Formative mechanisms of high-quality source rocks in continental fault basin of northern South China Sea: a case study from the Eocene Wenchang Formation in Shunde sag,Pearl River Mouth Basin
GAO Mengtian, YOU Li, HU Gaowei, GONG Yu, LI Yanli, CHEN Yabing, FENG Qi, HAN Junwei, LIU Guolin
Abstract：Three sets of favorable source rocks developed in the Eocene Wenchang Formation of the Shunde sag,Pearl River Mouth Basin. However,their stratigraphic attribution,organic matter characteristics and development patterns are unclear. Based on high-resolution 3D seismic,drilling,and geochemical data,this study documents sequence stratigraphic divisions of the Wenchang Formation,and sorted out the characteristics of hydrocarbon source rocks. The current study not only identifies main controlling factors for organic matter enrichment,but also establishes development patterns of high-quality hydrocarbon source rocks of the Wenchang Formation in Shunde sag. Results and observations from the current study suggest that the Eocene Wenchang Formation can be divided into three third-order sequences,among which the sequence SQ2 corresponds to the Member 2 of the Wenchang Formation. The lithofacies of source rocks developed during the development of SQ2 are mainly composed of brown-black and gray-black laminated shale with high organic matter abundance,and are considered as high-quality source rocks. The SQ1 and SQ3 sequences correspond,respectively,to the Members 3 and 1 of the Wenchang Formation. The lithofacies of source rocks developed during the development of SQ1 and SQ3 are mainly composed of dark-gray massive mudstone with silty mudstone with relatively low organic matter abundance. Also,the parent-source types of them were dominated by terrestrial higher plants and aquatic plankton,and the contribution of algae in the SQ2 sequence was more developed. The development of high-quality source rocks in the Wenchang Formation was constrained by tectonism-palaeoclimate coupling,which suggests that palaeoproductivity and palaeoredox conditions are the main controlling factors of organic matter enrichment. In addition,during the development of SQ2 sequence,the strong fault depression intensified volcanic activity which drived higher palaeoproductivity by large amount of volcanic dust subsiding stably. Also,the strong tectonic subsidence and the warm-humid palaeoclimate promoted the rise of lake levels,and the stratification of the water body under temperature control led to the oxygen depletion of the lake bottom water,giving rise to the thick organic-rich shales in the semi-deep lake environment.
GAO Mengtian,YOU Li,HU Gaowei et al. Formative mechanisms of high-quality source rocks in continental fault basin of northern South China Sea: a case study from the Eocene Wenchang Formation in Shunde sag,Pearl River Mouth Basin[J]. JOPC, 2024, 26(5): 1108-1126.
[1] 曹涛涛,邓模,宋之光,刘光祥,黄俨然. 2018. 黄铁矿对页岩油气富集成藏影响研究. 天然气地球科学,29(3): 404-414. [Cao T T,Deng M,Song Z G,Liu G X,Huang Y R.2018. Study on the effect of pyrite on the accumulation of shale oil and gas. Natural Gas Geoscience,29(3): 404-414] [2] 陈烨菲,赵伦,侯珏,李毅,王淑琴,李建新. 2024. 滨里海盆地东缘北特鲁瓦油田石炭系层序地层与沉积演化特征. 古地理学报,26(1): 58-74. [Chen Y F,Zhao L,Hou Y,Li Y,Wang S Q,Li J X.2024. Carboniferous sequence stratigraphy and sedimentary evolution in the North Troyes Oilfield,eastern margin of the Pre-Caspian Basin. Journal of Palaeogeography(Chinese Edition),26(1): 58-74] [3] 高梦天,陆永潮,杜学斌,马义权,张靖宇,邓空. 2021. 