南沙群岛海域北康盆地生物礁高精度层序地层学及其新近纪生物礁层序演化模式
摘要
新近系生物礁油气储层是南海含油气盆地油气勘探两大主力目的层系之一,过去有关其高精度层序地层学和层序演化模式的研究不多。为此,通过对北康盆地2万余公里地震资料的精细解释和钻井资料的综合研究,获得了以下重要成果:1)识别划分出该盆地新近纪11条主要等时界面、7个三级层序和基本层序组。2)描述了生物礁低位体系域、海侵体系域和高位体系域地震反射结构特征。3)提出南海首个中中新世生物礁高精度层序演化模式,代表中中新世(16.3—10.4Ma BP)海宁期(T13—T2)生物礁的剖面形态,含由1个低位体系域层序单元+5个高位体系域层序单元构成的一个典型海进体系域和由1个早期高位体系域层序单元+1个晚期高位体系域层序单元构成的1个典型高位体系域;可见中中新世完整海进-海退旋回生物礁发生、发展和消亡的过程。通过与曾母盆地中新世生物礁解释剖面对比,指出该模式具有区域性古海洋学代表意义。4)通过对L礁、西琛一井和南海-地中海中新世古海洋演化研究,确定研究区中中新世分别发育5—8个海平面升降旋回,形成晚中新世"南中国海事件",具有冰川型海退性质,可与全球和南海北部特别是与"Missinian"事件对比;确定北康盆地乃至南海新近系生物礁形成至逐渐消亡,也是新构造运动与新近纪古海洋事件共同作用的结果。5)指出L礁气田发现有9.8MaBP、13.8Ma BP、14.5Ma BP和15.5Ma BP等多个层序界面,分别系高孔渗层段;同期南海礁型油气圈闭层序界面当为优良储层;若其为油气充满,则油气"高产"或构成"高压气包"。以上成果,将有助于对全球变化及南海古海洋区域响应过程与结果的理解,并对南海的油气勘探有启示作用。
Neogene organic reef oil reservoirs are one of the two main target strata systems for petroleum explorations in the South China Sea petroliferous basins.Previously,there was little research on high-precision sequence stratigraphy and sequential evolvement of such target strata.Recently,a precise interpretation of over 20 000km seismic data is carried out,and the drilling data of the basin are comprehensively studied.The following is the important knowledge acquired.1)Through identification and division,there are mainly 11 Neogene isochronous interfaces and 7 third-order sequence units and basic sequence sets.2) The seismic reflection configuration characteristics of low-stand system domain,transgressive domain and high-stand system domain of organic reefs are described.3) The first high-precision model for sequence evolution of the mid-Miocene organic reefs in the South China Sea is given,and this sequence shows a complete transgressive cyclic process of an organic reef from generation to development and then to extinction during the Haining Period of the mid-Miocene(6.3-10.4 Ma BP).Of the model,a typical transgressive system domain consists of a low-stand system domain(a sequence unit) and a high-stand system domain(five sequence units),and a typical high-stand system domain is composed of an early high-stand system domain sequence unit and a late high-stand system domain sequence unit.Through comparison with the Miocene bioherm interpretation section from the Zengmu Basin,the above mentioned model is of great oceanographic significance.4) Through the study on the Miocene paleo-oceanographic evolution in the areas of Reef L,Xichen-1 well and in the South China Sea-Mediterranean areas,we find 5-8 glacial regressive cycles,which formed the "South China Sea Event" in the late Miocene and corresponded to the "Missinian Event" in the global eustatic cycles in the Miocene.The "South China Sea Event" was a joint action of Neotectonic movements and Neogene oceanographic events,and it controlled the growth and extinction of the early Miocene organic reef in the Beikang Basin or even in the whole South China Sea.5) It is pointed out that multiple sequence-depth interfaces have been found in the oil-gas-producing layers of Reef L gas field(pool),such as those about 9.8,13.8,14.5 and 15.5 Ma BP,each of which has formed a section of high permeability.Therefore,it is thought that if there are sequences of similar type in the corresponding bioherm oil traps in the South China Sea,they could be excellent oil reservoirs,and if they are filled with oil and gas,they can give "high oil production" or form "high pressure gas bodies".The study will be useful for understanding the Miocene organic reef sequence formation in the Beikang Basin as well as the consequence and process of its response to the global changes in the ancient South China Sea areas,and therefore provides useful information for petroleum explorations in the South China Sea.
