Reservoir characteristics, formation mechanism and exploration direction of deep buried tight conglomerate of Permian Upper Urho Formation of Fukang Sag, Junggar Basin

Key words: 
• Tight conglomerate reservoir /
• Deep buried reserovir /
• Formation mechanism /
• Fukang Sag /
• Upper Urho Formation /
• Junggar Basin

Abstract: The Permian Upper Urho Formation in the eastern slope area of Fukang Sag is an important oil and gas exploration formation in the Junggar Basin. However, the deep conglomerate reservoir is tight, and the unclear reservoir characteristics and genesis restrict the process of oil and gas exploration and development. Through core observation, casting thin section, physical property analysis, scanning electron microscope, high-pressure mercury injection curve and other data, the petrology characteristics, physical property characteristics, pore characteristics and reservoir genetic mechanism of the tight conglomerate reservoir of the Upper Urho Formation in the slope area of Fukang Sag were studied. The results indicate that: ① the reservoir is an ultra-low porosity and ultra-low permeability lithic sandstone reservoir; ② The pore types are mainly micropores and fractures, and the pore structure is mainly small pores and micro throats, with poor connectivity; ③ Sedimentary microfacies are the basis for the differential development of reservoir physical properties. Conglomerates deposited in clastic flow channels, and fine sandstones deposited in far sand bars have high shale content and poor physical properties, while underwater distributary channels have relatively good physical properties of conglomeratic sandstones; Diagenetic compaction and clay illitization are the main factors causing the tightness and low permeability of the reservoir; Fractures and high pressure are the main reasons for higher initial oil and gas production; ④ The conglomeratic sandstone in the underwater distributary channel at the top of P3w1 and bottom of P3w2 is an important layer for stable oil production, and the Fubei area, far from the influence of provenance of the Xiquan uplift, is a favorable area for further oil and gas exploration.