Abstract:

The Upper Triassic Yanchang Formation sandstone characterized by low permeability is the main reservoir in the Qingcheng—Heshui area of Ordos Basin, within which the tectonic fractures serve as important seepage pathways. On the basis of rock mechanics parameters testing, considering the influence of sandstone distribution, the paleostress field in the main fracture forming period was simulated, and the tectonic fractures were predicted with the constraints of cores using 3D Finite Element Method (FEM). The results show that the Yanshanian tectonic fracture density is high in Well Zhuang 72, Well Zhuang 47, Well Ning 88 and Well Zheng 20 areas, with the density up to 0.10 m-1, while the Himalayan tectonic fracture density is high in Well Zhuang 156, Well Ning 45 and Well Zheng 20 areas. Comparing to the Himalayan tectonic period, the Yanshanian tectonic fracture density as a whole is higher. The study results can provide us basic geological data for building conceptual fracture distribution and fracture porosity calculation model, and are able to support the reservoir prospecting and exploitation as well in the QingchengHeshui area.

Key words:  tectonic fractures, Chang 63 reservoir, QingchengHeshui area, Yanchang Formation, Ordos Basin