Ali S. Al-Bemani

Biosurfactant production by Bacillus subtilis B30 and its application in enhancing oil recovery

The fermentative production of biosurfactants by Bacillus subtilis strain B30 and the evaluation of biosurfactant based enhanced oil recovery using core-flood were investigated. Different carbon sources (glucose, sucrose, starch, date molasses, cane molasses) were tested to determine the optimal biosurfactant production. The isolate B30 produced a biosurfactant that could reduce the surface tension and interfacial tension to 26.63±0.45 mN/m and 3.79±0.27 mN/m, respectively in less than 12h in both glucose or date molasses based media. A crude biosurfactant concentration of 0.3-0.5 g/l and critical micelle dilution (CMD) values of 1:8 were observed. The biosurfactants gave stable emulsions with wide range of hydrocarbons including light and heavy crude oil. The biosurfactants were partially purified and identified as a mixture of lipopeptides similar to surfactin, using high performance thin layer chromatography and Fourier transform infrared spectroscopy. The biosurfactants were stable over wide range of pH, salinity and temperatures. The crude biosurfactant preparation enhanced light oil recovery by 17-26% and heavy oil recovery by 31% in core-flood studies. The results are indicative of the potential of the strain for the development of ex situ microbial enhanced oil recovery processes using glucose or date molasses based minimal media.

Residual-Oil Recovery Through Injection of Biosurfactant, Chemical Surfactant, and Mixtures of Both Under Reservoir Temperatures: Induced-Wettability and Interfacial-Tension Effects

In this study, a biosurfactant produced by a Bacillus subtilis strain isolated from oil-contaminated soil from an Omani oil field was tested for its potential in enhancing oil recovery by a series of coreflooding experiments. It was found that the performance of the biosurfactant was increased by mixing with chemical surfactants, by which the maximum production went up to 50% of residual oil at a mixing ratio of (50:50). The second objective of this study was to investigate the effects of the biosurfactant on wettability alteration and to estimate its tendency to loss caused by adsorption. The influence of biosurfactant on wettability was studied by contact-angle measurements, atomic force microscopy (AFM) technique on few-layer graphene (FLG) surfaces, and Amott wettability tests on Berea sandstone cores. Contact-angle measurements showed that the wettability of the biosurfactant solution changes to more oil-wet as the angle decreased from 70.6 to 25.32° when treated with 0.25% (w/v) biosurfactant solution. Amott testing showed a change in wettability index from strongly water-wet in the untreated core toward less water-wet in biosurfactant-treated cores. These results confirmed the ability of the biosurfactant to alter the wetting conditions against different surfaces, thereby serving as a mechanism for enhancing oil recovery. The maximum loss of biosurfactant caused by adsorption was 1.2 mg/g of rock, which is comparable with reported chemical-surfactant values.

Microbial enhanced heavy oil recovery by the aid of inhabitant spore-forming bacteria: an insight review.

Crude oil is the major source of energy worldwide being exploited as a source of economy, including Oman. As the price of crude oil increases and crude oil reserves collapse, exploitation of oil resources in mature reservoirs is essential for meeting future energy demands. As conventional recovery methods currently used have become less efficient for the needs, there is a continuous demand of developing a new technology which helps in the upgradation of heavy crude oil. Microbial enhanced oil recovery (MEOR) is an important tertiary oil recovery method which is cost-effective and eco-friendly technology to drive the residual oil trapped in the reservoirs. The potential of microorganisms to degrade heavy crude oil to reduce viscosity is considered to be very effective in MEOR. Earlier studies of MEOR (1950s) were based on three broad areas: injection, dispersion, and propagation of microorganisms in petroleum reservoirs; selective degradation of oil components to improve flow characteristics; and production of metabolites by microorganisms and their effects. Since thermophilic spore-forming bacteria can thrive in very extreme conditions in oil reservoirs, they are the most suitable organisms for the purpose. This paper contains the review of work done with thermophilic spore-forming bacteria by different researchers.

