SLB is a leading oilfield services company that has provided sub-surface measurement, well-construction and production services to the oil and gas industry worldwide for the last 100 years. A major part of well-construction is drilling the well which, despite being a 100yr old industry, is a process that still experiences significant technical challenges.  These industry challenges continue to be highly relevant as slb extends its, already significant, activity in adjacent energy transition technologies that also require deep drilling, that is geothermal, carbon capture & sequestration and sustainable lithium production.

Here I introduce the company, drilling fluids and the essential parts of a well-construction process. I focus on the ability of drilling fluids to carry rock cuttings to the surface. Within the industry this particle-carriage problem is, in general, modelled using a generalized Newtonian fluid.  Yet there are repeated industry reports comparing fluids where the flow curves are closely similar but where cuttings transport is demonstrably different. To probe this, we combine a Xanthan solution as a proxy for a water-based drilling fluid together with an aqueous Bentonite dispersion that at low concentrations in the Xanthan solution is representative of shale contamination of a water-based drilling fluid. The aqueous Bentonite solution alone has rheological properties similar to those of an oil-based drilling fluid.  The concentrations of each of the two fluids, Xanthan and Bentonite, are chosen so that their generalized Newtonian properties are closely similar. However, their extended rheological properties, in particular normal stress differences, differ markedly.

We examine dense particle motion in a horizontal Couette in the presence of Taylor vortices for each fluid.  We find significant effects dependent on fluid type which, through comparison with our model, we speculatively assign as primarily due to normal forces generated by the background fluid.