Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 087
Flow Assurance: Micro- and Macro-Scale Evaluation of Low Dosage Hydrate Inhibitors
Tohidi, B., Danesh, A., Todd, A.C., Yang, J., Ren, S.R., Arjmandi, M., Burgass, R.W., Carnegie, E., Anderson, R., Biderkab, A.-B., and Zain, Z.
UK DTI IOR Seminar, Aberdeen, Scotland, UK, 24 June 2003.
A three-year research programme on micro- and macro-scale evaluation of low dosage hydrate inhibitors started in September 2002. The objectives are to study the mechanisms of inhibition offered by Low Dosage Hydrate Inhibitors (LDHIs) and improve their performance by better design and/or deployment procedures. A novel experimental technique based on visual observation capabilities of a high pressure glass micromodel will be employed to analyse gas hydrate nucleation and growth in the presence and absence of LDHIs. The tests will be repeated in a high-pressure kinetic rig to examine the effect of various parameters on the performance of LDHIs. The project deliverables include: Visual data on gas hydrate nucleation and growth in various hydrocarbon systems. Effect of LDHIs on gas hydrate growth, using the high-pressure glass micromodel set-up. Guidelines on design and deployment of LDHIs for deepwater applications. Guidelines on screening of potential LDHIs using laboratory-based test procedures. A series of experiments have been conducted to visualise gas hydrate formation in CO2, methane and natural gas systems and how clathrate growth in these systems was affected by the presence of LDHIs. Initial results have proved very encouraging and demonstrated the opportunities offered by the glass micromodel set-up in attaining a better understanding of micro-scale processes during gas hydrate formation with and without inhibitors present. Micromodel tests on the natural gas system were complimented by tests in a hydrate kinetics rig, the objective being to examine up-scaling issues. These tests also provided valuable information on induction time, rate of hydrate formation and transportability of gas hydrates. The results indicate that gas hydrate formation and inhibition by LDHIs depends on the degree of subcooling, the solubility of hydrate forming gases, the chemistry of produced water and possibly the type of gas hydrate structure. A brief description of some of the experiments conducted and results are presented here. Although only preliminary, they demonstrate the potential of a combined micro-scale (glass micromodel) and macro-scale (bulk kinetic rig) experimental approach to the assessment of LDHIs.

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