X型正断层交汇处应力分布及其油气地质意义

Stress Distribution at the Intersection of X-pattern Normal Faults and Its Significance in Petroleum Geology

为了查明X型正断层夹角变化对应力分布特征及油气运聚的影响,应用FLAC3D软件建立了X型正断层夹角自15(°)至90(°)变化的6种模型,并对其交汇处应力场分布特征进行了三维数值模拟分析。结果表明:断裂交汇部位垂直应力表现为挤压性质的力,不明显受相交角度变化的影响,而水平应力主要为拉张性质的力,当θ大于45(°)后出现挤压应力;断裂交汇部位水平、垂直应力集中程度具有先增大后减小的变化规律,垂直应力大小较水平应力明显大一个数量级,当相交角度为45(°)时,水平、垂直应力集中程度达到最大。应力高集中区能够释放大量应变能,有利于油气的运移和聚集,因此,交角为45(°)的X型正断层是油气富集的有利区。

In order to find out the influence of the change of angle between X-pattern normal faults on stress distribution and hydrocarbon migration and accumulation,six models of the change of angle between 15 and 90 degrees of X-pattern normal faults are established by FLAC3D software.The distribution characteristics of stress field at the intersection of X-pattern normal faults are analyzed.The results of three-dimensional numerical simulation show thatthe vertical stress at the fracture junction is a force of extrusion,not obviously affected by the change of intersection angle,while the horizontal stress is mainly a force of tension.When theta-form is greater than 45 degrees,the compression stress occurs.The horizontal and vertical stress concentration at the fracture junction increases first and then decreases.The magnitude of force is an order of magnitude larger than that of horizontal stress.When the intersection angle is 45 degrees,the concentration degree of horizontal and vertical stress willreach the maximum.The high stress concentration area can release a large amount of strain energy,which is conducive to the migration and accumulation of oil and gas.Therefore,the X-pattern normal faults with an angle of 45 degrees is a favorable area for oil and gas enrichment.