Cloud Points: Can We Measure or Model Them?

Abstract

The terminology “cloud point ” has been traditionaly adopted by the American Society for Testing and Materials (ASTM) D2500 to refer to the temperature at which “cloudiness ” of a relatively transparent petroleum fluid is observed upon cooling. The cloudiness forms as a “finite and detectable ” amount of wax and/or paraffins precipitates from the test fluid contained in a 1-in ( ~ 30 mm) diameter glass tube. Nowadays, more sophisticated techniques of differing measurement principles and varying degrees of sensitivity have been developed to measure cloud points of petroleum fluids including opaque hydrocarbon systems (dark oils). Alternative terminologies like wax appearance temperature (WAT) and wax precipitation temperature (WPT), amongst a few others, have also emerged and are used interchangeably. Meanwhile, numerous characterization and modeling efforts have been made to simulate “measured ” cloud points of petroleum fluids. The goals of this paper are to provide an objective review of the concept of “cloud point ” and to illucidate the adequacy and limitations of the measurement techniques and modeling approaches.