Application of Ultra Fine Ilmenite Powder as Drilling Fluid Weighting Agent

Deep water well, extended reach well, HTHP well and well with narrow safe drilling window are imposing higher and more rigorous requirements on the performance of drilling fluids, especially those requirements such as the rheology, wall building property, settling stability and reservoir protection ability of high density and ultra-high density drilling fluids, which cannot be gained from conventional API barite. New weighting agents have to be found to satisfy the increasing needs of drilling wells with special challenges. Ultra-fine barite, fine manganese minerals and ultra-fine ilmenite are in recent years finding wider application in drilling fluids and have gained good reputation in field application. Relative literatures from both China and abroad have been studied to understand the characteristics of the ultra-fine ilmenite, the effects of ultra-fine ilmenite on the rheology, filtration property and settling stability of water base drilling fluid and oil base drilling fluid, as well as the use of ultra-fine ilmenite in high density and ultra-high density water base and oil base drilling fluids. It is concluded that the rheology of the water base and oil base drilling fluids is improved if ultra-fine ilmenite is used alone or with API barite as the weighting agent. Ultra-fine ilmenite has good acid solubility, and mud cakes of drilling fluids treated with ultra-fine ilmenite are much easier to remove. Ultra-fine ilmenite has better settling stability and poses low damage to reservoir rock permeability. By removing the hematite from ultra-fine ilmenite, the magnetism of ultra-fine ilmenite can be minimized. Although the hardness of ultra-fine ilmenite is higher than that of barite, the D₉₀ of ilmenite is approximately 15 μm, meaning that ultra-fine ilmenite has abradability that is lower than that of API barite. Since ultra-fine ilmenite has narrow particle size distribution (D₅₀≈5 μm), in drilling fluids of the same density, drilling fluid weighted with ultra-fine ilmenite has higher HTHP filtration rate. This can be resolved by adding acid soluble bridging particles with wide particle size distribution. Ultra-fine ilmenite as a whole is a prospective new drilling fluid weighting agent. Ultra-fine ilmenite has been used as weighting agent with great success in Arab Gulf and United Arab Emirates.