A Fundamental Study of Asphaltene Deposition

Abstract

Asphaltenes are a solubility class of petroleum crude oil that can destabilize and deposit in both upstream and downstream processes. In this study, asphaltene deposits were generated in metal capillaries by heptane addition to crude oils, and it was found that deposition is caused by submicrometer asphaltene aggregates. Deposits were generated at heptane concentrations above and significantly below the instantaneous onset point. Analysis of the results reveals that the governing factor controlling the magnitude of asphaltene deposition is the concentration of insoluble asphaltenes present in a crude oilprecipitant mixture and the instantaneous onset point is irrelevant to the deposition process. Electron microscopy images of the deposits represent the first images and confirmation of arterial growth in laboratory generated asphaltene deposits. The axial deposit profile was found to be highly nonuniform. In addition, deposits formed shortly after when oil and heptane mix, revealing that the destabilization of asphaltenes occurs virtually immediately after a precipitant is added. The results were reproduced with a second crude oil, indicating that asphaltene deposition behavior is broadly applicable.

Temperature effects on solubility of asphaltenes in crude oils

“…At higher temperature, the colloidal asphaltenes are small in amount and tend not to form strong associations, because the resins effectively disperse the colloids (Branco et al, 2001;Hoepfner et al, 2013;Maqbool et al, 2011). This is because the part of asphaltenes is dissolved leaving enough mass of the resins and oil to keep the remaining smaller aggregates of asphaltenes well peptized in the oil at higher temperature.…”

“…Much of the research has been driven by the tendency of asphaltenes to aggregate, precipitate and deposit onto surfaces (Arciniegas and Babadagli, 2014;Hoepfner et al, 2013;Mullins et al, 2007;Spiecker et al, 2003;Maqbool et al, 2011). Deposit formation in crude oil processing can be attributed to various factors but asphaltenes are generally considered as main precursors of deposit formation on heat transfer surfaces in crude oil processing (Hoepfner et al, 2013;Murphy and Campbell, 1992;Wiehe, 2006). The presence of asphaltenes on heat transfer surfaces further favors fouling of equipment because asphaltenes are more prone to attach to already coked surfaces than a clean metallic alloy surface (Asprino et al 2005).…”

Integrated one-dimensional modeling of asphaltene deposition in wellbores/pipelines

“…Asphaltene deposition can appear at various stages of oil production, transportation and processing, leading to arterial blockages of wellbores, pipelines, separators, heat exchangers and other surface facilities [1][2][3]. As oil flows in wellbores or pipelines, due to the change in pressure (p), temperature (T) and oil composition, asphaltene precipitation usually takes place producing particles.…”

Experimental Investigation and Application of the Asphaltene Precipitation Envelope

“…3,6,11 In order to establish the consistent and clear terminology, several terms (e.g., "deposition" and "precipitation") which will be used in this paper are defined. 12,13 Firstly, "precipitation" refers to the whole process of asphaltenes converting from stable conditions to the aggregation or precipitation of asphaltene in micron level. Secondly, "deposition" will be used to describe the suspended precipitated asphaltene detached from the crude oil and deposited in the solid-surface (e.g., the porous media).…”

“…14 Simultaneously, most of the laboratory experiments and field results investigated that the effect of the pressure, temperature, and oil composition on AP are all important factors. 12,15,16 Zendehoudi, S. et al found that the contribution of the temperature, pressure, and oil composition to the AP amount accounts for 37%, 36%, and 27%, respectively. 18 In addition, for the actual oilfield, the operating pressure has significant impacts on the AP phenomenon during the process of primary oil recovery.…”