Asphaltene Remedial Technology Using Advanced Deasphalted Oil

Abstract

Abstract It is well recognised among the scientific community that resin molecules play a crucial role in the stability of colloidal asphaltene particles in petroleum oils. The de-stabilization of asphaltene/resin interaction under the influence of any change in the thermodynamic parameters can cause asphaltene to precipitate. This may significantly add to petroleum field problems such as in-situ permeability reduction, as well as by contributing to serious plugging problems in the production facilities. The latter is the case in West Kuwait Marrat deep wells. One of the remedial technologies that is used in the oil industry is to increase the concentration of the resins' chemical potential by developing synthetic resins to enhance the stability of asphaltene in the oil phase. This method sometimes can be ineffective due to the difficulty in predicting the resin chemical structure that is compatible with the asphaltene chemical structure. The objective of this paper is to introduce a method that is capable of increasing the concentration of resins in their natural state, including increasing oil's aromatic power solvency. The latter is an excellent solvent for well cleaning. The stability of asphaltene was investigated using three different types of de-asphalted oils (DAO) derived from West Kuwait Marrat oil. The first DAO had only the asphaltene fraction removed; the second had the fractions of C5 to C9 removed, and asphaltene; the third had C5 to C15 fractions and asphaltene removed. The oil fractions were removed by a distillation process and asphaltene precipitated by n-pentane. The results have shown that the resin concentration in Marrat oil was increased in volume by removing more oil fractions. It was observed that asphaltene stabilization is strongly influenced by the resin concentration. The influence of the aromatic power solvency has also been examined on asphaltene particles disaggregation, and it was found that disaggregation kinetic rates increase with increasing the aromatic concentration in DAO. No formation damage was observed by all DAO products during core flooding tests. Introduction The numerous problems associated with asphaltene deposition generate large costs to the petroleum industry worldwide. The asphaltene phenomenon seriously reduces well productivity, plugging well tubing and flow lines. The main objective for the oil producers is to minimize asphaltene precipitation to avoid any extra cost to the production operation1–3. Petroleum oils were found to be colloidal solutions in which asphaltenes were the dispersed colloids4. The colloidal nature of petroleum oil was first recognized by Nellesteyn5,6, who proposed that petroleum oil contains three principal fractions: oils as dispersed phase, resins as protective bodies and asphaltenes as dispersed colloids. The precipitation of asphaltenes depends on the colloidal stability of these complex systems. The stability of a colloid dispersion is defined as its resistance to flocculation or coagulation. The degree of the "resistance" is used as a measure of the dispersion stability. Asphaltene colloidal dispersion in petroleum reservoirs is considered physically stable if free from any changes in physical properties. However, the degree of asphaltene stability mainly depends on the chemical potential of the resin concentration in the oil phase, thus promoting what is called a steric effect to prevent asphaltene particles from aggregation7–11. The stability of asphaltene has been studied systematically by using a variety of asphaltene stabilizers, i.e. an amphiphile12–15. The asphaltene stabilizer or inhibitor is supposed to act in a similar way to the natural state of resins by peptizing asphaltene particles and keeping them in solution. This type of chemical process depends on the interactions between asphaltene and resin molecules, which is difficult to investigate due to their structural complexity. The performance of this method has its limitations due to the differences of asphatene chemical structure from reservoir to reservoir.