ADSORPTION OF ASPHALTENES AND RESINS ON ORGANIC AND INORGANIC SUBSTRATES AND THEIR CORRELATION WITH PRECIPITATION PROBLEMS IN PRODUCTION WELL TUBING

The solute-solid adsorption isotherms (SSA) of asphaltenes and resins were measured using the inorganic fraction (97% SiO2) of the deposit that plugged the tubing of a production well as an inorganic adsorbent. In other experiments, Ceuta asphaltenes and the product (HA) of heating them at 350-degrees-C for 11 h were used as organic adsorbents in heptane, toluene and heptane-toluene at 26-degrees-C. Ceuta and Furrial asphaltenes on the inorganic substrate resulted in multilayer formation (L-3 type adsorption) whereas a Cerro Negro sample gave simple Langmuir-type adsorption. A possible correlation between these results and the tendency of the asphaltenes to precipitate from the crude oils is suggested. Saturation, multilayer formation and pore penetration were apparent in the SSA experiments for the system resins-heptane-asphaltenes. SSA results for the system resins-heptane/toluene-HA were consistent with the steric stabilization theory of colloidal dispersions. Adsorption of aggregates or micelles of asphaltenes was apparent in both the organic and the inorganic substrates.