Compared with other enhanced oil recovery (EOR) techniques like gas flooding, chemical flooding, and thermal production, the prominent advantages of microbial enhanced oil recovery (MEOR) include environment-friendliness and lowest cost. Recent progress of MEOR in laboratory studies and microbial flooding recovery (MFR) field tests in China are reviewed. High biotechnology is being used to investigate MFR mechanisms on the molecular level. Emulsification and wettability alternation due to microbial effects are the main interests at present. Application of a high-resolution mass spectrum (HRMS) on MEOR mechanism has revealed the change of polar compound structures before and after oil degradation by the microbial on the molecular level. MEOR could be divided into indigenous microorganism and exogenous microorganism flooding. The key of exogenous microorganism flooding was to develop effective production strains, and difficulty lies in the compatibility of the microorganism, performance degradation, and high cost. Indigenous microorganism flooding has good adaptation but no follow-up process on production strain development; thus, it represents the main development direction of MEOR in China. More than 4600 wells have been conducted for MEOR field tests in China, and about 500 wells are involved in MFR. 47 MFR field tests have been carried out in China, and 12 field tests are conducted in Daqing Oilfield. MFR field test’s incremental oil recovery is as high as 4.95% OOIP, with a typical slug size less than 0.1 PV. The input-output ratio can be 1 : 6. All field tests have shown positive results in oil production increase and water cut reduction. MEOR screening criteria for reservoirs in China need to be improved. Reservoir fluid, temperature, and salinity were the most important three parameters. Microbial flooding technology is mature in reservoirs with temperature lower than 80°C, salinity less than 100,000 ppm, and permeability above 5 mD. MFR in China is very close to commercial application, while MFR as quaternary recovery like those in post-polymer flooding reservoirs needs further study.

In low oil price era, it seems that ASP flooding has little market. However, ASP progress in China shows that ASP flooding is good technology to help oil companies thrive and make profit. Since 2014, ASP flooding has entered industrial application in Daqing oilfield. ASP flooding production in 2015 is 3.5 million ton, 9% of the oilfield’s total production of Daqing oilfield. There are 22 ASP flooding blocks in Daqing, containing 7231 wells and 3 are new blocks in 2016. Obviously, more and more ASP flooding is being carried out. Another large ASP flooding field test in high temperature (80°C) in Henan oilfield has got staged incremental oil recovery of 7.7%. Latest theory and application in ASP flooding in China are reviewed to help ASP flooding go from success to more application. Weak alkali is better than strong alkali ASP flooding. Relation between viscosity and IFT is discussed. This paper also explains why weak alkali ASP flooding is promoted in Daqing after 12 field tests on strong alkali one. ASP flooding can be a great help to survive low oil price.

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Capillary number theory is very important for chemical flooding enhanced oil recovery. The difference between microscopic capillary number and the microscopic one is easy to confuse. After decades of development, great progress has been made in capillary number theory and it has important but sometimes incorrect application in EOR. The capillary number theory was based on capillary tube bundles and Darcy’s law hypothesis, and this should always be kept in mind when used in chemical flooding EOR. The flow in low permeability porous media often shows obvious non-Darcy effects, which is beyond Darcy’s law. Experiments data from ASP flooding and SP flooding showed that remaining oil saturation was not always decreasing as capillary number kept on increasing. Relative permeability was proved function of capillary number; its rate dependence was affected by capillary end effects. The mobility control should be given priority rather than lowering IFT. The displacement efficiency was not increased as displacement velocity increased as expected in heavy oil chemical flooding. Largest capillary number does not always make highest recovery in chemical flooding in heterogeneous reservoir. Misuse of CDC in EOR included the ignorance of mobility ratio, Darcy linear flow hypothesis, difference between microscopic capillary number and the microscopic one, and heterogeneity caused flow regime alteration. Displacement of continuous oil or remobilization of discontinuous oil was quite different.