Super-virtual Interferometry for noise elimination on vertical seismic profiling (VSP)

Vertical seismic profiling (VSP) datasets often suffer from significant incoherent noise caused by poor coupling between receivers and boreholes. This problem is observed in both the standard VSP, where seismograms are recorded using receivers within the well, and the distributed acoustic sensing vertical seismic profiling (DAS-VSP), where a fiber cable acts as a line of receivers. The presence of this incoherent noise poses challenges in accurately picking direct-wave traveltimes and can lead to inaccuracies in subsequent inversion and modeling results. To alleviate this problem, a super-virtual interferometry (SVI) technique is proposed to enhance the VSP arrivals. Our approach is implemented within a tapered window centered around the initial guess travel time information, with the goal of improving the signal-to-noise ratio (SNR). The key idea of SVI involves generating diffraction gathers by convolving different recorded traces with the same active surface source. This process results in virtual diffraction data that correspond to the respective source locations. By calculating the cross-correlation of these different virtual diffraction datasets and performing a stack, a gather with a common forward and backward propagation path is obtained. Finally, by applying convolution and stacking operations once again, the enhanced VSP direct wave mode is obtained. The proposed technique is tested using one synthetic and two field datasets; the first is a reversal VSP dataset, and the second is a DAS-VSP dataset.