The Development Regulanities And Reservoiring Conditions Analysis Of Reefs And Banks In Deepwater Area Of Northern South China Sea

The deepwater area of northern south China sea Pearl River Mouth Basin and Qiongdongnan Basin has a very large oil and gas exploration prospect.Reefs and Banks oil and gas reservoirs is the important exploration targets in the deepwater area of northern south China sea, at present, the deepwater area of Pearl River Mouth Basin and Qiongdongnan Basin has low degree of exploration and research. According to the widespread moundy reflectors in the seismic data, it is known that Pearl River Mouth Basin and Qiongdongnan Basin have reefs develop in Miocene, but large biohermal reservoirs has not yet found in the deepwater area. Therefore, the study of development regularities and the explain of biohermal reservoirs of Reefs and Banks of deepwater area of Pearl River Mouth Basin and Qiongdongnan Basin causes significant exploration value.Based on the existing data of deepwater area of Pearl River Mouth Basin and Qiongdongnan Basin and by analyzing the palaeostructure, paleogeographic background and in combination with drilling sedimentary facies and 2 d and 3 d seismic data comprehensive research, then geological interpretation and analysis of the forming reason and background for the extensive development of hummocky reflector, then the analysis of hydrocarbon accumulation conditions and gas detection for the reef type of moundy reflectors.Two marginal sea tectonic cycle in south China sea determines the different types of basins formation, basins ancient topography and geomorphology, coastline and ancient sedimentary system, and then control the development of ages of reefs, the distribution regularity of reefs and the type of reefs in different basin.During late Oligocene, the deepwater area of Pearl River Mouth Basin and Qiongdongnan Basin mainly deposited by the littoral and shallow sea deposit, northern of Pearl River Mouth Basin has large delta sedimentary, the South uplift of Qiongdongnan basin and Shenhu uplift were denudation area. Into the Miocene, with the rising of sea levels, Liwan sag of Pearl River Mouth Basin and The central depression belt of Qiongdongnan Basin deposited bathyal deposit, northern area deposited delta deposit, carbonate platform and reefs grow at Southern uplift area.Moundy reflectors in the doopwater area of Pearl River Mouth Basin and Qiongdongnan Basin are mainly have the following four types:reefs, contourite hills, volcanic moundy and turbidite fan. Among them reefs mainly grow in the South uplift of Pearl River Mouth Basin and Qiongdongnan Basin, in the edge of South uplift and in the shallow water platform of South uplift.Through the analysis of ancient geography, structures and seismic attribute of the northern south China sea, the distribution of carbonate platform and reefs are clear. Different size scale of 5 carbonate platforms and 4 reefs in the South uplift of Pearl River Mouth Basin and Qiongdongnan Basin has been identified. The hydrocarbon source rocks, storage and transportation conditions of the carbonate platforms in Pearl River Mouth Basin and Qiongdongnan Basin and hydrocarbon detection of the reefs are analyzed, the results shows that the carbonate rocks in the south uplift of Pearl River Mouth Basin and Qiongdongnan Basin have accumulation conditions and part of the reefs display gas.