Control of wax deposition: An experimental investigation of crystal morphology and an evaluation of various chemical solvents

Four commercial solvents and o-xylene have been tested for their effectiveness in remediating paraffin (wax) depositions from three different dead oils. The dead oils were sampled from the North Sea, Alberta and Gulf of Mexico, respectively. Representative field solvent/oil concentrations of 2000 and 4000 ppm (vol) were prepared for each oil and solvent considered in this work. Two state-of-the-art techniques, namely a cross polar microscopy (CPM) and a rheometrics mechanical spectrometer (RMS 800), were used to study paraffin crystal habits and/or morphologies at 32°F, wax dissolution temperatures (WDT), and pour point temperatures of the three dead oils with and without solvents. It is found that in almost all cases, the 2000 pm (vol) solvent concentration yielded similar or better remediation results than mixtures with 4000 ppm (vol) solvents. More importantly, it is shown that the remediation of wax deposition depends not only on the solvent concentration but also the type oil and, in turn, waxes being treated (i.e., case specific). In some cases, the relatively cheap solvents outperform the more expensive o-xylene in dissolving wax deposits. Finally, a laser based solids detection system (SDS) was used to study the effect of o-xylene on the wax appearance temperature (WAT) of a second live fluid from the Gulf of Mexico.