Machine Learning Based Model for Predicting the Distribution of Terrestrial Organic Matter in Marine-terrestrial Transitional Environmen—From Sedimentary Simulation Experiments to Geological Applications

Key words: 
• Marine-terrestrial transitional environment /
• Terrestrial organic matter /
• Machine learing /
• Sedimentary simulation /
• Prediction model

Abstract: Marine-terrestrial transitional source rocks are the main source rocks in several offshore basins in China, and their differential distribution characteristics restrict the prediction accuracy of source rocks and the effectiveness of oil and gas exploration. And the transport and sedimentation process of terrestrial organic matter determines the quality and distribution of source rock in marine-terrestrial transitional environment. Using a combination of flume sedimentary simulation and 3D laser scanning technology, the dynamic recording and quantitative characterization of the transport process of terrestrial dispersed organic matter under different water salinity conditions are carried out from the perspective of forward modeling. Machine learning algorithms are used to establish a TOC prediction model. The results show that terrestrial organic matter in the marine-terrestrial transitional environment is mainly enriched in the delta front and prodelta. As the transportation distance increases, the abundance of terrestrial organic matter shows a trend of first increasing and then decreasing. Under the influence of salt flocculation, the transportation distance of terrestrial organic matter in saltwater environment is closer to the source area, and the sediment thickness is larger. A TOC prediction model was established under experimental conditions based on three deep learning algorithms, and ultimately selects the prediction model based on random forest algorithm with outlier removal and experience based sedimentary facies assignment as input features as the optimal model. The TOC prediction model under experimental conditions is combined with geological conditions to complete the TOC prediction of source rocks in the Yacheng Formation of the Yanan depression. The results show that the transportation distance of terrestrial organic matter in the Yanan Depression can reach 50 km, and the highest degree of organic matter enrichment occurs at a distance of about 31 km from the source area.