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 t hat plugged the tubing of a production well as an inorganic adsorbent. In other experiments, Ceuta asphaltenes and the product (HA) of heati ng them at 350-degrees-C for 11 h were used as organic adsorbents in h eptane, toluene and heptane-toluene at 26-degrees-C. Ceuta and Furrial asphaltenes on the inorganic substrate resulted in multilayer formati on (L-3 type adsorption) whereas a Cerro Negro sample gave simple Lang muir-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-asphalt enes. SSA results for the system resins-heptane/toluene-HA were consis tent with the steric stabilization theory of colloidal dispersions. Ad sorption of aggregates or micelles of asphaltenes was apparent in both the organic and the inorganic substrates.