古地磁在大庆徐家围子火山岩裂缝定向中的应用
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摘要
在油气田勘探开发中，钻井岩芯的定向对于油气勘探具有十分重要的意义。目前有多种岩芯定向方法，其中古地磁粘滞剩磁定向是一项经济有效的岩芯定向技术，具有良好的应用前景。
本文对大庆徐家围子下白垩统营城组火山岩9口钻井500余块岩芯样品进行了系统的岩石磁学和古地磁研究，并对钻井中的营城组火山岩进行了系统的裂缝统计和定向。
等温剩磁和阻挡温度谱等岩石磁学分析结果显示，徐深气田下白垩统营城组火山岩的主要载磁矿物是以磁铁矿为主，含少量赤铁矿的组合，少量样品可能含有磁黄铁矿或钛磁铁矿。其中流纹岩、英安岩类以磁铁矿为主，而凝灰岩类以赤铁矿为主。系统的热退磁分析表明，松辽盆地早白垩世深层火山岩具有特征剩磁和粘滞剩磁两组剩磁分量，载磁性矿物为磁铁矿。火山岩剩磁特征表明，火山岩分离出的粘滞剩磁分量与现今地球磁场方向一致。只要将岩芯粘滞剩磁分量校正至现今地磁场方向，即实现了岩芯在现今地下原始方位的恢复，继而实现岩芯裂缝的定向。
为验证获得的粘滞剩磁定向是否有效，从样品中挑选出部分系统退磁的样品结果，进行特征剩磁分离，特征剩磁的平均方向为D=35.2°，I=71.7°，α_(95)=12.1°，κ=22，从而进一步计算出古地磁极的位置Ψ=175.9°，λ=65.9°，dp=18.8，dm=21.4，古纬度为56.5°。经粘滞剩磁定向校正后获得的古地磁极与松辽地区已有的早白垩世古地磁极可以对比，证明了粘滞剩磁定向是有效的。
利用粘滞剩磁定向方法对研究区的火山岩岩芯裂缝进行了定向并制作了相应井的裂缝走向玫瑰花图，从统计学角度直观地反映裂缝发育的优势方向。不同的井获得的裂缝优势发育方向存在差异，但是综合起来看，火山岩主要发育有四组裂缝，分别为北东向(35°～50°)、北西向(310°～320°)、近南北向和近东西向，其中北东向和北西向的裂缝更占优势。宋西断层在兴城—升平地区的走向为NNW(330°)方向，为左旋走滑断裂，而其它方向的裂缝是在宋西断层的发育下的派生裂缝方向。
In the exploration of gas and oil fields, the orientation of the drilling core is of great importance. Paleomagnetism is a very effective and economic way for core orientation developed recent years and has good prospects in its application.
In this article, we collected about 500 core samples from Lower Cretaceous Yingchen Formation over 9 drilling wells in Xujiaweizi, Daqing. Cracks on the cores were measured systematically. Representive samples were measured for rock magnetic properties and systematic thermal cleaning were carried out on all the samples.
Rock magnetic analysis such as isothermal remnant magnetization and block temperature spectrum shows that the dominantly magnetic carrier is magnetite combined with some hematite, occasionally with pyrrhotite or titanomagnetite in the Lower Cretaceous Yingchen Formation. Among these lava, rhyolite and dacite are mainly magnetite, while tuffaceous rocks are mainly hematite. Systematic thermal demagnetization analysis shows two remnant magnetism components which are characteristic remnant magnetization and viscous remnant magnetization. Remnant magnetic feature of lava shows that the viscous remnant magnetism component cleaning at below 350°C from the lava is consistency with the present direction of the Earth's magnetic field. We can recover the original underground position of the core by correct the viscous remnant magnetization component of the core to the current earth's magnetic field direction. And then we can obtain the orientation of the core cracks.
In order to test the effectiveness of the viscous remnant magnetization, we isolated characteristic remnant magnetization (ChRM) from some selected samples. The average direction of the characteristic remnant magnetization is D=35.2°,I=71.7°,α95=12.1°, k = 22; and from this we can calculate that the position of the paleomagnetic pole isψ= 175.9°,λ=65.9°,dp=18.8,dm=21.4, palaeolatitude is 56.5°. This result is parallel to the already exist paleomagnetic pole of the Early Cretaceous of the Songliao region and thus pass the ChRM test which shows the re-orientation effectiveness by viscous remnant magnetization. We then use the viscous remnant magnetization to re-oriente cracks direction of the lava core in the study area, and make the rose-diagram of crack strikes of the corresponding well which can directly reflects the preferential direction of the crack in the statistical point of view. There are differences among the preferential developed directions of different wells, however, there are mainly four preferential developed directions of cracks in the lava. They are northeast (35°-50°), northwest(310°-320°) , nearly N-S and nearly E-W, among which the northeast and the northwest are more dominant. The direction of Songxi Fault in Xingcheng-Shengping district is NNW (330°) , which is a sinistral slip strike fault,and others are driviative faults drove by Songxi fault.
