The researchers studied the sedimentary layers in Xinzhuang Oilfield and found that they were formed by a fan-delta system. They identified different sub-facies within the fan-delta system, such as underwater channels and sandbars. By analyzing the distribution of these sedimentary layers, they were able to understand how they affect the physical and oil-bearing properties of the reservoir. This research provides a solid foundation for evaluating reservoirs and predicting where the best oil reservoirs might be located.