidence of gas flushing and deasphalting.