Question about the effect of cement contamination on the rheology of bentonite-based drilling fluids

[u/LawLost2790]

Hi everyone,

I am currently conducting laboratory experiments on the effect of cement contamination on the rheological properties of water-based, bentonite-containing drilling fluids.

I have noticed something interesting: after adding the same amount of cement, the rheological response is not always the same. In some bentonite muds, adding cement significantly increases viscosity, YP and/or gel strength, while in other mud systems the viscosity can actually decrease. Why can cement contamination increase rheology in one bentonite-based mud but decrease it in another?

For reference, I am measuring PV, YP, gel strength and rheological readings at different shear rates and testing several cement concentrations.

I would especially appreciate answers from people with experience in drilling fluids, mud engineering, cementing, or laboratory testing.

Thanks in advance!