Lacustrine turbidite channels and fans in the Mesozoic Songliao Basin, China

摘要

The Songliao Basin is a large Mesozoic nonmarine petroliferous basin in northeastern China. Based on an analysis of high-resolution three-dimensional seismic data, a large-scale lacustrine turbidite channel and fan system is identified within the lacustrine mudstone of the Nenjiang Formation in the central depression. The system was fed by a delta complex and extends to the south along the Daqing anticline. This system is composed of three trunk channels and four tributary channels, with a maximum length of about 71 km. Changes in channel patterns, specifically bifurcations and terminations into fans, are associated with gradient changes along the palaeoslope, which vary from 0.13 to 0.02 degrees. Interpretation of geophysical well logs and core indicate that channel sand bodies are oil charged. The widest channel sandstone body is about 600 m with an average around 300 m, and the maximum thickness of sandstone is more than 6 m with an average of about 3 m. The sandstone bodies of the turbidite system, which are encased within organic-rich source rocks, provide a new target for hydrocarbon exploration and development.