Digital rock analysis of the transition zone in the minagish formation, Kuwait

We present the results of a comprehensive multiscale imaging and simulation projecton core plugs from the Minagish formation in South East Kuwait. The objective of the study was to calculate petrophysical and two-phase flow properties of core plugs representative of well BG-0836. The well contains multiple rock types ranging from packstone to coarse grainstone and includes an oil-water transition zone. Nine plugs were selected to represent the different rock types and wettability conditions encountered in the well. A digital rock analysis (DRA) program was established to characterize the plugs by combining experiments, imaging, modeling, and simulations. The plugs were imaged at multiple scales by X-ray micro Computed Tomography (microCT), Scanning Electron Microscopy (SEM) and SEM-Energy Dispersive X-ray Spectroscopy (SEM-EDS) to allow a detailed characterization of the pore space and the construction of representative rock models. The rock models were used to calculate the petrophysical properties of the core plugs including porosity, permeability, formation factor and the cementation exponent (m). The simulation of two-phase flow properties requires plausible pore-scale wettability distribution input. This is particularly important in the transition zone where the samples can range from oil-wet to water-wet. Consequently, to increase the reliability of the results, the DRA workflow was complemented by an advanced 3D pore-scale imaging workflow in which the fluid distributions in the samples were imaged by micro CT after experimental water saturation, primary drainage, spontaneous and forced imbibitions. The 3D images obtained at different saturation states were used to quantify the wettability and guide the two-phase flow simulations. Oil/water capillary pressure and relative permeability curves for primary drainage and water imbibition as well as the saturation end-points were generated.