联合微米CT和高压压汞的致密储层孔喉网络结构差异定量评价

Quantitative evaluation of pore-throat network structure differences in tight reservoirs with combined micro-CT and high pressure mercury

阐明致密储层孔喉网络结构特征对明确油气富集主控因素,预测有利储层分布具有重要意义。联合微米CT和高压压汞技术,构建包括主流孔喉半径、幂指数、孔隙连通率和多重分形维数在内的孔隙结构参数,对鄂尔多斯盆地延长组长8—长6段孔喉半径分布、孔喉网络非均质性和连通性及其差异进行定量评价。结果表明,长6和长8段样品孔径分布特征较好,长6段主流孔隙半径为2.27μm,幂指数最小,储集能力最强。长8段样品0.1~0.5μm的喉道比例最高,对储层可动流体分布的控制作用最强。不同层段样品非均质性差异明显,在半径大于1μm区间内,长7段非均质性最弱,孔隙结构最好。长7和长6段样品的孔隙连通性要好于长8段,配位数和孔体积的有利匹配能提高储层孔隙连通性。

Demonstrating the tight reservoir pore-throat network structure is of great significance to clarify the main controlling factors of hydrocarbon accumulation and predict the favorable reservoir distribution.The pore-size distribution,pore-throat network heterogeneity and pore connectivity of Yanchang Formation Chang 8 to Chang 6 tight reservoirs in the Ordos Basin and their differences were evaluated quantitatively,by combining micro-CT and high pressure mercury intrusion and building the parameters such as dominant pore-throat size(DOMsize),power exponent(k),pore connectivity rate(Cr)and multi-fractal dimensions(D).The results showed that Chang 6 sample displays the great features characterized by maximum DOMsize(2.27μm),minimum k and strongest storage capacity.The throat(0.1~0.5μm)proportion of Chang 8 sample was higher than that of other samples,which indicated its strongest control over the movable fluid in reservoir.The pore-throat heterogeneity had obvious differences among three members.The Chang 7 sample showed the weakest heterogeneity and the best pore structure within the radius range of>1μm.The pore connectivity of Chang 7 and Chang 6 samples are better than that of Chang 8 sample,and it could be improved dramatically by the beneficial association between coordination number and pore volume.