Spatial distribution patterns of single framework sand bodies of a shallow-water delta in the Cretaceous Quantou Formation of Xinmin Oilfield, Songliao Basin

Guided by the principles of high-resolution sequence stratigraphy and reservoir architecture, the spatial distribution pattern of single framework sand bodies of the 4th Member of the Cretaceous Quantou Formation(K₁q⁴) in the Min 36 block of Xinmin Oilfield of the Songliao Basin is studied. Some models have been established on the basis of depositional features acquired from cores, logging and production performance data. Shallow-water deltaic plain and front are well developed in the K₁ q⁴ of the study area and their framework sand bodies are mainly the deposits of distributary channels and subaqueous distributary channels respectively. Research results suggest that during the deposition of K₁q⁴, the lake level was rising. As the results, the shallow-water delta gradually retrograded toward the land. The A/S value is the main factor controlling the spatial distribution pattern of single sand bodies. When A/S value is far less than 1, there developed shallow water deltaic plain and the vertical stacking of single sand bodies are dominated by lateral and vertical tangency, and in view of plane distribution, sandbodies are contiguous. Individual sand bodies may reach 396 to 463 meters in length and 5.2 to 5.8 meters in width on average. However, when A/S value is less than or equal to 1, the vertical stacking patterns of single sand bodies are dominated by lateral and vertical superposition. In a plane view, sandbodies are distributed in a reticular pattern. Single sand bodies are 308 to 412 meters long and 4.2 to 5.2 meters wide on average. When A/S value is far more than 1, the sand bodies are dominated by a vertical stacking pattern by separated sandbodies, in the plane view, sandbodies are distributed in a dendritic pattern consisting of sand bodies 165 to 325 meters long and 2.4 to 4.0 meters wide on average.