Diagenesis and Diagenetic Evolution of Deltaic and Neritic Gas-Bearing Sandstones in the Lower Mingyuefeng Formation of Paleogene, Lishui Sag, East China Sea Shelf Basin: Implications for Depositional Environments and Sequence Stratigraphy Controls  

作　　者：XU Fa ZHANG Penghui ZHANG Jinliang LIU Jinshui HOU Guowei ZHANG Ming LI Jingzhe LIU Shasha GUO Jiaqi MENG Ningning 

机构地区：[1]Shanghai Branch of CNOOC Ltd. [2]Qingdao Institute of Marine Geology [3]College of Resources Science & Technology, Beijing Normal University [4]College of Marine Geosciences, Ocean University of China

出　　处：《Acta Geologica Sinica(English Edition)》2015年第5期1625-1635,共11页地质学报（英文版）

基　　金：Financial support was provided by the National Science and Technology Major Project of China (No.2011ZX05023-002-003)

摘　　要：Gas-bearing deposits in the Lower Mingyuefeng Formation of Paleogene, Lishui Sag, East China Sea Shelf Basin consist of shoreface sandstones of the highstand systems tract（HST） and transgressive systems tract（TST）, and deltaic sandstones of the lowstand systems tract（LST） and falling stage systems tract（FSST）.Detailed petrographic observations suggest that the diagenetic features and related evolution of these deposits cannot be simply characterized and demonstrated in the depth domain.However, the occurrence of diagenetic minerals systematically depends on the studied interval within the HST, TST, LST, and FSST; therefore, diagenesis in this region can be better constrained when studied in the context of the depositional environments and sequence stratigraphic framework.The eogenetic processes in such settings include：（1） microcrystalline siderite precipitated as concretions in almost all environments and systems tracts, which inhibited further mechanical compaction;（2） grain dissolution and kaolinitization occurred in shoreface HST sandstones and deltaic LST and FSST sandstones;（3） glaucony was locally observed, which did not clearly reflect the controls of facies or sequence stratigraphy; and（4） cementation by pyrite aggregates occurred in the shoreface HST sandstones and deltaic LST sandstones.The mesogenetic diagenesis includes：（1） partial conversion of kaolinite into dickite in deltaic LST sandstones, and minor chlorite cementation in deltaic FSST sandstones;（2） transformation of kaolinite into illite and quartz cementation in deltaic LST and FSST sandstones;（3） frequent precipitation of ankerite and ferroan calcite in shoreface TST sandstones and early HST sandstones, forming baffles and barriers for fluid flow, with common calcite in shoreface HST sandstones as a late diagenetic cement; and（4） formation of dawsonite in the deltaic LST and FSST sandstones, which is interpreted to be a product of the invasion of a CO2-rich fluid, and acts as a good indicatGas-bearing deposits in the Lower Mingyuefeng Formation of Paleogene, Lishui Sag, East China Sea Shelf Basin consist of shoreface sandstones of the highstand systems tract（HST） and transgressive systems tract（TST）, and deltaic sandstones of the lowstand systems tract（LST） and falling stage systems tract（FSST）.Detailed petrographic observations suggest that the diagenetic features and related evolution of these deposits cannot be simply characterized and demonstrated in the depth domain.However, the occurrence of diagenetic minerals systematically depends on the studied interval within the HST, TST, LST, and FSST; therefore, diagenesis in this region can be better constrained when studied in the context of the depositional environments and sequence stratigraphic framework.The eogenetic processes in such settings include：（1） microcrystalline siderite precipitated as concretions in almost all environments and systems tracts, which inhibited further mechanical compaction;（2） grain dissolution and kaolinitization occurred in shoreface HST sandstones and deltaic LST and FSST sandstones;（3） glaucony was locally observed, which did not clearly reflect the controls of facies or sequence stratigraphy; and（4） cementation by pyrite aggregates occurred in the shoreface HST sandstones and deltaic LST sandstones.The mesogenetic diagenesis includes：（1） partial conversion of kaolinite into dickite in deltaic LST sandstones, and minor chlorite cementation in deltaic FSST sandstones;（2） transformation of kaolinite into illite and quartz cementation in deltaic LST and FSST sandstones;（3） frequent precipitation of ankerite and ferroan calcite in shoreface TST sandstones and early HST sandstones, forming baffles and barriers for fluid flow, with common calcite in shoreface HST sandstones as a late diagenetic cement; and（4） formation of dawsonite in the deltaic LST and FSST sandstones, which is interpreted to be a product of the invasion of a CO2-rich fluid, and acts as a good indicat

关 键 词：diagenetic alteration depositional environment sequence stratigraphy reservoir quality PALEOGENE East China Sea Shelf Basin 

分 类 号：P618.13[天文地球—矿床学] P736[天文地球—地质学]