In high-density drilling fluids, maintaining low plastic viscosity (PV) to reduce Equivalent Circulation Density (ECD) and consequently achieve a higher rate of penetration comes with its own challenges. A low PV indicates that the drilling fluid is capable of drilling faster due to the low viscosity fluid exiting at the bit. PV represents the viscosity of drilling fluids when they are extrapolated to an infinite shear rate based on the Bingham model.

High PV is caused either by a viscous base fluid or by an excessive solid content in drilling fluids. The usage of a new product, Cerium Oxide (CeO2) with S.G at 6.0, referred to as CERITE in this paper, has been evaluated in a HTHP drilling fluid.

CERITE allows the drilling fluid to achieve higher density where the solid content in the mud is much lower than traditional weighting materials that are added to the drilling fluids.

A drilling fluid THAT IS formulated with CERITE as weighting material has a lower solids content due to the higher S.G. of CERITE and thus contributes to effective management of ECD without needing to restrict the drilling rate compared to drilling fluids that have been weighed up using API Barite

The objective of this study is to discuss the performance of a HTHP drilling fluid where CERITE has been used as a weighting material. Hence, two batches of HPHT water-based mud (WBM) with a density of 2.0 SG, one containing API standard Barite and the other CERITE, were compared. HPHT filtration is measured under static conditions at 400 °F and 500 psi. A Particle Plugging Apparatus (PPA) is used at 2000 psi differential pressure for measuring the filter cake sealing capability on a ceramic disk. The rheological properties, particle size distribution (PSD), sag tendency, the volume of filtrate, and the filter cake thickness of the drilling fluids are measured after hot rolling the mud at 400 °F for 16 hours. Circulation hydraulic and frictional pressure loss measurement using rheology model as Power-Law is simulated to evaluate the effects of this product on equivalent circulating density (ECD) reduction against the API Barite.

This paper discusses the extensive lab test results for the performance of CERITE against API Barite that has been added in a HTHP WBM system and ultimately concludes suitability of this material as a weighting agent.

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