Division and Characteristics of Shale Parasequences in the Upper Fourth Member of the Shahejie Formation, Dongying Depression, Bohai Bay Basin, China  

作　　者：Jing Wu Zaixing Jiang 

机构地区：[1]Petroleum Exploration and Production Research Institute of SINOPEC, Beijing 100083, China [2]State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms of SINOPEC, Beijing 100083, China [3]SINOPEC Key Laboratory of Shale Gas/Oil Exploration & Production, Beijing 100083, China [4]Faculty of Energy Resources, China University of Geosciences, Beijing 100083, China

出　　处：《Journal of Earth Science》2017年第6期1006-1019,共14页地球科学学刊（英文版）

基　　金：supported by the National Science and Technology Special Grant of China (No. 2017zx05036-004)

摘　　要：Shale parasequence analysis is an important part of sequence stratigraphy sudies. This paper proposed a systematic research method for analyzing shale parasequences including their delineation, division, characteristics and origins. The division method is established on the basis of lithofacies. Multi-method analysis and mutual verification were implemented by using auxiliary indicators（such as mineral compositions, geochemical indicators and wavelet values）. A typical shale parasequence comprises a lower interval of deepening water-depth and an upper interval of shallowing water-depth（e.g., a shale parasequence including a high-total organic carbon（TOC） shale-low-TOC limy shale）. Abrupt increases in pyrite content, TOC value, relative hydrocarbon generation potential（（S1＋S2）/TOC）, and wavelet values are indicative of parasequence boundaries. The proposed research method was applied to study the upper fourth member of the Shahejie Formation in the Dongying depression, Bohai Bay Basin. Results show that there were seven types of parasequences developed. A singular and a dual structured parasequences were identified. Three factors controlling the development of the shale parasequences were identified including relative lake level change, terrestrial input and transgression. The development of high-TOC（〉2%） shale parasequences was mainly controlled by biological and chemical sedimentation. The low-TOC（〈2%） shale parasequences were mainly deposited by chemical sedimentation. The diversities of shale parasequences were caused by four major controlling factors including climate, relative lake level change, terrestrial input and emergency（e.g., transgression）.Shale parasequence analysis is an important part of sequence stratigraphy sudies. This paper proposed a systematic research method for analyzing shale parasequences including their delineation, division, characteristics and origins. The division method is established on the basis of lithofacies. Multi-method analysis and mutual verification were implemented by using auxiliary indicators（such as mineral compositions, geochemical indicators and wavelet values）. A typical shale parasequence comprises a lower interval of deepening water-depth and an upper interval of shallowing water-depth（e.g., a shale parasequence including a high-total organic carbon（TOC） shale-low-TOC limy shale）. Abrupt increases in pyrite content, TOC value, relative hydrocarbon generation potential（（S1＋S2）/TOC）, and wavelet values are indicative of parasequence boundaries. The proposed research method was applied to study the upper fourth member of the Shahejie Formation in the Dongying depression, Bohai Bay Basin. Results show that there were seven types of parasequences developed. A singular and a dual structured parasequences were identified. Three factors controlling the development of the shale parasequences were identified including relative lake level change, terrestrial input and transgression. The development of high-TOC（〉2%） shale parasequences was mainly controlled by biological and chemical sedimentation. The low-TOC（〈2%） shale parasequences were mainly deposited by chemical sedimentation. The diversities of shale parasequences were caused by four major controlling factors including climate, relative lake level change, terrestrial input and emergency（e.g., transgression）.

关 键 词：SHALE PARASEQUENCE Dongying depression Shahejie Formation 

分 类 号：P539.2[天文地球—古生物学与地层学] P618.13[天文地球—地质学]