利用重磁资料研究西非中南段含盐盆地构造区划
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摘要
西非中南段含盐盆地位于大西洋东岸浅海区,在构造演化的过渡阶段形成了巨厚的Aptian期蒸发盐岩,将该区分为盐上层、盐层和盐下层三个构造层序.而盐岩的遮蔽效应使得盐下层地震反射品质差、盐下层序研究程度低,致使裂谷主控断裂、裂谷规模及展布形态不清楚.本文利用重、磁资料覆盖面广、横向分辨能力强、受盐岩影响小的优势,结合地震及地质资料,研究了西非中南段含盐盆地盐下构造格局.通过研究表明,西非中南段含盐盆地整体呈现"东西分带,南北分块"的构造特征;重新厘定了里奥穆尼、加蓬、下刚果和宽扎4个含盐盆地边界;识别了2个盐下裂谷带及其内部28个盐下凹陷,盐下凹陷呈现垒堑相间的结构特征;推断了盐下一级断裂16条,二级断裂23条,呈现"东西拉张,北东走滑"的力学特征.该项研究成果为该区盐下地震层序再解释、盐下油气战略选区及下一步勘探部署提供了地球物理依据.
The salt-bearing basins in south-central section of West Africa are located on the east coast of the Atlantic Ocean.The thick salt rock formed during the Aptian period that happened at the transition stage of structural evolution,which is divided into three tectonic sequences:upper salt layer,salt layer and lower salt layer.It is a big challenge to research the major faults that control the boundaries of rifts and morphological dimensions of rifts based on the poor-qualityseismic reflection data that is influenced by the shading effect of salt rock.In this paper,we study the subsalt structure of salt-bearing basins in this region using gravity and magnetic anomaly data which have several advantages such as wide area coverage,strong horizontal resolution and less effect from salt rock.In addition,combining the seismic reflection and geologic data,we further study the tectoniv pattern of subsalt in this area.Results suggest that the salt-bearing basins in south-central section of West Africa are characterized by"zones in eastwest and blocks in south-north".The boundaries of Rio Muni Basin,Gabon Basin,Lower Congo Basin and Kwanza Basin are redefined.Two subsalt rifts and 28 subsalt sags are identiflied,where are present alternating uplifts and depressions.We also infer 16 first-order and 23 secondorder subsalt faults,which exhibit "extension in east-west and strike-slip in north-east".The results of this study provide geophysical supports to the seismic sequence reanalysis,choosing exploration areas of subsalt oil and gas and the exploration deployment in the next step.
The salt-bearing basins in south-central section of West Africa are located on the east coast of the Atlantic Ocean.The thick salt rock formed during the Aptian period that happened at the transition stage of structural evolution,which is divided into three tectonic sequences:upper salt layer,salt layer and lower salt layer.It is a big challenge to research the major faults that control the boundaries of rifts and morphological dimensions of rifts based on the poor-qualityseismic reflection data that is influenced by the shading effect of salt rock.In this paper,we study the subsalt structure of salt-bearing basins in this region using gravity and magnetic anomaly data which have several advantages such as wide area coverage,strong horizontal resolution and less effect from salt rock.In addition,combining the seismic reflection and geologic data,we further study the tectoniv pattern of subsalt in this area.Results suggest that the salt-bearing basins in south-central section of West Africa are characterized by"zones in eastwest and blocks in south-north".The boundaries of Rio Muni Basin,Gabon Basin,Lower Congo Basin and Kwanza Basin are redefined.Two subsalt rifts and 28 subsalt sags are identiflied,where are present alternating uplifts and depressions.We also infer 16 first-order and 23 secondorder subsalt faults,which exhibit "extension in east-west and strike-slip in north-east".The results of this study provide geophysical supports to the seismic sequence reanalysis,choosing exploration areas of subsalt oil and gas and the exploration deployment in the next step.
引文
Blaich O A,Tsikalas F,Faleide J I.2008.Northeastern Brazilian margin:Regional tectonic evolution based on integrated analysis of seismic reflection and potential field data and modelling.Tectonophysics,458(1-4):51-67.
