利用物探资料对西安凹陷和固市凹陷基底结构特征的研究
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摘要
为了探测渭河新生代盆地的基底组成和结构构造,调查渭河盆地主要地层厚度、埋深和构造特征,在渭河盆地开展二维地震勘探测量,在全面收集渭河盆地以往物探和钻孔资料的基础上,通过实测地震剖面,划分渭河盆地新生界地层,得到固市凹陷基底深约8 100km,西安凹陷基底深约6 600km,固市凹陷明显比西安凹陷基底深,这是本次工作最大的成果之一。再结合收集的重力数据,经过消除莫霍面影响后,分析渭河盆地西安凹陷和固市凹陷整体重力场变化特征,结果表明造成西安凹陷重力低,但基底浅;固市凹陷重力高,但基底深。这种实际地质情况是由于西安凹陷新近系沉积地层比固市凹陷沉积地层厚且深,而古近系地层却较之薄而浅,这种"跷跷板"式的地层分布特征能够引起重力异常"非常规"现象出现。通过此次工作实践,对渭河新生代盆地的基底组成和结构构造有清楚认识,对评价重点勘查区的成藏条件,为渭河盆地氦气资源远景调查提供借鉴。
In order to investigate the basal composition and structural structure of the Weihe Cenozoic basins,the main strata thickness,depth and tectonic characteristics of the Weihe basin,the 2 Dseismic survey was carried out in the Weihe basin.And the past geophysical and borehole data of the Weihe Basin was collected.According to the measured seismic section,the cenozoic strata of Weihe basin are divided.The base of Gushi and Xi'an depressions is about 8 100 km 6 600 km deep,respectively.This suggests that the Gushi depression is deeper than that of Xi'an depression,which is inconsistent with previous understanding.This is one of the greatest achievements.Combined with the collected gravity data and elimination the influence of Moho have been used to analyze the gravity field variation in Weihe basin.The results show that the gravity is low in the Xi'an depression,but the base is shallow.The gravity of the Gushi depression is high,but the basement is deep.This practical geological condition is due to the thick and deep sedimentary strata of the Neogene sedimentary strata in the Xi'an depression,which is thicker and shallow than the sedimentary strata in the Gushi depression.And so the characteristics of the distribution of the "seesaw" type can cause gravity "unconventional" phenomenon.Through the practice of this work,the basal composition and structure of the Weihe cenozoic basins have a clear understanding,and evaluation of reservoir formation conditions in the key exploration areas,and provide the geophysical basis for the helium resource prospecting survey in the Weihe basin.
In order to investigate the basal composition and structural structure of the Weihe Cenozoic basins,the main strata thickness,depth and tectonic characteristics of the Weihe basin,the 2 Dseismic survey was carried out in the Weihe basin.And the past geophysical and borehole data of the Weihe Basin was collected.According to the measured seismic section,the cenozoic strata of Weihe basin are divided.The base of Gushi and Xi'an depressions is about 8 100 km 6 600 km deep,respectively.This suggests that the Gushi depression is deeper than that of Xi'an depression,which is inconsistent with previous understanding.This is one of the greatest achievements.Combined with the collected gravity data and elimination the influence of Moho have been used to analyze the gravity field variation in Weihe basin.The results show that the gravity is low in the Xi'an depression,but the base is shallow.The gravity of the Gushi depression is high,but the basement is deep.This practical geological condition is due to the thick and deep sedimentary strata of the Neogene sedimentary strata in the Xi'an depression,which is thicker and shallow than the sedimentary strata in the Gushi depression.And so the characteristics of the distribution of the "seesaw" type can cause gravity "unconventional" phenomenon.Through the practice of this work,the basal composition and structure of the Weihe cenozoic basins have a clear understanding,and evaluation of reservoir formation conditions in the key exploration areas,and provide the geophysical basis for the helium resource prospecting survey in the Weihe basin.
