Sublacustrine fan is one of the important origin types since glu-tenites are developed widely in the steep slope and subsag zones of Chezhen Sag. Deposition of the sublacustrine fan corresponds to low stand system tract (LST)or early transgressive system tract (TST) , which was controlled by tectonic activity, attitude and secondary faults of border fracture at the edge of the basin. Single deposition of the sublacustrine fan is positive cycle with upward- fining grain size. There are matrix- supported conglomerate rocks and massive conglomerate - sandstones with an origin of deepwater gravity flow in its bottom, and massive conglomerate -sandstones and deformed bedding medium-( or fine-) sandstones with better grading, positive skewness, two - segment style of grain probability curve and an origin of tractive current. As a whole, the glutenites of the sublacustrine fan in this area is characterized by deep buried depth, coarse grain and poor grading, and belongs to super low - porosity and super low - permeability reservoirs with two-porous media of pore and micro- fractures. The secondary pore formed by organic acid chemical erosion is the main type of storage place. Surpressure has vital function for reforming reservoir quality in this area.
Petroleum Geology and Recovery Efficiency
sublacustrine fan,glutenite,faulted lake basin,surpressure, Chezhen Sag