The Effects of Barium Sulfate Saturation Ratio, Calcium, and Magnesium on the Inhibition Efficiency--Part I: Phosphonate Scale Inhibitors
- Scott S. Shaw (Heriot-Watt University) | Ken Sorbie (Heriot-Watt University) | Lorraine S. Boak (Heriot-Watt University)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- August 2012
- Document Type
- Journal Paper
- 306 - 317
- 2012. Society of Petroleum Engineers
- 4.3.4 Scale, 5.2 Reservoir Fluid Dynamics, 4.2.3 Materials and Corrosion
- 2 in the last 30 days
- 518 since 2007
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Conventional phosphonate-type scale inhibitors (SIs) are commonly applied for barite-scale prevention in oil fields. The barite forms when the injection water (IW), which is usually sulfate rich, is injected into a barium-containing formation water (FW). The inhibition efficiency (IE) of barite-scale inhibitors is affected by the barium sulfate saturation ratio (SR) of the brine mix and, additionally, by the presence of divalent cations Ca2+ and Mg2+. What is less well known is that the precise balance between these factors (SR and Ca2+/Mg2+ ratio) can vary significantly for different phosphonate species. This paper presents novel IE experimental results for phosphonate-scale inhibitors DETPMP and HMTPMP (penta-phosphonates), OMTHP (hexa-phosphonate), and HMDP (tetra-phosphonate). Minimum-inhibitor-concentration (MIC) levels for each SI are established by testing a wide range of brine IW/FW mixing ratios, which changes (i) barite SR and precipitated mass, (ii) molar ratio of Ca2+/Mg2+, and (iii) the ionic strength of the brine mix.
The phosphonate SIs were categorized into two types on the basis of their MIC-vs.-percent-North Sea-seawater (NSSW) behavior. Type 1 (e.g. DETPMP and OMTHP) are affected principally by SR and are rather less sensitive to Ca2+/Mg2+ ratio although they do show some sensitivity to the latter factor. Type 2 (e.g., HMTPMP and HMDP) are severely affected by brine Ca2+/Mg2+ ratio as well as SR. To demonstrate these effects conclusively, a series of IE experiments is presented with varying [Ca2+] and [Mg2+] (which normally occurs in the field as the IW/FW ratio changes over time) and then similar experiments are repeated at a fixed Ca2+/Mg2+ molar ratio. The MIC level measured for both types of phosphonate SI always correlates very well with the barite SR at fixed Ca2+/Mg2+ molar ratio (fixed case). In addition, we find the MICs of both types of SI are much lower in the fixed-case experiments (higher Ca2+/Mg2+ molar ratio), compared with the base case, because of the beneficial effect of higher [Ca2+]. The effects observed are important for field application of phosphonate SIs because they show how the various species are sensitive to the changing scaling problems as the %NSSW increases, in terms of SR and Ca2+/Mg2+ molar ratio. These results also give some important insights into the mechanism by which different phosphonates actually work in inhibiting barite scale.
|File Size||7 MB||Number of Pages||12|
Boak, L.S. and Sorbie, K.S. 2010. New Developments on the Analysis of ScaleInhibitors. Paper SPE 130401 presented at the SPE International Conference onOilfield Scale, Aberdeen, 26-27 May. http://dx.doi.org/10.2118/130401-MS.
Boak, L.S., Graham, G.M., and Sorbie, K.S. 1999. The Influence ofDivalent Cations on the Performance of BaSO4 Scale Inhibitor Species. Paper SPE50771 presented at the SPE International Symposium on Oilfield Chemistry,Houston, 16-19 February. http://dx.doi.org/10.2118/50771-MS.
Boak, L.S., Graham, G.M., and Sorbie, K.S. 2003. The Influence ofFormation Calcium and Magnesium on the Effectiveness of Generically DifferentBarium Sulphate Oilfield Scale Inhibitors. SPE Prod & Fac 18 (1): 28-44. SPE-81825-PA. http://dx.doi.org/10.2118/81825-PA.
Duan, W., Satoh, K., and Sawada, K. 2001. Stability and Structure ofEthylenedinitrilopoly(methylphosphonate) Complexes of the Divalent TransitionMetal Ions in Aqueous Solution. Bull. Chem. Soc. Jpn. 74(3): 487-493.
Gill, J.S. and Varsanik, R.G. 1986. Computer modeling of the specificmatching between scale inhibitors and crystal structure of scale formingminerals. J. Cryst. Growth 76 (1): 57-62. http://dx.doi.org/10.1016/0022-0248(86)90008-4.
Graham, G.M., Boak, L.S., and Sorbie, K.S. 1997. The Influence ofFormation Calcium on the Effectiveness of Generically Different Barium SulphateOilfield Scale Inhibitors. Paper SPE 37273 presented at the InternationalSymposium on Oilfield Chemistry, Houston, 18-21 February. http://dx.doi.org/10.2118/37273-MS.
Kan, A.T., Fu, G., Shen, D., Al-Saiari, H., and Tomson, M.B. 2008.Enhanced inhibitor treatments with the addition of transition metal ions. PaperSPE 114060 presented at the SPE International Oilfield Scale Conference,Aberdeen, 28-29 May. http://dx.doi.org/10.2118/114060-MS.
Popov, K., Rönkkömäki, H., and Lajunen, L.H. 2001. Critical evaluationof stability constants of phosphonic acids. Pure Appl. Chem. 73 (10): 1641-1677. http://dx.doi.org/10.1351/pac200173101641.
Sánchez-Moreno, M.J., Fernández-Botello, A., Gómez-Coca, R.B., et al. 2004.Metal Ion-Binding Properties of (1H-Benzimidazol-2-yl-methyl)phosphonate(Bimp2-) in Aqueous Solution. Isomeric Equilibria, Extent of Chelation,and a New Quantification Method for the Chelate Effect. Inorg. Chem. 43 (4): 1311-1322.
Sawada, K., Miyagawa, T., Sakaguchi, T., and Doi, K. 1993. Structureand thermodynamic properties of aminopoly-phosphonate complexes of thealkaline-earth metal lons. J. Chem. Soc., Dalton Trans. (24): 3777-3784.http://dx.doi.org/10.1039/DT9930003777.
Shaw, S.S., Sorbie, K.S., and Boak, L.S. 2010. The Effects of BariumSulphate Saturation Ratio, Calcium and Magnesium on the Inhibition Efficiency:II Polymeric Scale Inhibitors. Paper SPE 130374 presented at the SPEInternational Conference on Oilfield Scale, Aberdeen, 26-27 May. http://dx.doi.org/10.2118/130374-MS.
Sorbie, K.S. and Laing, N. 2004. How Scale Inhibitors Work: Mechanisms ofSelected Barium Sulphate Scale Inhibitors Across a Wide Temperature Range.Paper SPE 87470 presented at the SPE International Symposium on Oilfield Scale,Aberdeen, 26-27 May. http://dx.doi.org/10.2118/87470-MS.
Sorbie, K.S., Graham, G.M., and Jordan, M.M. 2000. How scaleinhibitors work and how this affects test methodology. Paper OFC-1 presented atthe 4th International Conference and Exhibition on Chemistry in Industry,Manama, Bahrain, 30 October-1 November.