Logging identification of Ordovician karst cave filling in the Tahe Oil Field

The SINOPEC Northwest Company has deployed over 1300 wells in the Ordovician in the Tahe Oilfield, among which about 1/3 of the wells turned out empty or leaking. Many wells drilled to karst caves. The caves were partially filled, and the filling materials had various physical properties. The accurate identification of the nature of cave fillings can help the deployment of completion program and select completion interval. We used core data to calibrate conventional logging, summarized the logging responses of different fillings, and identified fillings on seismic maps. The fillings of ancient underground rivers in blocks 6, 10, 12 in the Tahe Oil Field were studied.