Evaluation of Microbial Growths on Drilling Muds used in an On-Shore Drilling Well Located in Edo State.
Abstract
The growth of indigenous microorganisms on drilling muds used in facilitating a borehole of oil and gas located at Ologbo were evaluated. Growth profiles of bacterial and fungal isolates in mineral salt medium amended with 1%
drill muds were examined in a rotary shaker at 120 rpm at 30 0 C for 14 days. The growth kinetics of isolates at different concentrations of drilling muds was assessed (by using the total viable count data to calculate the test
organisms’ specific growth rate and generation (doubling) time after appropriate incubations). Findings revealed that, the highest bacterial count was 5.8x10 3 cfu/ml recorded for Micrococcus sp. in medium amended with a water based mud and attained its peak at day 6. Contrary, the least fungal count was 0.2x10 3 cfu/ml by Penicillium sp. and Aspergillus sp. in medium amended with synthetic based mud, with a growth peaked at day 8 of incubation. The growth rates (h -1 ) of the test isolates decrease as concentrations of the drilling muds increased while the generation
times were stimulated. The highest growth rate (h -1 ) of 1.32±0.01 was recorded for Micrococcus sp at 4% and 6% water based mud substrate, while the least growth rate (h -1 ) of 0.33±0.01 and 0.33±0.05 was recorded for
Aspergillus sp at 4% and 6% synthetic based mud substrates respectively. The metabolic abilities of test organisms were clear indications that both synthetic based mud and potassium chloride polymer water based mud are
biodegradable and their harmful effects may have been occasioned by oxygen depletion when cuttings are discharged into receiving environment.
drill muds were examined in a rotary shaker at 120 rpm at 30 0 C for 14 days. The growth kinetics of isolates at different concentrations of drilling muds was assessed (by using the total viable count data to calculate the test
organisms’ specific growth rate and generation (doubling) time after appropriate incubations). Findings revealed that, the highest bacterial count was 5.8x10 3 cfu/ml recorded for Micrococcus sp. in medium amended with a water based mud and attained its peak at day 6. Contrary, the least fungal count was 0.2x10 3 cfu/ml by Penicillium sp. and Aspergillus sp. in medium amended with synthetic based mud, with a growth peaked at day 8 of incubation. The growth rates (h -1 ) of the test isolates decrease as concentrations of the drilling muds increased while the generation
times were stimulated. The highest growth rate (h -1 ) of 1.32±0.01 was recorded for Micrococcus sp at 4% and 6% water based mud substrate, while the least growth rate (h -1 ) of 0.33±0.01 and 0.33±0.05 was recorded for
Aspergillus sp at 4% and 6% synthetic based mud substrates respectively. The metabolic abilities of test organisms were clear indications that both synthetic based mud and potassium chloride polymer water based mud are
biodegradable and their harmful effects may have been occasioned by oxygen depletion when cuttings are discharged into receiving environment.
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