Controlling factors of ghosts and the effects on single-channel seismic exploration

Source ghost and other ghosts affect the quality of marine seismic exploration. The variation of source ghost is mainly controlled by its time-delay relative to the primary. Based on the theories of ghosts and the two-dimensional model supposing sea surface and seabed are horizontal, the formulas including source ghost time-delay, source depth, and source-receiver distance were established. The relationship between source-receiver distance and source depth was visualized and analyzed when real values are taken into the formulas, through which the effects on source ghost could be determined using the source-receiver distance and source depth. After that, the indirect controlling factors of source ghost were studied when the changes of source depth during exploration were taken into account, and the results were verified by factual seismic profiles. Research shows that the shorter source-receiver distance, the more conducive to reducing the damage of ghosts to seismic exploration results. The source-receiver distance has a small impact on deep exploration results, only on the data acquired in where water depth is less than the source-receiver distance, and the affected length of the data is between seabed and the length of the source-receiver distance below seabed. The effect of the source-depth to the source ghost is much greater than that of the source-receiver distance. When water depth is less than 15 m, the response of the variation range of ghost time-delay to the variation of focal depth is about 5 times that of the response to the variation of offset on the same scale. The fluctuation of the sea surface is an important factor leading to the change of the ghosts. The exploration under good sea conditions is conducive to improving the resolution of single channel seismic data and the consistency of its reflection event.