前陆冲断带下盘的掩伏构造假象分析与校正——以准噶尔盆地东部“火北掩伏带”为例
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摘要
造山带和盆地之间的前陆冲断带及其下盘掩伏带是油气勘探的重要领域,有关其时间域构造假象及时间域剖面复杂构造的研究多集中在高速盐丘、海底峡谷等特殊地貌或地层厚度剧变对下伏构造层成像"上拉、下拽"形成的构造假象方面,而对于火山岩体厚度变化及尖灭对下盘构造成像的影响以及"假断裂、假构造"判识方法的研究则较少。为此,以准噶尔盆地东北部火烧山油田以北石炭系克拉美丽前陆冲断带下盘的掩伏背斜带(以下简称火北掩伏带)为例,通过对火北2井钻探前后验证过程的描述,基于对正演模型、叠前深度偏移剖面及倾角测井等资料的综合分析,探究了该冲断带下盘时间域"假背斜、假断裂"形成的原因。结果表明:(1)地层速度的横向变化可导致速度异常区下伏地层构造形态畸变,出现假构造和构造高点偏离的现象;(2)火北掩伏构造和火14井北断裂是因逆冲断层上盘石炭系火山岩高速层存在且横向厚度突变导致的构造假象;(3)叠前深度偏移技术是解决时间域剖面上构造假象难题的最佳手段,在不具备进行叠前深度偏移条件时可通过建立正确的三维速度场、变速时深转换来实现成图。结论认为:(1)通过建立复杂构造区的典型构造样式及地震构造解释模型,运用模型正演,结合地层倾角测井等成果,可以识别逆掩推覆断裂复杂构造带的真假;(2)探讨火山岩发育的逆掩推覆断裂带的地震解释技术,对于指导研究区勘探目标优选具有实践意义,对类似地区的地震资料解释也具有借鉴作用。
The foreland thrust belts between orogenic zones and basins and the buried structures at their footwalls are important oil & gas exploration fields.The studies on structural illusions and complex structures in time domain usually focus on the structural illusions that the images of the underlying structures are pulled up or down by the violent change of stratum thickness or special landforms(e.g.highspeed salt dome and submarine canyons).However,the effects of the thickness change and pinchout of volcanic rock matrix on the imaging of footwall structures and the "false fault and false structure" identification methods are rarely researched.In this paper,the buried anticline at the footwall of Carboniferous Kelameili foreland thrust belt to the north of Huoshaoshan Oilfield in the northeastern Junggar Basin(hereinafter "Huobei buried structure" for short) was taken as an example.Firstly,the verification process before and after the drilling of Well HB2 was described.Then,based on the comprehensive analysis of forward modeling,pre-stack depth migration section and diplog,the cause for "false anticline and false fault" at the footwall of Kelameili foreland thrust belt in time domain was discussed.And the following research results were obtained.First,the lateral change of formation velocity can lead to distorted structural forms of the underlying strata in the velocity anomaly zones,and consequently false structure and deviated structural high emerge.Second,Huobei buried structure and Well H14 north fault are the structural illusions which are resulted from the high-velocity layer of Carboniferous volcanics at the hanging wall of thrust fault and the abrupt change of lateral thickness.Third,the pre-stack depth migration technology(PSDM) is the best tool for solving the problem of structure illusion in time-domain section.If PSDM cannot work,the structural map can be obtained by establishing a correct 3D velocity field and conducting variable velocity time–depth conversion.In conclusion,whether the complex structural belt of overthrust nappe fault is true or not can be discriminated by establishing the typical structural pattern and seismic structure interpretation model of complex structure area and applying forward modeling,combined with diplog results.In addition,the discussion on the seismic interpretation technologies used for overthrust nappe faulting zones with developed volcanics is of practical significance to the selection of exploration targets in the study area,and it can be used as the reference for the seismic data interpretation of similar areas as well.
