塔河油田海西运动早期奥陶系岩溶地貌

依据大量地质和地球物理资料,从构造形变的角度出发,采用井震结合、层面追踪及三维建模的方法,对塔河油田海西运动早期岩溶地貌的形成过程进行研究。结果发现,塔河油田古生界可分为2个形变构造层,一个是寒武系—奥陶系形变构造层,呈平缓背斜构造;另一个为石炭系—二叠系形变构造层,呈褶皱链式构造披覆于奥陶系之上。印模法不适用于塔河油田岩溶地貌的恢复,基于现今奥陶系顶面构造形态,建立构造等效圆弧曲线方程,依据不同构造阶段挤压形变压缩率,采用等弧长积分法,有效去除了岩溶期后的构造形变量,恢复了岩溶期地貌形态。海西运动早期,塔河油田奥陶系岩溶地貌北高南低,西倾东翘,其构造幅度为现今构造幅度的70%,具继承性演化特征,2个高耸带状峰丘高地与其间低缓箕状河丘谷地以及南部平坦开阔岩溶湖,共同构成了一个完整、独立的岩溶系统。

Ordovician Karst Paleogeomorphology During Early Hercynian Movement in Tahe Oilfield

Using a large amount of geological and geophysical data, the genetic process of the Ordovician karst paleogeomorphology during the Early Hercynian movement in the Tahe oilfield was investigated from the point of tectonic deformation by means of logging-seismic combination, stratigraphic interpretation and 3D modeling. The results show that there are two Paleozoic intervals with distinct deformation. The upper is a Cambrian-Ordovician carbonate formation showing as a gentle anticline, and the lower is a Carboniferous-Permian clastic formation showing as a fold chain overlying the Ordovician. The “impression method” isn’t suitable for the restoration of the paleokarst landform in the study area. Instead, we built a structural equivalent arc curve equation based on the present Ordovician top structural geomorphology, and used the equal arc length integral method to effectively remove the structural deformation after the karst period and restored the paleogeomorphology according to the compression ratio of different structural stages. The karst paleogeomorphology during the Early Hercynian movement was high in the north and low in the south, plunging to the west and rising to the east. The structure relief was 70% of the present one, showing a successive development feature. The complete and independent karst system is composed of two high and steep banded hoodoos-uplands, a lower karst depressions with a dustpan shape and a flat and open karst lake in the south of study area.