Abstract
In general, the South Sumatra Regional Stratigraphy of the Baturaja Limestone Formation facies is deposited on the Buildup Carbonate (Reef) and the Limestone Clastic Carbonate of the Baturaja Formation which grows as a buildup reef on the platform in the Basement High (Horst) underneath is the Lemat Formation volcanic deposits. Referring to the facies model in general, the Baturaja Limestone Formation, the depositional environment starts from Shelf Lagoon Open Circulation - Winnowed Edge Sand - Organic Buildup - Fore Slope - Deep Shelf Margin - Open Sea Shelf - Basin, meaning that carbonate is formed starting from pure organic Cabonate Buildup Reef without / a little sludge / mud to the Carbonate Basin where more muddy / mud is present, this condition causes clay minerals to also more and more mix with Terigenous Clastics (Quartz, feldpar). The complexity of the Baturaja Limestone Formation requires fracture barrier analysis associated with well stimulation planning in order to increase oil productivity with the appropriate method. Fracture barrier fracture analysis is an approach method to determine the depth interval that becomes a barrier in hydraulic fracturing by correlating the results of geomechanical analysis from well log data and mineralogical analysis from drill cuttings data, so that a commonly used well stimulation method can be selected, namely hydraulic fracturing, acidizing, and acid-fracturing.From the ternary diagram plot the XRD (bulk) analysis results show that the distribution of the main minerals (Quartz, Clay, Calcite) is more dominant in the ductile zone, hard to frac category. This shows that all the depth intervals in the OBF-01 and OBF-04 wells are more ductile, and are not recommended for hydraulic fracturing. From the XRD (bulk) analysis, Calcite mineral is more dominant, so for well stimulation work it is recommended to use acidizing or acid-fracturing.
Highlights
The South Sumatra Basin is one of four basins located on the back side of the Sumatra portion of the Indonesian Island Arc complex
It can be seen that the distribution of main minerals (Quartz, Clay, and Calcite) is more dominant in Zone 4 (Ductile, hard to frac category). This shows that all the depth intervals in the OBF-01 and OBF-04 wells are more ductile, so hydraulic fracturing is not recommended
The results of bulk XRD analysis of cutting samples from OBF-01 and OBF-04 wells in the Upper Baturaja Formation (UBR), show that Calcite is the most dominant mineral compared to Quartz and Clay
Summary
The South Sumatra Basin is one of four basins located on the back side of the Sumatra portion of the Indonesian Island Arc complex. It consists of several structural sub-basins with Tertiary sedimentary section lying unconformably on the eroded and faulted topography of Pre-Tertiary basement metamorphic and igneous rocks. Baturaja carbonate deposition within the study area began during the early Miocene at the onset of the marine transgression that followed the Eocene rifting phase. Throughout the area, the Baturaja carbonates appear to unconformably overlie the marine shales of the Pendopo Formation, the terrestrial deposits of the Talang Akar formation and the Pre-Tertiary age basement. The Pendopo Formation appears to transition directly into the basal carbonates of the Baturaja formation, making it difficult to define the transition between the formations
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