Publications

The Miocene-carbonate reservoir in Soka Field is located in the Musi Platform of South Sumatera, Indonesia. Soka is one of producing fields in Medco Energi and Carbonate – Baturaja formation is the main formation play in Musi Platform. Soka itself is a four-way dip closure trap combined with stratigraphic trap in the North toward basement high. Carbonate mound was deposited in shallow marine, inner to outer shelf area where sea level rose and compaction triggered the diagenetic process that resulting in heterogeneity carbonate reservoir in this area.

Lithofacies evaluation of Baturaja in Soka field has been analyzed by utilizing image log and integrating well data such as logs, conventional core, petrography, and isotope analysis as the basis of analysis. From 5 wells used in this analysis, there are total 4 conventional cores, 4 image-log data, 10 thin sections, and 49 samples of isotope as well as conventional log suite have used during the evaluation.

Variations in texture, structures, organism, mineral content, shale properties, and pore geometrical attributes define the existence of distinct lithofacies unit which could give the picture of its fluid-flow characteristics in carbonate reservoirs.

The result of analysis indicates that Baturaja limestone in Musi block consist of 7 lithofacies, LF#1 Bedded to laminated Wackstone-Packstone, LF#2 Skeletal Packstone-Grainstone, LF#3 Mottled Wackstone, LF#4 Microcrystaline wackstone, LF#5 Mudstone. LF#6 Rubble bed (breccia-conglomerate), and LF#7 Bedded Limestone. Lithofacies #7 doesn’t have conventional core to be calibrated, but just based on image logs and conventional well data.

Characterization of the Baturaja Formation in Soka field gives better lithofacies predictions, leading to an enhanced image-based reservoir characterization supported by core and wireline log calibration. This can have potential benefits both in daily operations and in reservoir simulation models. Each lithofacies exhibits a clustered range of porosity and permeability values, which together define a continuous porosity-permeability trend Furthermore, Image-based lithofacies characterization can be used in field application and can improve reservoir descriptions in complex carbonate reservoirs.

However, there is a limitation in the rock characterization and distribution to the whole structure, due to the low resolution of 3D-seismic that up to 67 ft of tuning thickness. Hence, the study is not reaching technical limit yet and still have an opportunity to be re-modelled in the future if there is a chance to run a new 3D-seismic acquisition.