Steam injection has become a common method of extracting heavy crude oil. To mitigate environmental impact associated with disposal of large volumes of produced water in the heavy oil fields and to decrease the need in fresh water from surface sources, the Company has been using the produced water for steam generation. Currently, Tatneft PJSC operates two water treatment units, the Kamenka unit with the capacity 350 m3/h and the Karmalka unit with the capacity 700 m3/h to produce demineralized water to be used as feed water for steam generation. Membrane methods of water treatment and demineralization have been realized in the above-mentioned water treatment units. The flow scheme includes the following process units and operations: sorption-filtration unit (preliminary cleaning to remove residual oil); ultrafiltration membrane unit (removal of oil); activated carbon sorption filters (further removal of dissolved oil and organic matter); reverse osmosis membranes – two stages (demineralization of water); anionic filters (removal of hydrosulfides); hydrogen peroxide dosing unit (complete removal of sulfide ions). TatNIPIneft R&D Institute has performed extensive studies to develop an efficient technology of preliminary cleaning of produced water in the sorption-filtration unit; also, TatNIPIneft research engineers have carried out studies on hydrogen peroxide dosing into demineralized water to neutralize residual sulfide ions, and have designed an automatic hydrogen peroxide dosing unit. The performed pilot tests allowed to select the most efficient agents for chemical washing of the reverse osmosis membranes. Successful operation of the first-in-Russia water treatment units based on the membrane methods has demonstrated that water meets the requirement to feed water for water-tube units for steam generation.
References
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