Revisiting Thomson Equation for Accurate Modeling of Pore Scale Thermodynamics of Hydrocarbon Solvents

Abstract

As stated by the classical Thomson equation, the pore scale thermodynamics of solvent is different from bulk conditions being critically controlled by capillary characteristics. This equation shows that the boiling points decrease remarkably as the pore size and interfacial tension become smaller. This paper investigates this phenomenon for hydrocarbon solvents experimentally and compares the results with the values obtained from the Thomson equation to test its applicability in modelling heavy-oil recovery by solvents under non-isothermal conditions. As an initial step, the boiling temperature of different single component solvents (heptane and decane) was measured by saturating Hele-Shaw type cells with variable apertures (ranging from 0.04 mm to 5 mm) and monitoring the boiling process. One experiment was run with a thickness of 12 mm to represent the bulk case. As the aperture (pore size) became smaller, the boiling point temperature decreased. For example, the measured boiling temperatures of heptane and decane were approximately 57.7°C and 107.4°C for the aperture values less than 0.15 mm, which were considerably lower than the "bulk" values (around 40%). In the next step, the same experiments were repeated using micromodels representing porous media. The micromodel (grain diameter of 0.15 mm and a pore throat of 0.075 mm) was designed with uniform properties (constant grain diameter and pore throat). By using the Thomson equation, the boiling points of the selected liquids were mathematically computed and compared with the experimental results from Hele-Shaw experiments.

Propagation and Entrapment of Hydrocarbons in Porous Media under Capillarity Controlled Phase-Alteration Conditions: A Visual Microfluidics Analysis

“…Phase alteration is a commonly encountered phenomenon in many engineering applications and natural processes in underground reservoir systems or synthetic porous media. − These include CO 2 sequestration, conventional and unconventional oil and gas production, geothermal systems, waste deposition, and synthetic porous systems such as filters. Throughout the primary production period of oil or gas, the decline of reservoir pressure leads to the vaporization of hydrocarbons, starting from the lighter components.…”

“…Small (nano)­capillaries have a major impact on the process as boiling occurs quicker (at lower temperatures) compared to larger capillaries. , Therefore, capillary size and distribution controls the whole process, meaning further phase change and the displacement and entrapment of the gas and liquid phases. In our prior studies, − vaporization temperatures of various hydrocarbons were studied using different lab-scale capillary models such as Hele–Shaw silica-glass cells, microfluidics chips, and reservoir rocks (Berea sandstone, Indiana limestone, tight sandstone, and shale). These studies qualitatively and quantitively investigated the phase behavior (boiling temperatures and pressures of hydrocarbon solvents) and showed that phase change occurs more quickly as the medium becomes tighter.…”