Solubility and Inhibition Efficiency of Phosphonate Scale Inhibitor_Calcium_Magnesium Complexes for Application in a Precipitation-Squeeze Treatment
- Alsu Valiakhmetova (Heriot-Watt University) | Ken S. Sorbie (Heriot-Watt University) | Lorraine S. Boak (Heriot-Watt University) | Scott S. Shaw (Heriot-Watt University)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- August 2017
- Document Type
- Journal Paper
- 343 - 350
- 2017.Society of Petroleum Engineers
- Precipitation Squeeze Treatment, Phosphonate Scale Inhibitor, Solubility, Inhibition Efficiency
- 2 in the last 30 days
- 244 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 5.00|
|SPE Non-Member Price:||USD 35.00|
Scale-inhibitor (SI) squeeze treatments are applied extensively for controlling scale formation during oil and gas 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 behavior of the SI_ calcium (Ca)_magnesium (Mg) complexes of HEDP (a diphosphonate), DETPMP (a pentaphosphonate), and OMTHP (a hexaphosphonate); these mixed phosphonate/divalent precipitates are denoted as SI_Can1_Mgn2, where n1 and n2 are the stoichiometric ratios of Ca and Mg to SI, respectively.
Precipitation experiments with SI_Can1_Mgn2 species were carried out over a temperature range of 20 to 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 the 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 respeciation 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; this was subsequently placed into a solution with different Mg/Ca compositions (from all Ca to all Mg). In these experiments, respeciation of the precipitate may occur.
We have been able to establish the solubility (Cs) of the precipitates of three SIs (HEDP, OMTHP, and DETPMP) as a function of both temperature and Mg/Ca molar ratio. It has been shown that the solubility of precipitate is in equilibrium with Mg and Ca concentrations in solution, and any change of these parameters leads to solubility variation. All phosphonate/metal precipitates become less soluble with increasing temperature and much more soluble with an increasing proportion of Mg. We have found that any change in Mg/Ca ratio of brine does lead to a redistribution of Ca, Mg, and SI concentrations in a given precipitate and bulk solution, and, hence, leads to some variation in the precipitate solubility.
Additionally, the inhibition efficiency (IE) of precipitated and then redissolved HEDP, OMTHP, and DETPMP SIs was tested and compared with the IE of industrial stock products. We show that, unlike polymeric SI precipitates, the inhibition activity of phosphonate SIs does not depend significantly on the precipitation process, and the IE of precipitated and redissolved SI_Ca and SI_Ca_Mg complexes is very close to that of the industrial stock solutions. These results can be used directly for modeling phosphonate precipitation-squeeze treatments, and the significance of these results for field applications is explained.
|File Size||1 MB||Number of Pages||8|
Browning, F. H. and Fogler, H. S. 1995. Effect of Synthesis Parameters on the Properties of Calcium Phosphonate Precipitates. Langmuir 11 (10): 4143–4152. https://doi.org/10.1021/la00010a082.
Browning, F. H. and Fogler, H. S. 1996a. Fundamental Study of the Dissolution of Calcium Phosphonates From Porous Media. AIChE Journal 42 (10): 2883–2896. https://doi.org/10.1002/aic.690421017.
Browning, F. H. and Fogler, H. S. 1996b. Effect of Precipitating Conditions on the Formation of Calcium–HEDP Precipitates. Langmuir 12 (21): 5231–5238. https://doi.org/10.1021/la9603277.
Farooqui, N. M. and Sorbie, K. S. 2014. Oilfield Scale Inhibitors for Application in Precipitation Squeeze Treatments: Solubility of the Ca_PPCA Complex. Presented at the SPE International Oilfield Scale Conference and Exhibition, Aberdeen, 14–15 May. SPE-169792-MS. https://doi.org/10.2118/169792-MS.
Kan, A. T., Oddo, J. E., and Tomson, M. B. 1994. Formation of Two Calcium Diethylenetriaminepentakis(methylene phosphonic acid) Precipitates and Their Physical Chemical Properties. Langmuir 10 (5): 1450–1455. https://doi.org/10.1021/la00017a022.
Oddo, J. E. and Tomson, M. B. 1990. The Solubility and Stoichiometry of Calcium-diethylenetriaminepenta(methylene phosphonate) at 70°C in Brine Solutions at 4.7 and 5.0 pH. Applied Geochemistry 5 (4): 527–532. https://doi.org/10.1016/0883-2927(90)90026-2.
Pairat, R., Sumeath, C., Browning, F. H. et al. 1997. Precipitation and Dissolution of Calcium–ATMP Precipitates for the Inhibition of Scale Formation in Porous Media. Langmuir 13 (6): 1791–1798. https://doi.org/10.1021/la9608425.
Sawada, K., Miyagawa, T., Sakaguchi, T. et al. 1993. Structure and Thermodynamic Properties of Aminopoly-Phosphonate Complexes of the Alkaline-Earth Metal Ions. J. Chem. Soc., Dalton Trans. 1993 (24): 3777–3784. https://doi.org/10.1039/DT9930003777.
Shaw, S. S. 2012. Investigation Into the Mechanisms of Formation and Prevention of Barium Sulphate Oilfield Scale. PhD dissertation, Heriot-Watt University, Edinburgh, UK.
Shaw, S. S. and Sorbie, K. S. 2014. Structure, Stoichiometry, and Modelling of Calcium Phosphonate Scale-Inhibitor Complexes for Application in Precipitation-Squeeze Processes. SPE Prod & Oper 29 (2): 139–151. SPE-164051-PA. https://doi.org/10.2118/164051-PA.
Shaw, S. S. and Sorbie, K. S. 2015. Structure, Stoichiometry, and Modeling of Mixed Calcium Magnesium Phosphonate Precipitation Squeeze-Inhibitor Complexes. SPE Prod & Oper 30 (1): 6–15. SPE-169751-PA. https://doi.org/10.2118/169751-PA.
Shaw, S. S., Sorbie, K. S., and Boak, L. S. 2012a. The Effects of Barium Sulfate Saturation Ratio, Calcium, and Magnesium on the Inhibition Efficiency—Part I: Phosphonate Scale Inhibitors. SPE J. 27 (3): 306–317. SPE-130373-PA. https://doi.org/10.2118/130373-PA.
Shaw, S. S., Welton, T. D., and Sorbie, K. S. 2012b. The Relation Between Barite Inhibition by Phosphonate Scale Inhibitors and the Structures of Phosphonate-Metal Complexes. Presented at the SPE International Conference on Oilfield Scale, Aberdeen, 30–31 May. SPE-155114-MS. https://doi.org/10.2118/155114-MS.
Sorbie, K. S. 2010. A General Coupled Kinetic Adsorption/Precipitation Transport Model for Scale Inhibitor Retention in Porous Media: I. Model Formulation. Presented at the SPE International Conference on Oilfield Scale, Aberdeen, 26–27 May. SPE-130702-MS. https://doi.org/10.2118/130702-MS.
Sorbie, K. S. 2012. A SimpleModel of Precipitation Squeeze Treatments. Presented at the SPE International Conference on Oilfield Scale, Aberdeen, 30–31May. SPE-155111-MS. https://doi.org/10.2118/155111-MS.
Tantayakom, V., Fogler, H. S., and Chavadej, S. 2005. Study of Scale Inhibitor Reactions in Precipitation Squeeze Treatments. Presented at the International Symposium on Oilfield Chemistry, Houston, 2–4 February. SPE-92771-MS. https://doi.org/10.2118/92771-MS.