致密砂岩多因子储层精细分级评价方法: 以东海盆地西湖凹陷渐新统花港组上段H3砂组为例. 石油实验地质,43(6): 1097-1106. [Gao M T,Lu Y C,Du X B,Ma Y Q,Zhang J Y,Deng K.2021. Multi-factor evalution for fine grading of tight sandstone reservoirs: a case study from H3 sand group in the upper section. Petroleum Geology & Experiment,43(6): 1097-1106] [4] 高梦天,牟必鑫,崔钦宇,陈杨,魏洪刚,张靖宇,邓空,陆永潮. 2022. 西昌盆地上三叠统白果湾组层序格架下沉积演化及油气勘探意义. 天然气地球科学,33(10): 1611-1627. [Gao M T,Mou B X,Cui Q Y,Chen Y,Wei H G,Zhang J Y,Deng K,Lu Y C.2022. Sedimentary evolution under the sequence framework of the Upper Triassic Baiguowan Formation in Xichang Basin and its significance for oil and gas exploration. Natural Gas Geoscience,33(10): 1611-1627] [5] 何雁兵,雷永昌,邱欣卫,肖张波,郑仰帝,刘冬青. 2024. 珠江口盆地陆丰南地区文昌组沉积古环境恢复及烃源岩有机质富集主控因素研究. 地学前缘,31(2): 359-376. [He Y B,Lei Y C,Qiu X W,Xiao Z B,Zheng Y D,Liu D Q.2024. Sedimentary paleoenvironment and main controlling factorsoforganic enrichment in source rocks of the Wenchang Formation in southern Lufeng,Pearl River Mouth Basin. Earth Science Frontiers,31(2): 359-376] [6] 胡笙,谭秀成,罗冰,张本健,张亚,苏成鹏,芦飞凡,李明隆. 2020. 四川盆地西北部二叠系栖霞阶层序地层特征及地质意义. 古地理学报,22(6): 1109-1126. [Hu S,Tan X C,Luo B,Zhang B J,Zhang Y,Su C P,Lu F F,Li M L.2020. Sequence stratigraphic characteristics and geological significance of the Permian Qixia Stage in northwestern Sichuan Basin. Journal of Palaeogeography(Chinese Edition),22(6): 1109-1126] [7] 胡宗全,高志前,刘旺威,卫端. 2023. 塔里木盆地东北缘兴地断裂以北地区下寒武统富有机质泥页岩沉积环境与发育机制. 古地理学报,25(6): 1235-1256. [Hu Z Q,Gao Z Q,Liu W W,Wei D.2023. Depositional environments and formational mechanisms of the Lower Cambrian organic-rich mud/shales,north of Xingdi Fault,northeastern Tarim Basin. Journal of Palaeogeography(Chinese Edition),25(6): 1235-1256] [8] 李辉,姜振学,徐旭辉,邓勇,范彩伟,谭建财,付大巍. 2023. 珠三拗陷南断裂带新生代发育演化的分段性及其对区域构造背景的响应. 地球科学,48(12): 4575-4585. [Li H,Jiang Z X,Xu X H,Deng Y,Fan C W.2023. Segmentation of Cenozoic Development and Evolution of Southern Fault Zone in Zhu-3 Depression and Its Response to Regional Tectonic Setting. Earth Science,48(12): 4575-4585] [9] 刘雨晴,吴智平,程燕君,吴克强,何敏,张杰,张勐,陈明明. 2019. 南海北缘古近纪裂陷结构时空差异及控制因素: 以珠江口盆地为例. 中国矿业大学学报,48(2): 367-376. [Liu Y Q,Wu Z P,Cheng Y J,Wu K Q,He M,Zhang J,Zhang M,Chen M M.2019. Spatial and temporal difference of Paleogene rift structure and its controlling factors in the northern South China Sea: a case study of Pearl River Mouth basin. Journal of China University of Mining & Technology,48(2): 367-376] [10] 吕彩丽,张功成,杨东升. 2017. 珠江口盆地珠二坳陷文昌组构造差异性与动力学成因机制. 地学前缘,24(6): 333-341. [Lü C L,Zhang G C,Yang D S.2017. Differential structure and dynamic mechanism of Wenchang formation in the Zhu H depression of the Pearl River mouth basin. Earth Science Frontiers,24(6): 333-341] [11] 马明,漆家福,张远泽,苗全芸,陈玮常,张帅. 2019. 珠江口盆地新生代沉降特征及其影响因素分析. 中国地质,46(2): 269-289. [Ma M,Qi J F,Zhang Y Z,Miao Q Y,Chen W C,Zhang S.2019. An analysis of subsidence characteristics and affecting factors in the Pearl River Mouth Basin in Cenozoic. Geology in China,46(2): 269-289] [12] 孟庆涛,张训,杨亮,高家俊,刘招君,胡菲,邢济麟,张成铭,康嘉楠,崔博,董秦玮,张恩威. 2024. 陆相拗陷湖盆细粒沉积有机质富集机制研究: 以松辽盆地长岭凹陷青山口组为例. 古地理学报,26(2): 401-415. [Meng Q T,Zhang X,Yang L,Gao J J,Liu Z J,Hu F,Xing J L,Zhang C M,Kang J N,Cui B,Dong Q W,Zhang E W.2024. Mechanism study of organic matter enrichment in fine-grained sediments in continental depression lacustrine basin: an example from the Qingshankou Formation in Changling Sag,Songliao Basin. Journal of Palaeogeography(Chinese Edition),26(2): 401-415] [13] 米立军,张功成,刘志峰,陈莹,白志钊. 2023. 