本文对大庆徐家围子下白垩统营城组火山岩9口钻井500余块岩芯样品进行了系统的岩石磁学和古地磁研究，并对钻井中的营城组火山岩进行了系统的裂缝统计和定向。
等温剩磁和阻挡温度谱等岩石磁学分析结果显示，徐深气田下白垩统营城组火山岩的主要载磁矿物是以磁铁矿为主，含少量赤铁矿的组合，少量样品可能含有磁黄铁矿或钛磁铁矿。其中流纹岩、英安岩类以磁铁矿为主，而凝灰岩类以赤铁矿为主。系统的热退磁分析表明，松辽盆地早白垩世深层火山岩具有特征剩磁和粘滞剩磁两组剩磁分量，载磁性矿物为磁铁矿。火山岩剩磁特征表明，火山岩分离出的粘滞剩磁分量与现今地球磁场方向一致。只要将岩芯粘滞剩磁分量校正至现今地磁场方向，即实现了岩芯在现今地下原始方位的恢复，继而实现岩芯裂缝的定向。
为验证获得的粘滞剩磁定向是否有效，从样品中挑选出部分系统退磁的样品结果，进行特征剩磁分离，特征剩磁的平均方向为D=35.2°，I=71.7°，α_(95)=12.1°，κ=22，从而进一步计算出古地磁极的位置Ψ=175.9°，λ=65.9°，dp=18.8，dm=21.4，古纬度为56.5°。经粘滞剩磁定向校正后获得的古地磁极与松辽地区已有的早白垩世古地磁极可以对比，证明了粘滞剩磁定向是有效的。
利用粘滞剩磁定向方法对研究区的火山岩岩芯裂缝进行了定向并制作了相应井的裂缝走向玫瑰花图，从统计学角度直观地反映裂缝发育的优势方向。不同的井获得的裂缝优势发育方向存在差异，但是综合起来看，火山岩主要发育有四组裂缝，分别为北东向(35°～50°)、北西向(310°～320°)、近南北向和近东西向，其中北东向和北西向的裂缝更占优势。宋西断层在兴城—升平地区的走向为NNW(330°)方向，为左旋走滑断裂，而其它方向的裂缝是在宋西断层的发育下的派生裂缝方向。
In the exploration of gas and oil fields, the orientation of the drilling core is of great importance. Paleomagnetism is a very effective and economic way for core orientation developed recent years and has good prospects in its application.
In this article, we collected about 500 core samples from Lower Cretaceous Yingchen Formation over 9 drilling wells in Xujiaweizi, Daqing. Cracks on the cores were measured systematically. Representive samples were measured for rock magnetic properties and systematic thermal cleaning were carried out on all the samples.
Rock magnetic analysis such as isothermal remnant magnetization and block temperature spectrum shows that the dominantly magnetic carrier is magnetite combined with some hematite, occasionally with pyrrhotite or titanomagnetite in the Lower Cretaceous Yingchen Formation. Among these lava, rhyolite and dacite are mainly magnetite, while tuffaceous rocks are mainly hematite. Systematic thermal demagnetization analysis shows two remnant magnetism components which are characteristic remnant magnetization and viscous remnant magnetization. Remnant magnetic feature of lava shows that the viscous remnant magnetism component cleaning at below 350°C from the lava is consistency with the present direction of the Earth's magnetic field. We can recover the original underground position of the core by correct the viscous remnant magnetization component of the core to the current earth's magnetic field direction. And then we can obtain the orientation of the core cracks.
In order to test the effectiveness of the viscous remnant magnetization, we isolated characteristic remnant magnetization (ChRM) from some selected samples. The average direction of the characteristic remnant magnetization is D=35.2°,I=71.7°,α95=12.1°, k = 22; and from this we can calculate that the position of the paleomagnetic pole isψ= 175.9°,λ=65.9°,dp=18.8,dm=21.4, palaeolatitude is 56.5°. This result is parallel to the already exist paleomagnetic pole of the Early Cretaceous of the Songliao region and thus pass the ChRM test which shows the re-orientation effectiveness by viscous remnant magnetization. We then use the viscous remnant magnetization to re-oriente cracks direction of the lava core in the study area, and make the rose-diagram of crack strikes of the corresponding well which can directly reflects the preferential direction of the crack in the statistical point of view. There are differences among the preferential developed directions of different wells, however, there are mainly four preferential developed directions of cracks in the lava. They are northeast (35°-50°), northwest(310°-320°) , nearly N-S and nearly E-W, among which the northeast and the northwest are more dominant. The direction of Songxi Fault in Xingcheng-Shengping district is NNW (330°) , which is a sinistral slip strike fault,and others are driviative faults drove by Songxi fault.
