碳酸溶蚀对砂岩储层物性特征及孔隙结构的影响

The Influence of Carbonate Dissolution on Physical Properties and Pore Structure of Sandstone Reservoir

以鄂尔多斯盆地长6不同渗透率级别砂岩岩心为研究对象,系统研究了碳酸溶蚀前后岩心物性特征、矿物组成以及孔隙结构的变化特征。结果表明:对于较低渗透率的岩样,碳酸水的溶蚀作用造成除石英外的其他矿物组分含量均有所下降,而对于高渗岩样,由于孔隙空间比表面积较小,使得矿物与碳酸水作用强度较弱,少量方解石和长石被溶解而含量下降,其他矿物相对含量有所升高。随着碳酸水的不断注入,渗透率为0.1 mD的岩心孔隙度和渗透率均不断增大,渗透率为1.0 mD的岩心孔渗均是先减小后增大,当岩心渗透率为10 mD时,岩心孔隙度和渗透率均不断减小。总体上,孔隙度相对变化率在-5.77%~-3.68%之间;渗透率相对变化率在-21.87%~-18.47%之间。研究结果揭示了不同孔渗级别砂岩与碳酸水相互作用下孔喉结构变化特征,能够为低渗储层CO_(2)驱油和埋存方案的制定提供重要理论依据。

The change of physical properties,mineral composition and pore structure of Chang 6 sandstone cores with different permeability levels in Ordos Basin before and after carbonic acid dissolution were systematically studied.The results show that for rock samples with low permeability,the content of other mineral components except quartz decreases due to the dissolution of carbonate water,while for rock samples with high permeability,due to the small specific surface area of pore space,the interaction strength between minerals and carbonate water is weak,and a small amount of calcite and feldspar are dissolved and the content decreases,while the relative content of other minerals increases.With the continuous injection of carbonate water,the porosity and permeability of the core with a permeability of 0.1 mD increase continuously,and the porosity and permeability of the core with a permeability of 1.0 mD decrease first and then increase.When the core permeability is 10 mD,the core porosity and permeability decrease continuously.In general,the relative change rate of porosity is between-5.77%and-3.68%.The relative change rate of permeability was between-21.87%and-18.47%.The research results reveal the characteristics of pore throat structure changes under the interaction between sandstone with different porosity and permeability levels and carbonate water,which can provide an important theoretical basis for the formulation of CO_(2) displacement and storage schemes in low permeability reservoirs.