Functionalized Nanosilicas as Shale Inhibitors in Water-Based Drilling Fluids

Water-based-mud (WBM) formulations inclusive of nanosilicas offer the possibility for improved shale inhibition with reduced environmental impact vs. conventional shale inhibitors. These additives may be effective in maintaining well stability and in preventing equipment problems, such as bit balling, which may be experienced in the absence of good shale inhibition. A series of different nanosilicas has been tested as shale inhibitors in WBMs. Differences in shale inhibition are observed depending on the kind of nanosilica that is used. The nanosilicas described in this article are tested in fresh water and seawater to determine their applicability in both onshore and offshore scenarios. In seawater, nanosilica muds appear to be more powerful inhibitors than silicate/potassium chloride (KCl) muds. The data presented in this report indicate that a nanosilica mud achieves less shale erosion in seawater than a conventional silicate/KCl mud. This increased performance of nanosilica is accompanied with greater ease in handling the lower-pH fluid (which can range from pH 8.5 to 10.0) compared with silicate muds that often exceed pH 12. In addition to being more-potent inhibitors and more safe to handle, nanosilicas offer the possibility of lower environmental cost. High concentrations of KCl are not necessarily required when nanosilicas are included in a mud design for shale inhibition.