中国近海富油凹陷湖相优质烃源岩发育机制. 石油学报,44(3): 405-419,509. [Mi L J,Zhang G C,Liu Z F,Chen Y,Bai Z Z.2023. Discussion on the development mechanism of lacustrine high-quality source rocks in oil-rich sags in offshore China. Acta Petrolei Sinica,44(3): 405-419,509] [14] 牟传龙,王秀平,王启宇,周恳恳,梁薇,葛祥英,陈小炜. 2016. 川南及邻区下志留统龙马溪组下段沉积相与页岩气地质条件的关系. 古地理学报,18(3): 457-472. [Mou C L,Wang X P,Wang Q Y,Zhou K K,Liang W,Ge X Y,Chen X W.2016. Relationship between sedimentary facies and shale gas geological conditions of the Lower Silurian Longmaxi Formation in southern Sichuan Basin and its adjacent areas. Journal of Palaeogeography(Chinese Edition),18(3): 457-472] [15] 彭光荣,陈聪,龙祖烈,张丽丽,汪旭东,马勇,辛志源,翟普强. 2023. 白云凹陷烃源岩有机质富集机理. 地质学报,97(12): 4164-4178. [Peng G R,Chen C,Long Z L,Zhang L L,Wang X D,Ma Y,Xin Z Y,Zhai P Q.2023. Organic matter enrichment mechanism of different types of source rocks in the Baiyun sag. Acta Geologica Sinica,97(12): 4164-4178] [16] 单玄龙,牟汉生,刘玉虎,李瑞磊,朱建峰,石云倩,冷庆磊,衣健. 2023. 湖盆水下喷发火山岩相类型、特征与储集意义: 以松辽盆地南部查干花地区白垩系为例. 石油勘探与开发,50(4): 719-730. [Shan X L,Mu H S,Liu Y H,Li R L,Zhu J F,Shi Y Q,Leng Q L,Yi J.2023. Subaqueous volcanic eruptive facies,facies model and its reservoir significance in a continental lacustrine basin: a case from the Cretaceous in Chaganhua area of southern Songliao Basin,NE China. Petroleum Exploration and Development,50(4): 719-730] [17] 庹雷,胡林,周杰,刘海钰,梁刚. 2023. 珠江口盆地顺德凹陷稠油特征及成因分析. 中国海上油气,35(5): 14-23. [Tuo L,Hu L,Zhou J,Liu H Y,Liang G.2023. Characteristics and genesis of Paleogene heavy oil in Shunde sag of the Pearl River Mouth Basin. China Offshore Oil and Gas,35(5): 14-23] [18] 谢浩然,梁超,吴靖,籍士超. 2023. 火山活动对沉积古环境及有机质富集的影响. 古地理学报,25(4): 768-787. [Xie H R,Liang C,Wu J,Ji S C.2023. Impacts of volcanic activity on sedimentary palaeo-environment and organic matter enrichment. Journal of Palaeogeography(Chinese Edition),25(4): 768-787] [19] 徐长贵,赖维成,张新涛,张锦伟. 2023. 中国海油油气勘探新进展与未来勘探思考. 中国海上油气,35(2): 1-12. [Xu C G,Lai W C,Zhang X T,Zhang J W.2023. New progress and future exploration thinking of CNOOC oil and gas exploration. China Offshore Oil and Gas,35(2): 1-12] [20] 殷树铮,郭文建,李新宁,周志超,刘文辉,焦立新,何登发. 2024. 准噶尔盆地西部坳陷带二叠系构造—地层层序与盆地演化. 古地理学报,26(1): 132-149. [Yin S Z,Guo W J,Li X N,Zhou Z C,Liu W H,Jiao L X,He D F.2024. Tectono-stratigraphic sequence and basin evolution in West Depression of Junggar Basin. Journal of Palaeogeography(Chinese Edition),26(1): 132-149] [21] 张功成,刘震,米立军,沈怀磊,郭瑞. 2009. 珠江口盆地—琼东南盆地深水区古近系沉积演化. 沉积学报,27(4): 632-641. [Zhang G C,Liu Z,Mi L J,Shen H L,Guo R.2009. Sedimentary evolution of Paleogene series in deep water area of Zhujiangkou and Qiongdongnan Basin. Acta Sedimentologica Sinica,27(4): 632-641] [22] 张功成. 2010. 南海北部陆坡深水区构造演化及其特征. 石油学报,34(4): 528-533,541. [Zhang G C.2010. Tectonic evolution of deepwater area of northern continental margin in South China Sea. Acta Petrolei Sinica,34(4): 528-533,541] [23] 张美洲,朱筱敏,姜振学,朱德宇,叶蕾,谌志远. 2023. 陆相淡水湖盆页岩有机质富集主控因素研究: 以四川盆地东北部侏罗系自流井组为例. 古地理学报,25(4): 806-822. [Zhang M Z,Zhu X M,Jiang Z X,Zhu D Y,Ye L,Chen Z Y.2023. Main controlling factors of organic matter enrichment in continental freshwater lacustrine shale: a case study of the Jurassic Ziliujing Formation in northeastern Sichuan Basin. Journal of Palaeogeography(Chinese Edition),25(4): 806-822] [24] 赵娜,曹瑞华,黄廷林,文刚. 2023. 水源水库温跃层溶解氧最小值条件下天冬氨酸的转化规律与机制. 