Broucke O,Temple F,Rouby D,et al.2004.The role of deformation processes on the geometry of mud-dominated turbiditic systems,Oligocene and Lower-Middle Miocene of the Lower Congo basin(West African Margin).Marine and Petroleum Geology,21(3):327-348.
Dickson W,Schiefelbein C,Zumberge J,et al.2005.Basin analysis in Brazilian and west African conjugates:Combining disciplines to deconstruct petroleum systems.∥GCSSEPM Foundation 25th Annual BOB F.Perkins Research Conference.Houston TX.
Dickson W G,Fryklund R E,Odegard M E,et al.2003.Constraints for plate reconstruction using gravity data-implications for source and reservoir distribution in Brazilian and West African margin basins.Marine and Petroleum Geology,20(3-4):309-322.
DupréS,Bertotti G,Cloetingh S.2007.Tectonic history along the South Gabon Basin:Anomalous early post-rift subsidence.Marine and Petroleum.Geology,24(3):151-172.
DupréS,Cloetingh S,Bertotti G.2011.Structure of the Gabon Margin from integrated seismic reflection and gravity data.Tectonophysics,506(1-4):31-45.
Gay A,Lopez M,Berndt C,et al.2007.Geological controls on focused fluid flow associated with seafloor seeps in the Lower Congo Basin.Marine Geology,244(1-4):68-92.
Guiraud M,Buta-Neto A,Quesne D.2010.Segmentation and differential post-rift uplift at the Angola margin as recorded by the transform-rifted Benguela and oblique-to-orthogonal-rifted Kwanza basins.Marine and Petroleum Geology,27(5):1040-1068.
Hu W S,Li T,Yu S,et al.2012.Tectonic revolution and forming mechanism of gravitational décollement structures in the passive continental margin of West Africa.Geotectonica et Metallogenia(in Chinese),36(2):186-196.
Ji X L,Wang W Y,Qiu Z Y.2015.The research to the minimum curvature technique for potential field data separation.Chinese Journal of Geophysics(in Chinese),58(3):1042-1058,doi:10.6038/cjg20150329.
Kamgang P,Njonfang E,Nono A,et al.2010.Petrogenesis of a silicic magma system:Geochemical evidence from Bamenda Mountains,NW Cameroon,Cameroon Volcanic Line.Journal of African Earth Science,58(2):285-304.
Letouzey J,Colletta B,Vially R,et al.1995.Evolution of saltrelated structures in compressional settings.∥Jackson M P A,Roberts D G,Snelson S eds.Salt Tectonics:A Global Perspective.Oklahoma:AAPG,65:41-60.
Li L,Wu M N,Li D R.2005.Present hydrocarbon exploration situation and prospect of salt-bearing basin in gabon and its adjacent area.China Petroleum Exploration(in Chinese),10(3):57-63,68.
Li T,Hu W S,Hu F,et al.2012.Gravitational decollement structural development characteristics and its evolutionary history of Rio Muni Basin.Journal of Oil and Gas Technology(in Chinese),34(4):1-6.
Liu G D.1992.Geologic-Geophysic Features of China Seas and Adjacent Regions(in Chinese).Beijing:Science Press.
Liu G D,Hao T Y,Liu Y K.1996.The significance of gravity and magnetic research for knowing sedimentary basins.Progress in Geophysics(in Chinese),11(2):1-15.
Liu Z D,Li J H.2011.Control of salt structures on hydrocarbons in the passive continental margin of West Africa.Petroleum Exploration and Development(in Chinese),38(2):196-202.
Lu B L,Wang W Y,Du X D,et al.2015.Review of tectonicsedimentary features of the central-south section of West African continental margin basins.Advances in Marine Science(in Chinese),33(3):414-428.
Maus S,Barckhausen U,Benkenbosch H,et al.2009.EMAG2:A2-arc min resolution earth magnetic anomaly grid compiled from satellite,airborne,and marine magnetic measurements.Geochemistry,Geophysics,Geosystems,10(8):1-12.
