Definition of seismic geometry for short non-position receivers and multiples attenuation in shallow water

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.