Genetic types and origins of natural gases from eastern Fukang Sub-depression of the Junggar Basin, NW China: Implication for low-mature coal-derived gases

Mineralogical characteristics and sources of alkali metals in the No. 6 coal seam from the Fukang mining area of the Zhunnan coalfield, Xinjiang province, Northwest China

“…As mentioned before, the Fukang coal field is rich in coalbed methane, which formed from the coalification process. Meanwhile, geological data show that quartz albitophyre intrusive bodies, which have been formed in the Carboniferous period (Cao et al., 2017; Gong et al., 2017), located in the Tianshan piedmont, are distributed in the south and southeast of the coal field. Moreover, albite has been found in the No.…”

“…The annual average precipitation and evaporation values are 251.59 mm and 1543.81 mm, respectively (Gong et al., 2015). For the area of low precipitation and comparatively high evaporation capacity, annually, the topsoil layers have undergone salinization, and many saltwater lakes are distributed in Xinjiang province (Gong et al., 2017; Xu et al., 2007). In the Fukang area, the main chemical type of phreatic water is SO 4 ·HCO 3 –Na·Ca (Li, 2014).…”

“…(2015) on Na contents in the open-pit mine of the Zhundong coal mine, the Na contents in the coal seam near the bottom of the Xiaohuangshan coal mine were relatively high. The underlying Mesozoic formation water is dominated by SO 4 ·HCO 3 –Na with ultrahigh or normal pressures in the Fukang area (Gong, 2017; Li et al., 2013; Wen et al., 2012). In addition, the Na 2 SO 4 -type Mesozoic formation water, with ultrahigh, pressure is often associated with the generation of hydrocarbons via the hydrocarbon resource rock in the coal systems (Voast and Montana, 2003).…”

“…6 coal seam (vitrinite reflectance of 0.55), is poor and the dominant pore types are micropore (Li et al., 2017; Wang et al., 2018b). Therefore, the Na 2 SO 4 and NaHCO 3 type waters in the underlying strata with ultrahigh or normal pressures have a relatively low flow rate and are rather stagnant (Gong et al., 2017; Li et al., 2013). The Na + is enriched in those pores and fractures, indicating a higher Na content near the bottom of coal seam in comparison to the middle of the coal seam.…”

The characteristics and genetic mechanisms of the Upper Permian Shangwuerhe clastic reservoir in the eastern Junggar Basin, Northwest China

“…However, as the largest proliferous depression in the Junggar Basin, the hydrocarbon exploration in the Fukang Sag has not yielded any significant discoveries. This may be because previous hydrocarbon exploration in the area centered on the bulge around the perimeter of the sag (Zhang, 2011;Wang et al, 2013;Sun et al, 2016;Gong et al, 2017Gong et al, , 2019Hu et al, 2020;Wu et al, 2020). The important discovery of "near-source exploration" in the proliferous Mahu and Shawan sags demands that exploration targets change from uplift to depression areas in the Fukang Sag.…”