Moulin M,Aslanian D,Olivet J L,et al.2005.Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data(Za6ango project).Geophysical Journal International,162(3):793-810.
Mounguengui M M,Guiraud M.2009.Neocomian to early Aptian syn-rift evolution of the normal to oblique-rifted North Gabon Margin(Interior and N′Komi Basins).Marine and Petroleum Geology,26(6):1000-1017.
Mounguengui M M,Lang J,Guiraud M.2008.Sedimentary dynamics and extensional structuring related to early Cretaceous rifting of Neocomian and Barremian deposits of the interior basin of Gabon.Journal of African Earth Sciences,51(5):239-256
Rao Y Q.2012.Petroleum geological features and exploration prospect of Gabon coastal Basin.Inner Mongulia Petrochemical Industry(in Chinese),(1):147-149.
Sandwell D T,Garcia E,Soofi K,et al.2013.Towards 1-mGal accuracy in global marine gravity from CrySat-2,Envisat,and Jasom-1.The Leading Edge,32(8):892-899.doi:10.1190/tle32080892.1.
Sandwell D T,Müller R D,Smith W H F,et al.2013.New global marine gravity model from CrySat-2and Jasom-1reveals buried tectonic structure.Science,346(6205):65-67.
Sandwell D T,Smith W H F.2009.Global marine gravity from retracked Geosat and ERS-1altimetry:Ridge Segmentation versus spreading rate.J.Geophys.Res.,114:B01411:1-Bo1411:18,.doi:10.1029/2008JB006008.
Teisserence P,Villemin J.1990.Sedimentary basin of Gabon-Geology and oil systems.∥Edwards J D,Santogrossi P A eds.Divergent/passive margin Basins.AAPG,48:117-199.
Turner J P,Rosendahl B R,Wilson P G.2003.Structure and evolution of an obliquely sheared continental margin:Rio Muni,West Africa.Tectonophysics,374(1-2):41-55.
Wang J.Analysis on sub-salt structural characteristics and exploration direction of block LT2000in Gabon.Journal of Oil and Gas Technology(in Chinese),2012,34(1):35-40.
Wang W Y,Pan Y,Qiu Z Y.2009.A new edge recognition technology based on the normalized vertical derivative of the total horizontal derivative for potential field data.Applied Geophysics,6(3):226-233.
Wang W Y,Pan Z S.1993.Fast solution of forward and inverse problems for gravity field in a dual interface model.Geophysical ProspectingforPetroleum(in Chinese),32(2):81-123.
Wang W Y,Qiu Z Y,Yang Y,et al.2010.Some advances in the edge recognition of the potential field.Progress in Geophysics(in Chinese),25(1):196-210,doi:10.3969/j.issn.1004-2903.2010.01.027.
Xiong L P,Liu Y L,Huo H.2010.Comparison of the hydrocarbon accumulation patterns of petroliferous basins between the north and south parts of the West African coast.Oil&Gas Geology(in Chinese),31(4):410-109.
Yang X J,Li J,Yu B S.2012.Structural feature and exploratory potential of the Lower Congo Basin.Progress in Geophysics(in Chinese),27(6):2585-2593,doi:10.6038/j.issn.1004-2903.2012.06.036.
Yang Y C,Zhang S L,Sun Y M,et al.2013.Source rock distribution and petroleum accumulation in Kwanga basin West Africa.Marine Geology Frontiers(in Chinese),29(3):29-36.
Zhang P Q,Zhao Q Y.1996.Methods of the magnetic direction transform of aeromagnetic anomalies with differential inclinations in low magnetic latitudes.Computing Techniques for Geophysical and Geochemical Exploration(in Chinese),18(3):206-214.
胡望水,李涛,于水等.2012.西非被动大陆边缘重力滑脱构造发育演化及成因机制.大地构造与成矿学,36(2):186-196.
纪晓琳,王万银,邱之云.2015.最小曲率位场分离方法研究.地球物理学报,58(3):1042-1058,doi:10.6038/cjg20150329.
