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The Kuqa Depression is rich in oil and gas resources and serves as a key production area in the Tarim Basin. However, controversy persists over the genesis of oil and gas in the various structural zones of the Kuqa Depression. This study employs natural gas composition analysis, gas carbon isotope analysis and gold pipe thermal simulation experiments, to comprehensively analyze the differences in the genesis and sources of hydrocarbon gas fluid from the eastern and western Kuqa Depression. The results show that the Kuqa Depression is dominated by alkane gas, with an average gas drying coefficient of 95.6, with nitrogen and carbon dioxide as the primary non-hydrocarbon gases. The average of δ13C1, δ13C2 and δ13C3 values in natural gas are −27.70‰, −20.43‰ and −21.75‰, respectively. Based on comprehensive natural gas geochemical maps, the CO2 in the natural gas from the Tudong and Dabei areas, as well as the KT-1 well of the Kuqa Depression, is thought to be of organic origin. Additionally, natural gas formation in the Tudong area is relatively simple, consisting entirely of thermally generated coal gas derived from the initial cracking of kerogen. The natural gas in the KT-1 well and the Dabei area are mixed gasses, formed by the initial cracking of kerogen from highly evolved lacustrine and coal-bearing source rocks, exhibiting characteristics resembling those of crude oil cracking gas. The methane (CH4) content of natural gas in the Dabei area is high and the carbon isotopes are unusually heavy. Considering the regional geological background, potential source rock characteristics and geochemical features may be related to the large-scale invasion of dry gas contributed by CH4 from highly evolved, underlying coal-bearing source rocks. Consequently, the CH4 content in the mixed gas is generally high (Ln (C1/C2) can reach up to 5.38), while the relative content of heavy components is low, though remains relatively unchanged. Thus, the map of the relative content of heavy components still reflects the characteristics of the original gas genesis (initial cracking of kerogen). Mixed-source gas was analyzed using thermal simulation experiments and natural gas composition ratio diagrams. The contributions of natural gas from deep, highly evolved coal-bearing source rocks in the KT-1 well and the Dabei area accounted for more than 90% and approximately 60%, respectively. This analysis provides theoretical guidance for natural gas exploration in the research area. [ABSTRACT FROM AUTHOR]

The deep Lower Jurassic Ahe Formation (J1a) in the Dibei–Tuzi area of the Kuqa Depression has not been extensively explored because of the complex distribution of fractures. A study was conducted to investigate the relationship between the natural fracture distribution and structural style. The J1a fractures in this area were mainly high‐angle shear fractures. A backward thrust structure (BTS) is favorable for gas migration and accumulation, probably because natural fractures are more developed in the middle and upper parts of a thick competent layer. The opposing thrust structure (OTS) was strongly compressed, and the natural fractures in the middle and lower parts of the thick competent layer around the fault were more intense. The vertical fracture distribution in the thick competent layers of an imbricate‐thrust structure (ITS) differs from that of BTS and OTS. The intensity of the fractures in the ITS anticline is similar to that in the BTS. Fracture density in monoclinic strata in a ITS is controlled by faulting. Overall, the structural style controls the configuration of faults and anticlines, and the stress on the competent layers, which significantly affects deep gas reservoir fractures. The enrichment of deep tight sandstone gas is likely controlled by two closely spaced faults and a fault‐related anticline. [ABSTRACT FROM AUTHOR]

Helium is an irreplaceable ore resource for many applications, such as nuclear magnetic resonance, aviation, semiconductors, and nuclear energy. Extracting helium in a free state from natural gas is currently the only economical approach at the industrial level. In this study, we compiled geochemical data of 719 natural gas samples from 36 oil and gas fields in the Tarim basin that include experimental results and previously reported data. Helium is of primarily crustal origin in the Tarim Basin according to helium isotope characteristics (not exceeding 0.1 Ra), except in the Ake gas field that has not more than 7% of mantle helium. Helium concentrations in diverse tectonic units vary considerably. Oil-type gas, on the whole, has a higher helium concentration relative to coal-type gas. Abundant helium flux, a favorable fault system between the source-reservoir system, no strong charging of gaseous hydrocarbons, and the good sealing capacity are important factors that control the formation of helium-rich gas fields. Considering both the helium concentration and natural gas reserves, helium-rich gas fields located in the Southwest Depression and Tabei Uplift can be regarded as the major favorable zones of further deployment for helium extraction. [ABSTRACT FROM AUTHOR]

Gypsum caprocks' sealing ability is affected by temperature‐pressure coupling. Due to the limitations of experimental conditions, there is still a lack of triaxial stress‐strain experiments that simultaneously consider changes in temperature and pressure conditions, which limits the accuracy of the comprehensive evaluation of the brittle plastic evolution and sealing ability of gypsum rocks using temperature pressure coupling. Triaxial stress‐strain tests were utilized to investigate the differences in the evolution of the confinement capacity of gypsum rocks under coupled temperature‐pressure action and isothermal‐variable pressure action on the basis of sample feasibility analysis. According to research, the gypsum rock's peak and residual strengths decrease under simultaneous increases in temperature and pressure over isothermal pressurization experimental conditions, and it becomes more ductile. This reduces the amount of time it takes for the rock to transition from brittle to plastic. When temperature is taken into account, both the brittle–plastic transformation's depth limit and the lithological transformation of gypsum rocks become shallower, and the evolution of gypsum rocks under variable temperature and pressure conditions is more complicated than that under isothermal pressurization. The sealing ability under the temperature‐pressure coupling is more in line with the actual geological context when the application results of the Well #ZS5 are compared. This provides a theoretical basis for precisely determining the process of hydrocarbon accumulation and explains why the early hydrocarbon were not well preserved. [ABSTRACT FROM AUTHOR]

Biotic tissues are a kind of highly scattering random media; studies on laser light propagation in biotic tissues play an important role in bio-medical diagnostics and therapeutics. The propagation and distribution of infinitely narrow photon beam in tissues are simulated by Monte Carlo method in this paper. Also presented are the energy distribution with regard to depths, light distribution in tissues, reflection and transmittance on the upper and lower surface. The optical parameters adopted in this study are g, albedo and microa, which have influence on energy distribution. The results show: The energy distribution decreases more quickly with the increase of depths and reveals a peak value close to the surface; g factor plays an important part in the lost energy on the upper surface and lower surface; the decrease of g factor causes weaking of the forward moving ability, so the penetration depth becomes smaller and the energy becomes dispersives variation of albedo has distinct effect on the shallow and deep tissues.