The foreland thrust belts between orogenic zones and basins and the buried structures at their footwalls are important oil & gas exploration fields.The studies on structural illusions and complex structures in time domain usually focus on the structural illusions that the images of the underlying structures are pulled up or down by the violent change of stratum thickness or special landforms(e.g.highspeed salt dome and submarine canyons).However,the effects of the thickness change and pinchout of volcanic rock matrix on the imaging of footwall structures and the "false fault and false structure" identification methods are rarely researched.In this paper,the buried anticline at the footwall of Carboniferous Kelameili foreland thrust belt to the north of Huoshaoshan Oilfield in the northeastern Junggar Basin(hereinafter "Huobei buried structure" for short) was taken as an example.Firstly,the verification process before and after the drilling of Well HB2 was described.Then,based on the comprehensive analysis of forward modeling,pre-stack depth migration section and diplog,the cause for "false anticline and false fault" at the footwall of Kelameili foreland thrust belt in time domain was discussed.And the following research results were obtained.First,the lateral change of formation velocity can lead to distorted structural forms of the underlying strata in the velocity anomaly zones,and consequently false structure and deviated structural high emerge.Second,Huobei buried structure and Well H14 north fault are the structural illusions which are resulted from the high-velocity layer of Carboniferous volcanics at the hanging wall of thrust fault and the abrupt change of lateral thickness.Third,the pre-stack depth migration technology(PSDM) is the best tool for solving the problem of structure illusion in time-domain section.If PSDM cannot work,the structural map can be obtained by establishing a correct 3D velocity field and conducting variable velocity time–depth conversion.In conclusion,whether the complex structural belt of overthrust nappe fault is true or not can be discriminated by establishing the typical structural pattern and seismic structure interpretation model of complex structure area and applying forward modeling,combined with diplog results.In addition,the discussion on the seismic interpretation technologies used for overthrust nappe faulting zones with developed volcanics is of practical significance to the selection of exploration targets in the study area,and it can be used as the reference for the seismic data interpretation of similar areas as well.
引文
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[17]张朝军,贾承造,邹才能,胡云扬.西秋构造带盐下构造圈闭及其天然气成藏条件[J].天然气工业,2010,30(8):1-3.Zhang Chaojun,Jia Chengzao,Zou Caineng&Hu Yunyang.Subsalt structures and geological conditions for gas accumulation in western Qiulitage,Kuqa Foreland Basin[J].Natural Gas Industry,2010,30(8):1-3.
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[2]何登发,管树巍,张年富,吴晓智,张越迁.准噶尔盆地哈拉阿拉特山冲断带构造及找油意义[J].新疆石油地质,2006,27(3):267-269.He Dengfa,Guan Shuwei,Zhang Nianfu,Wu Xiaozhi&Zhang Yueqian.Thrust belt structure and significance for petroleum exploration in Hala'alat Mountain in northwestern margin of Junggar Basin[J].Xinjiang Petroleum Geology,2006,27(3):267-269.
[3]付锁堂.柴达木盆地油气勘探潜在领域[J].中国石油勘探,2016,21(5):1-10.Fu Suotang.Potential oil and gas exploration areas in Qaidam Basin[J].China Petroleum Exploration,2016,21(5):1-10.
[4]宋明水,吕明久,赵乐强,隋风贵.准噶尔盆地车排子凸起油气资源潜力与成藏模式[J].中国石油勘探,2016,21(3):83-91.Song Mingshui,LüMingjiu,Zhao Leqiang&Sui Fenggui.Hydrocarbon potential and accumulation model in Chepaizi Uplift,Junggar Basin[J].China Petroleum Exploration,2016,21(3):83-91.
[5]梁顺军,肖宇.潜伏背斜圈闭优选在强烈挤压断褶区油气勘探的重要性分析--来自天山、龙门山、昆仑山山前逆冲断带及川东高陡背斜区的勘探实例[J].中国石油勘探,2013,18(1):1-14.Liang Shunjun&Xiao Yu.Selection and optimization of buried anticline trap in oil and gas exploration of strongly compressional faulted fold zone:Cases from exploration of Tianshan,Longmen and Kunlun Mountain frontal thrust belts and Chuandong high steep anticline[J].China Petroleum Exploration,2013,18(1):1-14.
[6]陈海清,戴晓云,潘良云,赵叶平,何丽红,陈元忠,等.时间剖面上的假构造及其解决方法[J].石油地球物理勘探,2009,44(5):590-596.Chen Haiqing,Dai Xiaoyun,Pan Liangyun,Zhao Yeping,He Lihong,Chen Yuanzhong,et al.False structures on time domain seismic sections and corresponding resolutions[J].Oil Geophysical Prospecting,2009,44(5):590-596.
