Characterization of Carbon-Dioxide-Induced Asphaltene Precipitation

Abstract

Asphaltene precipitation continues to be one of the major problems during the carbon dioxide enhanced oil recovery process. Supercritical carbon dioxide is injected into oil reservoirs to enhance oil recovery in the tertiary phase of production. Development of multiple-contact miscibility is important in the success of a carbon dioxide flood. In this paper, we establish conditions at which solids are formed in carbon dioxide–oil systems and characterize these solids by a variety of analytical techniques. Crude oils containing low and medium amounts of heptane-insoluble asphaltenes were used in the study. A high-pressure thermodynamic system was designed and fabricated, and a number of thermodynamic experiments were performed with dead and live oils. Multiple-contact experiments were first performed by adding a “light–intermediate” cut to the crude oil and later by creating actual multiple contacts. Precipitation onset for dead oils was obtained between 20 and 30 mol % CO2. CO2-induced solids consisted of ...