Solubility and inhibition efficiency of phosphonate scale inhibitor_calcium_magnesium complexes for application in precipitation squeeze treatment

Alsu Valiakhmetova, Kenneth Stuart Sorbie, Lorraine Scott Boak, Scott Shaw

Research output: Chapter in Book/Report/Conference proceedingConference contribution

8 Citations (Scopus)


Scale inhibitor (SI) squeeze treatments are applied extensively for controlling scale formation during oil production. The current research involves phosphonate/metal precipitate studies in the context of precipitation squeeze treatments. The main focus here is on the precipitation and solubility behaviour of the SI-Ca-Mg complexes of HEDP (di-phosphonate), DETPMP (penta-phosphonate) and OMTHP (hexaphosphonate) phosphonate Sis; these phosphonate/mixed Ca/Mg divalent precipitates are denoted as SI-Can1-Mgn2, where n1 and n2 are the stoichiometric ratios of Ca and Mg to SI. Precipitation experiments with SI-Can1-Mgn2 species were carried out over the temperature range, 20-95°C, while varying the Mg/Ca molar ratio over a wide range from all Ca to all Mg. These precipitates were formed in MgCl2·6H2O/CaCl2·6H2O brine solutions with appropriate molar ratios of metals, then separated from supernatant by filtration. Subsequently, the solubility of the collected precipitate was found in a solution of the same Mg/Ca molar composition from which it was prepared. In this type of experiment, the solubility of the SI-Can1-Mgn2 precipitate without any re-speciation is determined. In addition, another type of solubility experiment was carried out for a precipitate formed in a brine with one fixed Mg/Ca ratio and this was subsequently placed into a solution with different Mg/Ca compositions (from all Ca to all Mg). In these experiments, re-speciation of the precipitate may occur. We have been able to establish the solubility (Cs) of the precipitates of 3 SIs (HEDP, OMTHP and DETPMP) as a function of both temperature and Mg/Ca molar ratio. It has been shown, that the solubility (Cs) of precipitate is in equilibrium with Mg and Ca concentrations in solution and any change of these parameters leads to solubility (Cs) variation. All phosphonate/metal precipitates become less soluble with increasing temperature and much more soluble as the proportion of Mg increases. We have found, that any change in Mg/Ca ratio of brine does lead to a re-distribution of Ca, Mg and SI concentrations in a given precipitate and bulk solution, and hence leads to some variation in the precipitate solubility. In addition, the inhibition efficiency (IE) of precipitated and then re-dissolved HEDP, OMTHP and DETPMP SIs was tested and was compared with the IE of industrial stock products. We show that, unlike polymeric SI precipitates, the inhibition activity of phosphonate SIs does not depend very significantly on the precipitation process and the IE of precipitated and re-dissolved SI-Ca and SI-Ca-Mg complex is very close to that of the industrial stock solutions. These results can be used directly for modelling phosphonates precipitation squeeze treatments and the significance of these results for field applications is explained.

Original languageEnglish
Title of host publicationSPE International Conference and Exhibition on Formation Damage Control, 24-26 February, Lafayette, Louisiana, USA
PublisherSociety of Petroleum Engineers
ISBN (Print)9781613994412
Publication statusPublished - 2016
EventSPE International Conference and Exhibition on Formation Damage Control 2016 - Lafayette, United States
Duration: 24 Feb 201626 Feb 2016


ConferenceSPE International Conference and Exhibition on Formation Damage Control 2016
Country/TerritoryUnited States

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Geotechnical Engineering and Engineering Geology


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