To get a better understanding of the phase behaviour of these hyberbaric reservoirs we are studying the phase behaviour of binary and ternary model reservoir fluids composed of methane and long-chain n-alkanes.
In this contribution, the thermal behavior, upon heating, was studied for 4 pure alkanes: eicosane, tetracosane, triacontane and tetracontane at pressures from 10 MPa to 150 MPa. The experiments were performed using the transitiometer developed and described by Randzio et al. .The calorimetric signal, pressure and temperature was measured using a very slow heating rate to guarantee thermal equilibrium.
It was found that from the compounds studied, eicosane was the only one that did not present a solid-solid transition; the other compounds show a solid-solid transition a few Kelvin below the solid-liquid transition temperature. This solid-solid transition disappears when the pressure is increased in a triple point of type: solid-solid-liquid.
1. S.L. Randzio, J. Therm. Anal. 46 (1996) 335-336.