李莉,吴慕宁,李大荣.2005.加蓬含盐盆地及邻区油气勘探现状和前景.中国石油勘探,10(3):57-63,68.
李涛,胡望水,胡芳等.2012.里奥穆尼盆地重力滑脱构造发育特征及演化规律.石油天然气学报,34(4):1-6.
刘光鼎.1992.中国海区及邻域地质地球物理特征.北京:科学出版社.
刘光鼎,郝天珧,刘伊克.1996.重磁研究对认识盆地的意义.地球物理学进展,11(2):1-15.
刘祚冬,李江海.2011.西非被动大陆边缘盆地盐构造对油气的控制作用.石油勘探与开发,38(2):196-202.
鲁宝亮,王万银,杜向东等.2015.西非陆缘盆地中南段构造与沉积研究.海洋科学进展,33(3):414-428.
饶轶群.2012.加蓬海岸盆地油气地质特征及勘探前景.内蒙古石油化工,(1):147-149.
王建.2012.加蓬LT2000区块盐下构造特征与勘探方向分析.石油天然气学报,34(1):35-40.
王万银,潘作枢.1993.双界面模型重力场快速正反演问题.石油物探,32(2):81-123.
王万银,邱之云,杨永等.2010.位场边缘识别方法研究进展.地球物理学进展,25(1):196-210,doi:10.3969/j.issn.1004-2903.2010.01.027.
熊利平,刘延莉,霍红.2010.西非海岸南、北两段主要含油气盆地油气成藏特征对比.石油与天然气地质,31(4):410-109.
杨晓娟,李军,于炳松.2012.下刚果盆地构造特征及油气勘探潜力.地球物理学进展,27(6):2585-2593,doi:10.6038/j.issn.1004-2903.2012.06.036.
杨永才,张树林,孙玉梅等.2013.等.西非宽扎盆地烃源岩分布及油气成藏.海洋地质前沿,29(3):29-36.
张培琴,赵群友.1996.低磁纬度区航磁异常变倾角磁方向转换方法.物探化探计算技术,18(3):206-214.
Broucke O,Temple F,Rouby D,et al.2004.The role of deformation processes on the geometry of mud-dominated turbiditic systems,Oligocene and Lower-Middle Miocene of the Lower Congo basin(West African Margin).Marine and Petroleum Geology,21(3):327-348.
Dickson W,Schiefelbein C,Zumberge J,et al.2005.Basin analysis in Brazilian and west African conjugates:Combining disciplines to deconstruct petroleum systems.∥GCSSEPM Foundation 25th Annual BOB F.Perkins Research Conference.Houston TX.
Dickson W G,Fryklund R E,Odegard M E,et al.2003.Constraints for plate reconstruction using gravity data-implications for source and reservoir distribution in Brazilian and West African margin basins.Marine and Petroleum Geology,20(3-4):309-322.
DupréS,Bertotti G,Cloetingh S.2007.Tectonic history along the South Gabon Basin:Anomalous early post-rift subsidence.Marine and Petroleum.Geology,24(3):151-172.
DupréS,Cloetingh S,Bertotti G.2011.Structure of the Gabon Margin from integrated seismic reflection and gravity data.Tectonophysics,506(1-4):31-45.
Gay A,Lopez M,Berndt C,et al.2007.Geological controls on focused fluid flow associated with seafloor seeps in the Lower Congo Basin.Marine Geology,244(1-4):68-92.
Guiraud M,Buta-Neto A,Quesne D.2010.Segmentation and differential post-rift uplift at the Angola margin as recorded by the transform-rifted Benguela and oblique-to-orthogonal-rifted Kwanza basins.Marine and Petroleum Geology,27(5):1040-1068.
Hu W S,Li T,Yu S,et al.2012.Tectonic revolution and forming mechanism of gravitational décollement structures in the passive continental margin of West Africa.Geotectonica et Metallogenia(in Chinese),36(2):186-196.
Ji X L,Wang W Y,Qiu Z Y.2015.The research to the minimum curvature technique for potential field data separation.Chinese Journal of Geophysics(in Chinese),58(3):1042-1058,doi:10.6038/cjg20150329.
