Determination of physicochemical properties and API of Asmari reservoir in Ahvaz oil field using petroleum inclusions study

Document Type : Original Article


1 Department of Geology, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran

2 Petroleum Geology and Sedimentary Basins Department, Faculty of Earth Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran

3 National Iranian South Oil Company, Ahvaz, Iran


Introduction: Fluid inclusions provide valuable evidence of the formation temperature of minerals, the pressure on their formation environment, the fluids densities that make up the minerals, and the chemical composition of the mineralizing fluids. This data can be used to interpret temperature history, maturity, determination of diagenetic environment, cementation timing, and hydrocarbon migration related to burial history.
Materials and methods: In this study, 19 double-polished sections prepared from Asmari reservoir cores of 7 wells from Ahvaz field (AZ) were used. After the preliminary investigation, 54 fluid inclusions were selected for microthermometric studies. All microthermometric data were obtained using cooling and heating operations on the involved fluids using a Linkam THMSG 600 model stage placed on an Olympus microscope. In addition, in order to determine the amount of UV reflection in the fluids involved, the U-RFL-T model UV light source placed on the Olympus microscope was used. LABRAM model (ISA Jobin Yvon) of Montanuniversitat University was used to perform laser Raman spectroscopy analysis.
Results and discussion: Petrographic studies: All the samples were subjected to petrography study, which is in terms of the types of single-phase gas, single-phase liquid, two-phase liquid-rich (oil) intermediates. In terms of origin, it can be seen in different and varied types, primary and secondary false.
Microthermometric studies: The homogenization temperature of fluid inclusions is between 50 and 362 degrees Celsius. The samples of the Asmari reservoir show the melting temperature of the last ice crystal between -22 and 13.9. The degree of salinity is calculated to be 0.16 to 35% by weight equivalent to table salt.
API study: 54 fluid inclusions selected from the Asmari reservoir in Ahvaz field were analyzed by API. The frequency of reflective color is related to green with a value of 55%, (30-40 API degrees) has a density of 0.82 to 0.74 g/cm3, which generally indicates oil with a light density. and the value of 40% belongs to blue color (40-50 API degree), which indicates a density of less than 0.74 g/cm3, is considered an extremely light oil. and only 5% of these colors belong to the yellow color (20-30 API degree), which indicates the density of 0.9 to 0.82 g/cm3, it is considered a medium density oil.
Raman spectroscopy: The calculation of liquid phase salinity in petroleum inclusions cargoes using the Raman laser spectroscopy method is dependent on the geometric shape of the spectrum obtained from the liquid phase present in the petroleum inclusions. According to the Cauchy-Lorentz scattering, the Raman spectrum for pure water shows three peaks at cm-13220, cm-13433 and cm-13617.
Conclusion: Based on the physicochemical properties of the Asmari reservoir, it shows two temperature ranges, which can be concluded that this reservoir was charged during two phases in two different time periods. One of the reasons confirming this conclusion can be mentioned that the oil of this reservoir has two origins. Also, based on the composition of the phases in the fluid inclusions (two-phase, three-phase with oil, etc.), it is possible to predict the path of charging the reservoir.


Main Subjects

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