塔里木盆地西南地区和田古隆起改造过程及其地质意义

Transformation processes of Hetian paleo-uplift in southwestern Tarim Basin and its geological significance

  • 摘要: 塔里木盆地西南地区古生代经历了复杂的建造—改造过程,古隆起迭加改造过程认识的不清晰制约了区域内油气勘探的突破。为解决此问题,基于最新的地震、钻井资料,开展了地震解释、构造分析等一系列工作,分层、分期恢复区域内剥蚀量的变化过程,刻画了和田古隆起的形成、改造过程;基于盆缘岩浆岩年龄、形成环境分析,讨论了古隆起演化及改造的动力学机制;结合油气勘探情况,探讨了古隆起迭加改造的控油气作用。研究认为:(1)塔西南地区剥蚀中心发生过明显的迁移,加里东中期Ⅰ幕局限于盆地西南缘,加里东中期Ⅲ幕剥蚀区域向北扩展,海西早期剥蚀中心向东迁移,海西晚期,剥蚀中心位于盆地西北部,喜马拉雅期剥蚀中心位于现今巴楚隆起所在区域;(2)和田古隆起具有两阶段演化特征,加里东中期Ⅲ幕为陆缘隆起,海西早期为陆内隆起,和田古隆起主要遭受盆地西北缘麦西古隆起和盆地中部巴楚隆起的改造,调整了和田古隆起控制形成的早期古地貌;(3)古隆起的迁移演化及不同古隆起间的迭加改造,控制了不同储盖组合的分布,和田古隆起、麦西古隆起、巴楚古隆起间的构造枢纽带是油气聚集的有利部位,应成为下一步的勘探方向。

     

    Abstract: The southwestern Tarim Basin experienced a complex construction and transformation process during the Paleozoic era. The unclear understanding of the superimposed transformation processes of the paleo-uplifts has restricted its oil and gas exploration. To address this issue, a series of studies, including seismic interpretation and structural analysis, were carried out based on the latest seismic and drilling data. The variation process of denudation was restored in different layers and periods, and the formation and transformation processes of the Hetian paleo-uplift were characterized. Based on the analysis of the ages and formation environments of basin-margin igneous rocks, the dynamic mechanism of the evolution and transformation of the paleo-uplift was discussed. Combined with the oil and gas exploration results, the controlling effects of the superimposed transformation of the paleo-uplifts were discussed. The results indicated that: (1) The denudation center in the southwestern Tarim Basin has undergone significant migration. During stage Ⅰ of the middle Caledonian period, denudation was confined to the southwestern margin of the basin. By stage Ⅲ of the middle Caledonian period, the denudation area expanded northward. During the early Hercynian period, the denudation center migrated eastward. In the late Hercynian period, it was located in the northwestern part of the basin. During the Himalayan period, the denudation center was located in the area where the present Bachu Uplift is situated. (2) The Hetian paleo-uplift exhibited a two-stage evolutionary pattern. It was an uplift along continental margins during stage Ⅲ of the middle Caledonian period and then transformed into an intracontinental uplift during the early Hercynian period. The Hetian paleo-uplift was mainly affected by the transformation of the western Maigaiti paleo-uplift in the northwestern margin of the Tarim Basin and the Bachu Uplift in the central basin, which adjusted the early paleogeomorphology of the Hetian paleo-uplift. (3) The migration and evolution of the paleo-uplift and the superimposed transformation between different paleo-uplifts controlled the distribution of different reservoir and caprock assemblages. The structural hinge zones between the Hetian, the western Maigaiti, and the Bachu paleo-uplifts were identified as favorable areas for oil and gas accumulation and should be the focus of future exploration efforts.

     

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