Evaluation of Formation Damage of Oil-Based Drilling Fluids Weighted with Micronized Ilmenite or Micronized Barite

Solids found in drilling fluids, particularly weighting materials, can cause significant formation damage by plugging of formation pores. This study investigates formation damage caused by using oil-based drilling fluid systems weighted by micronized ilmenite or micronized barite. Rheological properties of the oil-based-mud (OBM) systems were measured. High-pressure/high-temperature (HP/HT) static filtration experiments were conducted. A coreflood system was used to simulate dynamic conditions, allowing for drilling fluid circulation at the face of the core and measuring permeability damage. Computed-tomography (CT) scan analysis revealed formation damage and depth of solid invasion. The paper presents field applications of nondamaging micronized-ilmenite-based OBM, illustrating its advantages.