Global energy demand has driven petroleum industry to develop hydrocarbon resources from extremelyharsh formations.Ultra-high density drilling fluids are critical to successful drilling and completion practicesin all of these wells.In this paper,potential weighting materials were systematically evaluated and screenedto accomplish an ultra-high density oil-based drilling fluid system (19.62 to 22.12lb/gal)aimed to utilizein ultra HPHT conditions (>30000psi and >410°F).Potential high-density weighting materials were evaluated.Properties (pure density,particle size/distribution,surface area etc.)were evaluated and compared.Special treatment was conducted to optimizeproperties of weighting materials.HPHT filtration tests under static and dynamic conditions were conductedat higher than 410°F and 300 psi.Real cores with an average porosity of 19% and an average permeabilityof 50 md were used in the filtration tests.Rheological properties,sag tendency,the volume of filtrate,andthe filtrate cake characterization was measured before and after heating at 410°F for 16 hours.Results revealed that ultra-micro manganese and ilmenite complex after suitable surface treatment couldact as an ideal weighting material than ultra-pure barite or other materials,which could fail in rheology andsag measurement with such high temperature and density.Viscosity and filtration analysis confirmed thestability and reliability of this novel ultra-high density oil-based drilling fluid.This study developed a challenged drilling fluid system under critical conditions,as well as establisheda systematical laboratory evaluation and screening procedure of weighting materials and contributedrecommendations on how to utilize it in the fields.
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