A microbial enhanced oil recovery (MEOR) technique was tested at low-temperature heavy oil reservoirs (Russia). The bioaugmentation approach used is based on the introduction of hydrocarbon-oxidizing bacteria into the oilfield in combination with an injection of oxygen as a H 2 O 2 solution in order to initiate the first stage of hydrocarbon oxidation and of (NH 4 ) 2 HPO 4 as a source of biogenic elements. Before the pilot trials, the microorganisms of petroleum reservoirs were investigated by high-throughput sequencing, as well as by culture-base and radioisotope techniques. Molecular studies revealed the differences in microbial composition of the carbonate and terrigenous oil reservoirs and the communities of injection and formation water. Aerobic bacteria Rhodococcus erythropolis HO-KS22 and Gordonia amicalis 6-1 isolated from oilfields oxidized oil and produced biosurfactants. Fermentative enrichment and pure cultures produced considerable amounts of low fatty acids and alcohols from sacchariferous substrates. In core-flooding tests, 43.0-53.5% of additional heavy oil was displaced by aerobic bacteria, producing biosurfactants, and 13.4-45.5% of oil was displaced by fermentative bacteria, producing low fatty acids, alcohols, and gas. A total of 1250 t additional oil was recovered as a result of the application of an MEOR technique at the Cheremukhovskoe heavy oil reservoir and Vostochno-Anzirskoe reservoir with light conventional oil.
The results of laboratory studies of filtration processes on models of a terrigenous reservoir are presented in order to develop optimal compositions for simultaneous water and gas injection and foam assisted water alternating gas injection on the reservoir. The experiments were carried out on rock samples drilled from the core of terrigenous deposits of the Kynovsko-Pashiy horizon. The use of water-gas mixtures with foam-forming surfactants taking into account the field conditions of the fields of PJSC TATNEFT has been established will make it possible to obtain the greatest increase in oil recovery. Studies of the multiplicity and stability of foam systems have shown that non-ionic foaming surfactants TN-PO-1, TN-PO-2 and AF9-12 are best suited for use in FAWAG of the reservoir. The results of studies of the properties of foams depending on the concentration of surfactants are presented, recommendations are given on the use of specific reagents for the implementation of FAWAG, taking into account the conditions of specific fields. The use of SWAG and FAWAG technologies is not only increase oil recovery, but also significantly reduce the volume of irrationally used associated petroleum gas, which is one of the most important tasks for sustainable development goals. Keywords: enhanced oil recovery; filtration studies; simultaneous water and gas injection; foam assisted water alternating gas injection; foaming surfactants.
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