Important criterion for correct selection of scale inhibition protection and methods for treatment of oil equipment is chemical composition of formation water and mineral deposits. The aim of this paper was to study a composition of produced and sea waters as well as deposits drawn fr om various technological points of the oil-producing equipment. The samples were taken from platform MOLIQPAK of the Astokhskoye area of Piltun-Astokhskoye oilfield located on the northeast part of shelf of Sakhalin Island. Samples were analyzed with various physical and chemical methods including IC HPLC, GLC and X-ray fluorescence spectrometry. Produced waters of the studied oilfield have typical composition for oilfield waters. Total mineralization of studied water samples was 28 g/l in average Major dissolved components of the salt matrix are sodium and potassium chlorides. Concentration of sulfate-ions for different wells varied within 200-1900 mg/l, alkalinity (as HCO3-) - 450-870 mg/l. Acetic acid was major component among volatile fatty acids. Units of equipment wh ere the concentration of carboxylic acids was highest contained iron sulfide in the sediment. It may indicate to occurrence of sulfate reduction processes. According to Sulin’s classification formation waters belong to types: sulfate-sodium, chloride-calcium, hydro carbonate-sodium, to groups - chlorides and hydrocarbonate, to subgroups - calcium and magnesium.
Inorganic part of the studied deposits consists of sand, clay, insoluble sulfates and carbonates of alkaline-earth metals, corrosion products of pipes and equipment (compounds of Fe and salts of transition metals - Cr, Mo, Zr, etc.). Comparison of water and deposit composition gives information on deposit formation at different technological parts of oil-producing equipment, allows creating chemical models for studying of mechanisms of formation and removal of salt deposits.
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