<p class="6Abstract22" style="margin: 0cm 20.15pt 0pt;"><span style="font-size: small;"><span style="font-family: Times New Roman;"><span style="mso-spacerun: yes;"> </span><span lang="EN-AU">G<a href="javascript:showjdsw('showjd_1','j_1')">as breakthrough</a> is a common problem in CO2 displacement. This paper provides a new method with ethylenediamine to improve the efficiency of CO2 injection, sealing off the breakthrough channel. Experiments in porous medium model show that the ethylenediamine system can be easily injected into extremely low permeability reservoir, it can react with CO2 and the generated carbonate will reduce the permeability of the flooding region, causing the breakthrough pressure reaches 22MPa, hence, the swept efficiency is improved. Oil displacement experiment with heterogeneous core shows that the recovery factor is improved by 19.8%. Additionally, the ethylenediamine system shows high temperature resistance and CO2 erosion resistance. It also has an advantage of selective plugging, it will not injury the reservoir where CO2 does not pass by as long as we chose the suitable injection speed, <a href="http://dict.cnki.net/dict_result.aspx?searchword=%e5%89%8d%e7%bd%ae&tjType=sentence&style=">prepositive</a> and <a href="http://dict.cnki.net/dict_result.aspx?searchword=%e5%90%8e%e7%bd%ae&tjType=sentence&style=">postpositive</a> slug. So we could control CO2 breakthrough by profile control. </span></span></span></p><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 10.5pt; font-family: "Times New Roman","serif"; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-fareast-language: ZH-CN; mso-ansi-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt;" lang="EN-US">Key words:</span></strong><span style="font-size: 10.5pt; font-family: "Times New Roman","serif"; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-fareast-language: ZH-CN; mso-ansi-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt;" lang="EN-US"> <span style="mso-spacerun: yes;"> </span>ethylenediamine; plugging; CO2; heterogeneity; profile control</span>