The researchers studied the distribution of hydrocarbon source rocks in Heshan Sag, a deep-water area in the South China Sea. They used methods like studying rock layers and seismic patterns to predict where the rocks are. They found that the rocks in Heshan Sag have good potential for holding oil and gas, similar to rocks in another nearby area. This suggests that Heshan Sag could be a good place to look for oil and gas in the future.