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下古生界是塔里木盆地内最有潜力找到大油气田的层位。通过盆地内48口钻至下古生界钻井的沉积层序与沉积相分析、9800km地震剖面的地震相分析、大量Sr、C同位素及微量元素分析,并结合相关资料,开展了寒武纪—奥陶纪的以世或期为单位的岩相古地理研究,定性探讨海平面变迁。在此基础上,运用沉积地球化学定量探讨海平面的波动。分析表明,早古生代塔里木地区经历了两次大规模的海侵与海退过程,寒武纪和奥陶纪各经历了一次。每个海侵与海退过程内各包含了两个较高频的海平面升降旋回,即早寒武世早期海侵—早寒武世中期至中寒武世晚期海退、中寒武世末期海侵—晚寒武世晚期海退、早奥陶世早期至中奥陶世中期海侵—中奥陶世晚期海退、晚奥陶世早期海侵—晚奥陶世中至晚期海退。在上述2次大规模的海侵与海退以及4个较高频的海平面升降旋回中,两次大的海侵分别发育于早寒武世早期以及晚奥陶世早中期,三次较大的海退出现于中寒武世晚期、晚寒武世末期、晚奥陶世早期。岩溶在地层格架中的发育支持了上述结论。
The Lower Paleozoic is the most potential layer in the Tarim Basin to find large oil and gas fields. Through the analysis of sedimentary sequence and sedimentary facies of 48 drilling to lower Paleozoic drilling in the basin, seismic phase analysis of 9800km seismic section, a large number of Sr, C isotopes and trace elements analysis, combined with relevant data, the Cambrian- Ordovician epoch or epicontinental lithofacies palaeogeography, qualitative analysis of sea level changes. Based on this, the sedimentary geochemistry is used to quantitatively study the sea level fluctuation. The analysis shows that the Early Paleozoic Tarim region experienced two large-scale transgressions and regressions, and the Cambrian and Ordovician experienced one each. Each of the transgression and regression processes contained two higher-frequency sea-level rise-and-fall cycles, namely, the Early Cambrian transgression-the Middle Cambrian-Middle Cambrian sea-level regression, the Middle Cambrian Late transgression: retrogressive late Late Cambrian, early Early Ordovician mid-Ordovician transcontinental - Late Middle Ordovician retreat, Early Late Ordovician transgression - Late Ordos receded into middle and late stages. In the above-mentioned two large-scale transgressions and regression and four higher-frequency sea-level cyclones, two large transgressions were developed in early Early Cambrian and early-middle Ordovician, respectively, three times larger The sea retreat occurred in the late Middle Cambrian, Late Cambrian, Late Ordovician early. The development of karst in the stratigraphic framework supports this conclusion.