Effects of indigenous microorganisms on the properties of oil and water

Abstract EN

The objective of this research was to obtain additional informations about the effects of nutrition conditions on indigenous bacterial growth.

In situ microbial growth results in production of metabolic products which affect the physical and interfacial properties of crude oil and water.

A heavy crude oil (19° API gravity) was used in the study.

The crude oil has a 1.63 mg KOH/gm per sample organic acidity and viscosity of 200 cP at room temperature.

Nutrient solutions were prepared from 0.1% ammonium phosphate and molasses concentrations of 2,4, and 6% by weight.

The water used in nutrient solutions was tap water and brines containing 20000 and 45 000 ppm NaCl.

The nutrients were incubated with equal volume of crude oil at different temperatures.

After incubation, measurements were conducted to determine oil and water viscosities, oil volume, water acidity, and oil/water interfacial tension.

The results showed that the indigenous microorganisms attained their maximum growth after 8 days.

The nutrient support containing 2w% molasses, and 0.1% ammonium phosphate showed best results, when based on metabolic products that reflected on oil/ water interfacial tension reduction and oil emulsification.

The 20000 ppm NaCl gave better in situ growth of bacteria than the 45 000 ppm NaCl brine and tap water.

The results showed that temperatures ranging between 25°C and 45°C were best for microbial growth.

A reduction in pH values was observed and attributed to production of metabolic acid products, while an increase in water viscosity was attributed to biopolymer production and the reduction of IFT was attributed to metabolic biosurfactant products.