--> Abstract: Maturity Assessment Of Natural Gas In Tarim Basin: CH4/N2Ratio As A Tool; #90063 (2007)

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Maturity Assessment Of Natural Gas In Tarim Basin: CH4/N2Ratio As A Tool

 

Liu, Quanyou1, Bernhard M. Krooss2, Jinxing Dai1, Wenhui Liu3, Ralf Littke4 (1) Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, China (2) Lehrstuhl für Geologie, Geochemie und Lagerstätten des Erdöls und der Kohle, RWTH-Aachen, Aachen, Germany (3) Exploration and Production Research Institute, SINOPEC, Beijing, China (4) Technical University of Aachen (RWTH), D-52056 Aachen, Germany

 

In this context, the bulk ratio of CH4 / N2 is examined here as potential alternative geochemical parameter for the assessment of gas sources and maturity and compared to other previously used methods of maturity assessment of natural gas. Open-system non-isothermal pyrolysis of the low-mature coal from Manjiaer Sag, Tarim Basin yielded generation curves for CH4 and N2. Analysis of the change of vitrinite reflectance indicated a two-stage process of of thermal maturation with increasing temperatures. The relation between Ro and pyrolysis temperature could be expressed by the following equations: Stage I : Ro = 0.0014T + 0.109, r2 = 0.9931(Ro<0.6%); Stage II: Ro = 0.0067T - 1.5855, r2 = 0.9996(Ro>0.6%). A kinetic interpretation of nitrogen and methane generation characteristics of humic coal during laboratory pyrolysis indicates that the bulk ratios of methane and nitrogen as thermal maturity parameter may be applied to assess the maturity of gas-sources. Thus, the maturity of the source rocks of natural gases in Tarim Basin was expressed in terms of the CH4/N2 ratios and compared with other geochemical natural gas parameters, such as stable isotopes. The predicted results were found to correlate well with published data of gas-source maturity in these basins.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California