Chemical composition of deposition from production well of Piltun-Astokhskoye oil field (Sakhalin-2 project) was investigated. Deposition was taken during planned well maintenance. It was found that deposition consisted of water, organic and inorganic parts. It is shown that along with carbonates and sulfates of alkaline earth metals (barium and strontium), the inorganic part contains hardly soluble magnesium silicate. In the organic part, polymer components were identified, as well as carbon and molybdenum lubricants. To identify the nature of polymers and other organic compounds insoluble in toluene (polymers and lubricants), the method of pyrolytic chromatography-mass spectrometry was used. The concentration of the polymers and their average molecular weight were determined by high performance liquid chromatography with an ultraviolet detector at a wavelength of 200 nm. Polymers with a structure similar to polyacrylic acid were identified in the deposition samples from pyrograms and total mass spectra. The dependence of the chemical composition of deposition on the depth at which they were found is shown. At great depths, the deposits are enriched in barium and strontium sulfates; with decreasing depth, calcium carbonate (calcite) begins to prevail in the deposits. The solubility of deposition in various solvents was studied; it was shown that acidic solvents well dissolve depositioт in which carbonates predominate, but do not dissolve barium and strontium sulfates, as well as molybdenum salts, which are effectively removed by a 50% solution of the Scale Cure® reagent (scale dissolver). The results obtained were used to optimize the treatment of production wells with scale dissolvers and scale inhibitors.
References
1. 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.
2. Markin A.N., Sukhoverkhov S.V., Zadorozhny P.A. et al., Measurement and calculation of polymeric scale inhibitor concentration in water, Int. J. Corros. Scale Inhib., 2018, V. 7, no. 2, pp. 250–259.
