Determination of Low Concentrations of Phosphonate in Brines (1991)

Determination of Low Concentrations of Phosphonate in Brines A.T. Kan; A.T. Kan Rice U. Search for other works by this author on: This Site Google Scholar K. Varughese; K. Varughese Al-Qahtani Pipe Coating Terminal Search for other works by this author on: This Site Google Scholar M.B. Tomson M.B. Tomson Rice U. Search for other works by this author on: This Site Google Scholar Paper presented at the SPE International Symposium on Oilfield Chemistry, Anaheim, California, February 1991. Paper Number: SPE-21006-MS https://doi.org/10.2118/21006-MS Published: February 20 1991 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Kan, A.T., Varughese, K., and M.B. Tomson. "Determination of Low Concentrations of Phosphonate in Brines." Paper presented at the SPE International Symposium on Oilfield Chemistry, Anaheim, California, February 1991. doi: https://doi.org/10.2118/21006-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Conference on Oilfield Chemistry Search Advanced Search AbstractPhosphonates are widely used as scale and corrosion Phosphonates are widely used as scale and corrosion inhibitors in the industrial environment, but methods of measurement especially at low concentration levels are subject to numerous interferences. The process described herein consists of a digestion step to break-down the phosphonate materials to orthophosphate. The phosphonate materials to orthophosphate. The orthophosphate material is extracted into a novel organic phase and measured. The process of extraction eliminates the phase and measured. The process of extraction eliminates the common interferences to the orthophosphate measurement and allows the accurate determination of phosphonate materials at low levels. The method is suited for measuring phosphonate concentration between 0.1 to 10 mg/l in brine phosphonate concentration between 0.1 to 10 mg/l in brine with a reproducibility of + 5% at normal concentration. In two hours as many as 20 phosphonate samples can be analyzed by one person using this technique.IntroductionPhosphonates are widely used as scale and corrosion Phosphonates are widely used as scale and corrosion inhibitors in gas and oil wells which co-produce large volumes of brine. Recently, it was shown that as low as 0.16 mg/I of phosphonate can effectively prevent scale formation in the field. Often the decision to re-treat a well is based upon the ability to measure inhibitor concentrations and not upon performance criteria. The cost for chemicals may be small, but the operational cost and the loss in production during repeated shut-ins can be significant.Analytical methods to measure the concentration of phosphonates in brine include: 1) use of radio-labelled phosphonates in brine include:use of radio-labelled carbon or phosphorous;complexation with copper, thorium, iron, or magnesium;inductively coupled plasma (ICP) arc mass spectrometry (MS);high performance ion chromatography with or without ion suppression; andoxidation of the phosphonate to phosphate and colorimetric measurement of the increased phosphate concentration.The ICP/MS and ion chromatography methods, in addition to requiring sophisticated instrumentation, are still in the developmental stages, and the radio-labelled methods are not generally useable in the field due to problems both with permitting and availability. The colorimetric methods are permitting and availability. The colorimetric methods are easy to perform, but are susceptible to numerous interferences. The analytical method most commonly used today for measurement of phosphonate concentration was developed at Hach Chemical Companies in 1972. In this method, hereinafter referred to as the "Hach method," phosphonates are oxidized to phosphate by UV/persulfate, phosphonates are oxidized to phosphate by UV/persulfate, and the Increased phosphate concentration is measured as the classical phosphomolybdate blue complex. That method yields excellent results in twenty to thirty minutes for phosphonate concentrations above 0.02 mg/l in fresh water. phosphonate concentrations above 0.02 mg/l in fresh water. However, the interferences from trace species such as calcium, barium, strontium, sulfate, sulfide, silicate and turbidity as well as major ion interferences due to chloride etc., render the method unsuitable for measuring the phosphonate in brine solutions below about 5 mg/l. phosphonate in brine solutions below about 5 mg/l. Therefore, when the measured phosphonate concentration drops below about 1.0 to 5.0 mg/l, it is commonly recommended to re-squeeze or treat the well before scale begins to develop.If the drop in phosphonate concentration over time were linear, such a treatment schedule would be reasonably efficient. In fact, inhibitor concentration initially drops to around 1 mg/l or below and then levels off at a steady state value from 0.1 to 1.0 mg/1. The precise steady state concentration depends upon the specific brine, the formation type, and the inhibitor chemistry. Although this 0.1 to 1.0 mg/l concentration range may be too small for corrosion control, it is generally adequate for scale control in the production tubing. production tubing. This discussion describes a simple method for the accurate and reliable determination of phosphonate concentrations above about 0.05 mg/1. Both the incomplete UV/persulfate oxidation and the color development interferences were problems associated with the Hach method. problems associated with the Hach method. P. 109 Keywords: asphaltene inhibition, production chemistry, phosphonate, acid, wax remediation, oilfield chemistry, wax inhibition, absorbance, scale inhibition, upstream oil & gas Subjects: Production Chemistry, Metallurgy and Biology, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene This content is only available via PDF. 1991. Society of Petroleum Engineers You can access this article if you purchase or spend a download.