Effect of Water Flooding on Oil Reservoir Permeability: Saturation Index Prediction Model for Giant Oil Reservoirs, Southern Iraq

This research was conducted on five oilfields in the Mishrif reservoir, southern Iraq, to illustrate the effects of permeability on the damage caused by the injection of river water into the oilfield. Oilfield flooding has dramatically changed the pH and brine chemistry of the reservoir and resulted in the deposition of carbonates and native sulfur. The air permeability test and scanning electron microscope (SEM) analysis revealed how the precipitated minerals and materials (e.g., residual heavy oil, asphaltene, wax, native sulfur and authigenic and diagenetic clay minerals) reduced the permeability by lining the pore necks. The PHREEQC software and saturation index (SI) model revealed several types of pore-lining scales formed in a porous matrix. The SI model indicates that barite, celestite, calcite and pyrite are common scales lining the pore spaces, which precipitated in response to the injection of sulfate- and carbonate-rich river water into an oil well. This research generated useful findings that can be taken into consideration for future oil production worldwide. Additionally, the permeability values were used as evidence for discrimination of sedimentary environment, particularly reef and non-reef facies.