## 6 Conclusions  
The field study conducted to evaluate DAS in a test well revealed that the best method for coupling the DAS cable to the earth is to install it with the casing at the time of drilling, when and if possible. The study found that deploying the cable in a water-filled well did not yield good results and imaging DAS VSP for on-tubing deployment was not possible due to low SNR. The use of an inflatable liner to push the cable against the side of the wellbore was found to be the best alternative for a free well. The DAS cables also needed to be depth calibrated against a reference, as tap tests were not found to be reliable. The extent of the DAS cable from the surface to near the bottom of the well enabled the construction of a comprehensive and detailed velocity model. It was also important to correct for source statics due to differences in elevation or local weathering effects in order to obtain the optimal resolution in the final image. With careful processing and attention to detail, the fine resolution of the DAS fiber optic cables can yield excellent results and provide an image that covers most of the depth range of the well, significantly better than geophones due to their limited depth range and generally poorer vertical resolution.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{1}{c}{**Parameter to Be**} & \multicolumn{1}{c}{**Fiber Optics**} & \multicolumn{1}{c}{**Fiber Optics**} & \multicolumn{1}{c}{**Fiber Optics as**} & \multicolumn{1}{c}{**Fiber Optics**} & \multicolumn{1}{c}{**Key Performance**} \\ \multicolumn{1}{c}{**Evaluated**} & \multicolumn{1}{c}{**behind Casing**} & \multicolumn{1}{c}{**on Tubing**} & \multicolumn{1}{c}{**Wireline**} & \multicolumn{1}{c}{**Linear**} & \multicolumn{1}{c}{**Index**} \\ \hline \multirow{5}{*}{**Fiber Optics**} & Low Frequency/Pulse & Good Data & Moderate & Moderate to & Moderate Data & \multirow{2}{*}{\
\begin{tabular}{c} **Key Performance** \\ **Linear** \\ \end{tabular} } & \multirow{2}{*}{LF = 10 Hz} \\  & Rate/Pulse Length & Quality & Data Quality & & & \\ \cline{2-7}  & High frequency/Spectral & & Moderate & Moderate to & & \\  & Resolution/Gauge & Quality & Data Quality & Poor Data & & \\  & Length & & & Quality & & \\ \cline{2-7}  & Dynamic & Good Data & Moderate & Moderate to & & \\  & Range/Resolution & Quality & Data Quality & & & \\ \cline{2-7}  &
\begin{tabular}{c} VSP/Azimuthal (3D) \\ Acquisition/Directivity \\ \end{tabular} & Good Data & Moderate & Moderate to & & & \\  & Quality & Data Quality & & & \\ \cline{2-7}  & Signal-to-Noise/Time & Good Data & Moderate & & & \\  & Gated Digitizer & Quality & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Quality conformance of fiber optic sensing demonstrates the field deployment advantages and disadvantages in data quality, sensitivity, and accuracy. Optimum data quality acquisition for reservoir monitoring is to place fiber optic cable behind casing and cable on tubing. Cable deployment with inflatable liner is not suitable for deep well deployment.  
**Author Contributions:** Conceptualization, M.H.M.Z. and A.R.G.; methodology, M.H.M.Z.; formal analysis, M.H.M.Z.; investigation, M.H.M.Z. and K.M.A.A.; data curation, M.H.M.Z. and K.M.A.A.; writing--original draft preparation, M.H.M.Z.; writing--review and editing, M.H.M.Z. and A.H.A.L.; supervision, A.R.G. and A.H.A.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** Universiti Teknologi Petronas: 015 MD0-076.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors would like to thank the management of PETRONAS, PETRONAS Research and UTP for allowing us to pursue and publish this work through 015 MD0-076. The authors would also like to thank Neubrex Co., Ltd. (Kobe, Japan) and CMC Research Institutes who contributed to the field trial.  
**Conflicts of Interest:** The authors declare no conflict of interest.