A sample preparation method for acid-sensitive weakly-cemented artificial sandstone with its application in acid-erosion seepage test
YANG Xin1，HONG Yi1，2，WANG Llizhong1，2，GUO Zhen1，2，ZHENG Jianan1，YAN Mengqiu2
(1. College of Civil Engineering and Architecture，Zhejiang University，Hangzhou，Zhejiang 310058，China；
2. Hainan Institute of Zhejiang University，Sanya，Hainan 572025，China)
Abstract：Carbon storage is an effective way to reduce CO2 emissions and mitigate environmental problems such as global warming. The porosity and permeability characteristics of storage reservoir are the key factors to determine the efficiency of CO2 storage，one important mechanism among which is the weakening of calcite cementation by acid erosion，and it is therefore necessary to carry out the researches on weakly cemented sandstone sensitive to acid. This study developed a prepare method of acid-sensitive weakly cemented artificial sandstone，conducted the deformation analysis of acid-sensitive weakly cemented sandstone during acid erosion process，and investigated the change laws of sandstone permeability before and after acid erosion. Firstly，based on the response surface experimental method，the effects of different urease activity，concentration of cementing fluid and concentration of skim milk powder on the strength of acid-sensitive weakly cemented artificial sandstone were studied，and a regression model considering multiple factors was established. Secondly，the acid erosion seepage tests of acid-sensitivity weakly cemented artificial sandstone under different stresses were carried out to analyse the deformation of sandstone during acid erosion：During acid erosion，the sandstone strain increases linearly with the acid flow，and the cementation weakening induced by acid erosion seepage can make the sandstone shrinkage strain exceed 4%. Finally，the change of sandstone permeability before and after acid erosion was studied：The permeability reduced by 70% under high confining pressure. The study reveals the acid erosion characteristics of weakly cemented sandstone，which has a certain guidance on CO2 geological storage project.
