Asphaltenes are known as the ‘cholesterol’ of crude oil. They precipitate, adhere to surfaces and, in the worst cases, cause costly pipe blockages (see photograph below right). Furthermore they alter the wetting characteristics of mineral surfaces within the reservoir, hindering oil recovery efficiency.
Asphaltenes are a complex mixture of different molecules with similar chemical characteristics which are insoluble in aliphatic solvents (e.g. heptane) but soluble in aromatic ones (e.g. toluene). Even at very low concentrations in ‘good’ solvents, they still have a propensity to form ‘nanoaggregates’ whose structure and formation remain largely unknown despite much research. Small-angle neutron scattering (SANS) has been used to examine asphaltenes in deuterated toluene in the absence and presence of laponite clay, the hypothesis being that the clay surface would enhance asphaltene aggregation.
This appears to be borne out by the change in the radius of gyration (Rg) of the asphaltene nanoaggregates as a function of temperature (see figure). Hopefully this observation will help provide a route for the oil industry to predict and control asphaltene precipitation and deposition in the field.
Graph of radius of gyration for asphaltene samples with (white) and without (blue) Laponite clay.
Research authors: TF Headen, NT Skipper (University College London), ES Boek (Schlumberger Cambridge Research), RK Heenan (ISIS)
Further information: J Roux et al., Langmuir 17 (2001) 5085
Notes for Editors:
1. About the London Centre for Nanotechnology
The London Centre for Nanotechnology is an interdisciplinary joint enterprise between University College London and Imperial College London. In bringing together world-class infrastructure and leading nanotechnology research activities, the Centre aims to attain the critical mass to compete with the best facilities abroad. Research programmes are aligned to three key areas, namely Planet Care, Healthcare and Information Technology and bridge together biomedical, physical and engineering sciences. Website: www.london-nano.com
2. About ISIS
ISIS is a world-leading centre for research in physical and life sciences operated by the Science and Technology Facilities Council at the Rutherford Appleton Laboratory, Oxfordshire, UK.
ISISsupports an international community of around 1600 scientists who use neutrons and muons for research in physics, chemistry, materials science, geology, engineering and biology. It is the most productive pulsed neutron spallation source in the world.