长庆气田储层的高频层序地层学分析

Sequence Stratigraphy Analysis of High Frequency for Reservoir of Changqing Gas Field

鄂尔多斯盆地长庆气田的主力储层为下奥陶统上马家沟组的马五段 ,属蒸发边缘海相沉积 ,由鲕云岩、颗粒云岩、藻云岩、泥云岩、含膏云岩和膏云岩等组成 .其中高泥质的泥云岩和云泥岩以至含云泥岩 ,代表了洪泛沉积 ,在区内分布广泛而稳定 ,是建立高频层序的标志层 .为此 ,将自然伽玛测井曲线进行频谱分析 ,找出其主频系列 ,经转换得到泥质含量的周期系列 ,从而得出马五1 的高频沉积层序符合米兰科维奇周期的结论 ,即储层马五1的高频沉积旋回是由天文因素控制 ,使该区气候产生了干热和湿热的周期性变化 .

The main reservoir of Changqing Gas Field in Ordos Basin is M 5 1 of upper Majiagou Formation, which belongs to marine deposits of evaporating marginal sea and is composed of oolite dolomite, graindolomite, algal dolomite, pelitic dolomite, gypsodolomite, gypsiferous dolostone, etc. The high pelitic dolostone, dolomitic pelite and slightly dolomitic pelite represent flooding deposits characterized by stable lithofacies and extensive distribution and usually regarded as reference lamina. The spectrum chart and its main frequency series are obtained by utilizing Fast Fourier Tansformation (FFT) to natural gamma logging curves. The ratio of chief-frequency wave length is identical with that of the eccentricity cycle and the tilting cycle, inferring that the high-frequency sedimentary sequence of M 5 1 corresponds to Milankovitch Cycle. It is, therefore, reasonable to deduce the sequence cycle of high frequency of the Reservoir M 5 1 is caused by astronomical factors.