The Mechanism and Application of MEOR by Brevibacillus Brevis and Bacillus Cereusin Daqing Oilfield

摘要

The mechanism of petroleum hydrocarbonrndegradation by the selected bacteria Brevibacillus brevisrnand Bacillus cereus is studied based on the metaboliternanalysis. The result shows that bio-oxidation processes,rnespecially those called unconventional subterminalrnoxidation, terminal and double-terminal oxidation, are thernmain pathway by which the bacteria will convert petroleumrnhydrocarbons into fatty monoacids, hydroxyl fatty acidsrnand dicarboxylic acids. This, for the first time, makes anrnimportant correction to the prevailing opinion which saysrnthat long-chain hydrocarbon molecules can be degradedrninto short-chain hydrocarbon molecules instead of acidrncompounds. The study explains how the bacteria ingestrnpetroleum hydrocarbons as well as the correlationrnbetween ingestion modes and the active substancesrnpresent in crude oil. The pathway to produce biosurfactantsrnand the correlation between produced biosurfactantsrnand oil metabolism are also discussed in thisrnpaper.rnFrom 2002 to 2004, Brevibacillus brevis and Bacillusrncereus were applied in the microbial huff and puff as wellrnas the Microbial enhanced waterflood test in Daqingrnexcessively low permeability (1.0md-25md) reservoir.rnAfter bacteria injection, 44 among the 60 huff and puffrnwells shows a significant oil production response — thernaccumulative oil increment reaches 6012 tons and therninput-output ratio amounts to 1: 6. The Microbial enhancedrnwaterflood test carried out in June 2004 also provides arnsatisfying result. After the injection of bacteria, thernpressure in the two water injectors decreased more thanrn2MPa, which results in an injection capacity increase. Inrnlate 2004, the fluid production of the 5 producers (the totalrnnumber is 8) is increased from 29.5 tons per day (beforernbacteria injection) to 44.4 tons per day, and the corresponding oil production is increased from 20.8 tonsrnper day (before bacteria injection) to 36.9 tons per day.rnThese make MEOR a very promising oil recovery methodrnin Daqing Oilfield.