Asphaltenes are chemical aromatic compounds that may precipitate at certain thermodynamic conditions and fluid characteristics. Oil production and transportation operations can be affected by asphaltene precipitation/deposition through wettability alteration and blockage mechanisms. This undesirable behavior is found in many oil reservoirs across the world, resulting in significant capital / operating costs and environmental issues.
Asphaltene deposition takes place in oil reservoirs when asphaltene flocculates by pressure reduction. Deposition of asphaltenes onto the rock surface appears in the form of adsorption and mechanical entrapment. Different production schemes such as Enhanced Oil Recovery (EOR) and natural depletion might experience the asphaltene precipitation and deposition.
The challenge with asphaltene precipitation/deposition in flow assurance can be addressed in three strategies: (1) prevent it from happening; (2) reduce the extent of precipitation; and/or (3) dissolve deposited asphaltene. There are a variety of removal and inhibition techniques such as utilization of solvents and chemicals including toluene, xylene, and Dodecylbenzenesulfonic acid (DBSA). The modern technologies such as ultrasonic and microwave radiation can be employed to eliminate the formation damage created near the wellbore. Most of the past studies about asphaltene inhibition involve static tests within a narrow range of operating conditions, using homogeneous physical porous models.
Further understanding of asphaltene characteristics and precipitation/deposition/inhibition processes in reservoir rocks are vital for better design, implementation, and control of oil production operations.
This chapter will provide a detailed survey of the main aspects of asphaltenes in terms of characterization, thermodynamic behaviours, process modeling, and corresponding experimental phases. The past research and engineering activities in this area are critically reviewed such that pros and cons of recent developments in asphaltene precipitation and mitigation approaches are briefly discussed. The main practical and theoretical challenges for characterization and control of asphaltene precipitation occurrence are then addressed.