引文
董平川．利用岩芯古地磁定向研究油藏水平主应力方向．岩石力学和工程学报，2004，23(14)：2480—2483．
方大钧，沈忠悦，谈晓冬等．塔里木盆地显生宙古地磁与板块运动学．浙江大学出版社，2006，p236．
侯守信，田国荣．古地磁岩心定向及其在地应力测量上的应用．地质力学学报，1999，5(1)：90—96．
靳坤．徐家围子断陷盆地中部火山岩段裂缝特征定量描述与评价．浙江大学工程硕士学位论文，2005．
李学森，熊国锦．钻井岩心重定向的古地磁方法及其可靠性．石油勘探与开发，2006，33(5)：581—585．
刘为付．松辽盆地徐家围子断陷深层火山岩储层特征及有利区预测．石油与天然气地质，2004，25(1)：115—119．
孟小红，周海民．冀东油田钻井岩芯的磁学研究．地球物理学报．1997，40(6)：809—820．
苏培东，秦启荣，黄润秋．储层裂缝预测研究现状与展望．西南石油学院学报．2005，27(5)：14—17．
唐湘蓉，李品．构造应力场有限元数值模拟在裂缝预测中的运用．特种油气藏，2005，12(2)：25—28．
田莉丽，邓成龙．岩石的磁学性质．地球物理学进展，2001，16(2)：109—117．
童亨茂，钱样麟．储层裂缝研究分析方法[J]．石油大学学报．1994，18(6)：14—20．
童亨茂．储层裂缝描述与预测研究进展．新疆石油学院学报．2004，16(2)：9—13．
王瑞平．基岩潜山油气藏储集空间分布规律和评价方法．北京：地质出版社，2003．
王秀娟，孙贻铃，迟博等．松辽盆地三肇地区油田储层裂缝及地应力特征．高校地质学报，1999，5(3)：328—333．
杨斌谊，龚建军，陈建军．确定油田钻井岩心原始方位的古地磁学方法探讨．西北地质，2003，36(4)：79—83．
杨斌谊，吴汉宁，李学森等．南泥湾油田钻井岩芯古地磁初步研究．石油天然气地质，2002，23(4)：297—401．
杨辉，张研，邹才能等．松辽盆地北部徐家围子断陷火山岩分布及天然气富集规律．地球物理学报，2006，49(4)：1136—1143．
杨振宇，Moreau M G．Montcomet．钻孔岩芯的古地磁研究．地球物理学报，1998，41(5)：652—657．
岳乐平，王建其，邸世祥等．油气田钻井岩芯及岩芯裂缝方位确定的古地磁原理与方法．地球物理学进展，1997，12(3)：71—76．
张盛宗，王为民，陈权．低渗透油藏开发与裂缝孔隙度．大庆石油地质与开发，1999，18(2)：23—27．
张永贵，陈明强，吴莹．利用动态资料研究巴喀油田裂缝分布．石油勘探与开发，1998，25(9)：68—71．
周新桂，操成杰，袁嘉音．储层构造裂缝定量预测与油气渗流规律研究现状和进展．地球科学进展．2003，18(3)：398—404．
朱岗崑．古地磁学概论：基础、原理、方法、成果与应用[M]．北京：科学出版社，2005：1—256．
朱日样，黄宝春，潘永信等．岩石磁学与古地磁实验室简介．地球物理学进展，2003，18(2)：177—181．
Besse J and Courtillot V. Apparent and true polar wander and geometry of the geomagnetic field over the last 200 Myr. Journal of Geophysics Reviews, 2002, 107(B11), 2300, doi: 10. 1029/2000JB000050.
Dong P C. Orientation determination of maximum horizontal stress in reservoir formation by paleomagnetic orientation of cores. Chinese Journal of Rock Mechanics and Engineering(in Chinese), 2004, 23(14): 2480—2483.
Enkin R J. The direction correction test for paleomagnetism. In His PhD Thesis, University de Paris 7, Paris, 1990.
Jin K. Quantitative description and elevation of fracture in volcanic reservoir, middle of Xujiaweizi fault-depression basin. Dissertation for the Engineering Master degree of Zhejiang University, 2005.
