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Vesiculate amygdaloidal basalt stands out as a recently recognized primary reservoir within Urho area, the northwestern periphery of Junggar Basin. Notably, a significant proportion of the volcanic rock-type oil and gas reservoirs discovered in this region is affiliated with the volcanic formations of Hala'alate Formation. Within this stratigraphic unit, a distinct segment characterized by vesiculate amygdaloidal basalt exhibits remarkable development, encompassing over 78% of the total thickness of the strata. This particular interval serves as an optimal candidate for in-depth studies on volcanic rock reservoir characteristics. The amygdaloid bodies in these basalts predominantly consist of secondary calcite, which demonstrates a high solubility in water. These amygdaloid bodies often assume circular to semi-circular configurations, with many interconnected in patterns resembling networks, branches, or irregular structures. Statistical analyses corroborate that subjecting these amygdaloid bodies to dissolution in wellbore fluids results in a significant increase in porosity, approximately ranging from 3.6 to 4.5 times, effectively rendering them highly favorable as reservoir lithology. A robust assessment of the reservoir quality considers three distinct parameters, including stomatal unit area proportion, the proportion of connectivity, and the proportion of porosity enhancement stemming from amygdaloid dissolution. When all three of these criteria achieve excellence, the reservoir attains a classification of excellent reservoir. Meanwhile, a classification of favorable reservoir is attributed when a minimum of two criteria reaches an excellent level. A prudent estimation indicates that over 50% of the 110 samples obtained from a dataset surpass the established criteria for a favorable reservoir, thus demonstrating a noteworthy potential for reservoir development. The above reservoir division scheme provides a reference for establishing comprehensive evaluation scheme of evaluating the reservoir performance specific to vesiculate amygdaloidal basalts. [ABSTRACT FROM AUTHOR]

Basaltic magma, which is found in whole process of plate tectonic evolution and the critical stages, is a most important tectonogeochemical indicator in all igneous rocks. Therefore, the diagrams and ratios of related elements in basalts become the first choice to investigate the igneous diagenesis and tectonic setting. Ta, Hf, Th, La, Zr and Nb, which are high-field strength elements and stronger incompatible elements, have similar geochemical properties and regular changes in basaltic diagenesis, thus, they are most frequently used in basalt genesis and discrimination diagrams of tectonic setting. Moreover, the ratios of contents between the each one of elements can better distinguish the tectonic settings of formation. Based on the double-log discrimination diagrams of Th/Hf-Ta/Hf, Th/Zr-Nb/Zr and La/Zr-Nb/Zr in basalt yielded by previous research, the ratios of Ta/Hf, Th/Ta, Th/Hf, Nb/Zr, Th/Nb, La/Nb values were proposed to distinguish the basalts in various common tectonic settings, and the ratio discrimination table was put forward. The table extremely distinguishes basalt in most common variety of tectonic environments and is a great supplement for the double-log discrimination diagrams. [ABSTRACT FROM AUTHOR]