Improving sweep efficiency from heterogenous reservoirs necessitates the injection of gel treatment and/or polymer solution to lower the degree of heterogeneity and to lower the mobility ratio, respectively. In this study, three gel systems were compared with partially hydrolyzed polyacrylamide (HPAM) solution. The purpose of this study was to show the ability of the viscoelastic properties of the HPAM to enhance the sweep efficiency compared to the selected gel systems. The model was one quarter of five- spot pattern with one injector and one producer. The injection rate was 525 bbl/day. The selected simulator to run the scenarios was UTGEL, while the selected gel systems were colloidal dispersion gel (CDG), polymer/chromium chloride gel, and polymer/chromium malonate gel. Two polymer concentrations (0.1 and 0.15 wt. %) were used and three salinities were considered (5000, 10,000, and 20,000 mg/l).
This study showed interesting results regarding the ability of the viscoelastic properties of the HPAM polymer solution to yield recovery factors close or similar to those recovery factors obtained from the selected polymer gel systems. The results also revealed that lowering the salinity of post-treatment water could boost the performance of the polymer solution and make the polymer flooding more effective than gel systems. The results also showed that regardless the duration of injecting the polymer gel system, the HPAM polymer solution still yielded promising results, particularly if low-salinity water was implemented after the treatment.
Almansour, Abdullah Owidah (King Abdulaziz City for Science & Technology Saudi Arabia and Missouri University of Science & Technology) | Al-Bazzaz, Waleed Hussien (Kuwait Institute For Scientific Research) | Saraswathy, Geetha (Kuwait Institute for Scientific Research) | Sun, Yongpeng (Missouri University of Science & Tech) | Bai, Baojun (Missouri University of Science & Tech) | Flori, Ralph E (Missouri University of Science & Tech)
Deep tar-mat layers, which occur between the aquifer column and the reservoir-oil column, contain substantial quantities of extremely heavy oil and are found in various parts of the world, most prominently in Middle Eastern nations such as Saudi Arabia, Qatar, south Iraq, and Kuwait. Tar mats are thick layers with oil gravity of less than 10 °API; they isolate conventional oil reservoirs from their aquifers either partially or completely, causing numerous problems when applying oil recovery technology. However, in this study, tar mats are considered as a potential source from which to extract difficult oil. Researchers have attempted to experimentally evaluate the effect of toluene, hot water, and surfactant solution extractions on several carbonate tar-mat rock samples at several different temperatures (25°C, 135°C, 225°C and 315°C). In the study presented in this paper, samples were selected from a tar-mat carbonate reservoir in Kuwait. The physical and chemical geneses of tar-mat oil were analyzed utilizing several experimental geochemical techniques, such as rock evaluation pyrolysis, liquid extracts for Saturates, Aromatics, Resins, and Asphaltenes (SARA analysis), and elemental fingerprinting of Carbon, Hydrogen, Nitrogen, Sulfur, and Oxygen (CHNSO). These geochemical techniques were integrated in order to quantitatively evaluate the tar-mat recovery patterns of the carbonate reservoir at different temperatures. The results showed that the oil recovery significantly increased as the temperature increased. A comparison of all three methods indicates that for light and heavy tar mats, toluene produced the highest oil recovery at all temperatures tested, reaching as high as 47.1% at 315 °C. The surfactant treatment yielded less oil recovery than toluene, which reached as high as 7.5% at 315 °C. The temperature had a significant effect on light tar-mat oil recovery when using water methods; the oil recovery reached as high as 6.2% when using water at 315 °C. However, high-temperature water had little effect on extremely heavy tar mats. The paper provides a systematic method by which to quantitatively characterize tar-mat crudes in carbonate reservoirs.