珠江口盆地恩平凹陷碎屑岩储层孔隙度纵向演化特征

VERTICAL POROSITY VARIATION OF CLASTIC RESERVOIR ROCK IN ENPING SAG,ZHUJIANGKOU BASIN

首先分析了珠江口盆地恩平凹陷不同层位的孔隙度纵向演化特征与成岩作用之间的关系,然后通过相关性分析并结合多元逐步回归方法,找出了孔隙演化的主控因素,抽象出恩平凹陷孔隙的"3段式"演化模式,即在不考虑次生溶蚀作用和早期碳酸盐胶结等化学成岩条件下,恩平凹陷的孔隙演化具有高孔锐减段、稳定下降段和缓慢减缩段明显的演化规律,其中高孔锐减段表现为压实初期的原生粒间孔迅速减少,稳定下降段是高孔锐减段这一陡变带之后出现的缓变带,缓慢减缩段是埋藏到一定深度后随深度的增加孔隙度下降不明显的深部紧密压实带,认为通过这一演化规律可以较好地评价类似盆地深部储层的经济基底。

In this context, the relationship between diagenesis and vertical variation of porosity within the different strata in the Enping sag, Zhujiangkou basin is set up. Based on the correlation analysis and multivariate regression, the main controls on the porosity evolution is discussed and the ＂three-section model＂ of porosity evolution is setup; for example the vertical porosity variation of clastic reservoir in the Enping sag shows the obvious three-section evolutionary feature when secondary dissolution and early carbonate cementation is not involved, including high porosity sharp-decreasing section, stable decreasing section and slow decreasing section. The high porosity sharp-decreasing section displays the abrupt decrease of the primary porosity during the early compaction. Then the stable decreasing section is happened after the first section with gentle decrease of porosity because of the anti-compaction ability enhancement of clastic rock. The slow decreasing section is an intangibly decreasing section due to the tight compaction zone within deep burial after the gradual increasing depth. This principle of the porosity evolution can be used to evaluate the economic basement of deeply buried reservoir in the Enping sag and similar basins.