Enhanced Oil Recovery – EOR
Inter Facial Tension
Investigation of surface and interfacial tension requires a viewable environmental chamber, temperature and pressure control and observation equipment. The IFT cell operates to 10000psig at 350°F. Within this range most reservoir conditions can be accurately and safely simulated. This allows conducting experiments in an oxygen-free environment as opposed to normal room-condition IFT measurements. It is important to measure the interfacial tension at the reservoir temperature because it changes dramatically with temperature. The IFT cell is heated by band heaters and insulation jackets (instead of placing the cell in an oven), so that the valve is not heated. The cell is leveled on a vibration-free table that reduces the interference of constant low-frequency vibration. A drop phase is created and put in contact with the external phase through a needle tip, located in the cell at reservoir conditions. The IFT pendent drop visual cell includes a light source to illuminate the drop phase in its glass-windowed Chamber and a low power video microscope connected to a computer.
Measurement of the drop dimensions and fluid densities enables calculation of interfacial tension. The low power video camera is used to capture the drop and embedded algorithms in the software to compute the interfacial tension. As part of the interfacial tension measurements, the program performs a numerical integration of the drop profile to determine the volume and surface area. This opens several possibilities for additional or complimentary use of the program. A 2-step process determines interfacial tension as follows. First, size parameters Ro and β are determined from the drop profile. Secondly interfacial tension is calculated from these parameters by the equation: Δρ g Rο2 / β
- Δρ = difference in fluid densities, g/ml
- g = local gravitational constant, cm/s2
- Rο = radius of curvature at the drop apex, cm
- β = shape factor (calculated from drop dimensions)
- DE = R’ + R” = maximum diameter
- DS = diameter at a distance DE from the apex
By convention, Δρ is defined such that Δρ and β is negative for pendant drops.