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This papar w selactad for presentation by an SPE Program Committae Iollowlng raviaw of infwmatlon wntainad in an abstraclsubmfttad by the author(s). Contents of the papar, = Pfe-td, heve not bwn revwad by the SOCIatYof Petrcieum Engineers and ara sut@t to correction by IF+Sauthcf(s). Tha materhl, as prasented. does not nacassarily raftect any position of the Scdefy of Petroleum Enginaars, its officers, w mambam. Papain prasentad at SPE maetin@ are subjact to publication revfaw by Ednorfal Commtiaaa of tha Soc@ty of Patrolaum Englnaws Pannbskm to copy is rastrfctedto an abstract of not rnoreihan 30b words. Illustrationsmay not ba copiad. Tha abmracf should Kmtain compicuws acknow!ecfgment of wham and by whom the papar Is prasantad. Write Librarian, SPE, P.O. Sox 8S3.936, Riihwcfson, TX 7&M3S&?8, U.S.A. Tatax, 16S245 SPEUT. MwiRAcrOriginal phase equilibria data on asphakenic mixtures show that the principal modellistic approaches described in the literature do not accurately reproduce asphaltene phase behaviour. A new, more reliable modellistic approach is proposed in this paper, and a procedure for predicting the stability of asphaltene soiutions is outlined. Application of the new model to two oils gives satisfactory results when compared with field obsemations.

In spite of its importance, wax deposition is still not fully understood, and a reliable physical description of wax deposition is still to be agreed upon. Up to now, the focus in wax studies has been mainly on the radial transport of waxes to the cold wall through molecular diffusion, but other mechanisms that have been cited (and so far neglected) may count on the kinetics of deposit formation. An analysis of the experimental evidence is presented here, leading to the conclusion that an important role may be played by the axial convective transport and the oil gelation on the cold surface (i.e., by the bulk liquid-to-gel change driven by the temperature change). Gelation is faster than molecular diffusion and may lead to the formation of a loose solid network that is slowly filled by diffusion (by aging) in a successive step. An experimental apparatus has been employed to measure the gelation kinetics both on a model mixture and on a stock tank oil. Obtained data have been modeled by employing a classic solution of the conductive heat transfer problem. The qualitative agreement obtained indicates that the physics involved in gelation have been well identified.

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