大型控盆边界正断层活动性评价方法及应用

Evaluation method of large boundary normal fault activity and its application

裂陷区存在大量缺失下盘地层沉积的控盆主边界正断层,这类断层的运动学特征对认识盆地的结构、沉积充填及油气成藏都具有重要意义。然而目前还没有一种有效的该类断层活动性评价方法,为此,以油区构造解析理论为指导,在已有断层活动性评价方法调研基础上,通过断裂活动与沉积充填响应关系的系统分析,提出了一种新的评价方法——地层楔形体法。断层的活动过程是上盘楔形地层超覆体的形成过程,某一地质时期内,因断层活动的阶段性而发育多个地层楔形体,所有地层楔形体的视厚度就代表了地层沉积时期的断层活动产生的垂距。文中将地层楔形体法应用于沙南—埕北地区,对缺失下盘地层沉积控盆边界断层的活动性做了评价,明确了沙三段沉积时期断层活动强烈。

Faulted depression area has massive main boundary normal faults with lost sedimentary strata in footwall. Kinematic characteristics of this type of fault have important significance to recognize basin structure, sedimentary filling and hydrocarbon accumulation, but there is not an effective method to evaluate fault activity. In order to solve the issue, a new method, formation wedge method, was proposed, which was based on oilfield structural analysis theory, the research of existing fault activity evaluation method, the systematic analysis of fault activity and sedimentary response. Wedge-shaped layer body developed in hanging wall is caused by fault activity. In a geological period, due to phase feature of fault activity and multiple stratigraphic wedges development, the apparent thickness of all formation wedges represents vertical distance induced by fault activity in different period. The formation wedge method was applied to Shanan-Chengbei Area to evaluate the activity of boundary faults in this area, and the result shows that the faults acted strongly in Sha-3 Member sedimentary period.