Study of the formation of carbonate scale in oilfield equipment of the Piltun-Astokhskoye field (Sakhalin Island)

UDK: 66.08+54.061
DOI: 10.24887/0028-2448-2019-4-90-93
Key words: carbonates, dolomite, magnesian calcite, formation water, X-ray spectral analysis
Authors: A.N. Markin (Institute of Chemistry, the Far Eastern Branch of RAS, RF, Vladivostok; Tyumen Industrial University, RF, Tyumen), I.S. Trukhin (Institute of Chemistry, the Far Eastern Branch of RAS, RF, Vladivostok), N.V. Polyakova (Institute of Chemistry, the Far Eastern Branch of RAS, RF, Vladivostok), P.A. Zadorozhny (Institute of Chemistry, the Far Eastern Branch of RAS, RF, Vladivostok), S.V. Sukhoverkhov (Institute of Chemistry, the Far Eastern Branch of RAS, RF, Vladivostok)

Co-precipitation of calcium and magnesium carbonates is possible in real oilfield systems. Due to co-precipitation, the amount of salts formed may differ significantly from the amount calculated using saturation indexes for the various carbonates individually. Magnesium, along with calcium, is in the overwhelming majority of cases in the reservoir and in produced water, and its presence may have an effect on the calcite formation. The aim of the work was to study scale formation processes on the basis of experiments with synthetic and real samples of the produced water of the Piltun-Astokhskoye oilfield to confirm the possibility of formation of mixed calcium and magnesium carbonates. The composition of scale from oilfield equipment and sediments formed in laboratory experiments was determined by X-ray spectral analysis. To study the scale formation synthetic brines of Piltun-Astokhskoye field produced water were prepared with the following composition (ppm): Na+ – 8140, K+ – 170,

Ca2+ – 470, Mg2+ – 140, Cl- – 13000, HCO3- – 1500, SO42- – 730. The precipitation of mixed Ca and Mg carbonates was also studied on samples of real produced water from the PA-A platform and mixtures of produced and sea water. According to X-ray spectral analysis, the composition of scale from oilfield equipment is more complex than the composition of sediments formed from synthetic brines in laboratory experiments. On the diffractograms of sediments formed from synthetic brines in laboratory experiments, in addition to calcium carbonate, there are signals of mixed calcium and magnesium carbonates (magnesian calcite), with different stoichiometric ratios of these metals, with a significant predominance of the former. The formation of dolomite was not observed in the laboratory experiments. It was shown earlier that the amount of magnesium in the scale from oilfield equipment can reach 6.6%wt. in terms of MgCO3. The magnesian calcite found in the scale has several stoichiometric Ca / Mg ratios, so it is difficult to predict its precipitation. Since in real scales magnesium can be present both in the form of magnesian calcite and in the form of dolomite, the magnesium deposition forecast should be made for the dolomite, for which the thermodynamic characteristics are known, and it is possible to calculate the saturation index.

The results obtained indicate that the formation of magnesium carbonate should be taken into consideration when predicting scale precipitation in oilfield systems.

References

1. Vazquez O., Fursov I., Mackay E., Automatic optimization of oil field scale inhibitor squeeze treatment designs, J. Pet. Sci. Eng., 2016, V. 147, pp. 302–307.

2. Sydykov Zh.D., Sambaeva D.A., Tolokonnikova L.I., Maymekov Z.K., The formation of aragonite and calcite in the system Ca(OH)2-H2O-CO2 - air with different salinity of the solution (In Russ.), Nauka, novye tekhnologii i innovatsii, 2008, no. 3–4, pp. 220–224.

3. Markin A.N., Nizamov R.E., Sukhoverkhov S.V., Neftepromyslovaya khimiya: prakticheskoe rukovodstvo (Oilfield chemistry: a practical guide), Vladivostok: Dal'nauka Publ., 2011, 294 p.

4. Matusevich L.N., Kristallizatsiya iz rastvorov v khimicheskoy promyshlennosti (Crystallization from solutions in the chemical industry), Moscow: Khimiya Publ., 1968, 304 p.

5. Reeder R.J., Carbonates: mineralogy and chemistry, Berlin: De Gruyter Publ., 1983, 394 p.

6. Chen T., Neville A., Yuan M., Assessing the effect of Mg2+ on CaCO3 scale formation-bulk precipitation and surface deposition, Journal of Crystal Growth, 2004, V. 275, pp. 1341–1347.

7. Polyakova N.V., Zadorozhnyy P.A., Trukhin I.S. et al., Determination of the chemical composition of formation and sea waters, inorganic deposits sampled at oilfield platform MOLIQPAK (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2018, no. 4, pp. 43–47.

8. Polyakova N.V., Zadorozhnyy P.A., Trukhin I.S. et al., Modeling of scaling in oilfield equipment of the Piltun-Astokhskaya-A platform (In Russ.), Vestnik DVO RAN = Bulletin of the Far East Branch of the Russian Academy of Sciences, 2017, no. 6, pp. 98–105.

9. Modeling of scaling in the system of maintaining reservoir pressure on the Piltun-Astokhskaya-A platform (“Sakhalin-2” project) (In Russ.), Vestnik Dal'nevostochnogo otdeleniya Rossiyskoy akademii nauk = Bulletin of the Far East Branch of the Russian Academy of Sciences, 2017, no. 6, pp. 106–112.

10. Polyakova N.V., Trukhin I.S., Zadorozhnyy P.A. et al., Comparison of Physicochemical model and real composition of scales in oilfield equipment units of the Platform “A-B” (In Russ.), Tekhnologii nefti i gaza, 2017, no. 3, pp. 26–32.

11. Frigo D.M., SIEP 99-5679. Scaling manual: inhibition of oilfield scales. – Hague: Shell International Exploration and Production B.V., 1999, 53 p.

