Identifying and predicting multiples based on spread of velocity spectrum

The genesis of internal multiples is complicated and identification is difficult as their velocities are similar to the velocity of primaries, so their residual time is short. The existing conventional methods for identifying multiples are mainly used on a single-common mid-point (CMP) or single line, so the result is indistinct and inaccurate. The concept of velocity spread is proposed, whereby multiples are identified by obtaining the lateral spread of energy clusters on the velocity spectrum. The proposed method uses image segmentation to binarise the velocity spectrum, obtain the spread of velocity, and identify and predict multiples on the plane via attribute spread slicing. In a 3D seismic of Sichuan, the multiples predicted are in good agreement with the known wells. The case shows that velocity spread analysis can quantitatively identify and predict multiples interference, and is complementary to the existing multiples identification method. It can be used to monitor the multiples suppression effect in seismic processing and analyse the interference of multiples in interpretation. In addition, the method has good practicability for evaluating the reliability of reservoir prediction results and reduces the risk of well location deployment during exploration.