Petroleum Recovery Research Articles

Effects of Short-Chain n-Alcohols on the Properties of Asphaltenes at Toluene/Air and Toluene/Water Interfaces

Crude oil asphaltenes contain a wide series of chemical species, which includes the most polar compounds and interfacially active agents from the petroleum. Asphaltenes have been considered to be implicated in foam and emulsion formation during the petroleum recovery and production process. In this work, the interfacial activity of organic solutions containing asphaltene and n-alcohols was investigated. Asphaltene extraction from a 28°API crude oil produced 2.5 wt % of n-pentane precipitated asphaltene (C5I). Dynamic surface and interfacial tensions of asphaltene solutions were assessed by the pendant drop method. Asphaltene films were evaluated at the air-water interface using a Langmuir trough. Results were expressed by means of the interfacial tension time-dependence. Interfacial tension measurements showed alcohols reduce the toluene/water interfacial tension of asphaltene solutions. The interfacial tension was reduced from 23 mN/m to 15.5 mN/m for a 2 g/L solution of asphaltene plus n-butanol. Higher asphaltene concentrations did not affect the toluene/air surface tension. The effects of n-alcohols on the asphaltene surface activity was dependent on the asphaltene aggregation state. n-Alcohols modify the asphaltene film elasticity and the film phase behavior.

Shining the spotlight on the petroleum resource rent tax

The petroleum resource rent tax (PRRT), a 40% profits-based upstream tax that applies to Australian oil and gas projects, has come under significant scrutiny as to its effectiveness in providing an appropriate return to the community for the exploitation of Australia’s petroleum resources. The April 2017 independent Callaghan review into the design and operation of the PRRT found that it remained the preferred way of achieving a fair return to the community from petroleum exploration and recovery, without discouraging investment into the sector. However, the Callaghan review recommended possible changes to the regime to improve its sustainability and compatibility with the current state of the industry, while ensuring fiscal stability for existing investments. In response to the findings and recommendations of the Callaghan review, Australian Treasury embarked on a consultation process to investigate potential reform options to the PRRT. Government has yet to announce its decision on the way forward. What the future holds for the PRRT and the consequential impact on existing and new or proposed projects remain to be seen pending the Government’s chosen policy direction. This paper covers the following: • a survey of the economic rent theory underpinning the framework of the PRRT regime, including its pros and cons compared with other forms of resource taxation • a review of key recent developments in the administration and interpretation of the PRRT law, and • how the PRRT regime is anticipated to change and the associated repercussions on the after-tax economics and practical compliance for existing and future projects.

Two-stage genetic algorithm for parallel machines scheduling problem: Cyclic steam stimulation of high viscosity oil reservoirs

In this paper, the problem of optimal assignment of trailer-mounted steam generators for cyclic steam stimulation (CSS) of petroleum wells is formulated as a parallel uniform machines scheduling (PMS) problem with release dates. The total weighed tardiness is used as the goal of the optimization process. The distinctive features of the proposed PMS formulation include: jobs with variable weights, variable machine setup time, constraint capacity of drilling pads (where machines are allocated), and modified tardiness criterion. A two-stage scheduling algorithm combining heuristic and genetic algorithms is proposed for solving it. A chromosome representation, crossover and mutation operators generating only feasible solutions and thus avoiding the use of any repair mechanism are discussed. The performance of the algorithm is tested on a real-world data set from the oilfield asset located in the coastal swamps of the Gulf of Mexico. The experiments indicate that the proposed approach gives good results in optimization of the operational costs and petroleum recovery. The algorithm is implemented as a part of the software platform for optimization of CSS and currently is in use by oilfield engineers.

Characterization of organic-rich shales for petroleum exploration & exploitation: A review-Part 3: Applied geomechanics, petrophysics and reservoir modeling

