Dissolved Gas Analysis in Mineral Oil and Natural Ester Liquids from Thermal Faults

This work addresses the gas formation mechanisms for paraffinic-type mineral oil and soybean-based natural ester with a predominantly linoleic fatty acid under thermal faults. Based on a literature review, possible decomposition paths due to pyrolysis are proposed. A case study of hot spots of different temperatures is presented and its results are compared and analyzed with the gas profiles of the IEEE C57.155-2014 guide. The results obtained for both cases are consistent with the proposed mechanisms. For the same thermal fault, the gas profiles are different. The natural ester presents significant proportions of ethane and carbon dioxide concerning mineral oil. For temperature faults above 700 degrees C, the behavior of the chemical structures of the natural ester is similar to the carbon structures of the mineral oil and is subject to similar reactions. Therefore, the major differences in the gases generated for thermal faults are at low temperatures.