鄂尔多斯盆地X地区延长组长7油层组致密油藏流体包裹体特征及成藏期次

Hydrocarbon accumulation dating by fluid inclusion characteristics in Chang 7 tight oil reservoirs of Yanchang Formation of X Area,Ordos Basin

利用包裹体显微测温、显微荧光、显微红外光谱分析技术，结合埋藏史和热史模拟分析，探讨了鄂尔多斯盆地东南部x地区延长组长7油层组成藏期次．结果表明：研究区长7油层组主要发育两期油气包裹体，第l期油气包裹体沿石英颗粒次生加大内侧分布，或沿未切及石英颗粒次生加大边的成岩微裂缝，或成群、成带分布于长石颗粒内等，同期石油包裹体成分中长链烷烃质量分数相对较高，成熟度较低，同期盐水包裹体均一温度峰值为80～100℃；第2期油气包裹体沿切穿石英或长石颗粒的晚期微裂缝成线状或带状分布，同期石油包裹体成分中长链烷烃质量分数相对较低，成熟度较高，同期盐水包裹体均一温度峰值为85～100℃．综合分析认为研究区延长组长7油层组存在2期成藏，分别为早白垩世中晚期的大规模石油成藏和晚白垩世晚期到古近纪早期的晚期构造抬升调整成藏．

In combination with simulation analysis of the burial and thermo-evolutionary history of Chang 7 Oil Group, accumulation periods of Chang 7 Oil Group of Yanchang Formation in X Area, southeastern of Ordos Basin were studied by analyzing fluid inclusions through microfluorometric, microscopic thermometry and microscopic infrared spectroscopy. The results showed that there were two periods of hydrocarbon inclusion in Chang 7 reservoirs of X Area. The hydrocarbon inclusions formed in the first phase mainly occurred inside the quartz overgrowth, or in the diagenetic microfracture zone by cutting and being located in the quartz overgrowth, or lying inside the feldspar particles in groups and in zones. The components of oil fluid inclusions in the first phase had a higher content value of long chain alkane, a lower maturity value, and the homogenization temperature of accompanied saline inclusions was 80- 100 ~C. The hydrocarbon inclusions formed in the second phase were mainly distributed along the lateformed fractures cut by quartz or feldspar in threadinesses and in zones. The components of oil fluid in- clusions in the second phase had a lower content value of long chain alkane and a higher maturity value, and the homogenization temperature of accompanied saline inclusions was 85-100 ℃. Two periods of hydrocarbon accumulation of Chang 7 Oil Group of Yanchang Formation in the studied area were the early period of mature oil accumulating in a large scale at the mid-late stage of early Cretaceous, and the late period of adjusting accumulation from late stage of late Cretaceous to early Paleogene.