典型碳酸盐岩渗透力学行为特征及其对储、盖性质的判定

Using permeability mechanics behavior of typical carbonate to identify reservoir and caprock properties

目前对碳酸盐岩的研究主要关注其油气的储集空间,针对含油气盆地中碳酸盐岩的勘探也主要是为了寻找优质的油气储集体。然而,随着油气勘探向深层更古老的地层拓展,有效的碳酸盐岩储—盖配置显得至关重要。勘探证实,深埋条件下碳酸盐岩有利相带仍然发育高孔渗的优质储集体,然而是否发育与之配置的碳酸盐岩盖层就成为了制约深层碳酸盐岩油气勘探的关键因素。首次系统全面地通过对典型碳酸盐岩开展不同温度条件下三轴应力加载全过程渗透力学试验,得出了碳酸盐岩在破坏变形过程中渗透率随温度、围压的演化过程。试验分析结果显示,典型白云岩和典型灰岩在深埋应力作用过程中渗透力学行为特征具有明显差异,白云岩更多地显示出储集性能的特征,表现为脆—塑转换临界围压较大,岩石更容易形成裂缝,渗透率随温度的增加而增大等;而灰岩则表现出盖层的属性,体现在脆—塑转换临界围压小于白云岩,岩石相对容易形成密闭,渗透率随温度的增大逐渐减小。综合分析认为,白云岩和灰岩的纵向叠置能够形成有效的油气藏储—盖组合。

At present,the study of carbonate rocks mainly focuses on the reservoir space of oil and gas.Howev⁃er,as oil and gas exploration expands into deeper and more ancient formations,effective carbonate reservoircap configuration becomes more critical.Exploration has proved that high porosity and permeability reservoirs are still developed in the favorable carbonate facies zones under deep burial conditions,but the development and configuration of carbonate cap has become a key factor restricting the exploration of deep carbonate rocks.In this study,the permeability evolution with temperature and confining pressure in the process of carbonate rock fail⁃ure and deformation is obtained for the first time systematically and comprehensively by conducting the perme⁃ation mechanics test for the whole process of triaxial stress loading under different temperature conditions for typical carbonate rock.Experimental analysis results show that the penetration of typical dolomite and typical limestone in the process of deep stress mechanics behavior characteristics has obvious difference.Dolomite shows that,the characteristics is more towards the reservoir property,the brittle-plastic conversion critical con⁃fining pressure is larger,rock is easier to form cracks,rock permeability increases with the increase of tempera⁃ture,etc.Generally,the limestone shows the properties of the cap,for example,the critical confining pressure of brittle plastic transformation is lower than that of dolomite,the rock is relatively easy to be closed,and the permeability decreases with the increase of temperature.It is concluded that the longitudinal superposition of do⁃lomite and limestone in carbonate rocks can form an effective reservoir-cap assemblage.