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在对鄂尔多斯盆地白豹—华池地区长8段砂岩储层特征、主控因素分析及地层埋藏史和成岩史研究的基础上,应用数理统计的方法,以现今孔隙度为约束条件,将孔隙度演化分为孔隙度减小和孔隙度增大2个过程,分别建立了鄂尔多斯盆地白豹—华池地区长8段砂岩储层从埋藏初始至现今的孔隙度随埋藏深度和地史时间变化的演化模型。结果表明:孔隙度定量演化模型为一个4段式分段函数。机械压实阶段为孔隙度减小模型,是以埋深为自变量的连续函数;压实和胶结作用阶段为孔隙度减小模型,是对埋深和埋藏时间的连续函数;次生增孔是由于地层酸性流体的溶蚀作用而产生的,主要发生在80～100℃的温度窗口内。因此,溶蚀阶段为孔隙度增大模型,是对埋深和埋藏时间的复合函数;溶蚀阶段结束后地层孔隙度为压实和保持阶段,孔隙度减小模型是对埋深、埋藏时间及增孔量的叠加复合函数。实例验证结果表明在研究区建立的该砂岩孔隙度定量演化模型符合地质实际,可以推广应用到研究区相似岩性、埋藏年代和沉积类型的地层孔隙度计算中,为孔隙度预测提供定量计算方法,以期对该区油气勘探提供借鉴意义。
Based on the analysis of the characteristics and main controlling factors of Chang 8 sandstone reservoir in the Baibao-Huachi region in the Ordos Basin and the study on the burial history and diagenesis of the strata, mathematical statistics method is used to calculate the porosity The evolution of the degree is divided into two processes, the decrease of porosity and the increase of porosity. The porosity of the Chang 8 sandstone reservoir in the Baibao-Huachi area, Ordos Basin, has been established with the change of burial depth and geo- Evolutionary model. The results show that the quantitative evolution model of porosity is a 4-segment segmentation function. The mechanical compaction stage is the porosity reduction model, which is a continuous function with the depth as the independent variable. The compaction and cementation stage is the porosity reduction model, which is a continuous function of burial depth and burial time. Is due to the dissolution of acid fluid formation, mainly in the temperature window of 80 ~ 100 ℃. Therefore, the dissolution stage is a model of porosity increase, which is a composite function of burial depth and burial time. After the dissolution stage, the porosity of the formation is the compaction and holding stage. The porosity reduction model is a function of burial depth, burial time, Hole stacking function. The results of the example verification show that the quantitative model of porosity evolution of sandstone in the study area accords with the geological reality and can be applied to the formation porosity calculation of similar lithology, burial age and sedimentary type in the study area to provide a quantitative calculation method for porosity prediction , With a view to provide reference for oil and gas exploration in this area.