松辽盆地北部古中央隆起带变速成图方法

Variable velocity mapping method in Palaeocentral Uplift Belt of North Songliao Basin

地震资料解释中时深转换是非常重要的环节,在古中央隆起带地区利用常规方法绘制的构造图误差比较大,为此提出了一种新的方法:因为钻至T_2反射层的井比较多,相对来说时深转换的速度比较准确,再把T_2至目的层的速度计算出来,就可以得到目的层以上的平均速度,这样就可以比较准确地完成时深转换,编制出更符合实际地质情况的构造图。依据以上方法,对古中央隆起带地区的T_5、T_(4-1)T_4、T_(3-2)、T(3-1a)、T_(3-1)、T_3反射层分别求取了至T_2反射层的层速度,再利用T_2反射层以上平均速度,从而得到了各目的反射层以上的平均速度,进行时深转换,编制出7个目的反射层的构造图。经过误差分析表明,利用这种方法编制的构造图的精度有了很大地提高。

Time-depth eonversion is very important link of seismic data interpretation. The error of drawn struetural map by eonventional method in palaeoeentral uplift belt is rather serious, so the paper presents a new approach： for so many wells drilled through T2 reflection formation and the velocity of time-depth conversion is pretty accurate to a certain degree, if the veloeity from T2 to target formation calculates, the average velocity above the target layer can be obtained and then much aeeurate time-depth conversion can be performed and furthermore the drawn structural map ean well accord with actual geologieal conditions. Aeeording to the above means, the layer veloeities from refleetion interfaces T5 , T4_1 , T4, T3-2 , T3-1a, T3-1 , T3 to T2 are seperatively got in palaeo-eentral uplift belt and then with the help of the average veloeity above reflection interface T2, the average veloeities above eaeh reflection interface ean be gain and then time-depth eonversion can be eonduct easily and finally the struetural maps of total 7 reflection interfaces can be compiled. Through error analysis, the accuracy of eompiling structural map by this method is proven aeeurate to a great deal.