库车坳陷迪北气藏2期油气充注古流体证据

Palaeo-fluid Evidence for the Two-stage Hydrocarbon Charges in Dibei Gas Reservoir of Kuqa Depression

采用包裹体岩相学观察、显微测温、储层定量颗粒荧光分析、红外光谱分析及油气地球化学分析等方法,从古流体证据的角度对迪北气藏的油气充注历史进行研究。结果表明迪北气藏具有2期油气充注特征:第Ⅰ期主要源自三叠系湖相烃源岩排出的油,对应于镜下发浅黄色荧光的油气包裹体,红外光谱分析表明其成熟度相对较低,定量颗粒荧光分析表明存在古油藏,也是此期原油充注的证据;第Ⅱ期主要源自侏罗系煤系烃源岩排出的天然气,对应于发蓝白色荧光的油气包裹体,红外光谱分析表明其成熟度相对较高,且此期高成熟天然气充注使得早期充注的原油遭受气洗脱沥青作用。迪北气藏的2期油气充注使其具有中新世早中期的原油充注、上新世以来的致密深盆气藏叠加、西域期以来的致密气藏调整改造再富集的成藏过程。

According to the observation of fluid inclusion petrological characteristics,microthermometric analysis,reservoir quantitative grain fluorescence analysis,infrared spectrum analysis and hydrocarbon geochemistry analysis,hydrocarbon charging history of Dibei gas reservoir has been researched comprehensively from the perspective of paleo-fluid evidence.The result shows that Dibei gas reservoir has two-stage hydrocarbon charging history.The oil discharged in phaseⅠ is mainly derived from the Triassic lacustrine source rocks and it corresponds to light yellow fluorescent hydrocarbon inclusions.The infrared spectrum analysis shows that the maturity of the oil is relatively low.Moreover,the existence of paleo-oil reservoir also can be verified by the analysis of quantitative grain fluorescence,which are also the evidences of oil discharge.The gas discharged in phaseⅡ is mainly derived from the Jurassic coal-measure source rocks and it corresponds to blue-white fluorescent hydrocarbon inclusions.The infrared spectrum analysis shows that the maturity of the gas is relatively high.The oil charged at earlier stage has been gas-flushed and deasphalted because of the charge of high-mature gas.Hydrocarbon charging processes of Dibei gas reservoir has been established:(1)charged with oil at the earlymiddle period of the Miocene;(2)charged with the superposition of deep basin gas reservoir in Pliocene;(3)charged with adjustment,modification and re-enrichment in Xiyu period.