Loading...

Experimental and Theoretical Investigation of Heavy Oil Recovery Using Chemical Flooding; Mechanistically Study

Dehghan, Ali Akbar | 2015

697 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46738 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Masihi, Mohsan; Ayatollahi, Shahaboddin
  7. Abstract:
  8. Chemical flooding has great potential to recover significant fractions of remaining oil for medium to heavy oil reservoirs not applicable for thermal recovery techniques. Nowadays, with gradual crude oil price increase the chemical process is receiving renewed attention, however, illustration of the possibility of various chemical injection scenarios for medium to heavy oil reservoirs has not been clearly reported and these kinds of reservoirs require more investigation for the applicability of these techniques in the fields. The interfacial active molecules are responsible for providing low IFT range and water/oil emulsions which in many cases could improve the oil displacement efficiency. However, the interaction behavior of these chemical mixtures for each set of crude oil/chemical composition is required to be investigated separately. A new-designed surfactant along with three other commercial anionic surfactants was prepared with capability of tolerating high saline formation water and real oil reservoir conditions. The compatibility state of these materials were initially investigated and the specific emulsion and phase behavior of the chemical solutions with a heavy crude oil were investigated by doing all sets of emulsion stability and emulsion behavior tests in presence of four different alkalis as Sodium Hydroxide, Sodium Carbonate, Sodium Metaborate, and Triethanolamine. The Interfacial Tension (IFT) measurements and analysis, wettability examination, various core flooding tests at two wetting conditions by mixtures of alkali-surfactant-polymer in saturated Berea core samples, capillary pressure versus saturation trend (CDC), and temperature dependency experiments for different mixtures of the provided alkali-surfactant mixtures were investigated throughout thorough number of experiments. Neural network modeling technique was used in the last section to investigate the possibility of the presence of any correlation between the effective experimental parameters and the final recovery during a sample chemical flooding experiments in core scale.The initial screening compatibility experiments with two different provided aqueous solutions showed some scales or two-phase states for NaOH and Na2CO3 salts while the two other ones represented acceptable results. While Sodium Metaborate and Triethanolamine did not remain any considerable precipitates, adding some percentages of the designed surfactant to alkaline solutions could recuperate parts of the deposited alkaline precipitates. The optimum phase behavior (lowest interfacial tension region) of the chemical combination was very dependent on the nature of the used components. Mixtures of the surfactants and alkalis gave the optimum three-phase region at high salinity conditions. Addition of alkalis in each case improved the emulsion generation capability of the surfactant mixtures. The solubilization-ratio for all set of the chemical mixtures were evaluated using the static bottle tests and the results showed a reasonable value for almost all the cases (values greater than 10) which reveals a promising condition for the generated emulsion positive role during chemical flooding in the oil reservoirs. The synergistic effect of the surfactants and in-situ soap generated as a result of alkali and acidic crude oil reaction made promising results for positive emulsion generation in a porous medium. At optimum states, solutions containing 0.5 wt% of alkalis and 0.2 wt% of the surfactants provide IFT values less than 0.005 mN/m. Increasing the temperature reduced the optimum salinity strength by weakening the effective electrostatic forces around the droplets. Although both contact angle and Amott cell experiments were performed to monitor the wettability change as a result of different chemical solutions, the results showed that the contact angle method would not be so trustable at conditions where the solution contains reactive materials. All the surfactant solutions could reduce the oil wet state of the core slices. Mixtures of the Sodium Metaborate and the surfactant as well as the Calcium and Magnesium ions could also improve the spontaneous recovery of the cores in both imbibition and drainage conditions.
    The dynamic interaction of the oil-chemicals in the core flooding experiments was also measured by monitoring the pressure drops, recovery pattern, and the effluent nature. The pressure responses and the produced liquids during the injection of the optimum surfactant-alkaline solutions were representative of a promising role during these chemical injections. Two last surfactant solutions that have higher optimum salinity values depicted more oil recovery during flooding at high salinity media. Flooding at all the oil wet core samples showed lower final oil recovery and lower pressure humps but the amount of the produced oil was more than the pure water flooding cases. The temperature influence on oil flooding were also showed that the micro-emulsion generation has a great role for heavy oil displacement in the porous media. It was shown that the remaining wetting phase saturation depends on capillary end effects at lower capillary numbers (high IFT flood); At higher capillary numbers (low IFT floods), the remaining wetting phase saturation was found to depend on both capillary numbers and on the number of injected pore volumes. The overall mechanistic results including the proper compatibility of the surfactants, proper optimum salinity range for alkalis-chemical solutions, high values for solubilization-ratio, low IFT range, and suitable recovery values during different flooding states introduced the chemical injection scenario as a favorable technique for better fluid displacement and more oil recovery in a porous media
  9. Keywords:
  10. Enhanced Oil Recovery ; Chemical Method ; Heavy Oil ; Alkaline-Surfactant-Polymer (ASP)Flooding ; Laboratary Study

 Digital Object List

 Bookmark

No TOC