Vapor-liquid equilibrium data for the binary system methane + carbon dioxide were measured at 230, 250, and 270 K. The ethane + carbon dioxide system was studied at 207, 210, 213, 230, 250, and 270 K, and the methane + ethane system was studied at 210, 230, 250, and 270 K. Ternary vapor-liquid equilibria for the methane + ethane + carbon dioxide system were measured at 230 K over the pressure range from 1.15 to 6.59 MPa. The Peng-Robinson equation of state was used to model the systems, and binary interaction coefficients are reported.

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. Laboratory test methods and a computational model have been developed to predict rates of paraffin deposition in pipelines and the effect of long-term deposition on the pipeline pressure drop and temperature profile. The model has been incorporated into a fully menu-driven program that runs on a personal computer. The two major portions of the program are the thermodynamic model which is used to calculate solid-liquid-vapor phase equilibria and the kinetic model which is used to predict the deposition and paraffin buildup rates. The thermodynamic portion is described in a companion paper'.The kinetic model is based on information present in the literature and on several hundred measurements of paraffin deposition rates in a laboratoryscale test loop.

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.

A thermodynamic model for paraffin formation is presented which accurately accounts for the effects of light ends, such as methane, ethane, and propane, and high pressures. The model uses the Simplified, Perturbed Hard Chain equation of state for all fluid phase fugacities and contains no adjustable parameters for the solid-liquid equilibria. Model predictions are compared to binary solid-liquid, solid-vapor, and solid-liquid-vapor equilibria data with good results. Also, a high-pressure, coldstage microscope technique was developed to measure cloud points of live oils with which to test the model. Comparisons between the predicted and measured cloud points for live oils are presented.

No abstract