Paleogeomorphic Influence on Facies Characteristics and Reservoir Prediction in Lacustrine Basin—By Taking Cretaceous Reservoirs in the Western Slope of SL Basin, China as an Example

The West Slope of SL Basin, China, mainly targets on lithologic reservoirs for oil and gas. The paleogeomorphology and provenance direction analysis has great significance for predicting the type and distribution of sand body. According to the analysis of well logging, core and seismic data, braided delta and gravity sediment mainly develop in the study area. A backs tripping method is used to reconstruct the topography of Qingshankou to Yaojia Formation, Cretaceous. The West Slope is mainly controlled by two slope belts in Qingshankou Formation, with the width of upper slope 12 - 18 km and the gradient 0.7 - 0.8 degrees, the width of lower slope 13 - 15 km and the gradient 1.0 degrees. The West Slope is controlled by a single slope belt in Yaojia Formation, with the lower slope width of 13 - 16 km and the gradient 0.4 degrees. The relationship between the slope belt, provenance direction and sand body distribution is analyzed, and result shows that the combination of upper and lower slope controls the distribution of reservoir types, and the provenance supply rate controls the scale of sand body. The gravity flow develops when the provenance direction is parallel to slope direction, and the slope becomes transporting channel in vertical to provenance direction. The paleogeomorphology, lake level and provenance direction are the main control factors of sand body in West Slope.