Seismic Prediction of Ultra Deep Lithologic Oil Reservoirs in Permian of Fukang Sag, the Junggar Basin and Its Exploration Significance

The Permian Lucaogou Formation and the Upper Urhe Formation in the Fukang Sag of the the Junggar Basin have always been considered to be dominated by shallow water sedimentary systems such as shore shallow lake/delta. Tectonically, due to the narrow slope area, lithologic exploration has not made progress directly from the high part into the trough area. With the exploration breakthrough of A1 well, it has been revealed for the first time that multiple large deep-water lake bottom fans have developed in the slope area and trough area of Lucaogou Formation in Fukang Depression, and a large-scale lithological trap group has developed in the Upper Urhe Formation. Through paleogeomorphological characterization and seismic reservoir prediction research, the Lucaogou Formation and upper Urhe Formation exhibit characteristics of multiple depressions and subsidence centers. The lake floor fan is influenced by both external sources (Kelameili Mountain) and internal sources (Xiquan Nose Uplift), and the dominant sand bodies developed under the control of slope break zones form a large-scale lithological trap group. Taking into account the influence of the development layer, provenance, and later uplift and erosion of the lake floor fan, we have broken through the previous exploration ideas of high parts and slope areas in the Fukang Depression. The deep and ultra deep layers below 7000 m in the trough area still have the conditions for the development of large-scale lithological reservoirs. The gravity flow exploration of the Lucaogou Formation should focus on the low-level water inflow system tract. The Upper Urhe Formation develops a low-level delta front lake floor fan scale sand body lithological trap group under the control of the slope break zone. The lacustrine mudstone serves as the cap layer, and the reservoir cap combination is good, which has important exploration significance.