The Sedimentary and Foreground of Prospect for LeveeOverbank in Central Canyon, Qiongdongnan Basin

Key words: 
• leveeoverbank /
• ancient physiognomy /
• Qiongdongnan Basin /
• central canyon

Abstract: In our country as the lower frequency of land and shallow water exploration for oil and gas, deep water oil and gas exploration is playing more important role. Big reservoir body becomes the target of deepwater oil and gas exploration, because the deepwater oil and gas exploration has some characteristics, such as greater risks and higher investment. Central canyon, which comes from Yinggehai basin and pass through Qiongdongnan basin and enter into the xisha trough, lies in the deepwater area of Qiongdongnan basin and is mainly formed at 10.5 Ma, 5.5 Ma and 4.2 Ma. With an area of more than 50 000 km2, central canyon can be a target of deepwater oil and gas exploration.
In the central canyon, leveeoverbank sediments are abundant. Deepwater leveeoverbank has received considerable attention in the petroleum industry because of having good reservoirs. In order to conduct the prospect for central canyon, this article has analyzed the shape and control factors of leveeoverbank deposited in the central canyon by using 3D seismic profile and RMS attribute. After that, the sediment model is summed up and the foreground of prospect is analyzed. The result has shown below:
1. leveeoverbank sediments in the central canyon developed at least eight times, and have many micro facies such as crevasse splay, overflow splay and levee. In the cross seismic profiles, leveeoverbank sediments represent wedge shape with strong amplitude, intermediate frequency and midgood continuity, and combining with channel has shown "gullwing" shape. In the plane, the overall shape of leveeoverbank sediments is elongate and trends roughly parallel to the channel. Its area of single sand body could reach 17 km2.
2. In the central canyon, leveeoverbank sediments is mainly controlled by province and ancient physiognomy. The grain size whether sandrich or mudrich is mainly decided by province. The position is mainly decided by ancient physiognomy. The pond accommodate space is afforded for leveeoverbank to be deposited in the area where has fluctuation variation. On the opposite, in the incline area, there is no accommodation and leveeoverbank cannot deposit.
3. Leveeoverbank sediments which has many deposition time and large single sand body can be ideal stratigraphic traps and it could accumulate oil and gas if it cooperate with fault or "gas chimney". Leveeoverbank sediments have well foreground for prospect. 