This research model Microbial Enhanced Oil Recovery (MEOR) using two known simulators: UTCHEM and PHREEQC. We elucidate of environmental conditions effect on MEOR process by using real experimental data of an oil-degrading bacteria. Our work differs from previous research in that, we model MEOR operations with emphasis on oil viscosity reduction. Also, we elaborate on the geochemical reactions involved with nutrient/brine injection into oil reservoirs prior to and during microbial. PHREEQC was used to simulate the hydrochemistry reactions between the synthetic formation brine and the pulsating nutrient (yeast extract – nitrogen source)/brine solution in the absence of microbe. Hitherto, we modelled the enhancement of oil viscosity by assuming production of gases and by the direct action of the microbe on heavy hydrocarbon chains using UTCHEM. It was observed that the geochemical and transport model depicts the precipitation of Calcite as well as the dissolution of K-Feldspar. There was the evolution of CO2 and CH4 gases. Moreover, altering temperature and pH, appreciably affected the saturation indices of the various phases. The enhancement of oil recovery reached 10% by increasing the yeast extract concentration from 50 mg/l to 500 mg/l at a salinity of 10 g/l and temperature of 60 degrees Celcius.