柴达木盆地尕斯断陷断层封闭性及其对油气运聚的作用

影响断层封闭性的主要因素包括:断层的活动性、泥岩涂抹系数、断层两盘的岩性对置关系、断面压力与泥地比的关系。将这4个主要影响因素作为评价参数,结合盆地构造演化,综合研究了柴达木盆地尕斯断陷内断层的垂向、侧向封闭性和封闭史。结果表明,柴西地区断层的封闭性在时空上存在着较大的差异性,并在油气运聚过程中起到不同的作用:当断层作为油气运移通道时,可以连接源岩和圈闭,并且控制着油气在垂向上的运聚层位和运聚时期,如Ⅶ号、Ⅺ号等断层;当断层作为遮挡体时,控制着油气聚集圈闭的形成,如乌南断层;断层活动开启还会引起油气藏的破坏和油气的再分配,如油砂山、南翼山地区的断层。

Sealing capacity of faults and its control on hydrocarbon migration and accumulation in Gas fault depression in Qaidam basin

The key factors that influence sealing capacity of fault include fault activity, shale smearing factor, lithologic juxtaposition on both sides of fault, and relation between pressure on fault plane and shale stratum ratio. Taking these four key influential factors as appraisal parameters and integrating with tectonic evolution of the basin, the vertical and lateral sealing capacities and sealing history of the faults in Gas fault depression in Qaidam basin are studied. It is shown that the sealing capacities of faults vary largely in time and space in western Qaidam basin and have played different roles in hydrocarbon migration and accumulation. When acting as migration pathways of hydrocarbon, the faults would interconnect source rocks and traps and controlled the horizons and times of vertical migration and accumulation of hydrocarbons, such as the Ⅶ and Ⅺ faults. When acting as barrier beds, they would control the formation of traps for hydrocarbon accumulation, such as Wunan fault. Reactivation of faults would destruct oil and gas reservoirs, leading to the redistribution of oil and gas, such as the faults in Youshashan and Nanyishan areas.