Abstract

Global energy demand has driven petroleum industry to develop hydrocarbon resources from extremely harsh formations. Ultra-high density drilling fluids are critical to successful drilling and completion practices in all of these wells. In this paper, potential weighting materials were systematically evaluated and screened to accomplish an ultra-high density oil-based drilling fluid system (19.62 to 22.12lb/gal) aimed to utilize in 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 optimize properties of weighting materials. HPHT filtration tests under static and dynamic conditions were conducted at higher than 410°F and 300 psi. Real cores with an average porosity of 19% and an average permeability of 50 md were used in the filtration tests. Rheological properties, sag tendency, the volume of filtrate, and the 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 could act as an ideal weighting material than ultra-pure barite or other materials, which could fail in rheology and sag measurement with such high temperature and density. Viscosity and filtration analysis confirmed the stability 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 established a systematical laboratory evaluation and screening procedure of weighting materials and contributed recommendations on how to utilize it in the fields.

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