An active strain of anaerobic thermophilic bacteria was isolated from the environment of the United Arab Emirates. This project studied the effect of temperature, salinity and oil concentration on biodegradation of crude oil. Oil weight loss, microbial growth and the changes of the crude oil asphaltene concentration are used to evaluate the oil degradation by this strain. A series of batch experiments was performed to study the effects of bacteria on the degradation of crude oil. The effects of oil concentration, bacteria concentration, temperature and salinity on the biodegradation were investigated. The temperatures of the studied systems were varied between 35 and 75°C and the salt concentrations were varied between 0 and 10%. Oil concentrations were ranged from 5 to 50% by volume. Experimental work showed the bacteria employed in this project were capable of surviving the harsh environment and degrading the crude oil at various conditions. Increasing the temperature increases the rate of oil degradation by bacteria. Increasing the oil concentration in general decreases the rate of bacteria oil degradation. Salinity plays a major role on the acceleration of biodegradation process of crude oil. An optimum salinity should be determined for every studied system. The finding of this project could be used in either the treatment of oil spill or in-situ stimulation of heavy oil wells.

The effect of injection brine salinity on the displacement efficiency of low water salinity flooding was investigated using sea water at 35,000 ppm, and two field injection waters, namely, Um-Eradhuma (UER) at 171,585 ppm and simsima (SIM) at 243,155 ppm. The salinity of the employed waters was varied from original salinity to 1,000 ppm and used in the displacement of oil in selected core samples. The results of this set of experiments revealed that UER salinity of 5,000 ppm is the optimum system for the candidate reservoir. UER original water and its optimum water were then used in this project as the high and low salinity waters in the CO₂–WAG flooding experiments. Displacement efficiencies were evaluated under three injection modes: carbon dioxide WAG miscible flooding (CO₂–WAG, 1:1, 2:1, and 1:2), continuous CO₂ injection, and waterflood. The WAG performance parameters, such as secondary and tertiary displacement efficiencies, CO₂ flood utilization factor, and CO₂ performance during different WAG flood cycles were determined. To insure miscibility condition between the injected gas and the employed oil, all of the flooding experiments were conducted at 3,200 psia (which is 300 psia above the minimum miscibility pressure of CO₂ and used oil) and 250 °F. Experimental results indicated that core length is a critical parameter in determining the optimum WAG process, and that a minimum core length of 29 cm is required to insure the generation of miscibility before breakthrough in CO2–WAG flooding experiments. On the other hand, core length had no effect on the performance of the low salinity flooding experiments. Using single core flooding low salinity CO₂–WAG of 1:2 flooding produced an improvement in the displacement efficiency of 29 % over the high salinity system. Also, composite core flooding experiments showed that the high salinity CO₂-2:1 WAG achieved a displacement efficiency of 98 %. These results indicate that achieving miscibility at the reservoir conditions is the dominant mechanism and that low salinity will have no major effect on the displacement efficiency of CO₂-Miscible WAG flooding. Results also indicate that oil recovery during different CO2–WAG cycles is a function of WAG ratios.

This experimental assessment was carried out to study the viscoelastic performance of crude oil-xanthan emulsions employing a RheoStress RS100 rheometer. Crude oil with a concentration range of 0–75% by volume was used to prepare the oil-gum emulsions. Two xanthan gums of Sigma and Kelzan were added in the emulsions with concentration ranges of 0–10⁴ ppm. The linear viscoelastic ranges of all the tested oil-gum emulsions were found in the range of 0.1–10 Pa. Thus, the experimental tests were completed within the linear viscoelastic range of 1 Pa. The complex modulus increased gradually and steadily with frequency and gum concentration for all the examined emulsions. The addition of crude oil into the lighter xanthan concentration of <10³ ppm provided almost the same behavior as the xanthan solution, whereas the presence of crude oil within the higher xanthan concentrations significantly stimulated the measured values of the complex modulus. For lower gum concentrations of up to 1000 ppm, oil concentration displayed no effect on both the storage and loss moduli, whereas for gum concentrations higher than 1000 ppm, both moduli increased gradually with crude oil concentration.

The experimental study of the Creep-recovery examination is necessary to understand the viscoelastic behavior of crude oil-Xanthan gum emulsions. The experimental measurements and analysis of these tests were completed using RheoStress RS100 under controlled stress CS-mode. Rheometers with CS-mode allow for a useful and direct technique for the experimental measurements of creep and recovery stages. This investigation covers a wide range of crude oil concentration of 0–75% by volume, Xanthan concentration range of 0–10⁴ ppm, and two types of Xanthan gums are used and investigated. The creep-recovery measurements of crude oil-Xanthan gums emulsions were extensively investigated. It was important to find the linear viscoelastic range for the examined crude oil-Xanthan gum emulsions. The experimental measurements and analysis of the creep-recovery examinations showed that the linear viscoelastic range was up to 1 Pa. The experimental investigation showed that the higher the concentration of the used gum and crude oil, the lower the compliance of the emulsions. For the Xanthan concentrations of less than 10³ ppm, the crude oil-gum emulsion exhibited viscous behavior. However, for the Xanthan concentration of higher than 10³, the examined emulsions displayed viscoelastic behavior.

While the “low salinity waterflooding” (LSWF) has been praised for enhancing oil recovery from different core rocks, the performance of the technique in different wettability environments remains unclear. The consensus is that LSWF does not work well in water-wet carbonate oil reservoirs. The main research objective was to determine the effect of LSWF on the displacement efficiency (DE) in different wettability environments. Carbonate core flooding experiments on rocks with different wettabilities were performed at in-situ reservoir conditions using seawater as a “base water”. Seawater was sequentially diluted 10 to 50 times and spiked 2 and 6 times with sulfate. Following sequential flooding with four different waters, the DEs were measured for different wettabilities. Five different sequential brine floodings were performed on carbonate rocks. Results indicated that optimum low salinity water is a function of system wettability. Seawater (≈ 50,000 ppm) is the optimum brine for oil-wet and intermediate-wettability systems. Sequential flooding consisting of seawater followed by diluted seawater in a water-wet system yielded the highest DE of 88%. Besides, low-salinity brine followed by sulfate performed better in a water-wet environment than in oil- and intermediate-wettability systems.