Identification and analysis of ancient river near the Ordovician carbonate buried hill in Tarim Basin

Two sorts of ancient water patterns that surface water pattern and underground water pattern exist and develop near the Ordovician carbonate buried hill in Tarim Basin. Frequency mixing technique can effectively improve the resolution effect of the frequency division result attribute of single frequency, which is more effective in detailed identifying the surface and underground river. Both surface river pattern and underground river pattern can form effective karst space, which provides important proof for revealing the development law of the Ordovician ancient karst in Tarim Basin. Underground river pattern controls the distribution of large karst cavity, and poses significant impact on the formation of top large collapse fractures due to cavity collapse in later stage; surface river pattern has mainly invasion effect at the buried hill high parts and lateral and vertical corrosion at low parts, however, deep corrosion can be formed on both sides and riverbed. During the process of diagenesis, fractures are formed due to later filling and overburden differential compaction. The study on ancient river pattern poses significance for revealing karst distribution law, deepening non-tectonic fracture study and expanding exploration of fractured reservoirs.