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以坡折带理论为基础,按照成因机制,在柴达木盆地昆北—阿拉尔地区识别出3种类型坡折带,即构造坡折带、沉积坡折带和侵蚀坡折带。昆北断裂坡折带和阿拉尔断裂坡折带属于构造坡折带;跃进Ⅱ—Ⅳ号、昆仑山前坡折带属于沉积坡折带;铁木里克坡折带属于侵蚀坡折带。坡折带对沉积体系和岩性圈闭发育具有明显的控制作用,构造坡折带控制低水位期近岸三角洲扇体和浊积扇扇体的形成,主要发育河道透镜体型岩性圈闭;沉积坡折带主要控制了低水位期辫状河三角洲扇体的发育,侵蚀坡折带控制了低位期充填的侵蚀谷岩性圈闭。根据研究区沉积、储层、油源及运移等成藏条件,开展了坡折带背景下的岩性圈闭预测与评价,总结其岩性油气藏发育成藏模式,综合分析认为跃进Ⅱ—Ⅳ号和尕斯坡折带是发育岩性圈闭的有利区块。
Based on the slope break zone theory, according to the genetic mechanism, three types of slope break zones are identified in the Kunbei-Alar region of the Qaidam Basin, namely, structural slope break, sedimentary slope break and erosion slope break. Kunbei fault slope break belt and Aral fault slope break belts belong to structural slope break belt; Yuejin Ⅱ-Ⅳ, Kunlun mountain slope break belts belong to sedimentary slope break belt; Tiemurike slope belts belong to erosion slope break belt. The slope break zone plays a significant role in controlling the sedimentary system and lithologic traps. The structural slope break zone controls the formation of nearshore delta fan and turbidite fan sectors at low water level, and mainly develops the lenticular lithologic traps. The sedimentary slope break zone mainly controls the development of braided river delta fan in the low water level period, and the erosion slope break zone controls the eroded valley lithologic trap in the low period. Based on the reservoir conditions such as sedimentation, reservoir, oil source and migration in the study area, prediction and evaluation of lithologic traps in the slope break zone are carried out. The development and accumulation pattern of lithologic reservoirs are summarized. According to the comprehensive analysis, Zone IV and Gasse slope fold are favorable blocks for the development of lithologic traps.