塔中Ⅱ区奥陶系鹰山组岩溶古地貌恢复方法研究

Reconstruction of karst palaeogeomorphology for the Ordovician Yingshan formation in the central Tarim basin

塔中地区在构造上是塔里木盆地中央隆起的一部分,属于中央隆起带中段的塔中低凸起。良里塔格组沉积之前吐木休克组、一间房组、鹰山组地层遭受不同程度的剥蚀,精确雕刻鹰山组顶面古岩溶地貌,对岩溶储层地质建模及有利区块预测具有重要意义。论文对比了不同古地貌恢复方法:认为印模法可以很好地雕刻微地貌形态,但是区域构造趋势却与实际不符;残厚与残厚趋势面法构建了当时的古构造,但不能刻画微地貌形态。本次研究首次提出"残厚趋势面与印模残差组合法"古地貌恢复技术,该方法不仅解决了塔中地区古地貌恢复难题,且有利于计算机实现。研究认为塔中Ⅱ区奥陶系鹰山组古地貌形态可划分为三种二级地貌单元:岩溶台地、岩溶缓坡地和岩溶盆地,并给出了不同岩溶地貌单元的划分指标体系。

As part the central uplift of the Tarim basin, the Tazhong （central Tarim） Ⅱ area is a low swell of the middle section of this uplift belt. In this area, before sedimentation of the Lianglitage formation, the strata of the Tumuxiuke, Yijianfang and Yingshan formations had experienced erosion of different degrees, leading to destruction of the original landforms. To delineate the karst paleomorphology of the top Yingshan formation is of great importance for modeling of karst reservoirs and forecasting favorable blocks in exploration. This work compares methods for paleogeomorphology reconstruction. The impression method can well describe micro morphology, but its resulting regional tectonic trends do not accord with the real ones. While the residual thickness and residual thickness trend surface method is able to build the palaeostructure at that time, but cannot depict the micro morphology. To solve this problem, this study proposes a combination approach of ＂residual thickness of trend surface and impression residuals＂ to recover the ancient karst landform. This new method not only facilitates the paleogeomorphology restoration of the Tazhong area, but also helps computer modeling. The research suggests that the Ordovician Yingshan formation of the Tazhong Ⅱ area can be divided into three kinds of second-order geomorphic units, karst platform, karst basin, karst gentle slope, and gives the index system for subdivision of these landform units.