The most common fluid model used to determine the rheology of non-Newtonian fluid is the Bingham plastic model. With this model, it has the assumption that the shear rate is a straight line function of the shear stress. The point where the shear rate is zero is called “Yield Point” or threshold stress. Furthermore, the slope of the shear stress and the shear rate curve is called “Plastic Viscosity”. Please see the figure below for more understanding.

Reference Books: Drilling Fluids Book

When you learn about drilling mud, the rheological models are essential knowledge. For this post, I will give you a background of the rheological models prior to going into each model details.

The rheological models are mathematical models used to describe the flow behavior of drilling mud. This topic is critical for drilling fluid study because the models are used to simulate the characteristic of drilling mud under dynamic conditions. With this knowledge, you will be able to determine some key figures as equivalent circulating density, pressure drop in the system, and hole cleaning efficiency.

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You have learned about the gel strength from the previous post. This time we will learn about operational impacts of the gel strength on our drilling operation.

The impacts of the gel strength are as follows;

Cutting suspension ability – Low get strength drilling mud will not be able to efficiently suspend cuttings; therefore, the cutting will quickly drop once pumps are shut down. This can lead to several problems such as stuck pipe, hole pack off, and accumulation of cutting beds.

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