引文
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[9]冯希杰,李晓妮.渭河断裂深、中、浅和近地表显示[J].地震地质,2008,30(1):264-271.FENG X J,LI X N.Manifestations of weihe fault at deep,middle,shallow and near-surface depth[J].Seismology And Geology,2008,30(1):264-271.(In Chinese)
[10]冯希杰,戴王强.渭河盆地断层活动横向迁移[J].地震学报,2004,26(2):174-182.FENG X J,DAI W Q.Lateral migration of fault activity in Weihe basin[J].Journal of Seismology,2004,26(2):174-182.(In Chinese)
[11]朱广生,桂志先,熊新斌,等.密度与纵横波速度关系[J].地球物理学报,1995,38:260-264.ZHU G S,GUI Z X,XIONG X B,et al.Relationships between density and P-wave,S-wave velocities[J].Journal of Geophysics,1995,38:260-264.(In Chinese)
[12]王卫东,张永志,王平,等.渭河断陷盆地及邻区的地震活动性和深部地球物理背景[J].内陆地震,2004,18(3):207-211.WANG W D,ZHANG Y Z,WANG P,et al.Seismicity and deep geophysical background in weihe down-faulted basin and its adjacent areas[J].Inland Earthquake,2004,18(3):207-211.(In Chinese)
[13]胡斌,祝意青,田勤俭,等.关中地区重力场及其时空动态演化特征[J].中国地震,2006,22(2):172-181.HU B,ZHU Y Q,TIAN Q J,et al.Study on gravity field and its dynamic evolutional characteristics in the guanzhong area[J].Earthquake Research in China,2006,22(2):172-181.(In Chinese)
[2]胡孟春.渭河盆地的地质构造与构造地貌类型[J].地理研究,1989,8(4):56-64.HU M C.The relationship between the tectonic landforms and structures in the Weihe river basin[J].Geographical Research,1989,8(4):56-64.(In Chinese)
[3]李玉宏,卢进才,李金超,等.渭河盆地富氦天然气井分布特征与氦气成因[J].吉林大学学报(地球科学版),2011,41(1):618-631.LI Y H,LU J C,LI J C,et al.The research of deep structural features of Weihe basin and adjacent areas[J].Chinese Journal Geophysics,2011,41(1):618-631.(In Chinese)
[4]张勤,瞿伟,彭建兵,等.渭河盆地地裂缝群发机理及东、西部地裂缝分布不均衡构造成因研究[J].地球物理学报,2012,55(8):2589-2597.ZHANG Q,QU W,PENG J B,et al.Research on tectonic causes of numerous ground fissures development mechanism and its unbalance distribution between eastern and western of Weihe basin[J].Journal of Geophysics,2012,55(8):2589-2597.(In Chinese)
[5]彭建兵,邓亚虹.汾渭盆地地裂缝成因与构造活动研究工作项目报告[R].西安:长安大学,2009.PENG J B,DENG Y H.Ground fissures causes and tectonic active+ity in Fenwei basin.research project roport[R].Xi’an:Chang’an University Shaanxi,2009.(In Chinese)
[6]韩芳林,张拴厚.陕西省区域地质志[M].西安:陕西省地质调查中心,2012.HAN F L,ZHANG S H.Regional geology shaanxi province[M].Xi’an:Shaanxi Center of Geological Survey,2012.(In Chinese)
[7]韩恒锐,张逸,袁志祥.渭河断陷盆地带的形成演化及断块运动[J].地震研究,2002,25(4):362-368.HAN H R,ZHANG Y,YUAN Z X.The evolution of Weihe basin and movement of the fault blocks[J].Journal of Seismological Research,2002,25(4):362-368.(In Chinese)
[8]冯希杰,田勤俭,申旭辉.渭河断裂西段活动差异性分析[J].地质论评,2003,49(3):233-238.FENG X J,TIAN Q J,SHEN X H.Analysis of activity difference of the west section of the Weihe fault[J].Geological Review,2003,49(3):233-238.(In Chinese)
[9]冯希杰,李晓妮.渭河断裂深、中、浅和近地表显示[J].地震地质,2008,30(1):264-271.FENG X J,LI X N.Manifestations of weihe fault at deep,middle,shallow and near-surface depth[J].Seismology And Geology,2008,30(1):264-271.(In Chinese)
[10]冯希杰,戴王强.渭河盆地断层活动横向迁移[J].地震学报,2004,26(2):174-182.FENG X J,DAI W Q.Lateral migration of fault activity in Weihe basin[J].Journal of Seismology,2004,26(2):174-182.(In Chinese)
[11]朱广生,桂志先,熊新斌,等.密度与纵横波速度关系[J].地球物理学报,1995,38:260-264.ZHU G S,GUI Z X,XIONG X B,et al.Relationships between density and P-wave,S-wave velocities[J].Journal of Geophysics,1995,38:260-264.(In Chinese)
[12]王卫东,张永志,王平,等.渭河断陷盆地及邻区的地震活动性和深部地球物理背景[J].内陆地震,2004,18(3):207-211.WANG W D,ZHANG Y Z,WANG P,et al.Seismicity and deep geophysical background in weihe down-faulted basin and its adjacent areas[J].Inland Earthquake,2004,18(3):207-211.(In Chinese)
[13]胡斌,祝意青,田勤俭,等.关中地区重力场及其时空动态演化特征[J].中国地震,2006,22(2):172-181.HU B,ZHU Y Q,TIAN Q J,et al.Study on gravity field and its dynamic evolutional characteristics in the guanzhong area[J].Earthquake Research in China,2006,22(2):172-181.(In Chinese)