Solid organic deposition during gas injection studies

Recently a series of first contact miscibility (swelling) experiments have been performed on undersaturated light and heavy oils using LPG rich and me thane rich injection gases, in which solid organic deposition was observed. A compositional gradient in the oils during the gas injection process was also evident as oil fractions expelled from the top to bottom of the PVT ce ll were observed to vary in density, molecular weight, as well as darkness of color. The change in stability of the oil samples before and after the c ontact with gas was analyzed using flocculation threshold titration. The as phaltene content of the different oil samples were determined by the TP 143 method. The standard asphaltenes and the solid organic deposit recovered f rom the swelling tests were analyzed using FTIR, HPLC-SEC and H-1 NMR. The aim of these analyses is to reveal the molecular nature of the deposits for med during the gas injection process in comparison with the standard asphal tenes in order to understand the mechanisms involved in asphaltene depositi on.