塔中北斜坡走滑断裂断距对碳酸盐岩油气藏的影响

Study on the Influence of Strike-slip Fault Displacement on Reservoir in Northern Slope,Tazhong Area

塔中北斜坡奥陶系碳酸盐岩的储层改造和油气分布,都受到走滑断裂的影响。由于区域内较大规模的走滑断裂均表现为北东向,水平断距较小,使得利用地震资料直接计算断距时存在着较大的困难。实际上,走滑断裂还普遍表现出北西向拉张特征,并沿断裂走向形成了宽度不同的拉分区域。断裂多沿北东向平直延伸,表明这些拉分区域的宽度和高度主要是受局部应力作用而形成的。这些拉分区域的宽度和高度在三维地震资料中较容易识别。根据断裂的拉分特征,提出通过计算拉分区域的宽度和高度间接识别走滑断裂的断距的方法。断距计算结果符合走滑断裂发育的地质规律,断距较大处是走滑断裂活动性较强的区域,同时也是储层改造作用强烈和油气分布较好的区域。

Reservoir reformation and petroleum distributions in Ordovician carbonate reservoirs are affected by strike-slip faults with northeast direction in the Northern Slope of Tazhong area.Large scale strike-slip faults al-ways show north-east strike direction.Unfortunately,the horizontal displacement is too shorter to be identified by using poor quality and low resolution seismic data.Strike-slip faults show ubiquitous pull-apart areas along the strike direction,because they have been affected by the tensional stress with northwest direction.And pull-apart areas are developed along the direction of strike-slip faults mainly affected by the formation of local stres-ses.The width and height of these areas are easy to be identified in 3D seismic data.A method is then proposed for displacement calculation by using the width and height of the pull-apart area to replace the horizontal dis-placement and vertical displacement of fault.Displacement calculation results by this method show a high agreement to geology regularity of strike-slip faults development.Large displacement in strike-slip faults al-ways means a high activity regional area,and also shows a profitability area for reservoir reformation or petro-leum accumulation.