河套盆地吉兰泰地区白垩系地层划分及地质特征

(1.西北大学 大陆动力学国家重点实验室,陕西 西安 710069; 2.中国石油长庆油田分公司 勘探开发研究院,陕西 西安 710018)

河套盆地; 吉兰泰; 地层划分

Division of Cretaceous strata and analysis of geological characteristicsin the Jilantai area of Hetao Basin
WANG Fei1,MA Zhan-rong2,PU Ren-hai1,ZHANG Cai-li2

(1.State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China; 2.Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi'an 710018,China)

Hetao Basin; Jilantai; division of strata

DOI: 10.13800/j.cnki.xakjdxxb.2019.0413

备注

作为河套盆地油气勘探的主要目的 层系,盆地白垩纪地层划分一直存在较大的争议。文中利用古生物、岩性及录井资料,确定吉兰泰地区白垩系只发育下白垩统。通过合成记录标定与不整合面建立了吉兰泰地区白垩系地层格架。固阳组固三段在部分剖面中表现为一厚度急剧增大的楔状体,根据钻遇其的ZK500井岩心、露头显示及正演模拟,楔状体主要为胶结松散的砂泥岩砾岩沉积物。根据形态及内部反射特征将其分为Ⅰ,Ⅱ2种类型,Ⅱ型楔状体之下的航磁异常体的隆升使研究区北部区域由固三段的断陷沉积向固二段的凹陷沉积转换。Ⅰ型楔状体未受航磁异常体隆升影响,受断层切割严重,其厚度应向山前控盆断层进一步增大。研究区南部地震剖面中固三段之下发育强振幅连续反射的侏罗系断陷沉积,根据地震剖面勾画出了其发育范围,并在西南边界一剖面中见到了可能的石炭系。

There have been disputes among scholars over the division of the Cretaceous strata,a mina target layer of oil and gas exploration in Hetao Basin.There was only formed early Cretaceous strata Guyang Formation based on the paleontology,lithology and logging data.The Cretaceous stratigraphic framework of the Jilantai area has been established through synthetic record and surface of unconformity.The third member of Guyang Formation is a wedge-shaped body with a sharp thickness increasing in some sections.According to drilling and outcrop display and forward modeling of ZK500 well,wedge bodies are mainly consolidated loose sand,mudstone and conglomerate sediments.With the characteristics of morphology and internal reflection in view,it can be divided into two types:type I and II.The uplift of the aeromagnetic anomaly beneath the wedge body is the main reason for the transformation from the rift to the sag.The I cuneiform is not affected by the uplift of the aeromagnetic anomaly body,and was seriously cut by the fault,and its thickness should be further increased to the fault of the Bayanwula mountain.In the southern section of the study area,the Jurassic fault depression with strong amplitude and continuous reflection is developed under the third members of Guyang Formation in the seismic sections.The development range is outlined according to the seismic profiles with a possible Carboniferous system found in the profile of the southwest boundary.