Thomson equation points to lower boiling points of hydrocarbon solvents in capillary systems
Thomson equation points to lower boiling points of hydrocarbon solvents in capillary systems lead image
Extracting hydrocarbons often relies on reducing the viscosity of heavy oil by heating it or injecting solvents. The sole use of solvents is unfeasible because of high economic cost mainly emerging from the low rate of solvent retrieval. Combining heating and solvent methods by alternate injection to retrieve solvent requires precise estimation of temperature needed. One new study applies one of the most established equations of modern thermodynamics to the problem.
Al-Kindi and Babadagli present findings from experiments that have examined how to use the classical Thomson equation to model pore scale thermodynamics in hydrocarbon solvents. By testing the boiling temperature of two solvents, heptane and decane, the investigators found that boiling points decreased with the size of capillary pores, yielding both agreement and discrepancies with what is predicted by the Thomson equation depending on the scale.
“To put an extra 10 or 20 degrees into your reservoir to retrieve your solvent is a big cost,” said Tayfun Babadagli. “What you see in a porous medium underground is not the same as above conditions.”
The pores in rocks through which oil is extracted represent a tight capillary system. The researchers recreated such conditions using closely affixed glass plates called Hele-Shaw cells and more complex micromodels of rocks that had both uniform and heterogeneous pores.
Boiling point temperatures gradually decreased as the gap thickness decreased from 1.2 centimeters to 0.04 millimeters. They found the equation works for pore sizes less than 1000 nm, but overestimates for larger pore sizes.
Babadagli said the general approach could be applied to oil and natural gas extraction from unconventional reservoirs under non-isobaric and non-isothermal conditions . He hopes to investigate the effects in rock specimens.
Source: “Revisiting thomson equation for accurate modeling of pore scale thermodynamics of hydrocarbon solvents,” by Ilyas Al-Kindi and Tayfun Babadagli, Physics of Fluids (2019). The article can be accessed at https://doi.org/10.1063/1.5127754 .
