Precipitation of asphaltene is a serious and common challenge faced by the oil industry during production of heavy oil. Regular treatments are often required to reinstate lost productivity by removal of such deposits from tubing or within the reservoir.
Hydrocarbon-based solvents, like xylene or xylene mixtures, are the most commonly used recipes for dissolution of deposited asphaltenes. While such treatments are effective, they sometimes present problems with respect to health, safety, and environmental (HSE) characteristics (lower flash points and the presence of benzene, ethyl benzene, toluene, or xylene (BETX) components), which can limit their use. Recently, water/solvent emulsion systems that offer significant advantages compared to traditional recipes have been used. The solvents used in these emulsions have relatively higher flash points, making them a safer alternative. Further, the redeposition process is delayed because the treated surfaces are left in a water-wet condition.
This paper describes the application of such water/solvent emulsion systems used to treat asphaltene deposits from two distinct regions of the eastern hemisphere. The steps taken to optimize a recipe suitable for dissolution of the asphaltene deposits are highlighted. This is extremely important to the design of a successful treatment because the complexity of the deposits vary regionally. Higher solubility values were obtained with the emulsion system when compared to xylene. Importantly, these emulsion systems could also be designed with acid as an aqueous phase. This increases the solubility values significantly because acid-soluble inorganic minerals were also found in conjunction with asphaltene in the deposits studied. The data presented demonstrates the applicability of the emulsion system for effective removal of asphaltene deposits and recovery of lost productivity. This environmentally acceptable emulsion system can contribute significantly to profitable and sustained production of heavy oil when faced with asphaltene challenges.