柴达木盆地西北古近系新近系异常高压形成机制分析
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摘要
柴达木盆地西北(以下简称"柴西北区")古近系—新近系异常超压普遍存在。对超压的空间分布特征和形成机制的研究是评价该地区油气成藏条件与资源潜力的关键。依据柴西北区钻井实测压力数据及基于等效深度法计算的地层压力结果,对研究区异常高压的平面和剖面分布特征进行分析。在此基础上,结合柴西北区典型钻井泥岩声波时差曲线特征、不同时期沉积速率、各地层岩性特征、有机质生烃潜力及柴西北地区遭受的构造挤压作用,对研究区超压的形成机制进行分析,并对各控制要素在超压形成过程中的贡献进行定量评价。研究结果表明:柴西北区地层超压起始深度位于大约1 500m,主要发育在古始新统路乐河组—中新统上干柴沟组内,总体上异常高压随深度加深逐渐增大。研究区超压的形成是多种因素综合作用的结果,其中欠压实作用、有机质生烃和构造挤压作用是该区超压形成演化的重要原因。对控制超压形成的各要素定量评价结果显示:欠压实作用是柴西北区超压形成的最重要控制因素,其贡献率高达60%;构造挤压作用次之,其贡献率在20%～30%左右;有机质生烃演化作用对超压形成也有影响,但贡献率相对较小。此外对柴西北区咸湖环境下的盐度分布特征研究初步表明,地层孔隙流体盐度和咸水半咸水环境下沉积的含盐塑性地层对超压的形成和保存也有一定的影响。
Overpressure is considered prevalent in the northwestern Qaidam Basin.Understanding the spatial distribution and genetic mechanism of overpressure is key to the evaluation of hydrocarbon accumulation conditions and resource potential of the region.Here,we analyzed the plane and section distribution characteristics of the area's abnormal high pressure based on the measured pressure and pressure calculated by the equivalent depth method.Combining the time-difference curve of acoustic wave of mudstone,deposition rate,lithologic characteristics,hydrocarbon generation potential of organic matter and tectonic compression,we quantitatively evaluated the genetic mechanism of overpressure.The results showed that the initial depth of overpressure in the area was about 1500 m,developed mainly in the Lulehe to upper Ganchaigou Formations of the Miocene and with abnormally high pressure increasing with depth.In general,undercompaction,organic matter generation and tectonic compression were important factors for overpressure formation and evolution.The results showed that,in the northwestern Qiandam Basin,undercompaction was the most important controlling factor,with a contribution rate of up to 60%;the contribution from tectonic compression came in second at about 20%-30%;and the contribution from organic matter generation was the least.Moreover,the salinity characteristics of the northwestern Qaidam Basin indicated that the formation of the overpressure was also affected by both pore fluid salinity and the salt-bearing plastic layer deposited in the salt-brackish water environment.
Overpressure is considered prevalent in the northwestern Qaidam Basin.Understanding the spatial distribution and genetic mechanism of overpressure is key to the evaluation of hydrocarbon accumulation conditions and resource potential of the region.Here,we analyzed the plane and section distribution characteristics of the area's abnormal high pressure based on the measured pressure and pressure calculated by the equivalent depth method.Combining the time-difference curve of acoustic wave of mudstone,deposition rate,lithologic characteristics,hydrocarbon generation potential of organic matter and tectonic compression,we quantitatively evaluated the genetic mechanism of overpressure.The results showed that the initial depth of overpressure in the area was about 1500 m,developed mainly in the Lulehe to upper Ganchaigou Formations of the Miocene and with abnormally high pressure increasing with depth.In general,undercompaction,organic matter generation and tectonic compression were important factors for overpressure formation and evolution.The results showed that,in the northwestern Qiandam Basin,undercompaction was the most important controlling factor,with a contribution rate of up to 60%;the contribution from tectonic compression came in second at about 20%-30%;and the contribution from organic matter generation was the least.Moreover,the salinity characteristics of the northwestern Qaidam Basin indicated that the formation of the overpressure was also affected by both pore fluid salinity and the salt-bearing plastic layer deposited in the salt-brackish water environment.
引文
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[15]吴婵,阎存凤,李海兵,等.柴达木盆地西部新生代构造演化及其对青藏高原北部生长过程的制约[J].岩石学报,2013,29(6):2211-2222.
[16]付锁堂.柴达木盆地西部油气成藏主控因素与有利勘探方向[J].沉积学报,2010,28(2):373-379.
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[19]时贤,程远方,梅伟.基于测井资料的地层孔隙压力预测方法研究[J].石油天然气学报,2012,34(8):94-98,166.
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[21]BOWERS G L.Pore pressure estimation from velocity data:accounting for overpressure mechanisms besides undercompaction[J].International Journal of Rock Mechanics&Mining Science&Geomechanics Abstracts,1995,10(2):89-95.
[22]赵永军,李汉林,查明.柴达木盆地西部第三系地层压力预测[J].江汉石油学院学报,2001(4):8-10+6.
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[24]李鹤永,刘震,党玉琪,等.柴达木盆地西部地区地温地压系统演化及其与油气成藏的关系[J].地质科学,2006(4):564-577.
