Understanding and Recognition of Three Key Indicators in Bentonite Mud浆

Our understanding and recognition of three key indicators in clay slurry:

(1) Viscosity: Viscosity reflects the internal friction between the tiny particles of bentonite in a water solution. It is the relative motion between particle dispersion and aggregation. The inherent driving force for this motion is the chemical potential difference between the particle end surfaces.

The viscosity in the mud soil standards refers to the apparent viscosity (viscosity by sight). Apparent viscosity is composed of plastic viscosity and structural viscosity, that is: Apparent Viscosity = Plastic Viscosity + Structural Viscosity.

Although the viscosity index indicates a value with ≥, it's not necessarily the case that higher is better. In short: If the high viscosity value is not due to high plastic viscosity but rather high structural viscosity, it suggests that the clay particles in the mud system have a greater coalescence ability than dispersion. At this point, the drilling mud loses its rheological properties, thereby also losing its role and significance in drilling operations.

(2) Yield Value/Plastic Viscosity: This indicator reflects the shear stress required to initiate fluid flow, essentially representing the structural viscosity of the mud. The numerical symbol used for this indicator is ≤, indicating that the lower the value, the better. In other words, the lower the structural viscosity of drilling mud is preferred. The corresponding plastic viscosity, on the other hand, is better when higher.

(3) Loss volume: This indicator reflects the amount of water that escapes from drilling mud under pressure within a specific time frame. The more water that is lost from the mud, the thicker and looser the mud cake formed on the wellbore becomes. A thick and loose mud cake is detrimental to drilling operations, potentially causing stuck pipe, irregular wellbore diameter, and even wellbore collapse. Therefore, the value used for this indicator is ≤, meaning the lower the better. A smaller loss volume results in a thinner and denser mud cake during drilling, leading to better wall protection.