Adsorption of Asphaltenes and Its Effect on Oil Production

Abstract

Summary Asphaltenes show moderate capacity to reduce oil/water interfacial tension (IFT) and/or to stabilize emulsions. However, in the presence of other surfactants and fine particles presenting intermediate presence of other surfactants and fine particles presenting intermediate wettability, these compounds enhance emulsion formation and stability, At the solid/solution interface, asphaltenes adsorb up to a saturation value of 2 to 3 mg/g and modify the mineral wettability. At the oil/gas interface, the asphaltic fractions adsorb as single molecules or as liquid crystalline phases, causing foaming problems. Introduction Asphaltenes and resins are the polar fractions of crude oil and bitumen that can be precipitated by the addition of low-molecular-weight alkanes. These fractions are formed by molecules containing paraffinic, naphtenic, and aromatic hydrocarbons and functional groups containing oxygen, nitrogen, and sulfur. Owing to this amphiphilic character, these compounds, also denominated asphaltic material, possess the ability to aggregate and to adsorb to interfaces. These processes normally are associated with such production problems as sludge formation, foaming in the primary treatment, and wettability changes that may be detrimental to oil production. In this paper, we investigate the behavior of asphaltic materials at the liquid/liquid, solid/liquid and liquid/gas interfaces. We isolated asphaltenes and resins from the Carmopolis field, an onshore field in the Sergipe-Alagoas basin, and from the Cherne field, an offshore field in the Campos basin. Carmopolis crude presents a basic sediments and water (BS&W) of about 80% and forms very stable emulsion. Cherne crude, however, has a BS&W of 10% but precipitates asphaltic sludge during acid stimulation operations. Some preliminary studies also were carried out on crude oil foam with samples from the Pampo field (offshore in the Campos basin) that displays a natural tendency to foaming.

Understanding Mechanisms of Asphaltene Adsorption from Organic Solvent on Mica

“…While pipeline deposition can lead to pipe plugging, adsorption onto clay solids modifies their wettability, decreasing efficiency of oil liberation from the solids and increasing solids partitioning at the oil-water interface. [14][15][16][17][18][19][20] In oil production, the formation of a complex multiphase dispersion layer in the middle of oil-water separation vessel, known as rag layers, is frequently encountered. 21,22 The rag layers are extremely stable multiemulsions with the stabilizing species identified as surfactants, asphaltenes and inorganic fine particles.…”

“…16,17 Common clay minerals used in adsorption studies are kaolinite, illite, montmorillonite, mica and chlorite. The common non-clay minerals used in adsorption studies are quartz, calcite, feldspar, limestone, and dolomoite.…”

“…Several authors have reported Langmuir-type adsorption isotherms, indicating the formation of a monolayer of asphaltenes at the toluene-quartz interface. 17,29 Whereas, others have found stepwise or linear increase in adsorption, suggesting a multilayer adsorption process, for example, toluene to glass, and toluene to quartz/dolomite/kaolin/calcite. 27,30,31 Ellipsometry studies confirmed the presence of multilayer asphaltenes adsorbed on solids.…”

A DPD study of asphaltene aggregation: The role of inhibitor and asphaltene structure in diffusion-limited aggregation

“…Physisorption is regarded as the dominating mechanism for asphaltene adsorption and aggregation [23]. The acid-base reactions between the DBSA acid group and the asphaltene heteroatomic groups occur at relatively short distances below the Bjerrum length, and the relatively strong electrostatic interactions in the corresponding ion-pairs are accounted for qualitatively in our model by using relatively strong short range interactions in the simulation [24], rather than implementing the Coloumb force.…”

Wetting Alteration of Solid Surfaces by Crude Oils and Their Asphaltenes

“…Anything less ideal than brine and oil in the pore spaces of a rock is hard to imagine. Nevertheless, there is a great deal to be learned from properly designed contact angle experiments (Anderson, 1986;Morrow, 1991;Buckley, 1996a González et al (1991González et al ( , 1993González et al ( , 1994 Acevedo et al IR spectra. More asphaltene adsorbs on Ca 2+ forms and less on preheated, drier clays.…”