Deasphalted Oil: A Natural Asphaltene Solvent

Abstract

Summary Asphaltene deposition in the near-wellbore region can block pore throats, change wettability characteristics and relative-permeability relationships, and therefore, reduce oil production. Conventional aromatic solvents (e.g., toluene, xylene) alone or in combination with various dispersants are used to remove asphaltene damage from the near-wellbore region. However, these aromatic solvents are expensive and are not environmentally friendly. The objective of this work was to systematically evaluate the asphaltene-solvating power of various non conventional solvents, including deasphalted oil, using a light-scattering technique. Experimental results suggest that deasphalted oil is a strong asphaltene solvent presumably because of its native resin and aromatic contents. Addition of asphaltene dispersants also increases the solubilizing power of the deasphalted oil. Furthermore, various refinery and heavy oil upgrader streams show strong ability to solubilize asphaltenes. Introduction Asphaltenes are defined as the n-pentane insoluble fraction of crude oil. They are polar molecules that aggregate together through aromatic - orbital association, hydrogen bonding and acid-base interactions. These asphaltene molecules also contain some heteroaromatics (aromatics with nitrogen, sulphur, and oxygen atoms included in the structure). They exist as platelets and are maintained in suspension by maltenes and resins. The growth of the aggregates is limited by the association of asphaltenes with resins in solution. The molecular weight of these aggregates can grow to several hundred thousand grams per mole. Asphaltene-solubility modelling studies based on the principle of colloidal suspension have been reported in the literature. In several cases, molecular theory has also been used to predict the dynamics of asphaltene flocculation.

Effect of Precipitating Conditions on Asphaltene Properties and Aggregation

“…The last studied sample was one asphaltene enriched in resins, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 solubility purposes. 57 A second interpretation, more alike to what was discussed in the preceding paragraphs, is provided by the works of Acevedo, Castillo and coworkers, 58,59 who showed that low solubility parameter asphaltenes fractions were found able to improve dissolution of "core asphaltenes" and modify their adsorptivity over solid surfaces. It is believed that low solubility parameter asphaltenes as described by …”

A Systematic Approach for Experimental Study of Asphaltene Deposition for an Abu Dhabi Reservoir Under WAG Development Plan

“…Various laboratory techniques such as fluorescence spectroscopy, 10 conductive measurements, 11 acoustic resonance, 11,12 gravimetric, 13 and light-scattering technique (LST) [14][15][16][17] have been used in determining the onset of asphaltene precipitation conditions. A general summary of the various techniques can be found in Reference 18.…”

Ready for Gas Injection: Asphaltene Risk Evaluation by Mathematical Modeling of Asphaltene-Precipitation Envelope (APE) With Integration of All Laboratory Deliverables

“…Asphaltene problems have been treated mechanically, chemically, and/or operationally. Among available remedies in each technology that have been widely applied in the world (Jamaluddin et al 1996;Avila et al 2001;Kokal et al 2003;Wang and Civan 2005;Hamid 2006;Al-Ghazi and Lawson 2007;Frost et al 2008), the most conventional ways have been applied in our target fi eld. The selection of remedial action was based on operational and cost reasons.…”