Modeling geomechanical properties of shales to make sense of their complex propert-ies is at the forefront of petroleum exploration and exploitation application and has received much research attention in recent years. A shale’s key geomechanical properties help to identify its “fracibility” its fluid flow patterns and rates, and its in-place petroleum resources and potential commercial reserves. The models and the information they provide, in turn, enable engineers to design drilling pat-terns, fracture-stimulation programs and materials selection that will avoid forma-tion damage and optimize recovery of petroleum. A wide-range of tools,technologies, experiments and mathematical techniques are deployed to achieve this.Characterizing the interconnected fracture, permeability and porosity network is an essential step in understanding a shales highly-anisotropic features on multiple scales (nano to macro). Well-log data, and its petrophysical interpretation to calibrate many geom-echanical metrics to those measured in rock samples by laboratory techniques plays a key role in providing affordable tools that can be deployed cost-effectively in multiple well bores.Likewise,microseismic data helps to match fracture density and propagation observed on a reservoir scale with predictions from simulations and la-boratory tests conducted on idealised/simplified discrete fracture network models. Shales complex wettability, adsorption and water imbibition characteristics have a significant influence on potential formation damage during stimulation and the sho-rt-term and long-term flow of petroleum achievable. Many gas flow mechanisms and m-odels are proposed taking into account the multiple flow mechanisms involved (e.g., desorption, diffusion, slippage and viscous flow operating at multiple porosity le-vels from nano- to macro-scales). Fitting historical production data and well decl-ine curves to model predictions helps to verify whether model’s geomechanical assu-mptions are realistic or not. This review discusses the techniques applied and the models developed that are relevant to applied geomechanics, highlighting examples of their application and the numerous outstanding questions associated with them.

The effect of a crosslinking chemical reaction on pattern formation in viscous fingering of miscible fluids in a Hele-Shaw cell.

Viscous fingering can occur in fluid motion whenever a high mobility fluid displaces a low mobility fluid in a Darcy type flow. When the mobility difference is primarily attributable to viscosity (e.g., flow between the two horizontal plates of a Hele-Shaw cell), viscous fingering (VF) occurs, which is sometimes termed the Saffman-Taylor instability. Alternatively, in the presence of differences in density in a gravity field, buoyancy-driven convection can occur. These instabilities have been studied for decades, in part because of their many applications in pollutant dispersal, ocean currents, enhanced petroleum recovery, and so on. More recent interest has emerged regarding the effects of chemical reactions on fingering instabilities. As chemical reactions change the key flow parameters (densities, viscosities, and concentrations), they may have either a destabilizing or stabilizing effect on the flow. Hence, new flow patterns can emerge; moreover, one can then hope to gain some control over flow instabilities through reaction rates, flow rates, and reaction products. We report effects of chemical reactions on VF in a Hele-Shaw cell for a reactive step-growth cross-linking polymerization system. The cross-linked reaction product results in a non-monotonic viscosity profile at the interface, which affects flow stability. Furthermore, three-dimensional internal flows influence the long-term pattern that results.

Jurassic source rocks in the Vienna Basin (Austria): Assessment of conventional and unconventional petroleum potential

The Upper Jurassic marlstones (Mikulov Fm.) and marly limestones (Falkenstein Fm.) are the main source rocks for conventional hydrocarbons in the Vienna Basin in Austria. In addition, the Mikulov Formation has been considered a potential shale gas play. In this paper, organic geochemical, petrographical and mineralogical data from both formations in borehole Staatz 1 are used to determine the source potential and its vertical variability. Additional samples from other boreholes are used to evaluate lateral trends. Deltaic sediments (Lower Quarzarenite Member) and prodelta shales (Lower Shale Member) of the Middle Jurassic Gresten Formation have been discussed as secondary sources for hydrocarbons in the Vienna Basin area and are therefore included in the present study.The Falkenstein and Mikulov formations in Staatz 1 contain up to 2.5 wt%TOC. The organic matter is dominated by algal material. Nevertheless, HI values are relative low (<400 mgHC/gTOC), a result of organic matter degradation in a dysoxic environment. Both formations hold a fair to good petroleum potential. Because of its great thickness (∼1500 m), the source potential index of the Upper Jurrasic interval is high (7.5 tHC/m2). Within the oil window, the Falkenstein and Mikulov formations will produce paraffinic-naphtenic-aromatic low wax oil with low sulfur content. Whereas vertical variations are minor, limited data from the deep overmature samples suggest that original TOC contents may have increased basinwards. Based on TOC contents (typically <2.0 wt%) and the very deep position of the maturity cut-off values for shale oil/gas production (∼4000 and 5000 m, respectively), the potential for economic recovery of unconventional petroleum is limited. The Lower Quarzarenite Member of the Middle Jurassic Gresten Formation hosts a moderate oil potential, while the Lower Shale Member is are poor source rock.

