Journal of Petroleum Exploration and Production Technology (Mar 2019)
A comparative study of density estimation of asphaltene structures using group contribution methods and molecular dynamic simulations for an Australian oil field
Abstract
Abstract One of the major challenges faced by oil extraction industry is the unstable behavior of asphaltene formation, yet not fully understood. The prediction of asphaltene formation depends on the small changes in chemical characteristics and composition of the crude oil. Consequently, the study of molecular structure and molecular properties such as density is of a great practical interest. Other properties become very complex to assess when the asphaltene fraction contains 105 different molecules. Average molecular parameters are used to obtain information about asphaltenes. The density of the asphaltenes can easily be calculated and, thus, can be used to evaluate predictive capacities of the average structure. This present work of molecular dynamic simulations was carried out to evaluate the asphaltene densities of an Australian oil field. Simulations of molecular dynamics are used to assess the average structure densities representing different asphaltenes in a specific oil field. These simulations assist in predicting the formation of asphaltene structural model. Comparatively, the experimental densities are higher than the calculated ones. However, the calculated values demonstrate the appropriate trend. The chemical structure shows essential accuracy, as evidenced by average structures, which can be used to estimate the densities qualitatively. Hence, systematic study was carried out on the basis of the effects of various structures on the calculated densities of asphaltene. The main characteristics of the molecules which yielded highest densities are those found with low hydrogen–carbon ratio and big condensed aromatic rings. Moreover, better and improved density values were produced by a recently developed group contribution method than simulations of molecular dynamics, which is still being lower than that of experimental values.
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