Differences of polygonal faults related to upper Miocene channels:a case study from the Beijiao sag of Qiongdongnan basin,South China Sea  

作　　者：Yufeng LI Renhai PU Xueqin ZHAO Gongcheng ZHANG Xiaowei FAN Jingjing BAO Jiong WANG 

机构地区：[1]School of Environment and Resource,Southwest University of Science and Technology,Mianyang 621010,China [2]State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,China [3]Key Laboratory of Marine Mineral Resources,Ministry of Natural Resources,Guangzhou 510075,China [4]CNOOC Research Institute,Beijing 100028,China [5]Research Institute of Yangchang Petroleum(Group)Co.Ltd.,Xi’an 710075,China [6]Laboratory of Ocean and Coast Geology,Third Institute of Oceanography,Ministry of Natural Resources,Xiamen 361005,China [7]Central Sichuan Oil-Gas District,Petro-China Southwest Oil and Gas Field Company,Suining 629000,China

出　　处：《Journal of Oceanology and Limnology》2023年第1期84-99,共16页海洋湖沼学报（英文）

基　　金：Supported by the Key Laboratory of Marine Mineral Resources;Ministry of Land and Resources of China(No.KLMMR-2018-B-07);the National Basic Research Program of China(No.2011ZX05025-006-02);the National Natural Science Foundation of China(No.41672206)。

摘　　要：Deep-water coarse-grained channels are embedded within a polygonal fault tier,and the polygonal faults(PFs)present non-polygonal geometries rather than classic polygonal geometry in plan view.However,PFs present differences when they encounter deep-water(coarse-grained vs.fine-grained)channels with different lithology,which has not been further studied to date.Three-dimensional(3D)seismic data and a drilling well from Beijiao sag of Qiongdongnanbasin,South China Sea were utilized to document the plan view and cross-sectional properties of the PFs and their differences and genetic mechanism were investigated.Results show that,first,PFs can be divided morphologically into channel-segmenting PFs and channel-bounding PFs in plan view.The former virtually cuts or segments the axes of channels in highand low-amplitudes,and the latter nearly parallels the boundaries of the channels.Both are approximately perpendicular to each other.Secondly,channel-bounding PFs that related to low-amplitude channels are much longer than those of high-amplitude ones;channel-segmenting PFs related to low-amplitude channels are slightly longer than the counterparts related to high-amplitude channels.Lastly,the magnitudes(e.g.,heights)of the PFs are proportional to the scales(e.g.,widths and heights)of low-amplitude channels,whereas the magnitudes of the PFs are inversely proportional to the scales of high amplitude channels.Coarse-grained(high amplitude)channels act as a mechanical barrier to the propagation of PFs,whereas fine-grained(low-amplitude)channels are beneficial to the propagation and nucleation of PFs.Additionally,the genetic mechanism of PFs is discussed and reckoned as combined geneses of gravitational spreading and overpressure hydrofracture.The differences of the PFs can be used to reasonably differentiate coarse-grained channels from fine-grained channels.This study provides new insights into understanding the different geometries of the PFs related to coarse-grained and fine-grained channels and their genetic mechanism.

关 键 词：polygonal faults coarse-grained channels fine-grained channels gravitational spreading overpressure hydrofracture 

分 类 号：P744[天文地球—海洋科学]