鄂尔多斯盆地西南部长8致密油层油气成藏期次和时期

Timing and chronology of hydrocarbon accumulation phases of Chang 8 tight reservoir in southwest of Ordos Basin

宋世骏 刘森 梁月霞

西北大学大陆动力学国家重点实验室，陕西 西安 710069 西北大学地质学系，陕西 西安 710069 延长油田股份有限公司富县采油厂，陕西 延安 716000

State Key Laboratory of Continental Dyanmics, Northwest University, Xi′an 710069, China Department of Geology, Northwest University, Xi′an 710069, China Fuxian Oil Production Plant, Yanchang Oilfield Co. Ltd., Xi′an 716000, China

目前对于盆地西南部长8致密油层成藏期次的研究较少，并且研究单一依赖实验测试分析，造成了研究结果存在差异。文中综合致密油层的沉积￣构造演化、成岩￣油气成藏序列、烃源岩特征，利用C，O同位素、储层沥青质、油包裹体显微荧光特征、盐水包裹体均一温度等测试分析方法，结合热史恢复结果，开展鄂尔多斯盆地研究区长8致密储层油气成藏期次和时期研究。结果表明：稳定叠置的砂体致密储层表现出的相对高孔高渗、“东高西低”的构造背景及上覆长7高放射性烃源岩共同为研究区长8致密油层提供了良好的成藏条件。研究区存在2个成藏期次：第1期在130~120 Ma，代表了早期油气生成运移的时间；第2期在105~100 Ma，即早白垩世末期，代表了该区主要油气聚集成藏的时间。

Due to less work, there is little understanding about hydrocarbon accumulation phases of the Chang 8 tight reservoir in the southwest of Ordos Basin, and the previous researches were simply relied on the experimental test and analysis, leading to controversial results. In this paper, we synthesize sedimentary and tectonic evolution, sequences of diagenesis and hydrocarbon accumulation and source rock features, combined with the results of recovery of thermal history, aiming to bring light on hydrocarbon accumulation phases and periods of Chang 8 tight reservoir in the study area. Measurement and analysis methods such as C and O isotopes, asphalt, micro fluorescence characteristics of oil inclusions and homogenization temperature of brine inclusions are employed in the research. Our results indicate that the stably superimposed sand tight reservoirs are characterized by relatively high porosity and permeability, and the "east high west low" tectonic setting and the overlying Chang 7 high radioactive source rocks both provide better hydrocarbon accumulation conditions for Chang 8 tight reservoir in this area. Furthmore, there are two phases of hydrocarbon accumulation in the study area, namely the first phase (130￣120 Ma) during which the early hydrocarbon was producted and migrated, and the second phase (105￣100 Ma) during which the main hydrocarbon accumulated.

10.6056/dkyqt201802002