GUO Zekun,born in 1997,is a master’s degree holder and engineer. He is mainly engaged in development geology research work. E-mail: gzkun-tlm@petrochina.com.cn.
Due to intense tectonic compression,the massive sandstone of the Bashijiqike Formation in the Cretaceous within the piedmont belt of the Kuqa Depression exhibit severe deformation,complex seismic imaging,and high ambiguity,resulting in limited methods and even fewer achievements in the detailed study of provenance transport pathway in the Keshen natural gas accumulation area. In response to this issue,a comprehensive study was conducted on the heavy mineral assemblages of over 400 sandstone samples from more than 40 wells in the Bashijiqike Formation of the Keshen area,as well as experimental analyses including sandstone clastic components and cathodoluminescence on over 600 samples from 26 wells. The results show that: (1)Zircon,tourmaline,garnet,and magnetite are consistently present as heavy minerals in the wells of this area. The presence and variations in the content of stable heavy minerals such as rutile,apatite,and titanite,along with unstable heavy minerals like epidote,chlorite,and mica,lead to differences in heavy mineral assemblages across well zones. Combined with the ZTR index,these variations can help determine the differences in sedimentary provenance pathways among the well zones. (2)The sedimentary source rocks of the thick sandstone mainly come from pre Carboniferous high-grade metamorphic rocks,low-grade metamorphic rocks,intermediate acidic igneous rocks,basic igneous rocks,and sedimentary rocks,which can be subdivided into nine heavy mineral combination zones from east to west. (3)Due to the control of the content of sandstone debris components by primitive sedimentation,the planar variation characteristics of the average content of potassium feldspar,plagioclase,and metamorphic rock debris in sandstone debris components indicate the existence of 5-7 source transport pathways. (4)Based on a comprehensive analysis of the characteristics of source pathways indicated by heavy mineral assemblages and sandstone debris components,it is believed that there were at least seven source transport pathways from east to west during the sedimentation period of the Bashijiqike Formation,among which Zone Ⅱ and Zone Ⅴ may have been channels with longer river extensions. The above understanding provides a basis for the analysis of large-scale sedimentary microfacies and favorable sand body distribution in the Keshen area,supporting the fine research and evaluation of gas reservoirs in this area.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |