The Role of Asphaltene in Wettability Reversal .

Abstract

SPE Members Abstract Wettability is an important factor in a number of petroleum production processes. Asphaltene deposition can have a strong role production processes. Asphaltene deposition can have a strong role in wettability reversal. Among many factors, the high molecular with, polar fraction of crude oils, including the asphaltenes, are considered to be the primary wettability altering agents. Understanding the role of asphaltene in wettability of reservoir fluids on solid surfaces and its reversal will help us plan for more efficient oil recovery processes. It will also establish the role of asphaltene deposition in the production operation of asphaltic crudes including heavy petroleum crudes. In this paper the groundwork for the study of the complex role of asphaltene and its deposition in altering the wettability of reservoir fluids on solid surfaces is presented. A number of experimental observations in support of the strong role of asphaltene in altering the interfacial tensions and wettability is reported. A new molecular theory for prediction of wettability and its reversal is also prediction of wettability and its reversal is also introduced. Introduction and Background It is well recognized that the presence of asphaltene in a crude oil can add significantly to the problems in a petroleum production field. Properties problems in a petroleum production field. Properties of the asphaltene containing residue of an oil are found not to be consistent with the properties of the lighter oil fractions. The compounds which constitute complex petroleum crudes are mutually soluble so long as a certain ratio of each kind of molecule is maintained in the oil mixture; They are the ratio of polar to nonpolar molecules and the ratio of high to polar to nonpolar molecules and the ratio of high to low molecular weight molecules in the mixture. The necessary mathematical models for the prediction of the onsets and amounts of deposition of asphaltene due to changes in flow conditions, temperature, pressure, and concentrations is already formulated pressure, and concentrations is already formulated The principles of thermodynamics of multicomponent mixtures and phase equilibria, the theory of continuous mixtures, the statistical theory of polymer solution, the concept of streaming potential, and the theory of FRACTAL aggregation kinetics are utilized to develop these models. Asphaltene deposition. is considered to be a major cause of wettability reversal inside an oil reservoir. Wettability is defined as "the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids. Wettability has been recognized as an important factor in a number of oil-recovery-related processes such as waterflood behavior, capillary pressure, and relative permeability. According to the literature the exact permeability. According to the literature the exact mechanism of wettability is not satisfactorily understood. Furthermore, the determination of insitu wettability and application of laboratory results to field conditions are known to be unreliable. It is also known that wetting states of reservoir rocks are inherently difficult to ascertain. Whether the majority of reservoirs are water wet, oil wet, or of intermediate wettability seems still very much a matter of debate and research. P. 799