Development of a fuzzy saturation index for sulfate scale prediction

An innovative approach established upon the concepts of fuzzy numbers and their processing system was developed to address the risk of sulfate deposition due to seawater injection as an enhanced oil recovery option. Uncertain parameters such as solubility product constant and free sulfate concentration are considered as fuzzy numbers. Appropriate modeling steps were performed with these fuzzy numbers to suggest a fuzzy saturation index. As a case study, anhydrite scaling tendency due to injection of Persian Gulf water into a selected well from Parsi field, southwestern Iran, is investigated via the proposed fuzzy saturation index. The proposed fuzzy approach provides a strict mathematical environment in which vague conceptual phenomena in scale prediction problem can rigorously be studied. It is able to deliver the maximum possible saturation index value and the whole set of possible values for the problem solution, preparing a wider perspective for the oilfield operator over the scale problem and the corresponding suitable prevention action.