Water – inseparable companion of oil and gas. In the field, it lies in the same layers as oil or gas deposits, as well at the actual aquifers (horizons). At the development of field water can be injected in an oil or gas reservoir by moving at oil-well or enter the field from other aquifers.
Waterflooding of oil reservoirs – the main method to extract oil from oil reservoirs. The composition and properties of produced water are of great importance for the development and mining of oil and gas, many processes in the drained reservoir depends on them. Oilfields produced waters are usually complex multicomponent systems comprising: anions ОН—, Сl—, SO32-, СО32-, НСО3— ; cations H+, Na+, NH4+, Ca2+ and others; microelements I and Br; colloidal particles of SiO2, Fe2O3, Al2O3; dissolved gases: СО2, Н2S, СН4, Н2, N2 etc.; naphthenic acids and their salts. Quantitative relationships between the content of ions in water determine the type of produced waters and oilfield wastewaters.
Operation experience of petroleum deposits shows that waterflooding of oil reservoirs in some cases accompanied by the appearance of hydrogen sulfide in the reservoir, which previously was absent. It happens due to the activity of sulfate-reducing bacteria (SRB), which reduce water sulfates to hydrogen sulfide. SRB activity in the oil fields operation leads to the following complications:
- production of hydrogen sulfide in oilwell gas (up to 16 g per 100 m3 of gas);
- loss of water sulfate ions, enrichment of water with acid gases – hydrogen sulfide and carbon dioxide;
- enhancement of chemical and electrochemical corrosion of metal (presence of 0.000002 – 0.000004 kg of hydrogen sulfide per 1 l of water increase 3 – 5 times the rate of metal corrosion).
Catalytic oxidation with oxygen of hydrogen sulfide and sulfides is the most appropriate (from an economic and environmental point of view) method of produced water treatment. According to this, at STC «AhmadullinS – Science and Technology” was developed method of heterogeneous catalytic liquid phase oxidation of dissolved in water hydrogen sulfide and sulfides to sulfate and thiosulfate. Catalytic oxidative treatment of sulfide containing wastes does not cause air pollution with emissions of hydrogen sulfide and sulfur dioxide. This method does not require continuous consumption of reactants (carbon dioxide and sulfuric acid) and heat. It provides more complete removal of toxic malodorous sulfur compounds from wastewater: hydrogen sulfide, sodium sulfide and hydrosulfide. Neutral medium of the reaction and relatively low process temperature allow using carbon steels apparatus in a scheme.