Sophorolipids Production by Candida bombicola ATCC 22214 and its Potential Application in Microbial Enhanced Oil Recovery

Biosurfactant production using Candida bombicola ATCC 22214, its characterization and potential applications in enhancing oil recovery were studied at laboratory scale. The seed media and the production media were standardized for optimal growth and biosurfactant production. The production media were tested with different carbon sources: glucose (2%w/v) and corn oil (10%v/v) added separately or concurrently. The samples were collected at 24 h interval up to 120 h and checked for growth (OD660), and biosurfactant production [surface tension (ST) and interfacial tension (IFT)]. The medium with both glucose and corn oil gave better biosurfactant production and reduced both ST and IFT to 28.56 + 0.42mN/m and 2.13 + 0.09mN/m, respectively within 72 h. The produced biosurfactant was quite stable at 13–15% salinity, pH range of 2–12, and at temperature up to 100°C. It also produced stable emulsions (%E24) with different hydrocarbons (pentane, hexane, heptane, tridecane, tetradecane, hexadecane, 1-methylnaphthalene, 2,2,4,4,6,8-heptamethylnonane, light and heavy crude oil). The produced biosurfactant was extracted using ethyl acetate and characterized as a mixture of sophorolipids (SPLs). The potential of SPLs in enhancing oil recovery was tested using core-flooding experiments under reservoir conditions, where additional 27.27% of residual oil (Sor) was recovered. This confirmed the potential of SPLs for applications in microbial enhanced oil recovery.

Applicability of Sachdeva's Choke Flow Model in Southwest Louisiana Gas Condensate Wells

Sachdeva’s multiphase choke flow model has capabilities of predicting critical-subcritical boundary and liquid and gas flow rates for given upstream and downstream pressures. Although this model was shown to be accurate by Sachdeva et al. in their original paper using laboratory and field data, inaccuracy of the model has been found in other field applications. It is highly desirable for production engineers to find the applicability of this model when it is applied to gas condensate wells. In this study, the accuracy of the Sachdeva’s choke model was evaluated using data from oil and gas condensate wells in Southwest Louisiana. Comparisons of the results from the model and field measurements indicate that Sachdeva’s choke model generally under-estimates gas and condensate flow rates. Based on measurements from 239 gas condensate wells it was found that the model under-estimates gas rate and liquid rate by as much as 40% and 60%, respectively. The model also failed to calculate mass flow rates for 48 condensate wells where relatively low-pressure differentials at chokes and highflow rates were observed. The investigation further went on to improve the performance of Sachdeva’s choke model. It was found that the error of the model could be minimized using different values of choke discharge coefficient (CD). For gas condensate wells, the error in gas flow rate calculations can be minimized using CD = 1.073. However, the error in liquid flow rate calculations for condensate wells is minimum when CD = 1.532.

Improvement in Sachdeva's Multiphase Choke Flow Model Using Field Data

Wellhead chokes are equipment used in the oil and gas industry to control fluid production rates from wells, to maintain stable pressure downstream from the choke and to provide the necessary backpressure to a reservoir to avoid formation damage from excessive drawdown. Because oil and gas production rates are extremely sensitive to choke size, accurate modelling of choke performance is vitally important for petroleum engineers in oil production simulation. Tangren et al.(1) performed the first investigation on gas-liquid two-phase flow through restrictions. They presented an analysis of the behaviour of an expanding gas-liquid system. They showed that when gas bubbles are added to an incompressible fluid above a critical flow velocity, the medium becomes incapable of transmitting a pressure change upstream against the flow. Several empirical choke flow models have been developed in the past half century. They generally take the following form for sonic flow:

Production, Characterization, and Application of Bacillus licheniformis W16 Biosurfactant in Enhancing Oil Recovery

