Abstract

We have carried out flooding test with cores, sandpack, pore level model by microbe NG80, special metabolic products (G01,G02,G03) under reservoir temperature. The results are:

  1. Microbes migrated through core pore and fermented in it; microbial concentration has an increasing trend, part of cells were absorbed on sand surface.

  2. Oil recovery that flooded by bacteria with concentration 10% is over 6% higher than in water.

  3. The highest recovery is 13.8%, flooded at best flooding mode, NG80 products and its constitute;

  4. The earlier the time of injecting fermented broth, the better the result obtained;

  5. Metabolites bear effect of denudation on oil films; and metabolisms result in alteration of wettability, in witch a special biochemical process and " in situ growth" effects characterized by bacteria take place;

  6. Mechanisms observed in the pore level model during microbial flooding are: starting residual oil re-flowing by emulsification-carrying, changing the wettability, denuding oil films and producing " Jamin Effect" in the pores while flooding.

We performed microbial flooding program in G69 block, which has 5 injections wells and 7 drainage points. Mixed original, NG80, 80 and DG2, fermented broth 720m3 was injected in with three slugs during March to July,2001. Monitored preliminary results show that the decline trend of the block oil production was controlled and some wells' production began to increase. That the mechanism of microbial flooding in the oilfield improves poducibility.

Introduction

Enhancement of oil recovery is critical for mature fields. EOR by microbial flooding becomes a focus among producing countries because of its cost effectiveness, wide applicability, easily operability and non-damaging to formation and environment [1,2,3,4]. Microbes with hydrocarbons as carbon source can enhance oil recovery by biological and biochemical effects. More specifically, microbes in a reservoir can grow to improve oil properties, and meanwhile, the metabolically beneficial products modify the solid and liquid phases to increase oil mobility. However, picking the right microbe candidate is key. Many pilot tests turn out that this is significant, and further study is required on the mechanisms.

This paper testifies the microbial displacement mechanisms in a pilot laboratory simulation of G69 block, including interaction of microbe with oil in porous media, microbe growth and migration, effect of metabolic components and concentrations on EOR. Flow mechanisms were observed in pore level model.

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