Determining Wax Type: Paraffin or Naphthene?

Paraffin-wax deposits are known to be a worldwide problem in the upstream petroleum industry. Considerable resources are expended on inhibiting or removing wax deposits every year. Paraffin wax is not the only type of crude-oil-based wax. Microcrystalline waxes, composed of naphthene and iso-paraffin molecules, also exist but are not well studied. The predominance of paraffin (also called macrocrystalline) wax and paraffin-wax-inhibition techniques will likely lead to paraffin-wax treatments being applied to naphthene-based reservoirs. It is unclear how well a paraffin-based treatment will apply to naphthene-based oil. The current study investigates the use of cross-polarized microscopy (CPM) to determine if a crude oil contains macrocrystalline or microcrystalline waxes. The type of wax present in the crude oil can be determined using crystal morphology and size. This study demonstrates that paraffin-wax crystals are elongated structures with statistically larger sizes than the microcrystals. Microcrystalline waxes are shown to be statistically smaller and rounded structures.