Jitendra Sangwai

Increasing maturity of the crude oil reservoirs across the world have led to the production of waxy crude oil which need economical and efficient methods for enhanced oil recovery (EOR). The studies on the performance of bacteria in the presence of waxy crude oil is rare. In this study, experiments were performed to understand the efficacy of thermophillic microorganism Bacillus subtilis on the biodegradation of waxy crude oil for EOR applications. Bacterial growth, changes in crude oil composition, viscosity reduction, and surface and emulsification activity have been monitored to evaluate the oil degradation capabilities of the bacteria. This study also presents the effect of temperature, salinity, pH, and pressure on the stability of the produced biosurfactant for EOR applications. The biosurfactant produced by bacteria in the presence of crude oil was found to be stable up to 120°C, 10 MPa, 15% salinity, and wide range of pH, and thus favorable for reservoir environment. The crude oil composition before and after degradation at 75°C was determined using gas chromatography-mass spectroscopy and observed to be 60% in one day, while the maximum viscosity reduction was found to be 60% from initial values. Experimental results showed that the bacteria used in this work are capable of surviving at reservoir conditions, and are easy to grow on the waxy crude oil for enhanced oil recovery operations.

Conventional oil reserves are under production past several years, leaving the higher end hydrocarbons (paraffins/waxes) in the reservoir. The separation and deposition of these waxy components in the production and surface facilities are predominant when the system temperature reduces below the wax appearance temperature (WAT) during the flow of crude oil from a reservoir to the surface. It is, therefore, necessary to address various challenges posed by long chain paraffins using an economical, versatile, and eco-friendly technique. In the current scenario, microbial degradation of paraffins has gained considerable attention because of its environmentally friendly and operationally safer nature than other methods for sustainable development. In this study, the bio-surfactant producing microorganism Pseudomonas fluorescens, isolated from the marine port in Chennai, India, is used to degrade a wax sample, namely eicosane. The viscosity reduction and the delay in wax appearance temperature has been noticed. This study also analyzes the physico-chemical characteristics of the bio-surfactant produced by the microbe. The degradation of long chain paraffin to short chain molecule is confirmed by the gas chromatography-mass spectrometry (GCMS) result. From the GCMS results, it has been observed that 93% of the wax degraded in 10 days. The amount of bio-surfactant produced by the microbe is found to be as high as 9.5 g/L. The high surface tension reduction, production of higher amount of bio-surfactant, viscosity reduction and high rate of degradation indicates the potential of the microbe in flow assurance, oil-spill, enhanced oil recovery, etc.

The overall oil production worldwide has declined due to the increase in maturity of the oil reservoirs. In developing countries like India, the oil production and demand plays a crucial role for the development of economy of the country. However, the domestic crude oil production is insufficient to meet the requirement for energy. Thus, there is a big challenge to minimize the gap between the demand and supply for crude oil. Several methods to enhance oil recovery have been developed to increase the production from matured reservoirs and are referred to as enhanced oil recovery (EOR) methods. This chapter discusses in detail about the various EOR methods, their applicability, and the screening criteria for various reservoir types. The EOR methods are further discussed in Indian contexts. This chapter also summarizes the details of various oilfields in India. The chapter will in general, help to understand the recent trends and the need of EOR for Indian oil reservoirs.

The present work investigates the reaction kinetics of biodegradation of waxy crude oil using Bacillus subtilis YB7, a thermophilic organism. Mathematical modeling of the reaction kinetics of microbial growth together with biosurfactant production and hydrocarbon substrate utilization have been attempted. Although various models, such as Monod's, Logistic, Tessier and Contois were investigated for substrate degradation and biomass production, and compared with the experimental studies, none of them could accurately predict the biosurfactant production in the presence of waxy crude oil. In this study, a new model, which is an extension of Monod's equation, has been developed to predict the observed values of biosurfactant production along with substrate degradation and biomass production in the presence of waxy crude oil satisfactorily. The proposed model has also been tested with various experimental studies carried out in the literature. The proposed model is observed to provide satisfactory model predictions when compared to other models available in literature. This shows that the proposed model can be used to study the reaction kinetics of all types of biodegradation studies to find the optimum parameters for maximum possible biodegradation of hydrocarbon substrates and production of biosurfactant. The positive values of activation energy observed in the study indicates that the process of biodegradation is an endothermic process. The negative values of entropy indicates that the reacting molecule underwent an internal rearrangement to give the activated complex, without a change in the number of molecules. It is believed that this study will be suitable for possible model development for biodegradation of hydrocarbons for oil recovery applications or bioremediation methods.

The study has been carried out to investigate the production of biosurfactant by a thermophilic strain of Bacillus subtilis on various hydrocarbon substrates, such as waxy crude oil, model crude oil and six long chain paraffins (C16H34 to C36H74) at 35, 50 and 75 °C. Model crude oil represents the mixture of the six long chain paraffins. The maximum biosurfactant production has been found to occur at 50 °C with n-hexadecane (C16H34) as a substrate. It has also been inferred that the physico-chemical properties of the biosurfactant is reduced with an increase in carbon number in the hydrocarbon substrate. Biosurfactant production is observed to be higher in the presence of waxy crude oil than the model crude oil, which is due to the presence of short chain paraffins with fewer carbon numbers in the former. B. subtilis in the presence of waxy crude oil has been observed to show high microbial adherence, improved surface tension reduction and emulsification activity, production of higher amount of biosurfactant 'surfactin', and improved biosurfactant stability upto 120 °C at 10 MPa, 10% (w/v) salinity and pH 8-14. This indicates the potential of microorganism in tackling oil-spill, wax degradation, flow assurance and enhanced oil recovery.