Effects of silica nanoparticles and polymers on foam stability with sodium dodecylbenzene sulfonate in water–liquid paraffin oil emulsions at high temperatures

The foam stability of oil–water emulsions stabilised by various surface-active components at high temperature is one of the major problems facing foam-flooding petroleum recovery because of foam instability at the high temperature underground. In this paper, foams stabilised by sodium dodecylbenzene sulfonate (SDBS), polyethylene glycol (PEG) and silica (SiO2) nanoparticles in water–liquid paraffin (50%/50%) emulsions at temperature from 20 to 80°C were studied. Foam properties such as foam stability over time at different temperatures, equilibrium surface tension, and bubble morphology (bubble size) were determined by surface tension measurements and inverted fluorescence microscopy. High foam stability was demonstrated by emulsions of SDBS, PEG, SiO2 nanoparticles, and liquid paraffin from 40 to 80°C. The properties of the PEG–SDBS foams improved when SiO2 nanoparticles were added. Foam stability increased when SDBS was adsorbed on the bubble surface as the bubbles did not rupture easily in the liquid phase in the presence of SDBS because of the formation of closely packed small bubble droplets bridging between neighbouring large bubbles, which were separated by long chain polymers. This phenomenon may arise because the SiO2 nanoparticles formed networks and were adsorbed with surfactant molecules on the bubble surface of the oil–water emulsion, causing the foam inflexibility to increase and thus improving aqueous foam stability at high temperature.

Recovery of a Toxic Cargo from a Sunken Tank Barge: Lessons Learned and Policy Implications

Abstract: In December 2015, operations were successfully completed in the recovery of a highly toxic cargo from the sunken tank barge ARGO in Lake Erie. The ARGO, constructed in 1911, sank in 1937 with a cargo of benzol that contained a high percentage of the carcinogen benzene. The ARGO was previously listed as the highest environmental risk in the Great Lakes by the National Oceanic and Atmospheric Administration’s Remediation of Underwater Legacy Environmental Threats (RULET) study. To recover the cargo, salvors designed a diver directed hot-tapping and pumping system to pump the remaining high benzene cargo from the sunken barge at a depth of approximately 50-feet below the lake’s surface. The cargo off-load system included pumping the cargo to a series of storage tanks onboard a barge equipped with designed-for-purpose inert gas and vapor recovery systems to ensure the safety of the public and responders. Working in a Unified Command that included the Coast Guard, U.S. and Ohio Environmental Protection Agencies and National Oceanic Atmospheric Administration, the salvage crew achieved all operational objectives – from safely conducting around-the-clock cold-water contaminated water diving operations to collecting environmental and barge hull samples for further analysis. The ARGO case study will provide lessons learned to assist future responders in safely performing subsea oil removal operations. Additionally, the case study will frame the discussion of current submerged oil recovery regulations and guidance, including the 2016 American Petroleum Institute (API) sunken oil detection and recovery guidance and the U.S. Coast Guard’s guidance on the classification of Oil Spill Removal Organizations (OSRO) that perform non-floating oil detection and recovery operations.

Prediction of the viscosity of water-in-oil emulsions

ABSTRACTWater-in-oil (W/O) emulsions occur in different parts of petroleum recovery and since their properties are different from those of crude oil and water, it is essential to find information about their physical properties. The water causes some problems and heightens the cost of oil production. Separation of water from oil, water treatment, and disposal of water are the steps that make oil production costly. Among various physical properties of W/O emulsions, viscosity is the most important. Because of droplet crowding, emulsions indicate non-Newtonian behavior, which is why their viscosity is higher than the viscosity of oil and water. As a result, it is essential to have knowledge about the viscosity of W/O emulsions in order to extract and process petroleum properly. In this study, an intelligent model, namely a COA-LSSVM, is presented to accurately prognosticate the viscosity of W/O emulsions. The results indicated that the values estimated by the developed model is in great consistency with the laboratory data by R2 of 0.9972 and MSE of 1.1762 * 10−5. A comparison with another model, which was recently introduced, revealed that the developed model in this study is superior.

