Significance of the secondary pores in perthite for oil storage and flow in tight sandstone reservoir

• Published in: Marine and petroleum geology Vol. 110; pp. 178 - 188
• Main Authors: Du, Shuheng, Zhao, Yapu, Jin, Jun, Kou, Gen, Shi, Yongmin, Huang, Xianfu
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2019
• Subjects: K-feldspar; Na-feldspar; Perthite; Tight sandstone; Unconventional oil reservoir; Tight sandstone; Unconventional oil reservoir; K-feldspar; Perthite; Na-feldspar
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/j.marpetgeo.2019.07.006

Perthite is a special type of skeleton mineral in tight oil sandstone which cannot be ignored. However, few attention was paid to the secondary pores in perthite and their contributions in tight oil reservoir. This study reveals the perthite's significance in unconventional oil flow characterizes comprehensively and quantitativel by combining the Field Emission Scanning Electron Microscope (FE-SEM) with high resolution, Energy Dispersive Spectrometer (EDS) analysis, high precision image processing, comprehensive parameters construction and calculation. Typical perthite samples of Chang 7 tight oil reservoir of Ordos basin were selected for this study. Our results demonstrate that the growth of K-feldspar and Na-feldspar in perthite is complementary. The mixing process of the two types of stripes promotes each other rather than inhibiting each other. As to the development of secondary pores of perthite, there are clear differences in the area and number of pores, medium differences in the porosity, radius and perimeter, and small differences in other parameters. The more regular and uniform growth of Na-feldspar, the more likely the perthite is to form regular and normalized secondary pore. At least 56.7% of the secondary pore of perthite contributes to oil flow in the process of oil migration or development, and its scientific significance cannot be ignored. The conclusion could provide the geological basis for the effective development of the unconventional hydrocarbon reservoirs. •The more regular and uniform growth of Na-feldspar, the more likely the perthite is to form regular and normalized secondary pore.•At least 56.7% of the secondary pore of perthite contributes to the oil and gas flow in the process of oil and gas migration or development.