Why do we need to use casing centralizer?

The use of casing centralizer is an important measure to improve the quality of cementing.

The purpose of cementing is twofold: firstly, to seal off the well sections that are prone to collapse, leakage, or other complicated conditions with casing, so as to provide a guarantee for the continuation of safe and smooth drilling. The second is to effectively seal off different oil and gas formations, so as to prevent oil and gas from escaping to the ground or escaping between formations, and to provide a channel for the production of oil and gas.

According to the purpose of cementing, the criteria for evaluating the quality of cementing can be derived. The so-called good quality of cementing mainly means that the casing is centered in the borehole and the cement ring around the casing effectively separates the casing from the well wall and the formation from the formation. However, the actual drilled borehole is not absolutely vertical, and well slant will be generated to varying degrees. Due to the existence of well inclination, the casing will not be naturally centered in the borehole, resulting in the phenomenon of different lengths and different degrees of sticking to the well wall. Formation of the casing and the well wall gap between the size of different, when the cement paste through the gap is large, the original mud is easy to replace the mud; on the contrary, the gap is small, due to the liquid flow resistance is larger, the cement paste is difficult to replace the original mud, the formation of the commonly known slurry slurry trenching phenomenon. After the formation of trenching phenomenon, it can not effectively seal off the oil and gas layer, oil and gas will flow through the parts without cement ring.

The use of casing centralizeris to make the casing centered as much as possible during cementing. For directional wells or wells with large inclination, it is more necessary to use casing centralizer. In addition to effectively preventing cement slurry from running out of the groove, the use of a casing corrector also reduces the risk of the casing being stuck by the differential pressure. Because the casing is centered, the casing will not be close to the well wall, and even in the well section with good permeability, the casing will not be easily stuck by the mud cake formed by the differential pressure, which will lead to stuck drilling. The casing centralizer can also reduce the degree of casing bending in the well (especially in the large borehole section), which will reduce the wear and tear of drilling tools or other downhole tools on the casing during the drilling process after the casing is lowered, and play a role in protecting the casing. Due to the centralizer of the casing by the casing centralizer device, the contact area between the casing and the well wall is reduced, which reduces the friction between the casing and the well wall, and is conducive to the lowering of the casing into the well, and is conducive to the movement of the casing when cementing the well.

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