Casing First Or Cementing First?

Casing refers to the process of inserting a casing pipe into the wellhead during the drilling process to protect the well wall and maintain the integrity of the wellbore. It is also the prerequisite for cementing in the next step. Cementing refers to the process of forming a cement ring around the casing pipe after lowering the casing pipe to maintain the stability of the casing pipe, eliminate the passage between the fluid inside and outside the well, make the wellbore meet safety standards and prevent environmental pollution.

Purpose of lowering casing pipe

1. Protect the wellbore wall: The drill bit will wear the wellbore wall during the drilling process, and lowering casing pipe can protect the wellbore wall from being worn.

2. Maintain the integrity of the wellbore: After the casing pipe is lowered, the integrity of the wellbore wall can be maintained to prevent the wellbore from collapsing.

3. Improve drilling efficiency: Lowering casing pipe can shorten drilling time and improve drilling efficiency.

Purpose of cementing

1. Maintain the integrity of the wellbore: Cementing can ensure the stability of the casing pipe and avoid the problem of excessive annulus or blank space.

2. Prevent the mixing of fluids inside and outside the well: The cement ring formed during the cementing process can prevent the mixing of fluids inside and outside the well, achieving the effect of isolating oil, water, gas, and salt.

3. Protect groundwater resources: Cementing can ensure that crude oil, natural gas, etc. will not leak into the groundwater layer, protecting groundwater resources.

Casing first or cementing first

During the drilling process, the drilling supervisor, drilling engineer, and cementing engineer usually negotiate the order of casing and cementing, and choose whether to casing first or cement first.

In general, casing should be lowered before cementing. Because if cementing is performed first, it will affect the firmness of casing pipe and increase the difficulty of casing pipe. In addition, if casing pipe is lowered before cementing, it can reduce time and cost and improve drilling efficiency.

However, there are some cases where cementing is required first. For example, if groundwater is found during drilling, it is necessary to isolate the groundwater as soon as possible to prevent environmental pollution.

Conclusion

In drilling projects, whether to run casing pipe first or cementing first requires negotiation and trade-offs, and different situations may choose different orders. But in general, casing should be run first and then cementing to improve the efficiency and benefits of drilling projects.