The Effect of Inhibitors Asphaltene Precipitation Due to a Natural Depletion Mechanism in Crude Oil

Abstract

Asphaltene precipitation in oil reservoirs can cause severe problems that are expensive and difficult to remediate. Application of inhibitors as an effective method to remedy this problem is reviewed. Most of the reported experimental works examine the role of chemical inhibitors on asphaltene precipitation at atmospheric conditions and a some studies are performed at reservoir conditions. In this work, the performance of five inhibitors on asphaltene precipitation for an Iranian crude oil sample at atmospheric condition was investigated and one sample with the highest efficiency was used for conducting the experiments at reservoir conditions. Pressure depletion tests are carried out in the absence and presence of the selected inhibitor at two temperature levels using high pressure and high temperature PVT cells. Atmospheric tests showed that salicylic acid is the most efficient inhibitor and a concentration of 200 ppm was selected due to constant inhibition efficiency beyond this concentration. Experiments at reservoir conditions revealed that 200 ppm salicylic acid leads to a decrease in asphaltene precipitation of about 30% on average. The surprising result is that at 190.4°F the inhibition efficiency decreases when the pressure increases, while at 241.7°F it increases (with raising the pressure) below the bubble point, and decreases above the bubble point. The results of this work can be helpful for a successful design of network production for petroleum reservoirs.