The Green's function between two receivers can be retrieved using seismic interferometry (SI) by cross-correlation, as if one of the receivers were a virtual seismic source. When the wavefields experience intrinsic losses during propagation, non-physical arrivals (ghosts) would appear in the retrieved result. These ghosts are a result of internal reflections inside the different layers lying between the subsurface sources and the receivers. Recent studies have introduced a stable method to monitor the layer-specific changes in quality factor (Q) using the ghosts retrieved by SI applied to a horizontal-well data. However, drilling a horizontal well is much more complicated and expensive than drilling a conventional vertical well. Because of this, we show here how the Q-estimation method introduced for the horizontal well can be adapted to monitor layer-specific changes of Q using a vertical well. In order to improve the accuracy of the Q-estimation, we propose a grid-searching method to detect the optimal effective Q. We illustrate our method using numerically modelling data from a horizontal and a vertical well.@en