Abstract: Well Klari-2st is a directional exploratory well in Block Arar, Indonesia. In order to accomplish the exploration of the block, the ?215.9 mm leaking openghole section is backfilled with cement; then drill with ?152.4 mm drill bit and enlarge the hole with a reamer to form a ?177.8 mm cement ring hole; then run in ?149.2 mm expansion pipe to seal the wellbore so as to finish the 4th spud drilling. By analyzing the failure on pervious cement ring, we improved the cementing fluid system and added bentonite, fiber and expansion agent to the slurry to reduce the strength and brittleness of set cement stone and improve the toughness of set cement and its crosslinking intensity with well wall. By using shock-resistant high tenacity cement accompanied with the prepad fluid system of efficient flushing fluid and viscidity spacer fluid and other methods, we successfully pumped cement plugs, which satisfied the requirement that the maximum diameter of expansion pipe wellbore is less than ?190 mm.