Improvement of Anti-Sag and Rheological Properties of Water Based Muds Using Nano-Barite

Abstract

Barite Sag is an adverse phenomenon observed in horizontal drilling or Extended Reach Drilling (ERD) operations. It has been reported to occur majorly due to settling of weighing material such as barite on the lower side of directional wells. The barite sagging has been reported to cause drilling operational problems such as induced well-bore instability, mud losses and pipe stuck up leading to well control problems. In this context, an attempt has been made to address the barite sagging problem through application of laboratory synthesized nano-particles of barite as they are known to posses’ high area to volume ratio, hence required in low quantities in formulating optimum gravity drilling fluid. However, low quantities of barite nano-particles aids in lowering Plastic-Viscosity (PV) and increasing Rate Of Penetration (ROP) due to low solids concentration associated with it. Further, the larger surface area of barite nano-particles also aids in improved heat dissipation from bottom hole, thereby increasing the life of bits. The sagging test results have projected a reduction in sagging phenomenon with the application of nano-barite particles. However, the rheology analysis results have projected a decrease in PV with unchanging filtration-loss properties meeting the API standards. Further, the rheological behaviour at various temperatures better fits with Herschel-Bulkley model establishing its shear thinning characteristics. The present work aids in formulating efficient drilling fluids for economical directional drilling operations