A Comparison of the Geochemical Characteristics of Ultra-Deep Natural Gas in the Kuqa Foreland and Marine Craton Areas in the Tarim Basin, China

This research analyzed the composition and hydrocarbon isotope geochemical characteristics of ultra-deep natural gas (buried deeper than 6000 m) in more 130 wells Tarim Basin. Characteristics components Basin are as follows: Kuqa sandstone reservoir is developed dry gas, with a high methane content (an average 95.53%) low ethane only 1.39%). The marine craton carbonate reservoirs North Tarim-Central Tarim-East area wet gas. It mainly composed ranging from 56.1% to 98.8%, an 76.36% also contains small amount amounting 6.74%. CO 2 H S contents condensate Central high, maximum values 24.2% 23.1%, respectively. Isotopic δ 13 C 1 distributed between −36‰ −25.3‰, −28.2‰, −26.2‰ −13.8‰, −18.3‰. Most samples reversal carbon isotopic series > 3 , CO2 −19.5‰ −10.3‰. rocks −54.4‰ −33.3‰, −42.6‰. −41.1‰ −29.4‰, −33.8‰, −28.2‰–0.6‰. According identification chart, it can be seen that foreland coal-derived over-mature stage, may caused by mixing same type different sources. oil-type complex sources, including both kerogen cracking oil formed organic inorganic genesis. Inorganic most likely generated dissolution under acid formation water.