Why use a casing centralizer

Casing centralizer is an important measure to improve the quality of cementing. The purpose of cementing is two things. First, casing is used to seal off Wells that are prone to collapse, leakage, or other complicated conditions, so as to provide guarantee for continued safe and smooth drilling. The second is to effectively seal different oil and gas layers, prevent oil and gas from flowing to the ground or leaking between the strata, and provide channels for the production of oil and gas.

According to the purpose of cementing, the standard of evaluating cementing quality can be obtained. The so-called good cementing quality mainly means that the casing is centered in the hole, and the cement ring around the casing effectively separates the casing from the well wall and the formation from the formation. However, the actual borehole drilled is not absolutely vertical and will produce deviation to varying degrees. Because of the existence of well inclination, casing will not be naturally centered in the hole, resulting in different lengths and different degrees of sticking to the well wall.

  The gap between the casing and the well wall is different. When the cement slurry passes through the place with large gap, the original mud is easy to replace. On the contrary, the gap is small, because the liquid flow resistance is large, the cement slurry is difficult to replace the original mud, forming the often said cement slurry channeling phenomenon. After the channeling phenomenon is formed, the oil and gas layer cannot be effectively sealed, and the oil and gas will flow through the part without the cement ring.

To use a casing centralizer is to keep the casing as centered as possible during cementing. It is more necessary to use casing centralizer for cementing directional or highly inclined Wells. The use of casing centralizer can not only effectively prevent slurry channeling, but also reduce the risk of casing compression differential sticking.

Because the centralizer centers the casing, it does not lean against the wall. Even in well-permeable Wells, the casing is less likely to get stuck by the mud cake created by the differential pressure. The casing centralizer also reduces the curvature of the casing in the well (especially in large hole sections), which helps protect the casing by reducing wear on the drilling tool or other downhole tools during the drilling process after the casing is placed. Because the casing centralizer supports the casing, the contact area between the casing and the well wall is reduced, so the friction between the casing and the well wall is reduced, which is conducive to the casing running into the well and the casing moving during cementing.

To sum up,the use of casing centralizer is a simple and important measure to improve the quality of cementing.