## 4 Results and Discussions  
### Loss Circulation Depth, Thin Sections and Core Description Analysis  
Final well reports of Jintan-1, Jintan-2, Jintan-3, and M1-1 wells were studied to preliminary identify possible karst intervals and their corresponding depths. Jintan-3 well experienced lost circulation at 1869 m and was prematurely terminated to avoid further losses after it has experienced a minor loss at a rate of approximately 300 bbl/min. The depth at which the loss occurred was recorded as a marker in Jintan-3 well for well to seismic correlation. The result showed that the lost circulation depth marker falls on the prominent dendritic features (Figure 10). Hence, it is important to avoid dendritic features on seismics. It is best to have possible karst features analysis/interpretations activity before the well development planning to avoid drilling issues which are also part of the time and cost optimization strategy. Quantitative analysis on thin sections revealed that vuggy and moldic porosity in both wells are 25% of total pore types in Jintan-2 and 29% of total pore types in Jintan-3. Vugs of 2-4 mm in size with 1-2 mm moldic pore size and blocky calcite precipitates on the interior of fossils/molds were observed, which indicated the apparent rapidity of the dissolution process occurring in mixing zone. [PERSON] [26] in her petrographic analysis on mixing zone diagenesis in the subsurface of Florida and the Bahamas revealed a petrographic fabric of moldic porosity and blocky to dogtooth calcite cementation which are similarly observed on Jintan-2 (Figure 11) and Jintan-3 (Figure 12) wells. Core description analysis on Jintan-2 and Jintan-3 wells revealed up to 10 m of chalkified and rubble interval as well as \(\geq\)0.5-1 cm large vugs and moldic porosity observed which confirmed the existence of a dissolution karstification process on the platforms (Figure 13). Figure 10: (**a**) The lost circulation depth marked at Jintan-3 well falls on the chaotic seismic facies which revealed the approximate height of the cavern karst geobodies are 70–100 m. Horizon marked in red is the interpreted horizon exactly on the losses depth. (**b**) Time slice of the interpreted horizon show that the loss depth marked in pink falls within the prominent 1–3 km long dendritic features. Figure 11: (**a**) Vug size of 4 mm observed on thin section in Jintan-2 well at 1649.6 m depth. (**b**) Moldic porosity of coral growth framework pore type observed on thin section in Jintan-2 well at 1680.8 m depth. Figure 12: (**a**) More than 2 mm wide moldic porosity resulting from the dissolution of red algae and filled with blocky calcite cements (yellow arrow) are observed in a thin section at Jintan-3 well (1778.38 m depth). (**b**) More than 10 bioclasts dissolved and some of the pore filled with blocky calcite cements (yellow arrow) observed on thin section at Jintan-3 well at 1829.05 m depth. Figure 13: (**a**) Chalkified intervals observed in Jintan-2 well between 1662.97–1664.6 m depth (**b**) Rubble core observed in Jintan-3 well at 1792.4–1791 m depth (**c**) \(\geq\)0.5–1 cm large vugs and moldic porosity observed in Jintan-3 well at 1672.5 m depth. Spectral Decomposition Short-Time Fourier Transform (STFT), Continuous Wavelet Transform (CWT) Morlet, and CWT Ricker Methods  
Three methods of spectral decomposition have been applied on the Jintan and M1 3D seismic cube (Figure 14). The STFT method utilized frequencies of 46, 54, and 60 Hz, CWT Morlet wavelet with frequencies of 63, 65 and 67 Hz and CWT Ricker wavelet with frequencies of 49, 56, and 66 Hz. Analysis showed that the STFT method delineated more prominent karst on the Jintan platform as highlighted in yellow (Figure 14a). CWT Morlet wavelets delineated most karst features on the M1 platform particularly closer to the reef rim area (Figure 14b). Meanwhile, the CWT Ricker wavelet method delineated fewer karst features compared to the other two methods (Figure 14c).