EGU2020-12146
https://doi.org/10.5194/egusphere-egu2020-12146
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Different controlling factors of pore features between marine shale and transitional shale in the Upper Yangtze region, South China

Hongyang Jiang1,2, Zhenxue Jiang1,2, and Xin Li1,2
Hongyang Jiang et al.
  • 1State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
  • 2Unconventional Oil & Gas Research Institute, China University of Petroleum, Beijing, China

Compared with marine shale with plentiful research and successful exploration, fewer studies on transitional shale reservoirs limit further exploitation of shale gas. In this paper, comparative analysis, between Lower Silurian marine shale and Upper Permian transitional shale in the Upper Yangtze region, is carried out to analysis pore features of both shales and the main controlling factors, which can provide theoretical guidance for further exploration. A combination of methods is ultilized in terms of organic-chemistry geology measurement, X-ray diffraction (XRD), high-pressure mercury injection, gas adsorption, and focused ion beam milling and scanning electron microscopy (FIB-SEM). The results show that Lower Silurian marine shale and Upper Permian transitional shale have similar organic matter (OM) abundance (2.72% and 2.31%) and thermal degree (2.56wt%Ro and 2.68wt%Ro). However, the kerogen of Lower Silurian shale is type I derived from algae and plankton, while that of Upper Permian shale is mainly type III from higher plant debris. As for mineral composition, Siliceous minerals (> 43wt%) account for the majority in Lower Silurian shale, while clay (> 57wt%) is the main mineral in Upper Permian shale. Variations in material basis trigger to differences in pore characteristics between the two shales. Firstly, the pores in Lower Silurian shale are mostly hosted by OM with an average pore diameter of 7.94 nm, while Upper Permian shale mainly develops pores associated with clay minerals with an average pore diameter of 28.60nm. Moreover, Lower Silurian shale presented relatively higher pore properties than Upper Permian in both average pore volume (0.020ml/g and 0.015ml/g) and average pore surface area (7.99 m2/g and 1.2 m2/g). Various factors lead to the differences in pore types and pore properties between the two shales. For marine shale, OM with thermal convertibility tend to be mobilizable and porous. OM-hosted pores are the dominated type which is controlled by OM abandauce and thermal degree. However, in transitional shale, OM is featured by phase stability without porous feature. Pores associated with clay flakes are the main type which is controlled by the specifc material composition. Hence, the discrepancies of pore properties may be attributed to material diversities between marine shale and transitional shale.

How to cite: Jiang, H., Jiang, Z., and Li, X.: Different controlling factors of pore features between marine shale and transitional shale in the Upper Yangtze region, South China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12146, https://doi.org/10.5194/egusphere-egu2020-12146, 2020

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