Partitioning of Porosity for Carbonate Reservoirs Using Differential Effective Medium Models

Carbonate reservoirs are extremely heterogeneous owing to its variation in primary and secondary porosity types that affect the elastic properties of the reservoir. The Differential Effective Medium modelling approach is applied to determine the elastic properties of rocks and porosity partitioning of carbonate reservoir located in the western offshore region, India. The modelling requires the input from sonic derived logs and experimental data from the core samples. The Scanning Electron Microscope images of cores from two different depths are analyzed by watershed algorithm and binary digitization method to quantify the type of pores into cracks, interparticle and stiff defined by their aspect-ratios. The sonic velocities were inverted using Sequential Least-Squares Programming (SLSQP) optimization technique for the entire depth range of the well log from X110.20 m to X611.90 m. The partitioning of porosity derived by the DEM technique provides the relative percentage of the porosity types with depth and varies between 2 and 28% for the carbonate reservoir. In the reservoir section, most of porosity is contributed from stiff and interparticle types while the cracks contribute less than 20% of the total porosity.