The researchers studied the sedimentary facies in the Wenchang formation of Huizhou sag in the South China Sea. They used 3D seismic data to identify different types of seismic facies, such as wedge-shaped and lens facies. By analyzing these seismic facies, they were able to infer the sedimentary facies present, including braided river delta and fan delta facies. The braided river delta was found to be the most important sedimentary facies in the area.