关键词: 川西坳陷, 须家河组, 古圈闭类型, 隐蔽圈闭, 识别技术, 致密储层

Abstract: The upper Triassic formation is the primary hydrocarbon source rock of the western Sichuan Depression.The second section and forth section of Xujiahe Formation are the main reservoirs.The peaks of hydrocarbon generation and expulsion of the upper Triassic formation appeared in the Late Triassic and Middle-Late Jurassic periods.The early hydrocarbon generation and expulsion led to form oil-gas reservoir early.The reservoir evolvement shows that tightening completed at the end of Yanshanian froze up oil and gas of palaeo-trap.The multi-episodic superimposition of the tectonic movement modified the palaeo-trap and made it complicated and subtle.The analysis on known gas reservoirs and exploration areas shows that there are five types of palaeo-trap including palaeostructural-diagenetic trap,palaeostructural-lithologic trap,palaeostructural trap,superposed structural trap and stratigraphic-lithologic trap.The exploration and research results proved that the Late Indosinian and Yanshanian traps are available.Seeking for palaeo-trap by structure evolvement combining seismic-logging technique is a practical way for gas exploration in the tight reservoir of Xujiahe Formation in the western Sichuan Depression.

Key words: western Sichuan Depression, Xujiahe Formation, palaeo-trap type, subtle trap, identification technology, tight reservoir