东营凹陷地下水动力场的形成与演化

FORMATION AND EVOLUTION OF HYDRODYNAMIC FIELD IN THE DONGYING DEPRESSION

沉积盆地地下水动力场的理想模式可以归纳为对称型和不对称型两种 ,其中局部地下水动力单元可以划分为泥岩压榨水离心流 ,大气水下渗向心流 ,越流、越流 蒸发泄水和滞流 4种类型。地下水动力场的演化具有旋回性 ,每个旋回可以分为两个阶段 :盆地沉降沉积时期的泥岩压榨水离心流阶段和盆地抬升剥蚀时期的大气水下渗向心流阶段。随沉积盆地的形成与演化 ,水动力场也有形成、发展和消亡的过程。东营凹陷地下水动力场在平面上呈对称性 :总体上大气水由凹陷边缘向凹陷中心渗入 ,凹陷内部各洼陷为压榨水形成的离心流区 ,凹陷边缘南部斜坡带和北部断阶带以及凹陷内部中央断裂带为越流泄水区。纵向上 ,局部水动力单元强度及演化规律与地层的埋藏深度有关。随着埋藏深度的增加 ,水动力单元强度逐渐减弱。

Theoretical models of hydrodynamic field in a sedimentary basin could be concluded as two types: symmetrical and asymmetrical ones. Four types of local groundwater hydrodynamic units in the basin could be recognized: ①centrifugal flow caused by mudstone compaction at depression areas; ②gravity-induced centripetal flow recharged by meteoric water along basin margins generally; ③discharge area by cross-formational flow, or cross-formational flow and evaporation, and ④stagnation flow area. The evolution of hydrodynamic field had the property of a hydrogeological cycle. It could be divided into centrifugal flow stage during which the basin subsided and sedimentation occurred, and centripetal flow stage during which the basin uplifted and eroded. Accompanying the origin and evolution of sedimentary basin, hydrodynamic field underwent a process of origin, development and perished at last. Obviously, the hydrodynamic field in the Dongying Depression was symmetrical, with the characteristics of gravity-induced centripetal flow recharged by meteoric water along the edges of the depression, centrifugal flow formed by compaction in the central depression area, and cross-formational flow and concentration by evaporation in the southern slope and northern fault ramp along the basin margins and the central fracture zone in the interior depression area. The intensity of hydrodynamics had the property of vertical zoning. The intensity weakened gradually with the increasing depth.