Then the guide show is attached to the casing pipe’s end. It has a valve that helps ensure the cement flows only to the annulus – the space between the rock formations and pipes – from the casing but not back into it.
Another valve, known as a floating collar, sits on the guide shoe’s top to further prevent mixing between the residual drilling fluids and the cement. The guide show enters the well followed by the bottom plug that’s inserted into the casing. The cement head is then attached to the top of the casing’s last joint at the wellbore’s surface.
The process of pumping the cement solutions into the well then begins. The pressure is initially moderate but gradually increases so the slurry can break the diaphragm of the bottom plug, and the cement can begin flowing into well and on the casing sides through the guide shoe to fill the annulus.
Once all the cement gets pumped, another plug is inserted into the casing to push any cement that may have remained inside the pipe out of the wellbore. There are two types of cementing. The process is known as primary cementing. In case any problem arises during this stage, remedial or secondary cementing can be carried out to fix the mistakes.
Different Types of Cementing
#1- Primary Cementing
When the wellbore drilling is complete, pipes collectively known as well casing are lowered down, and cement is poured using a drill string into the well and on the sides to keep them firmly in place.
Many wells have more casing layers, requiring more than one cement layer between each casing. The layers of cement enhance the functionality of blowout preventers as they help reduce the risk of blowouts.
Besides fixing the casing firmly in place to cut off the water access in the wellbore, cementing also helps plug the lost circulation zones. These include formation cavities that can potentially compromise drilling by diverting lots of drilling mud. This is why plugging is essential. Primary cementing also includes plugging vertical wells prior to beginning directional drilling in shale oil wells.
#2- Secondary Cementing
Sometimes known as remedial cementing, this type of cementing is often used to fix issues created during the primary stage of cementing. However, it also addresses problems that emerge during a well’s lifetime.
Secondary cementing can be applied using two methods, including plug and squeeze cementing. The former involves creating a plug out of cement to inherently seal off holes to prevent the flow of fluids or water from and into the wellbore.
It’s also commonly used during well abandonment once the casing is cut at a specified depth. Wells must then be sealed with cement plugs to restrict the random release of remaining hydrocarbons from the ground.
Squeeze cementing requires pumping some cement down the wellbore at high pressures to fill the cavities that may have been identified as problematic for the safe operations of the concerned well. It’s also used for holes and cracks in rocks or casing cracks.
Interested in learning more? Stay up to date by visiting our resource center, which we update regularly to help you stay informed. As a leading cementing solutions provider, CNPS strives to boost efficiency, productivity, safety, and, ultimately the profitability of O&G operations.
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