关键词: 聚合物驱后油藏, 激活剂, 内源微生物, 菌群结构, 现场试验

Abstract: Based on the characteristics of indigenous microbial growth in reservoirs after polymer flooding (RAPFs), a field test was conducted to activate indigenous microorganisms for microbial enhanced oil recovery (MEOR) in representative RAPFs in the east of Nan-2 district in Sanan development zone, Daqing oilfield. The optimized activator, which consisted of corn steep powder, NaNO₃, and (NH₄)₂HPO₃, was injected alternately with protectant polymer. The changes in indigenous microbial community structure before and after activation were examined using terminal restriction fragment length polymorphism analysis, in order to determine the feasibility for application of indigenous MEOR technique. Results showed that: there existed a significant gas supercharging effect in the RAPFs; Dynamic changes in the driving pressure of RAPFs and substantial fluctuations in the δ¹³C isotope contents of microbially produced CH₄ and CO₂ confirmed that the addition of activator promoted alternative micro-aerobic and anaerobic metabolism of indigenous microorganisms in the reservoir; there were significant changes in the major biochemical parameters of the produced fluid after activation of indigenous microorganisms; the dominant indigenous microbial populations included Pseudomonas, Thauera, and Arcobacter, whose abundance experienced great increases after activation; the incremental oil production was 3 068.13 t while the water content declined by 2.2%, indicating that MEOR application significantly improved the oil recovery. This work proved that it is feasible to activate indigenous microorganisms for MEOR in RAPFs, which provides an alternative approach for further improving oil recovery in similar reservoirs.

Key words: reservoir after polymer flooding, activator, indigenous microorganism, microbial community structure, field test