Sedimentary System of Denglouku Formation in Xujiaweizi Area, Songliao Basin

Abstract

Denglouku Formation in Xujiaweizi area is an important field needing urgent breakthroughs for deep gas exploration in northern Songliao Basin. In order to clarify the distribution characteristics of sedimentary facies of Denglouku Formation in Xujiaweizi area, the isochronal framework is established and the sedimentary facies is comprehensively analyzed, by core observation of sedimentary facies, sedimentary cycle analysis by logging data and comprehensive analysis of seismic attribute slices. The results show that: The Denglouku Formation in Xujiaweizi area mainly develops 6 sedimentary facies from bottom to top, the alluvial fan and fan delta, the lake and braided river delta, the river and lake pan-plane, 10 sedimentary subfacies and 20 sedimentary microfacies. Vertically, the development of sedimentary system in the first member of Denglouku Formation is limited, which controlled by unconformity. The sedimentary facies system of Denglouku Formation is alluvial fan-fan delta-lake sedimentary system in the first member, braided river delta-intermittent lake depositional system in the second-third member, and fluvial sedimentary system in the fourth member. The fan delta front glutenite, braided delta distributary channel coarse sandstone and braided channel thick sandstone provide favorable reservoir space for gas accumulation. Accurate identification of fine sedimentary facies of Denglouku Formation in Xujiaweizi area provides an important basis for further exploration and deployment, and has positive exploration significance.