Preparation of Cleaning Agent for Treatment of Abandoned Oil Pipeline Fajie Yang, Shengmei Chi, Yufen Wen, Hongtao Wang, Jing Li, Feng Zhu, Chunman Li and Wang Tian E3S Web Conf., 194 (2020) 04027 Published online: 15 October 2020 DOI: 10.1051/e3sconf/202019404027