## 4 Results  
The process of transforming the data collected from DAS into Common Depth Point (CDP) domains is a complex one that requires several crucial steps. One of the first steps in this process is the ease of picking first arrivals and separating the up- and down-going wavefields, while also accounting for any noise that may be present due to the various cable combinations and deployments used. To ensure that the data is accurate, depth calibration is necessary by comparing it against geophones at the bottom of the well. However, this process can be difficult as the attempt to define depths using tap tests may not match up with the geophone data. In our study, the existing CaMI cable was used for calibration, but shot statics were derived as the sources occupied different locations. However, during the signal processing, the deployment for the tubing installation did not proceed, as the SNR was very low and the seismic amplitude was weak.  
In our field study, the next step, picking first breaks, was most straightforward when using the cemented cable data, as this method provided the best coupling with the surrounding earth. However, picking first breaks proved more difficult when using other methods, such as the liner or tubing deployment. This is because these methods can lead to weaker signals and higher levels of noise, making it harder to distinguish the first arrival times.  
During the imaging process, timing jitter in the data needs to be smoothed out and the use of a fine 20-cm sampling interval acts as a benefit. Deconvolution of the up-going wavefield using the down-going wavefield as a source signature helps to attenuate multiple reflection energies and enhance the bandwidth of the up-going wavefield. The final imaging stage of the VSP-CDP transform using ray tracing through the pre-defined velocity model resulted in excellent images for the cemented cable data (Figure 6) and the cables behind inflatable liner (Figure 7). However, the image for the cable as wireline in the water-filled well (Figure 8) was limited to an extent, as only seven short offset shots could be used. As for strapped to tubing deployment, the SNR was very low, making the gather unable to be used for DAS VSP processing (Figure 9).  
Figure 6: VSP to CDP transform in time (ms) for the cemented cable.  
Data attenuation occurred in all the deployment methods, most severely from the fiber on tubing installation in which the VSP data were unable to be imaged. The attenuation of DAS VSP data can lead to reduced SNR and affect the quality of the seismic data. Several issues were identified as the cased for poor SNR in the deployment. In wireline and on tubing installation, poor coupling between the fiber-optic cable and the surrounding medium led to a weak signal that was difficult to detect over background noise. To mitigate this, it is important to ensure that the fiber-optic cable is properly installed and in good contact with the surrounding medium as indicated in the permanent behind casing and via inflatable liner.  
Strong tubing waves can be observed when the fiber-optic cable is deployed inside the tubing as wireline and on the tubing itself. Tubing waves are acoustic waves that propagate along the tubing and cause interference with the DAS VSP measurements. This interference led to a reduction in the SNR and affected the quality of the VSP data for these two deployment methods.  
Figure 8: VSP to CDP transform in time (ms) for the cable as wireline in WATER.  
Figure 7: VSP to CDP transform in time (ms) for the cable installed behind inflatable liner.