4th International Conference of Palaeogeography

293 / 2019-08-27 18:35:28

MIOCENE GRAVITY FLOW CHANNEL TYPES AND SEDIMENTARY CHARACTERISTICS IN THE EASTERN YINGGEHAI BASIN

gravity flow channel,axial channel,downstream channel,sedimentation and filling,Oil and gas exploration

The eastern part of Yinggehai Basin develops different types of shallow marine gravity flow channels during Miocene, and different types of gravity flow channels have different sedimentary characteristics and architecture in their sandstone reservoirs. Thus, it is of great oil-gas significance for us to study the filling characteristics of different gravity flow channels types. Based on the 3D seismic, drilling and core sample testing data, the gravity flow channels are identified by the 3D closed interpretation of well-seismic calibration.
According to the relationship between channel and dip direction, the gravity flow channels in this area are divided into downstream channels and axial channels. Among them, the scale (width and depth) and the sinuosity of the downstream channels gradually increase toward the basin, and their distal ends are straighter than the proximal ends, while the axial channels, overall, are characterized by small sinuosity and straight shapes, with the channels length varies greatly, from a minimum of only about 20km to a maximum of 190km. In addition to morphological characteristics, there are also some differences in the formation processes and main controlling factors between the two types of gravity flow channels. The downstream channels develop in the low-lying and source-concentration areas under the background of sea level decline, while the formation of axial channels are mainly controlled by the strike-slip-extension faults under the global sea level decline background.
Based on the comprehensive analysis of well-seismic data, according to the sedimentary processes, three sedimentary units of gravity flow channels, namely sandy debris flow massive sandstone, turbidity currents interbedded sandstone and thin layer muddy sandstone are identified, and the depositional characteristics of different sedimentary units vary a lot. Among them, the sandy debris flow massive sandstone mainly develops a massive sandstone facies with floating mud clasts or muddy tearing clasts, with a high box shape in the GR curve and a low RMS amplitude in the seismic reflection respectively. The turbidity currents interbedded sandstone mainly exhibits an incomplete Bouma sequence in the core and a worm-like reflection structure with low or high RMS amplitude on the seismic profile respectively. Thin layer muddy sandstone represents a weak reflection amplitude on the seismic profile and a low-amplitude serrated shape in the GR curve. Through the depositional filling characteristics of gravity flow channels, it is considered that the large scale sandy debris flows massive sandstone filling in the gravity flow channels of this area have great oil-gas exploration potential due to their favorable sediment thickness and reservoir quality.