Laboratory study on activating indigenous microorganisms to enhance oil recovery in Shengli Oilfield

Microbial enhanced oil recovery (MEOR) offers an economic alternative to enhanced oil recovery (EOR). In accordance to the source of the microorganisms used, microbial enhanced oil recovery can be categorized into two types: injected exogenous microorganisms or utilized indigenous microorganisms for enhanced oil recovery. Indigenous microorganisms for MEOR have greater advantages compared to injected microorganisms. For example, this technology does not need additional injection instruments for in situ inoculation and the indigenous microorganisms adapt, grow, and breed more easily in the oil reservoir.Laboratory studies show the existence of some species of indigenous microorganisms (mainly bacteria) in crude oil and formation water of S12 block in Shengli Oilfield, such as hydrocarbon degrading bacteria (HDB), denitrifying bacteria (DNB), methane producing bacteria (MPB), sulfate reducing bacteria (SRB), iron bacteria (IB), sulfur bacteria (SB), and total growth bacteria (TGB). These indigenous bacteria are the objective of investigations for the MEOR.The results of the chemical analyses, bacteriological analyses of the crude oil and water samples, and the growth and physical simulation experiments are presented. The results show that the indigenous bacteria beneficial to MEOR can be selectively stimulated by nutrient injection while the detrimental bacteria can be restricted to some extent, enabling oil recovery to be enhanced by 9.14% after the first waterflooding.