Using Nanoparticles to Formulate Sag-Resistant Invert Emulsion Drilling Fluids

Abstract

Abstract Invert-emulsion fluid (IEF) systems formulated without organophilic clay have successfully addressed issues of barite sag while drilling wellbores. In the absence of organoclay, the “organoclay-free” IEFs have to use additional materials like sized calcium carbonate or clay-type materials to bolster the rheological properties and suspension character of the system. In the absence of low-gravity solids (LGS), the loss of suspension, especially in an inclined well, can lead to sag and cause a density gradient along the fluid column that may fracture the formation. This paper presents a solution toward barite sag in an invert emulsion drilling fluid with the use of novel nanoparticles. The use of nanoparticles was shown to prevent sag in 9 ppg, 12 ppg, and 16 ppg organoclay-free IEF in a static-aging cell held vertical at 90° and then inclined at 45°. Fluids formulated with nanoparticles showed good sag control in different base oils with minimal oil separation. Extended sag testing with the sag-control additive at 250°F for 24 hours and at 150°F for 60 hours gave minimal oil separation and no barite sag. The nanoparticles based IEF was also subjected to contamination testing. Barite sag measurements performed on “contaminated” nanoparticle-based IEF shows that the suspension characteristics remain unaffected and the mud properties are tolerant to the presence of contaminants. Experimental data demonstrating the anti-sag performance of the nanoparticles in IEF is presented and compared to fluids without the nanoparticles.