Kamgang P,Njonfang E,Nono A,et al.2010.Petrogenesis of a silicic magma system:Geochemical evidence from Bamenda Mountains,NW Cameroon,Cameroon Volcanic Line.Journal of African Earth Science,58(2):285-304.
Letouzey J,Colletta B,Vially R,et al.1995.Evolution of saltrelated structures in compressional settings.∥Jackson M P A,Roberts D G,Snelson S eds.Salt Tectonics:A Global Perspective.Oklahoma:AAPG,65:41-60.
Li L,Wu M N,Li D R.2005.Present hydrocarbon exploration situation and prospect of salt-bearing basin in gabon and its adjacent area.China Petroleum Exploration(in Chinese),10(3):57-63,68.
Li T,Hu W S,Hu F,et al.2012.Gravitational decollement structural development characteristics and its evolutionary history of Rio Muni Basin.Journal of Oil and Gas Technology(in Chinese),34(4):1-6.
Liu G D.1992.Geologic-Geophysic Features of China Seas and Adjacent Regions(in Chinese).Beijing:Science Press.
Liu G D,Hao T Y,Liu Y K.1996.The significance of gravity and magnetic research for knowing sedimentary basins.Progress in Geophysics(in Chinese),11(2):1-15.
Liu Z D,Li J H.2011.Control of salt structures on hydrocarbons in the passive continental margin of West Africa.Petroleum Exploration and Development(in Chinese),38(2):196-202.
Lu B L,Wang W Y,Du X D,et al.2015.Review of tectonicsedimentary features of the central-south section of West African continental margin basins.Advances in Marine Science(in Chinese),33(3):414-428.
Maus S,Barckhausen U,Benkenbosch H,et al.2009.EMAG2:A2-arc min resolution earth magnetic anomaly grid compiled from satellite,airborne,and marine magnetic measurements.Geochemistry,Geophysics,Geosystems,10(8):1-12.
Moulin M,Aslanian D,Olivet J L,et al.2005.Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data(Za6ango project).Geophysical Journal International,162(3):793-810.
Mounguengui M M,Guiraud M.2009.Neocomian to early Aptian syn-rift evolution of the normal to oblique-rifted North Gabon Margin(Interior and N′Komi Basins).Marine and Petroleum Geology,26(6):1000-1017.
Mounguengui M M,Lang J,Guiraud M.2008.Sedimentary dynamics and extensional structuring related to early Cretaceous rifting of Neocomian and Barremian deposits of the interior basin of Gabon.Journal of African Earth Sciences,51(5):239-256
Rao Y Q.2012.Petroleum geological features and exploration prospect of Gabon coastal Basin.Inner Mongulia Petrochemical Industry(in Chinese),(1):147-149.
Sandwell D T,Garcia E,Soofi K,et al.2013.Towards 1-mGal accuracy in global marine gravity from CrySat-2,Envisat,and Jasom-1.The Leading Edge,32(8):892-899.doi:10.1190/tle32080892.1.
Sandwell D T,Müller R D,Smith W H F,et al.2013.New global marine gravity model from CrySat-2and Jasom-1reveals buried tectonic structure.Science,346(6205):65-67.
Sandwell D T,Smith W H F.2009.Global marine gravity from retracked Geosat and ERS-1altimetry:Ridge Segmentation versus spreading rate.J.Geophys.Res.,114:B01411:1-Bo1411:18,.doi:10.1029/2008JB006008.
Teisserence P,Villemin J.1990.Sedimentary basin of Gabon-Geology and oil systems.∥Edwards J D,Santogrossi P A eds.Divergent/passive margin Basins.AAPG,48:117-199.
Turner J P,Rosendahl B R,Wilson P G.2003.Structure and evolution of an obliquely sheared continental margin:Rio Muni,West Africa.Tectonophysics,374(1-2):41-55.
Wang J.Analysis on sub-salt structural characteristics and exploration direction of block LT2000in Gabon.Journal of Oil and Gas Technology(in Chinese),2012,34(1):35-40.
