Journal de géologie et géophysique
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Evaluation of the Quantitative Criteria of Triassic Carbonate Rocks Reservoirs

Sudad H Al-Obaidi*, Wj Chang

South Mangyshlak basin is investigated in this paper. The Triassic deposits of carbonate rocks are investigated in this paper for their boundary values. These values are important for the interpretation of field geophysical data, as well as for perforation and blasting.

Triassic deposits, due to their lithological composition, are classified as either terrigenous or carbonate reservoirs. Carbonate reservoirs are found in the Middle Triassic strata containing volcanogenic dolomite and volcanogenic limestone rocks. These rocks create a complex type of reservoir that is characterized as porous-fractured, porouscavernous, and fractured. The intercalation of tuffaceous, siltstone-sandy, and mudstone rocks create the Upper Triassic sediments which overlie Middle Triassic sedimentary rocks. Oil deposits are confined to polymictic sandstones, which are saturated with oil to varying degrees.

In order to substantiate the quantitative criteria of the reservoir, experimental studies of the core samples were conducted in the laboratory. Studies of fluid flow were conducted where physical and hydrodynamic characteristics were determined when oil was displaced by displacing reagents. Correlations between reservoirs and non-reservoirs were constructed based on the obtained parameters. The boundary values were determined based on relationships between reservoir properties, such as porosity and permeability versus residual water content, as well as effective porosity and permeability versus dynamic porosity. Using these results, the porosity limits for the Middle and Upper Triassic strata have been determined to be 7%, the permeability limits for the Middle Triassic have been determined to be 0.02 × 10-3 m2, and the permeability limits for the Upper Triassic have been determined to be 0.3 × 10^-3 m².