Factors contributing to petroleum foaming. 1. Crude oil systems

Gas/oil separation can often be accompanied by unwanted foaming. To study this phenomenon, 20 crude oils were subjected to low-pressure foaming experiments. Eleven of the crudes were from offshore platforms where foaming occurs regularly. Two foaming parameters, foam volume (or foamability) and collapse slope (i.e. the rate of foam collapse in the absence of sparge gas), were compared with several crude oil properties, namely, density, bulk viscosity, surface tension, asphaltene and resin content, asphaltene and resin molecular weight, and asphaltene and resin heteroatom content. For asphaltenic crudes, collapse slope was found to correlate with asphaltene content as well as several other crude oil properties: density, viscosity, and surface tension. Foam volume did not relate to any asphaltenic crude oil property, However, for crudes having little to no asphaltenes, foam volume, not collapse slope, strongly related to crude oil surface tension. For low asphaltenic crudes, results further indicate that resin chemical composition plays a key role in determining foam volume and that larger foam volumes were associated with higher crude densities and viscosities. Finally, viscosity was found to play a major role in determining whether a crude oil will foam under the experimental conditions.