【摘要】 浅水无定位拖缆在近岸海洋工程及浅水多道地震勘探中应用广泛,但受无定位拖缆实际位置获取的限制,野外观测系统准确定义受影响.基于传统直线假设的观测系统定义简单易行,但计算的共反射点面元无法获得实际坐标,位置偏差较大,严重影响后续处理方法的有效应用.基于实际炮点轨迹坐标,本文提出了一种新的无定位拖缆实际坐标计算方法,新方法首先确定接收排列的相对空间位置,采用反距离比线性插值算法准确计算接收道实际坐标值,再根据实际坐标重新定义观测系统,获得了实际跑航弯曲测线观测系统图.文中对传统方法与新方法定义的不同观测系统数据,分别采用SRME(Surface-related Multiple Elimination)方法压制浅水海底鸣震类自由表面相关多次波,结果显示采用新方法定义的观测系统反射数据多次波衰减效果明显,有效反射连续,基底反射成像清晰,说明文中实际坐标计算方法符合海上弯曲测线观测系统的定义,提高了SRME方法压制多次波的效果.更多还原

【Abstract】 Defining the precise seismic geometry is very important for seismic data processing and interpretation. The short receiving cable with a non-position device is widely used in seismic exploration in shallow water, while its geometry definition meets some problems when processing the seismic data without the actual GPS position. Because it is difficult to acquire the true position information for the non-position cable in field prospecting, we usually rely on the assumption based on traditional linear geometry. The traditional method is simple to use, but it cannot get the actual X and Y coordinates and produces some errors in the CMP(Common Middle Point) location and the result of stacked folds, that seriously affects the subsequent modules’ processing, such as the SRME method to attenuate surface-related multiples as reverberation, in which the energy is very strong in shallow water’s seismic data, affecting the interpretation of actual reflector events. To avoid the error in the traditional method based on the linear geometry assumption, we propose a new algorithm to define the non-position short cable receivers’ geometry. Based on the actual precise shots’ track line position, this new method first determines the short cable receivers’ relative space to the shots’ track line. Then it uses the inverse distance ratio and linear interpolation algorithm to calculate the actual X and Y coordinates of each receiver in the short cable. Next we use these actual shots and receivers’ X and Y coordinates to precisely define the crooked geometry, which is adapted to the actual crooked lines’ situation. In order to check the reliability of such a definition for seismic geometry, we use the actual non-position short cable’s seismic data from the Dongji Island in the offshore Zhoushan area to test the traditional method and the new algorithm. The results show that when using the new algorithm to define the actual seismic data geometry, SRME can effectively attenuates the surface-related multiples such as reverberations and ghost waves. While using the traditional linear assumption’s geometry definition method, SRME cannot achieve such an effect. It can be obviously seen from the actual stacked data. So we can conclude that the new defining method of seismic geometry presented in this paper is valid to the non-position short cable’s seismic data in shallow water,and its results meet the actual crooked track line, and are valuable to the subsequent processing such as SRME to attenuate multiples. So it can be widely used to the actual data, especially to that of seismic surveys with a short non-position cable in shallow water.更多还原