摘要
镇北地区延长组是油气挖潜的主要目的层,其砂体类型和分布受古地貌控制。以精细等时地层格架为基础的古地貌恢复可以为砂体的成因和分布提供依据。结合岩心、测井和地震资料,以高分辨率层序地层学为指导建立研究区精细地层格架,将长7划分为1个中期旋回和5个短期旋回;以短期基准面旋回为单元,采用优化后的回剥法定量恢复研究区古地貌。结果表明:镇北地区主要发育坡折带,长73时期湖侵范围最大,坡折带较陡,东部深湖区发育浊积扇砂体;长73至长71时期,基准面下降,坡折带和沿湖岸线分布的河口坝砂体逐渐向湖区推进,坡折带逐渐变宽缓,其下的滑塌岩较发育;长71末期,基准面上升,坡折带和砂体逐渐向陆退缩。基准面旋回的变化导致沉积地貌发生改变,坡折带随之发生迁移,砂体成因和分布规律发生了明显变化。该研究对寻找有利油气目标区具有借鉴作用。
Chang 7 member of Yanchang Formation in Zhenbei area is one of the main targets of oil and gas exploration. The type and distribution of sand body are controlled by palaeogeomorphology. The recontructed palaeogeomorphology based on precise isochronous stratigraphic framework can provide basis for analyzing the genesis type and distribution of the sand body. Based on core, logging and sesmic data, this paper established fine stratigraphic framwork under the guadence of high resolution sequence stratigraphy, and divided Chang 7 reservoir into one middle-term base-level cycle and five short-term base-level cycles. An optimized backstripping method was used to restore the deposited terrain, and the palaeogeomorpholo~ map of the study area was drawn by short-term base level unit. The result shows that there mainly developed slope break in Zhenbei area, Chang 7~ is the maximum transgression, and turbidite fans appear in the deep lake in the northeastern part of the study area. From Chang 73 to Chang 71 stage, the base level decreases, the mouth bar and the slope break zone gradually advance to the lake, the angle of the break zone begins to decrease, and fluxoturbidite forms consequently; from late Chang 71 stage, the base level begins to rise, the slope break and the sandbody gradually retreat to the shore. Base level cycle change leads to geomorphic change, the origin and distribution of the sand bodies changes regularly, and it has an important significance in searehing for oil and gas.
出处
《岩性油气藏》
CSCD
2013年第5期65-69,共5页
Lithologic Reservoirs
基金
长庆油田科技项目"镇北地区长6-长8层序地层与砂体展布规律研究"(编号:2012-03)资助
关键词
古地貌
坡折带
砂体分布
鄂尔多斯盆地
palaeogeomorphology
slope break zone
sand body distribution
Ordos Basin
