Hydrate plugging potential of original and modified crude oils

The hydrate plugging potential of four crude oils have been studied. The crude oils were modified in two ways, either by de-asphalting (by adding n-pentane) or by a pH 14 liquid-liquid extraction. The pH 14 extraction removes acidic compounds from the oil phase into the aqueous phase at pH 14, typically phenols and naphthenic acids. All of the crude oils, both original and modified, were characterized together with their water-in-oil emulsions. The main results showed that removing the acidic compounds at pH 14 destabilized the asphaltenes, leading to increased water-in-oil emulsion stability. De-asphalting the crude oils decreased the water-in-oil emulsion stability, except for one of the crude oils. Three of the original crude oils were tested in a flow loop pilot rig. The results showed that the loop tests favor the inhibiting capacity of crude oils with high water-in-oil emulsion stability, possible due to emulsion formation by inline pump in the loop. In a flow simulator (wheel) the original crude oils, the pH 14 washed crude oils and two of the de-asphalted crude oils were tested. The results showed that the wheel tests favor the inhibiting capacity of crude oils with high content of acidic surfactants (naphthenic acids, phenols). In the wheel, the flow conditions are milder than in the loop, with less mixing, and the propensity of the oils to form stable water-in-oil emulsions is much lower.