The effect of molecular weight on the adsorption/desorption characteristics of polymeric scale inhibitors on silica sand and in sandstone cores
Book
·
OSTI ID:70048
- Heriot-Watt Univ., Edinburgh (United Kingdom). Dept. of Petroleum Engineering
A number of polymeric scale inhibitors are currently used for downhole application in oilfield ``squeeze`` treatments. These materials must perform the dual role of inhibiting scale formation at low concentration levels whilst giving acceptably long return curves at the wellbore. Both of these design aspects of polymeric scale inhibitors relate to their adsorption characteristics (either on the growing scale crystal or onto the rock substrate) which, in turn, are functions of the molecular weight of the species. In this paper, the authors examine the effects of inhibitor molecular weight on its adsorption characteristics onto highly quartzitic substrates and they discuss the importance of this factor in governing the dynamics of the inhibitor return curve. The effects of molecular weight on the inhibition efficiency, during both early nucleation and later crystal growth, are also examined. The adsorption/desorption characteristics of three polymeric scale inhibitors, each having a range of molecular weights, are studied in this work: viz. polyacrylate (PAA) and phosphinopolycarboxylate (PPCA) scale inhibitors of weight average molecular weight, M{sub w} < 10,000 g/mol, and polyvinyl sulphonic acid (PVS) inhibitors of M{sub w} < 20,000 g/mol. Using these polymers, the authors show that the preferential adsorption of the higher molecular weight components occurs. Results on the scale inhibition efficiency of barium sulphate, obtained for the same range of polymeric inhibitors, are also presented as functions of molecular weight. The factors required to ensure a long return curve are not necessarily the same as those for efficient inhibition under certain solution conditions (e.g. solution pH). This illustrates the importance of reaching a compromise in terms of molecular weight between inhibition efficiency and squeeze lifetime. The significance of these findings for field squeeze treatments using polymeric inhibitors is discussed. 43 refs.
- OSTI ID:
- 70048
- Report Number(s):
- CONF-940222--
- Country of Publication:
- United States
- Language:
- English
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