Pyrite dikes and tuff dikes in shale oil reservoir of Qingshankou Formation, Gulong Sag and their significances

Key words: 
• Pyrite dike, tuff dike, liquefaction, gravity fall, shale oil, Gulong Sag

Abstract: Gulong shale oil is an important replacement resource in the Songliao Basin, with an estimated resource amount of 15.1 billion tons. From the perspective of sedimentary and petrological characteristics, the most prominent feature of Gulong Qingshankou Formation shale is the extensive development of sand dikes, which is not found in shale oil reservoirs in other basins. Therefore, this is also an important information to explore the formation environment of Gulong Qingshankou Formation shale. The most peculiar thing is that in addition to sand dikes, there are two other special dikes in Gulong Qingshankou shale: pyrite dikes and cementite dikes. Pyrite dikes and cementite dikes are generally small in scale, with widths of 1-2 mm. Visible length several centimeters; Mostly curved like intestine, a few slightly curved. Multi-tilt output, tilt direction has a certain rule, 180° symmetry. The pyrite dikes in the shale oil reservoir of Qingshankou Formation in Gulong are formed by late pyritization of sand dikes. The cementation dikes are formed by gravity subsidence caused by density inversion and the formation kinetics of pyrite and tuff dike are also studied. The study of pyrite dikes and puffite dikes in the Gulong shale oil reservoir has three significances: first, the formation time, sedimentary environment, sedimentary process and sediment state of pyrite dikes and tuff dikes can be known; Second, the diagenetic compaction rate of shale can be known. Third, it can assist reservoir evaluation.