[7]梁顺军,肖宇,刁永波,朱亚东,陈燕雄,付建元.库车坳陷山地复杂构造速度场研究及其应用效果[J].中国石油勘探,2011,16(4):59-64.Liang Shunjun,Xiao Yu,Diao Yongbo,Zhu Yadong,Chen Yanxiong&Fu Jianyuan.Velocity field research of complex structures in Kuqa Depression and its application[J].China Petroleum Exploration,2011,16(4):59-64.
[8]梁顺军,吴超,唐怡,雷刚林,冯磊,李乐,等.库车坳陷盐下构造畸变特征分析和校正[J].新疆石油地质,2009,30(5):571-575.Liang Shunjun,Wu Chao,Tang Yi,Lei Ganglin,Feng Lei,Li Le,et al.Analysis and correction of distorted subsalt structure in Kuqa Depression[J].Xin Jiang Petroleum Geology,2009,30(5):571-575.
[9]肖宇,梁顺军,倪华玲,吴育林,汪少华,许勇,等.有关山地地震勘探构造成果的钻探失利井诠释与解析[J].中国石油勘探,2013,18(4):26-35.Xiao Yu,Liang Shunjun,Ni Hualing,Wu Yulin,Wang Shaohua,Xu Yong,et al.Interpretation and analysis about drilling failure based on mountainous seismic exploration results[J].China Petroleum Exploration,2013,18(4):26-35.
[10]代双河,高军,臧殿光,刘文利.滨里海盆地东缘巨厚盐岩区盐下构造的解释方法研究[J].石油地球物理勘探,2006,41(3):303-307.Dai Shuanghe,Gao Jun,Zang Dianguang&Liu Wenli.Interpretation method of subsalt structures in significant thickness of salt beds,east merging of littoral Caspian Sea Basin[J].Oil Geophysical Prospecting,2006,41(3):303-307.
[11]喻英梅,张英德,彭佳勇.海底峡谷对深部地层时深转换的影响及其消除方法[J].中国海上油气,2008,20(4):236-238.Yu Yingmei,Zhang Yingde&Peng Jiayong.Impact of submarine canyons on time-depth conversion of deeper intervals and its elimination approach[J].China Offshore Oil and Gas,2008,20(4):236-238.
[12]温铁民,苏世龙,钱豫.盐下速度场异常问题分析[J].石油地球物理勘探,2007,42(增刊1):5-7.Wen Tiemin,Su Shilong&Qian Yu.Analysis of abnormal issue in subsalt velocity field[J].Oil Geophysical Prospecting,2007,42(S1):5-7.
[13]张光荣,冉崎,廖奇,喻颐,张旋,陈康,等.四川盆地高磨地区龙王庙组气藏地震勘探关键技术[J].天然气工业,2016,36(5):31-37.Zhang Guangrong,Ran Qi,Liao Qi,Yu Yi,Zhang Xuan,Chen Kang,et al.Key seismic exploration technology for the Longwangmiao Fm gas reservoir in Gaoshiti-Moxi area,Sichuan Basin[J].Natural Gas Industry,2016,36(5):31-37.
[14]王波,王雪梅.滨里海盆地下盐下构造假象识别及真实形态恢复[J].中国石油勘探,2008,13(1):63-67Wang Bo&Wang Xuemei.Research on pro-salt pseudo structures identification and real shapes restoration in salt dome areas of Pre-Caspian Basin[J].China Petroleum Exploration,2008,13(1):63-67.
[15]张研,徐凌,陈立康.前陆冲断带复杂构造地震成像技术对策[J].石油勘探与开发,2005,32(5):62-64.Zhang Yan,Xu Ling&Chen Likang.Technical countermeasure of seismic imaging for complex structure in foreland overthrust belt[J].Petroleum Exploration and Development,2005,32(5):62-64.
[16]李素华.常规地震解释中波阻抗差异引起的构造假象研究[J].科学技术与工程,2012,12(26):6754-6758.Li Suhua.The research of pseudo structure in typical interpretation for impedance difference[J].Science Technology and Engineering,2012,12(26):6754-6758.
[17]张朝军,贾承造,邹才能,胡云扬.西秋构造带盐下构造圈闭及其天然气成藏条件[J].天然气工业,2010,30(8):1-3.Zhang Chaojun,Jia Chengzao,Zou Caineng&Hu Yunyang.Subsalt structures and geological conditions for gas accumulation in western Qiulitage,Kuqa Foreland Basin[J].Natural Gas Industry,2010,30(8):1-3.
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