In order to reinforce the wellbore, ensure safe drilling, seal oil, gas and water layers, ensure stratified testing during exploration and ensure reasonable oil and gas production during the whole exploitation process, we put in high-quality casing pipe, and fill the annulus between the wellbore and casing with cement. This is well cementation.
The well cementation steps are as follows:
Put in casing: Unlike drill pipe, casing pipe is a one-time pipe, which has no thickening part and its length is not strictly regulated. In order to ensure the quality of cementing and the smooth running of casing, the structural design of casing string should be done. According to the use, formation prediction pressure and casing depth, the strength of casing is designed, and the thickness of casing, steel grade and thread type are determined.
Cementing: Cementing is the key process after casing pipe is put into well. Its function is to seal the annular space of casing and wall to seal oil, gas and water layers and make casing become the passage of oil and gas to well.
Wellhead installation and casing pressure test: after putting in casing and cement injection, wellhead should be installed during cement solidification. The casing head should be installed at the top of the surface casing. The top of each layer of casing is hanging in the casing head. The casing head is mainly used to support the weight of technical casing and reservoir casing, which is particularly important for cementing cement not returning to the ground. The casing head is also used to seal the annular space between the casings to prevent pressure channeling. Casing head is also a BOP, and transition connection of tubing head. There are also two side ports on the casing head used on land, which can be used for reinforcing cement, monitoring well conditions and injecting balancing fluid.