CEMENTING OF THE INJECTION AND PRODUCTION WELLS OF UNDERGROUND GAS ST ORAGE IN DAZHANGTUO

Dazhangtuo gas storage is used to adjust the gas supply in Beijing and Tianjin. Well Ku8 is a directional well drilled in the gas storage block, and its cementing is difficult due to the following problems:1. Low formation fracture pressure, which can cause lost circulation; 2. Low formation pressure factor, which can lead to formation damage; 3. Long cementing interval, and high thermal gradient of 3.4℃/100m, which delays the setting time of upper cement slurry and impacts its gelling. The following measures are adopted to cope with these problems:1. Adopt the temporary shielding cementing technique, to improve the pressure bearing ability of the formation; 2. Apply two-stage cementing. Common cement slurry is used for the first stage cementing, and lightweight cement mainly composed of micro sphere and micro silicate are used for second stage cementing; 3. Control the fluid loss of the cement and the content of free water; 4. Use more casing centralizers to improve the displacement efficiency. SBT logging shows a good cementing job in this well.