Computer-assisted design of oil additives: hydrate and wax inhibitors

Abstract

In this paper we present the results of a molecular simulation study of low dosage anti-freeze agents for two common problems that occur during oil and gas transport: gas hydrate crystallization and wax deposition. Direct molecular dynamics simulations are presented of the nucleation and growth of methane hydrate from a liquid water film, and of the suppression of this growth in the presence of a well-known kinetic inhibitor—polyvinylpyrrolidone. In the case of wax inhibition we present a simple model for predicting the activity of comb-like polymers, which is likely to be useful for identifying the most active inhibitor from within a given class. The method is applied to a set of random copolymers and shown to correlate well with experimental data.

Acknowledgments

This work was supported under EPSRC grant GR/N06441 and by BP Exploration through the Wax Attack programme.

Notes

† Present address: Department of Physics and Astronomy, University College, London, WC1E 6BT, UK.

†In reality, these polymers were synthesized by starting with polymethylacrylate and replacing the methyl groups by octadecyl groups. As a result, the terminology ‘percentage conversion’ refers to the percentage of octadecyl side chains, so that ‘100% conversion’ is the PA18 homopolymer.