陆相断陷盆地层序类型及隐蔽圈闭预测

对中国东部古近系和新近系陆相断陷盆地层序地层的研究结果表明,陆相断陷盆地存在着同生断裂坡折带、弯折带2种基本的坡折带类型.当水平面下降到坡折带以下时,构成一个完整的水平面升降旋回,可形成包括低水位、湖扩展、湖萎缩3个体系域的层序(三分体系域);当水平面未下降到坡折带以下时,构成一个不完整的水平面升降旋回,可形成包括湖扩展、湖萎缩2个体系域的层序(二分体系域).这2种层序在纵向上有规律的叠置组合就构成了盆地层序充填序列.水平面上升期是寻找充填作用形成的水下扇(低水位扇)、小型(扇)三角洲(低水位楔)隐蔽圈闭的有利层序地层部位;而水平面下降期则是寻找(扇)三角洲前缘滑塌作用形成的浊积扇隐蔽圈闭的有利层序地层部位.

Sequence Types and Subtle Reservoirs Exploration in Continental Rift-Subsidence Basin

By means of studies on sequences in continental fault depression of Tertiary in Eastern China,this paper shows two basic kinds of slope-break: syndepositional fault slope-break and bend slope-break.When the horizontal level falls down the slope-break,a full horizontal level fluctuating cycle is formed,a system including lowstand tract,lake expand and lake shrink(trisection tracts).When the horizontal level cannot fall down the slope-break,an imperfect horizontal fluctuating cycle is formed,a system of lake expand and lake shrink(dimidiate tracts).The regular vertical superimposition of two sequences makes the sequence filling of the basin.It is found that the ascending level is the best place to locate the submarine fan(lowstand fan),small-size fan-delta(lowstand wedge) formed by the filling and that the descending level is the best to find subtle traps of turbidity fan formed by the slump of the fan-delta front.