(524a) Influence of Nanoparticle Wettability on Absorption and Desorption Mass Transfer Rates at Elevated Pressure in a Simple Hydrocarbon System

In the petroleum industry, the time required for degassing, or the rate of gas evolution within a gas-liquid separator at elevated pressure, is usually determined by assuming thermodynamic equilibrium between the two phases and estimating the time required for entrained gas bubbles to rise out of the super-saturated liquid. Gas-liquid separator design using this approach does not fully account for the dissolved solution gas present within the super-saturated solution. Further, crude oil naturally contains several oil-wet and water-wet particles such as inorganic clay, sand, rust produced from corrosion, and precipitated asphaltenes. The influence of such nanoparticles on the rate of gas evolution from super-saturated systems has not been investigated, so it is critical to investigate this phenomenon in order to improve our understanding of separator design and performance.

In this study, we measured the rate of absorption and desorption of methane in n-dodecane with 1 wt.% solid (silica) nanoparticles of varying wettability. These measurements were conducted in a batch stirred tank system at a constant pressure of 1,000 psia, a temperature of 45 ^oC, and a mixing speed of 250 rpm. Three different silica nanoparticles were selected based on their wettability characteristics: hydrophobic (R812S), partially hydrophobic (R711), and hydrophilic (A200). The rates of absorption and desorption of methane in pure n-dodecane were found to be within experimental uncertainty. The rate of gas absorption and desorption decreased with the addition of partially hydrophobic nanoparticles (R711) and hydrophilic nanoparticles (A200). Hydrophobic nanoparticles (R812S) did not have any noticeable effect on the rate of gas evolution. In addition, the wettability of the nanoparticles influenced the bulk viscosity of n-dodecane.

Keywords: absorption, desorption, gas evolution, gas-liquid mass transfer, particles, silica, wettability, gas-carry under, solution gas