New Strategy for Selection of Best Water Chemistry of Injected Fluid During Water Flooding to Mitigate Scaling Problem

In this study, we have implemented an effective and novel strategy for determining the potential of scale formation and reservoir minerals reactivity caused by the mixture of injected water and formation water during water injection in the carbonate hydrocarbon reservoir of the Kazakhstan oil field. Transport modeling was performed using PHREEQC geochemical software to predict the scale formation tendency and the reactivity of formation minerals with the mixture of injected and formation water during flooding. The formation minerals precipitation/dissolution was then used to derive the changes encountered in the porosity and permeability of the reservoir across the grid cell. To improve the injectivity, the injected water chemistry was modified by diluting it two and four times and removing H₂S and Fe contents from the injected water as an optimization technique. The results revealed that during injection of original water in the reservoir, in the presence of formation water, was found to be supersaturated with pyrite, hematite, mackinawite, FeS precipitates (ppt) and goethite scales. The outcomes also suggest that the removal of Fe from injected water proved to be the most reliable solution in terms of controlling the scale precipitation problem completely as well as the highest enhancement of porosity (value from 7 to 12) and permeability (an increase of 1.5 times) of the reservoir. The second best option is the H₂S removal. H₂S removal is important because it controls sulfide scales with simultaneous improvement in porosity and permeability but also assists in corrosion control management.