基于孔隙度演化模拟的低孔低渗砂岩成岩相划分——以鄂尔多斯盆地晋西挠曲带二叠系为例

Diagenetic Facies Classification of Low-Porosity and Low-Permeability Sandstones Based on Porosity Evolution Simulation: A Case Study from Permian Strata in Jinxi Flexure Belt,Ordos Basin

低孔低渗油气藏勘探开发的关键,是预测其储集层物性相对较好的区域,以寻找含油气有利区。在一定的沉积环境下,成岩相是控制储集层物性的核心因素。划分油气富集区的成岩相,应考虑成岩作用对储集层孔隙空间的影响程度。依据岩石组分、面孔率以及岩石物性资料,通过孔隙度演化模拟,在原始孔隙度的基础上模拟出压实、胶结和溶蚀等成岩作用前后的孔隙度变化,采用视压实率、视胶结率和视溶蚀率表征成岩作用对孔隙空间的建设与破坏程度,使得这种作用程度数据化。在此基础上,基于视压实率、视胶结率和视溶蚀率数据,将成岩作用分为强、中和弱3类,综合压实、胶结和溶蚀强度,对成岩相进行定量划分。应用此划分方法,把鄂尔多斯盆地晋西挠曲带二叠系成岩相划分为强胶结强溶蚀相、强胶结中溶蚀相和中胶结中溶蚀相3种相类,划分结果与岩样薄片分析结果一致。

The key to exploration of low-porosity and low-permeability reservoirs is to predict the reservoirs with relative good physicalproperties to find favorable petroliferous areas. In a certain sedimentary environment, diagenetic facies is the core factor controlling thephysical properties of reservoirs. The diagenetic facies which can be used to classify petroliferous areas should consider the influence of dia-genesis on pore spaces of reservoirs. Based on rock components, surface porosity and petrophysical properties and through porosity evolu-tion simulation, porosity variations before and after diagenesis such as compaction, cementation and corrosion are simulated on the basis ofprimary porosity. Apparent compaction rate, apparent cementation rate and apparent corrosion rate are used to represent the constructionand destroy degrees of pore spaces caused by diagenesis and the degrees could be digitalized. Based on the data of apparent compactionrate, apparent cementation rate and apparent corrosion rate, diagenesis can be divided into 3 types, namely strong, moderate and weak dia-genesis. Based on the intensities of compaction, cementation and corrosion, diagenetic facies can be classified quantitatively. With thismethod, the Permian diagenetic facies in Jinxi flexure belt of Ordos basin are classified as strong cementation and strong corrosion facies,strong cementation and moderate corrosion facies and moderate cementation and moderate corrosion facies, which is in accordance withthe results from thin section analysis.