Title : Microbial enzymes as green flow assurance agents for mitigating wax deposition in crude oil pipelines
Abstract:
Wax deposition remains one of the most persistent flow assurance challenges in crude oil production and transportation, particularly in waxy crude oils containing high concentrations of long-chain paraffinic hydrocarbons. Conventional mitigation techniques, including thermal, mechanical, and chemical treatments, are often associated with high operational costs, environmental concerns, production downtime, and potential damage to pipeline infrastructure. Consequently, there is increasing interest in environmentally sustainable alternatives for wax control.
This study investigated the potential of locally sourced microbial enzymes and biosurfactants for mitigating wax deposition in crude oil pipelines. A waxy crude oil sample obtained from the Niger Delta region was characterized and found to possess a density of 0.8515 g/mL, viscosity of 11.997 cSt at 32°C, and molecular weight of 209.48 g/mol. Hydrocarbon composition analysis revealed dominance of long-chain hydrocarbons (>C12) with a concentration of 197.14 g/mol, while C30+ fractions constituted 24.40 g/mol (11.65%), confirming the wax-prone nature of the crude oil.
Microbial enumeration and isolation were conducted using standard microbiological techniques. Total heterotrophic bacterial counts ranged from 1.3 ± 0.3 × 10⁴ to 2.6 ± 0.3 × 10⁴ CFU/mL, while hydrocarbon-degrading bacterial populations ranged from 1.2 ± 0.52 × 10⁴ to 1.8 ± 0.20 × 10⁴ CFU/mL. Four bacterial species were identified: Bacillus cereus, Bacillus subtilis, Micrococcus spp., and Pseudomonas aeruginosa. Screening for enzyme and biosurfactant production demonstrated that P. aeruginosa and B. subtilis possessed strong surface-active properties as evidenced by positive drop-collapse, oil-spread, emulsification index, and β-haemolysis tests. Maximum biosurfactant production was recorded for P. aeruginosa (%EC24 = 52.05), followed closely by B. subtilis (%EC24 = 50.00). Lipase production was observed in all isolates, with P. aeruginosa exhibiting the highest activity of 10.3 ± 0.2 U/mL.
Application of microbial cultures and cell-free enzyme extracts significantly improved the physicochemical properties of the waxy crude oil. Crude oil density decreased from 0.8515 g/mL to 0.8410 g/mL following treatment with a consortium of P. aeruginosa and B. subtilis. The lowest viscosity value of 8.379 cSt was obtained with B. subtilis treatment. Wax appearance time increased significantly to 117 ± 4.2 seconds under consortium treatment, indicating improved wax inhibition performance. Molecular weight reductions of up to 8.3% were also achieved. Furthermore, hydrocarbon compositional analysis revealed substantial degradation of long-chain hydrocarbons, along corresponding increases in short- and medium-chain fractions.
The findings demonstrate that locally sourced microbial enzymes and biosurfactants can effectively modify crude oil composition and reduce wax-forming tendencies. These biotechnological agents offer a sustainable, environmentally friendly, and cost-effective alternative to conventional wax-control methods in crude oil transportation systems. Their application has significant potential for improving flow assurance, reducing operational costs, and enhancing environmental sustainability in the petroleum industry.
Keywords: Wax deposition, Flow assurance, Biosurfactants, Microbial enzymes, Lipase, Waxy crude oil, Pipeline transportation, Green technology, Pseudomonas aeruginosa, Bacillus subtilis