Li X S and Xiong G J. Paleomagnetic method of reorienting cores and its reliability. Petroleum Exploration and Development, 2006, 33(5): 581—585.
Liu W F. Reservoir characteristics of deep volcanic rocks and prediction of favorable areas in Xujiaweizi fault depression in Songliao basin. Oil & Gas Geology(in Chinese), 2004, 25(1): 115—119.
Meng X H and Zhou H M. Magnetic study of drill-cores in Jidong oil fled. Acta Geophysica Sinica(in Chinese ), 1997, 40(6): 809—820.
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方大钧，沈忠悦，谈晓冬等．塔里木盆地显生宙古地磁与板块运动学．浙江大学出版社，2006，p236．
侯守信，田国荣．古地磁岩心定向及其在地应力测量上的应用．地质力学学报，1999，5(1)：90—96．
靳坤．徐家围子断陷盆地中部火山岩段裂缝特征定量描述与评价．浙江大学工程硕士学位论文，2005．
李学森，熊国锦．钻井岩心重定向的古地磁方法及其可靠性．石油勘探与开发，2006，33(5)：581—585．
刘为付．松辽盆地徐家围子断陷深层火山岩储层特征及有利区预测．石油与天然气地质，2004，25(1)：115—119．
孟小红，周海民．冀东油田钻井岩芯的磁学研究．地球物理学报．1997，40(6)：809—820．
苏培东，秦启荣，黄润秋．储层裂缝预测研究现状与展望．西南石油学院学报．2005，27(5)：14—17．
唐湘蓉，李品．构造应力场有限元数值模拟在裂缝预测中的运用．特种油气藏，2005，12(2)：25—28．
田莉丽，邓成龙．岩石的磁学性质．地球物理学进展，2001，16(2)：109—117．
童亨茂，钱样麟．储层裂缝研究分析方法[J]．石油大学学报．1994，18(6)：14—20．
童亨茂．储层裂缝描述与预测研究进展．新疆石油学院学报．2004，16(2)：9—13．
王瑞平．基岩潜山油气藏储集空间分布规律和评价方法．北京：地质出版社，2003．
王秀娟，孙贻铃，迟博等．松辽盆地三肇地区油田储层裂缝及地应力特征．高校地质学报，1999，5(3)：328—333．
杨斌谊，龚建军，陈建军．确定油田钻井岩心原始方位的古地磁学方法探讨．西北地质，2003，36(4)：79—83．
杨斌谊，吴汉宁，李学森等．南泥湾油田钻井岩芯古地磁初步研究．石油天然气地质，2002，23(4)：297—401．
杨辉，张研，邹才能等．松辽盆地北部徐家围子断陷火山岩分布及天然气富集规律．地球物理学报，2006，49(4)：1136—1143．
杨振宇，Moreau M G．Montcomet．钻孔岩芯的古地磁研究．地球物理学报，1998，41(5)：652—657．
岳乐平，王建其，邸世祥等．油气田钻井岩芯及岩芯裂缝方位确定的古地磁原理与方法．地球物理学进展，1997，12(3)：71—76．
张盛宗，王为民，陈权．低渗透油藏开发与裂缝孔隙度．大庆石油地质与开发，1999，18(2)：23—27．
张永贵，陈明强，吴莹．利用动态资料研究巴喀油田裂缝分布．石油勘探与开发，1998，25(9)：68—71．
周新桂，操成杰，袁嘉音．储层构造裂缝定量预测与油气渗流规律研究现状和进展．地球科学进展．2003，18(3)：398—404．
朱岗崑．古地磁学概论：基础、原理、方法、成果与应用[M]．北京：科学出版社，2005：1—256．
朱日样，黄宝春，潘永信等．岩石磁学与古地磁实验室简介．地球物理学进展，2003，18(2)：177—181．
Besse J and Courtillot V. Apparent and true polar wander and geometry of the geomagnetic field over the last 200 Myr. Journal of Geophysics Reviews, 2002, 107(B11), 2300, doi: 10. 1029/2000JB000050.
Dong P C. Orientation determination of maximum horizontal stress in reservoir formation by paleomagnetic orientation of cores. Chinese Journal of Rock Mechanics and Engineering(in Chinese), 2004, 23(14): 2480—2483.
Enkin R J. The direction correction test for paleomagnetism. In His PhD Thesis, University de Paris 7, Paris, 1990.
Jin K. Quantitative description and elevation of fracture in volcanic reservoir, middle of Xujiaweizi fault-depression basin. Dissertation for the Engineering Master degree of Zhejiang University, 2005.
Li X S and Xiong G J. Paleomagnetic method of reorienting cores and its reliability. Petroleum Exploration and Development, 2006, 33(5): 581—585.
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