Experimental study on foamy oil behavior using a heavy oil‒methane system in the bulk phase

In this study, three types of constant composition expansion tests on foamy oil are conducted in a pressure/volume/temperature cell: (a) constant pressure depletion rate test, (b) constant volume withdraw rate test, and (c) step-by-step test. The experiments are conducted to investigate the effect of pressure depletion methods and depletion/withdraw rates on a heavy oil‒methane system in bulk phase. Pure methane is recombined into a typical Manatokan dead heavy oil sample to generate a live oil sample. Totally, nine experiments are undertaken including four experiments for the constant pressure depletion rate test, four experiments for the constant volume withdraw rate test, and one experiment for the step-by-step test. New foamy oil behavior, which is presented as relative volume changes of foamy oil over time, is researched in this study. The experimental results indicate that similar trends and phenomena are investigated for both constant pressure depletion rate test and constant volume withdraw rate test. For solution gas phase, the concentration of solution gas has a strong exponential relationship with time. In addition, the reaction rate constant k_SG which indicates the gas transfers rate from solution gas to dispersed gas, increases with the depletion/withdraw rate increases. For free gas phase, moles of the evolved free gas proportional to t^1/2, and the same relation is observed in step-by-step test. Furthermore, the pseudo-bubble point pressure decreases with the depletion/withdraw rate increases, and a new approach using the trendlines of the moles of free gas versus t^1/2 is developed to determine the time when the pseudo-bubble point pressure achieves.