Positron-Emission Tomography Offers New Insight Into Wormhole Formation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 180051, “New Insight Into Wormhole Formation in Polymer Gel During Water Chase Floods Using Positron-Emission Tomography,” by B. Brattekås, University of Stavanger; M. Steinsbø, A. Graue, M.A. Fernø, and H. Espedal, University of Bergen; and R.S. Seright, New Mexico Petroleum Recovery Research Center, prepared for the 2016 SPE Bergen One-Day Seminar, Bergen, Norway, 20 April. The paper has not been peer reviewed. Polymer gel is frequently used for conformance control in fractured reservoirs, where it is injected to reside in fractures or high-permeability streaks to reduce conductivity. Polymer-gel behavior is often studied in corefloods, where differential pressure and effluents from fracture and matrix outlets give information about gel deposition during placement and flow paths during chase floods. The work presented in this paper uses complementary positron-emission-tomography (PET)/computed-tomography (CT) imaging to quantify the behavior and blocking capacity of gel during chase waterflooding. Introduction Channeling of injected fluids through a highly permeable fracture network, and the following early fluid breakthrough, may be mitigated by placing a highly viscous polymer gel in the fracture. With polymer gel in place, higher differential pressures may be achieved during chase floods, which can contribute to increased sweep efficiency in the porous matrix adjacent to the fracture network. A polymer gel is formed when a gelant solution is exposed to elevated temperature for a given time, known as the gelation time. Previous work has investigated how the gel state during placement (gel or gelant) influenced the gel behavior during chase floods. The complete paper provides a detailed discussion of previous models for fluid leakoff. In this work, the authors study the extrusion of formed polymer gel through fractures, and its resistance to pressure during subsequent waterfloods. PET imaging is based on the decay of positron-emitting radionuclides. In this work, PET was used to visualize flow of radioactive water through a gel-filled fracture, to augment global measurements, and to increase the understanding of filter-cake formation during formed-gel placement and wormhole formation during chase floods. A discussion of the experimental setup, including limestone- and sandstone-core-plug preparation, polymer-gel placement, the chase-flood procedure, and the PET-imaging process, is provided in the complete paper.

Polymer Flooding: The Influence of Polymer Chemical Structure and the Porous Medium

SummaryPolymer flooding is one of the chemical processes used to enhance the petroleum recovery. The injection of a polymer dissolved in water into a reservoir aims to increase the water viscosity, leading to an improvement of areal and vertical sweep efficiency of the oil that is located inside the pores of the rock formation. The polysaccharides (mainly xanthan gum) and polyacrylamides have been used extensively for this purpose by the oil industry, and several papers were published. However, it is not clear yet how to choose the best polymer for a specific rock formation. In this paper, four polyacrylamides with different structures were evaluated for polymer flooding and the results were correlated to the permeability of the sandstone's core employed. The polyacrylamides of higher average molar mass and higher radius of gyration were more effective in the enhancement of pressure inside the pore rock, especially with the decrease of rock permeability. Even in this case, no evidence of damage by polymer retention or adsorption on the pore rock was shown, indicating that the high polymers selected are good candidates to EOR.

Environmental health risk perception of hydraulic fracturing in the US

AbstractThe advent of new technologies such as directional drilling (D2) and the hydraulic fracturing technique (HFtech) has made it possible to enhance energy production from petroleum reserves. The procedures involved have however aroused public sentiments and triggered the debate on the economic importance of petroleum recovery processes. Public perceptions of the environmental health consequences of these processes have been fuzzy. Public survey was conducted using the United States as a case study to foster the development of the most effective policy relative to environmental health sustainability and energy independence. Participants (n = 1243) were surveyed on the prevalence and concerns for HFtech in proxy communities in 2015. Key to the perception inquiry was the knowledge of respondents on HFtech and the concerns relative to the exploration processes. Ordinal logistic regression and Poisson regression (Pλ) were used to interpret the responses obtained from the participants. The study determined...

Modeling of the Initial Adjustment Parameters of Petroleum Recovery Control Systems. Part 1. Degrees of Detail and Formulation of Models of Vectors of Variables with Disturbances

Features in the process of modeling the vectors of the input and output variables of petroleum recovery process control systems with different degrees of detail of their structures are considered. Methods of monitoring discharges of liquids at perforated depth intervals of water injection and petroleum producing wells of oil and gas deposits as the basic condition for implementing a real-time regime in these systems are proposed. Conditions for increasing the precision with which the parameters of the variables are monitored based on the hardware components employed in measurements of complex borehole media are considered.

