波动分析约束下的原型盆地剥蚀量恢复——以惠民凹陷为例

Calculation of the Denuded Amount of the Cenozoic Prototype Basin under the Restriction of the Wave Analysis Method: An Example of Huimin Depression

为准确的恢复原型盆地剥蚀量,提出在波动分析法约束下,恢复原型盆地剥蚀量的新思路。即通过波动分析法界定剥蚀的区域和厚度范围,再精确计算原型盆地剥蚀量。并以惠民凹陷新生代为例,首先运用波动分析原理,得出反映凹陷形成与发展的主周期波为57,27和7.5 Ma,根据7.5 Ma的周期波反映凹陷内不同沉积期间断面的剥蚀情况,来确定区域的剥蚀范围。然后根据惠民凹陷的地质特点及资料情况,采用沉积速率法、镜质体反射率差值法、地层对比法等来恢复局部地层的剥蚀量。在波动分析法的约束下,参考地质沉积史和构造演化分析的结果,综合加权平均得到最终的地层剥蚀厚度,以确保计算结果精确。研究结果表明:受波动旋回的影响,沙四段和孔店组地层普遍存在剥蚀,剥蚀厚度较大的区域主要集中在凹陷边缘或靠近隆起区,剥蚀量最小的区域是阳信洼陷,说明该区沙四上亚段和孔二段烃源岩没有遭受破坏,具有较大的勘探潜力。

A new way to calculate the denuded amount of prototype basin is introduced under the restriction of the wave analysis method to achieve exact data, that is, restricting the denuded area and its amount range by the wave analysis method firstly, then accurately calculating the erosion amount in combination with other methods. And taking the Cenozoic layers of the Huimin depression as an example, using the wave analysis theory, the 57, 27 and 7.5 Ma cyclic waves reflecting the formation and development of the depression were obtained, and the denuded region and its amount range were confirmed by the 7.5 Ma cyclic wave which reflected the denuded state of different sedimentary intervals; then based on different geologic and data conditions, the erosion amounts of local layers were calculated by means of the sedimentary rate, vitrinite reflectance and stratigraphic contrast methods. Finally, by consulting the analysis results of geologic history of deposition and structural evolution, the fine denuded amount was obtained by weighted averaging of the results from multi-perspective methods under the restriction of the wave analysis method. The results show that denuded exists pervasively in the Es4 and Ek, and its high amounts are centralized on the edge of the depression or faults, paralleling the lowest amount exits in the Yangxin sag, where the source rocks of upper Es4 and Ek2 were destroyed slightly, which shows that it could be propitious to the preservation of the generated by drocarbon and has good exploration potential.