[25]杜栩,郑洪印,焦秀琼.异常压力与油气分布[J].地学前缘,1995,2(4):137-148.
[26]陈磊,姜振学,陈委涛,等.川西新场地区须五段泥页岩超压成因及其对含气性的影响[J].现代地质,2016,30(2):406-412.
[27]曹国强.柴达木盆地西部地区第三系沉积相研究[D].广州:中国科学院研究生院(广州地球化学研究所),2005.
[28]WEI A J.Characteristics,origin and quantitative evaluation of overpressure in strike-slip and compression-shear booster zone of Tan-Lu Fault:a case study in JZ27section of Liaodong Bay,Bohai Sea[J].Petroleum Geology&Experiment,2015,37(1):47-52.
[29]罗晓容.构造应力超压机制的定量分析[J].地球物理学报,2004(6):1086-1093.
[30]刘亮明.浅成岩体引发的流体超压与岩石破裂及其对成矿的制约[J].地学前缘,2011,18(5):78-89.
[31]王亚东,张涛,迟云平,等.柴达木盆地西部地区新生代演化特征与青藏高原隆升[J].地学前缘,2011,18(3):141-150.
[32]李军,王贵文,欧阳健.利用测井信息定量研究库车坳陷山前地区地应力[J].石油勘探与开发,2001(5):93-95+10-1.
[33]郭小文,何生,刘可禹,等.烃源岩生气增压定量评价模型及影响因素[J].地球科学:中国地质大学学报,2013,38(6):1263-1270.
[34]向才富,冯志强,吴河勇,等.松辽盆地异常压力系统及其形成原因探讨[J].地质学报,2006(11):1752-1759.
[35]LIN L M,JIN Q.Hydrocarbon generation history of major source rocks in the northern edge and western part of Qaidam basin[J].Oil&Gas Geology,2004,25(6):677-681.
[36]刘军,刘成林,孙平,等.柴达木盆地西部地区咸化湖盆天然气地球化学特征及成因类型判识指标:以古近系-新近系为例[J].地质通报,2016,35(增刊1):321-328.
[37]姜德义,任涛,陈结,等.含软弱夹层盐岩型盐力学特性试验研究[J].岩石力学与工程学报,2012,31(9):1797-1803.
[38]卓勤功,赵孟军,李勇,等.膏盐岩盖层封闭性动态演化特征与油气成藏:以库车前陆盆地冲断带为例[J].石油学报,2014,35(5):847-856.
[39]陈发亮,陈业全,魏生祥,等.东濮凹陷盐湖盆地油气富集规律研究[J].盐湖研究,2003(4):33-38.
[40]LIU C L,LI H H,ZHANG X,et al.Geochemical characteristics of the Paleogene and Neogene saline lacustrine source rocks in the western Qaidam Basin,Northwestern China[J].Energy&Fuels,2016,30(6).
[41]刘池洋,赵俊峰,马艳萍,等.富烃凹陷特征及其形成研究现状与问题[J].地学前缘,2014,21(1):75-88.
[42]金强,朱光有,王娟.咸化湖盆优质烃源岩的形成与分布[J].中国石油大学学报(自然科学版),2008(4):19-23.
[2]HUNT J M.Generation and migration of petroleum from abnormally pressured fluid compartments[J].AAPG Bulletin,1990,74:1(1):1-12.
[3]SWARBRICK R E,OSBORNE M J.Mechanisms that generate abnormal pressures:an overview[J].AAPG Memoir,1998,70:13-34.
[4]李小强,赵彦超.东濮凹陷柳屯洼陷盐湖盆地超压成因[J].石油与天然气地质,2012,33(5):686-694.
[5]王震亮,张立宽,施立志,等.塔里木盆地克拉2气田异常高压的成因分析及其定量评价[J].地质论评,2005(1):55-63.
[6]王存武.川东北地区碳酸盐岩层系超压发育演化与成因机制[D].武汉:中国地质大学(武汉),2008.
[7]叶志,樊洪海,蔡军,等.一种异常高压形成机制判别方法与应用[J].中国石油大学学报(自然科学版),2012,36(3):102-107.
[8]张凤奇,王震亮,钟红利,等.沉积盆地主要超压成因机制识别模式及贡献[J].天然气地球科学,2013,24(6):1151-1158.
[9]TINGAY M R P,SWARBRICK R E,MORLEY C K,et al.Origin of overpressure and pore-pressure prediction in the Baram province,Brunei[J].AAPG Bulletin,2009,93(1):51-74.
[10]AUDET D M.Mathematical modeling of gravitational compaction and clay dehydration in thick sediment layers[J].Geophysical International Journal,1995,122(1):283-298.
[11]李海,王鹏,许浩,等.柴达木盆地与莺歌海盆地超压体系、油气成藏特征对比分析[J].天然气地球科学,2012,23(4):736-741.
[12]华保钦,林锡祥.柴达木盆地异常地层压力及其成因探讨[J].沉积学报,1983(4):61-77.
