Recovery of the Erosion Thickness and Characterization of the Paleogeomorphology in the Southern Lishui Sag, East China Sea Shelf Basin  

作　　者：LI Na ZHANG Jinliang SHEN Wenlong LIU Yang LIU Huaishan WANG Jinkai XIE Jun 

机构地区：[1]Faculty of Geographical Science,Beijing Normal University,Beijing 100875,China [2]CNOOC China Ltd.,Shanghai 200335,China [3]School of Earth Sciences,China University of Geosciences,Wuhan 430074,China [4]College of Marine Geosciences,Ocean University of China,Qingdao 266100,China [5]College of Geological Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China

出　　处：《Journal of Ocean University of China》2020年第2期320-330,共11页中国海洋大学学报（英文版）

基　　金：supported by the National Science and Technology Major Projects(No.2016ZX05027-001-006)

摘　　要：The restoration of the denudation thickness is the basis for quantitatively analyzing the basin burial history,thermal evolution history and hydrocarbon accumulation conditions.The well data is not sufficient to do this in the southern Lishui Sag with only 5 wells,so the new,high-quality three-dimensional(3D)seismic data is essential.The methods employed to determine the eroded thicknesses of key unconformities in the study area are the mudstone acoustic time difference(AC)method,vitrinite reflectance(Ro%)method and stratigraphic trend comparison method.On the basis of the structural evolution,the restoration of the paleogeomorphology is carried out.The results show that the Wenzhou formation(E2 w)in the entire study area has been all denuded.The denudation thickness is in the range of 0–550 m,and decreases gradually from west,thicker than 200 m,to east.The erosion of the upper Lingfeng formation(E1l)are mainly occurred in the N-P-1 structural trap(N-P-1),the N-P-2 structural trap(N-P-2)and the N-P-3 structural trap(N-P-3).Among them,the eroded area in N-P-1(near well S-1)and N-P-2 is 200–230 km^2,and the denudation thickness is 0–600 m,which increases from south to north,even up to 200–400 m in the region around well S-1.In N-P-3,the extent of denudation is 30–50 km^2,and the denudation thickness is 0–400 m.In the early stage of the upper E1 l,one north-south strike slip fault began to develop in the southern study area.Affected by this fault,the southern Lingfeng bulge was offset,forming a gorge,and the eastern and western sides of the concave belt connected to each other.On the basis of the paleo-geomorphological characteristics,it is shown that the sedimentary center of the west subsag began to migrate to the south.The restoration of the denudation thickness is the basis for quantitatively analyzing the basin burial history, thermal evolution history and hydrocarbon accumulation conditions. The well data is not sufficient to do this in the southern Lishui Sag with only 5 wells, so the new, high-quality three-dimensional(3 D) seismic data is essential. The methods employed to determine the eroded thicknesses of key unconformities in the study area are the mudstone acoustic time difference(AC) method, vitrinite reflectance(Ro%) method and stratigraphic trend comparison method. On the basis of the structural evolution, the restoration of the paleogeomorphology is carried out. The results show that the Wenzhou formation(E2 w) in the entire study area has been all denuded. The denudation thickness is in the range of 0 – 550 m, and decreases gradually from west, thicker than 200 m, to east. The erosion of the upper Lingfeng formation(E1 l) are mainly occurred in the N-P-1 structural trap(N-P-1), the N-P-2 structural trap(N-P-2) and the N-P-3 structural trap(N-P-3). Among them, the eroded area in N-P-1(near well S-1) and N-P-2 is 200 – 230 km2, and the denudation thickness is 0 – 600 m, which increases from south to north, even up to 200 – 400 m in the region around well S-1. In N-P-3, the extent of denudation is 30 – 50 km2, and the denudation thickness is 0 – 400 m. In the early stage of the upper E1 l, one north-south strike slip fault began to develop in the southern study area. Affected by this fault, the southern Lingfeng bulge was offset, forming a gorge, and the eastern and western sides of the concave belt connected to each other. On the basis of the paleo-geomorphological characteristics, it is shown that the sedimentary center of the west subsag began to migrate to the south.

关 键 词：Oil and gas denudation thickness paleogeomorphology stratigraphic trend Lishui Sag 

分 类 号：P618.13[天文地球—矿床学]