Geochemical characteristics of light hydrocarbons in natural gases from the Turpan-Hami Basin and identification of low-mature gas

Abstract

Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources. Light hydrocarbon parameters and C and H isotopes are useful tools to identify low-mature gas. Twenty gas samples were collected from the Turpan-Hami Basin for light hydrocarbon analyses. The results showed that the light hydrocarbon components of natural gases contain high methylcycloxane, high isoparaffin and low benzene. This implies that the gas-generating parent materials are of typical humus type and the paleoenvironment is a fresh water sedimentary environment. These features are consistent with the geological setting of the basin. Comparative studies of isoheptane, heptane, and the carbon isotopic compositions of methane in natural gases, and other maturity indices indicated that natural gases in the Turpan-Hami Basin are dominated by low-mature gas formed during the low evolution stage of Jurassic coal seams. The parent materials are of type III, and the maturation degree was in the low evolution stage. These are the fundamental characteristics of low-mature gas. Results of light hydrocarbon research provided further evidence to suggest that the Turpan-Hami Basin is a large-scale gas producer of low-mature gas in China. It is likely that this resource will play an important role in future exploration and development of low-mature gas in China. Turpan-Hami Basin, low-mature gas, light hydrocarbon component, humus Citation:Shen P, Wang X F, Wang Z Y, et al. Geochemical characteristics of light hydrocarbons in natural gases from the Turpan-Hami Basin and identification of low-mature gas.

Light Hydrocarbon (C5–C7) Geochemistry in the Northern Margin of the Qaidam Basin, Northeastern Tibetan Plateau: Gas Mixing and Hydrocarbon Charge History

“…Figure presents the compositions of C 5 –C 7 light hydrocarbons in ternary diagrams. Previous studies found that light hydrocarbons produced by sapropelic organic matter are abundant in n -alkanes, whereas those generated by humic organic matter are abundant in iso -alkanes and cyclo -alkanes. − Figure a shows that gases in Jianbei, Niudong, Kunteyibei, Lenghu no. 4 and Nanbaxain fields have higher contents of iso -C 5–7 than n -C 5–7 , indicating a greater contribution from humic organic matter, while gases in Dongping, Lenghu no.…”

Light hydrocarbon geochemical characteristics and their application in Upper Paleozoic, Shenmu gas field, Ordos Basin

“…Some light hydrocarbons are related with formation temperature of sedimentary rocks during burial; therefore, heptane value ( H ) and isoheptane value ( I ) could be jointly used to estimate natural gas maturity (Shen et al., 2010; Thompson, 1983). Biodegraded gas has isoheptane value less than 0.8 and heptane value less than 16; low-mature gas has isoheptane value of 0.8–2.2 and heptane value of 16–22; mature gas has isoheptane value of 2.5–5 and heptane value of 22–30; high-mature gas has isoheptane value over 5 and heptane value over 30.…”

“…The maximum values occur in Well Shuang 8-12 with isoheptane value of 6.39 and heptane value of 17.68. These two values are closely related with source rock maturity; for the same maturity, oil-derived gas of sapropelic type would have higher heptane value than coal-derived gas of humic type (Shen et al., 2010). Due to the mixture of some oil-derived gas in Well Shuang 8-12, its heptane value and isoheptane value are abnormally high.…”

Radiogenesis of Low Maturity Natural Gas in the Turpan‐Hami Basin, NW China

“…maturity gas in this basin has considerable potential for exploration (Lu et al, 2009). The gas and source rock correlation shows that the natural gas has a very good correlation with the Jurassic source rocks, especially with the Middle and Lower Jurassic coal-bearing source rocks (Wang et al, 1998;Wang et al, 2008;Shen et al, 2010;Zhao, 2013). The Ro measurements of the Jurassic source rocks all over the Turpan-Hami Basin indicate that most of the source rocks in the Jurassic are immature (Cheng, 1994;Wang et al, 2008;Xu et al, 2008Xu et al, , 2009Lu et al, 2009;Zhao, 2013).…”