A probabilistic and statistical approach as a means of predicting the efficiency of hydraulic fracturing

The study considers mathematical data on the efficiency of using a single-stage and multistage types of hydraulic fracturing for petroleum field development. The research is based on the geological and physical characteristics of the deposits in the latitudinal segment of the Ob River area, which has helped justify the method of choosing the HF technique. The probabilistic and statistical analysis of the commercial efficiency statistics has determined the quantitative criteria for selecting the crack parameters such as length, height and the amount of proppant injected, which can facilitate making estimates for the use of a single-stage and multistage types of hydraulic fracturing. The productive horizon AC-12-3 has a complex geological and physical structure and low reservoir properties, which greatly complicates its development but facilitates active formation of its hard-to-recover deposits.The study has revealed that the technology used to enhance oil recovery from the horizon BC-8-1 on the basis of a single-stage hydraulic fracturing can be effective for quite a limited time not exceeding 3-4 years. Meanwhile, the use of the multistage HF technology on the horizon AC-12-3 showed its higher efficiency compared to the single-stage HF technology.The results of the probabilistic and statistical analysis of the commercial application of the multistage hydraulic fracturing technology have proved that it is necessary to take into account the geological and physical peculiarities of a horizon in order to choose an appropriate technology of petroleum recovery.

Investigation of effect of pore sizes and pore sorting on two phase relative permeability in imbibition process

Relative permeability is one of the main petroleum recovery controller that is a function of porous media and the reservoir fluid. Water flooding titled as one of the eldest EOR methods is still used in some of reservoirs. For proper perception and description of rheology in reservoir scale, knowing the flowing fluid processes specifications and mechanisms and also recognition of porous media type in pore-scale is necessary. In this way, the new age has arrived in reservoir study by introducing porosity model on glass. We can have the two-dimension porous media in actual size by designing a microfluidic chip. This article implies the effects of heterogeneity on relative permeability curves by micro model system and water flooding. High definition photos from different water and oil saturations and also Goodyear equations are used for analyzing the effects of heterogeneity on water and oil permeability in pore-scale. In conclusion, it is observed that in glass micro model oil and water relative permeability curves are dependent on porous media pores sizes. So that as much as these pores grows, the relative permeability will be increased. Moreover, pores sizes distribution and direction have effects on relative permeability.

Defining irreducible water saturation using global characteristics envelopes and novel correlations

Irreducible water saturation plays a significant role in estimating hydrocarbon initially-in-place and petroleum recovery. Yet, laboratory measurements for determining irreducible water saturation take considerable time and money. For this reason available data may not cover all requirements, giving rise to the practise of using correlations to fill in gaps. Described in this paper are the reasons for irreducible water saturation being an elusive parameter that not only depends on pore structure characteristics but also the type of experiment and laboratory procedures, as well as changing plug conditions during experimentation. This paper reviews traditional methods, as well as recent and novel approaches to quality assure laboratory data and for correlating irreducible water saturation for prediction. To gain insight into the dependence of irreducible water saturation on detailed pore structure characteristics, most notably grain size and sorting, the usefulness of global characteristics envelopes is explored (Behrenbruch and Biniwale, 2005). In this multidimensional plot, irreducible water saturation is plotted against porosity, permeability, hydraulic radius, porosity group, flow zone indicator (grain size) and sorting, giving an insightful overview of the interdependence of parameters. The second part of this paper compares novel correlations with commonly used correlations. Traditional and more recent correlations are covered, from simple correlations versus the logarithm of permeability to more sophisticated approaches using more variables, including porosity and others. Most notably, it is shown that an approach of correlating irreducible water saturation with grain size (or flow zone indicator [FZI]) and sorting shows great promise. Data from two Australian fields are used to demonstrate the methodology, showing a significant increase in fitting accuracy. This approach may eventually lead to a universal correlation.

