塔中北斜坡走滑断裂断距及其与油气的关系

The Effect of Strike-Slip Faulting Throw on Hydrocarbons in Northern Slope of Tazhong Area,Tarim Basin

塔中北斜坡奥陶系碳酸盐岩储集层内的油气分布受北东向走滑断裂的影响,走滑断裂的断距影响着油气富集的程度。由于储集层埋藏较深,用来描述储集层分布的三维地震资料的分辨率和信噪比都较低,使得利用地震资料计算断距比较困难。又由于走滑断裂的水平断距过小,垂向断距变化较大,进一步影响着断距的计算。为此通过三维地震资料分析发现,走滑断裂普遍表现出北西向拉张的特征,并沿断裂走向形成了宽度不同的拉分区域。根据拉分特征,提出通过计算走滑断裂拉分区域的宽度和高度的方法,来间接确定走滑断裂的断距。计算结果不但符合走滑断裂发育的地质规律,还同该区域的油气分布有较好的吻合性,能够用来认识区域内油气的分布。

Petroleum distribution in carbonate reservoirs of Ordovician in northern slope of Tazhong area are affected by N-E strike-slip fault, and the hydrocarbon enriehmeut is controlled by the fault throw. But the fault throw is difficult to calculate due to deep-buried reser- voir, low resolution and signal to noise ratio of 3D seismic profiles describing the reservoirs distribution as well as the too-small horizontal fault throw and the varied vertical fault throw of this strike-slip fault. The further analysis of the 3D seismic data shows that the strike-slip fault was of the feature of N-W extension and formed extensional-apart regions with different widths along the fault strike. A method is then proposed in this paper for calculating the strike-slip fault width and height of extensional-apart regions to indirectly recognize and deter- mine the fault throws. The results indicate that this method can be used to recognize the hydrocarbon distribution in this area, because of its high agreement to the strike-slip fault development regularity and good coincidence to the oil-gas distribution in this area.