Ionic Analysis and Photography of the Effect of Sulfate Ion in Different Ratios of Injection Water and Scale Formation and its Effect on Wettability Alteration in Carbonate Reservoirs

The most important challenges in water injection operation are mineral precipitation and inorganic scale formation .The formation of mineral scales in the pore throats of the reservoir rock results in reduction of permeability, porosity and production rate from the reservoir. One of the methods to solve this problem is to change the ions concentraion in the injected water. In smart water injection, the type and concentration of ions is particular importance in increasing the production efficiency and the recovery factor. In this article, based on the ion analysis of formation water and injection water samples in one of the oil fields in southwest of Iran, water compatibility test and effect scale formation on wettability alteration were studied experimentally. Moreover, simulation and sensitivity analysis of effective ions on strontium sulfate and calcium sulfate deposits were done. In order to identify the type and morphology of scales, SEM image and EDX analysis were used.  The results of the  water compatibility experiments show that increases in Sulfate ion with 4000 ppm causes the weight of the precipitates increased from 400 mg/L to 1400mg/L that sulfate ion with a ratio of 80 percent of injection water and 20 percent of formation water has the greatest effect on the reservoir damage and formation of strontium sulfate and calcium sulfate deposits. In the static tests of mixed waters, due to more investigation of scales in different parts of the reservoir and also the novelty of this research, scales were also investigated in the presence of rock in different conditions, and the weight of precipitates was observed from 800 mg/L to 1800 mg/L which indicates the surface absorption of ions by the rock and creat calcium carbonate formation.