The mechanical casing process, or “cementing” is an important step in the oil and gas drilling process that involves running steel or fiberglass casing into the drilled hole. The purpose of this process is to provide stability to the well, to help prevent the sides of the hole from collapsing as it gets deeper. Additionally, the casing also helps to protect the drilling pipe and provides a seal that protects against water or other contaminants entering the well.
The most important part of cementing a well is the preparation phase, which includes cleaning and pre-conditioning the wellbore before casing is run. Initially the wellbore is cleaned of all debris, channel debris and any loose particles which could interfere with the cementing process. Any areas such as perforations, fractures or reaming should also be corrected. Casing centralizers can be used to ensure the casing is centralized within the wellbore.
After the casing is run into the wellbore and the casing centralizers are installed, a valve is inserted and the cement slurry is started to circulate down the casing. Cementing begins when the cement slurry is brought up to a pressure equal to the fracture pressure of the formation. The pressure of the cementing is then gradually increased, allowing the cement to circulate through the wellbore. To ensure good contact between the casing and the wall of the wellbore, the cement is also displaced multiple times in a pumping process known as “squeeze and bleed”. This process removes any gas or water that was trapped in the annulus between the casing and the wellbore. The rate of pumping is usually increased at this point, helping to ensure a complete seal between the casing and the wall of the wellbore.
Once the cementing process has been completed, the well is pressure tested for integrity. This involves pumping a test fluid into the wellbore and measuring the pressure in the casing and annulus to detect any leakage of fluid. The well is then allowed to “cure”, meaning to allow the cement to reach its full strength. During this time the pressure is monitored closely to ensure there are no signs of wellbore collapse.
In order to properly complete a cementing operation, the company performing the work must have the proper equipment and personnel in order to ensure the process is done correctly. It is important to select an experienced, qualified contractor that will provide consistent, reliable services. Additionally, the contractor must ensure that personnel are trained in the proper techniques and that all safety regulations are being observed.
The cementing process is an important part of the oil and gas drilling process, providing stability to the well and helping to protect against contamination. By using experienced personnel and the appropriate equipment, companies can ensure that the cementing process is done efficiently and safely.
