鄂尔多斯盆地中部上古生界流体包裹体特征及油气充注史

Fluid inclusion characteristics and hydrocarbon charge history in the Upper Paleozoic, central Ordos Basin

通过流体包裹体显微岩相学观察、均一温度和冰点温度测定、激光拉曼光谱分析,结合单井埋藏史、热史和成熟度史模拟,分析鄂尔多斯盆地中部上古生界油气充注历史。结果表明:研究区次生流体包裹体可划分为3大类、7个亚类,烃类和CO_2包裹体发育序列为黄色荧光烃包裹体→蓝色荧光烃包裹体→CO_2气包裹体→甲烷气包裹体;上古生界烃源岩在盆地南部最早进入生烃阶段,演化程度也最高,从南向北,烃源岩进入生烃的时间依次变晚,演化程度也逐渐降低;上古生界储集层主要经历两期油气充注,中晚三叠世,盆地中南部开始进入生油阶段,原油在中侏罗世早期充注到陕360和苏325地区,形成发蓝色荧光和少量黄色荧光的液态烃包裹体,未能形成工业性油藏,早白垩世中期,大量天然气生成,由南向北充注到伊陕斜坡北部,且持续到早白垩世晚期构造抬升之前,形成多个大规模工业性气藏。

Hydrocarbon charge history in the Upper Paleozoic, central Ordos Basin was investigated using a series of data from observations of an integrated fluid inclusion petrology, homogenization and ice melting temperatures measurements, laser-raman spectrum and one dimensional thermal and maturity modeling results. The results indicate that three types and seven sub-types of epigenetic fluid inclusions are divided in the Upper Paleozoic reservoir. Hydrocarbon and CO2 inclusions are developed mainly following the sequence of yellow fluorescence oil inclusions, blue fluorescence oil inclusions, CO2 gas inclusions and methane inclusions. Compared with the central and north part of area, the Upper Paleozoic source rocks in the southern part of the Ordos Basin first entered hydrocarbon generation stage and reached the highest maturity evolution stage, and show a declining trend from south towards north. Two episodes of hydrocarbon charges occurred in the Upper Paleozoic, central Ordos Basin. Hydrocarbons began to generate in the southern part of the basin during Middle to Late Triassic, and charged into the Su-325 and Shan-360 areas at early of the Middle Jurassic, forming mostly blue fluorescence and few yellow fluorescence oil inclusions. Massive natural gases were charged into the north part of the Yishan Slope Region from south to north at middle of the Early Cretaceous, and lasted until late of the Early Cretaceous, forming several giant gas fields.