Screening Of Microbial Strains And Displacement Characteristics Evaluation For High Salinity Reservoir

With the increase of petroleum exploration scale, the chance of discovering self-contained large scale oilfield was smaller and smaller in our country, while the high-speed development of the national economy to demand for petroleum increased constantly, and in order to adapt to current economic situation, the development and construction target of China petroleum industry turned to low production, low pressure, low permeable oil fields gradually. In the tense situation of the current oil reserve reserves, how to develop the low (extra-low) permeability oil field the extremely vital significance for the continuous and steady development of oil industry in our country. MEOR technique was using microbial metabolic activities and its metabolites acted on reservoir and reservoir fluid to realize EOR, it could be used to EOR, while had the functions of broken down, viscosity break and paraffin removal, and had the features of lower cost , fine applicability, simple construction, no damage to reservoir and no environmental pollution, etc. This had already caused the petroleum engineers'attention, and was an economy effective means of exploiting low yielding and inefficient oilfield, and had given initial results in field test at home and abroad.This paper studied oil field development experimental zone which had the typical characteristics of low permeability and low pressure, through a series of separation and screening experiments this paper found suitable strains for reservoir properties of this area to improve oil recovery. One strain Ym4 which had great ability of producing bio-surfactant was screened, the surface tension of its fermentation liquor was less than 30mN/m, the viscosity of fermentation liquor of the strain P which produced polymer was higher than 25mPa?s, the petroleum hydrocarbon degrading strain Ym8 made the non-hydrocarbon contents in crude oil drop from 9.01% to 6.18%, the bituminous contents were from 6.58% to 5.15%, while the aromatic contents were increased from 13.86% to 15.98%, the saturated hydrocarbon contents were from 70.02% to 70.79%, and the viscosity of crude oil was dropped from 49mPa?s to 24mPa?s, viscosity reduction rate reached 51%. The culture medium compatibility research of different strains showed that three strains all had high number of bacteria when they were single and mix cultured, each was not affected, the performance of their metabolic product was not changed too, they all adapted to the reservoir conditions in test area. Through the experiments of different core permeability, strains concentration and the amount of strains, finally determined the reasonable concentration of bacterium fluid was 10%, the usage was 0.5 PV. The experiment results of three tube parallel model showed that the mixed strains could effectively alter the flow distribution of the follow-up injected water. The proportion of fluid withdrawal rate in high permeability layer dropped from 71% to 54% after strains role, but increased from 29% to 40% in medium permeability layer, from 0% to 6% in low permeability layer. After mixed bacteria function, the recovery in high permeability layer increased 3%, 10% in medium permeability layer, 9% in low permeability layer, compared with single tube model, the recovery of strains H in medium and low permeability layer was great improved.