The recovery mechanism and application of Brevibacillus brevis and Bacillus cereus in extra-low permeability reservoir of Daqing

In view of oil and water properties and reservoirs characteristics of Chaoyanggou oilfield on the periphery of Daqing,Brevibacillus brevis and Bacillus cereus were screened as the bacterial groups of bacterial oil recovery.When the bacterium act on hydrocarbon,only long-chain paraffin hydrocarbon molecules(over C_(20)) are degraded,mainly by oxidative degradation and the metabolic product is dominated by saturated alkyl acid,with no short-chain hydrocarbon molecules being generated.The interfacial tension is decreased by about 50% and many kinds of organic acids being generated;the bacterium can selectively degrade some mid and high carbon paraffin hydrocarbons,resulting in the content of long-chain paraffin hydrocarbon being decreased and that of short-chain paraffin hydrocarbon increased,oil viscosity decreases by about 40%,the wax content and resin content decreases,and the rheological property is improved.Physical simulation of oil displacement indicates that oil recovery factor is increased by(6.7%).The pilot test in extra-low permeability oil fields has got desirable result.