Abstract
Matrix acidizing is one of the most viable options for opening up the clogged tortuous passages in near wellbore region which would lead to improved crude oil production. Nonetheless, the incompatibility of stimulation and reservoir fluids may result in further formation damage i.e., acid sludge. Sludge formation is a highly complex process in which the role of crude oil components is not well understood. In this study, the effect of aromatic and paraffinic components of crude oil on acid sludge formation has experimentally been investigated. For doing so, synthetic oil was used to isolate the impact of individual components of crude oil. Furthermore, the influence of polarity of solvents including DMF, acetone, THF, dichloromethane and toluene was discerned as well as type and concentration of asphaltene and different ratios of acid to synthetic oil mixture. The results showed that a paraffinic synthetic oil would be more susceptible to sludge formation than the aromatic one. Increased polarity of solvents from 2.4 for toluene to 6.4 for DMF resulted in more sludge formation from 15 to 231% and 42-175% for the same synthetic oil but for two asphaltenes, respectively. Acid to mixture ratio (AMR) showed to have a considerable implication on sludge formation. Increasing asphaltene concentration from 5000 to 15,000 ppm caused the increment of 1-3% in sludge content. This implied that asphaltene concentration in the synthetic oil had no considerable effect on the acid sludge formation in the absence of the other constituents of crude oil such as resin.
NSTL