Investigating the Viscosity Reduction of Ultra-Heavy Crude Oil Using Hydrocarbon Soluble Low Molecular Weight Compounds to Improve Oil Production and Transportation

Abstract

Abstract Heavy oil reservoirs contain a large amount of hydrocarbons that are relatively difficult to produce and lift to the surface due to the very low mobility of these heavy oils. Even after producing these heavy oils, transportation problems arise as well due to the extremely high viscosities that these oils have. This research investigates the ability of several low cost chemical solvents to reduce heavy oil viscosity and also develops four novel formulations with high stability under harsh reservoir conditions and high solubility in crude oil to aid in the reduction of heavy oil viscosity and hence increase production from these reservoirs, and improve transportation of these heavy oils. A heavy crude oil from Kansas USA was used to conduct all experiments. The oil composition was determined using gas chromatography-mass spectrometry, and the asphaltene weight percent was determined using the conventional asphaltene solubility detection test. The pure chemical additives researched include kerosene, xylene, toluene, naphtha, and heptane. These chemicals were added with 5, 10, and 20 wt% to the crude oil, and the viscosity was measured using a viscometer at temperatures of 25, 40, 60, and 80 °C. The oil was found to have 5.73 wt% asphaltene, which is a good indication that the oil is heavy, since asphaltene is one of the heaviest components in the crude oil. Of all the pure chemicals used, toluene managed to reduce the oil viscosity the most, followed by xylene, then kerosene, and finally naphtha. Heptane could not be used since it had a very low boiling point, and thus evaporated very quickly, and also asphaltene was insoluble in it which resulted in a significant amount of asphaltene precipitation which would result in severe operational problems during the production operation. The novel formulations managed to reduce the oil viscosity significantly, however the pure toluene still showed slightly more oil viscosity reduction. The main advantage that the novel formulations had over the toluene however was their higher stability, even under harsh conditions due to the incorporation of a stabilizing agent within them. The main difference between the chemical compositions of the formulations was the concentration of the stabilizing agent, and the addition of some other chemicals. This research shows the capability of several chemical solvents to reduce heavy oil viscosity, and also develops four novel formulations with high stability to reduce heavy oil viscosity. These formulation can help increase oil recovery from heavy oil reservoirs, and also reduce lifting and transportation costs for these oil.