Method of cable floating correction based on ghost reflection traveltime controlled by coherent analysis

Abstract

The high-resolution and small trace marine seismic exploration method has the characteristics of high dominant frequency and wide frequency band, which is an important means for the study of near-seabed stratigraphic sequence and fine structure, gas hydrate exploration and so on. The particularity of acquisition and the inherent problems of equipment cause unequal floating effect of the cable, resulting in unevenness, even bending and shaking of the in-phase axis on the gathers after NMO correction，which affects the effect of in-phase stacking and reduces the resolution and imaging accuracy of seismic data processing. The conventional residual moveout correction methods such as: interactive pick-up seabed reflection and ghost reflection traveltime fitting method, gather residual moveout correction method, etc., due to the large amount of pick-up, high quality requirements of gathers, and the residual moveout is a comprehensive reflection of the cable unequal floating, inaccurate speed and anisotropy, it is difficult to accurately identify whether residual moveout is caused by the unequal floating of the cable, which will cause errors in the correction results. This paper proposes a cable floating correction method based on ghost reflection traveltime controlled by coherent analysis. Firstly, the ghost reflection traveltime of the seabed reflection and receiver points are interactively picked up on the shot gathers in intervals, the information of all shots is obtained through fitting interpolation, and the real-time depth of the cable is obtained based on the moveout, and the initial moveout correction amount is calculated; Then the reference moveout correction amount is obtained through a two-dimensional coherent algorithm based on model trace constraints. Finally, based on the cross-correlation coefficient, a weighted selection is made to obtain an accurate residual moveout of unequal cable floating, and the moveout is applied after smoothing, the effect of in-phase stacking is achieved, thereby improving the imaging quality of seismic data. The test analysis combining synthetic data and actual processing shows that, compared with the conventional correction methods, the method proposed in this paper is more accurate and effective.