[13]郭泽清,刘卫红,钟建华,等.柴达木盆地西部新生界异常高压:分布、成因及对油气运移的控制作用[J].地质科学,2005(3):376-389.
[14]范昌育,王震亮,王爱国,等.柴达木盆地北缘鄂博梁构造带超压形成机制与高压气、水层成因[J].石油学报,2015,36(6):699-706,714.
[15]吴婵,阎存凤,李海兵,等.柴达木盆地西部新生代构造演化及其对青藏高原北部生长过程的制约[J].岩石学报,2013,29(6):2211-2222.
[16]付锁堂.柴达木盆地西部油气成藏主控因素与有利勘探方向[J].沉积学报,2010,28(2):373-379.
[17]刘云田.柴西第三系构造沉积演化与油气成藏[D].广州:中国科学院研究生院(广州地球化学研究所),2003.
[18]李新宁,李留中,徐向阳,等.异常地层压力的形成原因及预测方法[J].吐哈油气,2006(2):120-126.
[19]时贤,程远方,梅伟.基于测井资料的地层孔隙压力预测方法研究[J].石油天然气学报,2012,34(8):94-98,166.
[20]EATON B A.The equation for geopressure prediction from well logs[J].SPE,1975,5544(5544):1-11.
[21]BOWERS G L.Pore pressure estimation from velocity data:accounting for overpressure mechanisms besides undercompaction[J].International Journal of Rock Mechanics&Mining Science&Geomechanics Abstracts,1995,10(2):89-95.
[22]赵永军,李汉林,查明.柴达木盆地西部第三系地层压力预测[J].江汉石油学院学报,2001(4):8-10+6.
[23]赵加凡,陈小宏,杜业波.柴达木第三纪湖盆沉积演化史[J].石油勘探与开发,2004(3):41-44.
[24]李鹤永,刘震,党玉琪,等.柴达木盆地西部地区地温地压系统演化及其与油气成藏的关系[J].地质科学,2006(4):564-577.
[25]杜栩,郑洪印,焦秀琼.异常压力与油气分布[J].地学前缘,1995,2(4):137-148.
[26]陈磊,姜振学,陈委涛,等.川西新场地区须五段泥页岩超压成因及其对含气性的影响[J].现代地质,2016,30(2):406-412.
[27]曹国强.柴达木盆地西部地区第三系沉积相研究[D].广州:中国科学院研究生院(广州地球化学研究所),2005.
[28]WEI A J.Characteristics,origin and quantitative evaluation of overpressure in strike-slip and compression-shear booster zone of Tan-Lu Fault:a case study in JZ27section of Liaodong Bay,Bohai Sea[J].Petroleum Geology&Experiment,2015,37(1):47-52.
[29]罗晓容.构造应力超压机制的定量分析[J].地球物理学报,2004(6):1086-1093.
[30]刘亮明.浅成岩体引发的流体超压与岩石破裂及其对成矿的制约[J].地学前缘,2011,18(5):78-89.
[31]王亚东,张涛,迟云平,等.柴达木盆地西部地区新生代演化特征与青藏高原隆升[J].地学前缘,2011,18(3):141-150.
[32]李军,王贵文,欧阳健.利用测井信息定量研究库车坳陷山前地区地应力[J].石油勘探与开发,2001(5):93-95+10-1.
[33]郭小文,何生,刘可禹,等.烃源岩生气增压定量评价模型及影响因素[J].地球科学:中国地质大学学报,2013,38(6):1263-1270.
[34]向才富,冯志强,吴河勇,等.松辽盆地异常压力系统及其形成原因探讨[J].地质学报,2006(11):1752-1759.
[35]LIN L M,JIN Q.Hydrocarbon generation history of major source rocks in the northern edge and western part of Qaidam basin[J].Oil&Gas Geology,2004,25(6):677-681.
[36]刘军,刘成林,孙平,等.柴达木盆地西部地区咸化湖盆天然气地球化学特征及成因类型判识指标:以古近系-新近系为例[J].地质通报,2016,35(增刊1):321-328.
[37]姜德义,任涛,陈结,等.含软弱夹层盐岩型盐力学特性试验研究[J].岩石力学与工程学报,2012,31(9):1797-1803.
[38]卓勤功,赵孟军,李勇,等.膏盐岩盖层封闭性动态演化特征与油气成藏:以库车前陆盆地冲断带为例[J].石油学报,2014,35(5):847-856.
[39]陈发亮,陈业全,魏生祥,等.东濮凹陷盐湖盆地油气富集规律研究[J].盐湖研究,2003(4):33-38.
[40]LIU C L,LI H H,ZHANG X,et al.Geochemical characteristics of the Paleogene and Neogene saline lacustrine source rocks in the western Qaidam Basin,Northwestern China[J].Energy&Fuels,2016,30(6).
[41]刘池洋,赵俊峰,马艳萍,等.富烃凹陷特征及其形成研究现状与问题[J].地学前缘,2014,21(1):75-88.
[42]金强,朱光有,王娟.咸化湖盆优质烃源岩的形成与分布[J].中国石油大学学报(自然科学版),2008(4):19-23.
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