Impact of crude oil properties on stability of HCl-crude oil emulsion using XDLVO theory

Undesired emulsification of HCl-crude oils during acid jobs may compromise oil production due to clogging of near wellbore region. This may be resulted from the presence of natural surfactants such as asphaltene. In this paper, the relation between some of crude oil properties including API gravity, dynamic viscosity, polarity, total base number (TBN) with the emulsion stability has been studied by applying the XDLVO theory. The results showed that TBN, and polarity of the crude oil medium can be manifested as reliable criteria for predicting the emulsion stability, while the impact of API gravity and dynamic viscosity of the crude oil were marginal. Sensitivity analyses were also carried out to discern the most dominant parameters on the total interaction energy between droplets in the HCl-crude oil emulsions. It was found that in short distances between droplets, the effect of electron acceptor/donor components are important in such a way that a crude oil with high electron donor and low electron acceptor components would form more stable emulsion when it is mixed with the HCl solution, while no noticeable effect was observed for longer distances. In addition, the results of adhesion tests showed that the presence of HCl solution increases the adhesion of different crude oils onto a glass surface. This is imperative for evaluating the extent of formation damage due to acid-crude oil emulsion and acid sludge formation, when they stick to the rock surfaces. These findings can serve as guideline for choosing the appropriate acid stimulation job in connection with crude oil properties for management of formation damage.