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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]

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]

The Kuqa depression is an important oil and gas production area in western China, and there are abundant natural gas resources in the deep and ultra‐deep tight reservoirs. In this study, the accumulation law of deep oil and gas in the Kuqa depression has been systematically discussed based on the analysis of geochemical parameters, reservoir fluid inclusions and the recovery of burial‐thermal evolution history in different structural zones. The results show that the lacustrine mudstones of the Triassic Huangshanjie and Upper Jurassic Qiakemake formations in the Kuqa depression are the main oil‐generating source rocks, and the coal‐measure source rocks of the Middle and Lower Jurassic are the main gas‐generating source rocks. The oil and gas in the northern tectonic belt originated from the Huangshanjie and Yangxia formations have the characteristics of 'lower‐source and upper‐reservoir' and 'self‐generation and self‐storage'. The source rocks in the central tectonic belt are of high maturity and mainly generate natural gas, and a small amount of crude oil is derived from mudstones of the Jurassic Qiakemake Formation. The oil and gas in the southern slope belt are mainly derived from the source rocks of the Huangshanjie Formation, followed by the Jurassic source rocks. The ordered accumulation of oil and gas in the Kuqa depression is controlled by the effective spatiotemporal matching of multi‐stage tectonic evolution and hydrocarbon generation evolution of multi‐source rocks. Three spatiotemporal ordered hydrocarbon accumulation series have been proposed: early near‐source accumulation, late far and near‐source accumulation, and late upper‐near source accumulation. The piedmont belt is dominated by the near‐source continuous accumulation mode, the thrust belt is dominated by the ultra‐late upper source accumulation mode, and the slope belt is dominated by the late far‐source accumulation mode. Therefore, future exploration will focus on the tight lithologic reservoirs in the northern piedmont belt, the structural reservoirs in the central structural belt, and the unconformity hidden reservoirs in the southern slope belt. [ABSTRACT FROM AUTHOR]

Terrestrial gas-prone source rocks are significant for hydrocarbon gas accumulations especially in central and western basins in China. The Kuqa foreland basin in the northern margin of the Tarim Basin, NW China is rich in natural gas with recent discoveries of several large to giant gas-producing fields (e.g., the Kela-2, Dibei, Dabei-1, and Zhongqiu-1 gas fields, etc.) and a proven 3 P gas reserve of over one trillion cubic meters (TCM). This proliferous petroleum province is powered by an effective and diverse gas-prone source rock series in the basin comprising mudstone, carbonaceous mudstone, and coal seams. To date, little systematic research work has been done on the petroleum generation potential of the source rocks. This has seriously restricted the assessment of petroleum resources and further exploration in the frontier areas of the basin. A sealed gold tube pyrolysis approach was employed to simulate the oil and gas generation and cracking yields for the aforementioned three types of source rock. Compared with typical Type I and II 1 kerogens, the three types of source rocks in the Kuqa foreland basin are characterized by (1) far less hydrocarbon yield (150 mg/g TOC) with comparatively larger amounts of CO 2 (310 mg/g TOC), (2) a limited capacity and narrower window (0.5%–1.08% Ro) for oil generation, and (3) a much earlier secondary cracking for bulk oil to light oil and gases (>0.86% Ro for mudstone and >1.08% Ro for both carbonaceous mudstone and coal). All the source rocks are gas-prone, and significant amount of gas can still be generated during an over-mature stage. The kinetic parameters obtained allow us to model hydrocarbon generation in the Kuqa foreland basin more realistically. It is concluded that (1) two episodes of hydrocarbon generation occurred with hydrocarbon gases being mainly generated during the later stage (12–3 Ma); and (2) the depocenter of the basin is capable of supplying massive high-mature gases as late as in the Quaternary, which is crucial for the formation of giant gas fields. The findings provide new insight on the reconstruction of oil and gas accumulation processes and further hydrocarbon exploration in the basin. • Three typical terrestrial gas-prone source rocks were selected to determine and compare their oil and gas yields. • Both the generative and cracking kinetic parameters of the three source rocks were calculated. • Terrestrial gas-prone source rocks have different hydrocarbon generation characteristics comparing with typical Type I and II2 kerogens. • Evolution of hydrocarbon generation and cracking was constructed in the Kuqa foreland basin. [ABSTRACT FROM AUTHOR]