Reduction of erosion rate by particle size distribution (PSD) modification of hematite as weighting agent for oil based drilling fluids

Natural hematite (Fe2O3) and barite (Ba2SO4) are usually employed as weighting agents for oil based drilling fluids in several venezuelan fields. Hematite has shown some physico-chemical advantages with respect to barite: a greater specific gravity and solubility in acid media and lower attrition rate. However, the most challenging issue related to hematite field applications has been to reduce its high erosive potential. Effects of particle size distribution (PSD) have been evaluated with four different samples of hematite (48, 38, 30 and 18 μm based on the statistical parameter D(v,0.9)) respect to commercial barite. These samples were used to prepare fluids with a density of 1977 kg/m3. An erosion test loop was used to expose different samples of AISI 1020 flat steel to the erosive action of jet fluid. Wear of metallic samples was measured by weight lost and wear mechanisms were identified by laser profilometry, SEM and EDS. The investigation showed that the erosion rate (E) produced by hematite decreases potentially with size grain reduction (D(v,0.9)) and depends on the morphology and angularity of the particle in comparison with barite. Laboratory results were validated on field tests with drilling fluids formulated with hematite of different PSD.