Improved eigenvalue-based coherence algorithm with dip scanning

Abstract

Detection and identification of subsurface anomalous structures are key objectives in seismic exploration. The coherence technique has been successfully used to identify geologic abnormalities and discontinuities, such as faults and unconformities. Based on the classic third eigenvalue-based coherence ([Formula: see text]) algorithm, we make several improvements and develop a new method to construct covariance matrix using the original and Hilbert transformed seismic traces. This new covariance matrix more readily converges to the main effective signal energy on the largest eigenvalue by decreasing all other eigenvalues. Compared with the conventional coherence algorithms, our algorithm has higher resolution and better noise immunity ability. Next, we incorporate this new eigenvalue-based algorithm with time-lag dip scanning to relieve the dip effect and highlight the discontinuities. Application on 2D synthetic data demonstrates that our coherence algorithm favorably alleviates the low-valued artifacts caused by linear and curved dipping strata and clearly reveals the discontinuities. The coherence results of 3D real field data also commendably suppress noise, eliminate the influence of large dipping strata, and highlight small hidden faults. With the advantages of higher resolution and robustness to random noise, our strategy successfully achieves the goal of detecting the distribution of discontinuities.

Microseismic Full Waveform Modeling in Anisotropic Media with Moment Tensor Implementation

“…Strong seismic anisotropy is often observed in shale and reservoirs which contain lots of natural and/or induced fractures (Johnston and Christensen 1995;Schoenberg and Sayers 1995;Vernik and Liu 1997;Wang 2002;Wang et al 2007;Yan et al 2016).…”

Multispectral coherence

“…Twenty years after its inception in the mid-1990s, seismic coherence volumes are routinely used to delineate structural and stratigraphic discontinuities such as channels, faults and fractures, to highlight incoherent zones such as karst collapse and mass transport complexes, and to identify subtle tectonic and sedimentary features that might otherwise be overlooked on conventional amplitude volumes (Ogiesoba and Hart, 2009;Sun et al, 2010;Li et al, 2015;Qi et al, 2017). Estimates of seismic coherence (Bahorich and Farmer, 1995;Marfurt et al, 1998;Gersztenkorn and Marfurt, 1999;Lu et al, 2005;Wu, 2017;Yan et al, 2017) that highlight changes in seismic waveform or amplitude across a discontinuity provide a quantitative measures of the geological discontinuity.…”