J. Castilloa, S. Acevedoa, C.E. Canelona, H. Carrier b, JL Daridon b
a) Facultad de Ciencias, Escuela de Química, Universidad Central de Venezuela, Caracas, 47102, 1020ª Venezuela,
b) Laboratoire des Fluides Complexes, UMR 5150, Université de Pau et des Pays de l’Adour, BP 1155, 64013 Pau Cedex. France
The prediction and the prevention of
solid formation during production, transportation and treatment of oil
containing high-molecular-weight organic compounds such as asphaltenes are one
of the challenges for oil industries. The influence of pressure, temperature or composition changes on the
stability of asphaltenic crudes can be evaluated if it is possible one is able
An experimental set up composed of an
external sensor connected to a HP/HT cell by two optical fibers, placed in
front of the sapphire window of the cell has been developed to measure the
changes in the refractive index (RI) of liquids. Depending of the reflectivity
of a laser beam emitted by one of the fiber in the interface sapphire-liquid,
the light intensity in the collecting fiber will vary. Those changes in the
reflected intensity are related by the Fresnel reflectance coefficient to the
refractive index of the sample. One of the key point of our apparatus is that
the calibration can could be carried out at
atmospheric pressure as the optical device, placed outside the cell, is not
affected by the pressure and the temperature of the experiment.
The experimental device is presented and it is demonstrated that it permits to measure the refractive index of opaque samples and allows a determination of RI changes of 10-5. The temperature, composition and pressure effects on the stability of two Venezuelan asphaltenic crudes are presented. Effects of CO2 injection on the same systems up to 70 MPa and 383 K, are also discussed.