## 4 Hydrocarbon Potential of formations in Malaysia
### Organic Geochemical Characteristics of Rock Formations in Sabah Region
#### 4.2.2 Source Quality  
The average OI values of the Sandakan, Temburong, Pinangah, Beliat, Melian, West Crocker, and Setap formations ranged from 3.6 to 88.50, while the HI values ranged from 35.19 to 392.5 (Table 9). The Ganduman, Sebahat, Tanjong, Kapilit and Kalabakan formations had HI ranging from 24.69 to 261.78 and Tmax ranging from 372 to 492.7 \({}^{\circ}\)C (Table 10). The OI and HI plots indicated that almost all the formations were of type III kerogen, except for the Pinangah and Tanjong formations, which were type 1. This suggested that only the Pinangah and Tanjong formations would generate oil, but the rest would generate gas (Figure 10). The Tmax vs. HI plots also indicated that the Tanjong and Kalabakan formations were Type I, and the Kapilit formation was Type III, with the Ganduman and Sebahat formations being Type IV (Figure 11). However, since type IV kerogen is inert and only minimally contributes to the S2 but significantly contributes to the TOC, this lowered  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No.** & **Formation** & **Avg TOC (wt\%)** & **Interpretation after [PERSON] [79]** & **Reference(s)** \\ \hline
**1** & Ganduman & 15.75 & Very good & [58] \\ \hline
**2** & Sebahat & 6.51 & Very good & [58] \\ \hline
**3** & Tanjong & 52.80 & Very good & [55; 59; 60] \\ \hline
**4** & Sandakan & 19.27 & Very good & [61] \\ \hline
**5** & Temburong & 0.53 & Fair & [15; 62] \\ \hline
**6** & Beliat & 1.64 & Good & [15; 64] \\ \hline
**7** & Pinangah & 68.05 & Very good & [90] \\ \hline
**8** & Melian & 1.99 & Good & [15] \\ \hline
**9** & West Crocker & 3.19 & Very good & [15] \\ \hline
**10** & Setap & 0.84 & Fair & [64] \\ \hline
**11** & Kapilit & 39.94 & Very good & [60; 65] \\ \hline
**12** & Kalabakan & 1.03 & Good & [60] \\ \hline \hline \end{tabular}
\end{table}
Table 8: Interpretation of average TOC values of formations in Sabah according to [PERSON] [79].  
the HI, making the source rock appear more gas-prone [17]. The Pinangah and Tanjong formations were type I kerogen, originating from algal material accumulated in lacustrine environments and producing waxy oil [17]. So, the other formations in the Sabah region, except Pinangah and Tanjong, originated from terrestrial plant debris or aquatic organic matter accumulated in an oxidizing environment that generated mainly gas [72].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No.** & **Formation** & **Avg Tmax** (\({}^{\circ}\)**C**) & **Avg HI** & **References** \\ \hline
**1** & Ganduman & 372.00 & 60.75 & [58] \\ \hline
**2** & Sebahat & 405.44 & 24.69 & [58] \\ \hline
**3** & Tanjong & 458.33 & 250.08 & [60] \\ \hline
**4** & Kapilit & 434.06 & 261.78 & [60,65] \\ \hline
**5** & Kalabakan & 492.70 & 39.60 & [60] \\ \hline \hline \end{tabular}
\end{table}
Table 10: Average Tmax and HI values of formations in Sabah.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Formation** & **Avg OI** & **Avg HI** & **Reference(s)** \\ \hline
**1** & Sandakan & 47.48 & 76.74 & [61] \\ \hline
**2** & Temburong & 17.94 & 35.19 & [15,62] \\ \hline
**3** & Pinangah & 3.60 & 392.50 & [63] \\ \hline
**4** & Beliat & 43.00 & 56.22 & [15,64] \\ \hline
**5** & Meligan & 19.40 & 36.60 & [15] \\ \hline
**6** & West Crocker & 21.20 & 71.00 & [15] \\ \hline
**7** & Setap & 88.50 & 60.10 & [64] \\ \hline \hline \end{tabular}
\end{table}
Table 9: Average OI and HI values of formations in Sabah.  
Figure 9: A plot of average S2 versus average TOC of formations in Sabah showing hydrocarbon yield potential and kerogen type.