Wettability of Mississippian Barnett Shale samples at different depths: Investigations from directional spontaneous imbibition

Because of its significant impact on relative permeability, capillary pressure, stimulation methods, and ultimate recovery, the wettability of reservoir rocks is a critical factor of the petroleum recovery process. However, characterizing the wettability of shale with extremely low matrix permeabilities is a challenging task because of the dominant presence of nanopores in shale and high heterogeneity of shale compositions at multiple scales. From spontaneous imbibition behavior that uses two types of imbibing fluid (water and n-decane), the present study examines the wettability characteristics of gas-window Barnett Shale samples taken from four different depths of Texas United 1 Blakely core in Wise County in Texas. Imbibition experiments were conducted in two directions: parallel and transverse to the lamination of the samples. A scaling method was used to analyze imbibition data, and observed imbibition behaviors were interpreted to infer the different wettability conditions of four samples with different mineralogy, total organic carbon content, and pore-throat size distribution. Our results show that wettability significantly affects fluid imbibition behavior and that four tested samples can be divided into three wettability categories: more water wet, mixed wet, and more oil wet. Overall, the variable wettability of Barnett samples will affect hydrocarbon storage, distribution, and production.

Wettability alteration of oil-wet carbonate by silica nanofluid

Changing oil-wet surfaces toward higher water wettability is of key importance in subsurface engineering applications. This includes petroleum recovery from fractured limestone reservoirs, which are typically mixed or oil-wet, resulting in poor productivity as conventional waterflooding techniques are inefficient. A wettability change toward more water-wet would significantly improve oil displacement efficiency, and thus productivity. Another area where such a wettability shift would be highly beneficial is carbon geo-sequestration, where compressed CO2 is pumped underground for storage. It has recently been identified that more water-wet formations can store more CO2.We thus examined how silica based nanofluids can induce such a wettability shift on oil-wet and mixed-wet calcite substrates. We found that silica nanoparticles have an ability to alter the wettability of such calcite surfaces. Nanoparticle concentration and brine salinity had a significant effect on the wettability alteration efficiency, and an optimum salinity was identified, analogous to that one found for surfactant formulations. Mechanistically, most nanoparticles irreversibly adhered to the oil-wet calcite surface (as substantiated by SEM–EDS and AFM measurements). We conclude that such nanofluid formulations can be very effective as enhanced hydrocarbon recovery agents and can potentially be used for improving the efficiency of CO2 geo-storage.

Unsteady and porous media flow of reactive non-Newtonian fluids subjected to buoyancy and suction/injection

Purpose– The purpose of this paper is to examine the unsteady pressure-driven flow of a reactive third-grade non-Newtonian fluid in a channel filled with a porous medium. The flow is subjected to buoyancy, suction/injection asymmetrical and convective boundary conditions.Design/methodology/approach– The authors assume that exothermic chemical reactions take place within the flow system and that the asymmetric convective heat exchange with the ambient at the surfaces follow Newton’s law of cooling. The authors also assume unidirectional suction injection flow of uniform strength across the channel. The flow system is modeled via coupled non-linear partial differential equations derived from conservation laws of physics. The flow velocity and temperature are obtained by solving the governing equations numerically using semi-implicit finite difference methods.Findings– The authors present the results graphically and draw qualitative and quantitative observations and conclusions with respect to various parameters embedded in the problem. In particular the authors make observations regarding the effects of bouyancy, convective boundary conditions, suction/injection, non-Newtonian character and reaction strength on the flow velocity, temperature, wall shear stress and wall heat transfer.Originality/value– The combined fluid dynamical, porous media and heat transfer effects investigated in this paper have to the authors’ knowledge not been studied. Such fluid dynamical problems find important application in petroleum recovery.

Chemical structure, property and potential applications of biosurfactants produced by Bacillus subtilis in petroleum recovery and spill mitigation.

Lipopeptides produced by microorganisms are one of the five major classes of biosurfactants known and they have received much attention from scientific and industrial communities due to their powerful interfacial and biological activities as well as environmentally friendly characteristics. Microbially produced lipopeptides are a series of chemical structural analogues of different families and, among them, 26 families covering about 90 lipopeptide compounds have been reported in the last two decades. This paper reviews the chemical structural characteristics and molecular behaviors of surfactin, one of the representative lipopeptides of the 26 families. In particular, two novel surfactin molecules isolated from cell-free cultures of Bacillus subtilis HSO121 are presented. Surfactins exhibit strong self-assembly ability to form sphere-like micelles and larger aggregates at very low concentrations. The amphipathic and surface properties of surfactins are related to the existence of the minor polar and major hydrophobic domains in the three 3-D conformations. In addition, the application potential of surfactin in bioremediation of oil spills and oil contaminants, and microbial enhanced oil recovery are discussed.