塔中西北部上奥陶统丘状地震反射异常体的成因
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摘要
塔中地区上奥陶统良里塔格组富含礁滩沉积体,由于礁体具有丘状外形,因此人们普遍将其北西部台缘外带的丘状地震反射体解释为生物礁。本文通过地震地质综合分析,认为上奥陶统生物礁个体较小,其厚度小于1/8波长,宽度小于1个菲涅尔带半径,在常规地震资料中不能直接辨别,真正的礁滩沉积体总是隐伏于代表大套灰岩层顶面的极强反射波(T74)及其之下的1￣2个弱反射波之中。那些位于极强反射波(T74)之上,内部为低频强振幅层状反射波结构的丘状体,其地层结构表现为灰岩(或泥质灰岩)与泥岩互层,为低能与高能过渡带的沉积环境的产物,内含礁滩沉积体的概率也很低。精细解释表明,此类丘状体是低倾角逆断层构造、斜坡滑塌堆积及浊积扇等非礁滩沉积体的地震响应。
The Lianglitage formation of Upper Ordovician is rich in reef, which led the domal seismic anomaly bodies in Tazhong area of Tarim basin to be interpreted as reef in recent years. According to the integrated study of seismic and geological analysis, it is indicated that the reef or multiple circled complex reef-banks can not be recognized directly in conventional seismic profiles because the thickness of the reef is less than one eighth of wavelength, the width of it is less than one radius of Fresnel zone. Reefs or complex reef-banks are always invisible and intermixed in the strong reflection (T74), the top boundary of successive carbonate overlain by interbedded limestone and mud or/and the under 1~2 feeble and discontinuous reflections. Those domal seismic anomaly bodies overlying the strong reflection of T74, with inner bedding configuration composed of mid-strong reflections, reflect the interbedded configuration of limestone or argillaceous limestone with mudstone, which are the products of sedimentary environment with low- and high-energy transition zones, and the low probability of reef-bank deposits within them. The accurate interpretation shows that such domal bodies are the seismic reflections of non-reef-bank deposits of low angle thrust faults, slope slump accumulative zones and turbidite fans.
The Lianglitage formation of Upper Ordovician is rich in reef, which led the domal seismic anomaly bodies in Tazhong area of Tarim basin to be interpreted as reef in recent years. According to the integrated study of seismic and geological analysis, it is indicated that the reef or multiple circled complex reef-banks can not be recognized directly in conventional seismic profiles because the thickness of the reef is less than one eighth of wavelength, the width of it is less than one radius of Fresnel zone. Reefs or complex reef-banks are always invisible and intermixed in the strong reflection (T74), the top boundary of successive carbonate overlain by interbedded limestone and mud or/and the under 1~2 feeble and discontinuous reflections. Those domal seismic anomaly bodies overlying the strong reflection of T74, with inner bedding configuration composed of mid-strong reflections, reflect the interbedded configuration of limestone or argillaceous limestone with mudstone, which are the products of sedimentary environment with low- and high-energy transition zones, and the low probability of reef-bank deposits within them. The accurate interpretation shows that such domal bodies are the seismic reflections of non-reef-bank deposits of low angle thrust faults, slope slump accumulative zones and turbidite fans.
引文
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[2]Robert Riding,Structure and composition oforganic reefs and carbonate mud mounds:concepts and categories.Earth-Sci-ence Reviews[J].2002,(58):163-231.
[3]李洪辉,周东廷,丛祝安.塔里木盆地地震反射异常体及其地质属性初探[J].石油勘探与开发,2001,28(2):50-53.
[4]欧阳睿,焦存礼,白利华,等.塔里木盆地塔中地区生物礁特征及分布[J].石油勘探与开发,2003,30(2):33-36.
[5]李洪革,韩宇春.塔中地区中、上奥陶统有利油气富集的地震相特征及分布[J].石油地球物理勘探,2003,38(2):194-198.
[6]朱俊玲,张继腾,焦存礼,等.塔中地区顺西区块中、上奥陶统异常体与圈闭评价[J].石油勘探与开发,2004,31(5):34-37.
[7]Michael B E.Practical seismic interpretation[M].Boston,USA:IHRDC,1985.104-110.
[8]徐国强,刘树根,李国蓉,等.塔北塔中古隆起形成演化及油气地质条件对比[J].石油与天然气地质,2005,26(1):114-119.
[9]朱忠德,刘秉理,王泽中.塔里木盆地北部中、晚奥陶世生物礁新发现[J].江汉石油学院学报,2000,22(3):111.
[10]肖传桃,蒋维东,潘云唐.塔里木盆地轮南地区奥陶纪生物礁[J].中国区域地质,1996,(4):330-333.
[11]陈景山,王振宇,代宗仰,等.塔中地区中、上奥陶统台地镶边体系分析[J].古地理学报,1999,1(2):8-17.
[12]顾家裕,方辉,蒋凌志.塔里木盆地奥陶系生物礁的发现及其意义[J].石油勘探与开发,2001,28(4):1-3.
[13]邬光辉,李启明,张宝收,等.塔中Ⅰ号断裂坡折带构造特征及勘探领域[J].石油学报,2005,26(1):27-31.
[14]孔金平,刘效曾.塔里木盆地塔中5井下奥陶统隐藻类生物礁[J].新疆石油地质,1998,19(3):221-224.
[15]罗平,张兴阳,顾家裕,等,塔里木盆地奥陶系生物礁露头的地球物理特征[J].沉积学报,2003,21(3):423-427.
[16]徐国强,王英民,陆正元.模型正演与川中二叠系中小断层精细地质解释[J].石油物探,1993,32(1):74-82.
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