向源潜流侵蚀岩溶作用及其成因机理——以塔河油田早海西风化壳岩溶洞穴层为例

向源潜流侵蚀作用指在海(水)进环境中,由于盆地边缘岩溶斜坡带内陆区的潜水面上升后,潜水面以下地下潜流在相当长时间内仍然在原有的洞穴内流动,由此产生的连续向上(向着地下水流源头)侵蚀作用,其结果是在原有的洞穴层之上形成多旋回的具有`坍塌角砾- 暗河沉积’ 双层结构的塌积层序及纵向上呈加积方式产出的叠积洞穴层,以及由叠积洞穴与原有洞穴连成一体的复合洞穴层。本文以塔河油田早海西风化壳岩溶洞穴层为例,简要地介绍了古岩溶洞穴层的对比方法,展示了塔河地区早海西风化壳岩溶洞穴层对比成果,并通过典型井的洞穴层内部结构解剖分析,阐述了向源潜流侵蚀岩溶作用的成因机理,并探讨了一些相关的主要问题。 

THE MECHANISM OF RETROGRESSIVE EROSION AND KARSTIFICATION A CASE STUDY OF CAVE FORMATION IN EARLY HERSINIAN WEATHERED CRUST IN TAHE OILFIELD

Retrogressive erosion refers to the continued upward and head-ward erosion towards groundwater source produced by the flow of groundwater in cave under the water table after the water table in inner land on the verge of karst basin slope rises during transgression. The erosion results in multi-cycled collapse sequences and aggradational caves being developed over the original cave. The collapse sequence is composed of huge collapsed breccias and underground fluvial deposits. The aggradational cave is characterized by the filling of fluvial deposit and aggradational distribution. The complex huge cave is composed of the water table cave and the above aggradational cave. In this paper, the methods for the comparison of paleo-cave layers in the Early Hersinian weathered crust in Tahe oilfield is introduced, the result from the comparison of paleo-cave layers is showed, the mechanism of retrogressive erosion and karstification is illustrated through the analysis on configuration of the deposits filled in the huge cave and the dynamic model of underflow, and some key problems associated with retrogressive karstification are discussed.