Paleo-geomorphologic controls on the formation and distribution of high-quality reservoirs during lake transgression: An example of the Qingshuihe Formation in Gaoquan Structural Zone of Sikeshu Sag, Junggar Basin

Key words: 
• Gaoquan Structural Zone /
• Qingshuihe Formation /
• paleo-geomorphology /
• slope break /
• fan delta

Abstract: Paleo-geomorphology has a strong control on the sedimentary system and reservoir distribution. This paper analyzes the single-well facies in Gaoquan Structural Zone of Sikeshu Sag, identifies the characteristics of the sedimentary and reservoirs of the Qingshuihe Formation, and then combines with the paleo-geomorphology of the pre-Qingshuihe Formation in Gaoquan Structural Zone, establishes model of the sedimentary evolution under the control of paleo-geomorphology, and clarifies the influence of micro-geomorphology on the distribution of high-quality reservoirs. The study shows that three slope breaks are developed in the Gaoquan Structural zone of Sikeshu Sag, with a near-northwestern-south-eastern trend. Each slope-folding zone can be divided into two types of paleo-geomorphology units, namely, grooves and platforms. Three phases of regressive fan deltas were formed on the three slope breaks during the lake transgression, and each phase of fan deltas can form 9-15m thick conglomerate reservoirs. On each slope breaks, the groove and platform control the mud content of the conglomerate reservoirs, and the brown conglomerate with high mud content is easily developed in the groove area, while the gray or gray-green conglomerate with low mud content is easily developed in the platform area. The conglomerate with low mud content is ready to form high-quality reservoir in the platform area.