## 5 Analysis of HFT Results
### Stimulated Reservoir Volume (SRV)  
We have calculated the difference between the above T-dir and L-dir HFs induced stimulated reservoir volume (SRV) for each \"Well Pattern\" model. The concept of SRV provides a link between well productivity, the observed distribution of microseismic events, and HF networks that are created. The SRV dimensions are affected by both reservoir geomechanical properties and hydraulic fracturing parameters [32]. In this study, using the \"Kinetix Stimulation\" simulator, as shown in Figure 11, the SRV is calculated by creating unstructured grids centered on the HFs and summing the volume of the grids at a certain distance from the HFs [33]. The unstructured gridding created a Voronoi (PEBI; perpendicular bisection) grid which can conform to complex HF geometries generated by UFM [34]. The fracture cell width was upscaled to 3.28 ft. The minimum zone height was 10 ft and layers smaller than 10 ft were merged. As shown in Figure 12a,b and Table 5, the total SRV result of the proposed case, which was designed by considering the in-situ principal stress, was 99,926,737 m\({}^{3}\), which was 16.4% higher than the actual case (116,291,809 m\({}^{3}\)). This is due to the L-dir HFs, which were very closely spaced, formed in SANDY03 and ROADRUNNER 1H of the actual model drilled toward \(\sigma_{\text{Hmin}}\)-dir. Additionally, it is because the fractures created almost parallel to the horizontal well were limited to a narrow range close to the wellbore, so that the contact area to the reservoir could not be formed widely. Figure 13 shows the monthly oil production and cumulative oil production of SANDY03 from 2012 to 2019. The monthly oil production for the 1 st year indicates that it decreased to 16.2%, from the initial 1848 m\({}^{3}\) to 300 m\({}^{3}\). In addition, the cumulative production is only 2.7% (8777.2 m\({}^{3}\)) of the calculated OOIP. If the T-dir HFs were formed in SANDY03 and the SRV was 16.4% higher, it is expected that 1437.7 m\({}^{3}\) of oil can be additionally produced when the oil recovery of 2.7% is incorporated.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & **Stage** & **1-2** & **2-3** & **3-4** & **4-5** & **5-6** & **6-7** & **7-8** & **8-9** & **9-10** & **Avg** \\ \hline \multirow{3}{*}{SANDY 03} & Designed Interval (m) & 76.5 & 135.6 & 140.2 & 152.4 & 91.4 & 138.7 & 126.5 & 213.4 & 111.3 & 131.7 \\ \cline{2-10}  & Distance b/w HFs (m) & 19.8 & 35.1 & 36.3 & 39.3 & 23.8 & 36.0 & 32.6 & 55.2 & 28.7 & 34.1 \\ \cline{2-10}  & Stress Shadow (MPa) & 6.4 & 1.0 & 1.1 & 0.9 & 3.0 & 0.8 & 1.3 & & 1.7 & \\ \hline \multirow{3}{*}{ROAD RUNNER 1H} & Designed Interval (m) & 241.7 & 219.5 & 143.3 & 192.0 & 173.7 & 138.7 & & & 184.7 \\ \cline{2-10}  & Distance b/w HFs (m) & 62.5 & 56.7 & 37.2 & 49.7 & 45.1 & 36.0 & & & 47.9 \\ \cline{1-1} \cline{2-10}  & Stress Shadow (MPa) & & & 1.3 & 0.3 & 0.6 & 2.7 & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Stress shadow occurred by L-dir fractures of horizontal wells drilled toward \(\sigma_{\text{Hmax}}\)-dir.  
Figure 10: Stage #2 fracture affected by stress shadow due to stage #1 fracture.  
Figure 11: Concept diagram of unstructured gridding for stimulated reservoir volume (SRV) calculation [33].  
Figure 12: SRV of (**a**) “Actual Well Pattern” case and (**b**) “Proposed Well Pattern” case.