Neogene organic reef oil reservoirs are one of the two main target strata systems for petroleum explorations in the South China Sea petroliferous basins.Previously,there was little research on high-precision sequence stratigraphy and sequential evolvement of such target strata.Recently,a precise interpretation of over 20 000km seismic data is carried out,and the drilling data of the basin are comprehensively studied.The following is the important knowledge acquired.1)Through identification and division,there are mainly 11 Neogene isochronous interfaces and 7 third-order sequence units and basic sequence sets.2) The seismic reflection configuration characteristics of low-stand system domain,transgressive domain and high-stand system domain of organic reefs are described.3) The first high-precision model for sequence evolution of the mid-Miocene organic reefs in the South China Sea is given,and this sequence shows a complete transgressive cyclic process of an organic reef from generation to development and then to extinction during the Haining Period of the mid-Miocene(6.3-10.4 Ma BP).Of the model,a typical transgressive system domain consists of a low-stand system domain(a sequence unit) and a high-stand system domain(five sequence units),and a typical high-stand system domain is composed of an early high-stand system domain sequence unit and a late high-stand system domain sequence unit.Through comparison with the Miocene bioherm interpretation section from the Zengmu Basin,the above mentioned model is of great oceanographic significance.4) Through the study on the Miocene paleo-oceanographic evolution in the areas of Reef L,Xichen-1 well and in the South China Sea-Mediterranean areas,we find 5-8 glacial regressive cycles,which formed the "South China Sea Event" in the late Miocene and corresponded to the "Missinian Event" in the global eustatic cycles in the Miocene.The "South China Sea Event" was a joint action of Neotectonic movements and Neogene oceanographic events,and it controlled the growth and extinction of the early Miocene organic reef in the Beikang Basin or even in the whole South China Sea.5) It is pointed out that multiple sequence-depth interfaces have been found in the oil-gas-producing layers of Reef L gas field(pool),such as those about 9.8,13.8,14.5 and 15.5 Ma BP,each of which has formed a section of high permeability.Therefore,it is thought that if there are sequences of similar type in the corresponding bioherm oil traps in the South China Sea,they could be excellent oil reservoirs,and if they are filled with oil and gas,they can give "high oil production" or form "high pressure gas bodies".The study will be useful for understanding the Miocene organic reef sequence formation in the Beikang Basin as well as the consequence and process of its response to the global changes in the ancient South China Sea areas,and therefore provides useful information for petroleum explorations in the South China Sea.
引文
[1]许红,王玉净.西沙中新世生物地层,藻类的造礁作用与生物礁演变特征[M].北京:科学出版社,1999.
[2]MAY J A,EYLES D.Well Log and Seismic Character ofTertiary Terumbu Carbonate,South China Sea,Indonesia[J].AAPG Bulletin,1985,69(9):1339—1358.
[3]VAIL P R.Seismic stratigraphy interpretation using se-quence stratigraphy[M]//Part 1:seismic stratigraphy in-terpretation procedure.BALLY A W.Atlas of Seismic star-tigraphy.AAPG Studies in Geology,1987,27:1—10.
[4]HAQ B U,HARDENBOL J,VAIL P R.Chronology offluctuating sea level since the Triassic[J].Science,1987,235:1 156—1 167.
[5]秦国权.微体古生物在珠江口盆地新生代晚期层序地层学研究中的应用[J].海洋地质与第四纪地质,1996,16(4):1—18.
[6]XU HONG,WANG YUJING,CAI FENG,et al.Evolu-tion of Miocene organic reefs and functions of algae’s reef-making in Xisha Islands[J].Science Bulletin,1999,11,44(21):1 996—2 001.
[7]许靖华.地学革命风云录[M].北京:地质出版社,1985.
[2]MAY J A,EYLES D.Well Log and Seismic Character ofTertiary Terumbu Carbonate,South China Sea,Indonesia[J].AAPG Bulletin,1985,69(9):1339—1358.
[3]VAIL P R.Seismic stratigraphy interpretation using se-quence stratigraphy[M]//Part 1:seismic stratigraphy in-terpretation procedure.BALLY A W.Atlas of Seismic star-tigraphy.AAPG Studies in Geology,1987,27:1—10.
[4]HAQ B U,HARDENBOL J,VAIL P R.Chronology offluctuating sea level since the Triassic[J].Science,1987,235:1 156—1 167.
[5]秦国权.微体古生物在珠江口盆地新生代晚期层序地层学研究中的应用[J].海洋地质与第四纪地质,1996,16(4):1—18.
[6]XU HONG,WANG YUJING,CAI FENG,et al.Evolu-tion of Miocene organic reefs and functions of algae’s reef-making in Xisha Islands[J].Science Bulletin,1999,11,44(21):1 996—2 001.
[7]许靖华.地学革命风云录[M].北京:地质出版社,1985.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心