Distinguishing Anhydrate and Gypsum Scale in Mixing Incompatible Surface and Ground Waters During Water Injection Process

Determination of the type of precipitated calcium sulfate in mixing two incompatible injection and formation waters was studied experimentally in this work at two temperatures of 26oC and 80oC. Here the SEM, EDX and XRD techniques have been used to inspect the temperature effects on the morphology, type, and size of the precipitated calcium sulfate crystals. The results of this work show that the precipitated scales at these temperatures are calcium sulfate dihydrate and the temperature influences the size of crystals dramatically. The crystallization mechanism is the next issue which has been studied in this work. Measuring the amount of precipitated scale in the mixing of the incompatible waters versus time depicts the scale formation controlling mechanisms. According to the obtained results in this work, three primary nucleations, crystal growth, and secondary nucleation control the calcium sulfate scale precipitation.