Normal Injection, Reverse Squeeze and Intermediate Diversion: A Technology for Cementing the Complex Well **1-H*

The second interval of the well **1-H* penetrated the Neogene N₂k, N_1-2k, the upper N₁j (claystone, interbeds of sand shale and sandy conglomerate) and the lower N₁j (claystone, sandstone and interbeds of gypsum and claystone), and was drilled to the top of the Paleogene E_2-3s formation (claystone), providing conditions for drilling the third interval. Several high pressure water zones are found between 5065 m and 5360.53 m of the second interval, with overflow of well at static condition when mud weight was 1.51 g/cm³. Mud loss was encountered at pumping between 5318 m and 532,51 m, and there was only 2.47 m of claystone worked as a baffle layer. The drilling process of this interval and wireline logging were accompanied by the continual well killing and mud loss control because of the coexistence of mud loss and overflow in the same interval. This interval was drilled to 5363 m and was cased with φ244.5 mm casing string. A cement slurry with anti-channeling agents for invasion resistance, LCM, enhanced toughness, three setting points, double densities and salt resistance was used in the well cementing job. Normal injection, reverse squeeze and intermediate diversion were taken to ensure the success of the well cementing job. The quality of the well cementing job met the designed requirements.