用时距曲线方程研究四维地震时差

Study on 4D seismic time difference using traveltime-distance equation

1. 大庆勘探开发研究院,黑龙江大庆163712;2. 石油大学资源与信息学院,北京102200

1. Daqing Research Institute of Exploration and development, Daqing 163711, China;2. Resource and Information Institute of Petroleum University, Beijing 102200, China

时移地震在油藏监测方面发挥着越来越大的作用,尤其是使用该方法确定地下油水的分布。然而,对于注水开发而言,由于油水的速度差别较小(水中的速度大约为1480m/s,油中的速度为1027～1320m/s),因此,水驱油后储层的速度变化并不十分明显,导致水驱油后储层的时差变化很小,一般很难确定。而时移时差在确定地下油水分布时是一个很重要的参数,因为时移时差包含了储层速度的变化信息。从地震反射时距方程出发,推导了用叠前地震数据求取时移地震时差的方法,从文中给出的数学模型计算结果来看,用该方法得到的垂直时移时差非常准确,且不需要层速度信息。

Time lapse seismic is playing an important role in oil reservoirmonitoring, especially in the determination of distribution for underground oil and water. However, it is not obvious for the change of velocity in the reservoir after waterflooding because of the velocity difference between oil and water is small (water velocity is 1480m/s,whereas oil velocity is between 1027m/s and 1320m/s). Therefore, the time difference before and after waterflooding is very small and difficult to determine. Time lapse time difference is an important parameter in the determination of distribution for underground oil and water, because it includes the variation information of reservoir velocity. Starting from reflection traveltime distance equation, this paper presented amethod for getting time lapse time difference from prestack seismic data. Tests onmathematicalmodel show that the vertical time-lapse time difference resulted from thismethod is very accurate and no need the information of interval velocity.