Wang W Y,Pan Y,Qiu Z Y.2009.A new edge recognition technology based on the normalized vertical derivative of the total horizontal derivative for potential field data.Applied Geophysics,6(3):226-233.
Wang W Y,Pan Z S.1993.Fast solution of forward and inverse problems for gravity field in a dual interface model.Geophysical ProspectingforPetroleum(in Chinese),32(2):81-123.
Wang W Y,Qiu Z Y,Yang Y,et al.2010.Some advances in the edge recognition of the potential field.Progress in Geophysics(in Chinese),25(1):196-210,doi:10.3969/j.issn.1004-2903.2010.01.027.
Xiong L P,Liu Y L,Huo H.2010.Comparison of the hydrocarbon accumulation patterns of petroliferous basins between the north and south parts of the West African coast.Oil&Gas Geology(in Chinese),31(4):410-109.
Yang X J,Li J,Yu B S.2012.Structural feature and exploratory potential of the Lower Congo Basin.Progress in Geophysics(in Chinese),27(6):2585-2593,doi:10.6038/j.issn.1004-2903.2012.06.036.
Yang Y C,Zhang S L,Sun Y M,et al.2013.Source rock distribution and petroleum accumulation in Kwanga basin West Africa.Marine Geology Frontiers(in Chinese),29(3):29-36.
Zhang P Q,Zhao Q Y.1996.Methods of the magnetic direction transform of aeromagnetic anomalies with differential inclinations in low magnetic latitudes.Computing Techniques for Geophysical and Geochemical Exploration(in Chinese),18(3):206-214.
胡望水,李涛,于水等.2012.西非被动大陆边缘重力滑脱构造发育演化及成因机制.大地构造与成矿学,36(2):186-196.
纪晓琳,王万银,邱之云.2015.最小曲率位场分离方法研究.地球物理学报,58(3):1042-1058,doi:10.6038/cjg20150329.
李莉,吴慕宁,李大荣.2005.加蓬含盐盆地及邻区油气勘探现状和前景.中国石油勘探,10(3):57-63,68.
李涛,胡望水,胡芳等.2012.里奥穆尼盆地重力滑脱构造发育特征及演化规律.石油天然气学报,34(4):1-6.
刘光鼎.1992.中国海区及邻域地质地球物理特征.北京:科学出版社.
刘光鼎,郝天珧,刘伊克.1996.重磁研究对认识盆地的意义.地球物理学进展,11(2):1-15.
刘祚冬,李江海.2011.西非被动大陆边缘盆地盐构造对油气的控制作用.石油勘探与开发,38(2):196-202.
鲁宝亮,王万银,杜向东等.2015.西非陆缘盆地中南段构造与沉积研究.海洋科学进展,33(3):414-428.
饶轶群.2012.加蓬海岸盆地油气地质特征及勘探前景.内蒙古石油化工,(1):147-149.
王建.2012.加蓬LT2000区块盐下构造特征与勘探方向分析.石油天然气学报,34(1):35-40.
王万银,潘作枢.1993.双界面模型重力场快速正反演问题.石油物探,32(2):81-123.
王万银,邱之云,杨永等.2010.位场边缘识别方法研究进展.地球物理学进展,25(1):196-210,doi:10.3969/j.issn.1004-2903.2010.01.027.
熊利平,刘延莉,霍红.2010.西非海岸南、北两段主要含油气盆地油气成藏特征对比.石油与天然气地质,31(4):410-109.
杨晓娟,李军,于炳松.2012.下刚果盆地构造特征及油气勘探潜力.地球物理学进展,27(6):2585-2593,doi:10.6038/j.issn.1004-2903.2012.06.036.
杨永才,张树林,孙玉梅等.2013.等.西非宽扎盆地烃源岩分布及油气成藏.海洋地质前沿,29(3):29-36.
张培琴,赵群友.1996.低磁纬度区航磁异常变倾角磁方向转换方法.物探化探计算技术,18(3):206-214.