Research paperStudy on the Cretaceous turbidite and reservoir features in the Qingshankou Formation in northern Songliao Basin, NE China

- We exhibit slope fan, channelized, laminated and sublacustrine fan in the Qingshankou Formation in northern Songliao Basin.
- By analyzing the 3-D seismic date, well data and core data, we depict the sedimentary process, features of the turbidites.
- Unconventional oil and gas reservoirs in laminated and sublacustrine fan brings new hope to the turbidite exploration.

Based on analysis of well and drilling data, cores, sediment grains and 3D seismic data, four types of turbidites-slope fan, channelized, laminated and sublacustrine fan turbidite-are identified in Members 1 and 2 of the Qingshankou Formation in northern Songliao Basin. The slope fan turbidite is located in Members 1 and 2 of the Qingshankou Formation. It is dominated by silt and fine sand and is distributed in an SN-trending ribbon zone along the slope break at delta front in the western part of the basin. The channelized turbidite is located at the bottom of Member 1 of the Qingshankou Formation. It is dominated by silt and fine sand and is distributed in an SN-trending strip-shaped zone along the Qijia-Gulong sag, with funnel-shaped sublacustrine fans at the end. The laminated turbidite body is located in Member 2 of the Qingshankou Formation. It is dominated by siltstone and argillaceous siltstone and is distributed continuously in a tongue-shaped zone along the northern delta front towards the lacustrine region, with belt-like distributaries at the central part and sublacustrine fans at the end. Low-permeability and low-yield lithologic reservoirs are formed near the delta front within the slope fan turbidite and channelized turbidite. There are “sweet spots” in local regions, where reservoir reform techniques are required to attain high industrial yields. Laminated turbidite and sublacustrine fans can form unconventional and continuous reservoirs that generally have no natural productivity; industrial production is impossible until horizontal drilling and multistage volume fracturing are employed. Therefore, the research results are important to the exploration of unconventional oil and gas reservoirs in northern Songliao Basin.