The Research Of Denitrifying Bacteria Inhibiting Sulfate-reducing Bacteria For Enhanced Oil Recovery Technology

Most of the reservoir and oil/gas extraction system containing hydrogen sulfide (H2S) are due to the role of sulfate-reducing bacteria (sulfate reducing bacteria, referred to as SRB). SRB and hydrogen sulfide is caused by the high cost of reservoir development and operations of the main reasons, including the reservoirs sour sulfide corrosion of iron sulfide formation plugging, lower production and health, safety and environmental hazards. Biogenic sulfide problem is particularly acute in the international oil industry, and it has caused serious economic losses. Not only increased the microbial induced corrosion (MIC) and the related costs, but also the biogenic sulfide brought serious harm to human health and the environment. These harmful effects include:(1) accelerated corrosion and equipment damage;(2) increase in the renewal of equipment costs;(3) increase the cost to buy fungicides;(4) Due to the blockage of iron sulfide to reduce production and income;(5) to reduce oil and gas productsvalue;(6) pollution of the environment and harmful to human beings.Inhibiting the breeding of SRB in the injection water, and reducing the corrosion rate in order to enhance oil recovery, that should be the urgent problem in the oil field reinjection water treatment session. At present, oilfield commonly used chemical fungicides to control the harm caused by SRB, it have achieved remarkable results. However, long-term use of chemical fungicides make bacterial resistance, increase the amount of reagent, increased costs, and bring pollution load to environment. In recent years, the biological suppression methods take more and more researchers’ attention.The pilot study found that when the denitrifying bacteria (Denitrifying Bacteria, hereinafter referred to as DNB) exist, can effectively inhibit the growth of SRB, and greatly improve the corrosion of equipment. This phenomenon is known as bio-competitive exclusion (Exclusion Biocompetitive, hereinafter referred to as BCX) role, the mechanism is that the survival environment and living habits of the denitrifying bacteria (DNB) and SRB are similar, when the system contains a certain amount of nitrate or nitritewill, it will stimulate the growth and reproduction of DNB, the restore role of SRB is substituted by the denitrification of DNB, so as to achieve the purpose of the inhibition of SRB activity. The microbial enhanced oil recovery (Microorganism Enhances Oil Recovery, hereinafter referred to as MEOR) technology is injected the particular microorganisms screened or their metabolites that suit the stratigraphic environment into the reservoir, through the metabolic activity of microorganisms, the oil in the long chain saturatedhydrocarbon is decomposed into short-chain olefins, resulting in the enzymes of degrading heavy hydrocarbons and paraffin produce methane, surface active substances and other chemicals to change the performance of the strata and crude oil, then enhanced oil recovery. This study is the organic combination of BCX and MEOR, on the one hand, SRB is controled, on the other hand, to achieve the purpose of microbial enhanced oil recovery.This issue investigate the relative level between the denitrification capacity of the native DNB and the sulfate reduction capacity of the SRB in oilfield ground system through researching Changqing Oilfield and Xinjiang Oilfield existing information. Then determine the operating conditions for denitrification inhibiting sulfate reduction.The sulfate-reducing bacterial strain isolated from Changqing Oilfield produced water, the strain G+, short rod-shaped, motile, with sulfate-reducing function, production of H2S, strictly anaerobic; change the substrate (addition of nitrate)denitrifying bacteria in a lot of breeding, and competition of the substrate, sulfate-reducing bacteria lose or change its function, resulting in biological activity, thereby inhibiting the growth of sulfate-reducing bacteria, biological denitrification inhibition.The Xinjiang Oilfield Production Plant Hongshanzui18blocks is the polymer flooding pilot well area.The polymer crosslinking agent can not gelling and play role of flooding for the gaint amount of SRB.In August2011to November, this kind of technology applied to this blocks.DNB agents and its activator added to the polymer gelling well make the SRB to be inhibited, the production was increased of each well group.