EOR technology of microbial field with target dominant microflora in oil reservoir

In order to improve the effects of microbial enhanced oil recovery (EOR), chemical flooding and water flooding are introduced in the process of microbial flooding. And in order to enhance the oil recovery factor, a microbial field of target predominant microflora is built up in oil reservoirs. Baolige Oilfield was taken as the example. By taking the technical measures (e.g. screening the target predominant microflora and establishing the efficient ground fermentation process), the bacterial concentration of its injected fluid was increased from 10⁶/mL to 10⁸/mL and the surface tension of its injected fluid was decreased by 18.6%. Furthermore, the mutual effects between chromium movable gel, colloid and microorganisms were investigated and the measures for enlarging the swept volume were taken correspondingly, including profile control, separate injection and separate layer reconstruction. It is shown that 3 years after its implementation in the test areas of fault block Ba 19 and Ba 38 of Baolige Oilfield, the microbial field of target microflora is built up inside the oil reservoirs. Compared with the values in 2012, the recovery factor is 6.77% and 6.1% higher, respectively. The composite water cut is 3.46%−6.91% lower than that of water flooding, the bacterial concentration of the produced fluid increases from 10⁵/mL to 10⁶/mL and the surface tension decreases by 10.7%. The studies on the EOR technology by building up microbial field of target predominant microflora in oil reservoirs provide the valuable technology and theory for the large-scale implementation of microbial EOR technology.