印度扇近海盆地古新统—始新统陆架镶边台地沉积相特征及控制因素

Facies and controls of the Paleocene-Eocene shelf deposition in rimmed platform in offshore Indus Basin

  • 摘要: 印度扇近海盆地古新统—始新统浅水陆架碳酸盐岩镶边台地因缺乏钻井资料且地震资料品质较差,其沉积相类型与演化规律研究相对薄弱,严重制约了该区的油气资源潜力评价。本文基于深水区Pak G2-1井的单井相分析,结合邻区印度河盆地苏伊气田的地质资料,并参考四川盆地等典型镶边台地地震相图版,对研究区浅水陆架最新采集的二维地震资料进行了系统标定与解译。结果表明:(1)在浅水陆架区内识别出4种典型地震反射样式,据此将沉积相划分为开阔台地、台地边缘和台前斜坡3个相带,可进一步细分为若干亚相;(2)镶边台地的演化可划分为3个阶段,受古地貌与相对海平面变化的共同控制,始新世末期进入衰退阶段但未完全消亡。(3)台缘生物礁相为优质储集层的有利相带。本研究结果可为印度扇近海盆地下一步油气勘探提供地质依据和参考。

     

    Abstract: Due to the lack of drilling data and poor quality of seismic data, research on the types and evolution of the Paleocene-Eocene shallow-water shelf carbonate facies in rimmed platforms in the Indus Fan Offshore Basin is relatively weak, which seriously restricts the evaluation on hydrocarbon resource potential in this area. Based on the single-well facies analysis of the deep-water Well Pak G2-1 and combined with the geological data of the Sui Gas Field in the adjacent Indus Basin with the reference to the seismic facies plates of typical rimmed platforms such as the Sichuan Basin, we systematically calibrated and interpreted the newly collected 2D seismic data in the shallow-water shelf of the study area. Results show that: (1) Four typical seismic reflection patterns were identified within the shallow-water shelf area, based on which the sedimentary facies were classified into three major zones: the open platform, platform margin, and foreslope; and each zone can be further subdivided into several subfacies. (2) The evolution of the rimmed platform can be divided into three stages, which was jointly controlled by paleogeomorphology and relative sea-level changes, and at last Eocene entered a declining phase without complete termination. (3) The platform-margin reef facies is a favorable zone of high-quality reservoirs. This study provided a geological basis and reference for further hydrocarbon exploration in the offshore Indus Basin.

     

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