Migration, filling history and geochemical characteristics of Ordovician natural gases in the Tahe Oilfield, Tarim Basin, Northwest China

• Published in: Acta geochimica 2009-09, Vol.28 (3), p.299-307
• Main Authors: Wang, Jie, Liu, Wenhui, Qin, Jianzhong, Liu, Keyu, Gu, Yi
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Carbonate rocks; Earth and Environmental Science; Earth Sciences; Geochemistry; Hydrocarbons; Hydrogen sulfide; Maturity; Metamorphism; Natural gas; Oil and gas fields; Oil fields; Ordovician; Studies; 地球化学特征; 塔河油田; 塔里木盆地; 天然气发电; 奥陶系; 烃类气体
• ISSN: 1000-9426; 2096-0956; 1993-0364; 2365-7499
• DOI: 10.1007/s11631-009-0299-z

Ordovician natural gases in the Tahe Oilfield are composed predominantly of hydrocarbon gases dominated by methane with a significant amount of heavy hydrocarbon gas component. The non-hydrocarbon gases include N2, CO2 and minor H2S. The Ordovician natural gases are believed to have originated from the same source rocks, and are composite of gases differing in thermal maturity. Carbon dioxide was derived from thermal metamorphism of Ordovician carbonate rocks. The generation of natural gases involves multiple stages from mature normal oil and condensate-associated gas to thermally cracked gas at the maturity to over-maturity stages. In the main part of the Tahe Oilfield, the Ordovician natural gases appear to be filled in two major phases with a typical petroleum-associated gas from southeast to northwest and from east to west in the early stage; and a thermally cracked gas from east to west in the late stage. At the same time, the oil/gas filling boundary has been primarily established between the two stages.