How is drilling fluid formulated for external stabilizer drill pipes?
30 Jun,2020
In routine operations, if cuttings fail to return smoothly to the surface, there is a high risk of getting the drill bit buried. Therefore, if you notice a decrease in or complete absence of cuttings returning to the surface, you should immediately adjust the drilling fluid properties until the cuttings flow back to the surface as expected.
External Drill Pipe In daily work, if cuttings fail to return easily to the surface, there is a high risk of getting stuck—known as "buried drill" incidents. Therefore, if you notice a reduction in or complete absence of cuttings returning to the surface, you should immediately adjust the drilling fluid properties until the cuttings begin flowing back to the surface as usual.
The simplest and most effective solution is to add xanthan gum or a high-viscosity plugging agent, which will increase the viscosity of the drilling fluid funnel by 20–30 seconds, allowing cuttings to return smoothly to the surface.
If cuttings are not returning easily due to wellbore collapse caused by oversize formations, then in addition to the two materials already used, bentonite should also be added to increase the drilling fluid’s density and the strength of its network structure. This will help stabilize the wellbore, preventing further collapse or sloughing, and ensure that both cuttings and debris are effectively carried out of the well.
What is the relationship between cuttings, false narrowing, sticking due to adhesion, and bit balling?
Cuttings generate mud, causing the cuttings content in the drilling fluid to steadily increase. When the cuttings concentration exceeds 10% and the fluid loss exceeds 9 ml/30 min, a thick mud cake—over 3 ml in thickness—begins to form on the wellbore wall in the secant section. This leads to false shrinkage, reducing the wellbore diameter below the drill bit’s outer diameter and resulting in stuck pipe during tripping operations. If the section of false shrinkage becomes particularly long, once drilling is halted, External Drill Pipe The drill collar and drill pipe become tightly bonded to the mud cake on the wellbore wall, resulting in sticking due to adhesion. During the process of pulling out of the hole, the drill bit scrapes off the mud cake—but the mud cake also adheres strongly to the outside of the drill bit, gradually increasing its outer diameter. When the mud-packed drill bit expands beyond the wellbore's diameter, it encounters resistance during retrieval. If the applied pulling force becomes too great, the mud-packed drill bit can even get stuck entirely.
Factors Affecting Bentonite Performance
1. Raw ore quality: The level of montmorillonite content in the raw ore is the most critical factor influencing bentonite performance—higher montmorillonite content directly correlates with a higher bentonite slurry yield.
2. Particle Size: The finer the particle size, the higher the slurry yield—and vice versa.
3. Additives: Appropriately adding a dispersant can significantly enhance the performance of bentonite.
4. Water Quality: Bentonite's water-creating efficiency significantly decreases—or even fails to form a slurry—under conditions of high mineralization and acidity.
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