白云岩差异压实及对储层物性保存的控制作用

Differential compaction of dolostone reservoir and its controlling effect on physical property preservation

为明确中—深埋藏成岩阶段压实作用下白云岩物性的演化规律和保存机制,利用非稳态压力衰减孔渗联测方法,对孔隙型、孔洞型和裂缝型3种孔隙空间类型白云岩的抗压实效应进行模拟试验对比研究。结果表明:随着有效应力增加,白云岩物性相应下降,且孔隙空间类型和初始物性不同导致白云岩压实效应存在差异,其中孔隙型细分为孔隙Ⅰ型和孔隙Ⅱ型;在有效应力加大过程中,孔隙Ⅰ型和孔洞型白云岩储集空间抗压实能力强,孔隙度演化特征为早期快速下降、后期基本不变;裂缝型和孔隙Ⅱ型白云岩储集空间抗压实能力弱,孔隙度演化规律为早期快速下降、后期持续下降;孔隙Ⅰ型白云岩连通属性抗压实能力强,有效应力超过10 MPa后,渗透率基本保持不变;孔隙Ⅱ型、孔洞型和裂缝型白云岩连通属性抗压实能力依次变弱,渗透率随有效应力的增加具有早期快速下降、后期持续下降特征。

In order to clarify the evolution and preservation mechanisms of reservoir space and connectivity properties of dolomite under the action of compaction in medium-deep burial diagenetic stage,a combined measurement method of unsteady pressure attenuation porosity and permeability were used to conduct a comparative study on the compaction resistance of dolostone of porosity type,porosity-vuggy type and fracture type.The results show that the porosity and permeability of dolostone decrease correspondingly as the effective stress increases.The preservation law of physical properties of dolostone is also different due to differences in pore types and initial physical property.The porosity type is further divided into typeⅠand typeⅡ.In the process of gradually increasing effective stress,the porosity preservation ability of dolostone from high to low is porosity type I,vuggy type,fracture type and porosity typeⅡ,respectively.The reservoir spaces of porosity typeⅠand vuggy type dolostone have a strong ability to resist compaction,and their porosity evolution can be characterized by a rapid decline in the early stage which then asymptotically flattens in the later stage.The reservoir spaces of fracture type and porosity typeⅡdolostone have weak ability to resist compaction,and their porosity evolution rule is that the porosity decreases rapidly in the early stage and continues decreasing in the later stage.In the process of gradually increasing effective stress,the connectivity properties of porosity type I dolomite have a strong compaction resistance.When the effective stress exceeds 10 MPa,the permeability basically remains unchanged.The compaction resistance of connectivity properties of porosity typeⅡ,vuggy type and fracture type dolostone decreases successively,and permeability decreases rapidly in the early stage and continuously in the later stage with the increase of effective stress.