中国环境科学,43(10): 5529-5542. [Zhao N,Cao R H,Huang T L,Wen G.2023. Transformation and mechanism of aspartic acid under metalimnetic oxygen minimum condition in water source reservoirs. China Environmental Science,43(10): 5529-5542] [25] 朱筱敏,陈贺贺,葛家旺,谈明轩,刘强虎,张自力,张亚雄. 2022. 陆相断陷湖盆层序构型与砂体发育分布特征. 石油与天然气地质,43(4): 746-762. [Zhu X M,Chen H H,Ge J W,Tan M X,Liu Q H,Zhang Z L,Zhang Y X.2022. Characterization of sequence architectures and sandbody distribution in continental rift basins. Oil and Gas Geology, 43(4): 746-762] [26] Algeo T J,Ingall E.2007. Sedimentary Corg: pratios,paleocean ventilation,and Phanerozoic atmospheric pO2. Palaeogeography,Palaeoclimatology,Palaeoecology,256(3-4): 130-155. [27] Algeo T J,Tribovillard N.2009. Environmental analysis of paleoceanographic systems based on molybdenum-uranium covariation. Chemical Geology,268(3-4): 211-225. [28] Cao L,Zhang Z H,Li H Y,Zhong N N,Xiao L L,Jin X,Li H.2020. Mechanism for the enrichment of organic matter in the Liushagang Formation of the Weixinan Sag,Beibuwan Basin,China. Marine and Petroleum Geology,122: 104649. [29] Cranwell P A.1977. Organic geochemistry of Cam Loch(Sutherland)sediments. Chemical Geology,20: 205-221. [30] Ding X J,He W J,Liu H L,Guo X G,Zha M,Jiang Z F.2023. Organic matter accumulation in lacustrine shale of the Permian Jimsar sag,Junggar Basin,NW China. Petroleum Science,20: 1327-1346. [31] Fedo C M,Nesbitt W H,Young G M.1995. Unraveling the effects of potassium metasomatism in sedimentary rocks and paleosols,with implications for paleoweathering conditions and provenance. Geology,23(10): 921-924. [32] Ficken K J,Li B,Swain D L,Eglinton G.2000. An n-alkane proxy for the sedimentary input of submerged/floating freshwater aquatic macrophytes. Organic Geochemistry,31(7-8): 745-749. [33] He C,Ji L M,Su A,Wu Y D,Zhang M Z,Zhou S X,Li J,Hao L W,Ma Y.2017. Source-rock evaluation and depositional environment of black shales in the Triassic Yanchang Formation,southern Ordos Basin,north-central China. Journal of Petroleum Science and Engineering,173: 899-911. [34] Huang W Y,Meinschein W G.1979. Sterols as ecological indicators. Geochim Cosmochim Acta,43: 739-745. [35] Katz B J.1995. Factors controlling the development of lacustrine petroleum source rocks-an update. AAPG Studies in Geology,40: 61-79. [36] Li Q Q,Xu S,Hao F,Shu Z G,Chen F L,Lu Y C,Wu S Q,Zhang L.2021. Geochemical characteristics and organic matter accumulation of argillaceous dolomite in a saline lacustrine basin: a case study from the paleogene xingouzui formation,Jianghan Basin,China. Marine and Petroleum Geology,128: 105041. [37] Li C,Chen S J,Liao J B,Hou Y T,Yu J,Liu G L,Xu K,Wu X T.2023. Geochemical characteristics of the Chang 7 Member in the southwestern Ordos Basin,China: the influence of sedimentary environment on the organic matter enrichment. Palaeoworld,3: 1-13. [38] Liang H R,Xu G S,Xu F H,Yu Q,Liang J J,Wang D Y.2020. Paleoenvironmental evolution and organic matter accumulation in an oxygen-enriched lacustrine basin: a case study from the Laizhou Bay Sag,southern Bohai Sea(China). International Journal of Coal Geology,217: 103318. [39] Ma Y Q,Fan M J,Lu Y C,Liu H M,Hao Y Q,Xie Z H,Liu Z H,Peng L,Du X B,Hu H Y.2016. Climate-driven paleolimnological change controls lacustrine mudstone depositional process and organic matter accumulation: constraints from lithofacies and geochemical studies in the Zhanhua Depression,eastern China. International Journal of Coal Geology,167: 103-118. [40] McLennan S M.1993. Weathering and global denudation. The Journal of Geology,101: 295-303. [41] Nesbitt H W,Young G M.1982. Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature,299: 715-717. [42] Pietras J T,Dennett A,Selby D,Birdwell J E.2022. The role of organic matter diversity on the Re-Os systematics of organic-rich sedimentary units: insights into the controls of isochron age determinations from the lacustrine Green River Formation. Chemical Geology,604: 120939. [43] Qiu Z,He J L.2022. Depositional environment changes and organic matter accumulation of Pliensbachian-Toarcian lacustrine shales in the Sichuan basin,SW China. Journal of Asian Earth Sciences,232: 105035. [44] Quan Y B,Hao F,Liu J Z,Zhao D J,Tian J Q,Wang Z F.2017. Source rock deposition controlled by tectonic subsidence and climate in the western Pearl River Mouth Basin,China: evidence from organic and inorganic geochemistry. Marine and Petroleum Geology,79: 1-17. [45] Sun P C,Sachsenhofer R F,Liu Z J,Strobl S A I,Meng Q T,Liu R,Zhen Z.2013. Organic matter accumulation in the oil shale-and coal-bearing Huadian Basin(Eocene;NE China). International Journal of Coal Geology,105: 1-15. [46] Tribovillard N,Algeo T J,Lyons T,Riboulleau A.2006. Trace metal as paleoredox and paleoproductivity proxies: an update. Chemical Geology: 12-32. [47] Wang C,Wang Q X,Chen G J,He L,Xu Y,Chen L Y,Chen D F.2017. Petrographic and geochemical characteristics of the lacustrine black shales from the Upper Triassic Yanchang Formation of the Ordos Basin,China: implications for the organic matter accumulation. Marine and Petroleum Geology,86: 52-65. [48] Wang Y X,Xu S,Hao F,Poulton S,Zhang Y Y,Guo T X,Lu Y B, Nan B.2021. Arid climate disturbance and the development of salinized lacustrine oil shale in the Middle Jurassic Dameigou Formation,Qaidam Basin,northwestern China. Palaeogeography,Palaeoclimatology,Palaeoecology,577: 110533. [49] Wu Z R,Grohmann S,Littke R,Guo T X,He S,Baniasad A.2022a. Organic petrologic and geochemical characterization of petroleum source rocks in the Middle Jurassic Dameigou Formation,Qaidam Basin,northwestern China: insights into paleo-depositional environment and organic matter accumulation. International Journal of Coal Geology,259: 104038. [50] Wu Z R,He S,He Z L,Li X C,Zhai G Y,Huang Z Q.2022b. Petrographical and geochemical characterization of the Upper Permian Longtan formation and Dalong Formation in the Lower Yangtze region,South China: implications for provenance,paleoclimate,paleoenvironment and organic matter accumulation mechanisms. Marine and Petroleum Geology,139: 105580. [51] Xu C,Shan X L,Lin H M,Hao G L,Liu Pe,Wang X D,Shen M R,Rexiti Y,Li K,Li Z S,Wang X M,Du X D,Zhang Z W,Jia P M,He W T.2022. The formation of early Eocene organic-rich mudstone in the western Pearl River Mouth Basin,South China: insight from paleoclimate and hydrothermal activity. International Journal of Coal Geology,253: 103957. [52] Zdravkova A,Bechtel A,Sachsenhofer R F,Kortenskia J.2017. Palaeoenvironmental implications of coal formation in Dobrudzha Basin,Bulgaria: insights from organic petrological and geochemical properties. International Journal of Coal Geology,180: 1-17. [53] Zhou Q S,Liu J Y,Ma B,Li C,Xiao Y Y,Chen G J,Lyu C F.2024. Pyrite characteristics in lacustrine shale and implications for organic matter enrichment and shale oil: a case study from the Triassic Yanchang Formation in the Ordos Basin,NW China. ACS Omega,9: 16519-16535.