12. Patton C.C., Applied water technology, Oklahoma: Campbell petroleum series, 1991, 369 p.

13. Tishchenko P.Ya., Svininnikov A.I., Pavlova G.Yu. et al., Dolomite formation in the Sea of Japantc "Dolomite formation in the Sea of Japan" (In Russ.), Tikhookeanskaya geologiya, 2001, no. 5, pp. 84–92.

Co-precipitation of calcium and magnesium carbonates is possible in real oilfield systems. Due to co-precipitation, the amount of salts formed may differ significantly from the amount calculated using saturation indexes for the various carbonates individually. Magnesium, along with calcium, is in the overwhelming majority of cases in the reservoir and in produced water, and its presence may have an effect on the calcite formation. The aim of the work was to study scale formation processes on the basis of experiments with synthetic and real samples of the produced water of the Piltun-Astokhskoye oilfield to confirm the possibility of formation of mixed calcium and magnesium carbonates. The composition of scale from oilfield equipment and sediments formed in laboratory experiments was determined by X-ray spectral analysis. To study the scale formation synthetic brines of Piltun-Astokhskoye field produced water were prepared with the following composition (ppm): Na+ – 8140, K+ – 170,

Ca2+ – 470, Mg2+ – 140, Cl- – 13000, HCO3- – 1500, SO42- – 730. The precipitation of mixed Ca and Mg carbonates was also studied on samples of real produced water from the PA-A platform and mixtures of produced and sea water. According to X-ray spectral analysis, the composition of scale from oilfield equipment is more complex than the composition of sediments formed from synthetic brines in laboratory experiments. On the diffractograms of sediments formed from synthetic brines in laboratory experiments, in addition to calcium carbonate, there are signals of mixed calcium and magnesium carbonates (magnesian calcite), with different stoichiometric ratios of these metals, with a significant predominance of the former. The formation of dolomite was not observed in the laboratory experiments. It was shown earlier that the amount of magnesium in the scale from oilfield equipment can reach 6.6%wt. in terms of MgCO3. The magnesian calcite found in the scale has several stoichiometric Ca / Mg ratios, so it is difficult to predict its precipitation. Since in real scales magnesium can be present both in the form of magnesian calcite and in the form of dolomite, the magnesium deposition forecast should be made for the dolomite, for which the thermodynamic characteristics are known, and it is possible to calculate the saturation index.

The results obtained indicate that the formation of magnesium carbonate should be taken into consideration when predicting scale precipitation in oilfield systems.

References

1. Vazquez O., Fursov I., Mackay E., Automatic optimization of oil field scale inhibitor squeeze treatment designs, J. Pet. Sci. Eng., 2016, V. 147, pp. 302–307.

2. Sydykov Zh.D., Sambaeva D.A., Tolokonnikova L.I., Maymekov Z.K., The formation of aragonite and calcite in the system Ca(OH)2-H2O-CO2 - air with different salinity of the solution (In Russ.), Nauka, novye tekhnologii i innovatsii, 2008, no. 3–4, pp. 220–224.

3. Markin A.N., Nizamov R.E., Sukhoverkhov S.V., Neftepromyslovaya khimiya: prakticheskoe rukovodstvo (Oilfield chemistry: a practical guide), Vladivostok: Dal'nauka Publ., 2011, 294 p.

4. Matusevich L.N., Kristallizatsiya iz rastvorov v khimicheskoy promyshlennosti (Crystallization from solutions in the chemical industry), Moscow: Khimiya Publ., 1968, 304 p.

5. Reeder R.J., Carbonates: mineralogy and chemistry, Berlin: De Gruyter Publ., 1983, 394 p.

6. Chen T., Neville A., Yuan M., Assessing the effect of Mg2+ on CaCO3 scale formation-bulk precipitation and surface deposition, Journal of Crystal Growth, 2004, V. 275, pp. 1341–1347.

7. Polyakova N.V., Zadorozhnyy P.A., Trukhin I.S. et al., Determination of the chemical composition of formation and sea waters, inorganic deposits sampled at oilfield platform MOLIQPAK (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2018, no. 4, pp. 43–47.

8. Polyakova N.V., Zadorozhnyy P.A., Trukhin I.S. et al., Modeling of scaling in oilfield equipment of the Piltun-Astokhskaya-A platform (In Russ.), Vestnik DVO RAN = Bulletin of the Far East Branch of the Russian Academy of Sciences, 2017, no. 6, pp. 98–105.

9. Modeling of scaling in the system of maintaining reservoir pressure on the Piltun-Astokhskaya-A platform (“Sakhalin-2” project) (In Russ.), Vestnik Dal'nevostochnogo otdeleniya Rossiyskoy akademii nauk = Bulletin of the Far East Branch of the Russian Academy of Sciences, 2017, no. 6, pp. 106–112.

10. Polyakova N.V., Trukhin I.S., Zadorozhnyy P.A. et al., Comparison of Physicochemical model and real composition of scales in oilfield equipment units of the Platform “A-B” (In Russ.), Tekhnologii nefti i gaza, 2017, no. 3, pp. 26–32.

11. Frigo D.M., SIEP 99-5679. Scaling manual: inhibition of oilfield scales. – Hague: Shell International Exploration and Production B.V., 1999, 53 p.

12. Patton C.C., Applied water technology, Oklahoma: Campbell petroleum series, 1991, 369 p.

13. Tishchenko P.Ya., Svininnikov A.I., Pavlova G.Yu. et al., Dolomite formation in the Sea of Japantc "Dolomite formation in the Sea of Japan" (In Russ.), Tikhookeanskaya geologiya, 2001, no. 5, pp. 84–92.


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