Petrophysics analysis of unconventional reservoirs in Miocene interval, Area “ENC”

Indonesia continues to experience a decline in oil and gas reserves, with oil reserves dropping from 7.25 MMSTB in 2016 to 4.17 MMSTB in 2022 and natural gas reserves falling from 144.06 TSCF to 54.83 TSCF (KESDM, 2022). In the midst of the depletion of national oil and gas reserves, unconventional hydrocarbon reserves show very promising amounts of reserves. The basin of interest area contributes 2% of national natural gas production and 5% of national oil production. A study of what parameters are suitable for unconventional oil and gas research in the offshore Indonesia basin, Area ENC especially in Miocene interval is needed. The parameters studied include shale volume, porosity, Total Organic Carbon (TOC), and Brittleness Index (BI), that’s analyzed in 6 wells of the interval. Facies analysis shows that in the study area there are six facies, namely shale, shale-interbedded siltstone, siltstone, siltstone-interbedded sandstone, sandstone, and coal. Some shale facies and tight sandstone in study area are meet the requirement as unconventional reservoirs. The petrophysical characteristics of the shale hydrocarbon reservoir interval are as follows: the average shale volume is 0.73 (the highest is Dahlia well: 0.87); the PHIE is 4.4% (the highest is Edelweiss well: 6.2%); the TOC is 2.57 (the highest is Dahlia well: 3.02); and the BI is 0.64 (the highest is Akasia well: 0.68). The petrophysical properties of the tight sand hydrocarbon reservoir interval are as follows: the average shale volume is 0.25 (the lowest is Edelweiss well: 0.24); the PHIE is 8.2% (the highest is Edelweiss well: 8.8%); and the BI is 0.72 (the highest is Edelweiss well: 0.84). Based on the analysis that has been carried out, it is concluded that Miocene interval in ENC area, are potential to be developed as unconventional hydrocarbon reservoirs.