Thermodynamic Measurement and Prediction of Paraffin Precipitation in Crude Oil

Abstract

Economically and technically viable methods for controlling paraffin buildup in pipelines and wellbores are critical to the production of crude oil in deep water and cold environments. Conoco has identified laboratory test methods and developed a paraffin prediction program to better quantify the paraffin (wax) deposition potential of a crude oil and to evaluate or develop methods of preventing or controlling paraffin buildup. This paper will describe the thermodynamic paraffin model and the complementary laboratory test methods. A companion paper will describe the kinetic deposition model and the associated laboratory and field data.

Cloud Points: Can We Measure or Model Them?

“…It is also possible that for low wax content crude oils, WAT and/or the presence of paraffin crystals may go completely undetected by viscometry, DSC and/or LT, leaving the investigator unaware of potential waxing problems. The CPM is generally deemed to be the most sensitive and the only direct visual technique applicable for all non-biodegraded oils including opaque fluids Erickson et al, 1993).…”

“…(Erickson et al, 1993;Coutinho et al, 2001) or may be described using a free energy model (Won, 1986;Hansen et al, 1988;Coutinho et al, 1996;Lira-Galena et al, 1996). For high pressure systems (live oils), on the other hand, the liquid phase is generally described using an Equation of State (Lira-Galena et al, 1996;Pan et al, 1997;Pauly et al, 2000).…”

“…Either the authors assume that the solid phase is a sum of independent pure components or pseudo-components Lira-Galena et al, 1996;Pan et al, 1997) or that it is made up of a solid solution, stable or not, of all the materials that crystallize. Some authors that consider the formation of a solid solution assume it being ideal (Erickson et al, 1993;Coutinho et al, 2001;Won, 1986;Hansen et al, 1988;Coutinho et al, 1996).…”

Determination of Solid-Liquid Equilibria Data for Mixtures of Heavy Hydrocarbons in a Light Solvent

“…Crude oil WPT has been measured using conventional experimental methods such as differential scanning calorimetry (DSC) [4][5][6][7][8], viscometry [5][6][7][8][9][10], near-IR spectroscopy (NIR) [11] and cross-polarized microscopy (CPM) [5,7,[12][13][14][15]. The measurement of WPT by DSC is explained in detail in a later section in this report.…”

Evaluation of Wax Deposition and Its Control During Production of Alaska North Slope Oils

“…Wax precipitates from crude oil when the operating temperature is at or below the WAT (cloud point temperature). It has been reported that wax deposition will not occur until the operating temperature falls to or below the WAT (Erickson et al, 1993). All other factors actually lead to wax deposition when the temperature is already at or below the cloud point.…”