The biosurfactant production by Bacillus licheniformis W16 and evaluation of biosurfactant based enhanced oil recovery (EOR) using core-flood under reservoir conditions were investigated. Previously reported nine different production media were screened for biosurfactant production, and two were further optimized with different carbon sources (glucose, sucrose, starch, cane molasses, or date molasses), as well as the strain was screened for biosurfactant production during the growth in different media. The biosurfactant reduced the surface tension and interfacial tension to 24.33 ± 0.57 mN m−1 and 2.47 ± 0.32 mN m−1 respectively within 72 h, at 40°C, and also altered the wettability of a hydrophobic surface by changing the contact angle from 55.67 ± 1.6 to 19.54°± 0.96°. The critical micelle dilution values of 4X were observed. The biosurfactants were characterized by different analytical techniques and identified as lipopeptide, similar to lichenysin-A. The biosurfactant was stable over wide range of extreme environmental conditions. The core flood experiments showed that the biosurfactant was able to enhance the oil recovery by 24–26% over residual oil saturation (Sor). The results highlight the potential application of lipopeptide biosurfactant in wettability alteration and microbial EOR processes.

The application of air-sparging, soil vapor extraction and pump and treat for remediation of a diesel-contaminated fractured formation

Abstract The present study addresses the efficiency of an integrated air sparging, soil vapor extraction, and pump and treat system in the remediation of a diesel contaminated site in Oman. Cleanup efforts have targeted groundwater and soil in fractured formations. Site hydrogeological characterization was conducted including sampling and analysis of water and soil. Within seven months of the start of the treatment system, benzene gas in the unsaturated zone fell from an initial range of 15–60 ppm to below detection level, while total petroleum hydrocarbon in the groundwater dropped from 25–50 ppm to less than 0.5 ppm. Treatment processes have ceased while groundwater and soil are being monitored. Thus far, benzene gas has been undetected for the past 18 months, but total petroleum hydrocarbon in groundwater has rebounded to 1.2 ppm during the last four months.

VISCOSITY OF WATER-OIL EMULSIONS WITH ADDED NANO-SIZE PARTICLES

The viscosity of emulsion and suspensions in the presence of two types of nano-size particles that, have different affinity for oil, have been investigated. It has been found out that both oil-solid suspensions and oil-water-solid mixtures behave as pseudoplastic fluids at all studied solid concentrations. The viscosity of emulsion-solid mixtures does not seem to get affected by water concentration, yet it is a function of solid concentration. The ability of solids to act as emulsifying agents has also been investigated. It has been established that neither of the two types of solids used is capable of stabilizing water-in-oil or oil-in-water emulsions in the absence of surfactants. At low concentrations of solids and in the presence of an oil-soluble surfactant, both oil-wet and water-wet solids, however, are capable of stabilizing water-in-oil emulsions. In the presence of water-soluble surfactant, only water-wet solids are capable of stabilizing oil-in-water emulsions.

ESTABLISHING PVT CORRELATIONS FOR OMANI OILS

An adequate knowledge of any reservoir fluid PVT properties is essential for most types of petroleum calculations. These calculations include amount of oil in the reservoir, production capacity, variations in produced gas-oil ratio during the reservoirs production life, calculation of recovery efficiency, reservoir performance, production operations and the design of production facilities. PVT properties can be measured experimentally by using collected bottom-hole or surface samples of crude oils. But, the experimental determination of PVT is time consuming and very costly. In addition, even with the availability of PVT analyses, it is often necessary to extrapolate the data to field and/or surface conditions through the use of empirical correlations. Furthermore, geological and geographical conditions are considered very critical in the development of any correlation. But, universal correlations are difficult to develop. That is why correlations for local regions, where crude properties are expected to be uniform, is a reasonable alternative. In this study, experimental PVT data for North and South Oman crudes, statistical and artificial neural network (ANN) analyses are used to develop reliable PVT correlations. Comparisons with previously published correlations are presented.