Most of the crude oil reservoirs in the world are getting matured leading to the increased production and deposition of long chain paraffins (wax) at subsurface and surface facilities creating a challenge for flow assurance and safer operation. Deposition of wax on the inner walls of the pipelines tends to decrease the flow of crude oil thereby causing billions of dollars of loss. This article reviews in detail about the various aspects of the microbial degradation of waxy crude oil, along with different mechanisms involved in the hydrocarbon degradation. In addition, the article acts as a guide to screen the microorganism suitable for different environmental conditions for their applications in pipelines, oil spill remediation and microbial-based enhanced oil recovery technique to waxy and heavy oil reservoirs for environmentally safe operation.

Microbial degradation of waxy crude oil provides efficient, economical and environment friendly solution to enhance the waxy crude oil production from mature brownfield crude oil reservoirs, addressing flow assurance challenges during transportation, and on-shore and off-shore oil-spill remedies. This study systematically investigates the utilization of thermophilic Bacillus subtilis for the degradation of waxy crude oil obtained from the oilfield and model crude oil prepared by various higher molecular weight waxes suitable for high temperature applications. The influence of microorganism to improve the flow behavior of waxy crude oil has been analyzed by means of viscosity and compositional degradation. The degradation and reduction in the viscosity of crude oil at various temperatures have been analyzed. More than 95% of degradation has been observed in 15 days for both the crude oil samples at 50. °C. The simple nutrient and microorganism combination and the high activity of enzymes aided to get utmost and faster degradation of the crude oil. This study will be useful to employ the thermophilic bacteria for various oilfield applications.

The long chain paraffinic hydrocarbons (waxes) present in crude oil pose serious issues in the upstream oil and gas industries. The waxy hydrocarbons are reflected in their resistance to biodegradation when released into the environment. Microbial degradation of these paraffins is an alternative way to address the various issues effectively and economically. The present study investigates the utilization of thermophilic Bacillus subtilis isolated from Chennai, India for the degradation of waxes, such as n-hexadecane, n-eicosane, n-tetracosane, n-octacosane, n-dotriacontane and n-hexatriacontane. Several experiments have been conducted to observe the efficiency of Bacillus subtilis at various operating temperatures and concentrations of paraffins. We inspected the primary degradability of paraffins using gas chromatography mass spectrometry and ultimate biodegradability using viscosity analysis. The degradation of paraffins at 50 °C was observed to be 60 to 77% in one day, and 78 to 98% in ten days. The performance of Bacillus subtilis at 50 °C was observed to be higher than the performance observed at 35 and 75 °C. The viscosity of paraffins has reduced with decrease in carbon number and increase in degradation time. The functional groups present after the biodegradation were investigated using Fourier transform infrared spectroscopy. We also observed that the energy required for the activation of paraffin degradation increases with decrease in enzymatic activity and increase in carbon number. The current study with the information on the percentage degradation and viscosity reduction during the degradation of various long chain paraffins will add value in the development of a robust model for microbial degradation of complex mixtures of hydrocarbon systems suitable for upstream oil and gas applications.

Marine and costal pollution has become a global concern in recent years due to the increase in intensity of contaminants in the marine environment. The release of crude oil in the marine environment during exploitation and transportation cause serious environmental pollution, owing to the presence of toxic organic compounds. Crude oil, which is the most predominant energy resource throughout the word is the complex mixtures of hydrocarbons including more than 70% of alkanes along with aromatics, naphthenes and resins. The long chain alkanes present in the crude oil remains persistent due to its non-volatile nature and pose a major menace to terrestrial and marine ecosystems. Biodegradation has emerged as a potential and economical technology for the restoration of oil spilled environment. It provides efficient, economical and environment friendly solution for on-shore and off-shore oil spill remedies. The present study investigates the degradation of crude oil using a biosurfactant producing microorganism 'Bacillus subtilis' to obtain maximum degradation. Bacillus subtilis isolated from polymer dump site, Chennai, India was used for the degradation of crude oil. Crude oil degradation and viscosity reduction was observed to be 80% and 60%, respectively, in 10 days. The high microbial adherence, surface tension reduction, emulsification activity, production of higher amount of biosurfactant, stability of the produced biosurfactant at extreme environment conditions, viscosity reduction and high rate of degradation indicates the potential of the microorganism for oil spill treatment.

Microorganisms play an important role in the formation of methane hydrate in subsea environment. Studies involving the effect of biosurfactants produced by microorganisms on methane hydrate formation kinetics are not well understood. The present work investigates the influence of cell free solution containing biosurfactant obtained during the cultivation of microorganisms on the formation kinetics of methane gas hydrate. Two microorganisms, viz., Pseudomonas aeruginosa CPCL and Bacillus subtilis YB7 have been used to produce biosurfactants namely, rhamnolipid and surfactin, respectively. The performance of the cell free solution containing various concentrations (200, 400, 600, 800 and 1000 ppm) of biosurfactant to form the methane gas hydrate was analyzed by adding it into the pure water system and compared with synthetic surfactant, sodium dodecyl sulfate (SDS). It has been observed that the introduction of biosurfactant into pure water system improves the formation kinetics of methane hydrate and reduced the induction time. Addition of 200 ppm of rhamnolipid solution in pure water system has resulted in 47.3% of methane gas to hydrate conversion with an induction time of about 0.23 h, whereas pure water showed 45.1% conversion with an induction time of about 5.77 h. The same concentration of surfactin and SDS have resulted in 42.7 and 33.3% of methane gas to hydrate conversion, respectively. Biosurfactants studied here shows efficient and better performance than their chemical counterpart, namely SDS. This study also provides information on the optimum biosurfactant concentration for the improved formation kinetics of methane hydrate. The results suggest that the utilization of environment friendly biosurfactant can be used as an effective kinetic promoter for the methane hydrate formation suitable for optimum storage and transportation of natural gases.