Different Adsorption/Occlusion Properties of Asphaltenes Associated with Their Secondary Evolution Processes in Oil Reservoirs

Abstract

In this work, two asphaltenes derived from the same set of source rocks, C1 from a crude oil and C2 from an oil sand, were studied, concerning their adsorption/occlusion properties. From the adsorbed components, saturated and aromatic hydrocarbon distributions are distinctly different for these two asphaltenes. For example, some n-alkanes and alkyl-branched alkanes were found adsorbed in C2 asphaltenes, whereas only some cyclic compounds, particularly terpanes were detected from C1 asphaltenes. This difference is due to their different evolution processes in oil reservoirs, and the exchangeability between asphaltene-sorption compounds and those from outside of the bulk phase is different for these two asphaltenes. However, from the asphalteneocclusion compounds, saturated hydrocarbons show almost the same distribution features. This is consistent with the fact that these two asphaltenes were derived from the same set of source rocks, therefore, occluded almost the same original oils from the source rocks. The experimental results suggest that substantial microporous units exist inside the macromolecular structures of asphaltenes and the asphaltene-derived adsorption/occlusion phenomena extensively occur in oil reservoirs. It seems that asphaltene occlusion should have taken place before asphaltene was detached from kerogen.

Waxes in asphaltenes of crude oils and wax deposits

“…In other words, the waxes are isolated from the oil system from which the asphaltenes have been removed beforehand [from maltenes (Branthaver et al 1983;Elsharkawy et al 2000;Fazeelat 2006;Alcazar-Vara and Buenrostro-Gonzalez 2011) or saturates (Yang and Kilpatrick 2005;Lu et al 2008)]. However, the traditional methods used to isolate asphaltenes by adding 40 volumes in excess of low boiling point paraffin hydrocarbons can produce a fraction which is contaminated with a significant amount of waxes (Chouparova and Philp 1998;Thanh et al 1999;Liao et al 2006;Acevedo et al 2009;Coto et al 2011). The presence of paraffin hydrocarbons in asphaltenes can be explained by their coprecipitation as a result of low solubility in low molecular weight n-alkanes (Thanh et al 1999;Coto et al 2011), by interaction between the alkyl lateral chains (C 7 -C 10 ) of asphaltenes with high molecular weight n-alkanes (Garcia and Carbognani 2001;Stachowiak et al 2005;Ganeeva et al 2014), and by their adsorption and/or occlusion inside asphaltene aggregates (Liao et al 2005(Liao et al , 2006Acevedo et al 2009;Gray et al 2011).…”

“…However, the traditional methods used to isolate asphaltenes by adding 40 volumes in excess of low boiling point paraffin hydrocarbons can produce a fraction which is contaminated with a significant amount of waxes (Chouparova and Philp 1998;Thanh et al 1999;Liao et al 2006;Acevedo et al 2009;Coto et al 2011). The presence of paraffin hydrocarbons in asphaltenes can be explained by their coprecipitation as a result of low solubility in low molecular weight n-alkanes (Thanh et al 1999;Coto et al 2011), by interaction between the alkyl lateral chains (C 7 -C 10 ) of asphaltenes with high molecular weight n-alkanes (Garcia and Carbognani 2001;Stachowiak et al 2005;Ganeeva et al 2014), and by their adsorption and/or occlusion inside asphaltene aggregates (Liao et al 2005(Liao et al , 2006Acevedo et al 2009;Gray et al 2011). Now, it is well-known that the asphaltenes exist as three-dimensional aggregates due to the strong intermolecular forces such as hydrogen bonding and p-bonding (Murgich 2002) and even at very low concentration as 50-150 mg/L in a good solvent such as toluene (Mullins et al 2012).…”

Geochemical quantification of mixed marine oils from Tazhong area of Tarim Basin, NW China

“…Recently, the characteristics of compounds adsorbed and occluded inside asphaltenes were used to identify mixed oils (Liao et al, 2006a, b;Zhao et al, 2010). Since asphaltenes can adsorb and even occlude hydrocarbons inside their specific molecular structures (Liao et al, 2005(Liao et al, , 2006c. Liao et al (2006a) employed a mild oxidation system where for asphaltenes of crude oils, the aliphatic components chemically bonded to the asphaltene structures were cleaved as aliphatic acids by the oxidative reagents.…”

Petroleum resins adsorption onto quartz sand: Near infrared (NIR) spectroscopy study

“…In papers [19][20][21] two asphaltenes derived from the same set of source rocks (from a crude oil and from an oil sand) were studied, concerning their adsorption/occlusion properties.…”