An Experimental Investigation of Different Formation Waters and Injection Water Incompatibility to Obtain the Optimum Water Mixing Ratio in Injection Processes

Scale formation and well plugging due to the incompatibility of injected waters is a critical field problem in oil recovery. A water injection process was successfully performed when the identification of the source of water, water quality considerations, and laboratory compatibility tests were considered. When different waters are mixed, it is necessary to evaluate their compatibility prior to the injection into oil wells. Jar test is conventionally performed in the laboratory to estimate formation damage by scale formation in the wellbore and facility. The individual waters may be quite stable under all system conditions and present no scale problems. However, once they are mixed, the reaction between ions dissolved in the individual waters may form insoluble products that cause permeability damage in the vicinity of the wellbore. The obtained results from the jar test for different mixtures of waters can be used to know the type of scale in the reservoir. This work was undertaken to experimentally identify the composition of mineral scales that occur in a raw water and different volume mixings. The formation of CaSO4, SrSO4, and CaCO3 during the sampling of production waters, including different reservoir layers and mixing of their different volumes with K sample have been proved by scanning electron microscopy micrographs and X-ray diffraction. The results of jar tests for the mixing of different waters indicated that the main constituents of the scale were strontium sulfate and calcium carbonate. The results showed that mixing ratio of 75 to 25% of K water to different produced waters were the most suitable ones.